Polyphosphate attachment to lysine repeats is a non-covalent protein modification

Polyphosphate (polyP) is a chain of inorganic phosphate that is present in all domains of life and affects diverse cellular phenomena, ranging from blood clotting to cancer. A study by Azevedo et al. described a protein modification whereby polyP is attached to lysine residues within polyacidic serine and lysine (PASK) motifs via what the authors claimed to be covalent phosphoramidate bonding. This was based largely on the remarkable ability of the modification to survive extreme denaturing conditions. Our study demonstrates that lysine polyphosphorylation is non-covalent, based on its sensitivity to ionic strength and lysine protonation and absence of phosphoramidate bond formation, as analyzed via 31P NMR. Ionic interaction with lysine residues alone is sufficient for polyP modification, and we present a new list of non-PASK lysine repeat proteins that undergo polyP modification. This work clarifies the biochemistry of polyP-lysine modification, with important implications for both studying and modulating this phenomenon. This Matters Arising paper is in response to Azevedo et al. (2015), published in Molecular Cell. See also the Matters Arising Response by Azevedo et al. (2024), published in this issue.

Modulating the properties and structure of lignins produced by alkaline delignification of sugarcane bagasse pretreated with two different mineral acids at pilot-scale

Sugarcane bagasse was pretreated with dilute phosphoric acid or sulfuric acid to facilitate cellulose hydrolysis and lignin extraction. With phosphoric acid, only 8 % of the initial cellulose was lost after delignification, whereas pretreatment with sulfuric acid resulted in the solubilization of 38 % of the initial cellulose. After enzymatic hydrolysis, the process using phosphoric acid produced approximately 35 % more glucose than that using sulfuric acid. In general, the lignins showed 95-97 % purity (total lignin, w/w), an average molar mass of 9500-10,200 g mol-1, a glass transition temperature of 140-160 °C, and a calorific value of 25 MJ kg-1. Phosphoric acid lignin (PAL) was slightly more polar than sulfuric acid lignin (SAL). PAL had 13 % more oxidized units and 20 % more OH groups than SAL. Regardless of the acid used, the lignins shared similar properties, but differed slightly in the characteristics of their functional groups and chemical bonds. These findings show that pretreatment catalyzed with either of the two acids resulted in lignin with sufficiently good characteristics for use in industrial processes.

Optimizing Typha biochar with phosphoric acid modification and ferric chloride impregnation for hexavalent chromium remediation in water and soil

Considering the persistent and covert nature of heavy metal soil contamination, the sustainable development of ecological environments and food safety is at significant risk. Our study focuses on remediating soils contaminated with chromium (Cr); we introduce an advanced remediation material, iron oxide phosphoric acid-loaded activated biochar (HFBC), synthesized through pyrolysis. This HFBC displays greater microporosity, fewer impurities, and enhanced efficiency for the remediation process. Our research utilized a comprehensive set of analytical techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS), alongside adsorption studies to elucidate the Cr removal mechanism. The effectiveness of HFBC in remediation was influenced by several factors: the pH level, dosage of HFBC, the initial concentration of Cr, and the ambient temperature. Our results indicated an optimal chromium (VI) adsorption capacity of 55.5 mg/g by HFBC at a pH of 6.0 and a temperature of 25 °C, with the process adhering to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm, thus suggesting spontaneity in the uptake method. Moreover, this mechanism encompasses both adsorption and reduction reactions. Using HFBC in pot experiments with cabbage indicated not only an increase in soil pH and cation exchange capacity (CEC), but also a surge in bacterial community abundance. Significant reductions in bioavailable chromium were also recorded. Interestingly, HFBC addition bolstered the growth of cabbage, while concurrently diminishing chromium accumulation within the plant, particularly notable as the HFBC application rate increased. In summation, the HFBC produced in our study has demonstrated convincing efficacy in removing chromium from aqueous solutions and soil. Moreover, the positive agronomic implications of its use, such as enhanced plant growth and reduced heavy metal uptake by plants, indicate its high potential for operational value in the domain of environmental remediation of heavy metals.

Dietary contribution of iron from limestone and dicalcium phosphate for broiler chickens

Iron is routinely supplemented in broiler feeds aiming to prevent dietary deficiencies. Limestone and phosphates are very rich in Fe; however, its contribution from these sources have not been thoroughly investigated with chickens. The present research was conducted to evaluate live performance and blood parameters of broilers when using limestone and dicalcium phosphate as sources of Fe. A total of 576 one-day-old male Cobb x Cobb 500 were allocated into a total of 72 battery cages, 6 treatments with 12 replication cages of 8 chicks at placement. Chicks were fed diets formulated with corn, soybean meal (SBM) with laboratory grade calcium carbonate and phosphoric acid (having traces of Fe). All chicks were fed a common prestarter without Fe supplementation (analyzed total 58.2 ± 2.4 mg/kg Fe) from placement to 7 d. Allocation of birds to dietary treatments was completely randomized on day 8. Treatments had increasing Fe derived from commercial limestone and dicalcium phosphate (analyzed Fe 7,218 and 4,783 mg/kg, respectively) progressively replacing calcium carbonate and phosphoric acid to provide graded increases in total Fe (analyzed Fe in the feeds were 57.6 ± 2.1, 92.0 ± 2.3, 124.1 ± 2.7, 159.3 ± 3.1, 187.2 ± 3.2, 223.7 ± 3.6 mg/kg, respectively). There were no effects of dietary Fe on live performance, hematocrit, and hemoglobin the end of the study on day 28 (P > 0.05). Increasing dietary Fe from commercial limestone and dicalcium phosphate led to a linear reduction in the percent ileal digestible Fe. However, linear increments in Fe retention, serum ferritin and liver Fe occurred when compared to feeds without Fe derived from limestone and phosphate dicalcium. It is concluded that Fe from limestone and dicalcium phosphate can be partially utilized by broiler chickens. It was estimated that the Fe retained from limestone and dicalcium phosphate is of 1.9%. Broilers fed corn-soy feeds (58.2 mg/kg Fe) do not require supplemental Fe.

Preparation and structural characterization of epoxidized soybean oils-based pressure sensitive adhesive grafted with tea polyphenol palmitate

Vegetable oils-based pressure sensitive adhesives (PSAs) are green and sustainable but face unsatisfactory adhesion strengths and are prone to aging during storage and application due to the existence of residual double bonds and massive ester bonds. Nine common antioxidants (tea polyphenol palmitate (TPP), caffeic acid, ferulic acid, gallic acid, butylated hydroxytoluene, tertiary butylhydroquinone, butylated hydroxyanisole, propyl gallate, and tea polyphenols) were grafted into epoxidized soybean oils-PSA (ESO-PSA) system to enhance antiaging properties and adhesion strengths. Results showed ESO-PSAs grafted with caffeic acid, tertiary butylhydroquinone, butylated hydroxyanisole, propyl gallate, tea polyphenols, or TPP didn't occur failure with TPP having best performance. The optimal conditions were ESO reacted with 0.9 % TPP, 70 % rosin ester, and 7.0 % phosphoric acid at 50 °C for 5 min, under which peel strength and loop tack increased to 2.460 N/cm and 1.66 N, respectively, but peel strength residue reduced to 138.09 %, compared with control (0.407 N/cm, 0.43 N, and 1669.99 %). Differential scanning calorimetry and thermogravimetric results showed TPP grafting increased the glass transition temperature of ESO-PSA slightly but improved its thermal stability significantly. Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance results showed TPP, phosphoric acid, and rosin ester all partially participated in the covalently crosslinking polymerization of ESO-PSAs and the rest existed in the network structures in the free form.

Longitudinal bond strength of a universal adhesive and chemical dentin characterization under different acid etching protocols

OBJECTIVE

This study aimed to analyze the longitudinal bond strength of a universal adhesive and chemically characterize the dentin substrate under different acid etching protocols.

METHODOLOGY

Dentin samples were etched with polyacrylic acid 25% (PAA) for 10 seconds (n=3) and phosphoric acid 32% (PA) for 15 seconds (n=3) and analyzed by Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR) before and after treatment. For collagen degradation, samples (n=12) were divided into 3 groups: PAA, PA, and Deionized water (control), and analyzed by the quantity of solubilized type I collagen C-terminal cross-linked telopeptides and solubilized C-terminal peptide in relation to total protein concentration (ICTPtp and CTXtp) and by their ultimate tensile strength (UTS). For the adhesive interface analysis, dentin samples (n=72) were divided into 3 groups: PAA, PA, and Self-etch (SE), and subdivided into 2 groups: 24 h (baseline) and 1 year. The following tests were performed: microtensile bond strength (μTBS) (n=48), scanning electron microscopy (SEM) (n=12), and nanoleakage (n=12).

RESULTS

The FTIR of PAA showed lower reduction of the peaks in the phosphate group when compared to PA. For ICTPtp, PA showed a significantly higher value. For CTXtp, PA and PAA groups failed to statically differ from each other. UTS was significantly lower for PA. For μTBS, storage time significantly affected bond strength. The results were unaffected by the etching protocol. For SEM, after 1 year, PA had little evidence of degradation in the upper third of the adhesive interface in comparison to the other groups. Nanoleakage showed no considerable silver impregnation after 1 year in the SE group.

CONCLUSION

The use of PAA prior to a universal adhesive (when compared to PA) represents a less aggressive type of etching to dentin. However, self-etching still seems to be the best option for universal adhesive systems that have functional monomers in their composition.

Protocol for producing phosphoramidate using phosphorus fluoride exchange click chemistry

Phosphorus fluoride exchange (PFEx) is a catalytic click reaction that involves exchanging high oxidation state P-F bonds with alcohol and amine nucleophiles, reliably yielding P-O- and P-N-linked compounds. Here, we describe steps for preparing a phosphoramidic difluoride and performing two sequential PFEx reactions to yield a phosphoramidate through careful catalyst selection. We then detail procedures for handling and quenching potentially toxic P-F-containing compounds to ensure user safety when conducting PFEx reactions. For complete details on the use and execution of this protocol, please refer to Sun et al.1.

Analytical quality by design approach for the development of high-performance liquid chromatography method for simultaneous analysis of metformin and sitagliptin in the presence of major degradation products

An analytical quality by design-based high-performance liquid chromatography method for determining metformin (MET) and sitagliptin (SIT) in stress-degraded samples was developed and validated. The analytical target profile and risk assessment-driven critical method variables, for example, pH, % aqueous, and buffer concentration, were studied for their effect on method responses of retention time and resolution using a central composite design. The correlation regression coefficient was more than 0.8, and variables interaction was significant on method responses with curvature effect. The method operable design region afforded an aqueous range of 55%-70% and an ortho-phosphoric acid buffer of 0.1% with a pH of 3.0-4.0 as a robust region for the suitable method performance characteristics. The separation of MET and SIT from their degradants (m/z 85.0509; m/z 193.0694) on the C8 column was achieved using a mobile phase consisting of 0.1% ortho-phosphoric acid and methanol (60:40% v/v; pH 3.0). The optimized method eluted MET and SIT at 4.3 ± 0.2 and 7.1 ± 0.2 min, respectively, with acceptable specificity and resolution. The linearity ranges of 25-250 μg/mL (r2 : 0.9982) and 5-50 μg/mL (r2 : 0.9989) was established for MET and SIT, respectively. The % recovery (98.81%-102.17%), precision (0.55%-1.65%), and robustness study for method variables were acceptable.

Impact of try-in paste removal on the fatigue behavior of bonded lithium disilicate ceramics

This in vitro study assessed the effectiveness of three cleaning protocols (air-water spray, 37% phosphoric acid, or Ivoclean) on lithium disilicate restorations' fatigue behavior after try-in paste application, compared to a clean condition. Lithium disilicate discs (IPS e.max CAD, Ivoclar) with Ø-= 12 mm and 1 mm thickness were prepared from prefabricated CAD-CAM blocks, polished, subjected to CAD-CAM milling topography simulation and crystallization. After, etching with 5% hydrofluoric acid and the application of try-in paste (Variolink try-in paste shade white; load of 2.5 N for 5 min) was performed. Discs that received try-in paste were divided into three groups according to the removal protocol: SPRAY - air-water spray for 30 s; HPO - active application of 37% phosphoric acid for 60 s; IVOC - application of Ivoclean for 20 s. Control group (CTRL group) did not receive the try-in paste application. Half of the specimens (n= 15) were tested in the baseline condition (24 h up to 7 days), and the others underwent 25,000 thermal cycles (5 - 55 °C) + 210 days of distilled water storage (37 °C). Additional specimens (n= 3) underwent monotonic testing (1 mm/min). Fatigue testing involved a cyclic fatigue approach (20 Hz, initial load = 100 N - 5000 cycles, step size = 50 N - 10,000 cycles) until a visible crack appeared. Fractographic and topographic analyses were performed. Fatigue data were statistically analyzed with two-way ANOVA, Kaplan-Meier log-rank (Mantel-Cox), and independent t-test (α= 0.05). In the baseline condition, the IVOC group resulted in a superior fatigue behavior compared to the CTRL and SPRAY groups, but similar to the HPO group. The HPO and SPRAY presented a similar fatigue behavior to the CTRL group. It was noticed a decrease in fatigue behavior after aging, which resulted in all the cleaning protocols leading to similar fatigue behavior compared to the CTRL group. On the SPRAY group surface, try-in pastes remnants were noticed. In summary, despite a detrimental impact at baseline conditions, all tested cleaning protocols seem proper to remove the try-in paste from the ceramic's surface in the long-term evaluation.

Utilization of phosphoric acid-modified biochar to reduce vanadium leaching potential and bioavailability in soil

Remediating vanadium (V) polluted soil has garnered widespread attention over the past decade. Yet, few research projects have investigated the stabilization of soil V using modified biochar, so the effects and interacting mechanisms between soil properties and modified biochar for V immobilization and stabilization remain unclear. Hence, this gap is addressed by determining the leaching behavior and mechanisms of soil V on different dosages of phosphoric acid (H3PO4) impregnated biochar (MLBC, 0.5%-4%). The applicability and durability in soil V immobilization was investigated under acid precipitation. The MLBC effect on V bioavailability and mobility was assessed first by CaCl2, Toxicity Characteristic Leaching Procedure (TCLP) and Synthetic Precipitation Leaching Procedure (SPLP) extractions in different periods. The V concentrations significantly reduced in CaCl2, TCLP, and SPLP extract with MLBC at each dosage (30 d), while slight to significant increase in SPLP and TCLP extract V was recorded in a long-term incubation (90 d). Column leaching test further demonstrated the high durability of 4% MLBC in V stabilization under continuous acid exposure. Compared to the control (no-biochar), the accumulated V content in the leaching solution significantly decreased in MLBC-amended soil. Acid soluble fraction of V showed significant negative correlation with both soil organic matter (SOM) and available P, which was positively correlated with pH, suggested that pH, available P and SOM were key factors affecting the bioavailability of V in soil. Moreover, combining with the characterization results of MLBC and amended soil, the results revealed that H3PO4 modified biochar played a vital role on V immobilization and soil improvement by forming electrostatic adsorption, ion exchange, redox reaction or complexation with the increase of functional groups. These revealed an efficient and steady development of soil quality and treatment for soil V contamination, under MLBC operation to soil polluted with exogenous V.

Influence of etchant type on the shear bond strength of orthodontic brackets to enamel

The aim of this study was to evaluate the influence of the type of etchant on the shear bond strength (SBS) of metallic brackets to enamel and the Adhesive Remnant Index (ARI) after debonding. A total of 30 mandibular and maxillary premolars were randomly distributed into groups (n = 10) treated with 1 of 3 enamel surface-conditioning agents: 35% phosphoric acid (PA), 35% glycolic acid (GA), or 35% ferulic acid (FA). The designated acid was applied to the buccal enamel surface of the tooth for 20 seconds, and the tooth was then rinsed with distilled water for 20 seconds and air dried for 5 seconds. A metal bracket was bonded to the prepared surface with light-cured orthodontic resin. After 24 hours, the bracket-tooth interface was submitted to SBS testing in a universal testing machine at a speed of 0.5 mm/min. After debonding, the enamel surface was observed under a stereomicroscope (×20 magnification) to determine the ARI. The generalized linear models showed that the PA and GA groups presented significantly higher SBSs than the FA group (P = 0.0003). The ARI was significantly higher in specimens treated with PA than with the other acids (P < 0.05; Kruskal-Wallis and Dunn tests), with a larger quantity of adhesive remaining adhered to the tooth. Both PA and GA are effective for bonding brackets, but GA resulted in a lower percentage of adhesive remnant adhered to the enamel.

Formaldehyde-free and durable phosphorus-containing cotton flame retardant with -N=P-(N)3- and reactive ammonium phosphoric acid groups

A flame retardant (FR) hexachlorocyclotriphosphazene diethylenetriamine ammonium phosphoric acid (HDAPA) was synthesized. Vertical flammability test and limiting oxygen index (LOI) results showed that cotton samples finished with HDAPA solutions (15 % and 20 %) could pass vertical flame retardancy test, and LOIs reached 30.1 % and 35.4 % even after 50 laundering cycles according to AATCC 61-2013 3A washing standard (3A), performing flame retardancy and washing durability. Meanwhile, Fourier transform infrared and X-ray photoelectron spectroscopy analyses suggested that HDAPA was grafted on cotton fibers through -P(=O)-O-C covalent bond. Total heat release (1.98 MJ/m2) and char residue (16.2 %) of HDAPA treated cotton were much lower than those (4.26 MJ/m2, 3.2 %) of untreated cotton. Thermogravimetry results showed HDAPA changed thermal decomposition pathway of cotton fabric, which was further supported by thermogravimetric-Fourier infrared spectrometer results, revealing HDAPA performed a condensed phase flame retardancy mechanism. Scanning electron microscopy implied HDAPA entered amorphous region of cotton fibers to react with cellulose. Mechanical properties of HDAPA treated cotton decreased a little. Although the synthesis process used formaldehyde but no free formaldehyde released. In consequence, the aforementioned results indicated that the introduction of -N=P-(N)3- and -P(=O)(O-NH4+)2 groups to FR was an viable method to improve flame retardancy and durability.

Synthesis and evaluation of aromatic stationary phases based on linear solvation energy relationship model for expanded application in supercritical fluid chromatography

In the last decade, the separation application based on aromatic stationary phases has been demonstrated in supercritical fluid chromatography (SFC). In this paper, four aromatic stationary phases involving aniline (S-aniline), 1-aminonaphthalene (S-1-ami-naph), 1-aminoanthracene (S-1-ami-anth) and 1-aminopyrene (S-1-ami-py) were synthesized based on full porous particles (FPP) silica, which were not end-capped for providing extra electrostatic interaction. Retention mechanism of these phases in SFC was investigated using a linear solvation energy relationship (LSER) model. The aromatic stationary phases with five positive parameters (a, b, s, e and d+) can provide hydrogen bonding, π-π, dipole-dipole and cation exchange interactions, which belong to the moderate polar phases. The LSER results obtained using routine test solutes demonstrated that the aforementioned interactions of four aromatic stationary phases were influenced by the type and bonding density of the ligand, but to a certain extent. Furthermore, the LSER data verified that the S-1-ami-anth column based on full porous particles silica had higher cation exchange capacity (d+ value), compared to the commercialized 1-AA column (based on the ethylene-bridged hybrid particles). The relationship between the d+ value and SFC additive was quantitatively proved so as to regulate electrostatic interaction reasonably. This value was greatly increased by phosphoric acid, slightly increased by trifluoroacetic acid and formic acid, but significantly reduced by ammonium formate and diethylamine. Taking the S-1-ami-naph column as an example, better peek shape of the flavonoids was obtained after the addition of 0.1 % phosphoric acid in MeOH while isoquinoline alkaloids were eluted successfully within 11 min after adding 0.1 % diethylamine in MeOH. Combined with the unique π-π interaction and controllable electrostatic interaction, the aromatic stationary phases in this study have been proven to have expandable application potential in SFC separation.

Thermophysical properties and bonding with composite resin of premixed mineral trioxide aggregate for use as base material

Dental bases require low thermal conductivity and good mechanical properties, such as bonding with composite resins. This study aims to elucidate the physicochemical properties of premixed mineral trioxide aggregate (MTA) for its suitability as a dental base and to explore the optimal adhesive strategy with composite resin. The thermal conductivity and compressive strength of this premixed MTA are 0.12 W/(m•K) and 93.76 MPa, respectively, Which are deemed adequate for its application as dental base. When bonded to composite resin, the use of 37% phosphoric acid etching before applying the Clearfil SE bond significantly reduced the bonding strength between composite resin and premixed MTA. This was because the compressive strength and Vickers hardness of premixed MTA decreased, and tricalcium silicate was dissolved from the surface during acid etching. Therefore, it is recommended to avoid using 37% phosphoric acid etching when bonding premixed MTA and composite resin as a dental base.

75 Years Ago: Discovery of Resin Adhesion to Acid-etched Enamel - A Comparison of the 1949 and 1955 Methods

PURPOSE

This paper describes previously unknown details about the discovery of resin adhesion to acid-etched human enamel.

MATERIALS AND METHODS

A literature review was performed through manual assessments. Primary sources revealing the discovery of resin curing on etched enamel were analyzed considering the research objectives and methodological procedure during that era, including the type of teeth used, preparatory measures, acid-etching process, type of resin and its application, and follow-up observations. Additionally, the political and economic contexts were examined.

RESULTS

In 1949, acid etching was found to promote adhesion with acrylic resin, a finding described again in 1955. The 1949 studies utilized nitric acid for enamel etching and the acrylate resin Paladon from the Kulzer company (Germany). Conversely, the 1955 investigations employed phosphoric acid and an unnamed acrylate, likely a self-curing resin supported by Kulzer in the late 1930s. Disparities in the 1949 and 1955 findings can be ascribed to varying objectives and test conditions amidst a turbulent political backdrop, significantly impacting the Kulzer company.

CONCLUSION

The discovery of resin adhesion to acid-etched enamel, approaching its 75th anniversary in 2024, is a landmark in 20th-century adhesive dentistry. Paladon represents a pioneering compound, exemplifying the influence of political, ideological, and economic factors on scientific advancements during that period.

Phosphoramidate Azole Oligonucleotides for Single Nucleotide Polymorphism Detection by PCR

Detection of the Kirsten rat sarcoma gene (KRAS) mutational status is an important factor for the treatment of various malignancies. The most common KRAS-activating mutations are caused by single-nucleotide mutations, which are usually determined by using PCR, using allele-specific DNA primers. Oligonucleotide primers with uncharged or partially charged internucleotide phosphate modification have proved their ability to increase the sensitivity and specificity of various single nucleotide mutation detection. To enhance the specificity of single nucleotide mutation detection, the novel oligonucleotides with four types of uncharged and partially charged internucleotide phosphates modification, phosphoramide benzoazole (PABA) oligonucleotides (PABAO), was used to prove the concept on the KRAS mutation model. The molecular effects of different types of site-specific PABA modification in a primer or a template on a synthesis of full-length elongation product and PCR efficiency were evaluated. The allele-specific PCR (AS-PCR) on plasmid templates showed a significant increase in analysis specificity without changes in Cq values compared with unmodified primer. PABA modification is a universal mismatch-like disturbance, which can be used for single nucleotide polymorphism discrimination for various applications. The molecular insights of the PABA site-specific modification in a primer and a template affect PCR, structural features of four types of PABAO in connection with AS-PCR results, and improvements of AS-PCR specificity support the further design of novel PCR platforms for various biological targets testing.

Effective adsorption of bisphenol A from aqueous solution using phosphoric acid-assisted hydrochar

Sycamore leaf biochar (PSAC) was prepared by a two-step phosphoric acid-assisted hydrothermal carbonization combined with a short-time activation method. The characterization results showed that the introduction of phosphoric acid molecules and thermal activation resulted in a substantial increase in the specific surface area (994.21 m2/g) and microporous capacity (0.307 cm3/g) of PSAC. The batch adsorption results showed that the adsorption process of PSAC on bisphenol A (BPA) was best described by the pseudo-second-order kinetic model and Sips isothermal model, with a maximum adsorption capacity of 247.42 mg/g. The adsorption of BPA onto PSAC was determined to be a spontaneous endothermic process. The equilibrium adsorption capacity of PSAC exhibited an upward trend with increasing initial BPA concentration and temperature while decreasing with higher adsorbent dosage and pH value. Coexisting cations and humic acids in water have little impact on the adsorption performance of PSAC for BPA. The adsorption mechanism of BPA by PSAC was mainly governed by pore filling and hydrogen bonding interactions, π-π interactions, and intraparticle diffusion. Furthermore, PSAC demonstrated good reusability by its sustained adsorption capacity of BPA, which remained at 82.6% of the initial adsorption capacity even after four adsorption-desorption cycles. These findings highlight the potential of utilizing low-cost sycamore leaf biochar as an effective adsorbent for the removal of the endocrine disruptor BPA.

Scanning electron microscope analysis to evaluate the effect of pretreatment with ozone and sodium hypochlorite on pits and fissures of primary teeth

Introduction

The cornerstone of preventative therapy is made up of pit and fissure sealants and fluorides. Resin sealants have been shown to help reduce fissure decay in both primary and permanent teeth. Etching of primary molars is not effective due to prismless enamel, higher organic content, and diversity in fissure shape. Methods of pretreatment of pits and fissures have been hypothesized to promote microporosities in etched enamel and hence sealant adherence. Examining the etching pattern and surface roughness of the enamel surface can be used to gauge these.

Objective

This study aimed to evaluate the effect of pretreatment with ozone gas and 5.25% sodium hypochlorite solution on pits and fissures of primary teeth to check for the etching pattern and surface roughness.

Materials and Methods

Thirty noncarious primary molars were sectioned to retain the crowns, and randomly divided into three groups, sodium hypochlorite, ozone gas, and control. Each sample was pretreated with the agent, washed, followed by etching with 37% phosphoric acid. Samples were sectioned and subjected to scanning electron microscope analysis to evaluate the etching pattern and surface roughness.

Results

Comparison of the etching pattern in three groups showed a statistically insignificant difference (P=0.364). Surface roughness was highest in the hypochlorite group followed by ozone and control which showed a statistically significant difference (P = 0.001). The surface area between the three groups showed a statistically insignificant difference.

Conclusion

Sodium hypochlorite is a better pretreatment agent compared to ozone gas and acid etching alone. However, as all results were not statistically significant further research must be carried out to prove the effectiveness of these agents.

Environmental-friendly and effectively regenerate anode material of spent lithium-ion batteries into high-performance P-doped graphite

Recycling graphitefrom spentlithium-ionbatteries has been largely ignored.In the present work, we propose a novel purification process, which modifies the structure of graphite through phosphoric acid leaching-calcination to obtain high-performance phosphorus (P)-doped graphite (LG-temperature) and lithium phosphate products. The content analysis of X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF) and scanning electron microscope focused ion beam (SEM-FIB) indicates that the LG structure is deformed by the doped P atom. The results of In-situ fourier transform infrared spectroscopy (In-situ-FTIR), density functional theory (DFT) calculation and XPS analysis show that the surface of the leached spent graphite contains rich oxygen groups, which react with phosphoric acid at high temperatures and form stable C-O-P and C-P bonds, making it easier to form stable solid electrolyte interface (SEI) layer. The increase of layer spacing is confirmed by X-ray diffraction (XRD), Raman and transmission electron microscope (TEM), which is conducive to the formation of efficient Li⁺ transport channels. What is more, Li/LG-800 cells possess high reversible specific capacities of 359, 345, 330 and 289 mA h g^-1 at 0.2C, 0.5C, 1C and 2C, respectively. After100cyclesat0.5C, the specific capacityis as high as 366 mAh g^-1, demonstrating the outstanding reversibility and cycle performance. This study proves and highlights a promising recovery route for exhausted lithium-ion batteries anodes, making complete recycling possible.

Removal of Al3+ and Mg2+ ions in wet-process phosphoric acid via the formation of aluminofluoride complexes

With the decrease in the phosphate rock grade, the minor element ratios (MER) [(Fe₂O₃ wt% + Al₂O₃ wt% + MgO wt%)/P₂O₅ wt%] of wet-process phosphoric acid (WPA) exhibits a linear upward trend. This can lead to a huge challenge for the high-quality production of feed calcium phosphate salt (FCPS). In the present study, we proposed a novel and economical strategy to precipitate Al³⁺ and Mg²⁺ via the formation of aluminofluoride complexes (NaMgAlF₆·H₂O) with the anhydrous sodium sulfate (Na₂SO₄) and hydrofluoric acid (HF) as precipitation agents. Because of the low solubility of the complexes in WPA, the removal efficiencies of Al³⁺ and Mg²⁺ ions could reach 99.5% and 64.8%, respectively. The maximum mass loss of P₂O₅ was less than 0.5%. The precipitates could be separated and converted into the HF and Na₂SO₄ for reuse, thus further decreasing the cost of WPA purification.

Enamel and Dentin Etching with Glycolic, Ferulic, and Phosphoric Acids: Demineralization Pattern, Surface Microhardness, and Bond Strength Stability

This study evaluated the etching pattern, surface microhardness, and bond strength for enamel and dentin submitted to treatment with phosphoric, glycolic, and ferulic acids. Enamel and dentin blocks were treated with phosphoric, glycolic, and ferulic acid to evaluate the surface and adhesive interface by scanning electron microscopy (2000×). Surface microhardness (Knoop) was evaluated before and after etching, and microtensile bond strength was evaluated after application of a two-step adhesive system (Adper Single Bond 2, 3M ESPE) at 24 hours and 12 months storage time points. Analysis of variance (ANOVA) and Tukey's test showed a decrease in the microhardness values for both substrates after application of each acid (p<0.0001). The reduction percentage was significantly higher for enamel treated with phosphoric acid (59.9%) and glycolic acid (65.1%) than for ferulic acid (16.5%) (p<0.0001), and higher for dentin that received phosphoric acid (38.3%) versus glycolic acid (27.8%) and ferulic acid (21.9%) (p<0.0001). Phosphoric and glycolic acids led to homogeneous enamel demineralization, and promoted the opening of dentinal tubules, whereas ferulic acid led to enamel surface demineralization and partially removed the smear layer. The adhesive-enamel interface showed micromechanical embedding of the adhesive in the interprismatic spaces when phosphoric and glycolic acids were applied. Ferulic acid showed no tag formation. Microtensile bond strength at both time points, and for both substrates, was lower with ferulic acid (p=0.0003/E; p=0.0011/D; Kruskal Wallis and Dunn). The bond strength for enamel and dentin decreased when using phosphoric and glycolic acids at the 12-month time evaluation (p<0.05). Glycolic acid showed an etching pattern and microhardness similar to that of phosphoric acid. Ferulic acid was not effective in etching the enamel or dentin, and it did not provide satisfactory bond strength to dental substrates.

Treatment of distiller grain with wet-process phosphoric acid leads to biochar for the sustained release of nutrients and adsorption of Cr(VI)

Soil amendment products, such as biochar, with both sustained nutrient release and heavy metal retention properties are of great need in agricultural and environmental industries. Herein, we successfully prepared a new biochar material with multinutrient sustained-release characteristics and chromium removal potential derived from distiller grain by wet-process phosphoric acid (WPPA) modification without washing. SEM, TEM TG-IR, in situ DRIFTS and XRD characterization indicated that biochar and polyphosphate formed simultaneously and were tightly intertwined by one-step pyrolysis. The optimal product (PKBC-400) had the most stable carbon structure and an adequate P-O-P structure with less P loss. Batch experiments illustrated that 92.83% P (ortho-P), 85.94% K, 41.49% Fe, 78.42% Al and 65.60% Mg were continuously released in water from PKBC-400 within 63 days, and the maximum Cr removal rate reached 83.57% (50 mg/L K₂Cr₂O₇, pH=3.0) with an increased BET surface area (304.0557 m²/g) after nutrient release. SEM, IC and ³¹P NMR analyses revealed that the dissolution and hydrolysis of polyphosphates not only realized the sustained release of multiple nutrients but also significantly improved the sustained release performance. The proposed resource utilization strategy provided new ideas for Cr hazard control, biomass waste utilization and fertilizer development.

One-step selective separation and efficient recovery of valuable metals from mixed spent lithium batteries in the phosphoric acid system

The recovery of valuable elements in spent lithium-ion batteries (LIBs) has attracted more and more attention. Efficient recovery of valuable elements from spent LIBs with lower consumption and shorter process is the target that people have been pursuing. In this study, the valuable metals (Ni, Co, Mn and Li) and FePO₄ products are simultaneously recovered from mixed spent LiNi_xCo_yMn_zO₂ and LiFePO₄ in one step under the optimized condition of 0.88 M H₃PO₄, a mass ratio of LFP/NCM of 2:1, a L/S ratio of 33:1 and 80 ℃ for 120 min without additional auxiliary reagents. Over 60 % of acid consumption is reduced and the process of adjusting pH is avoidable. The leaching efficiencies of the valuable elements reach up to 99.1 % for Ni, 98.9 % for Co, 99.6 % for Li and 97.3 % for Mn. Almost all of Fe is precipitated as FePO₄·2H₂O. By means of the empirical model, the research on leaching kinetics demonstrates that the leaching reaction is internal diffusion-controlled with the apparent activation energy of valuable metals less than 30 kJ/mol. Furthermore, the redox reaction mechanism between spent LiBs has been explored. And the intrinsic driving force in the phosphoric acid system is found out. This finding may provide an innovative and selective recycling method for valuable elements from mixed spent LIBs with high economic benefit and fewer environmental footprints.

Zr-Based Metal-Organic Frameworks with Phosphoric Acids for the Photo-Oxidation of Sulfides

Heterogeneous Brønsted acidic catalysts such as phosphoric acids are the conventional activators for organic transformations. However, the photocatalytic performance of these catalysts is still rarely explored. Herein, a novel Zr-based metal-organic framework Zr-MOF-P with phosphoric acids as a heterogeneous photocatalyst has been fabricated, which shows high selectivity and reactivity towards the photo-oxidation of sulfides under white light illumination. A mechanism study indicates that the selective oxygenation of sulfides occurs with triplet oxygen rather than common reactive oxygen species (ROS). When Zr-MOF-P is irradiated, the hydroxyl group of phosphoric acid is converted into oxygen radical, which takes an electron from the sulfides, and then the activated substrates react with the triplet oxygen to form sulfoxides, avoiding the destruction of the catalysts and endowing the reaction with high substrate compatibility and fine recyclability.

Highly Efficient Removal of Lead/Cadmium by Phosphoric Acid-Modified Hydrochar Prepared from Fresh Banana Peels: Adsorption Mechanisms and Environmental Application

In this work, a phosphoric acid (H₃PO₄)-modified hydrochar (BPH200) was prepared at a low temperature (200 °C) in an air atmosphere with fresh banana peels as the raw material. The Cd²⁺ and Pb²⁺ adsorption behaviors and mechanisms of BPH200 were explored. As the temperature rose, co-hydrothermal carbonization of the banana peels and H₃PO₄ enhanced the transformation of phosphorus (P) species. More orthophosphate and metaphosphate were found in BPH200 than in banana peel hydrochar (BP) without modification. The adsorption kinetics for Cd²⁺ and Pb²⁺ followed the pseudo-second-order model. The Redlich-Peterson model best fit the experimental results of the adsorption isotherm, with maximum adsorption capacities of 84.25 and 237.90 mg·g^-1 for Cd²⁺ and Pb²⁺, respectively. H₃PO₄ promoted Cd²⁺ and Pb²⁺ adsorption by forming precipitates, which, respectively, accounted for 32.75 and 41.12% of the total adsorption onto BPH200. In addition, the cation-exchange capacities of BPH200 with Cd²⁺ and Pb²⁺ were weakened compared with those of BP. However, complexation with these two ions strengthened, accounting for 26.68 and 32.81%, respectively, of the total adsorption capacity. This indicated that the adsorption of Cd²⁺ and Pb²⁺ onto BPH200 was dominated by precipitation with minerals and complexation with oxygen-containing functional groups. The removal rates of Cd²⁺ and Pb²⁺ by BPH200 from different water bodies were more than 99.95 and 99.97%, respectively. The addition of BPH200 also decreased the amounts of bioavailable Cd²⁺ and Pb²⁺ in the soil, resulting in relatively high immobilization rates of Cd²⁺ (67.13%) and Pb²⁺ (70.07%).

Molecular insights into the catalytic oxidation of methanol-to-olefins wastewater with phosphoric acid modified sludge biochar

With the development of methanol-to-olefin (MTO) process, the effective disposal of wastewater was one key factor for the long-period and benign development of this technology. Herein, a sludge-based biochar catalyst (GSC-P) was synthesized and used in photo-Fenton reaction for the degradation of MTO wastewater from the outlet of a biological aerated filter. More iron was distributed on the surface of GSC-P catalyst, facilitating the photo-Fenton oxidation of MTO wastewater, with chemical oxygen demand (COD) removal rate of 75.4% and total organic carbon (TOC) removal rate of 62.5%. The 2223 unique molecular formulas assigned by a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in the original MTO wastewater showed that CHO compounds shared the lowest peak numbers (20.2%) but the highest peak abundance (51.6%) among the four groups. Besides, lipids, unsaturated hydrocarbons, lignins and proteins were the main structural types. After photo-Fenton treatment of 60 min, there were 56.7%-74.0% of compounds removed by the analysis of van Krevelen diagram, indicating that the MTO wastewater was degraded efficiently. Three possible evolution processes of dissolved organic matters during the photo-Fenton reaction were disclosed at the molecular-level.

Preparation of formate-free PMA@MOF-808 catalysts for deep oxidative desulfurization of model fuels

Due to the increasingly serious environmental problems caused by the combustion of sulfides in fuel, deep desulfurization of fuel became particularly urgent. Herein, the catalyst (PMA@MOF-808) of the Zr-based metal-organic framework (MOF-808) encapsulating phosphomolybdic acid (PMA) was prepared via a one-pot hydrothermal method. Besides, the formate ions of PMA@MOF-808 were removed by posttreatment with methanol, resulting in formate-free PMA@MOF-808-H catalysts with unsaturated open metal sites. The as-synthesized catalysts were systematically characterized by XRD, FT-IR, SEM, BET, TGA, ¹H NMR and XPS. The catalysts were also applied in catalytic oxidation desulfurization of fuel. The results indicated that the introduction of PMA and the removal of formate ions can improve the desulfurization performance of catalysts. Formate-free 0.2-PMA@MOF-808-H catalyst can reach 100% desulfurization rate for DBT. Besides, the kinetic properties were studied, and the apparent activation energy was 29.34 kJ/mol.

Thermal properties and pyrolysis kinetics of phosphate-rock acid-insoluble residues

In the phosphorous-sulphur two-step process for the clean production of phosphoric acid, a phosphate-rock acid-insoluble residue (PAIR) is a solid filter residue obtained via the phosphoric acid acidolysis of phosphate rock (PR). PAIR combined with other raw materials can be used to prepare cement, ceramics and glasses, opening a potential avenue for large-scale PAIR utilisation. However, the preparation of such materials requires high-temperatures calcination. Understanding the high-temperature thermal properties of PAIR can enable its more targeted comprehensive utilisation or disposal. In this study, the thermal properties and pyrolysis kinetics of PAIR were systematically studied using a multiple heating rate method based on thermogravimetric analysis and a kinetic model. Results showed that from room temperature to 1200 °C, the main changes in the PAIR were the complete removal of fluorine and sulphur, partial removal of phosphorus and conversion of quartz to cristobalite. Moreover, during these processes, H₂O(g), NH₃, N₂, CO₂, SO₂, P₂O₅(g), CO, CF₃⁺ and organic gases were volatilised. Herein, the pyrolysis kinetics of PAIR is divided into five stages. Stage 1 (conversion rate ɑ: 0.05-0.2) conforms to the random nucleation and growth as well as the Avrami-Erofeev (n = 2/3) mechanism; the corresponding mechanism function is F(ɑ) = [-Ln(1 - ɑ)]^2/3. Stage 2 (ɑ: 0.2-0.4) conforms to the first-order chemical reaction mechanism; the corresponding mechanism function is F(ɑ) = -Ln(1 - ɑ). Stage 3 (ɑ: 0.4-0.6) conforms to the phase boundary-controlled reaction and one-dimensional movement mechanism; the corresponding mechanism function is F(ɑ) = ɑ. Stage 4 (ɑ: 0.6-0.8) conforms to the three-dimensional diffusion process (Jander model); the corresponding mechanism function is F(ɑ) = [1 - (1 - ɑ)^1/3]². Stage 5 (ɑ: 0.6-0.95) conforms to the one-dimensional diffusion process; the corresponding mechanism function is F(ɑ) = ɑ².

Phosphomolybdic acid-catalyzed oxidation of waste starch: a new strategy for handling the OCC pulping wastewater

When old corrugated cardboard (OCC) is returned to the paper mill for repulping and reuse, the starch, which is added to the paper surface as a reinforcement agent, is dissolved into the pulping wastewater. Most of the OCC pulping wastewater is recycled to save precious water resources; however, during the water recycling process, the accumulation of dissolved starch stimulates microbial reproduction, which causes poor water quality and putrid odor. This problem seriously affects the stability of the papermaking process and product quality. In this study, phosphomolybdic acid (H₃PMo₁₂O₄₀, abbreviated as PMo₁₂) was utilized to catalyze the waste starch present in papermaking wastewater to monosaccharides, realizing the resource utilization of waste starch. The results showed that the optimized yield of total reducing sugar (78.68 wt%) and glycolic acid (12.83 wt%) was achieved at 145 °C with 30 wt% PMo₁₂ at pH 2, which is equivalent to 91.51 wt% starch recovered from wastewater for resource utilization. In addition, the regeneration of the reduced PMo₁₂ was realized by applying a potential of 1 V for 2 h. Overall, this study has theoretical significance and potential application value for resource utilization of waste starch in OCC pulping process and cleaner management of OCC waste paper.

Exploring the potential effect of Achnatherum splendens L.-derived biochar treated with phosphoric acid on bioavailability of cadmium and wheat growth in contaminated soil

Biochar remediation efficiency could be enhanced through numerous treatments such as acids treatment. Still, there has little work done on H₃PO₄-treated biochar particularly biochar derived from Achnatherum splendens L. feedstock. Therefore, the present study has been conducted to further explore the potential effect of A. splendens L.-derived biochar treated with H₃PO₄ on bioavailability of Cd and wheat growth in Cd contaminated soil. Phosphoric acid and untreated biochar each applied at the rate of 1% and 2% to Cd contaminated/spiked soil in pots and having one contaminated/spiked control without biochars amendment. The results show that 2% phosphoric acid-treated biochar has the most significant increase in plant height, shoot dry weight, and grain yield of wheat as compared to contaminated control. As compared to contaminated control, maximum improvement in total chlorophyll contents, photosynthetic rate, transpiration rate, and stomatal conductance occurred with 2% phosphoric acid-treated biochar. The 2% phosphoric acid-treated biochar also declined bioavailable Cd in soil by 53%, and its accumulation in shoot and grain by 65% and 90%, respectively, compared to contaminated control. Overall, phosphoric acid-treated biochar most effectively immobilized Cd in soil and reducing its uptake and translocation to grains. Therefore, A. splendens L.-derived biochar treated with phosphoric acid could be successfully utilized for remediation of contaminated soil.

Preparation of phosphoric acid modified antibiotic mycelial residues biochar: Loading of nano zero-valent iron and promotion on biogas production

Antibiotic mycelial residues (AMRs), as recyclable hazardous waste, can realize efficient utilization by reasonable treatment. To solve the problems of undeveloped pore structure and low specific surface area existed in AMR biochar, this study first modified biochar by phosphoric acid (H₃PO₄) to prepare PBC (H₃PO₄-modified biochar). Then, PBC was used as carrier to load nano zero-valent iron (nZVI) for preparation of nZVI/PBC. Finally, the biochar materials were used to promote anaerobic digestion (AD) of corn straw. The results showed that H₃PO₄-modification can effectively improve the specific surface area, pore structure, and electron donating capacity of AMRs biochar. The using of PBC as carrier to load nZVI attenuated the agglomeration of nZVI particles. Both PBC and nZVI/PBC improved the AD process, with biogas yield enhanced by 29.63% and 29.26%, respectively. The nZVI/PBC exhibited higher ability in maintaining the stability of AD system and promotion of fiber degradation than PBC.

Surface modification of spent coffee grounds using phosphoric acid for enhancement of methylene blue adsorption from aqueous solution

In this study, the surface of the spent coffee grounds (SCG) was activated using phosphoric acid to increase the removal efficiency of methylene blue (MB) in aqueous solution, which is one of the harmful substances emitted in industrial processes. According to Fourier transform infra-red analysis, after phosphorylation of the SCG (PSCG), P = O group, P-O-C (aromatic) bond, P = OOH and P-O-P were newly introduced on the surface of the adsorbent, and the peaks of carboxyl groups and OH-group were large and broad. In addition, the surface area and mesopore range of the PSCG adsorbent were increased, and the structure changed, which enabled easy adsorption of MB. The process of adsorbing MB from aqueous solution using PSCG was more suitable for the pseudo-second order and Langmuir models, and the adsorption process was closer to chemisorption than physical adsorption. The maximum adsorption capacity of PSCG was 188.68 mg/g. As a result of the reuse test, PSCG showed excellent performance with a high removal efficiency of 90% up to four consecutive uses. PSCG modified with phosphoric acid, an abundant lignocellulose-based biosorbent that is readily available everywhere, is a promising adsorbent capable of adsorbing MB in aqueous solution.

Dihydroxybenzene isomers electrochemical sensor based on activated carbon sensitive material activated by mechanochemistry and low-dosage phosphoric acid

A dihydroxybenzene isomers electrochemical sensor based on bamboo activated carbon (MCPBAC) sensitive material activated by mechanochemistry and low-dosage phosphoric acid was fabricated in this work. The sensor, modified by MCPBAC with GCE, can significantly distinguish and sensitively measure hydroquinone (HQ) and catechol (CC). The MCPBAC exhibits a well-developed porous structure, high specific surface area, and good electrical conductivity. Using differential pulse voltammetry (DPV), wide linear ranges for both HQ and CC are 0.6-600 μM, with low detection limits (S/N = 3) for both of 0.2 μM. The dihydroxybenzene isomers electrochemical sensor has wide application prospects in the determination of trace HQ and CC in environmental water.

Heterogeneous photooxidation of 6:2 polyfluoroalkyl phosphoric acid diester on dust mineral components under simulated sunlight and the influence of relative humidity and oxygen

Polyfluoroalkyl phosphoric acid diesters (diPAPs) have been widely and increasingly detected in various environmental mediums. The degradation of diPAPs brings perfluoroalkyl carboxylic acids (PFCAs) concerned of adverse health effects. DiPAPs mainly occur in particulate matter in ambient air and their photo-degradation behaviors have not been investigated. In this study, heterogeneous photo-degradation of 6:2 diPAP was studied on four model mineral components in ambient dust. 6:2 diPAP was found to undergo a fast degradation on titanium dioxide (TiO₂) particles as well as on artificial mineral dust containing TiO₂ (2.67% in mass) to produce C5-C7 PFCAs and other intermediates. Based on monitored intermediates and further degradation tests on important intermediates, thermodynamic calculation of energy barrier and Gibbs Free Energy was used to explain the observed degradation patterns and accordingly the degradation pathways of diPAPs were proposed. The increase in relative humidity promotes the production of hydroxyl radicals, which enhances the hydrolysis of 6:2 mono- and di-PAPs and the yield of C5 and C7 PFCAs. Oxygen is critical for radical formation, which bypasses the production of fluorotelomer carboxylic acid. Results of this study for the first time demonstrate that diPAP may account for additional PFCA sources in both indoor and outdoor environments and the heterogeneous degradation pathways were different from those of volatile fluorotelomer alcohols.

The quality of etched enamel in different regions and tooth types and its significance in bonding and the development of white spot lesions

OBJECTIVES

To quantify differences in the etch quality of enamel within and between human teeth, which has not previously been attempted.

MATERIALS AND METHODS

The buccal right and left halves of 27 extracted human teeth were randomly allocated to scanning electron microscopy (SEM) or micro-computed tomography (μCT) for evaluation. The buccal surfaces were pumiced, etched with 37% phosphoric acid gel etchant for 15 seconds, rinsed, and air dried. Each tooth was divided into three regions (incisal, middle, and cervical) and viewed after etching at 1200× magnification with SEM. The μCT scans were taken before and after etching to calculate apparent and material mineral densities.

RESULTS

SEM showed greater aprismatic enamel and poorer etch quality (ie, significantly less percentage enamel) for the posterior than anterior teeth and for the cervical region than for the incisal and middle regions of all teeth. Although there were no density differences prior to etching, μCT demonstrated that etching increased material density significantly more for the anterior than posterior teeth. Prior to etching, the enamel in the cervical regions was significantly less dense than the enamel in the middle or incisal regions. Etching significantly increased the material density of all three regions, which decreased initial regional differences. After etching, the apparent density of the cervical region remained significantly lower than the densities of the other two regions.

CONCLUSIONS

Based on SEM and μCT, there is greater aprismatic enamel and inferior etch quality in the cervical regions of all tooth types and is clinically significant in explaining the failure of sealant retention and the propensity for white spot lesions.

The Effect of Deproteinizing Agents on Bond Strength of Resin-based Materials to Enamel: A Systematic Review and Meta-Analysis of In Vitro Studies

PURPOSE

To systematically review the literature to evaluate whether the bond strength of resin-based materials to enamel is affected by deproteinizing agents.

MATERIALS AND METHODS

This systematic review and meta-analysis was conducted according to the PRISMA statement. PubMed, ISI Web of Science, Cochrane Library, SciELO, Scopus, LILACS, IBECS, and BVS databases were screened up to December 2020. Eligibility criteria included in vitro studies that reported the effect of a deproteinizing agent applied before or after acid etching on the immediate or long-term bond strength of resin-based materials to enamel. The meta-analysis was carried out using Review Manager (version 5.3.5). A global comparison was performed with the standardized mean difference based on random-effect models at a significance level of α = 0.05.

RESULTS

A total of 23 studies were included in the meta-analysis. In all the studies, only the immediate bond strength was evaluated. The bond strength of the materials was improved by the application of NaOCl or papain prior to enamel etching with phosphoric acid (p ≤ 0.006). None of the deproteinizing agents had a significant effect when applied after etching with phosphoric acid (p ≥ 0.27).

CONCLUSIONS

Based on in vitro studies, deproteinization with sodium hypochlorite or papain-based agents increases the immediate bond strength of resin-based materials to enamel only when used prior to phosphoric-acid etching.

Establishment of a HPLC-MS/MS Detection Method for Glyphosate, Glufosinate-Ammonium, and Aminomethyl Phosphoric Acid in Tea and Its Use for Risk Exposure Assessment

The tea shrub is grown in long-standing orchards, an environment that is suitable for persistent weed growth, which is increasingly controlled by herbicides. Therefore, there is increasing concern that tea consumers may be exposed to herbicide residues. In this study, the levels of glufosinate-ammonium (GLU), glyphosate [N-(phosphonomethyl) glycine; PMG], and its metabolite aminomethyl phosphoric acid (AMPA) were determined in tea samples by HPLC-MS/MS using several current purification methods and a new method that we developed herein. The matrix effect of our proposed method was between -27.3 and 27.7%, which was lower than that in other methods, indicating that this method effectively reduced the interference of tea matrix in the mass spectrometry process. This method was used to determine the levels of PMG, GLU, and AMPA in 780 samples, including six traditional Chinese teas (green tea, black tea, oolong tea, dark tea, white tea, and yellow tea) and a floral tea, from 14 provinces of China. Probability estimates showed that the 95th percentile risk entropy values of the three pesticide residues were far below the acceptable risk level. The risk assessment results showed that exposure to PMG, GLU, and AMPA caused by drinking tea beverages poses no significant risk to human health.

Remediation of arsenic-cationic metals from smelter contaminated soil by washings of Na2EDTA and phosphoric acid: removal efficiencies and mineral transformation

Sequential and combined soil washing tests of Na₂EDTA and phosphoric acids were conducted to remediation soil contaminated with arsenic and cationic metals (cadmium, copper, and lead) at a former metal smelter. The aim of the testing was to improve the heavy metals removal efficiency and investigate the mechanism of the influence of soil minerals on washing efficiency, including the influence on soil mineral, metal oxides, and functional groups of soil surface. The results indicated that the combined washing of Na₂EDTA and phosphoric acid was effective in removing both arsenic and cationic metals from contaminated soil and had synergy effect for most target metals. The results of metal removal efficiency indicated that the washing agent, washing mode, and washing times influenced the removal efficiencies of arsenic and cationic metals. The spectroscopic analysis demonstrated that sequential and combined washings were effective in dissolving and reforming soil minerals compared with single washing. The promoted complexation, ligand exchange, desorption, and inhibition of adsorption resulted in the synergistic effect for most target metals under combined washing.

Sorption of U(VI), Mn (II), Cu(II), Zn(II), and Cd(II) from multi-component phosphoric acid solutions using MARATHON C resin

Crude phosphoric acid is a vital component used in making phosphate fertilizers. Depending on the processes used in producing the crude phosphoric acid, it usually contains organic and inorganic contaminants. To make environmentally friendly phosphate fertilizers, these contaminants must be removed from the crude phosphoric acid stock used in making fertilizers. In this paper, commercially available strong cation exchange resin, Marathon C, was used to study the adsorptive removal of U(IV), Mn(II), Cd(II), Zn(II), and Cu(II) from synthetic multi-component phosphoric acid solutions and commercial crude phosphoric acid. Important parameters on the adsorption process such as the effects of contact time, initial metal ion concentration, sorbent dose, and concentration of phosphoric acid were investigated. The results suggested that the adsorption process reached equilibrium within 240 min for the five metal ions studied and the resin had adsorptive affinity for the metal ions in the order of U(IV) > Zn(II) > Cu(II) > Mn(II) > Cd(II). The results from the kinetics and isotherm models from the studies are very consistent with pseudo-second-order kinetic and Langmuir isotherm models. Simultaneous adsorptive removal of metal ions from the crude phosphoric acid strongly suggests that the Marathon C resin could be used in removing toxic metal ions from crude phosphoric acids used in making phosphate fertilizer.

Preparation, characterization, and efficient chromium (VI) adsorption of phosphoric acid activated carbon from furfural residue: an industrial waste

Furfural residue (FR) is an inevitable by-product of industrial furfural production. If FR is not managed properly, it will result in environmental problems. In this study, FR was used as a novel precursor for activated carbon (AC) production by H₃PO₄ activation under different conditions. Under optimum conditions, the prepared FRAC had high BET surface area (1,316.7 m²/g) and micro-mesoporous structures. The prepared FRAC was then used for the adsorption of Cr(VI). The effect of solution pH, contact time, initial Cr(VI) concentration, and temperature was systematically studied. Characterization of the adsorption process indicated that the experimental data were well-fitted by the Langmuir isotherm model and pseudo-second-order kinetics model. The maximum adsorption capacity of 454.6 mg/g was achieved at pH 2.0, which was highly comparable to the other ACs reported in the literatures. The preparation of FRAC using H₃PO₄ activation can make use of FR's characteristic acidity, which could make it preferable in practical industrial production.

Preparation and characterization of activated carbon developed from cotton cloth residue activated with phosphoric acid: adsorption of clofibric acid

Cotton cloth waste was used as a precursor to prepare activated carbon (ACCs) chemically activated with phosphoric acid. Adsorption behavior of prepared ACCs was correlated with physicochemical proprieties. The pore volume and BET surface of ACCs were determined by nitrogen adsorption isotherms and scanning electron microscopy was used to observe their surface morphologies. Fourier transform infrared (FTIR) spectroscopy analysis and pH point zero charge (pH_PZC) were conducted to determine chemical properties. Under the optimal conditions: 50% impregnation ratio and thermal treatment under N₂ flow at 600 °C during 60 min, the activated carbon prepared exhibits a high surface area 1,150 m²/g, 0.501 cm³/g micropore volume and an excellent adsorption performance. The adsorbed amount of clofibric acid is found to be 9.98 and 83 mg/g at, respectively, initial CA concentration of 10 and 100 mg/L at pH 3.0 and 20 °C. Diffusion and chemisorption are the steps controlling the adsorption of CA onto ACC 50% and the equilibrium data were well described by Freundlich isotherm.

Enhanced adsorption of copper ions by phosphoric acid-modified Paeonia ostii seed coats

Novel adsorbent, phosphoric acid-modified Paeonia ostii seed coats (PA-PSC) were successfully prepared by low-temperature pyrolysis to effectively remove Cu(II) from aqueous solution. The results revealed that equilibrium adsorption capacity (q_e) of PA-PSC for Cu(II) was notably enhanced up to 4-folds compared with the raw PSC. FT-IR and XPS analyses suggested that the adsorption of Cu(II) by PA-PSC was primarily ascribed to electrostatic forces and complexing effects. Besides, equilibrium and kinetic studies demonstrated that Freundlich and pseudo-second-order models were the actually fairly good approximations of Cu(II) adsorption. Thermodynamic analysis revealed that the adsorption of Cu(II) onto PA-PSC was a chemical, endothermic, and spontaneous process. Lastly, reusability study further confirmed the applicability of PA-PSC as a promising adsorbent for removing Cu(II) from aqueous solution.

Effect of settling time on the adsorption of 137Cs onto AMP in the AMP-coprecipitation method

Ten sets of experiments with different settling times were conducted to investigate the effect of settling time on the adsorption of ¹³⁷Cs in seawater onto ammonium phosphomolybdate (AMP). The weight yields of AMP and ¹³⁷Cs yields in all groups were generally higher than 90%. The average weight yields of AMP in each group varied from 91.8 ± 0.5 to 95.9 ± 0.6% (1 SD), and the average ¹³⁷Cs yields in each group varied from 88.3 ± 3.0 to 97.8 ± 3.7% (1 SD). The results showed that equilibrium between Cs and AMP is established immediately after the addition of stable Cs carrier and AMP, implying that the solution could be filtered immediately after the coprecipitation forms. IAEA seawater proficiency test exercises also confirmed that the AMP precipitate does not need to be treated statically in the case of 2 g AMP and 3.7 mg Cs carrier in a seawater sample solution. The modified AMP preconcentration method simultaneously meets the requirements of routine and nuclear emergency monitoring of ¹³⁷Cs in seawater.

Nitrogen-deficient g-C3Nx/POMs porous nanosheets with P-N heterojunctions capable of the efficient photocatalytic degradation of ciprofloxacin

The direct shedding of piperazine rings is critical for the degradation of antibiotic persistent organic pollutants. In this work, nitrogen-deficient g-C₃N₄ loaded with polyoxometalates porous photocatalysts with P-N heterojunctions were carried out through the formation of chemical bonds between the nitrogen-deficient C⁺ in g-C₃N_x and the bridging oxygen in polyoxometalates (POMs), including phosphomolybdic acid (PMA), phosphotungstic acid (PTA) and silicotungstic acid (STA). The adsorption and photocatalysis experiments confirm the ability of the g-C₃N_x/POMs nanosheets to efficiently remove ciprofloxacin via the synergistic effects of adsorption and photo-catalysis. Approximately, g-C₃N_x/POMs-30 exhibits the optimal degradation ability, and the degradation rates of g-C₃N_x/PMA-30, g-C₃N_x/PTA-30 and g-C₃N_x/STA-30 could respectively reach 93.1%, 97.4% and 95.6% within only 5 min under visible light. The free radical scavenging experiment and ESR free radical capture experiments confirm that ·OH and ·O₂^- are free radicals that effectively degrade CIP. According to the results of the LC-MS analysis, the intermediates produced after CIP degradation and the efficient degradation pathway are proposed. The direct shedding of piperazine rings in the decarboxylation and defluorination process leads to the most efficient degradation of CIP into the small molecules.

Does Etching of the Enamel with the Rubbing Technique Promote the Bond Strength of a Universal Adhesive System?

AIM

The aim of this in vitro research was to study the effect of etching by phosphoric acid with rubbing technique on the shear bond strength (SBS) of adhesive universal to enamel.

MATERIALS AND METHODS

Sixty extracted teeth were obtained. Three application methods (self-etch, etch-and-rinse, and etch-and-rinse with rubbing technique) were performed to bond the enamel surfaces by a universal adhesive. After 24 hours of immersion in water at 37°C, the specimens were prepared for the SBS test. Scanning electron microscopy was performed to observe the adhesive-enamel interfaces. Optical numeric microscope was used to observe the failure style. Statistical analyses were done with one-way analysis of variance test.

RESULTS

Statistically significant higher bond strength values were observed for etch-and-rinse mode with rubbing technique (25.98 ± 5.70) MPa then for the etch-and-rinse without rubbing (22.07 ± 5.27) MPa and self-etch modes (9.96 ± 2.98) MPa.

CONCLUSION

Enamel etched by 37% phosphoric acid with rubbing technique for 20 seconds showed an increase in the SBS of the universal adhesive to enamel surfaces. The tags of the adhesive can be presented more efficiently by rubbing the acid before the bonding process, consequently, an optimal interface for the bonding.

CLINICAL SIGNIFICANCE

According to the results of this in vitro study, the selective enamel etching mode with rubbing technique is advisable when using the universal adhesive, as it significantly increased the bond strength of this adhesive to enamel surfaces. The clinician should etch the enamel using phosphoric acid with rubbing technique for 20 seconds to promote the bond strength of the universal adhesive system.

Cadmium and iron removal from phosphoric acid using commercial resins for purification purpose

Three commercial resins bearing sulfonic, amino phosphonic, or phosphonic/sulfonic reactive groups have been tested for the removal of iron and cadmium from phosphoric acid solutions. The sorption properties are compared for different experimental conditions such as sorbent dosage (0.5-2.5 g L-1), phosphoric acid concentration (from bi-component solutions, 0.25-2 M), and metal concentrations (i.e., in the range 0.27-2.7 mmol Cd L-1 and 0.54 mmol Fe L-1) with a special attention paid to the impact of the type of reactive groups held on the resins. The sulfonic-based resin (MTC1600H) is more selective for Cd (against Fe), especially at high phosphoric acid concentration and low sorbent dosage, while MTS9500 (aminophosphonic resin) is more selective for Fe removal (regardless of acid concentration and sorbent dosage). Equilibrium is reached within 2-4 h. The resins can be ranked in terms of cumulative sorption capacities according the series: MTC1600H > MTS9570 > MTS 9500. Sulfuric acid (0.5-1 M) can be efficiently used for the desorption of both iron and cadmium for MTC1600H, while for MTS9570 (phosphonic/sulfonic resin) sulfuric acid correctly desorbs Cd (above 96% at 1 M concentration), contrary to Fe (less than 30%). The aminophosphonic resin shows much poorer efficiency in terms of desorption. The sulfonic resin (i.e., MTC1600H) shows much higher sorption capacity, better selectivity, comparable uptake kinetics (about 2 h equilibrium time), and better metal desorption ability (higher than 98% with 1 M acid concentration, regardless of the type of acid). This conclusion is confirmed by the comparison of removal properties in the treatment of different types of industrial phosphoric acid solutions (crude, and pre-treated H3PO4 solutions). The three resins are inefficient for the treatment of crude phosphoric acid, and activated charcoal pre-treatment (MTC1600H reduced cadmium content by 77%). However, MTC1600H allows removing over 93% of Fe and Cd for H3PO4 pre-treated by TBP solvent extraction, while the others show much lower efficiencies (< 53%).

Effect of Soil Washing Solutions on Simultaneous Removal of Heavy Metals and Arsenic from Contaminated Soil

In this study, we investigated the feasibility of using a solution of sulfuric acid and phosphoric acid as an extraction method for soil-washing to remove Cu, Pb, Zn, and As from contaminated soil. We treated various soil particles, including seven fraction sizes, using sulfuric acid. In addition, to improve Cu, Pb, Zn, and As removal efficiencies, washing agents were compared through batch experiments. The results showed that each agent behaved differently when reacting with heavy metals (Cu, Pb, and Zn) and As. Sulfuric acid was more effective in extracting heavy metals than in extracting As. However, phosphoric acid was not effective in extracting heavy metals. Compared with each inorganic acid, As removal from soil by washing agents increased in the order of sulfuric acid (35.81%) < phosphoric acid (62.96%). Therefore, an enhanced mixture solution using sulfuric acid and phosphoric acid to simultaneously remove heavy metals and As from contaminated soils was investigated. Sulfuric acid at 0.6 M was adopted to combine with 0.6 M phosphoric acid to obtain the mixture solution (1:1) that was used to determine the effect for the simultaneous removal of both heavy metals and As from the contaminated soil. The removal efficiencies of As, Cu, Pb, and Zn were 70.5%, 79.6%, 80.1%, and 71.2%, respectively. The combination of sulfuric acid with phosphoric acid increased the overall As and heavy metal extraction efficiencies from the contaminated soil samples. With the combined effect of dissolving oxides and ion exchange under combined washings, the removal efficiencies of heavy metals and As were higher than those of single washings.

Significant Enhancement of Gaseous Elemental Mercury Recovery from Coal-Fired Flue Gas by Phosphomolybdic Acid Grafting on Sulfurated γ-Fe2O3: Performance and Mechanism

The existing technologies to control Hg emissions from coal-fired power plants can be improved to achieve the centralized control of Hg⁰ emissions, which continue to pose a risk of Hg exposure to human populations. In this work, MoS_x@γ-Fe₂O₃, formed by the sulfuration of phosphomolybdic acid (HPMo)-grafted γ-Fe₂O₃, was developed as a magnetic and regenerable sorbent to recover gaseous Hg⁰ from coal-fired flue gas as a cobenefit to the use of wet electrostatic precipitators. The thermal stability of γ-Fe₂O₃ was notably enhanced by HPMo grafting; thus, the magnetization of MoS_x@γ-Fe₂O₃ hardly decreased during the application. The kinetic analysis indicates that the chemical adsorption of gaseous Hg⁰ was mainly dependent on the amounts of surface S₂^2- and surface adsorption sites. Although the amount of S₂^2- on sulfurated γ-Fe₂O₃ decreased after HPMo grafting, the amount of surface adsorption sites significantly increased due to the formation of a layered MoS_x structure on the surface. Therefore, the ability of sulfurated γ-Fe₂O₃ to capture Hg⁰ was improved considerably after HPMo grafting. Furthermore, low concentrations of gaseous Hg⁰ in coal-fired flue gas can be gradually enriched by at least 1000 times by MoS_x@γ-Fe₂O₃, which facilitates the recovery and centralized control of gaseous Hg⁰ in flue gas.

Batch interaction of emerging tetracycline contaminant with novel phosphoric acid activated corn straw porous carbon: Adsorption rate and nature of mechanism

In this work, corn straw (CS) based porous carbon was prepared by one-step phosphoric acid (H₃PO₄) low temperature activation. The impregnation ratios (H₃PO₄/CS, g/g) played an important role in the pore development. ACS_300-1 engineered at 300 °C and the impregnation ratio of 1.0 showed the maximal specific surface area of 463.89 m²/g with total pore volume of 0.387 cm³/g, attaining a high tetracycline (TC) uptake of 227.3 mg/g. The adsorption of TC onto ACS_300-1 was found tolerant with wide pH (2.0-10.0) and high ionic strength (0 - 0.5 M). The adsorption data can be fitted well by the pseudo-second order kinetic model and Langmuir isotherm model. The endothermic and spontaneous properties of the adsorption system was implied by Thermodynamic study. The findings of the current work conclude that one-step H₃PO₄ activation is a green and promising method for corn straw based porous carbon that may be found with great potentials in antibiotic containing wastewater treatment.

Towards establishing indicative values for metabolites of organophosphate ester contaminants in human urine

In 2015, nine laboratories from Belgium, USA, Canada, China, and Australia participated in an interlaboratory exercise to quantify metabolites of organophosphate ester (OPE) contaminants in pooled human urine. Pooled human urine available as SRM 3673 (Organic contaminants in non-smokers' urine) was obtained from the U.S. National Institute of Standards and Technology and was analyzed for its content of OPE metabolites. Each participating laboratory received 10 mL sample and used its own validated method and standards to report the concentrations of the OPE metabolites of its choice. Four OPE metabolites were consistently measured by most laboratories and they were the following diesters: bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPHP), bis(2-chloroethyl) phosphate (BCEP), and bis(1-chloro-2-propyl) phosphate (BCIPP). Concentrations of other OPE metabolites in SRM 3673 were also reported but are only considered as informative values since they were measured by three laboratories at most. All laboratories used liquid chromatography with tandem mass spectrometry (LC-MS/MS) with or without solid-phase extraction (SPE). This is the first study to report indicative values for OPE metabolites in a human urine Standard Reference Material. It is expected that these indicative values obtained for these four metabolites will be used as quality control to ensure compatibility of results in biomonitoring studies and by other researchers who validate their own methods for the quantification of OPE metabolites in human urine.