Highest TOC Removal Research Articles

Boron/Fe2+/H2O2 combined with resins process cost-effectively remove Ni(II) in wastewater containing Ni-EDTA: Performance and mechanism

This study proposes a green purification strategy in which mild decomplexation of Ni-EDTA into other Ni complexes facilitates the efficient removal and recovery of nickel through resin adsorption. Decomplexation of Ni-EDTA by boron/Fe2+/H2O2 (B/Fe2+/H2O2) followed by resins adsorption was conducted for Ni(II) removal in Ni-EDTA. The Ni(II) removal efficiency could only achieve 1.3 % and 6.2 % while Ni(II) coexisted with EDTA but more than 10 times of higher when Ni(II) coexisted with EDTA-relatives via the single adsorption of commercial heavy metal-affined resins (D001 and D463), which attributed to the increased binding energies of these Ni-EDTA’s degradation products complexes than Ni-EDTA based on density functional theory (DFT) calculation. In comparing to precipitation, the resin adsorption required much less mineralization of EDTA to have a better removal efficiency of Ni(II). B improved the efficiency of Ni-EDTA decompexation by accelerating the recycle of Fe3+/Fe2+. The EDTA (and TOC) removal enhanced from 48.7 % (4.7 %) to 94.7 % (11.9 %) by B/Fe2+/H2O2 process comparing to Fe2+/H2O2 process. With the high EDTA but low TOC removal efficiency after B/Fe2+/H2O2 treatment, Ni(II) removal efficiency via resins adsorption could maximum achieve 80.5 %, 2–3 times of that via regular precipitation method. In addition, B and resins exhibited good reusability in five cycles, and B/Fe2+/H2O2-resins process had excellent adaptability to different heavy metal complexes. B/Fe2+/H2O2-D463 system not only could reduce 78.4 % reagents cost compared with that of Fe2+/H2O2-precipitation process, but also could save much cost than other processes. The results provide new insights for the cost-effective treatment of EDTA-complexed heavy metal wastewater.

Ferromanganese oxide-functionalized TiO2 for rapid catalytic ozonation of PPCPs through a coordinated oxidation process with adjusted composition and strengthened generation of reactive oxygen species

Ferromanganese oxide (MFOx) was first utilized to functionalize TiO2 and an MFOx@TiO2 catalyst was developed for catalytic ozonation for rapid attack of pharmaceutical and personal care products (PPCPs) with adjusted reactive oxygen species (ROSs) composition and strengthened ROSs generation. Unlike Al2O3, which strongly relied on adsorption and was significantly influenced by MFOx loading, synergistic catalytical effects of MFOx and TiO2 were observed, and optimal MFOx doping of 2 wt% and MFOx@TiO2 dosage of 500 ppm were obtained for catalyzing ozonation. In ibuprofen (IBP) degradation, MFOx@TiO2-catalyzed ozonation (MFOx@TiO2/O3) obtained 2.0-, 4.7- and 6.9-folds the kobs of TiO2/O3, MFOx/O3 and bare ozonation (B/O3). Stronger O3 decomposition was observed by MFOx@TiO2 over bare TiO2 with the participation of redox pairs Fe(II)/Fe(III) and Mn(II)/Mn(III)/Mn(IV) and increased surface oxygen vacancies (SOVs) from 9.8 % to 33.7 % was detected. The results revealed that Fe(II), Mn(II) and Mn(III) with low valance accelerated Ti(III) generation from Ti(VI), obtaining an unprecedented high Ti(III) composition occupying 35.3 % of the total Ti atoms. Ti(III) catalyzed the direct reduction of SOVs-O2 to •O2–, and it accelerated the formation of Ti(VI)-OH and Ti(VI)-O which catalyzed O3 decomposition into •O2–. •O2– was found to primarily initiate IBP degradation with nucleophilic addition and dominated over 66 % IBP removal. The enhanced •O2– generation further strengthened •OH and 1O2 production. MFOx@TiO2/O3 obtained 17 %, 21 % and 30 % higher TOC removal over TiO2/O3, MFOx/O3 and B/O3, respectively. Acute toxicity tests confirmed the effective toxicity control of organics by MFOx@TiO2/O3 process (inhibition rate: 10.9 %). Degradation test of atenolol and sulfamethoxazole confirmed the catalytic effects of MFOx@TiO2. MFOx@TiO2 performed strong resistance to water matrix in application test and showed good stability and reusability. The study proposed an effective catalyst for strengthening the ozonation process on PPCPs degradation and provided an in-depth understanding of the mechanisms and characteristics of the MFOx@TiO2 catalyst and MFOx@TiO2/O3 process.

Exploring the Synergistic Mechanisms of Nanopulsed Plasma Bubbles and Photocatalysts for Trimethoprim Degradation and Mineralization in Water.

In this study, the synergetic action of nanopulsed plasma bubbles (PBs) and photocatalysts for the degradation/mineralization of trimethoprim (TMP) in water was investigated. The effects of ZnO or TiO2 loading, plasma gas, and initial TMP concentration were evaluated. The physicochemical characterization of plasma-treated water, the quantification of plasma species, and the use of appropriate plasma species scavengers shed light on the plasma-catalytic mechanism. ZnO proved to be a superior catalyst compared to TiO2 when combined with plasma bubbles, mainly due to the increased production of ⋅OH and oxygen species resulting from the decomposition of O3. The air-PBs + ZnO system resulted in higher TMP degradation (i.e., 95% after 5 min of treatment) compared to the air-PBs + TiO2 system (i.e., 87%) and the PBs-alone process (83%). The plasma gas strongly influenced the process, with O2 resulting in the best performance and Ar being insufficient to drive the process. The synergy between air-PBs and ZnO was more profound (SF = 1.7), while ZnO also promoted the already high O2-plasma bubbles' performance, resulting in a high TOC removal rate (i.e., 71%). The electrical energy per order in the PBs + ZnO system was very low, ranging from 0.23 to 0.46 kWh/m3, depending on the plasma gas and initial TMP concentration. The study provides valuable insights into the rapid and cost-effective degradation of emerging contaminants like TMP and the plasma-catalytic mechanism of antibiotics.

Removal of Congo red dye by electrochemical advanced oxidation process: optimization, degradation pathways, and mineralization

The degradation of Congo red dye has been studied by electrochemical advanced oxidation process based on the generation of powerful oxidizing agents especially hydroxyl radicals ·OH. In this study, the effect of several experimental parameters, such as pH, ferrous ion concentration, electrolyte support concentration and current intensity, on the process was investigated. The experimental design of Doehlert was applied to determine the optimum conditions of three factors, namely current intensity, initial Fe2+ concentration and electrolysis time for the Congo red removal. The relationship of response to experimental variables was represented graphically by the construction of the two-dimensional iso-response contour plots and those indicated that 360 mA, 19 mM Fe2+ and 30 min reaction time were optimal under 50 mM Na2SO4 at pH 3, leading to a total Congo red degradation. A quadratic polynomial model was determined and its statistical significance was verified through the variance analysis, which indicated that the proposed model was statistically meaningful and convenient for the results prediction. The mineralization of Congo red under the obtained optimum conditions was examined and the results showed a high TOC removal rate (81.1%) after 300 min of reaction time. Finally, a plausible degradation pathway was suggested.

Magnetic nickel ferrite for efficient persulfate activation to remove aqueous refractory organics: Synthesis, advantages, mechanism, and environmental implications

Magnetic spinel ferrites are promising catalysts for activating persulfate for aqueous organics removal. Herein, a high-efficiency ferrite NiFe2O4 was synthesized and comprehensively investigated for persulfate activation. The optimal preparation conditions and their interactions were successfully determined by response surface methodology. The resultant catalyst was characterized with favorable properties for persulfate activation, e.g., porous morphology, excellent magnetism, and good redox activity. The study of operating parameters showed good adaptability of the NiFe2O4 +PS system to pH variation (3–9), and 100 % diclofenac removal was achieved. Mineralization and PS consumption tests showed high TOC removal (65.6 %) and a low PS demand (PS:diclofenac = 6.7:1), which were clear advantages of NiFe2O4, indicating its excellent activity towards PS decomposition. Additionally, the catalyst could be recovered quickly and completely during reuse (> 90 % recovery within 10 s). In addition, persulfate was considered to bind to the catalyst via electrostatic and chemical bonding, followed by the generation of surface-bound SO4•−. A potential mechanism of persulfate activation by NiFe2O4 and three possible degradation routes of diclofenac were proposed. Finally, the environmental implications of the NiFe2O4 +persulfate system for treating actual waters and multiple pollutants were revealed. This work supplemented ferrite for persulfate activation and provided an effective oxidative system for decontamination.

Electric field-enhanced heterogeneous catalytic ozonation (EHCO) process for sulfadiazine removal: The role of cathodic reduction

In this work, an electric field-enhanced heterogeneous catalytic ozonation (EHCO) was systematically investigated using a prepared FeOx/PAC catalyst. The EHCO process exhibited high sulfadiazine (SDZ) and TOC removal efficiency compared with electrocatalysis (EC) and heterogeneous catalytic ozonation (HCO) process. Almost 100% of SDZ was removed within 2 min, and the TOC removal reached approximately 85% within 60 min. Quenching experiments and EPR analysis suggested that the prominent SDZ and TOC removal performance is supported by the enhanced ·OH generation ability. Further study proved that H2O2 formed by O2 electrochemical reduction, peroxone reaction and electrochemical reduction of ozone contributed to improving ·OH generation. Furthermore, the EHCO system showed satisfactory stability and recyclability compared to conventional HCO systems, and the SDZ and TOC removal rates were maintained at ≥95% and ≥70% in 16 consecutive recycles, respectively. Meanwhile, XPS analysis and Boehm's titration for the FeOx/PAC catalyst used in HCO and EHCO process confirmed that the external electron supply could restrain the oxidation of surface functional groups of PAC and maintain a balance of the Fe(II)/Fe(III) ratio, which proved the critical role of cathode reduction in catalyst in situ regeneration during long consecutive recycles. In addition, the EHCO system could achieve more than 80% SDZ removal within 2 min in different water matrices. These results confirmed that the EHCO process has a wide application perspective for refractory organics removal in actual wastewater.

A comparative study of advanced oxidation-based hybrid technologies for industrial wastewater treatment: An engineering perspective

In this paper, several advanced oxidation-based hybrid technologies were employed to efficiently remove organic pollutants from industrial wastewater. First, the efficiency of hybrid treatment systems composed of coagulation-flocculation, electrochemical oxidation (ECO), and ozone oxidation for removal of several landfill leachates were investigated and the effects of coagulation-flocculation with different chemicals, including polyaluminum chloride, anionic polymers, calcium-based compounds, and sodium carbonate were studied. Coagulation-flocculation/ECO/Ozone oxidation hybrid system achieved the best performance (90.65% removal rate) for fluoride removal, compared with ECO alone and coagulation-flocculation/ECO systems. With a 92.2% fluoride removal rate, Ca(OH)2 achieved the best performance among all calcium-based hybrid treatment technologies. Then, the role of Fenton oxidation/adsorption hybrid technologies in industrial wastewater treatment were also investigated and compared with adsorption and Fenton oxidation alone. Fenton oxidation-adsorption technology achieved a high TOC removal rate of 97%, which was 2.42 times higher than that obtained by activated carbon alone (41.4%) and 1.56 times higher than that achieved by the homogeneous FO process alone (63%). Finally, factors influencing the efficiency of pollutant degradation, including initial pH value, pollutant concentration, and current density were evaluated.

Improved piezocatalytic activity with Ag2O@KNbO3: Mechanisms and performance in organic pollutant degradation

Constructing heterojunctions in a rational and effective way plays a vital role in enhancing the catalytic performance of piezo-/ferroelectric nanomaterials. In this paper, a new material called Ag2O@KNbO3 was fabricated using solvothermal and alkaline deposition methods. This material was found to be an effective catalyst for breaking down various organic pollutants, for example, Orange Ⅱ, Methyl orange, etc. Under optimal conditions, Ag2O@KNbO3 (1:1) demonstrated superior piezocatalytic activity with a degradation efficiency of 97.8% for Orange II within 120 min and a high TOC removal efficiency of 58.4%. The cycle stability for Orange II removal was also excellent. After 5 cycles, the degradation efficiency of Orange II still surpassed 95%. The related enhancement mechanism of the piezocatalytic activity was elaborated in detail, with Ag2O/KNbO3 heterojunctions promoting directed charge movement, reducing impedance of charge transport, and hindering electron-hole recombination, thereby improving charge transfer efficiency. Additionally, OH was confirmed to be the primary active species by electron spin resonance analysis and free radical capture experiment. Notably, a possible degradation pathway of Orange Ⅱ was inferred according to the LC-MS measurement. Overall, this study provides a promising approach for designing and synthesizing new piezoelectric catalytic materials.

Mechanistic study on the synergy of cold plasma and sulfate radical in the degradation of azo and triarylmethane dyes using density functional theory

The activation of persulfate using cold plasma and the synergy of plasma-generated reactive species and SO4•− in mineralization of organic dyes were assessed. In this regard, solutions of crystal violet (CV) as a triarylmethane dye and methyl orange (MO) as an azo dye, were treated with cold plasma, UV-C-activated sulfate radicals, and their combination. The achieved results showed 95% TOC removal, a synergy factor of 1.3 and an energy yield of 1.68 (g kWh−1) for the combined system. The contribution of oxidant species in CV (SO4•− > O2•- > •OH) and MO (SO4•−> O2•- >1O2) degradation was explored. Moreover, analysis of degradation products and density functional theory (DFT) calculations were adopted to find the degradation mechanism based on the minimum energy pathway. Experimental and DFT results revealed that while radical and nucleophilic pathways were the drivers of CV degradation, the electrophilic attack of oxidants was a more plausible mechanism for MO degradation. Additionally, a comparison of the results of different DFT methods with experimental values showed that the Kohn–Sham DFT yielded more accurate results compared to recommended double hybrid methods. Analysis of a treated real wastewater revealed that the background constituents had negligible effects on MO and CV degradation. The high TOC removal efficiency of the combined system suggests its feasibility for treating wastewater from fertilizer and pharmaceutical production facilities.

In-situ degradation of phenol using CuMgFe-LDO catalyst and assessment of its service life in the persulfate activation process

Layered double oxides (LDOs) have been proven effective and reusable materials in removing phenols. However, the service life of LDOs in an application remains unclear. This study optimized the properties of CuMgFe-LDO and assessed its service life for in-situ groundwater remediation. Phenol degradation in CuMgFe-LDO-activated persulfate (PS) system with various groundwater matrix was analyzed. Results showed improved phenol degradation with increasing Cu content and calcination temperature in LDO production, with a decrease in degradation beyond a certain level of Cu. Phenol removal was slightly influenced by fulvic acid and sodium humate below 20.0 mg/L but strongly affected by 1.0 mmol/L of SO42− and HCO3−. A high TOC removal of 80 % in all three recycled tests was found within 30 min, with intermediate products identified as benzoquinone, fumaric/maleic acid, and finally, oxalic and acetic acid. The CuMgFe-LDO showed demonstrated exemplary performance in a continuously flowing phenol and PS solution column, with a long service life of 12 days and low copper leaching (1.8 mg/L) at pH 6.55. This study supports the potential of the CuMgFe-LDO-activated PS system for remediating groundwater contaminated with phenolic compounds and mitigating acidification from PS use.

Efficient degradation of sulfamethoxazole in heterogeneous Electro-Fenton process with CeO2@MoS2@GF modified cathode: Mechanism and degradation pathway

Developing the efficiently degradation of organic pollutants in heterogeneous Electro-Fenton (E-F) process was still a challenge. In this work, the synthesized CeO2 and MoS2 were used to modify graphite felt (GF) for obtaining a novel electrode defined as CeO2@MoS2@GF, constructing a heterogeneous E-F system that could in-situ electrically generate and activate H2O2, thereby efficiently degrading sulfamethoxazole (SMX) in wastewater. The electrochemical performance and catalytic activity of CeO2@MoS2@GF electrode was evaluated by electrochemical tests (LSV/EIS/CV curves and RDE test) and effect of different experimental conditions (SMX concentration, current density and initial pH values). The E-F system using CeO2@MoS2@GF electrode realized rapid SMX degradation of 90% within 20 min and high TOC removal of 87.6% within 120 min, this excellent performance attributed to the efficient conversion between Ce(Ⅳ) and Ce(Ⅲ) under the presence of Mo(IV), as well as the effective utilization of oxygen vacancies. Furthermore, the E-F process mediated by CeO2@MoS2@GF electrode had excellent stability and cycle degradation performance as well as low energy consumption (9.1 kWh kg−1). Besides, this system presented a satisfactory detoxification effect towards degradation intermediates with high toxicity, as well as high adaptability in different water sources. Finally, the mechanism of E-F system using CeO2@MoS2@GF electrode and possible SMX degradation pathways were proposed. This work offered inspiration for developing superior heterogeneous E-F cathode materials and contributed to the practical application of E-F process in wastewater treatment.

Electrochemical oxidation of phenol in chloride containing electrolyte using a carbon-coated Ti4O7 anode

Magnéli-phase Ti4O7 is an excellent anode material for electrochemical advanced oxidation process (EAOP). However, the development of Ti4O7 electrodes is always limited by the high cost and high energy consumption in their preparation process. In this study, the carbon-coated Ti4O7 electrode was successfully synthesized by an in-situ pyrolysis method, which exhibited high specific surface area (143.8 m2 g−1) and efficient electron transfer (47.3 Ω). The accelerated service life was measured to be 102.5 h, demonstrating its excellent stability. EAOP performance of the C-coated Ti4O7 electrode was evaluated under various operating conditions. The result showed that a complete degradation of phenol (100 mg L−1) was obtained in 60 min, under the condition of 0.1 M NaCl electrolyte and 20 mA cm−2 current density. Owing to the high oxygen evolution potential (OEP, 2.25 V vs. RHE) of the C-coated Ti4O7 electrode, high TOC removal ratio (68.9%) and low energy consumption (113.8 kWh kg−1TOC) were achieved under the optimal condition. Moreover, the mechanism of phenol degradation was investigated by linear sweep voltammetry (LSV) and free radical scavenging experiments. The results indicated that the degradation of phenol can be mainly attributed to the synergistic effects between adsorbed ·OH (M(·OH)) and Cl−, rather than the direct electron transfer process (DET) on the surface of the C-coated Ti4O7 electrode. This study provides an efficient strategy for the mineralization of phenolic wastewater by the C-coated Ti4O7 electrode.

Influence of Microwave Radiation on Pollutant Removal and Biomethane Production Efficiency in Anaerobic Treatment of High-Load Poultry Wastewater

The growing consumption of poultry meat has spurred the development of meat-processing plants and an associated rise in wastewater generation. Anaerobic digestion is one of the preferred processes for treating such waste. The current push towards biogas upgrading and out-of-plant use necessitates new, competitive ways of heating digesters. One such alternative is to use electromagnetic microwave radiation (EMR). The aim of the study was to assessment how EMR used as a heat source impacts the anaerobic processing of high-load poultry slaughterhouse wastewater (H-LPSW) and its performance. Microwave heating (MWH) was found to boost the CH4 fraction in the biogas under mesophilic conditions (35 °C) as long as the organic load rate (OLR) was maintained within 1.0 kgCOD/dm3·d to 4.0 kgCOD/dm3·d. The best performing variant—EPM heating (55 °C), OLR = 3.0 kgCOD/dm3·d, HRT = 5 days—produced 70.4 ± 2.7% CH4. High COD and TOC removal, as well as the highest biogas yields, were achieved for loadings of 1.0 gCOD/dm3·d to 4.0 gCOD/dm3·d. Effluent from the EMR-heated reactors (1.0 gCOD/dm3·d) contained, on average, 0.30 ± 0.07 gO2/dm3 at 55 °C and 0.38 ± 0.10 gO2/dm3 at 35 °C. The corresponding COD removal rates were 97.8 ± 0.6% and 98.1 ± 0.4%, respectively. The 5.0 gCOD/dm3·d and 6.0 gCOD/dm3·d OLR variants showed incremental decreases in performance. Based on the polymerase chain reaction results of 16S rDNA analysis, diversity of bacterial communities were mostly determined by OLR, not way of heating.

Performance and Bacterial Characteristics of Aerobic Granular Sludge in Treatment of Ultra-Hypersaline Mustard Tuber Wastewater

Mustard tuber wastewater (MTW) is an ultra-hypersaline high-strength acid organic wastewater. Aerobic granular sludge (AGS) has been demonstrated to have high tolerance to high organic loading rate (OLR), high salinity, and broad pH ranges. However, most studies were conducted under single stress, and the performance of AGS under multiple stresses (high salinity, high OLR, and low pH) was still unclear. Herein, mature AGS was used to try to treat the real MTW at 9% salinity, pH of 4.1–6.7, and OLR of 1.8–7.2 kg COD/m3·d. The OLR was increased, and the results showed that the upper OLR boundary of AGS was 5.4 kg COD/m3·d (pH of 4.2) with relatively compact structure and high removal of TOC (~93.1%), NH4+-N (~88.2%), and TP (~50.6%). Under 7.2 kg COD/m3·d (pH of 4.1), most of the AGS was fragmented, primarily due to the multiple stresses. 16S rRNA sequencing indicated that Halomonas dominated the reactor during the whole process with the presence of unclassified-f-Flavobacteriaceae, Aequorivita, Paracoccus, Bradymonas, and Cryomorpha, which played key roles in the removal of TOC, nitrogen, and phosphorus. This study investigated the performance of AGS under multiple stresses, and also brought a new route for highly-efficient simultaneous nitrification–denitrifying phosphorus removal of real MTW.

Electro-Fenton mineralization of real textile wastewater by micron-sized ZVI powder anode.

The diverse compositions and complex nature of the textile wastewater make it imperative to find an economical and suitable degradation pathway. The degradation of real textile wastewater on a novel heterogeneous electro-Fenton system was carried out with a composite anode of magnetically fixed micron ZVI coupling with a Ti/RuO2-IrO2 sheet. The influences of different variables such as mZVI dosage, H2O2 amount, applied voltage and pH value on both total organic carbon and chemical oxygen demand removal efficiencies and energy consumption were investigated. The optimized parameters were simultaneously verified by using electrochemical workstation Tafel curves and Nyquist plots. The optimal operating conditions for evaluating the wastewater treatment were H2O2 dosage of 0.10 mol·L-1, applied voltage of 5.0 V, mZVI amount of 1.0 g·L-1 and initial pH value of 3.0. The high TOC and COD removal efficiencies of 92.44 and 82.84% could be achieved simultaneously in 60 min, respectively. XRD, XPS and SEM-EDS were used to investigate the interaction between the pollutant and the mZVI. GC-MS analysis was performed on untreated and treated wastewater to determine the degradation of pollutants in dyeing wastewater during the electro-Fenton process and to effectively propose a suitable degradation mechanism for this system.

Treatment of Sugar Industry Wastewater by Using Subcritical Water as a Reaction Media

AbstractThe sugar industry is one of the most wastewater‐producing industries and it contains high content of organic and inorganic substances. Treating and reusing wastewater has significant importance because sugar industry needs to use a high volume of water. In this study, sugar industry wastewater was treated under subcritical conditions and the impacts of reaction temperature and duration over TOC removal percentage were investigated. Additionally, the impact of NaOH concentration over TOC removal percentage was examined. The highest TOC removal was obtained almost 95 % in the presence of 0.1 M of NaOH at 240 °C for 90 min of reaction duration. Treatment of sugar industry wastewater by subcritical water oxidation followed the second‐order reaction kinetic model and the activation energy was found as 11.41 kJ/mol. Furthermore, the intermediate products were identified via GC‐MS.

Aerobic granular sludge treating hypersaline wastewater: Impact of pH on granulation and long-term operation at different organic loading rates

pH is one of the major parameters that influence the granulation and long-term operation of aerobic granular sludge (AGS). In hypersaline wastewater, the impact of pH on granulation and the extent of organic loading rate (OLR) that AGS can withstand under different pH are still not clear. In this study, AGS was cultivated at 3% salinity in three sequencing batch reactors with influent pH values of 5.0, 7.0, and 9.0, respectively, and the OLR was stepwise increased from 2.4 to 16.8 kg COD/m3·d after the granules maturation. The results showed the satisfactory granulation and organic removal under different influent pH conditions, in which the granulation was completed on day 43, 23, and 23, respectively. Neutral influent was the most appropriate for development of salt-tolerant aerobic granular sludge (SAGS), while acidic environment induced the formation of fluffy filamentous granules, and alkaline environment weakened the granule stability. Metagenomic analysis revealed the similar microbial community of neutral and alkaline conditions, with the predominance of genus Paracoccus_f__Rhodobacteraceae. While in acidic environment, fungus Fusarium formed the skeleton of filamentous granules and functioned as the carrier of bacteria including Azoarcus and Pararhodobacter. With the elevation of OLR, SAGSs were found to maintain the compact structure under OLRs of 2.4, 7.2, and 2.4 kg COD/m3·d, and obtain high TOC removal (>95.0%) under OLRs of 7.2, 14.4, and 14.4 kg COD/m3·d, respectively. For hypersaline high-strength organic wastewater, satisfactory TOC removal could also be obtained at broad pH ranges (5.0–9.0), in which neutral environment was the most suitable and acidic environment was the worst. This study contributed to a better understanding of SAGS granulation and treatment of hypersaline high-strength organic wastewater with different pH values.

Electro-activating of peroxymonosulfate via boron and sulfur co-doped macroporous carbon nanofibers cathode for high-efficient degradation of levofloxacin.

To address the difficulty of precisely regulating the two-electron oxygen reduction reaction (2e-ORR) and investigate the synergistic effect of hydrogen peroxide (H2O2) and peroxymonosulfate (PMS), a heterogeneous electro-catalyst was synthesized via carbonation of boron (B) and sulfur (S) co-doping electrospun nanofibers containing iron and cobalt (B, S-Fe/Co@C-NCNFs-900), and used to degrade levofloxacin (Levo) in the electro-activating PMS with self-made cathode material (E-cathode-PMS) system. The morphological, structural, and electrochemical characteristics have been investigated. The results showed that B and S co-doping could remarkably enhance electron transfer and manage two-electron oxygen reduction, which was more favorable for H2O2 generation. Levo degradation efficiency could reach 99.63% with a reaction rate of 0.3056min-1 in 20min under the appropriate conditions (pH = 4, current = 20mA, and [PMS] = 8.0mM). The steady-state concentration of singlet oxygen (1O2) was calculated to be 669.17×10-14 M, which was 15.42, 29.74, and 45.00 times respectively than that of HO2·/O2·- (43.40×10-14 M), ·OH (22.25× 10-14 M) and SO4-·(14.87× 10-14 M), signifying that 1O2 was the predominant reactive oxygen species (ROS) involved in Levo removal. The high TOC removal (74.19%), low energy consumption (0.14kWhm-3 order-1), few intermediates toxicity, and excellent Levo degradation efficiency for complex wastewater with various anions and matrixes showed the prospective practical applications of the E-cathode-PMS system. Overall, this study provides a useful strategy to regulate and control the 2e-ORR pathway.

Enhanced degradation of DDT using a novel iron-assisted hydrochar catalyst combined with peroxymonosulfate: Experiment and mechanism analysis

Poplar wood (PW) hydrochar modified by iron (Fe@HC) was prepared greenly by one-step hydrothermal method. The adsorption and degradation performance of DDT was investigated in a heterogeneous advanced oxidation system (Fe@HC/PMS) formed by Fe@HC collaborated with peroxymonosulfate (PMS). The effects of Fe@HC dosage, PMS dosage and DDT initial concentration were quantitatively analyzed. The results showed that DDT removal efficiency can reach to 88.62% in 240 min under optimal conditions (4 g/L Fe@HC, 10 mM PMS, 0.5 mg/L DDT, 5.5 pH0) in Fe@HC/PMS system. Furthermore, Fe@HC/PMS system exhibited high degradation rate and TOC removal efficiency for the removal of various organic contaminants. The influence mechanisms of Fe@HC/PMS system on DDT adsorption and degradation were proposed based on electron paramagnetic resonance (EPR) testing analysis and radical quenching experiments. Based on the mechanism analysis, the influence of Fe@HC/PMS on DDT removal efficiency can be concluded in the order: Active substance indirect degradation (60.95%) > Fe@HC direct degradation (10.13%) > Fe@HC adsorption (17.54%). Among active substance indirect degradation, SO4•−, •OH, O2•− and 1O2 occupied 27.56%, 15.74%, 5.33% and 12.32%, respectively. Moreover, DDT degradation intermediates were detected by a gas chromatography-mass spectrometer (GC-MS) to predict DDT degradation pathways. This study provided a green progress for the reuse of biomass resources and a new way for the enhanced degradation of DDT.

Comparison of homogeneous and heterogeneous electrochemical advanced oxidation processes for treatment of textile industry wastewater

This study aimed at understanding the influence of the generation of oxidants in a heterogeneous way at boron-doped diamond (BDD) anode (anodic oxidation (AO)) or homogeneously in the bulk (electro-Fenton (EF)) during treatment of a textile industry wastewater. Both processes achieved high TOC removal. A yield of 95 % was obtained by combining EF with BDD anode during 6 h of treatment. The EF process was found to be faster and more efficient for discoloration of the effluent, whereas AO was more effective to limit the formation of degradation by-products in the bulk. An advantage of AO was to treat this alkaline effluent without any pH adjustment. Operating these processes under current limitation allowed optimizing energy consumption in both cases. However, using BDD anode led to the formation of very high concentration of ClO3-/ClO4- from Cl- oxidation (even at low current density), which appears as a key challenge for treatment of such effluent by AO. By comparison, EF with Pt anode strongly reduced the formation of ClO3-/ClO4-. Operating EF at low current density even maintained these concentrations below 0.5 % of the initial Cl- concentration. A trade-off should be considered between TOC removal and formation of toxic chlorinated by-products.