Enhanced Selective Electrosorption of Nitrate from Wastewater by Controllably Doping Nitrogen into Porous Carbon with Micropores.

The biological NO3- removal process might be accompanied by high CO2 emissions and operation costs. Capacitive deionization (CDI) has been widely studied as a very efficient method to purify water. Here, a porous carbon material with a tunable nitrogen configuration was developed. Characterization and density functional theory calculation show that nitrogenous functional groups have a higher NO3- binding energy than Cl-, SO42-, and H2PO4-. In addition, the selectivity of NO3- is improved after the introduction of micropores by using the pore template. The NO3- ion removal and selectivity of MN-C-12 are 4.57 and 3.46-5.42 times that of activated carbon (AC), respectively. The high NO3- selectivity and electrosorption properties of MN-C-12 (the highest N content and micropore area) are due to the synergistic effect of the affinity of nitrogen functional groups to NO3- and microporous ion screening. A CDI unit for the removal of nitrogen from municipal wastewater was constructed and applied to treat wastewater meeting higher discharge standards of A (N: 15 mg L-1) and B (N: 20 mg L-1) ((GB18918-2002), China). This work provides new insights into enhanced carbon materials for the selective electrosorption of wastewater by CDI technology.

MOF-Derived Ni/ZIF-8/ZnO Arrays on Carbon Fiber Cloth for Efficient Adsorption-Catalytic Oxidation.

The catalytic oxidation of toxic organic pollutants in water requires enhanced efficiency for commercial applications. A ZnO nanorod array grown on a carbon fiber cloth (CFC) serves as the zinc source to ensure that the Ni/ZIF-8/ZnO nanoreactor is constructed. The Ni/ZIF-8/ZnO/CFC nanoreactor efficiently activates peroxymonosulfate (PMS) for bisphenol A (BPA) degradation owing to its high density of active sites, high adsorbability, and dispersibility structure, which concentrates catalytic and adsorptive sites within a confined space. Experimental and theoretical calculations clearly show that the introduction of Ni is beneficial for improving the adsorption of BPA and the activation of PMS. The synergistic mechanism of BPA adsorption-PMS activation is also investigated, and the degradation pathway of BPA is examined. Moreover, a filter catalytic unit is constructed using Ni/ZIF-8/ZnO/CFC to achieve a continuous zero discharge of BPA, which is convenient for nanocatalyst recycling. This study aims to develop a new strategy for the removal of emerging organic pollutants from water using a system with strong adsorption and catalytic capabilities.

Heterogeneous Fe-Co dual-atom catalyst outdistances the homogeneous counterpart for peroxymonosulfate-assisted water decontamination: New surface collision oxidation path and diatomic synergy.

Heterogeneous catalysts lag far behind their homogeneous counterparts in activating peroxymonosulfate (PMS) for water decontamination due to the low site intrinsic activity and sluggish mass transfer. The single-atom catalyst can bridge the gap between heterogeneous and homogeneous catalysts, but the difficulty to break scaling relations originating from the site monotony restricts further efficiency upgradation. Herein through modulating the crystallinity of NH2-UIO-66, a porous carbon support with ultrahigh surface area (1721.71 m2 g-1) is obtained to anchor the dual-atom FeCoN6 site, which exhibits superior turnover frequency over single-atom FeN4 and CoN4 sites (13.07 versus 9.97, 9.07 min-1). The as-synthesized composite thus outperforms the homogeneous catalytic system (Fe3++Co2+) for sulfamethoxazole (SMZ) degradation, and the catalyst-dose-normalized kinetic rate constant (99.26 L min-1 g-1) exceeds reported values by 1∼2 orders of magnitude. Moreover, only 20 mg of the catalyst can run a fluidized-bed reactor to realize continuous zero discharge of SMZ in multiple actual waters for up to 8.33 h. Unlike all reported reaction routes, the catalysis on the diatomic site follows a new surface collision oxidation path, i.e. the dispersed catalyst adsorbs PMS to generate surface-activated PMS with high potential, which collides with surrounding SMZ and directly seizes electron from it to induce pollutant oxidation. Theoretical calculation indicates that the enhanced activity of FeCoN6 site stems from the diatomic synergy, leading to stronger PMS adsorption, larger near-Fermi-level density of states and optimal global Gibbs free energy evolution. Overall, this work provides an effective strategy of constructing heterogeneous dual-atom catalyst/PMS process to achieve faster pollution control than homogeneous system, and sheds light on the interatomic synergetic mechanism for PMS activation.

Renewable Adsorbents for Selective Phosphorus Removal: Co(OH)2-Derived ZIF-67 on Anion Exchange Resin.

Metal organic framework (MOF)-based adsorbents are appealing for removing low-concentration phosphates with interfering ions in wastewater purification, a new strategy developed to maintain the good activity of metal sites. Here, ZIF-67 was immobilized onto the porous surface of anion exchange resin (D-201) with a high loading amount of 22.0 wt % by a modifiable Co(OH)2 template. We observed that the removal rate of low-concentration phosphate (2 mg P/L) by ZIF-67/D-201 nanocomposites was 98.6%, and more than 90% phosphate adsorption capacity was still maintained, with 5 times molar concentration of interfering ions in the solution. Moreover, after six times of regeneration by solvothermal reaction in the ligand solution, the structure of ZIF-67 was better preserved in D-201 with more than 90% phosphate removal rate. ZIF-67/D-201 could be employed effectively in fixed-bed adsorption runs. By the analysis of experiment and characterization, we found that during the adsorption-regeneration process of ZIF-67/D-201 for phosphate, reversible structural transformation of ZIF-67 and Co3(PO4)2 occurred in D-201. In general, the study reported a new method to develop MOF adsorbents for wastewater treatment.

Protein-folding-inspired approach for UF fouling mitigation using elevated membrane cleaning temperature and residual hydrophobic-modified flocculant after flocculation-sedimentation pre-treatment.

Hydrophobic-modified flocculants have demonstrated considerable promise in the removal of emerging contaminants by flocculation. However, there is a lack of information about the impacts of dosing such flocculants on the performance of subsequent treatment unit(s) in the overall water treatment process. In this work, inspired by the ubiquitous protein folding phenomenon, an innovative approach using an elevated membrane cleaning temperature as the means to induce residual hydrophobic-modified chitosan flocculant (TRC), after flocculation-sedimentation, to reduce membrane fouling in a subsequent ultrafiltration was proposed; this was evaluated in a continuous flocculation-sedimentation-ultrafiltration (FSUF) process treating samples of the Yangtze River. The hydrophobic chains of TRC had similar temperature-dependent hydrophobicity to those of natural proteins. In the 40-day operation of the FSUF system with combined dosing of alum and TRC, a moderately elevated cleaning water temperature (45 °C) of both backwash with air-bubbling and soaking with sponge-scrubbing cleaning, significantly reduced reversible and irreversible fouling resistance by 49.8%∼61.3% and 73.9%∼83.3%, respectively, compared to the system using cleaning water at 25 °C. Material flow analysis, statistical analysis, instrumental characterizations, and computational simulations, showed that the enhanced fouling mitigation originated from three factors: the reduced contaminant accumulation onto membranes, the strengthened membrane-surface-modification role of TRC, and the weakened structure of the fouling material containing TRC, at the elevated cleaning temperature. Other measures of the performance, these being water purification, membrane stability and economic aspects, also confirmed the potential and feasibility of the proposed approach. This work has provided new insights into the role of hydrophobic-modified flocculants in membrane fouling control, in addition to emerging contaminant removal, in a FSUF surface water treatment process.

Enhanced removal of trace pesticides and alleviation of membrane fouling using hydrophobic-modified inorganic-organic hybrid flocculants in the flocculation-sedimentation-ultrafiltration process for surface water treatment.

Pesticide concentrations in surface water occasionally exceed regulated values due to seasonal events (rainy season in high intensity agricultural areas) or intermittent discharges (leakage, spillage, or other emergency events). The need to remove pesticide compounds in these situations poses a challenge for drinking water treatment plants (DWTPs). In this work, the performance of dosing hydrophobic-modified inorganic-organic hybrid flocculants (HOC-M; lower acute toxicity than corresponding metal salt coagulants; acceptable economic costs when M=Al or Fe; prepared in large-scale quantities), for the removal of four different pesticides (each initial concentration: 0.25 µg/L) from Yangtze River water, and in mitigating membrane fouling, by an integrated flocculation-sedimentation-ultrafiltration (FSUF) process, was evaluated over a period of 40 days; the FSUF is well-established in many DWTPs. The mechanisms underlying the treatment were unveiled by employing a combination of instrumental characterizations, chemical computations, material flow analyses, and statistical analyses. Efficient pesticide removal (80.3%∼94.3%) and membrane fouling reduction (26.6%∼37.3% and 28.3%∼57.6% for reversible and irreversible membrane resistance, respectively) in the FSUF process were achieved by dosing HOC-M, whereas conventional inorganic coagulants were substantially inferior for pesticide removal (< 50%) and displayed more severe fouling development. Hydrophobic association between the pesticides and the hydrophobic organic chain of HOC-M played a predominant role in the improvement in pesticide removal; coexisting particulate/colloid inorganic minerals and natural organic matter with HOC-M adsorbed on the surface, acting as floc building materials, provided sites for the indirect combination of pesticides into flocs. The observed fouling alleviation from dosing HOC-M was ascribed to both the pre-removal of fouling-causing materials in the flocculation-sedimentation prior to UF, and a stable hydrophilization modification effect of residual HOC-M in the UF unit. The latter effect resulted from a hydrophobic association between the PVDF substrate of the membranes and the hydrophobic organic chains of the HOC-M, causing the hydrophilic ends of the HOC-M to be exposed away from the membrane surface, thereby inhibiting foulant accumulation. This work has not only demonstrated the superior performance of dosing HOC-M in the FSUF process for trace pesticide removal in DWTPs, but also clarified the underlying mechanisms.

Defective MOFs-based electrocatalytic self-cleaning membrane for wastewater reclamation: Enhanced antibiotics removal, membrane fouling control and mechanisms.

In order to resolve the poor antibiotics rejection and serious fouling of ultrafiltration (UF) membrane during municipal wastewater reclamation, a novel anodic membrane (defective UiO-66 (D-UiO-66)/Graphite/Polyvinylidene fluoride (PVDF)) with high pure water flux (596.1 L•h - 1•m - 2•bar-1) was fabricated by incorporating defective zirconium based metal-organic framework (D-UiO-66) and conductive graphite particles into PVDF matrix and applied in the coupling of electro-oxidation and membrane filtration process. Compared to the other anodic membranes (i.e., Graphite/PVDF and UiO-66/Graphite/PVDF), D-UiO-66/Graphite/PVDF possesses superior anti-fouling and self-cleaning abilities (flux recovery=100%, model foulant: bovine serum albumin) in both intermittent and continuous supply of electric field under current density of 0.01 mA/cm2; moreover, efficient antibiotics (tetracycline, norfloxacin, tylosin and sulfamethoxazole) removal (> 96.6%) and bactericidal efficiency against E. coli and S. aureus (100%) were achieved simultaneously without the addition of chemical reagents due to the higher electrocatalytic activity of anodic membrane for oxidation of pollutants by •OH and •O2- free radicals. Three degradation pathways of antibiotics were proposed and the self-cleaning mechanism of membrane was dominated by the synergy of the partial mineralization and the reduced fouling potential of foulants after oxidation as revealed by the increase in hydrophilicity, and decrease in negative charge and molecular weight. The fabricated membrane also presents excellent electrochemical stability, separation and self-cleaning performance for treatment of municipal secondary effluent during long-term filtration with low electric energy consumption, which is promising in wastewater reclamation.

Influence of DOM characteristics on the flocculation removal of trace pharmaceuticals in surface water by the successive dosing of alum and moderately hydrophobic chitosan.

Hydrophobically-modified chitosan (HC) has emerged as a promising flocculant for trace pharmaceutical removal from surface water. However, the variation in the characteristics of dissolved organic matter (DOM) in different water sources influences the efficacy of HC in removing pharmaceutical compounds. In this work, the flocculation performance of sequentially dosing alum and HC (alum+HC) for the treatment of five water types (three synthetic waters, and samples of two real waters collected from the Yangtze River and the Thames River), having different DOM and five representative pharmaceuticals (initial concentration: 100 ng/L), was assessed by bench-scale jar tests. The DOM characteristics were correlated quantitatively with the removal efficiencies (REs) of the pharmaceuticals. Density functional theory computations were performed to illuminate the interfacial interactions in the flocculation. Alum+HC exhibited a remarkably higher RE of all five pharmaceuticals (maximum RE: 73%-95%) from all waters compared to a conventional coagulant or flocculant (alum or polyacrylamide, respectively). In contrast to using HC alone, alum+HC also achieved a higher RE of pharmaceuticals with nearly half the HC dosage, thereby enhancing the cost-effectiveness of the alum+HC dosing system. Among the different key DOM characteristics, the surface charge and molecular weight of DOM had no evident correlation with RE(pharmaceutical), but the hydrophobic/hydrophilic nature and functional group composition of organic carbon of DOM were strongly correlated: Strongly hydrophobic fractions, with C-C & C=C functional groups (binding pharmaceuticals via hydrophobic association), were beneficial, while hydrophilic fractions with C-OH groups were less effective, for pharmaceutical removal. This work showed the enhanced performance of the alum+HC dosing combination in the removal of different pharmaceutical compounds from different waters, and filled the knowledge gap regarding the performance of hydrophobically-modified flocculants in the treatment of different surface water sources.

Co-utilization of lake sediment and blue-green algae for porous lightweight aggregate (ceramsite) production.

Lake sediment and algal sludge with large output posed significant environmental risks. In this work, an idea of co-utilization of both solid wastes for the production of ceramsite (a sort of porous lightweight aggregates as building materials) was proposed and validated for the first time. The treatment process contained a dewatering step by a flocculation-pressure filtration method, and a sintered ceramsite preparation step. Effects of flocculant type and dosage on the dewatering performance were studied in the first step. An environmental-friendly amphoteric starch flocculant with a dosage of 12 mg/(g dried sample) was found to achieve the best dewatering performance. Effects of raw material mass ratio, sintering temperature and time in the second step were investigated. Under the optimal conditions (60 wt% of dewatered sediment; 20 wt% of dewatered algal sludge; 20 wt% of additives (fly ash: calcium oxide: kaolin = 2:1:2); sintering temperature: 1100 °C; time: 35 min), the obtained ceramsite met the Chinese National Standard as a qualified building material, with reliable environmental safety according to the leaching results for both heavy metals and microcystins. Both environmental and economic benefits of the proposed treatment were assessed. The process completely followed the rules of "reduction, harmlessness and resource utilization" for solid waste treatment and disposal; Meanwhile, the profit of the proposed ceramsite production could be more than 2.3 US dollar/m3. The co-utilization method in this work acted as a good example for the comprehensive management of solid wastes in water-rich areas.

Humic acid enhanced pyrene degradation by Mycobacterium sp. NJS-1.

The search for nature-based tools to enhance bioremediation is essential for the sustainable restoration of contaminated ecosystems. Humic acid (HA) is an important component of organic matter in soil and water, but its effect on the microbial degradation of organic pollutants remains unclear. In this study, the biodegradation of pyrene by Mycobacterium sp. NJS-1 with and without HA was investigated. Only around 10.5% of pyrene was biodegraded in the pyrene treatment alone, whereas the addition of HA significantly enhanced biodegradation to the point where over 90% of pyrene was biodegraded. The production of 4,5-dihydropyrene-4,5-diol and phenanthrene-3,4-diol indicated the metabolic pathway via attacking of 4,5-positions of pyrene. Interestingly, 1,2-dimethoxypyrene was detected with the addition of HA, suggesting that HA induced a new ring-opening pathway involving the attack on the 1,2-positions of pyrene. The addition of HA first induced protein self-cleavage behavior with a significant increase in phenylalanine, tyrosine, and tryptophan containing large numbers of COO- groups. Furthermore, it altered the intracellular and extracellular ultrastructure of bacterial cells, promoting their growth in size and number as well as reducing the space between them. Overall, HA increased the ring-opening positions of pyrene and facilitated its interaction with bacterial cells, thus improving its biodegradability. Building upon the findings of this study to further research is conducive to the sustainable solution of environmental pollution.

Effect of γ-Fe2O3 nanoparticles on the composition of montmorillonite and its sorption capacity for pyrene.

Fe content and distribution on montmorillonite would probably enhance its sorption capacity for hydrophobic organic pollutants. Thus, Fe modified montmorillonites with different ratios of FeSO4·7H2O and Ca-montmorillonite were prepared. The results indicated that γ-Fe2O3 nanoparticles were not only generated at the montmorillonite surfaces, but that the γ-Fe2O3 also extended the edges of montmorillonite surfaces. The sorption capacities for pyrene were enhanced and even reached 834.79 µg g-1 with increase in ferrous iron content, but were then suppressed due to aggregation of γ-Fe2O3 on montmorillonite surfaces. Furthermore, pyrene was directly observed on γ-Fe2O3-montmorillonite surfaces with a lattice spacing parameter of approximately 0.27 nm, indicating that a new phase that mainly contained pyrene was generated during the sorption process. Additionally, after regenerating the γ-Fe2O3-montmorillonite composites, they could be reused for at least 5 cycles. It is therefore proposed that the prepared γ-Fe2O3-montmorillonite could be exploited as a potential green composite for remediation of hydrophobic organic pollutants in soil and sediment.

Up-regulation of ribosomal and carbon metabolism proteins enhanced pyrene biodegradation in fulvic acid-induced biofilm system.

The polycyclic aromatic hydrocarbons (PAHs) that enter the aqueous phase usually coexist with fulvic acid (FA). Therefore, we initiated this investigation to explore the influences of FA on bacterial biofilm formation and its potential to biodegrade pyrene (PYR), using electron microscopic techniques and isobaric tags for relative and absolute quantification (iTRAQ). Our results revealed that FA stimulated biofilm formation and enhanced the biodegradation of PYR. First, FA favored the three-dimensional proliferation of bacteria, with an OD590/OD600 value of up to 14.78, and the extracellular surfaces covered by a layer of biomaterials. Distinctive intracellular morphologies of texture and organization were accompanied by reduced inter-bacterial distances of less than 0.31 µm. The biofilms formed displayed interactions between FA and surficial proteins, as noted by band shifts for the C-O and CO groups. Strikingly, FA triggered the upregulation of 130 proteins that were either operational in biofilm formation or in metabolic adjustments; with the changes supported by the increasing intensity of free amino acids and the newly generated N-O bonds. The results above revealed that the enhanced biodegradation was related to the up-regulation of the proteins functioned for ribosomal and carbon metabolism, and the ultra-structural changes in FA-induced biofilm system.

Improved utilization of active sites for phosphorus adsorption in FeOOH/anion exchanger nanocomposites via a glycol-solvothermal synthesis strategy.

Metal oxide/hydroxide-based nanocomposite adsorbents with porous supporting matrices have been recognized as efficient adsorbents for phosphorus recovery. Aiming at satisfying increasingly restrictive environmental requirements involving improving metal site utilization and lowering metal leakage risk, a glycol-solvothermal confined-space synthesis strategy was proposed for the fabrication of FeOOH/anion exchanger nanocomposites (Fe/900s) with enhanced metal site utilization and reduced metal leakage risk. Compared to composites prepared using alkaline precipitation methods, Fe/900s performed comparably, with a high adsorption capacity of 19.05 mg-P/g with an initial concentration of 10 mg-P/L, a high adsorption selectivity of 8.2 mg-P/g in the presence of 500 mg-SO42-/L, and high long-term resilience (with a capacity loss of ~14% after five cycles), along with substantially lower Fe loading amount (4.11 wt.%) and Fe leakage percentage. Mechanistic investigation demonstrated that contribution of the specific FeOOH sites to phosphate adsorption increased substantially (up to 50.97% under the optimal conditions), in which Fe(III)-OH was the dominant efficient species. The side effects of an excessively long reaction time, which included quaternary ammonium decomposition, FeOOH aggregation, and Fe(III) reduction, were discussed as guidance for optimizing the synthesis strategy. The glycol-solvothermal strategy provides a facile solution to environmental problems through nanocrystal growth engineering in a confined space.

High phosphate removal using La(OH)3 loaded chitosan based composites and mechanistic study.

Our present study was to prepare a biomass-supported adsorbents with high adsorptive capacity and high selectivity to prevent the accelerated eutrophication in water body. To this end, different metal hydroxide (La, Zr and Fe) first was successfully loaded on chitosan microspheres. Then the quaternary ammonium group with different content was introduced into the adsorbent by polymerization. By comparison of adsorption properties, chitosan-La(OH)3-quaternary ammonium-20% (CS-La-N-20%) has strong adsorption to phosphate (160 mg/g) by immobilizing nano-sized La(OH)3 within a quaternary-aminated chitosan and it maintain high adsorption in the presence of salt ions. The pH results indicated that the CS-La-N-20% would effectively sequestrate phosphate over a wide pH range between 3 and 7 without significant La3+ leaching. What's more, adsorption capacity on the introduce of positively charged quanternary-aminated groups was significantly higher than that of the unmodified adsorbents at alkaline conditions. The column adsorption capacity reached 1300 bed volumes (BV) when phosphate concentration decreased until 0.5 mg/L at 6 BV/hr. The column adsorption/desorption reveals that no significant capacity loss is observed, indicating excellent stability and repeated use property. Characterizations revealed that phosphate adsorption on CS-La-N-20% through ligand exchange (impregnated nano-La(OH)3) and electrostatic attraction (positively charged quanternary-aminated groups). All the results suggested that CS-La-N-20% can serve as a promising adsorbent for preferable phosphate removal in realistic application.

Hydrophobic-modified metal-hydroxide nanoflocculants enable one-step removal of multi-contaminants for drinking water production.

Flocculation is a mainstream technology for the provision of safe drinking water but is limited due to the ineffectiveness of conventional flocculants in removing trace low-molecular-weight emerging contaminants. We described a synthesis strategy for the development of high-performance nanoflocculants (hydrophobic-organic-chain-modified metal hydroxides [HOC-M]), imitating surfactant-assembling nano-micelles, by integration of long hydrophobic chains with traditional inorganic metal (Fe/Al/Ti)-based flocculants. The core-shell nanostructure was highly stable in acidic stock solution and transformed to meso-scale coagulation nuclei in real surface water. In both jar and continuous-flow tests, HOC-M was superior over conventional flocculants in removing many contaminants (turbidity, UV254, and DOC: >95%; TP and NO3-N: >90%; trace pharmaceuticals [initial concentration: 100 ng/L]: >80%), producing flocs with better structural and dewatering properties, and lowering the environmental risk of metal leaching. The rationally designed nanoflocculants have large application potential, as a solution to increasing public concern about micro-pollutants and increasing water quality requirements.

Full-scale thermophilic aerobic co-composting of blue-green algae sludge with livestock faeces and straw.

A high incidence of harmful algal bloom in eutrophic surface waters causes many environmental problems. Thermophilic aerobic composting enables effective treatment and disposal of algal sludge that remains after the dewatering of algae slurries, and provides a value-added organic fertiliser. Previous studies have either only dealt with the composting of a single waste component or were conducted at a lab-/pilot-scale; however, this work is a comprehensive assessment of full-scale mechanized thermophilic aerobic co-composting of algal sludge and other typical biomass-based wastes, including chicken faeces and rice straw, in a water-rich rural area in the Tai lake basin, China. With the optimised feedstock material mass ratio (6.0:1.8:1.0 for straw:algae:faeces; initial C/N ratio of 20; and initial moisture of 60 wt%), the co-composting process effectively achieved the reduction, harmlessness, and reuse of waste. The moisture content (28.36 wt% of wet weight), organic matter content (57.91 wt% of dried weight), total nutrient content (6.59 wt% for TN + TP + TK of dried weight), and heavy metal contents as well as the pH of the final product fully met the Chinese National Agricultural Organic Fertiliser Standard requirements. The reduction rates of microcystin and toxic volatile fatty acid contents were higher than 99.5%, and the seed germination index of the product was 114.5%. A notable economic benefit with a gross profit margin of 167-434% of the process was highlighted. Investigation of the associated mechanisms, including statistical analysis, spectral characterisation, micro-morphological observation, and microbial community analysis, revealed that a decreased particle sizes with a looser structure and an efficient humification effect, resulting from the work of several identified dominant microbial species, contributed to the high product quality. The current study provided a demonstration of the promising full-scale co-composting technology for comprehensive management of the environment in water-rich rural areas and the construction of a sustainable watershed.

Role of moderately hydrophobic chitosan flocculants in the removal of trace antibiotics from water and membrane fouling control.

In this paper we describe the preparation and testing of a new class of chitosan-based flocculants for the treatment of surface waters containing antibiotic compounds. Three forms of moderately hydrophobic chitosan flocculants (MHCs) were prepared by chemically grafting hydrophobic branches with different lengths onto hydrophilic chitosan and these were evaluated by jar tests and a bench-scale continuous flow ultrafiltration (UF) membrane process with coagulation/sedimentation pre-treatment. Tests were conducted using both synthetic and real surface water in which norfloxacin and tylosin were added as representative antibiotics at an initial concentration of 0.1 µg/L. In jar tests, the MHCs achieved similar high removal efficiencies (REs) of turbidity and UV254 absorbance, but much higher REs of the two antibiotics (71.7-84.7% and 68.7-76.6% for synthetic and river waters, respectively), compared to several commercial flocculants; the superior performance was attributed to an enhanced hydrophobic interaction and H-bonding between the flocculants and antibiotics. The presence of suspended kaolin particles and humic acid enhanced the antibiotic removal, speculated to be through MHC bridging of the kaolin/humic acid and antibiotic molecules. In the continuous flow tests involving flocculation/sedimentation-UF for 40 days, an optimal MHC achieved a much greater performance than polyaluminium chloride in terms of the overall removal of antibiotics (RE (norfloxacin) of ∼90% and RE (tylosin) of ∼80%) and a greatly reduced rate of membrane fouling; the latter resulting from a more porous and looser structure of cake layer, caused by a surface-modification-like effect of residual MHC on the hydrophobic PVDF membrane. The results of this study have shown that MHCs offer a significant advance over the use of existing flocculants for the treatment of surface water.

Nitrogen-Free Cationic Starch Flocculants: Flocculation Performance, Antibacterial Ability, and UF Membrane Fouling Control.

In light of growing concerns about the formation of nitrogen-based disinfection byproducts (N-DBP) and the possible contribution from the use of quaternary-ammonium-containing flocculants, there is growing interest in the alternative use of quaternary phosphonium salts, which have been reported to have a lower DBP formation potential, stronger cationic properties, lower cytotoxicity, and greater stability. In this study, the performance of N-free quaternary-phosphonium-modified starch flocculants (S-BTP), synthesized through a facile one-step method using commercially available raw materials, in the treatment of bacteria-laden waters (E. coli as the model bacteria) was assessed in both jar tests and a bench-scale continuous-flow flocculation-sedimentation-ultrafiltration process. In jar tests, the effects of the cationic degree of substitution (DS) and dosage of the flocculant, solution pH, and presence of model contaminants on treatment performance were studied. One particular flocculant (S-BTP3), with a DS of 19.3%, displayed high removal efficiencies of E. coli, turbidity, and UV254 from water, comparable with those of ammonium-based analogues and conventional alum, via a combination of charge attraction, polymer bridging, and antibacterial effects. S-BTP3 also possessed better bactericidal properties (99.4% of E. coli killed) than alum (41.4% killed) and did not cause the release of intracellular substances into the treated water. In the continuous-flow flocculation-sedimentation-UF tests, S-BTP3 was superior to alum in the flocculation and antibacterial performance, and in mitigating UF membrane fouling. The results have clearly demonstrated the multiple benefits of the use of N-free cationic starch flocculants in water treatment as an alternative to conventional chemicals.

Pilot-scale composting of typical multiple agricultural wastes: Parameter optimization and mechanisms.

In this work, pilot-scale (100 kg of mixed wastes each time) composting of typical agricultural wastes, including chicken manure, vegetable leaves and rice husks with a mass ratio of 6:3:1, was studied. Effects of thermal phases and transformation time on performance, including moisture, nutrient, and carbon contents and C/N ratios of compost, were investigated. The optimal parameters were 75 ±â€¯5 °C and 18 h; the compost met the requirements of Chinese National Agricultural Organic Fertilizer Standard (NY525-2012). Mechanisms investigations demonstrated that, Bacillus and Sinibacillus played key roles in degrading high-molecular-weighted organic substances into small-molecular-weighted humic- and fulvic-acid-like matters, resulting in smaller particle size and loose structure of the product; rice husk particles acted as a conditioning agent and remained their originally morphology. The mechanism provided informative guidance for optimizing the process in practical application.

Norfloxacin and Bisphenol-A Removal Using Temperature-Switchable Graphene Oxide.

Graphene oxide (GO) is a competitive candidate used for adsorption of emerging organic contaminants (EOCs) from water. To overcome GO's spontaneous aggregation tendency in adsorption and to ease contaminant desorption from the adsorbent for adsorbent regeneration, a modified GO (P-GO), with temperature-switchable hydrophilicity/hydrophobicity, obtained by grafting temperature-responsive poly( N- n-propylacrylamide) was proposed. Two model EOCs, norfloxacin (NOR) and bisphenol A (BPA), with distinct hydrophilicity/hydrophobicity were employed. P-GO showed significant temperature-responsive adsorption behaviors: P-GO was more hydrophilic at a lower temperature and was beneficial for the adsorption of hydrophilic NOR, whereas it turned more hydrophobic at a higher temperature and was preferred for the adsorption of hydrophobic BPA. Compared with GO, P-GO under corresponding optimal conditions had comparable large adsorption amounts for NOR because of an "adsorption site replacement" strategy and notably enhanced adsorption for BPA because of strengthened hydrophobic association. Main interfacial binding interactions were π-π electron donor-acceptor effect and H-bonding for NOR adsorption and hydrophobic association and H-bonding for BPA uptake. On the basis of the temperature-responsive adsorption behaviors and studied interfacial interactions, regeneration of the adsorbent at designed temperatures using water (without additional chemicals) as an eluent is realized. This achievement is important for reducing risks of secondary environmental pollution during regeneration and easing further recovery of organic contaminants if needed.