Preparation and characterization of a novel polyethyleneimine cation-modified persimmon tannin bioadsorbent for anionic dye adsorption

Adsorption Characteristics of Organic Pollutants on Montmorillonites Modified by Quaternary Ammonium Surfactants with Organic Counterions

Na-montmorillonite (Na-Mt) modified by quaternary ammonium surfactants containing different organic counterions [OMt-QAS·Y-, Y = CH3CO3 -, CH3 (CH2)3COO-, CH3CH(OH)COO-, and HCOO-] was prepared for enhancing the adsorption capacity of 2, 4-dichlorophenol/cibacron brilliant yellow 3G-P. Compared with Na-Mt, whose adsorption efficiency for 2,4-dichlorophenol/cibacron brilliant yellow 3G-P was only 58/1.85 mg/g, the adsorption efficiency of OMt-QAS·Y- was greatly improved, with OMt-QAS·CH3CO3 - having the highest adsorption capacity of 152.85/116.17 mg/g. The kinetic and isotherm studies indicate that all adsorption processes fit well to the pseudo-second-order model and Freundlich model, respectively. The hydrophobicity of counterions and their affinity with the aliphatic chains had an effect on the interlayer spacing and point of zero charge of OMt-QAS·Y-, which in turn affected their adsorption properties.

A polyethyleneimine-coated thermally-oxidized graphitic-carbon nitride adsorbent for the removal of organic pollutants

Negatively charged organic pollutants in water are responsible for a large range of public health and ecological issues. Low-cost and low-toxicity graphitic carbon nitride (CN), with its abundant functional groups and surface defects, is a promising material for the removal of organic molecules by adsorption. However, basic synthesis methods for CN often result in a material with morphology and electric charge that are suboptimal for interacting with negatively charged pollutants. Here, an adsorbent was prepared by thermally oxidizing a tubular CN precursor and then coating the resulting flake-shaped material (FCNO) with the polycationic polymer polyethyleneimine (PEI). The resulting adsorbent, FCNO550-PEI, removed humic acid (HA), a widespread problematic organic molecule, as well as the common toxic anionic dye Congo red (CR). FCNO550-PEI was superior to other CN-based adsorbents previously reported in the literature with maximum adsorption capacities according to the Sips isotherm model for HA and CR of 437.1 mg/g and 1430.3 mg/g, respectively. In addition, FCNO550-PEI could adsorb HA and CR from different types of water and was reusable. Besides electrostatic interactions and hydrogen bonds between PEI and the pollutants, HA and CR adsorption was enabled by π-π interactions with the FCNO support itself. The high efficiency of FCNO550-PEI for the removal of HA and CR highlights its potential for water treatment applications.

Hollow Biomass Adsorbent Derived from Platanus Officinalis Grafted with Polydopamine-Mediated Polyethyleneimine for the Removal of Eriochrome Black T from Water

Platanus officinalis fibers (PFs) taking advantage of high-availability, eco-friendly and low-cost characteristics have attracted significant focus in the field of biomaterial application. Polyethyleneimine grafted with polydopamine on magnetic Platanus officinalis fibers (PEI-PDA@M-PFs) were prepared through a two-step process of mussel inspiration and the Michael addition reaction, which can work as an effective multifunctional biomass adsorbent for anionic dye with outstanding separation capacity and efficiency. The as-prepared PEI-PDA@M-PFs possess desirable hydrophilicity, magnetism and positive charge, along with abundant amino functional groups on the surface, facilitating efficient adsorption and the removal of Eriochrome Black T (EBT) dyes from water. In addition to the formation mechanism, the adsorption properties, including adsorption isotherms, kinetics, and the reusability of the absorbent, were studied intensively. The as-prepared PEI-PDA@M-PFs achieved a theoretical maximum adsorption capacity of 166.11 mg/g under optimal conditions (pH 7.0), with 10 mg of the adsorbent introduced into the EBT solution. The pseudo-second-order kinetic and Langmuir models were well matched with experimental data. Moreover, thermodynamic data ΔH > 0 revealed homogeneous chemical adsorption with a heat-absorption reaction. The adsorbent remained at high stability and recyclability even after five cycles of EBT adsorption processes. These above findings provide new insights into the adsorption processes and the development of biologic material for sustainable applications.

Improved Adsorption of Organic Dyes onto a Polypyrrole/Tannic Acid Nanocomposite

Methyl orange (MO) and methylene blue (MB) dyes are toxic and carcinogenic; thus, their presence in water bodies has been a major concern. Designing an efficient adsorbent for removal of these dyes is a scientific challenge for researchers. In this work, a polypyrrole-tannic acid nanocomposite was prepared via a chemical oxidation method and used as a novel adsorbent for removing these toxic dyes. The synthesized nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller methods. The effect of different parameters on adsorption such as adsorbent doses, temperature, pH, initial dye concentration, and contact time was studied. The adsorption was in line with pseudo-second-order kinetics and the Langmuir isotherm model. ΔG°, ΔH°, and ΔS° were calculated to ascertain the feasibility of adsorption. The maximum adsorption capacities attained for this adsorbent were found to be 204.08 mg/g toward the MO dye and 217.39 mg/g toward the MB dye.

Phosphorylating Tannin in Urea System: A Simple Approach for Enhanced Methylene Blue Removal from Aqueous Media

Tannin, after lignin, is one of the most abundant sources of natural aromatic biomolecules. It has been used and chemically modified during the past few decades to create novel biobased materials. This work intended to functionalize for the first time quebracho Tannin (T) through a simple phosphorylation process in a urea system. The phosphorylation of tannin was studied by Fourier transform infrared spectroscopy (FTIR), NMR, inductively coupled plasma optical emission spectroscopy (ICP-OES), and X-ray fluorescence spectrometry (XRF), while further characterization was performed by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and thermogravimetric analysis (TGA) to investigate the morphology, composition, structure, and thermal degradation of the phosphorylated material. Results indicated the occurrence of phosphorylation, suggesting the insertion of phosphate-containing groups into the tannin structure, revealing a high content of phosphate for modified tannin (PT). This elevated phosphorus content serves as evidence for the successful incorporation of phosphate groups through the functionalization process. The corresponding PT and T were employed as adsorbents for methylene blue (MB) removal from aqueous solutions. The results revealed that the Langmuir isotherm model effectively represents the adsorption isotherms. Additionally, the pseudo-second-order model indicates that chemisorption predominantly controls the adsorption mechanism. This finding also supports the fact that the introduced phosphate groups via the phosphorylation process significantly contributed to the improved adsorption capacity. Under neutral pH conditions and at room temperature, the material achieved an impressive adsorption capacity of 339.26 mg·g-1 in about 2 h.

One-Step Synthesis of Polyethyleneimine-Grafted Styrene-Maleic Anhydride Copolymer Adsorbents for Effective Adsorption of Anionic Dyes

Wastewater containing organic dyes has become one of the important challenges in water treatment due to its high salt content and resistance to natural degradation. In this work, a novelty adsorbent, PEI-SMA, was prepared by grafting polyethyleneimine (PEI) onto styrene-maleic anhydride copolymer (SMA) through an amidation reaction. The various factors, such as pH, adsorbent dosage, contact time, dye concentration, and temperature, which may affect the adsorption of PEI-SMA for Reactive Black 5 (RB5), were systematically investigated by static adsorption experiments. The adsorption process of PEI-SMA for RB5 was more consistent with the Langmuir isotherm model and the pseudo-second-order model, suggesting a single-layer chemisorption. PEI-SMA exhibits excellent adsorption performance for RB5 dye, with a maximum adsorption capacity of 1749.19 mg g-1 at pH = 2. Additionally, PEI-SMA exhibited highly efficient RB5 competitive adsorption against coexisting Cl- and SO42- ions and cationic dyes. The adsorption mechanism was explored, and it can be explained as the synergistic effect of electrostatic interaction, hydrogen bonding and π-π interaction. This study demonstrates that PEI-SMA could act as a high performance and promising candidate for the effective adsorption of anionic dyes from aqueous solutions.

Novel soy protein isolate/sodium alginate-based functional aerogel for efficient uptake of organic dye from effluents

In response to the increasing global concern regarding water pollution, there is a growing demand for the development of novel adsorbents capable of effectively eliminating hazardous organic pollutants from effluents. In this study, we present a functional soy protein isolate (SPI)/sodium alginate (ALG)/polyethyleneimine (PEI) aerogel prepared via a facile chemical crosslinking process as a novel adsorbent with excellent capabilities for removing toxic methyl blue (MB) dye from effluents. Thanks to the synergistic dense oxygen and nitrogen-containing functional groups in the networks, the ALG/SPI/PEI (ASP) aerogel displayed high adsorption capacity for MB (106.3 mg/g) complying the adsorption kinetics and isotherm with the pseudo-second-order and Langmuir models, respectively. Remarkably, the MB adsorption capability of the ASP aerogel surpasses that of its pristine counterpart and outperforms recently reported adsorbents. Moreover, the aerogel maintained >80% of initial adsorption capability in the fourth regenerative cycle, indicating excellent reusability. The superior MB adsorbability coupled with high-efficiency regenerability in this study reveal the significant potential of ASP aerogel in efficiently eliminating organic dye from wastewater.

Adsorption Behavior and Kinetics of 1,4-Dioxane by Carbon Aerogel

1,4-dioxane is a potential carcinogen in water and is difficult to deal with due to its robust cycloether bond and complete miscibility with water. To remove 1,4-dioxane in an economically viable and environmentally friendly way, a series of carbon aerogels were synthesized as adsorbents for 1,4-dioxane. The experiment results showed that adsorption performances were closely related to the preparation conditions of carbon aerogels, such as the molar ratio, heating rate, pyrolysis temperature and residence time, which were carefully controlled. Scanning electron microscope analysis revealed the presence of a three-dimensional porous network structure in carbon aerogels. Brunauer-Emmett-Teller analysis results demonstrated an increase in specific surface area (673.89 m2/g) and total pore volume after carbonization, with an increase in mesoporous porosity and a decrease in microporosity. When considering each variable individually, the highest specific surface area of prepared carbon aerogels was achieved at a pyrolysis temperature of 800 °C, a holding time of 1 h, and a heating rate of 2 °C/min. Under optimal experimental conditions, the adsorption removal of 1,4-dioxane by carbon aerogels exceeded 95%, following quasi-second-order kinetics and Langmuir isothermal adsorption isotherms, indicating that monolayer adsorption on the surface of carbon aerogels occurred. The maximum adsorption capacity obtained was 67.28 mg/g at a temperature of 318 K, which was attributed to the presence of a large proportion of mesopores and abundant micropores simultaneously in carbon aerogels. Furthermore, with the interference of chlorinated solvents such as trichloroethylene (TCE), the removal efficiency of 1,4-dioxane had no obvious inhibition effect. Regeneration experiments showed that after five continuous cycles, the carbon aerogels still kept a comparable adsorption capacity, which illustrates its potential application in 1,4-dioxane-polluted water purification.

Gemini Quaternary Ammonium Surfactants with Different Counterions-modified Montmorillonite for Efficient Removal of Methyl Orange

Organic Na-montmorillonite (OMt-12-2-12·2Y - , Y=CH 3 CO 3 - , C 6 H 5 COO - and Br - ) modified by a series of Gemini quaternary ammonium surfactants with different counterions was prepared for enhancing the adsorption capacity of methyl orange. Compared with the initial adsorption capacity of 5.251 mg/g of Na-Mt, the adsorption effect of OMts under the optimal conditions increased by about 31~34 times. The adsorption isotherms and kinetics of all adsorption processes were respectively described by Langmuir and pseudo-second-order models. The structure, hydrophobicity and hydration of the counterions, as well as the affinity of the counterions with the long aliphatic chains, had a certain influence on the adsorption performance of OMts for methyl orange.

Effective removal of malachite green from local dyeing wastewater using zinc-tungstate based materials

The frequent use of an industrial dye such as malachite green (MG) has caused major water body deterioration and is one of the most pressing global challenges, demanding effective treatment techniques. To solve these issues, a simplistic method was developed to synthesize zinc-tungstate (ZnWO4) nanoparticles and also dope the surface matrix of the ZnWO4 nanoparticles using nonmetals of boron (B), carbon (C), and nitrogen (N) at different ratios for enhanced MG removal from wastewater. The prepared nanomaterials were characterized by different methods for crystal structure composition, surface properties, surface morphology, microstructures, functional groups, and elemental oxidation states. The BET analysis revealed a mesoporous structure with surface areas of 30.740 m2/g for ZnWO4, 38.513 m2/g for ZnWO4@BCN, 37.368 m2/g for ZnWO4@BCN/B, 39.325 m2/g for ZnWO4@BCN/C, and 45.436 m2/g for ZnWO4@BCN/N nanocomposites. The best removal of MG was accomplished at pH (8), contact period (50 min), nanoadsorbent dose (0.8 g/L), initial MG concentration (20 mg/L), and temperature (303 K). The maximum adsorption capacities of ZnWO4 and ZnWO4@BCN/N towards MG were 218.645 and 251.758 mg/g, respectively. At equilibrium, the Freundlich isotherm and pseudo-second-order kinetic models were the best fits for the experimental data of MG adsorption on both nanoadsorbents. After eight cycles of adsorption and desorption, both ZnWO4 and ZnWO4@BCN/N were found to be good at removing MG, with efficiencies of 71.00 and 74.20%, respectively. Thermodynamic investigations further validated the spontaneity and endothermic nature of the adsorption process. All study findings confirm the nanoadsorbents exceptional capability and economic feasibility for removing MG dye.

Versatile CO2-responsive Sponges Decorated with ZIF-8 for Bidirectional Separation of Oil/Water and Controllable Removal of Dyes

The complex wastewater containing water-soluble dyes and water-insoluble oils has given rise to significant environmental concerns that demand urgent remediation. Herein, a novel "smart" multifunctional sponge (ZIF-8@PMS) stepwise decorated with ZIF-8 nanoparticles and CO2-responsive copolymer (poly(2-(diethylamino) ethyl methacrylate-co-3-(trimethoxysilyl)propyl acrylate-co-stearyl methacrylate) was successfully prepared for CO2 controllable oil/water separation and dyes removal. The results revealed that the sponge coated with CO2-responsive copolymer for three cycles (ZIF-8@PMS-3) exhibited optimal comprehensive properties. The ZIF-8@PMS-3 had excellent compressive-resilient characteristics and chemical stability. As expected, it displayed tunable wettability and charged state under the regulation of CO2. Based on these features, ZIF-8@PMS-3 presented highly efficient removal of oil and dyes, even for the dye-containing oil/water emulsions, via a synergistic combination of adsorption and separation methods. The adsorption capacity for oil and various organic solvents ranged from 21.3 to 50 g g-1. The maximum adsorption capacities toward anionic dyes: methyl orange with 1205.89 mg g-1 and methyl blue with 880.00 mg g-1 in the presence of CO2 through electrostatic interaction. In the absence of CO2, it achieved maximum adsorption capacities for cationic dyes, including malachite green with 1246.15 mg g-1 and rhodamine B with 203 mg g-1, primarily driven by π-π interactions. According to distinct adsorption mechanisms, ZIF-8@PMS-3 could selectively adsorb either anionic or cationic dyes by exploiting CO2 as a trigger. Furthermore, the separation efficiencies for both types of oil/water emulsions surpassed 99.9%, with respective fluxes of 1566.99 L m-2 h-1 (water-in-oil emulsion) and 310.37 L m-2 h-1 (oil-in-water emulsion). Additionally, the as-prepared sponges exhibited remarkable antibacterial properties and exceptional recyclability. Therefore, the ZIF-8@PMS-3 holds substantial promise for potential applications in practical industrial wastewater treatment.

Activity and potential mechanisms of action of persimmon tannins according to their structures: A review

One distinguishing feature of the persimmon, that differentiates it from other fruits, is its high proanthocyanidins content, known as persimmon tannin (PT). Despite the poor absorption of PT in the small intestine, results from animal studies demonstrate that PT has many health benefits. Our goal in this review is to summarize the literature that elucidates the relationship between PT structure and activity. In addition, we also summarize the potential mechanisms underlying the health benefits that result from PT consumption; this includes the hypolipidemic, hypoglycemic, antioxidant, anti-inflammatory, antiradiation, antibacterial and antiviral, detoxification effects on snake venom, and the absorption of heavy metals and dyes. Studies show that PT is a structurally distinct proanthocyanidins that exhibits a high degree of polymerization. It is galloylation-rich and possesses unique A-type interflavan linkages in addition to the more common B-type interflavan bonds. Thus, PT is converted into oligomeric proanthocyanidins by depolymerization strategies, including the nucleophilic substitution reaction, acid hydrolysis, and hydrogenolysis. In addition, multiple health benefits exerted by PT mainly involve the inactivation of lipogenic and intracellular inflammatory signaling pathways, activation of the fatty acid oxidation signaling pathway, regulation of gut microbiota, and highly absorptive properties.

Organo-Montmorillonite Modified by Gemini Quaternary Ammonium Surfactants with Different Counterions for Adsorption toward Phenol

The discharge of industrial phenol pollutants causes great harm to the natural environment and human health. In this study, phenol removal from water was studied via the adsorption of Na-montmorillonite (Na-Mt) modified by a series of Gemini quaternary ammonium surfactants with different counterions [(C₁₁H₂₃CONH(CH₂)₂N⁺ (CH₃)₂(CH₂)₂ N⁺(CH₃)₂ (CH₂)₂NHCOC₁₁H₂₃·2Y^-, Y = CH₃CO₃^-, C₆H₅COO^- and Br^-, 12-2-12·2Y^-]. The results of the phenol adsorption indicated that MMt-12-2-12·2Br^-, MMt-12-2-12·2CH₃CO₃^- and MMt-12-2-12·2C₆H₅COO^- reached the optimum adsorption capacity, which was 115.110 mg/g, 100.834 mg/g and 99.985 mg/g, respectively, under the conditions of the saturated intercalation concentration at 2.0 times that of the cation exchange capacity (CEC) of the original Na-Mt, 0.04 g of adsorbent and a pH = 10. The adsorption kinetics of all adsorption processes were in good agreement with the pseudo-second-order kinetics model, and the adsorption isotherm was better modeled by Freundlich isotherm. Thermodynamic parameters revealed that the adsorption of phenol was a physical, spontaneous and exothermic process. The results also showed that the counterions of the surfactant had a certain influence on the adsorption performance of MMt for phenol, especially the rigid structure, hydrophobicity, and hydration of the counterions.

Noval green sodium alginate/gellan gum aerogel with 3D hierarchical porous structure for highly efficient and selective removal of Congo red from water

Rational design of adsorbed materials with three-dimensional (3D) hierarchical porous structure, sustainable, high adsorption capacity, and excellent selective is of great significance in practical applications. Herein, a novel aerogel adsorbed material with 3D hierarchical porous architecture was fabricated by employing naturally abundant sodium alginate (SA)/gellan gum (GG) as basic construction blocks to achieve sustainability as well as applying polyethyleneimine (PEI) as functional material for highly efficient and selective capture of Congo red (CR). The aerogel sorbent exhibited strong microstructure, numerous active adsorption sites and being ultralight. The resulting aerogel adsorbent showed high adsorption capacity (3017.23 mg/g) toward CR, exceedingly most previously reported sorbents. Furthermore, the aerogel adsorbent was accompanied by outstanding selectivity for CR in four binary dye systems. Meanwhile, after 3 cycles, the adsorption capacity decreased by 14.8 %, but still maintained the adsorption capacity of 559.79 mg/g. Therefore, excellent adsorption performance, and superb selectivity prefigures its great prospects for wastewater purification.

Parametric Study of Methyl Orange Removal Using Metal–Organic Frameworks Based on Factorial Experimental Design Analysis

Wastewater treatment plants (WWTPs) are one of the most energy-intensive industries. Every stage of wastewater treatment consumes energy, which is the primary contributor to WWTP costs. Adsorbents and process optimization are critical for energy savings. The removal of dyes from industrial wastewater by adsorption using commercially available adsorbents is inefficient. Metal–organic frameworks (MOFs) have outstanding properties that can improve separation performance over current commercial adsorbents, and thus, these materials represent a milestone in improving dye removal in water treatment methods. In this work, three types of metal–organic frameworks (Fe-BTC, Cu-BTC, and ZIF-8) have been investigated as prospective adsorbents for methyl orange removal from water in batch setups. The results showed that at 15 mg/L MO initial concentration and 100 mg dosage, Fe-BTC had the highest removal efficiency of 91%, followed by ZIF-8 (63%), and finally Cu-BTC (35%), which exhibited structural damage due to its instability in water. Fe-BTC maintained consistent adsorption capacity over a wide range of pH values. Furthermore, a 23 full factorial design analysis was implemented to evaluate the conditions for maximum MO-removal efficiency. The main effects, interaction effects, analysis of variance (ANOVA), and the Pareto chart were reported. The statistical analysis demonstrated that the MOF type was the most significant factor, followed by dosage and initial concentration. The analysis indicated that the type of MOF and dosage had a positive effect on the removal efficiency, while the initial concentration had a negative effect. The two-way and three-way interactions were also found to be significant.

Selective adsorption of anionic dye from wastewater using polyethyleneimine based macroporous sponge: Batch and continuous studies

Dyes are well known for their hazardous impacts on public health and the environment. Dye removal using monolithic adsorbents is an attractive approach for industrial applications and process design owing to their utilization in both static and dynamic adsorption experiments. In the present work, polyethyleneimine (PEI) based macroporous monolithic sponge (S₁₀₀) was engineered by ice-templating method and used as an adsorbent. Both batch and continuous operations for dye removal were studied. The effect of various parameters such as pH, adsorbent amount, flow rate, influent dye concentration, and adsorbent bed height on adsorption performance of S₁₀₀ was studied and modelled using Langmuir/Freundlich isotherms for static operations and Adam-Bohart/Thomas model in packed-bed column experiments. Under optimum conditions, the adsorbent showed a remarkably higher adsorption capacity towards CR (1666.67 mg/g), which is considerably higher than most PEI-based adsorbents. Amine groups in S₁₀₀ offered exceptional selectivity for anionic Congo red (CR) against cationic Methylene blue (MB) dye (separation factor of 208 and 87 in absence and presence of sodium chloride, respectively). It can be easily regenerated in alkaline medium without a significant loss in percent adsorption capacity and shows good thermal and mechanical stability. Notably, in column studies, a relatively smaller percentage of unused bed height (32.3%) was observed with higher dye uptake for 16 mg S₁₀₀ at flow rate 10 mL/h and inlet concentration 300 mg/L. Thus, the adsorbent displays an outstanding physiochemical characteristic, excellent selectivity for anionic dye, ease of regeneration and high adsorption performance in both batch and continuous studies.

Highly efficient and selective adsorption of heavy metal ions by hydrazide-modified sodium alginate

In the present study, a new potential adsorbent for the separation and removal of heavy metal ions was prepared using hydrazide modification. Characterization of structural and chemical properties of the absorbent indicated the dialdehyde sodium alginate (DSA) grafted adipic acid dihydrazide (AAD) plays a crucial role. The adsorption process correlated well with Freundlich isotherm and pseudo-second-order kinetics models. Additionally, the adsorption capacities for Hg²⁺, Pb²⁺, Cd²⁺, and Cu²⁺ were 7.833, 2.036, 4.766, and 3.937 mmol g^-1, respectively. The thermodynamic parameter for the sorption demonstrated the process is endothermic and spontaneous. FT-IR and XPS analysis revealed the combination of chelation interactions and ion exchange between nitrogen, oxygen atoms and heavy metal ions. Moreover, after 10 times adsorption-desorption recycles, the adsorption efficiency of the adsorbent was slightly decreased. In conclusion, the as-prepared adsorbent has great potential in practical water pollution purification.

Effective removal of metal ions and cationic dyes from aqueous solution using different hydrazine-dopamine modified sodium alginate

In this paper, DSA-AAD-DA and DSA-TPDH-DA were prepared to effectively remove metal ions and cationic dyes from aqueous solution. The hydrazone structure was prepared by hydrazide-modified SA which captured metal ions selectively, and the remaining functional groups were used as active adsorption sites for cationic dyes. The thermodynamic parameter for the sorption demonstrated the process is endothermic and spontaneous. In single process, the adsorption of metal ions by DSA-AAD-DA and DSA-TPDH-DA correlated well with the Freundlich model through the hydrazone structure coordination and ion exchange which was mainly chemical adsorption, and cationic dyes adsorption correlated well with the Langmuir model which was shown monolayer adsorption was dominant by hydrogen bonding, electrostatic interaction, and π-π interaction. In binary system, the mixed adsorption shown significant antagonism effect in high concentration, but cationic dyes and metal ions in low concentration were efficiently and simultaneously removed, the adsorption ability of DSA-TPDH-DA was much better than DSA-AAD-DA. Moreover, adsorption efficiency can still maintain more than 80% after five times adsorption-desorption recycle. Therefore, DSA-AAD-DA and DSA-TPDH-DA possessed great potential for wastewater treatment.

A high-performance polymer hydrogel derived from konjac flying powder for removal of heavy metals

Agricultural byproducts have excellent potential for pollutant remediation due to the low-cost and environmental sustainability.

Synthesis of green magnetic biopolymer derived from Oak fruit hull tannin for efficient simultaneous adsorption of a mixture of Malachite Green and Sunset Yellow dyes from aqueous solutions

In the present study, a new bioadsorbent with polyhydroxyphenyl groups was synthesized as a tannin-based magnetic porous organic polymer by using from internal layer of Oak fruit hull (Oak Gal)...

Underwater suspended bifunctionalized polyethyleneimine-based sponge for selective removal of anionic pollutants from aqueous solution

Highly selective and efficient removal of ionic pollutants, including ionic organic compounds and heavy metal ions from water, is still a huge challenge due to the complex nature of polluted water. To meet this challenge, we presented the synthesis of bifunctionalized polyethyleneimine-based sponges through cryo-polymerization via BDDE as the crosslinker followed by bifunctional modification with glycidyl trimethylammonium chloride (GTAC) and phenyl glycidyl ether (PGE), which simultaneously afford quaternary ammonium cation (strongly basic and hydrophilic) and phenyl (hydrophobic) functionalities, respectively. As a result, a hybrid hydrophilic-hydrophobic sponge is generated that could stably be suspended underwater due to the co-operative effect of the water-absorbing hydrophilic domain and the hydrophobic domain generating buoyancy. The quaternized and phenyl-functionalized PEI-based sponge (S_QP-PEI) demonstrated highly selective and efficient removal of anionic pollutants from water, including diclofenac sodium (DIC), methyl orange (MO) and chromium (Cr(VI)) with co-existing interferences. The Langmuir isotherms revealed the maximum adsorption capacities of 342.7 mg/g, 491.9 mg/g, and 242.7 mg/g for DIC, MO, and Cr(VI), respectively. The studies of adsorption mechanism suggested that the bifunctional S_QP-PEI sponge indeed afford both strong anion-exchange interaction and π-π interaction toward organic pollutants DIC and MO, and the strong anion-exchange interaction can be the dominated adsorption mechanism for anionic DIC, MO and Cr(VI) species. The suspended S_QP-PEI also demonstrated excellent reusability, which shows the potential of S_QP-PEI for real applications.

Poly(ethylene-imine)-Functionalized Magnetite Nanoparticles Derivatized with Folic Acid: Heating and Targeting Properties

Magnetite nanoparticles (MNPs) coated by branched poly (ethylene-imine) (PEI) were synthesized in a one-pot. Three molecular weights of PEI were tested, namely, 1.8 kDa (sample MNP-1), 10 kDa (sample MNP-2), and 25 kDa (sample MNP-3). The MNP-1 particles were further functionalized with folic acid (FA) (sample MNP-4). The four types of particles were found to behave magnetically as superparamagnetic, with MNP-1 showing the highest magnetization saturation. The particles were evaluated as possible hyperthermia agents by subjecting them to magnetic fields of 12 kA/m strength and frequencies ranging between 115 and 175 kHz. MNP-1 released the maximum heating power, reaching 330 W/g at the highest frequency, in the high side of reported values for spherical MNPs. In vitro cell viability assays of MNP-1 and MNP-4 against three cell lines expressing different levels of FA receptors (FR), namely, HEK (low expression), and HeLa (high expression), and HepG2 (high expression), demonstrated that they are not cytotoxic. When the cells were incubated in the presence of a 175 kHz magnetic field, a significant reduction in cell viability and clone formation was obtained for the high expressing FR cells incubated with MNP-4, suggesting that MNP-4 particles are good candidates for magnetic field hyperthermia and active targeting.

Protecting HaCaT cells from ionizing radiation using persimmon tannin-Aloe gel composite

Context: Persimmon tannin (extract of Diospyros kaki L.f [Ebenaceae]) and Aloe gel (extract of Aloe vera (L.) Burm.f. [Asphodelaceae]) are known as anti-radiation agents. However, radiation resistance of the persimmon tannin-Aloe gel composite remains inconclusive.Objective: To investigate the capacity of the persimmon tannin-Aloe gel composite to protect against ionising radiation at the cellular level.Materials and methods: HaCaT (human epidermal keratinocytes) cells were pre-treated with PT-A-1 (the mass ratio of persimmon tannin and Aloe gel was 2:1) or the single component (persimmon tannin or Aloe gel) at various concentrations (0, 50, 100, 200, 400, 800 μg/mL. Control group: medium with no HaCaT cells), and then radiated with X-rays (radiation dose: 4, 8, 12, 16, and 20 Gy). Cell viability, cell apoptosis, and radiation-induced intracellular reactive oxygen species (ROS) generation were analysed by CCK-8, Hoechst 33258 staining/flow cytometry, and 2',7'-dichlorfluorescein diacetate (DCFH-DA) assay, respectively, for 12 or 24 h incubation after radiation.Results: The optimal radiation dose and post-radiation incubation period were determined to be 8 Gy and 12 h. CCK-8 activity detection showed that the cell activity was 77.85% (p < 0.05, IC₅₀ = 55.67 μg/mL). The apoptotic rate was the lowest (4.32%) at 200 μg/mL of PT-A-1 towards HaCaT cells. ROS production was the most effectively suppressed by 200 μg/mL PT-A-1 towards HaCaT cells.Discussion and conclusions: The persimmon tannin-Aloe gel composite has good radioprotective effect, and which will facilitate its clinic application as a potential natural anti-radiation agent in future.

Nanoparticles of Quaternary Ammonium Polyethylenimine Derivatives for Application in Dental Materials

Various quaternary ammonium polyethylenimine (QA-PEI) derivatives have been synthesized in order to obtain nanoparticles. Due to their antibacterial activity and non-toxicity towards mammalian cells, the QA-PEI nanoparticles have been tested extensively regarding potential applications as biocidal additives in various dental composite materials. Their impact has been examined mostly for dimethacrylate-based restorative materials; however, dental cements, root canal pastes, and orthodontic adhesives have also been tested. Results of those studies showed that the addition of small quantities of QA-PEI nanoparticles, from 0.5 to 2 wt.%, led to efficient and long-lasting antibacterial effects. However, it was also discovered that the intensity of the biocidal activity strongly depended on several chemical factors, including the degree of crosslinking, length of alkyl telomeric chains, degree of N-alkylation, degree of N-methylation, counterion type, and pH. Importantly, the presence of QA-PEI nanoparticles in the studied dental composites did not negatively impact the degree of conversion in the composite matrix, nor its mechanical properties. In this review, we summarized these features and functions in order to present QA-PEI nanoparticles as modern and promising additives for dental materials that can impart unique antibacterial characteristics without deteriorating the products' structures or mechanical properties.

Green Fabrication of Tannic Acid-Inspired Magnetic Composite Nanoparticles toward Cationic Dye Capture and Selective Degradation

An environmental strategy for developing sustainable materials presents an attractive prospect for wastewater remediation. Herein, a facile, green, and economical strategy is proposed to fabricate magnetic composite nanoparticles (NPs) toward cationic dye adsorption and selective degradation. To prepare the composite TiO2-PEI-TA@Fe3O4 NPs, tannic acid (TA) and polyethyleneimine (PEI) were first used to decorate Fe3O4 NPs at aqueous solution, and then TiO2 NPs were anchored onto the surfaces of Fe3O4 NPs based on the catecholamine chemistry. The chemical composition and microstructure of the obtained NPs were systematically characterized. The NPs not only exhibited adsorption ability for the cationic dye of methylene blue (MB) but also responded to ultraviolet light to selectively degrade the adsorbed MB, and the removal (adsorption and/or degradation) ratio for MB could reach 95%. In addition, cyclic experiments showed that the removal ratio of the composite NPs for MB could still be maintained more than 85% even after five cycles. Given by the above-mentioned advantages, such a green and facile strategy for combining the adsorption and degradation methods to construct magnetic nanocomposites exhibits potential applications in cationic dye selective removal and sustainable wastewater remediation.

Selenium(VI) and copper(II) adsorption using polyethyleneimine-based resins: Effect of glutaraldehyde crosslinking and storage condition

This study synthesizes polyethyleneimine-glutaraldehyde (PEI-GA) resins using different amounts of GA to crosslink with a certain amount of PEI and compares these adsorbents for the adsorption of Cu(II) (cations) and Se(VI) (anions). Moreover, the stability of adsorption affinity of PEI-GA resins stored in open or sealed conditions is also studied. Results show that the amount of GA for PEI crosslinking does not affect the adsorption performance for Se(VI), especially when PEI/GA mass ratio is less than 2, while for Cu(II), the increase on GA amount decreases Cu(II) adsorption capacity. This difference is directly correlated to the change in the adsorption mechanism from electrostatic attraction to chelation. The primary and secondary amine groups on PEI can easily react with CO₂ in the air to form carbamate, potentially affecting the adsorption performance of PEI. Results also indicate that the adsorption efficiency for Se(VI) is hardly affected by the storage condition, while that for Cu(II) decreases significantly after 20-day storage compared to the freshly prepared ones. In addition, all of the adsorbents can selectively remove Se(VI) from Se(VI)-As(V) system and Cu(II) from Pb(II)-Cu(II) system, indicating that the crosslinking has no significant influence on the selectivity.

Novel alginate particles decorated with nickel for enhancing ciprofloxacin removal: Characterization and mechanism analysis

The extensive occurrence of antibiotics (such as ciprofloxacin) in aqueous environment had raised severe concerns due to their impacts on humans and the ecosystem. In this study, a novel nickel alginate particles adsorbent had been successfully developed by combining an alginate matrix with nickel ion through immobilization and crosslinking technology and then was applied for the batch adsorption study of ciprofloxacin to evaluate its potential performance. The as-prepared adsorbent exhibited excellent adsorption performance at the condition of the pH 7 and 328.15 K, and the results indicated that the maximum adsorption capacity was 135.18 mg g^-1. The isotherm and kinetic studies were well fitted to the Langmuir and pseudo-second-order models, respectively. A thermodynamics analysis displayed that the ciprofloxacin adsorption process was endothermic, feasible and spontaneous. The as-prepared adsorbent before and after adsorption was characterized through SEM, EDX and XPS analyses, and the particle size of the as-prepared adsorbent was roughly 914 µm. Hydrogen bond, the cation bonding bridge and n-π electron-donor-acceptor interaction might be the driving force of the ciprofloxacin adsorption process. This study demonstrated that this as-prepared adsorbent was a promising and efficient material for the ciprofloxacin adsorption from the aqueous solution.

Simultaneous capture of methyl orange and chromium(vi) from complex wastewater using polyethylenimine cation decorated magnetic carbon nanotubes as a recyclable adsorbent

Most recently, the continuous deterioration of the aquatic environment triggered by both heavy metals and synthetic organic dyes has imparted serious threats to the ecosphere and drinking water safety. However, it is still extremely challenging to treat complex wastewater containing these two classes of pollutants via a one-step method owing to the significant differences in their physicochemical properties. In the current work, versatile magnetic MWCNTs decorated with PEI (denoted as MWCNTs@Fe3O4/PEI) was fabricated by a facile, rapid and reproducible strategy and applied to as a robust adsorbent for simultaneously removing methyl orange (MO) and Cr(vi) from aqueous solutions. The physicochemical properties of the as-designed nanohybrid were investigated using various analytical techniques, i.e. XRD, FT-IR, SEM, TEM, VSM, zeta potential, etc. It was found that the surface charge properties of the MWCNTs as well as its dispersion in aqueous solution were greatly changed after the introduction of PEI molecules. The resulting nanohybrid exhibited attractive adsorption capabilities toward anionic MO and Cr(vi). In the perspective of a mono-pollutant system, the time-dependent adsorption process matched well with a pseudo-second-order kinetics equation, the adsorption isotherm data at r.t. were well fitted by a Langmuir model with maximum monolayer uptake capacity of 1727.6 mg g-1 for MO and 98.8 mg g-1 for Cr(vi), and the removal process of both pollutants was thermodynamically spontaneous and exothermic. In the MO-Cr(vi) binary system, the uptake of Cr(vi) by the as-prepared adsorbent was evidently enhanced by the presence of MO, while the coexisting Cr(vi) exerted a small negative effect on the sorption of MO; which was attributed to the different adsorption mechanisms of both pollutants on the as-recommend adsorbent. The much better adsorbing performance of the resulting MWCNTs@Fe3O4/PEI for MO and Cr(vi) than that of the pristine MWCNTs or the MWCNTs/Fe3O4 composite was mainly ascribed to the high surface area of the MWCNTs, the high density of protonated N-rich groups of PEI as well as the excellent dispersion and solubility of the resulting nanocomposites. Moreover, the obtained nanohybrids can be easily recovered after being used by a permanent magnet and still retained high stability and excellent reusability after consecutive adsorption-desorption cycles, implying its great potential in practical applications. Therefore, the as-fabricated MWCNTs@Fe3O4/PEI composite could be recommended as a promising candidate adsorbent for the simultaneous capture of MO and Cr(vi) from complex wastewater via multiple uptake mechanisms (e.g. electrostatic attraction, π-π stacking and hydrogen bonding).

Functional Chitosan Derivative and Chitin as Decolorization Materials for Methylene Blue and Methyl Orange from Aqueous Solution

Dyes are classified as one of the major pollutants of water. They have negative impacts not only on environment but also on human health. In fact, wastewater that contains these harmful substances requires many types of treatments. Therefore, alternative methods and adsorption agents are needed. Herein, we propose to evaluate the decolorization of methylene blue (MB) and methyl orange (MO) as two models of soluble dyes from water using chitin and chitosan-graft-polyacrylamide. Furthermore, the applicability of these biomacromolecules as alternative adsorption agents, their sticking probability and desorption were also examined. Experimental parameters such as dye concentration, contact time, pH solution, adsorbent dosage and temperature were thoroughly examined for the grafted chitosan and chitin. The activation energy ( E a ) and the thermodynamic variables (i.e., standard Gibb's free energy ( Δ G 0 ), standard enthalpy ( Δ H 0 ), and standard entropy ( Δ S 0 )) were determined using the Van't Hoff and Arrhenius equations. The sticking probability ( S *) model for MB and MO removal by chitin and the chitosan derivative demonstrated that both dyes were successfully removed under the proposed conditions. Desorption studies of MB and MO showed the reusability of both materials, suggesting their application for removing dyes from aqueous solution.

Optimization and modeling of methyl orange adsorption onto polyaniline nano-adsorbent through response surface methodology and differential evolution embedded neural network

Presence of pigments and dyes in water bodies are growing tremendously and pose as toxic materials and have severe health effects on human and aquatic creatures. Treatments methods for removal of these toxic dyes along with other pollutants are growing in different dimensions, among which adsorption was found a cheaper and efficient method. In this study, the performance of polyaniline-based nano-adsorbent for removal of methyl orange (MO) dye from wastewater in a batch adsorption process is studied. Along with this to minimize the number of experiments and obtain optimal conditions, a multivariate predictive model based on response surface methodology (RSM) is developed. This is compared with data-driven modeling using the artificial neural network (ANN) which is integrated with differential evolution optimization (DEO) for prediction of the adsorption of MO. The interactive effects on MO removal efficiency with respect to independent process variables were investigated. The fit of the predictive model was found to good enough with R² = 0.8635. The optimal ANN architecture with 5-12-1 topology resulted in higher R² and lower RMSE of 0.9475 and 0.1294 respectively. Pearson's Chi-square measure which provides a good measurement scale for weighing the goodness of fit is found to be 0.005 and 0.038 for RSM and ANN-DEO respectively, and other statistical metrics evaluated in this study further confirms that the ANN-DEO is very superior over RSM for model predictions.