Quaternized magnetic microspheres for the efficient removal of reactive dyes

Preloading Long-Chain Quaternary Ammonium Groups to Synthesize a High-Efficient Anion-Exchange Resin for Eliminating Bacterial Contaminants in Drinking Water

Bacterial contamination in drinking water is a global health concern, necessitating the development of highly efficient treatment techniques. Anion-exchange resins (AERs) have long been employed for removing anionic contaminants from drinking water, but their performance for bacterial contamination is poor. Here, we develop a novel AER (AER6-1) with exceptional bactericidal effects and ultrafast adsorption rates of extracellular DNA (eDNA) (2.2- and 11.5-fold compared to other AERs) achieved through preloading quaternary ammonium groups (QAGs) with hexyl chain (-C6-N+-) on the resin exterior and successively grafting QAGs with a methyl chain (-C1-N+-) inside a resin pore. The AER6-1 outperforms other commercial AERs and ultraviolet disinfection, exhibiting superior elimination of total bacteria, potential pathogens (Escherichia coli and Pseudomonas aeruginosa), eDNA, and antibiotic resistance genes (mexF, mexB, and bacA) in actual drinking water, while maintaining a comparable anion exchange capacity with other commercial AERs. Theoretical calculations of density functional theory and xDLVO combined with XPS elucidate the crucial roles of hydrogen bonding and hydrophobic force provided by the resin skeleton and -C6-N+- in cleaving the bacterial cell membrane and increasing the adsorption kinetics on eDNA. This study broadens the scope of AERs and highlights an effective way of simultaneously removing bacterial and anionic contaminants from drinking water.

Magnetic porous microspheres altering interfacial thermodynamics of sewage sludge to drive metabolic cooperation for efficient methanogenesis

Controllable and recyclable magnetic porous microspheres (MPMs) have been proposed as a means for enhancing the anaerobic digestion (AD) of sludge, as they do not require continuous replenishment and can serve as carriers for anaerobes. However, the effects of MPMs on the interfacial thermodynamics of sludge and the biological responses triggered by abiotic effects in AD systems remain to be clarified. Herein, the underlying mechanisms by which MPMs alter the solid-liquid interface of sludge to drive methanogenesis were investigated. A significant increase in the contents of 13C and 2H (D) in methane molecules was observed in the presence of MPMs, suggesting that MPMs might enhance the CO2-reduction methanogenesis and participation of water in methane generation. Experimental results demonstrated that the addition of MPMs did not promote the anaerobic bioconversion of soluble organics for methanogenesis, suggesting that the enhanced methanogenesis and water participation were not achieved through promotion of the bioconversion of original liquid-state organics in sludge. Analyses of the capillary force, surface adhesion force, and interfacial proton-coupled electron transfer (PCET) of MPMs revealed that MPMs can enhance mass transfer, effective contact, and electron-proton transfer with sludge. These outcomes were confirmed by the statistical analyses of variations in the interfacial thermodynamics and PCET of sludge with and without MPMs during AD. It was thus proposed that the MPMs enhanced the PCET of sludge and PCET-driven release of protons from water by promoting the interfacial Lewis acid-base interactions of sludge, thereby resulting in the enrichment of free and attached methanogenic consortia and the high energy-conserving metabolic cooperation. This proposition was further confirmed by identifying the predominant syntrophic partners, suggesting that PCET-based efficient methanogenesis was attributable to the enrichment of genomes harbouring CO2-reducing pathway and genes encoding water-mediated proton transfer. These findings offer new insights into how substrate properties can be altered by exogenous materials to enable highly efficient methanogenesis.

Pollutants in aquatic system: a frontier perspective of emerging threat and strategies to solve the crisis for safe drinking water

Water is an indispensable natural resource and is the most vital substance for the existence of life on earth. However, due to anthropogenic activities, it is being polluted at an alarming rate which has led to serious concern about water shortage across the world. Moreover, toxic contaminants released into water bodies from various industrial and domestic activities negatively affect aquatic and terrestrial organisms and cause serious diseases such as cancer, renal problems, gastroenteritis, diarrhea, and nausea in humans. Therefore, water treatments that can eliminate toxins are very crucial. Unfortunately, pollution treatment remains a difficulty when four broad considerations are taken into account: effectiveness, reusability, environmental friendliness, and affordability. In this situation, protecting water from contamination or creating affordable remedial techniques has become a serious issue. Although traditional wastewater treatment technologies have existed since antiquity, they are both expensive and inefficient. Nowadays, advanced sustainable technical approaches are being created to replace traditional wastewater treatment processes. The present study reviews the sources, toxicity, and possible remediation techniques of the water contaminants.

Alkaline-thermal hydrolysate of waste activated sludge as a co-metabolic substrate enhances biodegradation of refractory dye reactive black 5

Aromatic azo dyes possess inherent resistance and are known to be carcinogenic, posing a significant threat to human and ecosystems. Enhancing the biodegradation of azo dyes usually requires the presence of co-metabolic substrates to optimize the process. In addressing the issue of excessive waste activated sludge (WAS) generation, this study explored the potential of utilizing alkaline-thermal hydrolysate of WAS as a co-metabolic substrate to boost the degradation of reactive black 5 (RB5) dyes. The acclimated microbial consortium, when supplemented with the WAS hydrolysate obtained at a hydrolysis temperature of 30 °C, achieved an impressive RB5 decolorization efficiency of 90.3% (pH = 7, 35 °C) with a corresponding COD removal efficiency of 45.0%. The addition of WAS hydrolysate as a co-substrate conferred the consortium with a remarkable tolerance to high dye concentration (1500 mg/L RB5) and salinity levels (4-5%), surpassing the performance of conventional co-metabolic sugars in RB5 degradation. 3D-EEM analysis revealed that protein-like substances rich in tyrosine and tryptophan, present in the WAS hydrolysate, played a crucial role in promoting RB5 biodegradation. Furthermore, the microbial consortium community exhibited an enrichment of dye-degrading species, including Acidovorax, Bordetella, Kerstersia, and Brevundimonas, which dominated the community. Notably, functional genes associated with dye degradation and intermediates were also enriched during the RB5 decolorization and biodegradation process. These findings present a practical strategy for the simultaneous treatment of dye-containing wastewater and recycling of WAS.

Thermodynamics of Azo Dye Adsorption on a Newly Synthesized Titania-Doped Silica Aerogel by Cogelation: A Comparative Investigation with Silica Aerogels and Activated Charcoal

The adsorption isotherms of azo dyes on a newly synthesized titania-doped silica (TdS) aerogel compared to silica aerogels and activated charcoal (AC) are systematically investigated. Monolithic TdS aerogels were synthesized by the cogelation process followed by supercritical drying of tetraethyl orthosilicate (TEOS) as a gel precursor and titanium(IV) isopropoxide (TTIP) as a metal complex precursor for co-polymerization in ethanol solvent. An acid-base catalyst was used for the hydrolysis and condensation of TEOS and TTIP. The effect of Ti⁴⁺ doping in a silica aerogel on the mesoporous structure and the adsorption capacity of methylene blue (MB) and crystal violet (CV) dyes were evaluated from the UV-vis absorption spectra. In order to compare the adsorption isotherms, the surface areas of silica and TdS aerogels were first normalized with respect to AC, as adsorption is a surface phenomenon. The azo dye equilibrium adsorption data were analyzed using different isotherm equations and found to follow the Langmuir adsorption isotherm. The maximum monolayer adsorption capacities for the adsorbent TdS aerogel normalized with the AC of the Langmuir isotherm are 131.58 and 159.89 mg/g for MB and CV dyes, respectively. From the Langmuir curve fitting, the Q _max value of the TdS aerogel was found to increase by 1.22-fold compared to AC, while it increased 1.25-1.53-fold compared to the silica aerogel. After four cycles, regeneration efficiency values for MB and CV dyes are about 84 and 80%, respectively. The study demonstrates the excellent potential and recovery rate of silica and TdS aerogel adsorbents in removing dyes from wastewater. The pore volume and average pore size of the new aerogel, TdS, were found to be lower than those of the silica aerogel. Thus, a new TdS aerogel with a high capacity of adsorption of azo dyes is successfully achieved.

Biological magnetic ion exchange resin on advanced treatment of synthetic wastewater

In this work, three biological ion exchange systems and one biological activated carbon (BAC) system were established by employing magnetic ion exchange resin (MIEX), non-magnetic resin (NIEX), polystyrenic resin (DIEX) and granular activated carbon as the biocarrier for advanced treatment of wastewater. Dissolved organic carbon (DOC) removal of four systems all stabilized at about 84% due to biodegradation. The start-up period of bio-MIEX (nearly 40 d) was greatly shorter than that of others (nearly 190 d). Ibuprofen removal was ascribed to adsorption in the initial stage, which subsequently changed to the effect of biodegradation. After the start-up period, ibuprofen removal was nearly 100% (bio-MIEX), 60% (bio-NIEX), 61% (bio-DIEX) and 89% (BAC). According to the surface observation, ATP and protein measurement and metagenomic analysis, the superior performance of bio-MIEX could be attributed to its highest biological activity resulted from the presence of Fe₃O₄ rather than polymer matrix and surface roughness.

A new process to further remove dissolved organic matter and disinfection by-product formation potential during drinking water treatment

Biological activated carbon (BAC) will produce soluble microbial products (SMPs), which affect effluent quality. To clarify the mechanism by which BAC affects effluent water quality, the processes of a drinking water plant in Jiangsu Province were investigated. It was found that during the O₃-BAC process, although ozonation could remove dissolved organic matter (DOC) to a certain extent, the DOC increased from 4.44 to 4.47 mg/L after BAC. Dissolved organic matter (DOM) in effluent from different processes was divided into five fractions based on hydrophilicity and hydrophobicity by resin fractionation. Through fluorescence excitation-emission matrix (EEM) spectroscopy combined with DOC analysis, it was found that SMPs are mainly included in transitional hydrophilic neutral (TPIN) fraction, which was the main cause of the DOC increase. Therefore, a new combined process was designed to remove TPIN effectively by coagulation after biological treatment, and found that coagulation had a good removal rate (13.2%) on TPIN. The trihalomethane formation potential (THMFP) of TPIN could be reduced effectively by 44.9% after coagulation. Compared with the old process, the new combined process had a higher removal rate (14.2-30.0%) of DOC, as well as a greater reduction of THMFP (29.0-78.6%) and haloacetic acid formation potential (HAAFP) (46.4-75.3%). This study aims to reveal the mechanism by which SMPs affect effluent water quality and exacerbate health risks, and to propose a solution to provide theoretical support for the design and optimization of drinking water treatment processes.

Quaternary Ammonium Groups Modified Magnetic Cyclodextrin Polymers for Highly Efficient Dye Removal and Sterilization in Water Purification

Water recovery is a significant proposition for human survival and sustainable development, and we never stop searching for more efficient, easy-operating, low-cost and environmentally friendly methods to decontaminate water bodies. Herein, we combined the advantages of β-cyclodextrin (β-CD), magnetite nanoparticles (MNs), and two kinds of quaternary ammonium salts to synthesize two porous quaternary ammonium groups capped magnetic β-CD polymers (QMCDP1 and QMCDP2) to remove organic pollutants and eradicate pathogenic microorganisms effectively through a single implementation. In this setting, β-CD polymer (CDP) was utilized as the porous substrate material, while MNs endowed the materials with excellent magnetism enhancing recyclability in practical application scenarios, and the grafting of quaternary ammonium groups was beneficial for the adsorption of anionic dyes and sterilization. Both QMCDPs outperformed uncapped MCDPs in their adsorption ability of anionic pollutants, using methyl blue (MB) and orange G (OG) as model dyes. Additionally, QMCDP2, which was modified with longer alkyl chains than QMCDP1, exhibits superior bactericidal efficacy with a 99.47% removal rate for Staphylococcus aureus. Accordingly, this study provides some insights into designing a well-performed and easily recyclable adsorbent for simultaneous sterilization and adsorption of organic contaminants in wastewater.

Application of calcium alginate-PANI@sawdust wood hydrogel bio-beads for the removal of orange G dye from aqueous solution

This work aims to investigate the adsorption performance of orange G (OG) dye from aqueous solutions employing PANI@sawdust biocomposite enrobed by calcium-alginate bio-beads (Alg-PANI@SD). The as-prepared adsorbent was characterized by scanning-electron-microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and Fourier transforms infrared (FT-IR) spectroscopy and used to remove orange G dye from aqueous water. Batch tests were performed as a function of adsorbent dosage, pH, contact time, interfering ions, and initial OG dye concentration. Experimental results show that the kinetic model of pseudo-first-order (PFO) and Freundlich isotherm perfectly fit the entire experimental data. Additionally, the prepared composite exhibited an excellent regeneration capacity and reusability for OG dye removal. The results revealed that the as-prepared Alg-PANI@SD bio-beads have the potential to be applied as a low-cost adsorbent for the adsorption of OG dye from aqueous media.

Design and Preparation of Imidazole Ionic Liquid-Based Magnetic Polymers and Its Adsorption on Sunset Yellow Dye

Magnetic polymers are often used as loading materials for ionic liquids because of their excellent magnetic separation properties. In this study, a novel imidazolium-based ionic liquid-modified magnetic polymer was synthesized by suspension polymerization and grafting, denoted as γ-Fe₂O₃@GMA@IM, and this magnetic polymer was used for the adsorption of the acid dye FCF. The magnetic polymer was characterized by SEM, FTIR, XRD, VSM and TGA. These techniques were used to reveal the overall physical properties of magnetic polymers, including the presence of morphology, functional groups, crystalline properties, magnetism and thermal stability. Studies have shown that γ-Fe₂O₃@GMA@IM can adsorb FCF in a wide pH range (2–10), with a maximum adsorption capacity of 445 mg/g. The adsorption data were more in line with the pseudo-second-order kinetic model and the Freundlich isotherm. In order to investigate its reusability, this study used 10% NaCl as the desorption solution, and carried out five batches of adsorption–desorption cycles. After five cycles, the adsorption effect was maintained at 98.3%, which showed a good recycling performance.

A highly efficient technique to simultaneously remove acidic and basic dyes using magnetic ion-exchange microbeads

The purpose of this study was to examine the combination of magnetic anion-exchange microbeads (MAM) and magnetic cation-exchange microbeads (MCM) to remove crystal violet (CV; a basic dye) and acid green 9 (AG9; an acidic dye) from their individual and combined solutions. Adsorption kinetics and isotherms experiments were performed in batch mode. CV and AG9 displayed superior affinity towards MCM and MAM, respectively, and their combined solution was efficiently adsorbed by combining MCM and MAM. The pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models well described the adsorption kinetic data, and the pseudo-second-order model appeared a better fit for the two-component CV/AG9 system. The better fit of the Langmuir isotherm for CV adsorption indicated that CV adsorption occurred on active sites with equal affinity in the monolayer. In contrast, AG9 adsorption onto the heterogeneous MAM surface appeared to be multilayered adsorption. The adsorption capacities of the two dyes decreased with the increase in the co-existing salt concentration and increased only slightly at the high salt level due to the salting-out effect. Moreover, these microbeads maintained most of their initial capacity during five reuse cycles, indicating the great potential of MCM and MAM to remove basic and acidic dyes in practical applications.

Performance and mechanism in degradation of typical antibiotics and antibiotic resistance genes by magnetic resin-mediated UV-Fenton process

Incomplete removal of antibiotics and antibiotic resistance genes (ARGs) has often been reported in wastewater treatment plants. More efficient treatment processes are needed to reduce their risks to the environment. Herein, we evaluated the degradation of antibiotics and ARGs by using magnetic anion exchange resin (MAER) as UV-Fenton catalyst. Sulfamethoxazole (SMZ), ofloxacin (OFX), and amoxicillin (AMX) were selected as the target compounds. The three antibiotics were almost completely degraded (> 99%) following the MAER UV-Fenton reaction for 30 min. From the degradation mechanism study, it was found that Fe³⁺/Fe²⁺ could be cyclically transferred from the catalyst at permeable interface, and the photo-generated electrons could be effectively separated. The dominant reactive radicals for antibiotics degradation were hydroxide during the MAER UV-Fenton reaction. The degradation pathway for sulfamethoxazole was proposed. In addition, wastewater samples from a wastewater treatment plant were applied to investigate the removal efficiency of antibiotics and their ARGs by the MAER UV-Fenton system. A rapid decrease in antibiotics and ARGs level was observed with this reaction system. The results from this study suggest that the MAER-mediated UV-Fenton reaction could be applied for the effective removal of antibiotics and ARGs in wastewater.

Removal of ibuprofen from aqueous media by adsorption: A comprehensive review

Ibuprofen (IBP) is a non-steroidal anti-inflammatory drug released into the environment through hospital and medical effluents, pharmaceutical wastewater and veterinary use. The aim of this paper is to review the empirical findings on the adsorption of IBP from aqueous media. A preliminary ecotoxicological assessment confirmed the environmental risk of IBP in the aqueous environment. Open literature works considered in this review were for the past decade (2010-2020). Carbon-based adsorbents are the best class of adsorbent for the uptake of IBP and the highest reported maximum adsorption capacity (q_max) for IBP is 496.1 mg/g by SWCNTs. The range of adsorption capacities for IBP uptake in this review is between 0.0496 and 496.1 mg/g. The mechanism of uptake is majorly by hydrophobic interactions, π - π stacking, hydrogen bonds, electrostatic interactions and dipole-dipole interaction. IBP uptake was best fit to a wide variety of isotherm models but was well suited to the pseudo-second order kinetics model. The thermodynamics of IBP uptake depends majorly on the nature of the adsorbent and desorption from the solid phase is based on an appropriate choice of the eluent. Knowledge gaps were observed in used adsorbent disposal and process improvement. In the future, interest would increase in scale-up, industrial applications and practical utilisation of the research findings which would help in sustainable water resource management.

Study on the adsorption and desorption performance of magnetic resin for Congo red

This study was to evaluate the adsorption capability of a magnetic resin (NDMP) to the removal of Congo red (CR) from aqueous solution. The adsorption kinetic and isotherm of NDMP were studied, as well as the desorption performance of NDMP. The results showed that the adsorption process of NDMP on CR was more suitable for Pseudo-second-order kinetic model. The whole adsorption process was affected by intraparticle diffusion and ion exchange. The adsorption isotherm of CR by NDMP was fitted better with Langmuir model. It showed that the adsorption of CR on NDMP resin was single layer adsorption. The maximum adsorption capacity (Q_m) of CR at 308 K can reach 354.29 mg/g. In the desorption, 10% NaCl and NaOH eluents had better desorption rate for CR than other mass fraction. While NaCl(10%)-MeOH mixed eluent with volume ratio of 3:7 had the best regeneration performance. The desorption rate can reach 90% within 30 min. The adsorption performance of NDMP on CR didn't decrease after 13 times successive adsorption-desorption by NaCl(10%)-methanol eluent, indicating that NDMP can be efficiently regenerated. The excellent adsorption-desorption performance of NDMP on CR suggests that the magnetic resin has a great potential for treating CR dye wastewater.

Enhanced Photo–Fenton Removal Efficiency with Core-Shell Magnetic Resin Catalyst for Textile Dyeing Wastewater Treatment

Heterogeneous photo–Fenton reactions have been regarded as important technologies for the treatment of textile dyeing wastewaters. In this work, an efficient core-shell magnetic anion exchange resin (MAER) was prepared through in situ polymerization and used to remove reactive brilliant red (X-3B) in a UV–Fenton system. The MAER exhibited satisfactory removal efficiency for X-3B because of its highly effective catalytic activity. More than 99% of the X-3B (50 mg/L) was removed within 20 min in the UV–Fenton reaction. This is because the uniformly dispersed core-shell magnetic microsphere resin could suppress the aggregation of Fe3O4 nanoparticles and, thus, enhance the exposure of Fe reaction sites for catalytic reaction with H2O2. The good adsorption capacity of MAER also played an important role in promoting contact between X-3B and reactive radicals during the reaction. Mechanism research showed that hydroxyl radical (•OH) was the main reactive radicals for the removal of X-3B in the MAER UV–Fenton system. The MAER can be easily separated by a magnet after catalytic reactions. Moreover, the matrix effects of different substrates (Cl−, NO3−, SO42−, and humic acid) were investigated. The results showed that SO42− could be beneficial to improve the removal of X-3B but that the others decrease the removal. The MAER UV–Fenton also removed significant amounts of total organic carbon (TOC) for the X-3B solution and an actual textile dyeing industrial wastewater. The heterogeneous oxidation system established in this work may suggest prospects for practical applications in the treatment of textile dyeing wastewater.

New insights into the fractionation of effluent organic matter on diagnosis of key composition affecting advanced phosphate removal by Zr-based nanocomposite

The influence of effluent organic matter (EfOM) on phosphate removal by adsorption plays an important role in evaluating the applicability of adsorbents. Currently, molecular understanding of EfOM regarding its impact on adsorption is insufficient due to a lack of appropriate EfOM fractionation/characterization protocols, as associated with the specific structure-function property of adsorbents. In this work, a combined method coupling DEAE/XAD fractionation with molecular characterization was proposed, targeting the versatile structure-function characters of nanocomposite, to reveal the composition of EfOM as well as its impact on phosphate removal by nanocomposite during long-term adsorption/regeneration runs. Zirconium-based polystyrene anion exchanger (HZO-201) was selected as a representative nanocomposite, featuring with porous networking matrix, positively charged surface and multiple adsorptive sites. The EfOM samples from three biologically treated sewage effluent sources were separated into fractions of negatively charged organic acid (OA) and hydrophobic-, transphilic-, hydrophilic-neutral/base (HPO-n/b, TPI-n/b and HPI-n/b). The combined method enables effective differentiation of the charge, aromaticity, molecular weight and functionalities of the fractions, matching the multiple structural/surface characteristics of HZO-201 and favoring the evaluation on the impact of the EfOM fractions. The interference sequence of the EfOM fractions on phosphate removal followed an order of OA > HPO-n/b > TPI-n/b > HPI-n/b. The OA fraction, characterized by negatively charged, aromatic functionalities and broad molecular weight distribution (1-5 kDa and 14 kDa), was recognized as the key interfering fraction, presumably due to its multiple adsorption pathways (i.e., ion exchange, π-π interactions and pore filling). Particularly, the low-molecular-weight OA moieties (1-4 kDa) progressively accumulated onto the nanocomposite via irreversible adsorption, causing a continuous phosphate-capacity loss by 32.70% over multiple cycles. We believe the combined fractionation/characterization method may be extended to other complex water systems to identify key influential organic matters in polishing treatment of various pollutants by adsorption.

Polyethylenimine-functionalized polyacrylonitrile anion exchange fiber as a novel adsorbent for rapid removal of nitrate from wastewater

The development of an adsorbent with high adsorption ability and favorable cyclic regeneration performance for the removal of nitrate residues from wastewater is a task of vital importance. To this end, polyacrylonitrile fiber (PANF) was modified with polyethyleneimine (PEI), and alkyl groups were then introduced around the active amine groups to prepare three polymer-based anion exchange fibers (PAN-PEI-3C, PAN-PEI-5C, and PAN-PEI-8C). The novel fibers were characterized using techniques such as scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The adsorption isotherms of the fibers were best fitted by the Langmuir model, and PAN-PEI-5C exhibited a higher adsorption amount of nitrate (31.32 mg/g) than the other adsorbents. The equilibrium was reached expeditiously (within 10 min), and both pseudo-first-order and pseudo-second-order models could well describe the adsorption kinetics. More attractively, the saturated PAN-PEI-5C could be eluted using a low-concentration (0.3 M) NaCl solution, without any sharp loss of adsorption amount for five consecutive cycles in the presence of dissolved organic matter (DOM). Furthermore, PAN-PEI-5C could effectively adsorb low-concentration nitrate from real secondary effluents in a fixed-bed column experiment. Our work provides a promising and low-cost material for the removal of nitrate residues in practical applications.

Surficial N+ charge density indicating antibacterial capacity of quaternary ammonium resins in water environment

The antibacterial effects of quaternary ammonium resins (QARs) have been reported for decades, but there are few practical applications because of limited improvements in bactericidal capacity and the absence of an efficient antibacterial-indicating parameter. An in-situ determination method of surficial N⁺ groups for QARs, defined as surficial N⁺ charge density, was first established to merely quantify the exposed surficial quaternary ammonium groups (QAs). The mechanism of the new method depends on the tetraphenylboron sodium standard solution (TS), which is a colloidal solution with high steric hindrance, making it difficult to permeate into QARs and further react with the inner QAs. The results showed that the antibacterial efficacy of QARs correlates with the surficial N⁺ charge density with R² > 0.95 (R² of 0.97 for Escherichia coli, R² of 0.96 for Staphylococcus aureus) but not with the strong-base group exchange capacity or zeta potential. Furthermore, the surficial N⁺ charge density was demonstrated efficient to indicate the antibacterial capacities against both gram-negative and gram-positive bacteria for commercial QARs, including acrylic, styrene and pyridine resin skeletons, especially for the QARs with similar skeletons and similar QAs. Based on the finding that the bactericidal groups merely involve the surficial QAs of QARs, this study proposes a new direction for improving the antibacterial capacity by enriching the surficial QAs and enhancing the bactericidal property of these surficial QAs, and provides a practicable synthesis with two-step quaternization.

Application progress of enhanced coagulation in water treatment

Water industries worldwide consider coagulation/flocculation to be one of the major treatment methods for improving the overall efficiency and cost effectiveness of water and wastewater treatment. Enhancing the coagulation process is currently a popular research topic. In this review article, the latest developments in enhanced coagulation are summarized. In addition, the mechanisms of enhanced coagulation and the effect of process parameters on processing efficiency are discussed from the perspective of ballast-enhanced coagulation, preoxidation, ultrasound, and composite coagulants. Finally, improvements and new directions for enhanced coagulation are proposed.

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.

Multifunctional β-Cyclodextrin Polymer for Simultaneous Removal of Natural Organic Matter and Organic Micropollutants and Detrimental Microorganisms from Water

Natural organic matter (NOM), organic micropollutants (OMPs), and detrimental microorganisms are three major pollutants that affect water quality. To remove these pollutants, a quaternary ammonium-functionalized β-cyclodextrin polymer (β-CDP) is successfully synthesized in the aqueous phase. The N₂ and CO₂ adsorption/desorption analysis showed that the polymer mainly contains ultra-micropores (<1 nm), with a Langmuir surface area of 89 m² g^-1. Two kinds of NOM, humic acid and fulvic acid, and five OMPs, 2-naphthol (2-NO), 3-phenylphenol (3-PH), 2,4,6-trichlorophenol (2,4,6-TCP), bisphenol A (BPA), and bisphenol S (BPS), were selected as model pollutants to study the performance of β-CDP and three kinds of commercial adsorbents, including granular activated carbon, DARCO-AC, and two resins, XAD-4 and D-201, were used for comparison. The polymer shows ultrarapid adsorption kinetics for the removal of these pollutants, with pseudo-second-order rate constants two to three orders of magnitude higher than that of the commercial activated carbon and resins. Due to the different adsorption sites of NOM and OMPs, β-CDP can simultaneously remove these pollutants without competitive adsorption. The maximum adsorption capacity of β-CDP for HA, FA, 2-NO, 3-PH, 2,4,6-TCP, BPA, and BPS based on the Langmuir model is 40, 166, 74, 101, 108, 103, and 117 mg g^-1, respectively. After use, the polymer can be easily regenerated at room temperature. In addition, β-CDP also showed excellent bactericidal properties due to the quaternary ammonium groups. At a concentration of 15 g L^-1, β-CDP can remove 98% of the tested Escherichia coli. Moreover, the synthesis of β-CDP is simple, green, and easy to industrialize. All of these findings indicate that β-CDP, as an ideal multifunctional material, presents potential for practical applications for water treatment and disinfection.

Characterizing property and treatability of dissolved effluent organic matter using size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors

In this study, size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors was used for characterizing property and treatability of effluent organic matter (EfOM) from 12 wastewater treatment plants. According to their apparent molecular weight (AMW), EfOM fractions were assigned to biopolymers (>20 kDa), humic substances that comprise sub-fractions of humic-like acids (HA-I & HA-II, 2.3-7.0 kDa) and fulvic-like acids (FA, 1.5-2.3 kDa), building blocks (0.55-1.5 kDa) and low molecular weight neutral substances (<550 Da). The fractions of biopolymers and low molecular weight neutral substances didn't show humic-like fluorescence, while the fractions of HA-II, FA and building blocks usually had signatures of both humic-like and protein-like fluorescence. Humic substances generally contributed the largest proportion of dissolved organic carbon and nitrogen (DOC & DON) in effluents. Coagulation removed EfOM fractions following the order of biopolymers > HA subfraction > FA subfraction > building blocks, while little removal of protein-like fluorescence in HA-II and FA subfractions was detected. Anion exchange treatment could effectively reduce DOC and DON concentrations; the sequence of the treatment efficiency was humic substances > biopolymers > building blocks. Increasing O₃ doses caused DOC and DON of EfOM to be gradually transformed from large AMW fractions into small AMW fractions, while chromophores and fluorophores in HA subfractions were relatively more refractory than those in the other fractions. Size exclusion chromatography with multiple detectors are suggested to be an informative technique for estimating treatability of EfOM by advanced wastewater treatment processes.

Anion-exchange resin adsorption followed by electrolysis: A new disinfection approach to control halogenated disinfection byproducts in drinking water

Bromide and natural organic matter (NOM) are both precursors of halogenated disinfection byproducts (DBPs) in drinking water. During drinking water treatment process, chloride-form anion-exchange resin adsorption is expected to be capable of removing these DBP precursors and in the meantime releasing chloride ions. The released chloride as well as the chloride initially present in source water could be oxidized through electrolysis to generate free chlorine for disinfection. Based on the above assumptions, we developed a new disinfection approach using chloride-form anion-exchange resin adsorption followed by electrolysis to control halogenated DBPs. Parameter setup and optimization were performed for resin adsorption and electrolysis processes. Results showed that 93.7% of NOM and 90% of bromide could be removed at a resin dose of 20 mL per 2 L of simulated source water sample with a contact time of 1 h. Meanwhile, 49.5 mg/L of chloride was released from the resin to the water sample via anion-exchange, and the released chloride was further oxidized by electrolysis (Ti/RuO₂-IrO₂ anode and graphite cathode, current intensity of 0.4 A) to generate free chlorine (5 mg/L as Cl₂) within 192 s. With this new approach, formation of total organic halogen, four trihalomethanes, and five haloacetic acids was reduced by 86.4%, 98.5%, and 93.2%, respectively, compared with chemical chlorination alone. Although the new approach might enhance the formation of some phenolic DBPs by decreasing bromide levels in source water, the overall cytotoxicity of the water samples treated with the new approach was significantly decreased by 68.8% according to a human hepatoma cell cytotoxicity assay. Notably, disinfection ability evaluation showed that the new approach achieved 3.36-log₁₀ reductions of three seeded bacteria (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) in 19 s, suggesting that it was not only effective to E. coli but also effective to the chlorine-resistant bacteria (P. aeruginosa and S. aureus).

Preferential adsorption of nitrate with different trialkylamine modified resins and their preliminary investigation for advanced treatment of municipal wastewater

In this paper, a series of mono-functional and bifunctional anion exchange resins with different kinds of trialkylammonium groups were synthesized and used for adsorption of nitrate from aqueous solution. The obtained resins were systematically characterized by scanning electron microscopy, Fourier transform infrared spectrometry and pore size distribution. Adsorptive behaviors and mechanisms were investigated by batch experiments. The nitrate could be preferentially adsorbed in the presence of chloride, sulfate and humic acid by longer-chain trialkylamine modified resins. Especially, the L20 resin with the triethylammonium functional group was demonstrated to possess high selectivity toward nitrate with the highest distribution coefficient among all tested resins. For both single and bi-solutes systems, the adsorption isotherm data could be well fitted with the Langmuir model, while the experimental kinetic data was well described by both pseudo first-order and second-order kinetic model. The L20 resin could be reused after many adsorption-desorption cycles with most of its virgin adsorption capacity for advanced wastewater treatment, indicating its great potential for the selective and efficient removal of nitrate from large amounts of municipal wastewater or surface water.

Modified magnetic chitosan microparticles as novel superior adsorbents with huge "force field" for capturing food dyes

In this study, modified magnetic chitosan microparticles (MCDs) were fabricated and used as adsorbents for the removal of Food Yellow 3 (FY3) and Acid Yellow 23 (AY23) from aqueous solution. The magnetic microparticles were characterized by scanning electronic microscope, Brunauer-Emmett-Teller specific surface area, elemental analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis, differential scanning calorimetry, and vibrating-sample magnetometer. Then, the effects of pH value, initial dye concentration, and contact time on the adsorption of FY3 and AY23 by MCDs were investigated. Evidently, MCDs showed excellent adsorption performance for both food dyes, and their adsorption capacities (833.33 mg/g for FY3 and 666.67 mg/g for AY23) were considerably higher than those of unmodified adsorbents, which could be attributed to the electrostatic interaction and ion exchange between the grafted cationic polymer and food dyes. Adsorption isotherm and kinetic data of the magnetic microparticles were well fitted by Langmuir isotherm and pseudo-second-order kinetic model, respectively. The regeneration and reusability of MCDs were also explored. Results showed that more than 80% adsorption capacities of MCDs for FY3 and AY23 remained after five adsorption-desorption cycles.

Antimicrobial resins with quaternary ammonium salts as a supplement to combat the antibiotic resistome in drinking water treatment plants

The increasing finding of pathogens and antibiotic resistance genes (ARGs) in drinking water has become one of the most challenging global health threats worldwide. However, conventional disinfection strategies in drinking water treatment plants (DWTPs) require further optimization in combating the antibiotic resistome. Here, we show that antimicrobial resins with quaternary ammonium salts (AMRs-QAS) exhibit great potentials in diminishing specific potential pathogens that relatively resist chlorine or UV disinfection in DWTPs, and comprehensive analyses using microscopy and fluorescence techniques revealed that the antimicrobial capacity of AMRs-QAS mainly proceed via the bacterial adsorption and cell membrane dissociation. Moreover, a total of 15 among 30 selected ARGs, as well as 4 selected potential pathogens including Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and Staphylococcus aureus were all detected in the source water. Coupling the AMRs-QAS with 0.2 mg/L chlorine resulted in higher removal efficiencies than chlorination (2 mg/L) or UV disinfection (400 mJ cm^-2) for all the detected pathogens and ARGs in drinking water and significantly decreased the relative abundances of Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, as well as all the detected ARGs (p < 0.05). Co-occurrences of pathogens and ARGs were revealed by a correlation network and possibly accounts for the ARGs removal. This coupled disinfection strategy overcomes the limitations of individual disinfection methods, i.e. the enrichment of specific pathogens and ARGs among bacterial populations, and provides an alternative for minimizing health risks induced by the antibiotic resistome in DWTPs.

Distribution of endocrine-disrupting chemicals in colloidal and soluble phases in municipal secondary effluents and their removal by different advanced treatment processes

In this work, the partition of endocrine-disrupting chemicals (EDCs) in colloid-bound and truly dissolved phases in municipal wastewater before and after advanced treatment processes was determined. The effluents, which were filtered using a 0.45 μm membrane, were further separated with the 1 kDa cross-flow ultrafiltration system into two phases, namely, colloidal phase (0.45 μm-1 kDa) and soluble phase (<1 kDa), and the partition coefficients of typical EDCs to colloids (Kcoc) were calculated. The removal of typical EDCs and their estrogenic activity in secondary effluent by coagulation sedimentation (CS), granular activated carbon (GAC) adsorption, magnetic ion exchange resin (NDMP), and ozone processes was compared. Results show that the percentages of colloid-bound EDCs were noteworthy and ranged between 7.8% and 44.3% in secondary effluents. The reduction in EDCs resulting from the GAC adsorption process was positively correlated to their logKcoc, thus suggesting that the adsorption of EDCs onto granular activated carbon and colloids exhibited a similar phenomenal character. Ozone oxidation was most effective in removing both colloidal phase and soluble phase EDCs, whereas CS displayed a relatively adequate performance in reducing colloidal EDCs. EDCs with lower Kow values exhibited higher removal by ion exchange resin. The combination of modified NDMP and ozonation processes achieved the best performance in reducing estrogenic activity and satisfying the predicted no-effect concentration (PNEC).

Enhanced coagulation of low-turbidity micro-polluted surface water: Properties and optimization

Micro-polluted surface water with low turbidity and low content of dissolved organic matter (DOM) is usually inefficiently purified. In this work, a combined technique for the enhanced coagulation of this surface water was proposed and investigated using cationic grafted starch (St-G) and polyaluminum chloride (PACl) as co-coagulants, followed by a magnetic ion-exchange resin (MIER). St-G was fed before PACl, and this procedure not only efficiently removes turbidity but also largely reduces the doses of the two coagulants. MIER remarkably removed DOM, and raw water was effectively purified. The entire coagulation process was further optimized through response surface methodology based on a central composite design by using the doses of St-G, PACl, and MIER as input variables. The dose effects of the three chemicals on the coagulation performance for turbidity and DOM removal were examined, and the coagulation mechanisms, including the interactive effect among various chemicals, were discussed in detail. This work provided a new strategy for the efficient treatment of low-turbidity micro-polluted surface water by utilizing organic and inorganic co-coagulants with magnetic ion-exchange resin in practical applications.

Antibiotic Resistome Alteration by Different Disinfection Strategies in a Full-Scale Drinking Water Treatment Plant Deciphered by Metagenomic Assembly

Disinfection regimes are considered the most solid strategy to reduce microbial risks in drinking water, but their roles in shaping the antibiotic resistome are poorly understood. This study revealed the alteration of antibiotic resistance genes (ARGs) profiles, their co-occurrence with mobile genetic elements (MGEs), and potential hosts during drinking water disinfection based on metagenomic assembly. We found the ozone/chlorine (O₃/Cl₂) coupled disinfection significantly increased the relative abundance of ARGs and MGE-carrying antibiotic resistance contigs (ARCs) through the enrichment of ARGs within the resistance-nodulation-cell division and ATP-binding cassette antibiotic efflux families that are primarily carried by Pseudomonas, Acinetobacter, Mycobacterium, and Methylocystis, whereas the antimicrobial resin/chlorine coupled disinfection posed unremarkable changes to the ARG and MGE abundances. Moreover, the co-occurrence patterns of antibiotic efflux and beta-lactam ARGs and MGEs were widely identified, and ARCs carrying the recR and mexH genes were detected in all the samples, with the highest abundance of 2.25 × 10^-2 copies per cell after O₃/Cl₂ disinfection. Sequence-independent binning analysis successfully retrieved two draft ARG-carrying genomes of Acidovorax sp. MR-S7 and Hydrogenophaga sp. IBVHS2, further revealing the host-ARG relationship during O₃/Cl₂ disinfection. Overall, this study provides novel insights into the antibiotic resistome alteration during drinking water disinfection.

A critical review on recent advancements of the removal of reactive dyes from dyehouse effluent by ion-exchange adsorbents

The effluent discharged by the textile dyehouses has a seriously detrimental effect on the aquatic environment. Some dyestuffs produce toxic decomposition products and the metal complex dyes release toxic heavy metals to watercourses. Of the dyes used in the textile industry, effluents containing reactive dyes are the most difficult to treat because of their high water-solubility and poor absorption into the fibers. A range of treatments has been investigated for the decolorization of textile effluent and the adsorption seems to be one of the cheapest, effective and convenient treatments. In this review, the adsorbents investigated in the last decade for the treatment of textile effluent containing reactive dyes including modified clays, biomasses, chitin and its derivatives, and magnetic ion-exchanging particles have been critically reviewed and their reactive dye binding capacities have been compiled and compared. Moreover, the dye binding mechanism, dye sorption isotherm models and also the merits/demerits of various adsorbents are discussed. This review also includes the current challenges and the future directions for the development of adsorbents that meet these challenges. The adsorption capacities of adsorbents depend on various factors, such as the chemical structures of dyes, the ionic property, surface area, porosity of the adsorbents, and the operating conditions. It is evident from the literature survey that decolorization by the adsorption shows a great promise for the removal of color from dyehouse effluent. If biomasses want to compete with the established ion-exchange resins and activated carbon, their dye binding capacity will need to be substantially improved.

The '333' integrated strategy for effective pollution control and its application to the heavily polluted Jialu River in north China

In this study, an integrated approach named the '333' strategy was applied to pollution control in the Jialu River, in northern China, which is heavily burdened with anthropogenic pollution. Due to a deficiency of the natural ecological inflow, the Jialu River receives predominantly industrial and municipal effluent. The '333' strategy is composed of three steps of pollution control including industrial point-source pollution control, advanced treatment of municipal wastewater, and ecological restoration; three increased stringency emission standards; and three stages of reclamation. Phase 1 of the '333' strategy focuses on industrial point-source pollution control; phase 2 aims to harness municipal wastewater and minimize sewage effluents using novel techniques for advanced water purification; phase 3 of the '333' strategy focuses on the further purification of effluents flowing into Jialu River with the employment of an engineering-based ecological restoration project. The application of the '333' strategy resulted in the development of novel techniques for water purification including modified magnetic resins (NDMP resin), a two-stage internal circulation anaerobic reactor (IC reactor) and an ecological restoration system. The results indicate that water quality in the river was significantly improved, with increased concentrations of dissolved oxygen (DO), as well as reduction of COD by 42.8% and NH₃-N by 61.4%. In addition, it was observed that the total population of phytoplankton in treated river water notably increased from only one prior to restoration to 8 following restoration. This system also provides a tool for pollution control of other similar industrial and anthropogenic source polluted rivers.

Fate of artificial sweeteners through wastewater treatment plants and water treatment processes

Five full-scale wastewater treatment plants (WWTPs) in China using typical biodegradation processes (SBR, oxidation ditch, A²/O) were selected to assess the removal of four popular artificial sweeteners (ASs). All four ASs (acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharin (SAC)) were detected, ranging from 0.43 to 27.34μg/L in the influent. Higher concentrations of ASs were measured in winter. ACE could be partly removed by 7.11–50.76% through biodegradation and especially through the denitrifying process. The A²/O process was the most efficient at biodegrading ASs. Adsorption (by granular activated carbon (GAC) and magnetic resin) and ultraviolet radiation-based advanced oxidation processes (UV/AOPs) were evaluated to remove ASs in laboratory-scale tests. The amounts of resin adsorbed were 3.33–18.51 times more than those of GAC except for SUC. The adsorption ability of resin decreased in the order of SAC > ACE > CYC > SUC in accordance with the pKa. Degradation of ASs followed pseudo-first-order kinetics in UV/H₂O₂ and UV/PDS. When applied to the secondary effluent, ASs could be degraded from 30.87 to 99.93% using UV/PDS in 30 minutes and UV/PDS was more efficient and economic.

Effect of pore structure on the removal of clofibric acid by magnetic anion exchange resin

The effect of pore structure of resin on clofibric acid (CA) adsorption behavior was investigated by using magnetic anion exchange resins (ND-1, ND-2, ND-3) with increasing pore diameter by 11.68, 15.37, 24.94 nm. Resin with larger pores showed faster adsorption rates and a higher adsorption capacity because the more opened tunnels provided by larger pores benefit the CA diffusion into the resin matrix. The ion exchange by the electrostatic interactions between Cl-type resin and CA resulted in chloride releasing to the solution, and the ratio of released chloride to CA adsorption amount decreased from 0.90 to 0.65 for ND-1, ND-2 and ND-3, indicating that non-electrostatic interactions obtain a larger proportional part of the adsorption into the pores. Co-existing inorganic anions and organic acids reduced the CA adsorption amounts by the competition effect of electrostatic interaction, whereas resins with more opened pore structures weakened the negative influence on CA adsorption because of the existence of non-electrostatic interactions. 85.2% and 65.1% adsorption amounts decrease are calculated for resin ND-1 and ND-3 by the negative influence of 1 mmol L^-1 NaCl. This weaken effect of organic acid is generally depends on its hydrophobicity (Log Kow) for carboxylic acid and its ionization degree (pKb) for sulfonic acid. The resins could be reused with the slightly decreases by 1.9%, 3.2% and 5.4% after 7 cycles of regeneration, respectively for ND-1, ND-2 and ND-3, suggesting the ion exchange resin with larger pores are against its reuse by the brine solution regeneration.

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.

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.

Comparison of different advanced treatment processes in removing endocrine disruption effects from municipal wastewater secondary effluent

In this study, secondary effluent from the Wulongkou (WLK) municipal wastewater plant (Zhengzhou, China) was tested for its toxicity effects before and after five advanced treatment processes (ATPs, i.e. coagulation sedimentation, nan da magnetic polyacrylic anion exchange resin (NDMP) resin adsorption, activated carbon adsorption, ozonation and electro-adsorption). Results showed that estrogen disruption effects (EDEs) were particularly significant for the raw secondary effluent among the studied dioxin-like toxicity effect, androgenic/anti-androgenic response effect, EDEs, and genotoxicity effect. And E1, E2, and EE2 were the main endocrine disruption chemicals (EDCs) contributing to EDEs. Except coagulation sedimentation, all the other four ATPs were efficient in removing the steroid estrogens (i.e. E1, E2, and EE2), but were inefficient in the artificial EDC (i.e. DBP, OP and BPA) removal. In the ATPs treated samples, vitellogenin (VTG) in zebrafish were largely removed. However, they were still significant in comparison with the control, probably due to artificial EDCs. Therefore, finding ways to thoroughly remove EDEs and EDCs from the secondary effluent will be a new research direction in the future.

Effect of humic acid on ciprofloxacin removal by magnetic multifunctional resins

Background organic matter significantly influences the removal of emerging contaminants in natural water. In this work, the adsorption of ciprofloxacin (CPX) onto a series of magnetic multifunctional resins (GMA10-GMA90) in the presence and absence of humic acid (HA) was conducted to demonstrate the effect of HA. Both hydrophobic and ion exchange interactions contributed to CPX adsorption. Negative charge-assisted hydrogen bonds also participated in the adsorption process, resulting in the high adsorption amount of anionic CPX onto the negatively charged GMA30 under basic solutions. HA could impact CPX adsorption not only as a competitive adsorbate but also as an additional adsorbent. At pH 5.6, the additional adsorption sites provided by adsorbed HA molecules on the resins dominated and thus facilitated the adsorption process. While at pH 10, HA inhibited the adsorption of CPX by directly competing for ion exchange sites and coexisting with CPX in the solution. The ratio of the amount of CPX adsorbed by dissolved HA to that by the resin reached as high as 1.61 for GMA90. The adsorbed HA molecules onto the resins could provide additional adsorption sites for CPX as proven by the enhanced CPX adsorption in HA-preloading systems at pH 5.6.