Efficient Elimination of Chlorinated Organics on a Phosphoric Acid Modified CeO2 Catalyst: A Hydrolytic Destruction Route

The development of efficient technologies to prevent the emission of hazardous chlorinated organics from industrial sources without forming harmful byproducts, such as dioxins, is a major challenge in environmental chemistry. Herein, we report a new hydrolytic destruction route for efficient chlorinated organics elimination and demonstrate that phosphoric acid-modified CeO₂ (HP-CeO₂) can decompose chlorobenzene (CB) without forming polychlorinated congeners under the industry-relevant reaction conditions. The active site and reaction pathway were investigated, and it was found that surface phosphate groups initially react with CB and water to form phenol and HCl, followed by deep oxidation. The high on-stream stability of the catalyst was due to the efficient generation of HCl, which removes Cl from the catalyst surface and ensures O₂ activation and therefore deep oxidation of the hydrocarbons. Subsequent density functional theory calculations revealed a distinctly decreased formation energy of an oxygen vacancy at nearest (V_O-1) and next-nearest (V_O-2) surface sites to the bonded phosphate groups, which likely contributes to the high rate of oxidation observed over the catalyst. Significantly, no dioxins, which are frequently formed in the conventional oxidation route, were observed. This work not only reports an efficient route and corresponding phosphate active site for chlorinated organics elimination but also illustrates that the rational design of the reaction route can solve some of the most important challenges in environmental catalysis.

Adsorption of cadmium and lead ions by phosphoric acid-modified biochar generated from chicken feather: Selective adsorption and influence of dissolved organic matter

To improve the adsorption efficiency, a H₃PO₄-modified biochar (CFCP) was prepared using chicken feather and applied to Cd²⁺ and Pb²⁺ adsorption. The pseudo-second-order model could explain the Cd²⁺ and Pb²⁺ adsorption behavior. CFCP had faster adsorption rate than non-modified biochar (CFC2). The Langmuir and Freundlich isotherm could better describe the Cd²⁺ and Pb²⁺ adsorption, respectively. The value of q_m for Cd²⁺ adsorption and K_F for Pb²⁺ adsorption by CFCP was 7.84 mg·g^-1 and 24.41 mg^1-(1/n)·L^1/n·g^-1, which was 1.38 and 5.41 times of the corresponding results of CFC2. Relative to Cd²⁺, Pb²⁺ was selectively adsorbed by biochars in the binary metal system. Phosphate precipitation explained in part the selective adsorption of Pb²⁺. Proline, glucose, and pH (4-6) had little influence on Cd²⁺ and Pb²⁺ adsorption. Electrostatic interaction, precipitation, and O-H bonds were the primary adsorption mechanisms. The increased N-containing heterocycles of CFCP accounted for the increased Cd²⁺ and Pb²⁺ adsorption.

Effectiveness of Etching by Three Acids on the Morphological and Chemical Features of Dentin Tissue

AIM

The purpose of this study was to evaluate the microscopic and chemical effects of phosphoric acid gel, phosphoric acid liquid, and polyacrylic acid application for 15 seconds (s) on coronal dentin.

MATERIALS AND METHODS

Twelve extracted teeth were selected. Three etching acids were used to prepare the dentin surfaces. Scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDX) were used to analyze the chemical and morphological changes of the dentinal surfaces, including the depth of demineralization. Collected data were statistically analyzed by the one-way analysis of variance test.

RESULTS

Dentin etched with phosphoric acid gel or liquid showed greater peritubular dentin dissolution, including complete removal of the smear layer. In addition, there were many silica particles on the dentin etched by phosphoric acid gel 37%. The dentin that was etched with 25% polyacrylic acid for 15 seconds showed no smear layer removal. Chemical analysis (EDX) showed that dental surfaces etched with phosphoric acid liquid 37% for 15 seconds showed the strongest mineral dissolution at the calcium surface, with a calcium content of 5.25%. On the other hand, EDX analysis of the dental surface etched with 25% polyacrylic acid showed more surface enrichment in calcium (17.19%).

CONCLUSION

Although phosphoric acid (gel or liquid) 37% cleans the dental surface, phosphoric acid gel precipitates silica particles on the etched dentin surface. These particles cannot be removed by rinsing off this acid. The application of polyacrylic acid for 15 seconds does not noticeably demineralized dentin, nor remove the smear layer.

CLINICAL SIGNIFICANCE

The clinician should use phosphoric acid (gel or liquid) to clean dental surfaces to prepare them for the bonding process. The low demineralizing effects of the polyacrylic acid permits its use near the pulp.

Enamel Etching for Universal Adhesives: Examination of Enamel Etching Protocols for Optimization of Bonding Effectiveness

OBJECTIVE

The purpose of this study was to evaluate whether different enamel etching methods with reduced etching times would improve the bonding effectiveness of universal adhesives.

METHODS AND MATERIALS

Three enamel etching methods, phosphoric acid ester monomer (PPM) etching, phosphoric acid (PPA) etching, and polyalkenoic acid (PLA) etching, and three universal adhesives, G-Premio Bond (GP), Prime&Bond elect (PE), and Scotchbond Universal Adhesive (SU), were evaluated. Initial bond strengths and fatigue strengths of universal adhesives to ground enamel and ground enamel etched for less than one, five, 10, and 15 seconds using different etching methods were determined. The bonded fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred with a staircase method. Atomic force micrograph (AFM) observations along with measurements of surface Ra roughness and modified surface area of enamel with different etching protocols were also conducted.

RESULTS

The bond fatigue durability of universal adhesives to enamel with PPA etching from less than one to 15 seconds and PLA etching for 15 seconds was significantly higher than that to ground enamel. The bond fatigue durability to enamel with PPM etching was not increased compared with ground enamel. The surface Ra roughness and surface area obtained with AFM of enamel increased after PPA and PLA etching, and those values were significantly higher than those of ground enamel. Furthermore, surface Ra roughness and surface area with PPA etching were significantly higher than those with PLA etching. However, surface Ra roughness and surface area of enamel with PPM etching were similar to those of ground enamel regardless of etching time.

CONCLUSION

PPA etching for less than one to 15 seconds and PLA etching for 15 seconds improve universal adhesive bonding, surface Ra roughness, and surface area of enamel. However, PPM etching is not effective, regardless of etching time, in improving bonds strengths, increasing surface roughness, and increasing surface area.

Effect of Phosphoric Acid Containing MMP-Inactivator on the Properties of Resin Bonding to Eroded Dentin

PURPOSE

To evaluate the effect of two phosphoric acids containing protease inactivators (chlorhexidine and proanthocyanidin) on the resin/eroded-dentin microtensile bond strength (μTBS), nanoleakage (NL), and in situ degree of conversion (DC) of three universal adhesives applied in the etch-and-rinse mode.

MATERIALS AND METHODS

One hundred twenty-six molars were randomly assigned to 18 experimental conditions according to the combination of the independent variables: eroded dentin (soft drink and citric acid), adhesive (Prime&Bond Elect [PBE, Dentsply Sirona], Scotchbond Universal Adhesive [SBU, 3M Oral Care], and Tetric N-Bond Universal [TEU, Ivoclar Vivadent]), and acid pretreatment (conventional phosphoric acid [CP acid]; chlorhexidine acid [CHX acid]; and proanthocyanidin acid [PA acid]). After restorations, specimens were sectioned into resin-dentin sticks (ca 0.8 mm2) that were then tested under tension (crosshead speed: 0.5 mm/min). Selected sticks from each tooth were used to evaluate NL and DC. Data from all tests were subjected to three-way ANOVA and Tukey's test (α=0.05).

RESULTS

Dentin eroded with citric acid showed a significant reduction in μTBS for each adhesive in comparison to dentin eroded with the soft drink (p < 0.001). For dentin eroded with CHX acid and PA acid, the μTBS (p > 0.03) significantly improved and NL decreased for all adhesives (p < 0.004); in addition, the DC improved for two of the three adhesives tested (SBU and TEU) (p < 0.03) when CHX acid and PA acid were compared to CP acid.

CONCLUSION

The addition of chlorhexidine and proanthocyanidin to phosphoric acid improved the adhesive performance when compared with conventional phosphoric acid, without jeopardizing adhesive polymerization at the resin/eroded-dentin interface.

Chemically activated hydrochar as an effective adsorbent for volatile organic compounds (VOCs)

Hydrochars derived from hickory wood and peanut hull through hydrothermal carbonization were activated with H₃PO₄ and KOH to improve their performance as a volatile organic compound (VOC) adsorbent. Polar acetone and nonpolar cyclohexane were used as representative VOCs. The VOC adsorptive capacities of the activated hydrochars (50.57-159.66 mg⋅g^-1) were greater than that of the nonactivated hydrochars (15.98-25.36 mg⋅g^-1), which was mainly caused by the enlargement of surface area. The significant linear correlation (R² = 0.984 on acetone, and R² = 0.869 on cyclohexane) between BET surface areas of hydrochars and their VOC adsorption capacities, together with the obvious adsorption exothermal peak of differential scanning calorimetry curve confirmed physical adsorption as the dominating mechanism. Finally, the reusability of activated hydrochar was tested on H₃PO₄ activated hickory hydrochar (HHP), which had higher acetone and cyclohexane adsorption capacities. After five continuous adsorption desorption cycles, the adsorptive capacities of acetone and cyclohexane on HHP decreased by 6.2% and 7.8%, respectively. The slight decline in adsorption capacity confirmed the reusability of activated hydrochar as a VOC sorbent.

Effect of Reduced Phosphoric Acid Pre-etching Times on Enamel Surface Characteristics and Shear Fatigue Strength Using Universal Adhesives

PURPOSE

To examine the effect of reduced phosphoric acid pre-etching times on enamel fatigue bond strength of universal adhesives and surface characteristics by using atomic force microscopy (AFM).

MATERIALS AND METHODS

Three universal adhesives were used in this study (Clearfil Universal Bond [C], G-Premio Bond [GP], Scotchbond Universal Adhesive [SU]). Four pre-etching groups were employed: enamel pre-etched with phosphoric acid and immediately rinsed with an air-water spray, and enamel pre-etched with phosphoric acid for 5, 10, or 15 s. Ground enamel was used as the control group. For the initial bond strength test, 15 specimens per etching group for each adhesive were used. For the shear fatigue test, 20 specimens per etching group for each adhesive were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. Initial shear bond strengths and fatigue shear strengths of composite adhesively bonded to ground and pre-etched enamel were determined. AFM observations of ground and pre-etched enamel were also conducted, and surface roughness as well as surface area were evaluated.

RESULTS

The initial shear bond strengths and fatigue shear strengths of the universal adhesives in the pre-etched groups were significantly higher than those of the control group, and were not influenced by the pre-etching time. Significantly higher surface roughness and surface area of enamel surfaces in pre-etched groups were observed compared with those in the control group. While the surface area was not significantly influenced by etching time, surface roughness of the enamel surfaces in the pre-etched groups significantly increased with pre-etching time.

CONCLUSIONS

The results of this in vitro study suggest that reduced phosphoric acid pre-etching times do not impair the fatigue bond strength of universal adhesives. Although fatigue bond strength and surface area were not influenced by phosphoric-acid etching times, surface roughness increased with increasing etching time.

Catalytic Oxidation of Chlorinated Organics over Lanthanide Perovskites: Effects of Phosphoric Acid Etching and Water Vapor on Chlorine Desorption Behavior

In this article, the underlying effect of phosphoric acid etching and additional water vapor on chlorine desorption behavior over a model catalyst La₃Mn₂O₇ was explored. Acid treatment led to the formation of LaPO₄ and enhanced the mobility of lattice oxygen of La₃Mn₂O₇ evidenced by a range of characterization (i.e., X-ray diffraction, temperature-programmed analyses, NH₃-IR, etc.). The former introduced thermally stable Brönsted acidic sites that enhanced dichloromethane (DCM) hydrolysis while the latter facilitated desorption of accumulated chlorine at elevated temperatures. The acid-modified catalyst displayed a superior catalytic activity in DCM oxidation compared to the untreated sample, which was ascribed to the abundance of proton donors and Mn(IV) species. The addition of water vapor to the reaction favored the formation and desorption of HCl and avoided surface chlorination at low temperatures. This resulted in a further reduction in reaction temperature under humid conditions ( T₉₀ of 380 °C for the modified catalyst). These results provide an in-depth interpretation of chlorine desorption behavior for DCM oxidation, which should aid the future design of industrial catalysts for the durable catalytic combustion of chlorinated organics.

Phosphoric acid purification sludge: Potential in heavy metals and rare earth elements

The present study was carried out to show the potential in heavy metals (HM) and the rare earth elements (REE) which presents the residues of phosphoric-acid(PA) purification. Three different cadmiferous solid residues (according to the nature of the purification process of the PA: BG, BC and BS) were collected from an industrial site located in the south of Tunisia. The mineralogical study showed the predominance of anhydrite, accompanied by quartz, malladrite; calcium sulfate hemihydrate and fluorapophyllite. The microanalysis showed (i) the association of cadmium and zinc, (ii) as well as the presence of associated REEs. The chemical analysis showed that (i) the calcium sulfate concentrations are majority in samples BS, BG and BC (44, 34 and 44%, respectively), (ii) significant concentrations of phosphoric acid (28, 18 and 21% P₂O₅, respectively), (iii) the HM: Cd, Zn, Cr, Ni, V, Cu, Pb, Co, Mo, Mn and U have proportion in the order of 0.1%. The concentrations of Cd, Zn and Cr are respectively in the order of: 230, 149 and 189 mg/kg for BS, 346, 243 and 153 mg/kg for BG and 183, 129 and 440 mg/kg for BC and (iv) the REEs: La, Ce, Nd, Eu, Y et Yb present considerable mass percentages able to reach 0.2%. A series of extraction tests was led on the cadmiferous sludges to evaluate the rates of HM (Cd, Zn) and REE dissolution, using two solvents (deionized water (DW) and aqueous sodium based alkaline metal solution). The results showed that the dissolution rates of Cd and Zn are respectively in the order of (12-29% and 41-45% for DW; 67-86% and 83-93% for Na₂SO₄ solution). The extractability of HM and REE is strongly influenced by pH, solvent nature and mineral load in the cadmiferous sludges. The water-soluble metals represent a significant mobile fraction, making the toxic elements more sensitive to mobilization processes, such as leaching and erosion. Whereas, the metals extractable by the Na₂SO₄ solution represent a very important exchangeable and "co-crystallization" fraction, which reflects the bioavailability of these metals.

Reconsideration of Enamel Etching Protocols for Universal Adhesives: Effect of Etching Method and Etching Time

PURPOSE

To evaluate whether different etching methods with reduced etching times would improve the enamel bonding efficacy of universal adhesives.

MATERIALS AND METHODS

Three enamel etching methods were evaluated - 1. phosphoric acid ester monomer etching (PPM); 2. phosphoric acid etching (PPA); and 3. polyalkenoic acid etching (PLA) - as were three universal adhesives: 1. BeautiBond Universal (BU); 2. Prime&Bond elect (PE); and 3. Scotchbond Universal Adhesive (SU). The shear bond strengths of the universal adhesives to ground enamel and ground enamel etched for 1, 5, 10, and 15 s with different etching methods were determined after 24 h and 10,000 thermal cycles. Surface roughness average (Ra) and surface area ratio (surface area:planar area) were measured using a confocal laser scanning microscope. Field-emission scanning electron microscope (FE-SEM) observations of enamel with different etching protocols were also conducted.

RESULTS

The bond strengths of universal adhesives to enamel subjected to PPA etching with maximum times of 1-15 s and PLA etching for 15 s were significantly higher than those to ground enamel. The bond strength to enamel subjected to PPM etching did not increase and was similar to that for ground enamel. PPA and PLA etching were effective at increasing the Ra and surface area ratio of enamel. Although both values were significantly higher than those of ground enamel, those subjected to PPA etching were significantly higher than those which underwent PLA etching. In addition, the Ra and surface area of enamel subjected to PPM etching were similar to those of ground enamel, regardless of the etching time.

CONCLUSIONS

Phosphoric acid etching for <1-15 s and polyalkenoic-acid etching for 15 s both improve the bonding of universal adhesives, the Ra, and the surface area ratio of enamel. However, phosphoric acid ester monomer etching was not effective, regardless of the etching time.

Bioethanol production from wheat straw by phosphoric acid plus hydrogen peroxide (PHP) pretreatment via simultaneous saccharification and fermentation (SSF) at high solid loadings

Phosphoric acid plus hydrogen peroxide (PHP) pretreatment was employed on wheat straw for ethanol conversion by simultaneous saccharification and fermentation (SSF) at high loadings. Results showed solid loading of PHP-pretreated wheat straw can be greatly promoted to 20%. Although more enzyme input improved ethanol conversion significantly, it still can be potentially reduced to 10-20 mg protein/g cellulose. Increasing yeast input also promoted ethanol conversion, however, the responses were not significant. Response surface method was employed to optimize SSF conditions with the strategy of maximizing ethanol conversion and concentration and minimizing enzyme and yeast input. Results indicated that ethanol conversion of 88.2% and concentration of 69.9 g/L were obtained after 120 h SSF at solid loading of 15.3%, and CTec2 enzyme and yeast were in lower input of 13.2 mg protein/g cellulose and 1.0 g/L, respectively. Consequently, 15.5 g ethanol was harvested from 100 g wheat straw in the optimal conditions.

Surface modification of sludge-derived carbon by phosphoric acid as new electrocatalyst for degradation of acetophenone

Sludge-derived carbons (SCs) were modified by different acids and used as electrocatalyst for electrochemical oxidation degradation of acetophenone. The results showed that SC treated with phosphoric acid (H₃PO₄-SC) exhibited the highest catalytic activity. The degradation efficiency of acetophenone reached 87.0%, and TOC removal was 72.3% under the conditions of 100 mg L^-1 acetophenone, 90 mA cm^-2, and 180 min reaction time. The element content and chemical state of H₃PO₄-SC were measured by XRF, XRD, TGA, FTIR, and Mössbauer spectra, and the results indicated that ferric iron and phosphate on the surface of H₃PO₄-SC might play the main role in acetophenone degradation. The carbonyl-¹³C-labeled acetophenone was first used to investigate the degradation of acetophenone in electrochemical oxidation by NMR.

Role of phosphoric acid in the bioavailability of potentially toxic elements in hydrochars produced by hydrothermal carbonisation of sewage sludge

The effect of phosphoric acid addition to the feed-water on the speciation and transformation behaviour of potentially toxic elements (PTEs) in the hydrothermal carbonisation (HTC) of sewage sludge was explored. Over 70% of each of the PTEs (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn) was in the directly bioavailable and potentially bioavailable fraction in the raw sludge, and especially Cu and Zn at 97.5 and 98.6%, respectively. Through the HTC process the directly bioavailable and potentially bioavailable fractions of PTEs in the sludge hydrochar clearly decreased, and the residual fraction in the hydrochar showed an observable increase. Further stabilisation of PTEs in hydrochar occurred during HTC with the addition of phosphoric acid solution to the feed-water. As the concentration of phosphoric acid in the feed-water increased the percentages of the residual fraction of Cd, Cr, Ni, Pb and Zn in hydrochars each exceeded 80%, but different PTEs behaved differently with increasing phosphate molar ratio in the feed-water. When the molar ratio of phosphate was 15%, the percentages of the residual fractions of Cd, Mn and Zn reached their maximum values in accordance with the changing trend in aromaticity of the hydrochar. Moreover, a large number of phosphate mineral crystals effectively occluded the PTEs in hydrochar. In conclusion, the addition of phosphoric acid to the feed-water during HTC further deactivated PTEs leading to a substantial decline in the potential environmental risk associated with the land application of the sewage sludge.

Phosphoric acid pretreatment enhances the specific surface areas of biochars by generation of micropores

Biochars are being increasingly applied in soil for carbon sequestration, fertility improvement, as well as contamination remediation. Phosphoric acid (H₃PO₄) pretreatment is a method for biochar modification, but the mechanism is not yet fully understood. In this work, biochars and the raw biomass were treated by H₃PO₄ prior to pyrolysis. Due to an acid catalysis and crosslink, the micropores of the pretreated particles were much more than those without H₃PO₄ pretreatment, resulting in the dramatical enhancement of specific surface areas of the pretreated particles. Crystalline cellulose (CL) exhibited a greater advantage in the formation of micropores than of amorphous lignin (LG) with H₃PO₄ modification. The formation mechanisms of micropores were: (a) H⁺ from H₃PO₄ contributes to micropores generation via H⁺ catalysis process; (b) the organic phosphate bridge protected the carbon skeleton from micropore collapse via the crosslinking of phosphate radical. The sorption capacities to carbamazepine (CBZ) and bisphenol A (BPA) increased after H₃PO₄ modification, which is ascribed to the large hydrophobic surface areas and more abundant micropores. Overall, H₃PO₄ pretreatment produced biochars with large surface area and high abundance of porous structures. Furthermore, the H₃PO₄ modified biochars can be applied as high adsorbing material as well as P-rich fertilizer.

Phosphoric Acid Containing Chlorhexidine Compromises Bonding of Universal Adhesive

PURPOSE

To examine the influence of phosphoric acid containing chlorhexidine on the dentin bond stability of a universal and a 2-step etch-and-rinse adhesive.

MATERIALS AND METHODS

Eighty sound bovine incisors were randomly assigned to 8 groups (n = 10) according to: phosphoric acid (37% phosphoric acid [CTR] or 37% phosphoric acid with 2% chlorhexidine [CHX]); adhesive (Scotchbond Universal Adhesive [SBU]or Adper Single Bond 2 [SB2]); and water storage time (24 h and 6 months). Both acids and adhesives were applied to flat dentin surfaces (following manufacturer's instructions) upon which composite cylinders were built up (0.72 mm2). After storage in distilled water at 37°C for 24 h or 6 months, the composite cylinders were submitted to microshear bond strength (µSBS) testing. Bond strength data (MPa) were analyzed using three-way ANOVA and post-hoc Tukey's test (α = 5%).

RESULTS

The interaction among factors was significant (p = 0.012). Both adhesives showed similar 24-h bond strengths regardless of the phosphoric acid. After 6 months, similar values were found for both materials when control phosphoric acid was used, but CHX phosphoric acid produced statistically significantly lower bond strengths for SBU. SB2 bond strength was not affected by acid type.

CONCLUSION

Phosphoric acid containing chlorhexidine induced premature bond strength degradation of Scotchbond Universal Adhesive.

Exposure to organophosphate flame retardants of hotel room attendants in Wuhan City, China

Indoor environments provide sources of exposure to organophosphate flame retardants (PFRs), which are artificially synthesized fire-protecting agents used as additives in interior products. As public spaces, hotels are required to meet stricter fire-precaution criteria. As such, room attendants may be exposed to higher levels of PFRs. Our goal was to characterize the exposure of hotel room attendants to PFRs by measuring metabolites in their urine and the corresponding parent PFRs in dust and hand-wipes collected from 27 hotels located in Wuhan City, China. The exposure of the attendants was found to be omnipresent: urinary metabolites of PFRs, such as DPHP (diphenyl phosphate), BDCIPP (bis(1,3-dichloro-2-propyl) phosphate), and DoCP (di-o-cresyl phosphate) & DpCP (di-p-cresyl phosphate) were detected with high frequency (87%, 79% and 87%, respectively). We observed that metabolites in post-shift urine were consistently present at higher levels than those in the first morning voids (p < 0.05 for BDCIPP and DPHP). Regarding external exposure, 10 PFRs were determined in both dust samples and hand-wipes, with TCIPP (tris(2-chloroisopropyl) phosphate) being the most abundant compound in both matrices. The levels of PFRs in hand-wipes and dust samples were not correlated. PFRs in dust and their corresponding urinary metabolites were not significantly correlated, while a moderate significant correlation of TDCIPP (tris(1,3-dichloro-2-propyl) phosphate) in hand-wipes and its urinary metabolite, BDCIPP, was observed in both morning void samples (p = 0.01) and post-shift urine (p = 0.002). Moreover, we found that participants from high-rise buildings (defined as > 7 stories) had significantly higher BDCIPP and DPHP concentrations than those from low-rise buildings. A possible reason is that high-rise buildings may use high-grade fireproof building materials to meet stricter fire restrictions. Overall, these results indicate that PFRs exposure in hotels is a contributor to the personal exposure of hotel room attendants.

Phosphoric acid based pretreatment of switchgrass and fermentation of entire slurry to ethanol using a simplified process

Switchgrass (Alamo) was pretreated with phosphoric acid (0.75 and 1%, w/w) at three temperatures (160, 175 and 190 °C) and time (5, 7.5 and 10 min) using a steam gun. The slurry after pretreatment was liquefied by enzymes and the released sugars were fermented in a simultaneous saccharification and co-fermentation process to ethanol using ethanologenic Escherichia coli strain SL100. Among the three variables in pretreatment, temperature and time were critical in supporting ethanol titer and yield. Enzyme hydrolysis significantly increased the concentration of furans in slurries, apparently due to release of furans bound to the solids. The highest ethanol titer of 21.2 ± 0.3 g/L ethanol obtained at the pretreatment condition of 190-1-7.5 (temperature-acid concentration-time) and 10% solids loading accounted for 190 ± 2.9 g ethanol/kg of raw switch grass. This converts to 61.7 gallons of ethanol per ton of dry switchgrass, a value that is comparable to other published pretreatment conditions.

Vibrational Dynamics and Couplings of the Hydrated RNA Backbone: A Two-Dimensional Infrared Study

The equilibrium structure of the RNA sugar-phosphate backbone and its hydration shell is distinctly different from hydrated DNA. Applying femtosecond two-dimensional infrared (2D-IR) spectroscopy in a range from 950 to 1300 cm^-1, we elucidate the character, dynamics, and couplings of backbone modes of a double-stranded RNA A-helix geometry in its aqueous environment. The 2D-IR spectra display a greater number of backbone modes than for DNA, with distinctly different lineshapes of diagonal peaks. Phosphate-ribose interactions and local hydration structures are reflected in the complex coupling pattern of RNA modes. Interactions with the fluctuating water shell give rise to spectral diffusion on a 300 fs time scale, leading to a quasi-homogeneous line shape of the symmetric (PO₂)^- stretching mode of the strongly hydrated phosphate groups. The RNA results are benchmarked by 2D-IR spectra of DNA oligomers in water and analyzed by molecular dynamics and quantum mechanical molecular mechanics simulations.

Biosorption of chromium(VI) in aqueous solutions by chemically modified Strychnine tree fruit shell

Chromium(VI) was removed from aqueous solution using sulfuric- and phosphoric-acid-activated Strychnine tree fruit shells (SSTFS and PSTFS) as biosorbents. Effects of various parameters such as adsorbent dose (0.02-0.1 g/L), temperature (303-333 K), agitation speed, solution pH (2-9), contact time, and initial Cr(VI) concentration (50-250 mg/L) were studied for a batch adsorption system. The optimum pH range for Cr(VI) adsorption was determined as 2. Equilibrium adsorption data were analyzed with isotherm models and the Langmuir and Freundlich models got best fitted values for SSTFS (R² value - 0.994) and PSTFS (R² value - 0.996), respectively. The maximum adsorption capacities of SSTFS and PSTFS were 100 and 142.85 mg/g, respectively. The biosorption process was well explained by pseudo-second-order kinetic model with higher R² value (SSTFS - 0.996, PSTFS - 0.990) for both biosorbents. Characterization of biosorbents was done using Fourier transform infrared spectroscopy, scanning electron microscopy, elemental analysis, energy-dispersive X-ray analysis, and thermogravimetric analysis. Thermodynamic studies revealed the spontaneous, endothermic, and randomness in nature of the Cr(VI) adsorption process. Different concentrations of NaOH solutions were used to perform the desorption studies. The results demonstrated that both SSTFS and PSTFS can be used as an effective and low-cost biosorbent for removal of Cr(VI) from aqueous solutions.

Intricate Estimation and Assessment of Surface Conditioning of Posts to improve Interfacial Adhesion in Post-core Restorations: An in vitro Study

INTRODUCTION

Post and core restorations are routinely used for restoring grossly decayed tooth structures. Various chemical agents are known to affect the interfacial adhesions between the post and the core. Hence, we planned the present study to evaluate the effect of various post-surface treatments on the interfacial strength between the posts and composite materials that are used for building up the core portion.

MATERIALS AND METHODS

The present study included assessment of the effect of surface conditioning of posts on the interfacial adhesion in post-core restorations. A total of 80 clear post-tapers were included and were divided broadly into four study groups based on the type of chemical testing protocols used. Various chemical treatments included alkaline potassium permanganate, hydrogen peroxide, and phosphoric acid. The fourth group was the control group. The composite core material was used for building up the core. Testing of the tensile load was done on a universal testing machine. All the results were analyzed by the Statistical Package for the Social Sciences (SPSS) software.

RESULTS

The highest bond strength was observed in the study group treated with alkaline potassium permanganate, while the lowest was observed in the control group followed by the hydrogen peroxide group. While comparing the mean bond strength in between various study groups, significant results were obtained.

CONCLUSION

Chemical treatment protocol significantly alters the mean bond strength of the post and core restoration.

CLINICAL SIGNIFICANCE

Potassium permanganate significantly increases the bond strength between the fiber post and core restoration.

Current-use flame retardants: Maternal exposure and neurodevelopment in children of the CHAMACOS cohort

Flame retardants are commonly used in consumer products found in U.S. households. Restrictions on the use of polybrominated diphenyl ether flame retardants have resulted in increased use of replacement chemicals, including Firemaster 550^® (FM 550^®) and organophosphate flame retardants (PFRs): tris(1,3- dichloro-2-propyl) phosphate (TDCIPP); tris(chloropropyl) phosphate (TCIPP); tris(2-chloroethyl) phosphate (TCEP); and triphenyl phosphate (TPHP). Animal research suggests that PFRs may affect neurodevelopment through noncholinergic mechanisms similar to some organophosphate (OP) pesticides. Despite the widespread presence of these compounds in home environments, and their structural similarity to neurotoxic OP pesticides, understanding of human exposure and health effects of PFRs is limited. We measured four urinary PFR metabolites from pregnant women in the CHAMACOS birth cohort study (n = 310) and assessed neurodevelopment of their children at age 7. Metabolites of TDCIPP (BDCIPP: bis(1,3-dichloro-2-propyl) phosphate) and TPHP (DPHP: diphenyl phosphate) were detected in >75% of urine samples, and isopropylphenyl phenyl phosphate (ip-PPP), a metabolite of one component of FM 550^®, was detected in 72% of urine samples. We observed decreases of 2.9 points (95% Confidence Interval (CI): -6.3, 0.5) and 3.9 points (95% CI: -7.3,-0.5) in Full-Scale intelligence quotient and Working Memory, respectively, for each ten-fold increase in DPHP in adjusted regression models (n = 248). Decreases in Full-Scale IQ and Working Memory were greater in models of the molar sum of the PFR metabolites compared to the DPHP models. This is the first study to examine PFR and FM 550^® exposures and potential neurodevelopmental outcomes in pregnant women and children. Additional research is warranted.

Interrelationships among hydrogen permeation, physiochemical properties and early adsorption abilities of titanium

This study aimed to investigate if the titanium samples with low hydrogen permeation which treated with a novel etching combination: phosphoric acid and sodium fluoride could influence the surface physiochemical properties and early adsorption ability. Titanium samples were treated with three different concentrations of the new formula, as groups A, B and C, and treated with the traditional etching formula, as group T. Zeta potential, contact angle, X-ray photoelectron spectroscopy (XPS) and fibronectin (FN)/vitronectin (VN) adsorption of Sprague-Dawley (SD) rat tibial osteotomies in the initial 30min and MG-63 adsorption in the initial 24 h were detected. Basing on the results of trails and pearson correlation analysis, the low hydrogen permeation into titanium didn't exert an impact on the surface morphology and surface stability. The adsorptions of F, P, S, acid hydroxyl and basic hydroxyl on the surfaces brought no bear on them as well. Surface concave depth and surface skewness showed highly positive correlation and moderate negative correlation with adsorption ability, respectively. Therefore, the surface morphology of titanium treated with the novel etching formula plays the only and primary role on the early adsorption. Because of its specific surface topography, group C showed the best performance which possessed slightly superiority than those of group B and group T, and with the lowest being group A. The low hydrogen permeation into titanium substrate was just benefit for improving the titanium mechanical properties, but not for the surface biochemical traits.

Pretreating wheat straw by phosphoric acid plus hydrogen peroxide for enzymatic saccharification and ethanol production at high solid loading

Wheat straw was pretreated by phosphoric acid plus hydrogen peroxide (PHP) for enzymatic hydrolysis and ethanol fermentation at high solid loadings. Results indicated solid loading could reach 20% with 77.4% cellulose-glucose conversion and glucose concentration of 164.9g/L in hydrolysate, it even was promoted to 25% with only 3.4% decrease on cellulose-glucose conversion as the pretreated-wheat straw was dewatered by air-drying. 72.9% cellulose-glucose conversion still was achieved as the minimized enzyme input of 20mg protein/g cellulose was employed for hydrolysis at 20% solid loading. In the corresponding conditions, 100g wheat straw can yield 11.2g ethanol with concentration of 71.2g/L by simultaneous saccharification and fermentation. Thus, PHP-pretreatment benefitted the glucose or ethanol yield at high solid loadings with lower enzyme input. Additionally, decreases on the maximal cellulase adsorption and the direct-orange/direct-blue indicated drying the PHP-pretreated substrates negatively affected the hydrolysis due to the shrinkage of cellulase-size-accommodable pores.

Evaluation of efficient glucose release using sodium hydroxide and phosphoric acid as pretreating agents from the biomass of Sesbania grandiflora (L.) Pers.: A fast growing tree legume

Sesbania grandiflora (L.) Pers. is one of the fast growing tree legumes having the efficiency to produce around 50tha^-1 above ground dry matters in a year. In this study, biomass of 2years old S. grandiflora was selected for the chemical composition, pretreatments and enzymatic hydrolysis studies. The stem biomass with a wood density of 3.89±0.01gmcm^-3 contains about 38% cellulose, 12% hemicellulose and 28% lignin. Enzymatic hydrolysis of pretreated biomass revealed that phosphoric acid (H₃PO₄) pretreated samples even at lower cellulase loadings [1 Filter Paper Units (FPU)], could efficiently convert about 86% glucose, while, even at higher cellulase loadings (60FPU) alkali pretreated biomass could convert only about 58% glucose. The effectiveness of phosphoric acid pretreatment was also supported by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR) analysis.

Study of ciprofloxacin adsorption and regeneration of activated carbon prepared from Enteromorpha prolifera impregnated with H3PO4 and sodium benzenesulfonate

Activated carbons were derived from Enteromorpha prolifera immersed in H₃PO₄ solution or the H₃PO₄ solution mixed with sodium benzenesulfonate (SBS), producing AC and AC-SBS. NaOH solution was employed in regeneration of ciprofloxacin (CIP)-loaded AC and AC-SBS to obtain RAC and RAC-SBS. The properties of the original and regenerated activated carbons were characterized by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), N₂ adsorption/desorption isotherms and Fourier transform infrared spectroscopy (FTIR). Batched adsorption studies were carried out to compare CIP adsorption behaviors of the four carbons. The results suggested that the four samples exhibited higher proportions of mesopores and similar functional groups. Although AC displayed much higher specific surface area (S_BET) (1045.79m²/g) than AC-SBS (738.03m²/g), its CIP adsorption capacity was much less than AC-SBS. The maximum adsorption capacity for AC, AC-SBS, RAC and RAC-SBS were found to be 250mg/g, 286mg/g, 233mg/g and 256mg/g, respectively, with the isotherms adhering to Langmuir isotherm model. The electrostatic attraction and cation exchange between CIP and the four carbons were the dominant adsorption mechanisms. Moreover, the thermodynamic parameters represented that the adsorption process had been confirmed to be a spontaneous and endothermic reaction.