Simultaneous removal of nitrate nitrogen and orthophosphate by electroreduction and electrochemical precipitation.

Electrochemical methods can effectively remove nitrate nitrogen (NO3-N) and orthophosphate phosphorus (PO4-P) from wastewater. This work proposed a process for the simultaneous removal of NO3-N and PO4-P by combining electroreduction with electrochemically-induced calcium phosphate precipitation, and its performance and mechanisms were studied. For the treatment of 100 mg L-1 NO3-N and 5 mg L-1 PO4-P, NO3-N removal of 60-90% (per cathode area: 0.25-0.38 mg h-1 cm-2) and 80-90% (per cathode area: 0.33-0.38 mg h-1 cm-2) could be acquired within 3 h in single-chamber cell (SCC) and dual-chamber cell (DCC), while P removal was 80-98% (per cathode area: 0.10-0.12 mg h-1 cm-2) in SCC after 30 min and 98% (per cathode area: 0.37 mg h-1 cm-2) in DCC within 10 min. The faster P removal in DCC was due to the higher pH and more abundant Ca2+ in the cathode chamber of DCC, which was caused by the cation exchange membrane (CEM). Interestingly, NO3-N reduction enhanced P removal because more OH- can be produced by nitrate reduction than hydrogen evolution for an equal-charge reaction. For 10 mg L-1 PO4-P in SCC, when the initial NO3-N was 0, 20, 100, and 500 mg L-1, the P removal efficiencies after 1 h treatment were < 10%, 45-55%, 86-99%, and above 98% respectively. An increase in Ca2+ concentration also promoted P removal. However, Ca and P inhibited nitrate reduction in SCC at the relatively low initial Ca/P, as CaP on the cathode limited the charge or mass transfer process. The removal efficiency of NO3-N in SCC after 3 h reaction can reduce by about 17%, 40%, and 34% for Co3O4/Ti, Co/Ti, and TiO2/Ti. The degree of inhibition of P on NO3-N removal was related to the content and composition of CaP deposited on the cathode. On the cathode, the lower the deposited Ca and P, and the higher the deposited Ca/P molar ratio, the weaker the inhibition of P on NO3-N removal. Especially, P had little or even no inhibition on nitrate reduction when treated in DCC instead of SCC or under high initial Ca/P. It is speculated that under these conditions, a high local pH and local high concentration Ca2+ layer near the cathode led to a decrease in CaP deposition and an increase in Ca/P molar ratio on the cathode. High initial concentrations of NO3-N might also be beneficial in reducing the inhibition of P on nitrate reduction, as few CaP with high Ca/P molar ratios were deposited on the cathode. The evaluation of the real wastewater treatment was also conducted.

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.

Preparation of Graphite-UiO-66(Zr)/Ti electrode for efficient electrochemical oxidation of tetracycline in water.

Tetracycline (TC) is widely-used antibiotic pollutant with high toxicity, refractory, persistence and bacteriostasis, and its removal from water needs to be enhanced. In this work, a novel Graphite-UiO-66(Zr)/Ti electrode was successfully prepared and evaluated for electrochemical oxidation degradation of TC. The electrochemical performance tests indicate the Graphite-UiO-66(Zr)/Ti electrode had higher electrochemical oxidation activity, which achieved higher TC removal efficiency (98.1% ± 1.5%) than Ti plate (65.2% ± 3.5%), Graphite-MIL-53(Al)/Ti electrode (79.5% ± 2.9%) and Graphite-MIL-100(Fe)/Ti electrode (89.0% ± 2.6%). The influence of operating condition was also systematically studied, and the optimized condition was pH 5.0, 20 mA/cm2 current density and 0.1 M electrolyte (Na2SO4). Through the liquid chromatography mass spectrometry (LC-MS), the TC degradation pathway by Graphite-UiO-66(Zr)/Ti electrode oxidation was proposed. Under the •OH free radical oxidative decomposition effect, the double bond, phenolic group and amine group of TC were attacked. TC was transformed into intermediate product ① (m/z = 447), then was further degraded to intermediates ② (m/z = 401) and ③ (m/z = 417). The latter was fragmented into small fractions ④ (m/z = 194), ⑤but-2-enedioic acid (m/z = 116) and ⑥oxalic acid (m/z = 90, the proposed intermediate). In addition, TC removal remained at 89.6% ± 2.7% in the sixth cycle of operation, which confirmed the efficient reusability and stability for antibiotics removal from water.

The key role of hydrophobicity in the determination of pharmaceuticals by liquid chromatography-electrospray ionization-mass spectrometry under the interference of natural organic matter.

The determination of trace-level pharmaceuticals in water is generally performed using liquid chromatography combined with mass spectrometry, which is susceptible to interference from non-target substances, such as natural organic matter (NOM). In this study, the interference of NOM on the determination of 20 typical pharmaceuticals using solid-phase extraction followed by ultra-performance liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (UPLC-ESI-tqMS) was investigated with a combined consideration of recoveries, matrix effects, and process efficiencies. The results showed that the recoveries of most pharmaceuticals were not significantly affected by NOM concentrations of 1-50 mg/L. The matrix effects and process efficiencies decreased linearly with increasing logarithmic NOM concentrations, and the changes in matrix effects and process efficiencies both exhibited negative linear correlations with the pharmaceuticals' hydrophobicity (logKow). This result indicated that the determination of hydrophilic pharmaceuticals suffered from more severe NOM interference, as NOM entered the ESI source together with hydrophilic pharmaceuticals after UPLC separation and subsequently weakened the ionization efficiency of these pharmaceuticals. According to the correlations between logKow and the changes in matrix effects and process efficiencies, the pharmaceutical determination in positive/negative ESI modes with logKow ≤ 3.80/4.27 is considered to be significantly affected by NOM, accompanied by > 20% changes in matrix effects and process efficiencies.

Improved mineralization and total nitrogen reduction by combination of electro-reduction and electro-oxidation for nitrophenol removal.

In this work, p-Nitrophenol (p-NP) was electro-chemically removed by using a prepared Co3O4/Ti cathode and a BDD anode to achieve the simultaneous reduction of total organic carbon (TOC), total nitrogen (TN) and toxicity. The prepared Co3O4/Ti cathode showed higher electro-activity than the Ti cathode towards p-NP reduction with the removal rate higher than 90.6% but without mineralization. The electro-oxidation removed 84.3% of TOC but none of TN. To develop an optimized process for mineralization and TN removal during p-NP electrolysis, the combination of electro-oxidation and electro-reduction were evaluated by using a dual-chamber cell and a single-chamber cell, respectively. As a result of the re-oxidation and re-reduction in the single-chamber cell, the typically used mode of the simultaneous redox, showed a lower removal of TOC and TN than the combination processes as well as an increased toxicity. The TN removal for both combined modes (21.0%-32.9%) was all higher than that of the mode of reduction because the produced inorganic nitrogen such as ammonia and nitrate could be partially oxidized or reduced to nitrogen gas. The results suggested that the combination process could significantly improve the mineralization and TN reduction for p-NP removal, accompanied with 60.3% decrease of acute toxicity for the reduction after oxidation mode.

Effect of ammonia on acute toxicity and disinfection byproducts formation during chlorination of secondary wastewater effluents.

Ammonia nitrogen (NH3-N) significantly affects the occurrence of disinfection byproducts (DBPs) and residual chlorine in chlorinated wastewater, thereby affecting the acute toxicity to aquatic organisms. In this paper, the formation of thirty-five halogenated DBPs and the changes in acute toxicity of luminescent bacteria and zebrafish embryos were evaluated after chlorination of seven secondary wastewater effluents with different NH3-N concentrations. Results showed that NH3-N significantly reduced the formation of most DBPs by 82-100%. The acute toxicity was enhanced after chlorination and increased linearly with increasing NH3-N concentration for luminescent bacteria (r = 0.986, p < 0.05) and zebrafish embryos (r = 0.972, p < 0.05) due to the coexistence of DBPs and monochloramine. According to the toxicity classification system of wastewater, the fitting results indicated that the toxicity level was acceptable for chlorinated wastewater with NH3-N concentration below 1.00 mg-N/L. DBPs might be the main toxicant to luminescent bacteria in the wastewater with low NH3-N concentrations (0.06-0.31 mg-N/L), which accounted for 68-97% of the toxicity contribution. By contrast, monochloramine contributed over 80% to the toxicity of luminescent bacteria and zebrafish embryos in the wastewater with high NH3-N concentrations (2.66-7.17 mg-N/L). Compared to chlorination, chlorine dioxide and ultraviolet disinfection unaffected by NH3-N could reduce acute toxicity by nearly 100%, primarily due to the lack of residual disinfectant. In view of the high toxicity caused by chlorination, chlorination-dechlorination or chlorine dioxide and UV disinfection are highly recommended for the treatment of wastewater with high NH3-N concentration.

Comparative Toxicity Analyses from Different Endpoints: Are New Cyclic Disinfection Byproducts (DBPs) More Toxic than Common Aliphatic DBPs?

In recent years, dozens of halogenated disinfection byproducts (DBPs) with cyclic structures were identified and detected in drinking water globally. Previous in vivo toxicity studies have shown that a few new cyclic DBPs possessed higher developmental toxicity and growth inhibition rate than common aliphatic DBPs; however, in vitro toxicity studies have proved that the latter exhibited higher cytotoxicity and genotoxicity than the former. Thus, to provide a more comprehensive toxicity comparison of DBPs from different endpoints, 11 groups of cyclic DBPs and nine groups of aliphatic DBPs were evaluated for their comparative in vitro and in vivo toxicity using human hepatoma cells (Hep G2) and zebrafish embryos. Notably, results showed that the in vitro Hep G2 cytotoxicity index of the aliphatic DBPs was nearly eight times higher than that of the cyclic DBPs, whereas the in vivo zebrafish embryo developmental/acute toxicity indexes of the cyclic DBPs were roughly 48-50 times higher than those of the aliphatic DBPs, indicating that the toxicity rank order differed when different endpoints were applied. For a broader comparison, a Pearson correlation analysis of DBP toxicity data from nine different endpoints was conducted. It was found that the observed Hep G2 cytotoxicity and zebrafish embryo developmental/acute toxicity in this study were highly correlated with the previously reported in vitro CHO cytotoxicity and in vivo toxicity in aquatic organisms (P < 0.01), respectively. However, the observed in vitro toxicity had no correlation with the in vivo toxicity (P > 0.05), suggesting that the toxicity rank orders obtained from in vitro and in vivo bioassays had large discrepancies. According to the observed toxicity data in this study and the candidate descriptors, two quantitative structure-activity relationship (QSAR) models were established, which help to further interpret the toxicity mechanisms of DBPs from different endpoints.

[Effects of Fe3O4 on the denitrification performance of Pseudomonas stutzeri].

Biological denitrification is the most widely used technology for nitrate removal in wastewater treatment. Conventional denitrification requires long hydraulic retention time, and the nitrate removal efficiency in winter is low due to the low temperature. Therefore, it is expected to develop new approaches to enhance the denitrification process. In this paper, the effect of adding different concentrations of Fe3O4 nanoparticles on the denitrification catalyzed by Pseudomonas stutzeri was investigated. The maximum specific degradation rate of nitrate nitrogen improved from 18.0 h⁻¹ to 23.7 h⁻¹ when the concentration of Fe3O4 increased from 0 mg/L to 4 000 mg/L. Total proteins and intracellular iron content also increased along with increasing the concentration of Fe3O4. RT-qPCR and label-free proteomics analyses showed that the relative expression level of denitrifying genes napA, narJ, nirB, norR, nosZ of P. stutzeri increased by 55.7%, 24.9%, 24.5%, 36.5%, 120% upon addition of Fe3O4, and that of denitrifying reductase Nap, Nar, Nir, Nor, Nos increased by 85.0%, 147%, 16.5%, 47.1%, 95.9%, respectively. No significant difference was observed on the relative expression level of denitrifying genes and denitrifying reductases between the bacteria suspended and the bacteria adhered to Fe3O4. Interestingly, the relative expression level of electron transfer proteins of bacteria adhered to Fe3O4 was higher than that of the bacteria suspended. The results indicated that Fe3O4 promoted cell growth and metabolism through direct contact with bacteria, thereby improving the denitrification. These findings may provide theoretical support for the development of enhanced denitrification.

Organic micropollutants and disinfection byproducts removal from drinking water using concurrent anion exchange and chlorination process.

Many traditional drinking water treatment processes have limited removal efficiencies on natural organic matter (NOM) and organic micropollutants (OMPs), and thus may lead to the production of harmful disinfection byproducts (DBPs). We examined four kinds of anion exchange resins (D205, D213, NDMP-3, and M80) in conjunction with chlorination in the treatment of drinking water. Five categories including 40 OMPs at environmentally relevant concentrations were analyzed. M80 showed the best performance to remove OMPs in water. However, it was vulnerable to the presence of humic acid (HA), indicating its limitation on removing OMPs and NOM at the same time. In contrast, D205, D213, NDMP-3 resins were less affected by HA. Besides, D205, D213 and NDMP-3 provided higher efficiencies on the reduction of DBPs than M80. The amount of trihalomethanes (THMs) lowered by 42.7%, 37.6%, 32.1%, and 0%, whereas haloacetic acids (HAAs) were decreased by 34.0%, 31.2%, 23.0%, and 17.9% by D205, D312, NDMP-3, and M80. Notably, D205 showed the highest removal effects on the bromide ion, brominated THMs, and HAAs, supporting that D205 can be a selective resin for the treatment of drinking water in high bromide-containing areas.

The improvement on total nitrogen removal in nitrate reduction by using a prepared CuO-Co3O4/Ti cathode.

In this work, a CuO-Co3O4/Ti composite was prepared via the coating-calcination method and employed as a cathode for the NO3--N reduction to increase the removal efficiency of total nitrogen (TN). SEM, EDS, and XRD characterization results indicated that CuO and Co3O4 were successfully introduced to the surface of Ti. The CuO-Co3O4/Ti electrode eventually removed NO3--N with the main products of N2, NH4+-N and NO2--N. In comparison to the Co3O4/Ti electrode, the better hydrogen evolution properties of the CuO-Co3O4/Ti electrode resulted in pH increase and NH3 gas release, so the TN removal for CuO-Co3O4/Ti electrode was improved approximately 20%. The presence of Cl- with the concentration up to 1000 mg L-1 greatly promoted the removal of TN from 40.1% to 94.0%, as a result of NH4+-N oxidation with free chlorine produced from the anode. Furthermore, the CuO-Co3O4/Ti electrode was applied to conduct three types of actual wastewater (biological effluent of municipal wastewater and industrial wastewater, and a regeneration concentrate from an anion exchange process) for nitrate removal. The highest TN removal efficiency (78.5%) and current efficiency (54.5%), and the lowest energy consumption (2 × 10-4 kWh mg-1 TN) were obtained for the regeneration concentrate, suggesting the feasibility of the CuO-Co3O4/Ti electrode to the water with high conductivity and high Cl- concentration for removing TN by the reduction of nitrate.

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.

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.

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.

New phenolic halogenated disinfection byproducts in simulated chlorinated drinking water: Identification, decomposition, and control by ozone-activated carbon treatment.

Recently, 13 new phenolic halogenated disinfection byproducts (DBPs) were discovered and confirmed in chlorinated drinking water using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry (UPLC/ESI-tqMS), which have been attracting a growing concern due to their higher chronic cytotoxicity, developmental toxicity, and growth inhibition compared with commonly known aliphatic DBPs. In this study, another 12 new phenolic halogenated DBPs were detected and identified in simulated chlorinated drinking water samples, including two monohalo-4-hydroxybenzaldehydes, two monohalo-4-hydroxybenzoic acids, three monohalo-salicylic acids, and five mono/di/trihalo-phenols. Decomposition mechanisms of these new phenolic halogenated DBPs during chlorination were speculated and partially verified by identifying intermediate products. These new DBPs could undergo hydrolysis, halogenation, substitution, addition, decarboxylation, and rearrangement reactions to form a series of decomposition products, including dihaloacetic acids, 2-halomaleic acids, and a group of new heterocyclic DBPs (trihalo-hydroxy-cyclopentene-diones). A bench-scale ozone-granular activated carbon (GAC) treatment unit was designed and set up in the lab. It was found that ozonation and GAC filtration were effective in reducing dissolved organic carbon levels and aromaticity (DBP precursors) of simulated raw water samples, and thus were effective in decreasing the concentrations of these new phenolic DBPs by 82.5% and 88.6%, respectively. Furthermore, four different treatment scenarios (i.e., ozonation, GAC filtration, ozonation followed by GAC filtration, and GAC filtration followed by ozonation) were evaluated and compared. Results showed that ozonation followed by GAC filtration was most effective in precursor removal and could decrease the level of these new phenolic DBPs by up to 97.3%.

The effect on ozone catalytic performance of prepared-FeOOH by different precursors.

In this study, different precursors were used to prepare FeOOH and the ozonation catalytic activity was s investigate by using ibuprofen as the degradation substrate. It could be found that FeOOH prepared from ferric sulfate performed higher activity. Subsequently, the catalysts were characterized by X-ray diffraction, Fourier transform infrared spectrometer, scanning electron microscope and N2 adsorption-desorption techniques. X-ray diffraction and Fourier transform infrared spectrometer showed that the synthesized FeOOH consisted of α-FeOOH and ß-FeOOH mainly. Scanning electron microscope showed that their appearance and morphology were significantly different, and the FeOOH prepared from ferric sulfate had a larger specific surface area, resulting in its better catalytic activity. Finally, the hydroxyl groups and pHzpc of the catalyst surface were measured. It was also found that the FeOOH prepared from ferric sulfate owned more hydroxyl groups and the pHzpc of the surface was closer to the pH of the degradation substrate, which illustrated the reasons for the increased catalytic activity. In addition, the degradation kinetics conformed to the pseudo first-order kinetic model and the hydroxyl radicals played an important role in the reaction process.

[Bioregeneration of Anion Exchange Resin Used in Nitrate Removal].

Anion exchange resin is a feasible adsorbent for nitrate removal because of its high efficiency and cost-effectiveness, but brine regeneration complicates subsequent wastewater procedures. Bioregeneration degrades the nitrate from the nitrate-laden resin, which can decrease brine solution usage and waste discharge. In this study, based on investigation of the effect of carbon source, for example, glucose, sodium acetate, sodium lactate, and methanol, on bioregeneration, nitrate-laden resin was employed to investigate the effects of inoculum amount and salt concentration on bioregeneration with sodium acetate as the carbon source. The results showed that the bioregeneration process comprised chemical desorption and biological denitrification and was limited by the biological process. With increasing inoculum amount, the bioregeneration time was remarkably reduced. Nitrate on the resin could be completely biodegraded within 10 h when the inoculum amount (measured as VSS) was higher than 0.6 g·L-1. Furthermore, higher NaCl concentrations improved the chemical desorption of nitrate, resulting in a sharp increase in soluble nitrate. However, the denitrification process of bioregeneration was also eventually limited by the biological process. When the concentration of NaCl was higher than 20 g·L-1, bioactivity of the denitrifying bacteria was limited and the bioregeneration time increased to more than 10 h. The result of multi-cycle adsorption-bioregeneration experiment showed that the NO3--N adsorption capacity of bioregenerated resin was stable at 30-35 mg·g-1.

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.

Detection, formation and occurrence of 13 new polar phenolic chlorinated and brominated disinfection byproducts in drinking water.

Recently, 13 new polar phenolic chlorinated and brominated disinfection byproducts (Cl- and Br-DBPs) were identified and quantified in simulated chlorinated drinking water by adopting product ion scan, precursor ion scan, and multiple reaction monitoring (MRM) analyses using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry (UPLC/ESI-tqMS). The 13 new DBPs have been drawing increasing concern not only because they possess significantly higher growth inhibition, developmental toxicity, and chronic cytotoxicity than commonly known aliphatic DBPs, but also because they act as intermediate DBPs that can decompose to form the U.S. EPA regulated DBPs. In this study, through MS parameter optimization of the UPLC/ESI-tqMS MRM analysis, the instrument detection and quantitation limits of the 13 new DBPs were substantially lowered to 0.42-6.44 and 1.35-16.51 µg/L, respectively. The total levels of the 13 new DBPs formed in chlorination were much higher than those formed in chloramination within a contact time of 3 d. In chlorination, the 13 new DBPs formed quickly and decomposed rapidly, and their total concentration kept on decreasing with contact time. In chloramination, the levels of the dominant species (i.e., trihalo-phenols) firstly increased and then decreased with contact time, whereas the levels of the other new DBPs were relatively low and kept on increasing with contact time. An increasing of pH from 6.0 to 9.0 decreased the formation of the 13 new DBPs by 57.8% and 62.3% in chlorination and chloramination, respectively. Gallic acid was found to be present in various simulated and real source water samples and was demonstrated to be a precursor of the 13 new DBPs with elucidated formation pathways. Furthermore, 12 of the 13 new DBPs were detected in 16 tap water samples obtained from major cities in East China, at total levels from 9.5 to 329.8 ng/L. The concentrations of the new DBPs were higher in samples with source waters containing higher bromide levels. Ozone-activated carbon treatment prior to disinfection might reduce the formation of the new DBPs since it was effective in precursor reduction.