Organic Wastewater Treatment Research Articles

Solar-powered flow-through catalytic evaporator for high-performance water desalination and synergistic pollutant degradation

Solar interfacial evaporation has been considered one of the most promising strategies to address freshwater scarcity. It is of great interest to explore means of expanding the utilization of solar interfacial evaporation for organic wastewater treatment to capture freshwater. To this end, it is proposed herein that a unidirectional flow-type solar-powered catalytic evaporator is fabricated as a unique integrated device with efficient vapor generation and organics degradation capability, giving rise to simultaneously achieving collection of freshwater and treatment of organics. Benefitting from the flow-through interfacial evaporation and the rational design of the high-performance array-type catalytic evaporative material composed of polydopamine (PDA)-coated CdS photocatalysts on carbon cloth (CC) substrate, the as-built solar-powered catalytic evaporator demonstrates excellent evaporation rate and organic treatment efficiency of 1.93 kg m−2 h−1 and 90.7 %, respectively, well exceeding those of the initial, un-designed evaporator (1.63 kg m−2 h−1 and 60.3 %). This work may provide a new strategy for the treatment of organic wastewater with versatility based on solar interfacial catalytic evaporation technology.

Process Energy and Material Consumption Determined by Reaction Sequence: From AAO to OHO

The anaerobic-anoxic-oxic (AAO) process is one of the most widely used processes for treating industrial organic wastewater, and it has shown significant effectiveness in the removal of organic compounds, as well as denitrification and phosphorus removal. However, for the treatment of industrial organic wastewater, this anaerobic preposition and aerobic postposition process has exposed various limitations. Therefore, for this type of wastewater, the oxic-hydrolytic and denitrification-oxic (OHO) treatment process has been proposed and developed based on the principles of three-sludge separation and fluidization. This study integrated operational data from 203 coking wastewater treatment plants worldwide, and the two-step nitrification-denitrification activated sludge model No.3 (TCW-ASM3) was used for comparative analysis of the pollutant removal efficiency and total operating cost of the AAO process and the OHO process in the face of characteristic pollutants in coking wastewater. The results indicate that the full-scale OHO process achieved removal efficiencies of up to 3784 mg/L for chemical oxygen demand (COD) and 297 mg/L for total nitrogen (TN). The theoretical total cost for OHO and AAO were 9.75 and 14.38 CNY/m3, respectively. The pre-treatment aerobic process effectively reduces the biological toxicity of high-toxicity and refractory industrial wastewater, and the three-sludge system provides a stable living space for functional microorganisms, the combination of multi-mode denitrification processes offers new possibilities for treating similar types of industrial wastewater.

A Supramolecular Polymer Network Based on Chitosan and Porphyrin and Its Application as an Adsorbent for Selective Removal of Dyes from Water

AbstractEnvironmentally friendly, high adsorption efficiency, and recyclable adsorbents meet the actual needs of organic dye wastewater treatment. Driven by noncovalent interactions between chitosan (CS) and 5,10,15,20‐tetra(4‐hydroxyphenyl) porphyrin sodium (THPPNa) under acidic conditions, a supramolecular polymer network is constructed. The supramolecular polymer network is applied as an excellent adsorbent for the removal of organic dyes from water with high efficiency. In addition, the supramolecular adsorbent shows excellent selectivity for the removal of organic anionic dyes from the mixtures of organic anionic and cationic dyes in water. Furthermore, the removal efficiency of anionic dyes of the network adsorbent keeps over 95% even after five adsorption–desorption cycles, indicating its reusability. This supramolecular polymer network shows its great potential as a low‐cost, effective, and selective adsorbent for removing organic dyes from water.

High performance lamellar structured graphene oxide nanocomposite membranes via Fe3O4-coordinated phytic acid control of interlayer spacing for organic solvent nanofiltration (OSN)

Graphene oxide (GO), a 2D nanomaterial known for its precise molecular sieving, holds potential for Organic Solvent Nanofiltration (OSN) and wastewater treatment. However, challenges such as thin interlayer spacing, extended diffusion pathways, and susceptibility to dehydration and negative charge-induced swelling limit its separation performance. To overcome these limitations, Herein, we have fabricated novel Fe3O4 coordinated PhA intercalated GO nanocomposite membranes. Impressively, these nanocomposite membranes exhibited remarkable separation efficiency for dyes, pesticides, and pharmaceutical ingredients, addressing the drawbacks associated with pristine GO membranes and enhancing their overall performance. The optimum G10(1)/P1.5-F100µL nanocomposite membrane displayed impressive solvent permeance of 40.43, 33.45, 20.70, 16.24, and 5.6 L/m2 h bar for acetone, methanol, water, ethanol, and IPA, respectively, while maintaining a rejection rate of ≥98.97 % for the MO dye (MW = 327.33 g/mol). Furthermore, the membrane exhibited outstanding efficiency in separating tetracycline (TC) in ethanol (≥97.97 %) and Pendimethalin (PM) in water (≥99.88 %). Additionally, it demonstrated high rejection capabilities for MB (≥98 %) and CR (≥98.78 %) in harsh DMF solvent. Importantly, the nanocomposite membrane displayed outstanding durability throughout continuous separation of Pendimethalin (PM) in a water solution over a period of 168 h. The PM separation remained nearly unchanged for the entire 168-h duration, demonstrating high mechanical strength and chemical stability. Additionally, the single nanocomposite membrane showcased high efficiency in feed change separation, successfully separating CR in ethanol and PM in water. These results, compared to the other GO-based nanocomposite membranes, demonstrate the exceptional stability and immense potential for real OSN applications.

Regulating Fe(III) spin state by anchoring iron on titanium dioxide for enhancing photo-Fenton treatment of tetracycline wastewater

Tetracycline (TC) wastewater can hardly be treated effectively by conventional processes due to its stable chemical structure and its refractoriness to biodegradation. Photo-Fenton technology based on iron-based catalyst exhibits excellent capacity on organic wastewater treatment, but current iron-based catalyst materials exist crucial problems such as slow regeneration of Fe(II) and low utilization of H2O2. In this study, Fe atom was anchored on TiO2 to regulate the spin state of Fe to prepare a new efficient photo-Fenton material. The results showed that the removal of TC by Fe2O3-TiO2(high spin, HS) can reach 94.7%, while the removal of TC by Fe-TiO2(low spin, LS) was only 83.0%. The Fe2O3-TiO2(HS) maintained high photo-Fenton activity after five cycles, and the TC removal rate still reached 91.8%. Fe2O3-TiO2(HS) had a narrow bandgap and excellent photogenerated charge separation properties, which facilitates the generation of photogenerated charges, improves the electron transfer, and accelerates the redox cycle of Fe(III)/Fe(II). The electrons in the 3d orbital of Fe2O3-TiO2(HS) are more easily to cross the antibonding orbital of the H2O2, which is conducive to the adsorption of H2O2 and generation of ·OH to accelerate TC degradation. This study provides a new photo-Fenton material for the treatment of TC wastewater and offers a new strategy for the development of photo-Fenton.

Fouling behavior of nanofiltration membrane during the refining treatment of morphlines-dominant reverse osmosis concentrate

Nanofiltration (NF) has been proven to be with great potential for the separation of morpholines with molecular weight less than 200 Da in refining reverse osmosis concentrate (ROC), but its application is significantly restricted by the membrane fouling, which can reduce the rejection and service time. To enable the long-term operation stability of nanofiltration, this work focuses on the fouling behavior of each substance in the hydrosaline organic solution on nanofiltration membrane, aiming to give insight into the fouling mechanism. To this end, in this work, the effects of salts (i.e NaCl and Na2SO4), organic substances (including N-(2-hydroxypropyl)morpholine(NMH) and 4-morpholineacetate(MHA)) and representative divalent ions (Ca2+ and Mg2+) on the performance and physicochemical properties of DK membrane were systematically investigated. The results show that both salts and organics can induce DK membrane swelling, leading to an increase of the mean effective pore size. After the filtration of Na2SO4–NaCl–H2O, the mean pore size increased by 0.002 nm, resulting in the decrease of the removal ratio of NMH and MHA for 3.82% and 13.10%, respectively. With static adsorption of NMH and MHA, the mean pore size of DK membrane increased by 0.005 and 0.003 nm. The swelling slowed the entrance of more organic molecules into membrane pores. Among them, MHA led to the terrible irreversible pore blocking. As the concentration of Ca2+ increased, gypsum scaling was formed on the membrane surface. During this process, NMH and MHA played different roles, i.e. NMH accelerated the CaSO4 crystallization while MHA inhibited. As a conclusion, the fouling behavior of substances in the high saline organic wastewater on DK membrane were systematically revealed with the fouling mechanisms proposed, which could provide an insightful guidance for membrane fouling control and cleaning in the treatment of high salinity and organic wastewater.

A new strategy for clean utilization of zinc oxide dust: Preparation of spinel zinc ferrite by solid phase reaction and its catalytic degradation of organic wastewater

The resource utilization of zinc oxide dust (ZOD) is mainly focused on the efficient recovery of zinc by acid leaching at present. Because of a large amount of iron in ZOD and zinc components existing in multi-phase, the problems of low zinc recovery and the separation of zinc and iron ions in the leaching solution are unavoidable. Considering the characteristics of ZOD and the advantages of spinel zinc ferrite (ZnFe2O4) in the advanced oxidation degradation of organic wastewater, a new strategy for clean utilization of ZOD is proposed. The leaching efficiency of soluble zinc components in ZOD reached 96.7 % by selective dissolution with low concentration sulfuric acid solution, and the leaching solution without iron ions can be directly used for electrolytic zinc recovery. The insoluble components of zinc and iron in the leaching residue were converted into ZnFe2O4 by solid phase roasting. By adjusting the roasting temperature, time and molar ratio of Fe/Zn in roasting process, the proportion of zinc elements in the form of ZnFe2O4 reached 99.56 % and a single spinel zinc ferrite product was obtained. Zinc ferrite product activated by ball milling for 2 h (ZFO-2) showed very high catalytic activity in the treatment of organic wastewater by peroxonosulfate (PMS). In the presence of 1 mM PMS and 1 g/L ZFO-2 at 20 °C, the ZFO-2/PMS system achieved a removal rate of over 90 % within 40 min for wastewater containing RhB, MO and MG (10 mg/L). In addition, ZFO-2 is ferromagnetic and easily recovered by magnetic separation. The new strategy proposed in this paper takes into account the efficient recovery of soluble zinc components and the cooperative high-value utilization of insoluble components of zinc and iron in ZOD, which is a comprehensive utilization method with more sustainable resource allocation.

Exploring electron-transfer pathways in co-pyrolyzed waste-derived carbocatalyst for enhanced peroxydisulfate activation

Heterogeneous catalyst-activated peroxydisulfate (PDS) process has great potential in environmental remediation, but its complex preparation process, high cost, low efficiency, and unclear mechanism hinder its practical application. To overcome these limitations, we introduced an innovative metal-free biochar catalyst (SCSS-NC) derived from waste biomass through co-pyrolysis of shrimp shell and sludge with nitrogen doping. This catalyst improved its performance, achieving 78.45 % degradation of tetracycline, outperforming sludge carbon/PDS systems (46.89 %) and shell carbon/PDS systems (22 %) under the dosage of PDS (0.5 mM) and catalysts (0.5 g/L) within 60 min. This improvement stems from its increased surface area, porosity, and electron transport capabilities. Quenching experiments, delayed contaminant addition experiments, and EPR results demonstrated that the SCSS-NC/PDS system relies on electron transfer, in which activated PDS binds to the catalyst surface, forming a highly reactive composite [SCSS-NC/PDS]* to degrade pollutants. The open-circuit potential and linear scanning voltammetry results confirm the existence of an electron transfer pathway, while the situ Raman spectroscopy results validate the presence of the composite [SCSS-NC/PDS]*. The DFT theoretical calculations provide further confirmation of the conductivity, low energy barrier, and ability to expedite electron transfer exhibited by SCSS-NC. The catalyst performance and characterization before, after, and post-recovery from the reaction pinpoint key active sites: pore adsorption, sp2 graphitic carbon, and graphitic nitrogen doping sites. The SCSS-NC/PDS system demonstrates robust anti-interference capability, suggesting its potential for practical organic wastewater treatment. This study provides novel insights into economical carbocatalyst and their mechanisms for environmental applications.

Optimization of sulfate reduction and methanogenesis via phase separation in a two-phase internal circulation reactor for the treatment of high-sulfate organic wastewater

To enhance the performance of the internal circulation (IC) reactor when treating high-sulfate organic wastewater, a laboratory-scale two-phase IC reactor with distinct phase separation capabilities was designed, and the sulfate reduction and methanogenesis processes were optimized by segregating the reactor into two specialized reaction zones. The results demonstrated that the first and second reaction areas of the two-phase IC reactor could be maintained at 4.5–6.0 and 7.5–8.5, respectively, turning them into the specialized phase for sulfate reduction and methanogenesis. Through phase separation, the two-phase IC reactor achieved a COD degradation and sulfate reduction efficiency of more than 80% when the influent sulfate concentration exceeded 5,000 mg/L, which were 32.32% and 16.04% higher than that before phase separation. Functional analyses indicated a greater activity of both the dissimilatory and assimilatory sulfate reduction pathways in the acidogenic phase, largely due to a rise in the relative abundance of the genera Desulfovibrio, Bacteroides, and Lacticaseibacillus, the primary carriers of sulfate reduction functional genes. In contrast, all the acetoclastic, hydrogenotrophic, and methylotrophic methanogenesis pathways were inhibited in the acidogenic phase but thrived in the methanogenic phase, coinciding with shifts in the genus Methanothrix, which harbors the mcrA, mcrB, and mcrG genes essential for the final transformation step of all three methanogenesis pathways.

Engineered lignocellulosic based biochar to remove endocrine-disrupting chemicals: Assessment of binding mechanism

The safety and health of aquatic organisms and humans are threatened by the increasing presence of pollutants in the environment. Endocrine disrupting chemicals are common pollutants which affect the function of endocrine and causes adverse effects on human health. These chemicals can disrupt metabolic processes by interacting with hormone receptors upon consumptions by humans or aquatic species. Several studies have reported the presence of endocrine disrupting chemicals in waterbodies, food, air and soil. These chemicals are associated with increasing occurrence of obesity, metabolic disorders, reproductive abnormalities, autism, cancer, epigenetic variation and cardiovascular risk. Conventional treatment processes are expensive, not environment friendly and unable to achieve complete removal of these harmful chemicals. In recent years, biochar from different sources has gained a considerable interest due to their adsorption efficiency with porous structure and large surface areas. biochar derived from lignocellulosic biomass are widely used as sustainable catalysts in soil remediation, carbon sequestration, removal of organic and inorganic pollutants and wastewater treatment. This review conceptualizes the production techniques of biochar from lignocellulosic biomass and explores the functionalization and interaction of biochar with endocrine-disrupting chemicals. This review also identifies the further needs of research. Overall, the environmental and health risks of endocrine-disrupting chemicals can be dealt with by biochar produced from lignocellulosic biomass as a sustainable and prominent approach.

Flexible bifunctional wood-derived water filtration/photo-Fenton membrane for efficient purification of mixed organic wastewater

Membrane filtration technology demonstrates excellent continuous processing capability in organic wastewater treated processes, which is usually applied in continuous industrial processes. However, it still faces a contradiction between membrane flux and treatment efficiency. In this study, a flexible wood-based photocatalytic membrane with high membrane flux and exceptional photofenton performance was developed via partial fragment wood components and uniform loading of multi-metal oxide nanocatalysts, which breaks mentioned contradiction. The homogeneous and efficient wood-based dual-function water filtration/photofenton system was established by leveraging the directional porous structure of wood in conjunction with the nanocatalysts while adjusting their ratios, enabling effective purification of highly concentrated mixed organic wastewater. Under one solar intensity and negative pressure filtration (0.03 MPa), the system treated a mixed solution containing Rhodamine B, phenol, and tetracycline at a concentration of 280 mg L−1 with the removal efficiencies of 100 %, 93.4 %, and 90.2 %, respectively, and the membrane flux could up to 315.3 Lm−2 h−1 within one hour. The membrane showed a good recycling performance, and the decay rates were all below 5 % after five cycles. This wood-based dual-function water filtration/photo-Fenton system provides a new approach for the continuous dynamic treatment of high-concentration organic wastewater on an industrial scale.

Molecular biological mechanism of fillers with surface micro-electric field to enhance biodegradation of kitchen-oil wastewater

The kitchen-oil wastewater is characterized by a high concentration of organic matter, complex composition and refractory pollutants, which make wastewater treatment more difficult. Based on the study of using micro-electric field characteristic catalyst HCLL-S8-M to enhance the electron transfer between microorganisms in kitchen-oil wastewater which further improved the COD removal rate, we focus on the microbial community, intracellular metabolism and extracellular respiration, and make an in-depth analysis of the molecular biological mechanisms to microbial treatment in wastewater. It is found that electroactive microorganisms are enriched on the material surface, and the expression levels of cytochrome c and riboflavin genes related to electron transfer are up-regulated, confirming that the surface micro-electric field structure could enhance the electron transfer between microbial species and improve the efficiency of wastewater degradation. This study provides a new idea for the treatment of refractory organic wastewater.

Catalytic air oxidation of biogas slurry using Cu sub-nanocluster supported by mesoporous TiZrO4 and protected by SiO2 shell

Biogas slurry, an inevitable outcome of anaerobic digestion (AD), is a treatment burden for urban environmental management. In this study, two kinds of biogas slurry (slurry J and slurry C), collected from the AD plants in Japan and China, were treated using novel TiZrO4 @Cu and TiZrO4 @Cu@SiO2 multilayered hollow spheres containing Cu sub-nanoclusters as the catalyst. The results showed that the chemical oxygen demand (COD) was removed by 63 % for slurry J and 44 % for slurry C after 5 h. The Cu sub-nanoclusters acted as co-catalysts and active centers, facilitating rapid electron transfer to oxygen molecules and forming highly reactive •O2− and •OH species (Use slurry J as the based solution). These free radicals cleaved the interconnecting bonds between benzene rings, disintegrated the ring structure, formed intermediate compounds such as n-hexylic acid, and ultimately mineralized organic pollutants in biogas slurry into CO2 and H2O. At the same time, TiZrO4 @Cu@SiO2 had excellent stability due to the protection of the SiO2 shell and reduced threefold Cu leaching than TiZrO4 @Cu. The COD removal rate was always 60 % in six cycles in the slurry J. The new catalyst ensured the high performance of catalytic air oxidation at low temperatures, which has significant potential as an environmentally friendly and energy-saving method for organic wastewater treatment.

High-performance hydrophobic aerogel based on nanocellulose, graphene oxide, polyvinyl alcohol, and hexadecyltrimethoxysilane: Structure, properties, and applicability

The most prevalent kinds of contaminants found in water sources are oil and organic substances, which are often present in either spilled or emulsified states. Due to the vast surface area and porous structure, nanocellulose aerogel is an environmentally benign material widely employed for its efficacy in adsorbing oils and organic pollutants. In this study, an aerogel composed of nanocellulose (CNF), graphene oxide (GO), and polyvinyl alcohol (PVA), subsequently modified with hexadecyltrimethoxysilane (HDTMS), exhibited a well-defined structure and demonstrated proficient removal of waste oil and certain organic solvents from water at high speed. By a simple and cheap preparation method from solution mixing and freeze-drying, the resultant aerogel has a high porosity of 97.26 %, a light density of 0.0036 g/cm3, a mesoporous structure with a mean pore diameter of 3.5 nm, and a surface area of 15.717 m2/g. Aerogel exhibits pronounced superhydrophobic behavior, achieving a contact angle of up to 152°, thereby substantially impeding water permeation through its structure in experimental assessments of selectivity and efficacy in separating oil-water mixtures. According to Langmuir isotherm model, DO adsorption occurred in a monolayer. CNF/GO/PVA/HDTMS aerogel exhibited a maximum adsorption capacity of 322.58 mg/g, with the pseudo-second-order model effectively representing this adsorption process. Furthermore, the CNF/GO/PVA/HDTMS aerogel displays a strong adsorption capability towards oils and organic solvents, with a range of 10–25 times the original volume of the aerogel. Another feature of the resultant aerogel is its good deemulsion ability on both water-in-oil and oil-in-water emulsions. The pump extraction method is more effective than the extraction method in oil recovery and reuse of the aerogel. The results obtained in the study show a potential environmentally friendly material for the treatment of oily and organic solvent wastewater from industries.

Hydrothermal preparation of magnetic recyclable In-doped MoO3/SrFe12O19 ternary nanocomposites with enhanced visible-light-driven photocatalytic performance

SrFe12O19 as a novel magnetic matrix has drawn increasing attention in photocatalysis. In the current study, a novel magnetically recoverable In-MoO3/SrFe12O19 ternary composite photocatalyst was fabricated with the hydrothermal method, and the photocatalytic activity was evaluated by degrading rhodamine B (RhB) solution through simulated solar irradiation. The results demonstrated that the outstanding degradation rate of RhB (96.5 %) could be achieved within 70 min when the mass ratio of both doped In and SrFe12O19 in the ternary composite photocatalyst was 5 % (5-IMS-5). The enhancement of the photocatalytic degradation performance was mainly related to the self-sensitization of RhB, the magnetic field effect of SrFe12O19, and the introduction of impurity energy levels by In doping. More importantly, the degradation rate of RhB by 5-IMS-5 was still up to 90.8 % after 4 times of recycling, verifying that the prepared ternary composite sample has good recyclability and stability. This study proves a novel ternary composite photocatalyst that can be used for organic wastewater treatment, and its photocatalytic degradation mechanism provides great reference significance for the synthesis of other SrFe12O19-based magnetic semiconductor photocatalysts.

Ultra-high selective removal of Congo red and Ciprofloxacin using unusual LDO modified biochar: Influence of emerging pollutants and application attempts

The porous biochar materials serve as effective adsorbents in water treatment. In this study, layered-double-hydroxide (LDH)(MgAl) was dispersed onto waste poplar powder through the co-precipitation method, followed by pyrolysis to prepare layered-double-oxides (LDO)/poplar carbon (CL-800) for ultra-high adsorption of Congo red (CR) and Ciprofloxacin (CIP). The CL-800 adsorbent possessed a well-developed layered porous structure that provides numerous adsorption sites and transport channels for dyes and antibiotics. Notably, CL-800 exhibited a significantly elevated level of selectivity and adsorption capacity towards CR and CIP reaching 93.0, 84.7 % and 4841.2, 744.0 mg/g, respectively. Various factors were considered to investigate the influence on CR and CIP adsorption, such as ion types, microplastics, and perfluorooctanoic acid. The adsorption capacity in complex water systems were also explored where CL-800 presented excellent removal efficiencies for CR (99.0 %) and CIP (89.6 %) in simulated wastewater along with good repeatability. Fixed-bed column tests also confirmed its potential as an effective adsorbent for wastewater purification due to continuous adsorption properties towards CR and CIP over time. Finally, the interaction mechanisms for CR/CIP adsorption processes onto CL-800 were possibly determined via various advanced techniques. This study provides new perspectives for providing a potential low-cost efficient adsorbent for organic wastewater treatment.

Enhancing anaerobic digestion of actual papermaking wastewater with addition of Fenton sludge

The effect of Fenton sludge on anaerobic digestion of actual papermaking wastewater was investigated in this study. The results showed the iron in the Fenton sludge primarily exists in the form of needle-like iron oxide (FeOOH) and showed high electron transfer capability. Fenton sludge promoted electron transport in anaerobic digestion and electron transport system activity increased by 59 %. Fenton sludge enhanced the metabolic activity of anaerobic microorganisms, especially that of the hydrogenotrophic methanogens, the content of coenzyme F420 increased by 48.9 %. Besides, the microbial community structure in anaerobic digestion was affected by Fenton sludge, the quantity of microorganisms increased significantly. The dissimilatory iron-reducing bacteria (Desulfobacterota) and hydrogenotrophic methanogens (Methanobacterium and Methanolinea) were enriched, which promoted the methane production. As a result, the anaerobic digestion performance of papermaking wastewater was promoted significantly by adding Fenton sludge, the organic matter removal efficiency and methane production increased by 11.17 % and 15.12 %. This study provided an effective solution for the optimisation of anaerobic treatment of actual refractory organic wastewater.

Performance evaluation of a wet air oxidation reactor with external circulation for high-chemical oxygen demand wastewater treatment

The presence of high-concentration organic contaminants in wastewater poses considerable risks to the health of both humans and ecosystems. Wet air oxidation (WAO) is an attractive treatment option, but current dilution and retreatment processes do not align with economic and environmental principles. Here we report an external circulation wet oxidation treatment process that utilizes oxidizing liquids to reduce feed concentration. By coupling energy consumption model with computational fluid dynamics model, we explore the optimal parameters for an industrial external circulation reactor. A 90 kt/a external circulation wastewater treatment system has been established, achieving a 21.6% increase in chemical oxygen demand (COD) removal efficiency and a 34.8% reduction in energy consumption. These findings provide a promising pathway for the efficient, low-energy treatment of high-concentration organic wastewater while minimizing freshwater resource consumption.

Development and testing of alginate/C3N4porphyrin bead as a self-initiated Fenton photocatalyst for highly efficient atrazine removal

Fenton reaction has been widely used for efficient treatment of organic wastewater. However, its applications are limited by such key factors as pH < 3. In this study, we developed, tested, and optimized an alginate/C3N4porphyrin bead (C3N4por-SA) as a recyclable photocatalyst in a photocatalysis-self-Fenton process to overcome these limitations. Porphyrin-modified C3N4 (C3N4por) was used as the H2O2 donator, while Fe(III) nodes served as the Fenton reagent. The as-prepared floating alginate/C3N4por bead utilized the light source as a driving force for the catalysis. Under visible light irradiation for 6 h, the model pollutant atrazine was degraded by 70.96 % by the optimized photocatalyst (named as C3N4por-SA-Fe1Ca5), demonstrating better photocatalytic performance than alginate/C3N4 beads. This improvement was attributed to the higher H2O2 yield from C3N4por. The alginate/C3N4por bead showed better photocatalytic activity even after several consecutive cycles and could easily be recovered for reuse. Furthermore, Fe(III)/Ca(II) bimetallic alginate bead exhibited better photocatalytic activity and a higher content of •OH radicals than the Ca(II) monometallic alginate beads, due to the ability of Fe(III) nodes to serve as a Fenton reagent. The influences of light sources, and commonly existing matters (namely SO42−, Cl−, CO32−, NO3−, and humic acid) were investigated. Moreover, the alginate/C3N4por bead demonstrated good photocatalytic performance in a simulated natural environment without the addition of extra H2O2, with an atrazine removal percentage of up to 96.3 % after 3-h irradiation. These findings indicated the great potential of alginate/C3N4por bead in practical applications.

Green and sustainable degradation of ofloxacin in Fe3O4/clinoptilolite electro-Fenton system under neutral condition

BackgroundIn order to overcome the drawbacks of the pH value adjustment and Fe2+addition of traditional electro-Fenton in refractory organic wastewater treatment, we set up an electro-Fence system (FCC-EF) with multiple functions of adsorption, catalysis, and green regeneration for efficient and green degradation of ofloxacin (OFLO) wastewater under neutral condition. MethodsThe Fe3O4/clinoptilolite catalyst with adsorption function was prepared by hydrothermal synthesis method, and then characterized by energy dispersive spectrometer (EDS), transmission electron microscopy (TEM) and X-ray Diffractometer (XRD). The Fe3O4/clinoptilolite's chemical composition and oxidation state was investigated by X-ray photoelectron spectros (XPS). The degradation of OFLO and the total organic carbon (TOC) were determined through HPLC and a TOC analyzer, respectively. FindingsThe results indicate that in multi-cycle operation under current density of 6 mA·cm−2 and pH = 7, FCC-EF has a 100 % removal rate for OFLO and 80.4 ± 0.2 % removal rate for TOC at 165 min, while no iron ions are detected. The internal cycling of Fe3+/Fe2+ within Fe3O4 crystals is performed in FCC-EF. The green regeneration of Fe3O4/clinoptilolite and the efficient degradation of OFLO in multi-cycle operation could be simultaneously achieved under neutral condition.