Organic Wastewater Treatment Research Articles

Effective microwave regeneration of natural sepiolite and montmorillonite as adsorbents for tetracycline removal and mechanism insight

Natural clay minerals such as sepiolite (Sep) and montmorillonite (Mt) are used as low-cost adsorbents to remove tetracycline (TC) in water, and the spent adsorbents saturated with TC are regenerated under microwave (MW) irradiation. The adsorption and regeneration properties of Sep and Mt are compared. The possible adsorption and MW regeneration mechanisms are proposed. The results show that 11.25 mg·g−1 and 20.74 mg·g−1 adsorption capacities of Sep and Mt are obtained, respectively, within 120.0 min at 298 K. Mt has higher adsorption capacity, faster adsorption rate and shorter adsorption time for TC than that of Sep. The adsorption processes using Sep and Mt are well-fitted to pseudo-second-order kinetics and Langmuir models. The two adsorption reactions are spontaneous and endothermic, with increased randomness at solid–liquid interfaces. Moreover, 89.76 % and 114.45 % maximum regeneration ratios are obtained for Sep and Mt, respectively. Mt exhibits superior regeneration performance than Sep. After eight adsorption-regeneration cycles, the two adsorbents can maintain excellent adsorption and regeneration performance. This work provides new perspectives on the adsorption technology using natural clay minerals to remove antibiotics and the MW regeneration technology to regenerate spent natural clay minerals saturated with organic pollutants in organic wastewater treatment.

Multi-functional copper oxide nanoparticles synthesized using Lagerstroemia indica leaf extracts and their applications

Developing multifunctional nanomaterials through environmentally friendly and efficient approaches is a pivotal focus in nanotechnology. This study aimed to employ a biogenic method to synthesize multifunctional copper oxide nanoparticles (LI-CuO NPs) with diverse capabilities, including antibacterial, antioxidant, and seed priming properties, as well as photocatalytic organic dye degradation and wastewater treatment potentials using Lagerstroemia indica leaf extract. The synthesized LI-CuO NPs were extensively characterized using UV–vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform-infrared spectroscopy (FT-IR). The colloid displayed surface plasmon resonance peaks at 320 nm, characteristic of LI-CuO NPs. DLS analysis revealed an average particle size of 93.5 nm and a negative zeta potential of −20.3 mV. FTIR and XPS analyses demonstrated that LI-CuO NPs possessed abundant functional groups that acted as stabilizing agents. XRD analysis indicated pure crystalline and spherical LI-CuO NPs measuring 36 nm in size. Antibacterial tests exhibited significant differential activity of LI-CuO NPs against both gram-negative (Escherichia coli, Salmonella typhimurium) and gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. In antioxidant tests, the LI-CuO NPs demonstrated a remarkable radical scavenging activity of 97.6 % at a concentration of 400 μg mL−1. These nanoparticles were also found to enhance mustard seed germination at low concentrations. With a remarkable reusability, LI-CuO NPs exhibited excellent photocatalytic performance, with a degradation efficiency of 97.6 % at 150 μg/mL as well as a 95.6 % reduction in turbidity when applied to wastewater treatment. In conclusion, this study presents environmentally friendly method for the facile synthesis of LI-CuO NPs that could potentially offer promising applications in biomedicine, agriculture, and environmental remediation due to their multifunctional properties.

Simultaneous purification of salt and condensate by collaborated evaporation-peroxodisulfate treatment of high salinity organic wastewater

High salinity organic wastewater is commonly treated by evaporation, which produces a large amount of waste salts and condensed water containing organic compounds. The waste salts are typical classified as hazardous waste and the condensed water often requires advanced oxidation treatment before it can be biochemically treated. In this study, a synergistic treatment process combining evaporation with thermal activation of peroxodisulfate (PDS) was developed for the treatment of wastewater containing tetrabromobisphenol S (TBBPS) and Na2SO4 to reduce the content of organics in the crystal salt and condensed water. Compared with evaporation alone, the synergistic treatment process allows the complete removal of TBBPS from the crystal salt with an increase of TOC removal from 4.48 % to 94.44 %. Meanwhile, in the condensed water, TBBPS can also be completely removed with a decrease of the average TOC content from 25.56 mg/L to 4.97 mg/L. EPR detection reveals that the dominant reactive species are •OH, SO4-•, and 1O2. Moreover, the presence of SO42- can enhance the conversion of •OH to SO4-•, thereby improving the utilization of reactive species by increasing the contribution of SO4-•. The degradation intermediates of TBBPS were detected by IC and LC-MS, based on which the possible degradation mechanism of TBBPS was proposed. The synergistic treatment process can not only promote the resource utilization of waste salt and reduce the difficulty of condensed water treatment but also improve the stability of the evaporation system.

Microalgal-bacterial treatment of ice-cream wastewater to remove organic waste and harvest oil-rich biomass.

The diversity of microalgae and bacteria allows them to form beneficial consortia for efficient wastewater treatment and nutrient recovery. This study aimed to evaluate the feasibility of a new microalgal-bacterial combination in the treatment of ice cream wastewater for biomass harvest. The bacterium Novosphingobium sp. ICW1 was natively isolated from icecream wastewater and the microalga Vischeria sp. WL1 was a terrestrial oil-producing strain of Eustigmatophyceae. The ice cream wastewater was diluted 4 folds for co-cultivation, which was relatively less inhibitory for the growth of Vischeria sp. WL1. Four initial algal-bacterial combinations (v:v) of 150:0 (single algal cultivation), 150:1, 150:2, and 150:4 were assessed. During 24days of co-cultivation, algal pigmentation was dynamically changed, particularly at the algal-bacterial combination of 150:4. Algal growth (in terms of cell number) was slightly promoted during the late phase of co-cultivation at the combinations of 150:2 and 150:4, while in the former the cellular oil yield was obviously elevated. Treated by these algal-bacterial combinations, total carbon was reduced by 67.5 ~ 74.5% and chemical oxygen demand was reduced by 55.0 ~ 60.4%. Although single bacterial treatment was still effective for removing organic nutrients, the removal efficiency was obviously enhanced at the algal-bacterial combination of 150:4. In addition, the harvested oils contained 87.1 ~ 88.3% monounsaturated fatty acids. In general, this study enriches the biotechnological solutions for the sustainable treatment of organic matter-rich food wastewater.

Cellulose‐Based Aerogels with Photocatalytic Function for Solar Steam Generation

Solar steam generation is considered an efficient, renewable, and environmentally friendly technology for clean freshwater production, offering the potential to alleviate the growing global water scarcity issue. Herein, the commercial cellulose is used as raw material and water transport matrix, and silver phosphate particles are used as difunctional light‐absorbing matters and photocatalyst to prepare cellulose‐based composite material (silver‐plated cellulose aerogel [CAAg]). The resulting CAAg possesses superhydrophilicity, intrinsic network structure, high porosity (89.88%), and low thermal conductivity (0.091 W m−1 K−1). As a result, the CAAg exhibits an evaporation rate of nearly 1.55 kg m−2 h−1 in simulated seawater under a light intensity of 1 kW m−2. Furthermore, due to the excellent photocatalytic properties of silver phosphate particles, the CAAg can simultaneously achieve high degradation rates toward various dye molecules including methylene blue, rhodamine B, and methyl orange in water, making it show tremendous potential applications for clean freshwater production and organic wastewater treatment.

MgMnxOy-GAC particle electrode for effective peroxone oxidation: High salinity organic wastewater treatment with synergistic electrocatalytic ozonation

A three-dimensional electro-peroxone (3D-EP) system achieved efficient degradation of high salinity organic wastewater and showed significant implications for potential application. Herein, an MgMn-granule-activated carbon (GAC) particle electrode was developed through impregnation calcination and applied in multipollutant removal. The integration of electrolysis, ozone application, and MgMn-GAC in the 3D-EP system manifested strong synergy, leading to successful elimination of all phenol within 30 min due to ample hydroxyl radical production. The energy consumption of MgMn-GAC was 1.86 kWh·m−3 and the specific energy consumption was 0.033 kWh·g−1 COD, exhibiting high electrical energy utilization efficiency under low applied current and low O3 exposure conditions. After six consecutive reaction experiments, COD removal reached 95.6 %, demonstrating remarkable catalytic activity and cycling stability. The study findings indicate that this material could be used as a low-cost particle electrode for practical wastewater treatment.

Activation of calcium sulfite by bismuth cobalt-copper perovskite-manganese dioxide composite for efficient degradation of metronidazole

The highly efficient BiCo0.5Cu0.5O3-MnO2 catalyst was prepared using the hydrothermal method and utilized for the first time to activate sulfite for degrading metronidazole (MNZ) in this study. Physicochemical analysis of the BiCo0.5Cu0.5O3-MnO2 catalyst was performed using XRD, FTIR, BET, SEM, TEM, and XPS, confirming the successful synthesis of catalyst. BiCo0.5Cu0.5O3-MnO2 demonstrated a larger specific surface area, a more uniform pore structure, and prevented perovskite agglomeration. The catalyst effectively activated CaSO3, resulting in the degradation of 99.94 % of MNZ within 30 min, showing excellent catalytic performance. Quenching experiments and EPR tests indicated that SO•-4, SO•-5 and 1O2 were the main reactive species, with the oxygen vacancy on the catalyst surface playing a crucial role in accelerating the formation of reactive species and electron transfer. Moreover, the valence transformation of Co, Cu, and Mn was identified as the main contributor to the activation of CaSO3, demonstrating significant synergistic effects. Liquid chromatography-mass spectrometry detected eleven intermediates, revealing that the BiCo0.5Cu0.5O3-MnO2/CaSO3 system could convert MNZ into low-toxicity products through three potential degradation pathways. Density functional theory (DFT) calculations showed that higher Fukui indices of MNZ sites were more susceptible to free radical attack. The BiCo0.5Cu0.5O3-MnO2/CaSO3 system also exhibited excellent degradability to different natural water bodies and other pollutants. Furthermore, the catalyst displayed strong stability and outstanding catalytic performance after 5 cycles. This study presents a versatile strategy for developing highly efficient green catalysts, which could be utilized in organic wastewater treatment.

Enhanced visible light photo-Fenton catalysis by Fe-doping oligo-layer natural molybdenite with efficient carrier spatial-driven Fe3+/Fe2+ cycle.

Developing cost-effective and efficient photo-Fenton catalysts is crucial for advancing photo-Fenton technology. MoS2 is a representative transition metal disulfide with attractive photoresponsiveness, making it ideal for preparing composite photo-Fenton catalysts. In this study, natural molybdenite was innovatively utilized as a source of MoS2 (OM) to synthesize a low-cost and efficient Fe@MoS2 (OMF) composite photo-Fenton catalyst by comminution and adsorption, which was then applied to the remediation of antibiotic-contaminated water. The OMF composites exhibited significant catalytic activity, with a kinetic rate constant of 0.022 min-1, which was 3.1 times higher than that of the original OM (0.007 min-1), indicating a 3% increase. This was attributed to the synergistic effect of many photogenerated electrons and reversible Mo4+/Mo6+ redox pairs, which accelerated the regeneration of Fe2+. After three cyclic tests, the concentrations of dissolved Fe2+ and Mo2+ ions remained below 0.38 mg/L and 0.17 mg/L, respectively. This indicates the high reusability of the catalyst in cyclic experiments. Ultimately, the main active species, •OH and •O2 -, were generated during the photo-Fenton process, contributing significantly to TC degradation. This study may serve as a reference for the development and application of natural mineral composite photo-Fenton catalysts in the treatment of organic wastewater.

Enhancing membrane distillation efficiency in treating high salinity organic wastewater: A pressure-driven membrane electrochemical reactor approach

Fouling of membranes continues to be a prominent challenge in the membrane distillation (MD) treatment of high salinity organic wastewater (HSOW). Although membrane electrochemical reactor (MER) can effectively inhibit the membrane fouling of MD, the high cost of the proton exchange membrane (PEM) used in MER limits its widespread application. In this study, cost-effective pressure-driven membranes were employed as a substitute for PEM to establish pressure-driven membrane electrochemical reactors for HSOW pre-treatment. By using ultrafiltration membrane (UFM) and reverse osmosis membrane (ROM), UFMER and ROMER were developed, respectively. Due to the superior electrochemical performance of UFM, UFMER saved 43 % of energy compared to PEMER with the highest removal rate of organics (~85 %) in the simulated HSOW treatment. In practical applications, using UFMER significantly reduced the amount and size of complexes in the real nanofiltration concentrate (NC) of landfill leachate. This contributed to the superior specific flux maintenance (97 %) with a salt rejection (>99 %) and the highest recovered specific water flux (99.6 %) in MD cases. UFMER reduced ~27 % of energy compared to PEMER in MER pre-treatment, and saved the most energy (~39.6 %) in MD post-treatment. Hence, this strategy is potential for forthcoming applications, notably in lowering the membrane cost of MER and energy consumption of both MER and MD.

Persulfate activated by Cu46Zr44.5Al7.5Y2 metallic glasses for efficient treatment of high concentration organic wastewater

Metallic glasses (MGs) with unique structures and properties have attracted much attention in a variety of chemical reactions. However, the industrial treatment of dye wastewater with ultrahigh concentration still remains a daunting challenge. Herein, it has been reported that Cu46Zr44.5Al7.5Y2 MGs are designed and applied to enhance heterogeneous persulfate (PS) activation for acid orange II (AO II) degradation. The Cu-based MGs exhibit the excellent catalytic behavior and reusability, and the high degradation efficiency (98 %) for 400 mg L−1 AO II dye aqueous solution is achieved within 70 min under PS activation overcoming the ultrahigh concentration limitation. Additionally, the degradation efficiency can still maintain more than 98.4 % within 23 min after reused 10 times. The probable degradation pathway may be proposed based on the intermediate identifications during the whole reaction. The highly reactive species for sulfate radicals, hydroxyl radicals and superoxide radicals (·SO4−, ·OH and ·O2−) generated from the reaction between Cu-based nanocomposites and PS molecules can contribute to improving the catalytic performance. These findings will provide a reasonable and potential strategy to design a catalytic degradation system for ultrahigh concentration dye wastewater treatment.

A dual flow-through electrochemical system coupled electrocatalytic membrane electrode and heterogeneous electro-Fenton for organic wastewater treatment

In this work, a dual flow-through heterogeneous electrochemical system was proposed in which a porous Ti/SnO2-Sb membrane and graphite felt (GF) were used as anode and cathode, respectively. By combining of anodic oxidation (AO) and electro-Fenton (EF), this electrochemical system obtained a synergism effect on organic pollutants degradation resulted in a high removal efficiency. In addition，attributed to the application of dual flow-through mode, mass transfer was improved which is also beneficial for organic pollutants degradation. The results illustrated that this dual flow-through electrochemical system exhibited a brilliant treatment performance for BPA wastewater treatment. It can be observed that the dual flow-through electrochemical system owned a removal efficiency of 99.2 % under optimum condition (2.5 V voltage at pH=3 using 0.05 M Na2SO4 as electrolyte). The mechanism investigation results indicated that the good treatment performance was due to the ·OH generated from both EF and AO processes and O2-· produced through AO process. In addition, this dual flow-through electrochemical system also exhibited a good reusability and application. It reveals a potential for factual wastewater application.

Unveiling activation mechanism of persulfate by homologous hemp-derived biochar catalysts for enhanced tetracycline wastewater remediation

Advancements in biochar activating persulfate advanced oxidation processes (PS-AOP), have gained significant attention. However, the understanding of biochar-based catalysts in activating PS remains limited. Herein, biochar (BC) and N-doped biochar (NBC) were synthesized from hemp for activating PS to treat tetracycline (TC) wastewater and analyzed their mechanisms separately. Surprisingly, N-doped in biochar leads to a change in the activation mechanism of PS. The BC-PS system operates mainly through a radical pathway, advantageous for treating soil organic pollution (68%) with pH adaptability (less than 10% variation). Nevertheless, the NBC-PS system primarily employs an electron transfer non-radical pathway, demonstrating stability (only 7% performance degradation over four cycles) and enhanced resistance to anionic interference (less than 10% variation) in organic wastewater treatment. This study provides a technical reference and theoretical foundation for enhancing biochar activation of PS in the removal of organic pollutants from aquatic and terrestrial environments.

Constructing efficient Ti4O7/PbO2 heterostructured photoelectrode for water remediation

Photoelectrocatalytic oxidation (PEC) technology is considered to be an efficient process for the treatment of organic wastewater, and its performance depends on the characteristics of the PEC photoanodes. Therefore, the construction of heterogeneous nanostructured photoelectrodes based on suitable semiconductor materials for fast induced carrier transfer efficiency is essential for a high-performance PEC technique. Herein, titanium suboxide/lead (IV) oxide (Ti4O7/PbO2) ceramic photoelectrode with efficient PEC performance was synthesized by coupling PbO2 nanospheres with Ti4O7 through a hydrothermal method. To maximize the PEC performance of the ceramic electrodes, the Ti4O7/PbO2 nano-heterostructures were optimized by modulating the hydrothermal temperature. The optimized ceramic electrodes possessed a low Tafel slope, a low charge-transfer resistance and a good photocurrent response. Ti4O7/PbO2-110 exhibited an efficient PEC activity (approximately 92.21%) for the degradation of reactive brilliant blue KN-R. The efficient PEC performance of Ti4O7/PbO2-110 arose from the formation of a type II heterojunction between Ti4O7 and PbO2, which achieved efficient photogenerated carrier separation and facilitated the formation of intermediate active species. This work not only validates the efficient performance of Ti4O7/PbO2-110 for PEC water purification but also provides a reference strategy for the preparation of heterostructured ceramic photoelectrodes with a high PEC efficiency.

A novel graphene oxide electrode preparation and its performance in the treatment of saline organic wastewater

This study uses electrochemical technology to simultaneously remove salt and degrade organic pollutants to achieve green and efficient treatment of high-salt organic wastewater. In this study, graphene oxide (GO), which has excellent conductivity, chemical stability, and catalytic adsorption performance, was selected to prepare a composite electrode, aiming to explore its performance and evaluate its possibility of being used for the degradation of high-salt phenol wastewater treatment. The samples were characterized using SEM, FTIR, and other techniques. The electrochemical performance of the samples was analyzed using an electrochemical workstation, and their practical application performance was explored through simulated wastewater experiments. Experimental results confirmed that among the three electrodes prepared, the CFGE exhibited the lowest system energy consumption and the highest current efficiency, measuring 235.81 kWh/kgCOD and 12.66 % respectively. The HGE electrode is second only to it, with 269.39 kWh/kgCOD and 11.08 % respectively. The SCGE electrode has the worst performance, which is 344.83 kWh/kgCOD and 8.66 % respectively. The Yst of the three electrodes are 0.4083 mg/L∙min, 0.3817 mg/L∙min, and 0.29 mg/L∙min respectively. This study provides new research ideas and solutions for the efficient treatment of high-salt organic wastewater.

Enhancing the treatment efficiency of three-dimensional electro-Fenton system for organic wastewater: An analysis from the comprehensive perspective of H2O2 generation

For optimizing H2O2 generation in three-dimensional electro-Fenton (3D-EF) to enhance efficacy in treating organic wastewater, a comprehensive analysis from various perspectives of H2O2 generation was provided. By quantifying the generation of H2O2 within the reaction system and comparing it with the changing trends in organic wastewater treatment efficiency, a close correlation between H2O2 generation and organic wastewater treatment was revealed. A reliable and accurate kinetic model for H2O2 generation was formulated by building upon the reactions of H2O2 with electrodes and coexisting substances. The mathematical formulation of the kinetic model pinpointed pivotal factors influencing H2O2 generation, including current density, dissolved oxygen concentration, and the Fe catalytic activity substance. The experimental data and fitted results under various conditions indicated that the model could reasonably and accurately describe the relationship between pivotal factors and the quantity of generated H2O2. Crucial strategies were proposed to enhance H2O2 generation in the 3D-EF system by drawing from the impact rules of pivotal factors on H2O2 generation. These strategies primarily focused on improving electrode performance, optimizing reactor conditions, and refining particle electrode preparation processes.

Fine-Tune the Electronic Structure of Copper Nanowire Networks by Heteroatom Doping Toward Enhanced Fenton-like Reaction

To fine-tune the configuration of electrons around metal centers is critical to enhancing the activation of peroxymonosulfate (PMS) for organic decontamination in a manner similar to the Fenton-like reaction. Herein, we systematically explored the inclusion of different heteroatoms to manipulate the electronic configuration of copper nanowire (CuNW) networks toward PMS activation. Both experimental results and theoretical simulations unveiled that doping the CuNW with boron (B) to generate CuNW-B adjusted the d orbital of CuNW, optimized the electronic density of Cu active sites and endowed a proper adsorption energy of PMS, which provided the most active oxidation capacity of the materials studied. Conversely, doping with phosphorus (P) to generate CuNW-P caused evident performance decay in terms of the activation of PMS, as strong adsorption energy hindered the effective desorption of key intermediates. Accordingly, the CuNW-B boosts the Fenton-like reaction and is nearly triple and twice as effectively at degrading bisphenol A (92.5%) as CuNW-P (36.0%) and CuNW (50.5%). Thus, it was reasonably hypothesized that electronic reconstruction played an important role in improving the Fenton-like reaction. During this process, an applied potential (AP) facilitated the catalytic process by reducing Cu2+ to Cu+, which was followed by the formation of primary active species (Cu3+). Additionally, the use of a recirculating fluid flow in the reactor provided convective mass transfer, which led to more charge transfer to the structure of electrode relative to a conventional diffusion-limited batch reactor. Moreover, tests in a variety of challenging conditions demonstrated the robustness and stability of the combined CuNW-B/PMS/AP approach. This study provides an approach to finely control the electronic structure of Cu sites and is expected to guide the design of advanced Fenton-like catalysts, which could further provide a promising technology for the treatment of actual organic wastewater in a sustainable manner.

Construction of S scheme ZnO/g-C3N4 heterojunction for the removal of pyridine from coal chemical wastewater

In order to achieve the removal of nitrogen-containing heterocyclic compound pyridine in coal chemical wastewater. The S scheme ZnO/g-C3N4 heterojunction was constructed by evaporation solvent-high temperature thermal polymerization. The construction of the S scheme heterojunction effectively improved the photocatalytic activity. The S scheme heterojunction well retained the h+ with high oxidation activity of ZnO-VB and the e− with high reduction activity of g–C3N4–CB, achieving efficient separation of e−-h+. The complex band structure and potential difference lead to the bending of the band and the formation of the internal electric field, which effectively realizes the charge separation. ZnO/g-C3N4 heterojunction shows good activity and stability, and has great potential in the field of organic pollutant wastewater treatment. The construction of S scheme heterojunction also provides a new way to improve the activity of photocatalyst.

Photocatalytic bio‐inspired PDA‐RGO/g‐C3N4 nanocomposite incorporated PES membrane for removal of environmental antibiotic pollutants

AbstractBACKGROUNDMembrane technology makes it more suitable for the treatment of environmental polluted organic wastewater. Membrane fouling is one of the major concerns in commercial membranes. To overcome this issue, photocatalytic nanomaterials are embedded into the membrane to enhance its surface nature and reusability. In this investigation, polydopamine functionalized graphene oxide (PDA‐RGO), graphite carbon nitride (g‐C3N4) and PDA‐RGO/g‐C3N4 nanomaterials were incorporated within polyethersulfone membrane fabricated via a phase inversion technique. These as‐prepared membranes’ functional groups and surface morphologies were investigated by Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and field emission electron microscopy (FESEM). These as‐prepared membranes were investigated for photocatalytic activity under visible‐light‐driven photodegradation by environmental pollutants such as Rhodamine B (RhB) and Norfloxacin (NOR).RESULTSCompared with pristine PES membrane, the PDA‐RGO/g‐C3N4‐PES nanocomposite membrane showed higher photocatalytic activity for Rhodamine B 94.6% and Norfloxacin 96.8%, also reached greater water flux 189 L m−2 h−1. Therefore, the bio‐inspired nanocomposite‐modified PDA‐RGO/g‐C3N4 photocatalytic membrane could have huge potential in processing environmentally polluted water.CONCLUSIONSPDA‐RGO/g‐C3N4‐PES nanocomposite membrane improved the membrane hydrophilicity, water flow, anti‐fouling performance, rejection studies and photocatalytic degradation than the pristine membrane. The synergistic result of PDA‐RGO and g‐C3N4 exhibits better photodegradation efficiency of the membrane towards environmental pollutants. © 2024 Society of Chemical Industry (SCI).

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2−), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

A novel continuous-flow photocatalytic device for antibiotic degradation

The presence of antibiotic contaminants in water reservoirs and aquatic environments poses considerable risks to public and ecosystem health. Despite its high mineralization efficiency and environmental friendliness, photocatalytic technology has limited practical applications due to low energy efficiency, intermittent operation, and inconvenient catalyst recovery. Here, we developed a continuous-flow photocatalytic device (CFP-D) with outstanding activity, stability, and university towards antibiotic wastewater degradation. Complete removal of total organic carbon was achieved for multiple antibiotic wastewaters using CFP-D in a continuous flow process. The unique combination of continuous-flow reactor and highly photo-permeable F-Ti-SiO2 aerogel with abundant TiO5 active sites overcomes the limitations of conventional photocatalytic devices. This study provides new insights for the design of highly efficient monolithic catalysts and continuous flow reaction devices, and showcases the immense potential of CFP-D in medical and organic wastewater treatment.