Magnetic Polyacrylic Anion Exchange Resin: Preparation, Characterization and Adsorption Behavior of Humic Acid

Adsorption of pyrolysis oil model compound (phenol) with plasma-modified hydro-chars and mechanism exploration

Phenol is one of the important ingredients of pyrolysis oil, contributing to the high biotoxicity of pyrolysis oil. To promote the degradation and conversion of phenol during anaerobic digestion, cheap hydro-chars with high phenol adsorption capacity were produced. The phenol adsorption capabilities of the plain hydro-char, plasma modified hydro-char at 25 °C (HC-NH3-P-25) and 500 °C (HC-NH3-P-500) were evaluated, and their adsorption kinetics and thermodynamics were explored. Experimental results indicate that the phenol adsorption capability of HC-NH3-P-500 was the highest. The phenol adsorption kinetics of all samples followed the pseudo-second-order equation and interparticle diffusion model, indicating that the adsorption rate of phenol was controlled by interparticle diffusion and chemistry adsorption simultaneously. By DFT calculations, π-π stacking and hydrogen bond are the main interactions for phenol adsorption. It was observed that an enriched graphite N content decreased the average vertical distance between hydro-chars and phenol in π-π stacking complex, from 3.5120 to 3.4532 Å, causing an increase in the negative adsorption energy between phenol and hydro-char from 13.9330 to 23.4181 kJ/mol. For hydrogen bond complex, the average vertical distance decreased from 3.4885 to 3.3386 Å due to the increase in graphite N content; causing the corresponding negative adsorption energy increased from 19.0233 to 19.9517 kJ/mol. Additionally, the presence of graphite N in the hydro-char created a positive diffusion region and enhanced the electron density between hydro-char and phenol. Analyses suggest that enriched graphite N contributed to the adsorption complex stability, resulting in an improved phenol adsorption capacity.

Removal of perfluoroalkyl acids and common drinking water contaminants by weak-base anion exchange resins: Impacts of solution pH and resin properties

The underlying chemistry of weak-base (WB) anion exchange resins (AERs) for contaminant removal from water is not well documented in the literature. To address this, batch adsorption experiments were conducted at pH 4, 7, and 10 using two representative WB-AERs (polyacrylic IRA67 and polystyrene IRA96) and two representative strong-base (SB) AERs (polyacrylic IRA458 and polystyrene A520E), of differing polymer composition, for the removal of nitrate, sulfate, 3-phenylpropionic acid (3-PPA) as surrogate for natural organic matter, and six perfluoroalkyl acids (PFAAs). Under acidic (pH 4) and neutral (pH 7) conditions, the selectivity of AERs for each contaminant was predominantly influenced by polymer composition followed by the size of the resin functional group. This result reflected the WB-AERs being fully protonated and functioning identical to SB-AERs. Isotherm model parameters revealed WB-AER had higher capacity than SB-AER with analogous polymer composition and porosity regardless of resin selectivity for each contaminant. Under basic conditions (≥ pH 10), contaminant removal by WB-AERs declined due to deprotonation of the tertiary amine functional groups. Removal of PFAAs by the more hydrophobic polystyrene WB-AER (IRA96) remained approximately constant with changing pH, which was possibly due to electrostatic interactions with remaining protonated amine functional groups on the resin.

Effect of Pore Size Distribution and Amination on Adsorption Capacities of Polymeric Adsorbents

Polymeric adsorbents with different properties were synthesized via suspension polymerization. Equilibrium and kinetics experiments were then performed to verify the adsorption capacities of the resins for molecules of various sizes. The adsorption of small molecules reached equilibrium more quickly than the adsorption of large molecules. Furthermore, the resins with small pores are easy to lower their adsorption capacities for large molecules because of the pore blockage effect. After amination, the specific surface areas of the resins decreased. The average pore diameter decreased when the resin was modified with either primary or tertiary amines, but the pore diameter increased when the resin was modified with secondary amines. The phenol adsorption capacities of the amine-modified resins were reduced because of the decreased specific area. The amine-modified resins could more efficiently adsorb reactive brilliant blue 4 owing to the presence of polar functional groups.

Application of the anion-exchange resin as a complementary technique to remove residual cyanide complexes in industrial plating wastewater after conventional treatment

Cyanide is highly toxic and must be destroyed or removed before discharge into the environment. This study examined the ability of commercial anion-exchange resins to remove residual cyanide complexes from industrial plating wastewater as a complement to conventional treatment. Cyanide removal experiments were conducted with various initial concentrations, reaction times, and temperatures, and the presence of co-existing anions. The maximum cyanide removal capacity (Q_m) of the Bonlite BAMB140 resin is 31.82 mg/g and effectively removes cyanide from aqueous solution within 30 min. The cyanide removal by the resin is an endothermic process and is affected by the presence of anions in industrial plating wastewater. The relative competitiveness observed in this study was sulfate > nitrate > chloride. A mixture of 0.05 M NaCl and NaOH regenerates resin for continuous reuse for 5 cycles. The Bonlite BAMB140 resin was able to remove residual cyanide complexes from industrial plating wastewater, but the removal capacity of the resin was reduced by more than three times in batch (9.94 mg/g) and column (6349.12 mg/L) systems. Based on the results, the anion-exchange resins are expected to be used as a complementary technique to remove residual cyanide complexes in industrial plating wastewater after conventional treatment.

The effect of incorporating inorganic materials into quaternized polyacrylic polymer on its mechanical strength and adsorption behaviour for ibuprofen removal

Quaternized polyacrylic polymer has many applications in water treatment because of its ion exchange effects, but its further industrial applications are largely restricted because of its poor mechanical strength. In this work, a magnetic anion exchange resin with a polyacrylic matrix (MAP) was prepared by incorporation of Fe₃O₄ and subsequent modification with tetraethyl orthosilicate (TEOS) to improve the mechanical strength and adsorption performance. The incorporation of Fe₃O₄ significantly enhanced the mechanical strength of the polymer and improved the sphericity rate after ball milling of the polyacrylic resin from 80.1% to 97.2% as a result of hydrogen bonding between the -OH groups on Fe₃O₄ and the -NH- groups on the resin matrix. Further TEOS modification could effectively prevent Fe₃O₄ particles from dislodging from the resins. The adsorption performance was evaluated by using ibuprofen as a model compound. The adsorption kinetics showed that adsorption equilibrium was reached in 150 min. XPS analysis indicated that hydrogen bonding greatly contributed to the adsorption of ibuprofen onto the MAP. Adsorption isotherm analysis indicated that the adsorption was endothermic.

Antifouling Ion-Exchange Resins

Large quantities of organic ion-exchange resins are used worldwide for water decontamination and polishing. Fouling by microorganisms and decomposition products of natural organic matter severely limits the lifetime of these resins. Much research has thus been invested in polymer-based antifouling coatings. In the present study, poly(4-styrenesulfonate) (PSS) and a co-polymer of PSS and a zwitterionic group were used to spontaneously coat commercial Dowex 1X8 anion-exchange resin. UV-visible spectroscopy provided a precise measure of the kinetics and amount of PSS sorbed onto or into resin beads. When challenged with Chlamydomonas reinhardtii algae, uncoated resin was rapidly fouled by algae. Coating the resin with either the homopolymer of PSS or the co-polymer with zwitterion eliminated fouling. Using narrow- and wide-molecular-weight distribution PSS, a cutoff molecular weight of about 240 repeat units was found, above which PSS was unable to diffuse into the resin. Thus, only one monolayer of added PSS was sufficient to confer a highly desirable antifouling property on this resin while consuming less than 0.1% of the exchanger capacity. Radioactive sulfate ions were used to probe the kinetics of (self)exchange, which were virtually unaffected by the PSS coating. This resin treatment is a fast, ultra-low-cost step for potentially enhancing the lifetime of ion exchangers.

Preparation of Permanent Magnetic Resin Crosslinking by Diallyl Itaconate and Its Adsorptive and Anti-fouling Behaviors for Humic Acid Removal

In this research, a series of permanent magnetic anion exchange resins (MAERs) were prepared by polymerizing glycidyl methacrylate monomer and crosslinking diallyl itaconate (DAI) and divinylbenzene. The properties and performances of these novel MAERs were systematically characterized and evaluated for humic acid (HA) adsorption by batch experiments. With the increase of DAI content from 0 to 15%, the moisture of MAERs was elevated from 50.23% to 68.53%, along with the adsorption capacity increasing from 2.57 to 3.14 mmol g^-1. As the concentrations of co-existing cation (Ca²⁺ and Mg²⁺) increased, the adsorption amounts of HA dropped drastically at first and increased a little at high cation concentrations. Although ion exchange was the primary mechanism for HA adsorption, other physical interactions and electrostatic attraction between HA molecules and newly formed oxonium group also played significant roles for HA adsorption. The MAERs could be efficiently regenerated by a mixture of NaCl/NaOH solution (10%/1%), and notably, the MAER-3 with the highest DAI content displayed unapparent loss of adsorption capacity during twenty-one successive adsorption-desorption cycles. These results suggested a novel resin adsorbent for its excellent performances on adsorption, regeneration, and sedimentation in water treatment for natural organic matter removal.

Magnetic recyclable bismuth oxyiodide/polyacrylic anion exchange resin composites with enhanced photocatalytic activity under visible light

A series of magnetic recyclable bismuth oxyiodide (BiOI)/polyacrylic anion exchange resin (PAER) composites with visible light responses have been synthesized for the first time through a facile and low-cost method at normal temperature. The photocatalytic performances of BiOI/PAER composites were evaluated by photodegrading 1-amino-8-naphthol-3,6-disulfonic acid under visible light. It was found that 1-amino-8-naphthol-3,6-disulfonic acid (H-acid) removal rate reached to 90.1% (BiOI/PAER-2), which was higher than the pure BiOI (50.3%) in 60min. The enhanced photocatalytic performance of BiOI/PAER composites should be attributed to the improved separation efficiency of the charge carriers. Furthermore, the BiOI/PAER composites exhibited excellent cyclinic utilization stability, which is a key factor for their potential practical applications.

Competition and enhancement effect in coremoval of atenolol and copper by an easily regenerative magnetic cation exchange resin

This paper aimed to investigate the removal of combined Cu²⁺ and atenolol (ATL) in aqueous solution by using a newly synthesized magnetic cation exchange resin (MCER) as the adsorbent. The MCER exhibited efficient removal performance in sole, binary, pre-loading and saline systems. The adsorption kinetics of Cu²⁺ and ATL fitted both pseudo-first-order and pseudo-second order model, while better described by pseudo-second order model in binary system. In mixed Cu²⁺ and ATL solution, the adsorption of ATL was suppressed due to direct competition of carboxylic groups, while Cu²⁺ adsorption was enhanced because of the formation of surface complexes. This increasing in heterogeneity was demonstrated by adsorption isotherms, which were more suitable for Freundlich model in binary system, while better described by Langmuir model in sole system. As proved by FTIR and XPS spectra, both amino and hydroxyl groups of ATL could form complexes with Cu²⁺. Decomplexing-bridging interaction was elucidated as the leading mechanism in coremoval of Cu²⁺ and ATL, which involved [Cu-ATL] decomplexing and newly created Cu- or ATL sites for additional bridging. For saline system, the resulting competition and enhancement effects in mixed solution were amplified with the addition of co-existing cations. Moreover, the MCER could be effectively regenerated by 0.01 M HCl solution and maintain high stability over 5 adsorption-desorption cycles, which render it great potential for practical applications.

Highly efficient and environmentally benign As(III) pre-oxidation in water by using a solid redox polymer

As(III) preoxidation to As(V) is usually a requisite step for its efficient removal from water. Traditional oxidants reacting with As(III) homogenously in water suffer from the excessive dosage as well as the possible formation of disinfection byproducts. Herein, we developed a heterogeneous oxidant, i.e., a solid redox polymer (DOX), by covalently binding chlorine to a commercially available cation-exchange resin, D001. As(III) pre-oxidation by DOX is independent upon the solution pH (6-8) and ionic strength (0-0.1 M NaNO₃). The presence of natural organic matters (NOMs) exhibits slightly adverse effect on the As(III) oxidation. More attractively, much less disinfection byproducts (DBPs, CHCl₃ in this study) is formed during oxidation by DOX than by chlorine, possibly ascribed to the electrostatic repulsion between NOMs and DOX as well as the steric effect of the solid matrix. The exhausted DOX could be fully refreshed by the NaClO solution for cyclic use. The column oxidation experiment were performed by feeding the synthetic groundwater containing As(III), various minerals, and NOMs. It could result in As(III) decline from 200 × 10^-3 mg/L initially to <1 × 10^-3 mg/L with the working capacity of >33,200 bed volume (BV) even at the volumetric flow rate of 50 BV/h (i.e., EBCT = 1.2 min, equivalent to the linear velocity of 2.2 m/h). In summary, DOX is a highly efficient and environmental friendly oxidant for As(III) pre-oxidation in water treatment.

One-step approach for the synthesis of CoFe2O4@rGO core-shell nanocomposites as efficient adsorbent for removal of organic pollutants

CoFe₂O₄-reduced graphene oxide nanocomposites (CFG) have been successfully synthesized via one-step solvothermal method. The prepared CFG are characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometer and so on. The FESEM results show that CFG have uniform core-shell structure with an average diameter of about 75 nm and the thickness of the outer graphene shell is about 15-20 nm. The mass ratio of CoFe₂O₄ to graphene oxide is a key factor affecting the formation of core-shell hybrids. CFG display much higher adsorption capacity for anionic dyes than cationic dyes owing to the favorable electrostatic interaction. The adsorption capacity for methyl orange is observed as high as 263 mg g^-1 at 298 K, and the adsorption isotherms follow the Langmuir model. Furthermore, the specific saturation magnetization (Ms) of CFG is 32.8 emu g^-1, and the as-synthesized nanocomposites can be easily separated by external magnetic field after adsorption. The results suggest that CFG have great potential for the practical industrial wastewater treatment.

Adsorption of three pharmaceuticals on two magnetic ion-exchange resins

The presence of pharmaceuticals in aquatic environments poses potential risks to the ecology and human health. This study investigated the removal of three widely detected and abundant pharmaceuticals, namely, ibuprofen (IBU), diclofenac (DC), and sulfadiazine (SDZ), by two magnetic ion-exchange resins. The adsorption kinetics of the three adsorbates onto both resins was relatively fast and followed pseudo-second-order kinetics. Despite the different pore structures of the two resins, similar adsorption patterns of DC and SDZ were observed, implying the existence of an ion-exchange mechanism. IBU demonstrated a combination of interactions during the adsorption process. These interactions were dependent on the specific surface area and functional groups of the resin. The adsorption isotherm fittings verified the differences in the behavior of the three pharmaceuticals on the two magnetic ion-exchange resins. The presence of Cl- and SO4(2-) suppressed the adsorption amount, but with different inhibition levels for different adsorbates. This work facilitates the understanding of the adsorption behavior and mechanism of pharmaceuticals on magnetic ion-exchange resins. The results will expand the application of magnetic ion-exchange resins to the removal of pharmaceuticals in waters.

Chemical and bioanalytical assessments on drinking water treatments by quaternized magnetic microspheres

This study aimed to compare the toxicity reduction performance of conventional drinking water treatment (CT) and a treatment (NT) with quaternized magnetic microspheres (NDMP) based on chemical analyses. Fluorescence excitation-emission-matrix combined with parallel factor analysis identified four components in source water of different rivers or lake, and the abundance of each component differed greatly among the different samples. Compared with the CT, the NT evidently reduced the concentrations of dissolved organic carbon, adsorbable organic halogens (AOX), bromide and disinfection by-products. Toxicological evaluation indicated that the NT completely eliminated the cytotoxicity, and greatly reduced the genotoxicity and oxidative stress of all raw water. In contrast, the CT increased the cytotoxicity of Taihu Lake and the Zhongshan River water, genotoxicity of Taihu Lake and the Mangshe River water, as well as the levels of superoxide dismutase and malondialdehyde of the Mangshe River water. Correlation analysis indicated that the AOX of the treated samples was significantly correlated with the genotoxicity and glutathione concentration, but exhibited no correlation with either of them for all the samples. As it can effectively reduce pollutant levels and the toxicities of drinking water, NDMP might be widely used for drinking water treatment in future.

Fouling of anion exchange resin by fluorescence analysis in advanced treatment of municipal wastewaters

The application of anion exchange resins (AERs) has been limited by the critical problem of resin fouling, which increases the volume of the desorption concentrate and decreases treatment efficiency. To date, resin fouling has not been well studied and is poorly understood compared to membrane fouling. To reflect the resin fouling level, a resin fouling index (RFI) was established in this work according to the decrease of DOC removal after regeneration of the resin for the advanced treatment of municipal wastewater. Comparing the linear fitting results between the RFI and the fluorescence intensity indicated that the resin fouling was related to the protein-like substances with fluorescence peak T in the region of excitation wavelength <250 nm and emission wavelength <380 nm. Using their fluorescent characteristics as a label, the protein-like substances causing the fouling were further identified as hydrophilic components with molecular weights greater than 6500 Da.

Dissolved organic matter removal using magnetic anion exchange resin treatment on biological effluent of textile dyeing wastewater

This study investigated the removal of dissolved organic matter (DOM) from real dyeing bio-treatment effluents (DBEs) with the use of a novel magnetic anion exchange resin (NDMP). DOMs in two typical DBEs were fractionized using DAX-8/XAD-4 resin and ultrafiltration membranes. The hydrophilic fractions and the low molecular weight (MW) (<3kDa) DOM fractions constituted a major portion (>50%) of DOMs for the two effluents. The hydrophilic and low MW fractions of both effluents were the greatest contributors of specific UV254 absorbance (SUVA254), and the SUVA254 of DOM fractions decreased with hydrophobicity and MW. Two DBEs exhibited acute and chronic biotoxicities. Both acute and chronic toxicities of DOM fractions increased linearly with the increase of SUVA254 value. Kinetics of dissolved organic carbon (DOC) removal via NDMP treatment was performed by comparing it with that of particle active carbon (PAC). Results indicated that the removal of DOC from DBEs via NDMP was 60%, whereas DOC removals by PAC were lower than 15%. Acidic organics could be significantly removed with the use of NDMP. DOM with large MW in DBE could be removed significantly by using the same means. Removal efficiency of NDMP for DOM decreased with the decrease of MW. Compared with PAC, NDMP could significantly reduce the acute and chronic bio-toxicities of DBEs. NaCl/NaOH mixture regenerants, with selected concentrations of 10% NaCl (m/m)/1% NaOH (m/m), could improve desorption efficiency.

Rapid removal of copper with magnetic poly-acrylic weak acid resin: quantitative role of bead radius on ion exchange

A novel magnetic weak acid resin NDMC was self-synthesized for the removal of Cu(2+) from aqueous solutions. NDMC showed superior properties on the removal of Cu(2+) compared to commercial resins C106 and IRC-748, which was deeply investigated by adsorption isotherms and kinetic tests. The equilibrium adsorption amount of Cu(2+) onto NDMC (267.2mg/g) was almost twice as large as that onto IRC-748 (120.0mg/g). The adsorption kinetics of Cu(2+) onto the three resins fitted well with the pseudo-second-order equation. The initial adsorption rate h of NDMC was about 4 times that of C106 and nearly 8 times that of IRC-748 at the initial concentration of 500mg/L. External surface area was determined to be the key factor in rate-controlling by further analyzing the adsorption thermodynamics, kinetics parameters and physicochemical properties of the resins. NDMC resin with the smallest bead radius possessed the largest external surface and therefore exhibited the fastest kinetics. The adsorption amount of Cu(2+) onto NDMC was not influenced as the concentration of Na(+) increased from 1.0 to 10.0mM/L. Dilute HCl solution could effectively desorb Cu(2+). NDMC demonstrated high stability during 10 adsorption/desorption cycles, showing great potential in the rapid removal of Cu(2+) from wastewater.

A cross-omics toxicological evaluation of drinking water treated with different processes

Cross-omics profiling and phenotypic analysis were conducted to comprehensively assess the toxicities of source of drinking water (SDW), effluent of conventional treatment (ECT) and effluent of advanced treatment (EAT) in a water treatment plant. SDW feeding increased body weight, and relative liver and kidney weights of mice. Hepatic histopathological damages and serum biochemical alterations were observed in the mice fed with SDW and ECT, but EAT feeding showed no obvious effects. Transcriptomic analysis demonstrated that exposure to water samples caused differential expression of hundreds of genes in livers. Cluster analysis of the differentially expressed genes which generated by both microarrays and digital gene expression showed similar grouping patterns. Proteomic and metabolomics analyses indicated that drinking SDW, ECT and EAT generated 59, 145 and 41 significantly altered proteins in livers and 8, 2 and 0 altered metabolites in serum, respectively. SDW was found to affect several metabolic pathways including metabolism of xenobiotics by cytochrome P450 and fatty acid metabolism. SDW and ECT might induce molecular toxicities to mice, but the advanced treatment process can reduce the potential health risk by effectively removing toxic chemicals in drinking water.

Enhanced adsorption and antifouling performance of anion-exchange resin by the effect of incorporated Fe3O4 for removing humic acid

The application of anion-exchange resins (AERs) is limited by fouling, which increases the fresh resin dosage, regeneration frequency, and amount of regeneration effluent. In this study, five AERs with different Fe3O4 amounts was prepared by increasing the amount of Fe3O4 added to 100 g of monomer mixture for suspension polymerization from 0 g to 40 g. Results showed considerably improved pore volume and hydrophilicity of the resin with increased Fe3O4 content, leading to significantly enhanced adsorption and desorption of humic acid. A method of developing novel resins with enhanced adsorption and antifouling abilities by incorporating Fe3O4 was then proposed. The adsorbent structure resulting from the incorporated inorganic particles was found to be important in determining the adsorption behavior of a hybrid adsorbent.

Tunable properties induced by ion exchange in multilayer intertwined CuS microflowers with hierarchal structures

Novel hierarchical wool-ball-like copper sulfide (CuS) microflowers with a three-dimensional (3D) porous framework were successfully synthesized by the direct reaction of copper with sulfur powder using a one-pot in situ growth method at low temperature (60 °C). The CuS microflowers covered firmly the surface of the 3D porous framework. The formation mechanism was examined in detail by adjusting the amount of hydrochloric acid and reaction time. Most importantly, the chemical composition of the CuS microflowers was altered by the Se exchange without changing their morphology and structure. In this way, pure CuSe and Cu1.8Se crystalline materials were obtained on the surface of the porous microtube at different reaction times and the appropriate amount of Se powder. And interestingly, the core material remained as CuS. This behavior greatly affects the physical and chemical properties of the materials. The catalytic ability of the as-obtained CuSe@CuS and CuSe1.8@CuS composite materials to degrade methylene blue and rhodamine B is several times greater than that of the as-synthesized CuS microflowers.

Selection of magnetic anion exchange resins for the removal of dissolved organic and inorganic matters

Four magnetic anion exchange resins (MAERs) were used as adsorbents to purify drinking water. The effect of water quality (pH, temperature, ionic strength, etc.) on the performance of MAER for the removal of dissolved organic matter (DOM) was also investigated. Among the four studied MAERs, the strong base resin named NDMP-1 with high water content and enhanced exchange capacity exhibited the highest removal rate of dissolved organic carbon (DOC) (48.9% removal rate) and UV-absorbing substances (82.4% removal rate) with a resin dose of 10 mL/L after 30 min of contact time. The MAERs could also effectively remove inorganic matter such as sulfate, nitrate and fluoride. Because of the higher specific UV absorbance (SUVA) value, the DOM in the raw water was found to be removed more effectively than that in the clarified water by NDMP resin. The temperature showed a weak influence on the removal of DOC from 6 to 26 degrees C, while a relatively strong one at 36 degrees C. The removal of DOM by NDMP was also affected to some extent by the pH value. Moreover, increasing the sulfate concentration in the raw water could decrease the removal rates of DOC and UV-absorbing substances.