Fenton-like activity and pathway modulation via single-atom sites and pollutants comediates the electron transfer process.

The studies on the origin of versatile oxidation pathways toward targeted pollutants in the single-atom catalysts (SACs)/peroxymonosulfate (PMS) systems were always associated with the coordination structures rather than the perspective of pollutant characteristics, and the analysis of mechanism commonality is lacking. In this work, a variety of single-atom catalysts (M-SACs, M: Fe, Co, and Cu) were fabricated via a pyrolysis process using lignin as the complexation agent and substrate precursor. Sixteen kinds of commonly detected pollutants in various references were selected, and their lnkobs values in M-SACs/PMS systems correlated well (R2 = 0.832 to 0.883) with their electrophilic indexes (reflecting the electron accepting/donating ability of the pollutants) as well as the energy gap (R2 = 0.801 to 0.840) between the pollutants and M-SACs/PMS complexes. Both the electron transfer process (ETP) and radical pathways can be significantly enhanced in the M-SACs/PMS systems, while radical oxidation was overwhelmed by the ETP oxidation toward the pollutants with lower electrophilic indexes. In contrast, pollutants with higher electrophilic indexes represented the weaker electron-donating capacity to the M-SACs/PMS complexes, which resulted in the weaker ETP oxidation accompanied with noticeable radical oxidation. In addition, the ETP oxidation in different M-SACs/PMS systems can be regulated via the energy gaps between the M-SACs/PMS complexes and pollutants. As a result, the Fenton-like activities in the M-SACs/PMS systems could be well modulated by the reaction pathways, which were determined by both electrophilic indexes of pollutants and single-atom sites. This work provided a strategy to establish PMS-based AOP systems with tunable oxidation capacities and pathways for high-efficiency organic decontamination.

Utilizing the oxygen-atom trapping effect of Co3O4 with oxygen vacancies to promote chlorite activation for water decontamination.

Heterogeneous high-valent cobalt-oxo [≡Co(IV)=O] is a widely focused reactive species in oxidant activation; however, the relationship between the catalyst interfacial defects and ≡Co(IV)=O formation remains poorly understood. Herein, photoexcited oxygen vacancies (OVs) were introduced into Co3O4 (OV-Co3O4) by a UV-induced modification method to facilitate chlorite (ClO2-) activation. Density functional theory calculations indicate that OVs result in low-coordinated Co atom, which can directionally anchor chlorite under the oxygen-atom trapping effect. Chlorite first undergoes homolytic O-Cl cleavage and transfers the dissociated O atom to the low-coordinated Co atom to form reactive ≡Co(IV)=O with a higher spin state. The reactive ≡Co(IV)=O rapidly extracts one electron from ClO2- to form chlorine dioxide (ClO2), accompanied by the Co atom returning a lower spin state. As a result of the oxygen-atom trapping effect, the OV-Co3O4/chlorite system achieved a 3.5 times higher efficiency of sulfamethoxazole degradation (~0.1331 min-1) than the pristine Co3O4/chlorite system. Besides, the refiled OVs can be easily restored by re-exposure to UV light, indicating the sustainability of the oxygen atom trap. The OV-Co3O4 was further fabricated on a polyacrylonitrile membrane for back-end water purification, achieving continuous flow degradation of pollutants with low cobalt leakage. This work presents an enhancement strategy for constructing OV as an oxygen-atom trapping site in heterogeneous advanced oxidation processes and provides insight into modulating the formation of ≡Co(IV)=O via defect engineering.

Revealing the Generation of High-Valent Cobalt Species and Chlorine Dioxide in the Co3O4-Activated Chlorite Process: Insight into the Proton Enhancement Effect.

A Co3O4-activated chlorite (Co3O4/chlorite) process was developed to enable the simultaneous generation of high-valent cobalt species [Co(IV)] and ClO2 for efficient oxidation of organic contaminants. The formation of Co(IV) in the Co3O4/chlorite process was demonstrated through phenylmethyl sulfoxide (PMSO) probe and 18O-isotope-labeling tests. Both experiments and theoretical calculations revealed that chlorite activation involved oxygen atom transfer (OAT) during Co(IV) formation and proton-coupled electron transfer (PCET) in the Co(IV)-mediated ClO2 generation. Protons not only promoted the generation of Co(IV) and ClO2 by lowering the energy barrier but also strengthened the resistance of the Co3O4/chlorite process to coexisting anions, which we termed a proton enhancement effect. Although both Co(IV) and ClO2 exhibited direct oxidation of contaminants, their contributions varied with pH changes. When pH increased from 3 to 5, the deprotonation of contaminants facilitated the electrophilic attack of ClO2, while as pH increased from 5 to 8, Co(IV) gradually became the main contributor to contaminant degradation owing to its higher stability than ClO2. Moreover, ClO2- was transformed into nontoxic Cl- rather than ClO3- after the reaction, thus greatly reducing possible environmental risks. This work described a Co(IV)-involved chlorite activation process for efficient removal of organic contaminants, and a proton enhancement mechanism was revealed.

Unveiling the Origins of Selective Oxidation in Single-Atom Catalysis via Co-N4-C Intensified Radical and Nonradical Pathways.

Single-atom catalysts (SACs)-based peroxymonosulfate (PMS) systems are highly selective to the type of organic pollutants while the mechanisms remain ambiguous. In this work, we carried out experimental and theoretical investigations to reveal the origins of selectivity of radical and nonradical pathways in a designated Co-N4-C/PMS system. Two typical pollutants [bisphenol A (BPA) and metronidazole (MNZ)] with different molecular structures were employed for comparison. We found that radical oxidation (SO4•- and HO•) and nonradical electron-transfer pathway (ETP) co-existed in the Co-N4-C/PMS system. Pollutants (e.g., MNZ) with a high redox potential were degraded primarily by free radicals rather than ETP, while the oxidization of low-redox pollutants (e.g., BPA) was dominated by ETP at the surface region of Co-N4-C which overwhelmed the contributions of radicals in the homogeneous phase. Intriguingly, the contributions of radical and nonradical pathways could be manipulated by the PMS loading, which simultaneously increased the radical population and elevated the oxidation potential of Co-N4-C-PMS* complexes in ETP. Findings from this work will unravel the mysterious selective behavior of the SACs/PMS systems in the oxidation of different micropollutants.

Single-atom catalysis in advanced oxidation processes for environmental remediation.

Emerging single atom catalysts (SACs), especially carbon-based SACs are appealing materials in environmental catalysis because of their ultrahigh performances, environmental friendliness, structural/chemical robustness, and the maximum utilization of active metal sites. The metal centres, carbon matrixes, and coordination characteristics collectively determine the electronic features of carbon-based SACs, and their behaviours in catalysing peroxide activation and efficiencies in advanced oxidation processes (AOPs). However, there is lack of a comprehensive and critical review reporting the successful marriage of carbon-based SACs in AOP-based remediation technologies. It is particularly necessary to systematically compare and reveal the catalytic sites and the associated mechanisms of carbon-based SACs in diverse AOP systems. In this review, we highlight the synthetic strategies, characterisation, and computation of carbon-based SACs, and for the first time, showcase their innovative applications in AOP technologies. We unveil the origins of versatile catalytic oxidation pathways in different AOP systems and the mechanisms of micropollutant degradation over carbon-based SACs, distinguished from the upsized counterparts (metals/oxides and carbon substrates). We also provide directions to the rational design of on-demand SACs for green chemistry and environmental sustainability. Also, we suggest a designated and integrated experimental/theoretical protocol for revealing the structure-catalysis relations of SACs in AOP applications, and propose the prospects for future opportunities and challenges.

Antibiotics promoted the recovery of Microcystis aeruginosa after UV-B radiation at cellular and proteomic levels.

Elevated UV-B radiation due to ozone layer depletion may prevent the growth of bloom-forming cyanobacteria in aquatic environments, while antibiotic contaminants may cause effects opposite to that of UV-B due to hormesis. This study investigated the influence of a quaternary antibiotic mixture on Microcystis aeruginosa after UV-B radiation through a 15-day exposure test. UV-B radiation extended the lag phase of M. aeruginosa at doses of 600 and 900 mJ/cm2, and significantly (p < 0.05) reduced the growth rate and the Fv/Fm value at doses of 300-900 mJ/cm2. Although UV-B radiation significantly (p < 0.05) stimulated the microcystin production ability in each cyanobacterial cell, the total microcystin concentration still significantly (p < 0.05) decreased due to the reduction of cell density. Mixed antibiotics and UV-B regulated the proteomic expression profile of M. aeruginosa in different manners. UV-B radiation upregulated 19 proteins and downregulated 49 proteins in M. aeruginosa, while mixed antibiotics upregulated 45 proteins and downregulated 25 proteins in UV-B treated cells. Mixed antibiotics significantly (p < 0.05) stimulated growth and photosynthesis, increased cell density and microcystin concentration, and reduced oxidative stress in UV-B treated cells through the upregulation of proteins involved in photosynthesis, biosynthesis, cell division, oxidation-reduction, gene expression and microcystin synthesis. This study verified the hypothesis that antibiotics accelerated the recovery of M. aeruginosa from UV-B induced damage. A safe threshold of 20 ng/L was suggested for mixed antibiotics (5 ng/L for each antibiotic), in order to eliminate the stimulatory effects of antibiotics on bloom-forming cyanobacteria.

Synchronous removal of CuO nanoparticles and Cu2+ by polyaluminum chloride-Enteromorpha polysaccharides: Effect of Al species and pH.

Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid (HA) to form composite contaminants. As an innovative recycled coagulant aid, Enteromorpha polysaccharides (Ep) were associated with polyaluminum chloride (PACl) (denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu2+ and HA in this study. The influence of different Al species coagulants (AlCl3, PAClb and PAClc) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail. Results showed that in the three PACl-Ep systems, PAClb-Ep gave the highest removal efficiencies for turbidity and Cu2+, and the best UV254 removal effect was reached by using PAClc-Ep. Higher contents of Alb and Alc contributed to great coagulation performance because of their stronger bridging and sweeping effects. For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions. Additionally, smaller and more agminated flocs with great recovery ability were formed by PAClb-Ep and PAClc-Ep systems (bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species). Similarly, due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.

Adsorptive removal of phosphate by the bimetallic hydroxide nanocomposites embedded in pomegranate peel.

This study aimed to fabricate new and effective material for the efficiency of phosphate adsorption. Two types of adsorbent materials, the zirconium hydroxides embedded in pomegranate peel (Zr/Peel) and zirconium-lanthanum hydroxides embedded in pomegranate peel (Zr-La/Peel) were developed. Scanning electronic microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) were evaluated to give insight into the physicochemical properties of these adsorbents. Zr-La/Peel exceeded the adsorption efficiency of Zr/Peel adsorbents in batch adsorption experiments at the same pH level. The peel as a host can strive to have a strong "shielding effect" to increase the steadiness of the entrenched Zr and La elements. La and Zr are hydroxide metals that emit many hydrogen ions during the hydrolysis reaction, which contribute to protonation and electrostatic attraction. The highest adsorption capacity of La-Zr/Peel for phosphate was calculated to be 40.21 mg/g, and pseudo second-order equation is very well fitted for kinetic adsorption. Phosphate adsorption efficiency was reduced by an increase of pH. With the background of coexisting Cl-, little effect on adsorption efficiency was observed, while adsorption capacities were reduced by almost 20-30% with the coexistence of [Formula: see text] , [Formula: see text] and humic acid (HA).

Pilot-Scale Pyrolytic Remediation of Crude-Oil-Contaminated Soil in a Continuously-Fed Reactor: Treatment Intensity Trade-Offs.

Pyrolytic treatment offers the potential for the rapid remediation of contaminated soils. However, soil fertility restoration can be highly variable, underscoring the need to understand how treatment conditions affect soil detoxification and the ability to support plant growth. We report here the first pilot-scale study of pyrolytic remediation of crude-oil-contaminated soil using a continuously fed rotary kiln reactor. Treatment at 420 °C with only 15 min of residence time resulted in high removal efficiencies for both total petroleum hydrocarbons (TPH) (99.9%) and polycyclic aromatic hydrocarbons (PAHs) (94.5%) and restored fertility to clean soil levels (i.e., Lactuca sativa biomass dry weight yield after 21 days increased from 3.0 ± 0.3 mg for contaminated soil to 8.8 ± 1.1 mg for treated soil, which is similar to 9.0 ± 0.7 mg for uncontaminated soil). Viability assays with a human bronchial epithelial cell line showed that pyrolytic treatment effectively achieved detoxification of contaminated soil extracts. As expected, TPH and PAH removal efficiencies increased with increasing treatment intensity (i.e., higher temperatures and longer residence times). However, higher treatment intensities decreased soil fertility, suggesting that there is an optimal system-specific intensity for fertility restoration. Overall, this study highlights trade-offs between pyrolytic treatment intensity, hydrocarbon removal efficiency, and fertility restoration while informing the design, optimization, and operation of large-scale pyrolytic systems to efficiently remediate crude-oil-contaminated soils.

Influence of mixed antibiotics on Microcystis aeruginosa during the application of glyphosate and hydrogen peroxide algaecides.

Antibiotics regulate various physiological functions in cyanobacteria and may interfere with the control of cyanobacterial blooms during the application of algaecides. In this study, Microcystis aeruginosa was exposed to H2 O2 and glyphosate for 7 d in the presence of coexisting mixed antibiotics (amoxicillin, spiramycin, tetracycline, ciprofloxacin, and sulfamethoxazole) at an environmentally relevant concentration of 100 ng · L-1 . The mixed antibiotics significantly (P < 0.05) alleviated the growth inhibition effect of 15-45 µM H2 O2 and 40-60 mg · L-1 glyphosate. According to the increased contents of chlorophyll a and protein, decreased content of malondialdehyde, and decreased activities of superoxide dismutase and glutathione S-transferase, antibiotics may reduce the toxicity of the two algaecides through the stimulation of photosynthesis and the reduction in oxidative stress. The presence of coexisting antibiotics stimulated the production and release of microcystins in the M. aeruginosa exposed to low concentrations of algaecides and posed an increased threat to aquatic environments. To eliminate the secondary pollution caused by microcystins, high algaecide doses that are ≥45 µM for H2 O2 and ≥60 mg · L-1 for glyphosate are recommended. This study provides insights into the ecological hazards of antibiotic contaminants and the best management practices for cyanobacterial removal under combined antibiotic pollution conditions.

A biodegradable biomass-based polymeric composite for slow release and water retention.

Slow-release fertilizer has been proven to be more effective than traditional fertilizer for providing a long-term stable nutrient supply. Although such fertilizers have been widely investigated, their water-retention properties and biodegradability have not been fully analysed. Composites of fertilizers and polymers provide opportunities to prepare new types of fertilizer with enhanced properties for real applications. Chicken feather protein-graft-poly(potassium acrylate)-polyvinyl alcohol semi-interpenetrating networks forming a super absorbent resin combined with nitrogen (N) and phosphorus (P) (CFP-g-PKA/PVA/NP semi-IPNs SAR) was prepared. The chemically bonded or physically embedded fertilizer compound could be released form the resin matrix to the surrounding soil under irrigation. The synthesis mechanism, morphology, and chemical and mechanical structure of the synthesized composites were investigated. The reactant doses were optimized through response surface methodology (RSM). A 30-day field trial of the prepared SAR was applied to detect the influence of sample particle size, soil salinity, pH, and moisture content on the slow-release behaviour of N and P. The maximum release values of N and P from the composites were 69.46% N and 65.23% P. A 120-day soil burying experiment and 30-day Aspergillus niger (A. niger) inoculation were performed, and the biodegradability and change in microstructure were monitored. The addition of SAR to soil could also improve the water-retention ability of the soil.

Characterization of dissolved organic matter and membrane fouling in coagulation-ultrafiltration process treating micro-polluted surface water.

Coagulation-ultrafiltration (C-UF) is widely used for surface water treatment. With the removal of pollutants, the characteristics of organic matter change and affect the final treatment efficiency and the development of membrane fouling. In this study, we built a dynamic C-UF set-up to carry out the treatment of micro-polluted surface water, to investigate the characteristics of dissolved organic matter from different units. The influences of poly aluminum chloride and poly dimethyldiallylammonium chloride (PDMDAAC) on removal efficiency and membrane fouling were also investigated. Results showed that the dosage of PDMDAAC evidently increased the UV254 and dissolved organic carbon removal efficiencies, and thereby alleviated membrane fouling in the C-UF process. Most hydrophobic bases (HoB) and hydrophobic neutral fractions could be removed by coagulation. Similarly, UF was good at removing HoB compared to hydrophilic substances (HiS) and hydrophobic acid (HoA) fractions. HiS and HoA fractions with low molecule weight accumulated on the surface of the membrane, causing the increase of transmembrane pressure (TMP). Membrane fouling was mainly caused by a removable cake layer, and mechanical cleaning was an efficient way to decrease the TMP.

Removal of tridecane dicarboxylic acid in water by nanoscale Fe0/Cu0 bimetallic composites.

In this study, nanoscale zerovalent Fe0/Cu0 bimetallic composites were synthesized by liquid-phase reduction of Fe(II)/Cu(II) and applied for decomposition of tridecane dicarboxylic acid (DC13). The removal performance of Fe0/Cu0 bimetallic composites for DC13 in terms of Fe/Cu ratios, addition amount, reaction time and initial pH were studied. The as-prepared nanoscale composites were characterized by a transmission electron micrographs (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area, fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma-atomic emission spectrometry (ICP). Finally, the degradation mechanisms of DC13 utilizing the Fe0/Cu0 nanocomposites were investigated by using mass spectrumetry (MS). The results indicated that the Fe0/Cu0 bimetallic composites exerted a remarkable removal capacity for DC13 through the multiple reactions, e.g., coagulation, adsorption and •OH reduction in the Fe0/Cu0 system. XPS indicated that the Fe0/Cu0 reduction reaction of hydroxyl radicals (•OH) system played a significant role in degradation of DC13 and the LC-MS result suggested that DC13 was degraded into inorganic small molecules by •OH radicals generated from the corrosion of Fe0. The experimental results indicated that the nanoscale Fe0/Cu0 could be used as a potential material to remove DC13 because of its remarkable degradability.

Research on adsorption of Cr(â ¥) by Poly-epichlorohydrin-dimethylamine (EPIDMA) modified weakly basic anion exchange resin D301.

A novel composite, EPIDMA/D301, with high adsorption capacity and particular affinity toward Cr(Ⅵ) was well prepared utilizing cationic polyelectrolyte poly-epichlorohydrin-dimethylamine (EPIDMA) impregnated in the networking pores of the styrene macroporous weak basic anion exchange resin D301. The physicochemical characteristics of EPIDMA/D301 were characterized by the Brunauer-Emmett-Teller (BET), zeta potential, FTIR, SEM-Mapping and XPS. The adsorption properties were researched via the influence of the concentration of EPIDMA, adsorbent dose, pH, the initial concentration of Cr(Ⅵ) solution, contact time and temperature. Results presented that the weakly basic anion exchange resin supported cationic polymer showed the excellent potential of removing Cr(VI) ions primarily due to the nonspecific Cr(VI) adsorption resulted from the polymeric host D301, the electrostatic attraction of amino groups fixed on the D301 matrix and the embedded EPIDMA with Cr(VI) ions and the ion exchange by the displacement of Cl- mainly derived from EPIDMA with Cr(VI) ions. The kinetic data were best fitted by the pseudo-second-order kinetic model. The batch equilibrium data followed Langmuir isotherm model well with the maximum adsorption capacity of 194 mg g-1 at 25 °C, which demonstrated that the styrene anion exchange resin modified with EPIDMA might be an efficient approach to eliminate potentially toxic metals.

Application for oxytetracycline wastewater pretreatment by Fe-C-Ni catalytic cathodic-anodic-electrolysis granular fillers from rare-earth tailings.

Fe-C-Ni catalytic cathodic-anodic-electrolysis granular fillers (REGF) coupled with a reactor was studied for oxytetracycline (OTC) wastewater pretreatment. In this study, the REGF were manufactured from the rare-earth tailing (RET), powdered activated carbon (PAC), scrap iron and nickel by balling and calcining. The REGF was characterized by X-Ray Diffraction and Scanning Electron Microscope analysis. The influences of pH value (2-7), OTC concentrations, hydraulic retention time and aeration on the removal efficiency of OTC and total organic carbon (TOC) were studied. This system had good removal efficiency of TOC of 80.0% and OTC of 98.2% under the optimal conditions, which were influent pH of 3, aeration rate of 0 mg L-1, and HRT of 3 h. After running for 50 d, the REGF did not become hardened and the ability of reaction was more lasting. The system was back-washed by acid solution (pH = 1) in the 25th day. The removal mechanisms were electrophoresis, redox and flocculation. The nickel, which was as the catalyst, was added into REGF to enhance the reduction of pollution with the absorbed atomic hydrogen. This paper provides a way for the recycle of the rare earth tailings and an effective application for wastewater.

Preparation of wheat straw-supported Nanoscale Zero-Valent Iron and its removal performance on ciprofloxacin.

Wheat straw-supported Nanoscale Zero-Valent Iron particles (WS-NZVI) were successfully synthesized, which were used for Ciprofloxacin hydrochloride (CIP) removal in simulation wastewater. The structure, chemical composition and micro-morphology of WS-NZVI and Nanoscale Zero-Valent Iron (NZVI) were characterized by scanning electron microscopy analysis (SEM), X-ray diffraction (XRD), as well as the Fourier Transformed IR spectra (FT-IR). XRD results proved the existence of Fe°, and SEM images indicated that the agglomeration of NZVI was effectively inhibited when loaded on wheat straw. Besides, the effects of initial solution pH, CIP concentration, adsorbents dosage and contacting time on the removal efficiency of CIP by WS-NZVI and NZVI were investigated. The experimental results showed that, compared with NZVI and wheat straw, WS-NZVI possessed higher removal efficiency for CIP, and the maximum removal capacity of CIP by WS-NZVI was 363.63 mg g-1 (25 °C). Furthermore, WS-NZVI was suitable for wider pH range (pH = 4-10) in comparison with NZVI. For the WS-NZVI, the kinetic was better fitted with pseudo-second-order equation, rather than pseudo-first-order equation. The Mass spectrometry (MS) analysis deduced that the degradation reaction mainly occurred on quinolone groups piperazinyl ring. Therefore, it is feasible that using wheat straw as a support material to enhance the performance of NZVI, and the synthesized WS-NZVI has a potential in the organic compounds elimination because of its redox reaction activity.

Facile one-step synthesis of functionalized biochar from sustainable prolifera-green-tide source for enhanced adsorption of copper ions.

The use of biochars formed by hydrothermal carbonization for the treatment of contaminated water has been greatly limited, due to their poorly developed porosity and low content of surface functional groups. Also, the most common modification routes inevitably require post-treatment processes, which are time-consuming and energy-wasting. Hence, the objective of this research was to produce a cost-effective biochar with improved performance for the treatment of heavy metal pollution through a facile one-step hydrothermal carbonization process coupled with ammonium phosphate, thiocarbamide, ammonium chloride or urea, without any post-treatment. The effects of various operational parameters, including type of modification reagent, time and temperature of hydrothermal treatment, and ratio of modification reagent to precursor during impregnation, on the copper ion adsorption were examined. The adsorption data fit the Langmuir adsorption isotherm model quite well. The maximum adsorption capacities (mg/g) of the biochars towards copper ions followed the order of 40-8h-1.0-APBC (95.24)>140-8h-0-BC (12.52)>140-8h-1.0-TUBC (12.08)>140-8h-1.0-ACBC (7.440)>140-8h-1.0-URBC (5.277). The results indicated that biochars modified with ammonium phosphate displayed excellent adsorption performance toward copper ions, which was 7.6-fold higher than that of the pristine biochar. EDX and FT-IR analyses before and after adsorption demonstrated that the main removal mechanism involved complexation between the phosphate groups on the surface of the modified biochars and copper ions.

Aluminum formate (AF): Synthesis, characterization and application in dye wastewater treatment.

Aluminum formate (AF), a degradable and non-corrosive coagulant, was synthesized from aluminum hydroxide and formic acid. Polyamidine (PA), as a coagulation aid, was combined with AF for dye wastewater treatment. AF was characterized by XPS, FT-IR, viscosity, zeta potential, mass spectrum and XRD, and the flocculation properties of the dual-coagulation system were characterized by FT-IR and SEM. The results showed that COOH, Al2O3-Al and O2-Al bonds were formed in the AF synthesis process, and AF had a higher molecular weight and higher charge neutralization ability than PAC. The hydrolysates of AF were determined to contain Al13 Al11 and Al2, and the components of AF were confirmed to comprise a mixture including aluminum formate (C3H3AlO6) and its hydrate. When the color removal efficiency reached 100% in jar tests, the optimized dosage of AF/PA was 18.91/0.71mg/L, while the optimized dosage of PAC/PA was 21.19/0.91mg/L. According to the variance analysis, the interaction between AF/PA and PAC/PA were insignificant in macroscopic view. FT-IR spectrum indicated AF captured pollutant by means of CCO bond, PAC captured pollutant by δ CH, CC and δ CH. Overall, although the coagulation mechanism of AF was different from that of PAC, AF/PA showed better coagulation efficiency than PAC/PA in dye wastewater treatment.

Performance of bimetallic nanoscale zero-valent iron particles for removal of oxytetracycline.

In this study, bimetallic nanoscale zero-valent iron particles (nZVI), including copper/nanoscale zero-valent iron particles (Cu/nZVI) and nickel/nanoscale zero-valent iron particles (Ni/nZVI), were synthesized by one-step liquid-phase reduction and applied for oxytetracycline (OTC) removal. The effects of contact time and initial pH on the removal efficiency were studied. The as-prepared nanoscale particles were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Finally, the degradation mechanisms of OTC utilizing the as-prepared nanoparticles were investigated by using X-ray photoelectron spectroscopy (XPS) and mass spectrometry (MS). Cu/nZVI presented remarkable ability for OTC degradation and removed 71.44% of OTC (100mg/L) in 4hr, while only 62.34% and 31.05% of OTC was degraded by Ni/nZVI and nZVI respectively. XPS and MS analysis suggested that OTC was broken down to form small molecules by ·OH radicals generated from the corrosion of Fe0. Cu/nZVI and Ni/nZVI have been proved to have potential as materials for application in OTC removal because of their significant degradation ability toward OTC.

Pre-treatment of pyridine wastewater by new cathodic-anodic-electrolysis packing.

A novel cathodic-anodic-electrolysis packing (CAEP) used in the treatment of pyridine wastewater was researched, which mainly consisted of 4,4'-diamino-2,2'-disulfonic acid (DSD acid) industrial iron sludge. The physical properties and morphology of the packing were studied. The CAEP was used in a column reactor during the pretreatment of pyridine wastewater. The influence of pH, hydraulic retention time (HRT), the air-liquid ratio (A/L) and the initial concentration of pyridine were investigated by measuring the removal of total organic carbon (TOC) and pyridine. The characterization results showed that the bulk density, grain density, water absorption percentage and specific surface area were 921kg/m3, 1086kg/m3, 25% and 29.89m2/g, respectively; the removal of TOC and pyridine could reach 50% and 58% at the optimal experimental conditions (pH=3, HRT=8hr, A/L=2). Notably, the surface of the packing was renewed constantly during the running of the filter, and the handling capacity was stable after running for three months.