TOC Removal Efficiency Research Articles

Integrated Advanced Ozonation Technologies for Enhanced Total Organic Carbon Removal from Secondary Treated Municipal Wastewater: Systematic Optimization and Environmental Analysis

Integrated Advanced Ozonation Technologies for Enhanced Total Organic Carbon Removal from Secondary Treated Municipal Wastewater: Systematic Optimization and Environmental Analysis carbon (AC) for TOC removal from secondary-treated effluent. A predictive model optimised the process parameters, achieving a maximum TOC removal efficiency of 65.95% at an O3 flow rate of 3.17 L/min, H2O2 dosage of 12.98 mM, UV exposure duration of 62.04 min, and AC dosage of 10.10 mg/L. In contrast, the lowest TOC removal of 39.55% ± 2.15% occurred under sub-optimal conditions, with an O3 flow rate of 3 L/min, H2O2 dosage of 10 mM, UV exposure for 20 min, and 1 mg/L of AC. The economic and environmental analyses revealed the integrated process to be more cost-effective and sustainable compared to conventional single-step treatments. These findings highlight the potential of integrated advanced ozonation technologies for effective TOC removal, providing a pathway for enhanced wastewater treatment practices and improved environmental sustainability. Graphical Abstract

Electrocatalytic Oxidation of Toxic Wastewater using Electrodes based on Transition d-metal Oxides

The process of electrooxidation of the active substances Paracetamol (PCT), benzoquinone (BQ) and hydroquinone (HQ) was studied using a set of different dimensionally stable anode (DSA) and Boron doped diamond (BDD) electrodes. Comparison of the efficiency of electrocatalytic anodes was assessed using percent total organic carbon (%TOC) removal and PCT amount removal values. The removal of %TOC in synthetically prepared waters for the BDD anode reached 96%, for DSA electrodes Ti/PbO2-IrO2-RuO2 57%, Ti/IrO2-RuO2-TiO2 35%, Ti/IrO2-RuO2-SnO2 31%, Ti/RuO2-SnO2 30% and Pt 24%. BDD effectively degrades PCT and almost completely mineralizes BQ and HQ. A DSA-Ti/PbO2-IrO2-RuO2 electrode and a BDD electrode were used in the electrooxidation process of real industrial wastewater containing PCT. The BDD electrode had a TOC removal efficiency of 58%, while the DSA-Ti/PbO2-IrO2-RuO2 electrode achieved 52%. Despite similar values ​​of PCT removal by both electrodes, the Ti/PbO2-IrO2-RuO2 anode showed low mineralization of organic matter. The originality of this paper lies in the study of the electrooxidation of real PCT wastewater and the use of a Ti/PbO2-IrO2-RuO2 electrode.Graphical

High-Efficiency Catalytic Ozonation Degradation of Ni Complex Wastewater Using Mn-N Codoped Active Carbon Catalyst.

With the rapid development of electroless nickel (Ni) plating industry, a large amount of Ni complex wastewater is inevitably produced, which is a serious threat to the ecological environment. Herein, a novel Mn-N codoped active carbon (Mn-N@AC) catalyst with high catalytic ozonation ability was synthesized by the impregnation precipitation method and was characterized by BET, XRD, Raman, SEM, FTIR, and TPR. Meanwhile, Mn-N@AC showed excellent catalytic ozonation ability, stability, and applicability. When Ni-EDTA (TOC = 400, Ni = 58.05 mg/L) was used as simulated wastewater, the removal efficiency of TOC and total Ni reached 97.8 and 92.7%, respectively, and after three cycles, the TOC removal efficiency was still up to 93.6%. When Ni-EDTA wastewater was replaced with Ni-citrate, Ni-tartaric, and Ni-malate, the TOC removal efficiency remained above 93%. In addition, mechanistic insights by quenching experiments and EPR verified the high removal efficiency of TOC mainly attributed to indirect oxidation of ·OH and ·O2-, and the potential mechanism was proposed. The work provides insights into the deep removal of Ni complex wastewater by catalytic ozonation with low cost and high efficiency.

The effectiveness of ozonation treatment in reducing ph, turbidity, bod, cod, and toc in pharmaceutical industrial wastewater

Abstract The pharmaceutical industry’s fabrication of pharmaceutical products releases byproducts that have the potential to negatively impact the environment. Indicators of contaminants include characteristics such as COD, BOD, TOC, pH, and turbidity that are within acceptable standards of excellence. The objective of this study was to look at fluctuations in the concentrations of pharmaceutical wastewater substances parameters before and following treatment with the ozonation method, as well as to assess the ozonation procedure’s performance on pharmaceutical wastewater contaminants parameters. The ozonation methods, which altered the O3 retention period, served as the independent variable in this study. The dependent variables applied were pH optimalization, and the removal efficiency of turbidity, BOD, COD, and TOC. Controlling variables involve the starting pollutant concentration, pressure and temperature levels, and equipment conditions. To determine the ideal time variation for the ozonation process, many variations will be evaluated. However, several parameters (e.g. pH, BOD, and TOC) were not reducing with the designed time variations. Nevertheless, this approach was effective in reducing turbidity levels by 48.5% and COD levels by 55.4% over 15 minutes.

In-situ thermally induced formation of an ultra-glossy hydrophilic surface for oil fouling prevention in TiO2@MXene membranes

Oil droplets are inevitably deposited on the surface of membranes, resulting in membrane contamination during oily sewage separation. To effectively prevent oil fouling, a TiO2@MXene membrane with an ultra-glossy hydrophilic surface was designed via in-situ thermal induction to regulate the membrane surface structure and properties. Through high temperature-induced evolving the Ti valence and the functional groups of Ti3C2Tx, uniform TiO2 nanoparticles were generated in-situ on the Ti3C2Tx surface while altering the surface structure and properties, which considerably improved the hydrophilicity, underwater oleophobic properties, and surface finish of the membrane. Specifically, the TiO2@MXene membrane (MT600) exhibited a low water contact angle of 7.5° and a high underwater oil contact angle of 133.3°. Notably, the oil adhesion force of the membrane was as low as 0.0013 μN, outperforming most oil water separation membranes. Thus, the unique structure and surface properties endowed MT600 membrane with excellent oil retention (TOC removal efficiency of > 95 %) and antipollution ability (permeance decay rates of < 10 %) for oil-in-water emulsion separation. This is because the ultra-glossy hydrophilic and oleophobic surface prompted the formation of a continuous and stable hydration layer on the membrane surface and prevented oil droplets from falling into the membrane grooves. Benefiting from the robust, ultra-glossy surface, the MT600 membrane exhibited excellent long-term durability and reusability (emulsion permeance recovery of > 90 %) in high-salt, highly acidic, and highly alkaline environments. This study opens pathways to realize ultra-glossy membrane surface for the efficient demulsification of small size emulsions and long-lasting, stable oil water separation.

Efficient Preparation of S-Scheme Ag/AgBr/BiOBr Heterojunction Photocatalysts and Implications for Degradation of Carbendazim: Mechanism, Pathway, and Toxicology.

Carbendazim (CBZ), as a highly effective benzimidazole fungicide, has a good control effect on various crops caused by fungi. However, excessive use of CBZ in water, atmosphere, soil, and crops has serious effects. The efficient degradation of CBZ is an effective way to reduce its toxic effect. In this work, the type of S-scheme Ag/AgBr/BiOBr heterojunction photocatalyst was effectively prepared by a simple one-step solvothermal in situ method and first applied to the mineralization and degradation of CBZ. The effects of the molar ratio of AgBr to BiOBr, catalyst dosage, CBZ concentration, pH value of the original solution, and inorganic salt ions on the photocatalytic degradation performance of CBZ were comprehensively studied. The results showed that, under visible light irradiation, 0.9-Ag/AgBr/BiOBr (0.9-AAB) exhibited the best photocatalytic degradation performance (88.9%) against the concentration at 10 mg/L of CBZ in original solutions with pH of 10. However, the degradation effect was also good at pH 7. After 90 min, the degradation efficiency reached 86.0%, corresponding to a TOC removal efficiency of 84.0%. The results indicate that the main active species are 1O2 and •O2- free radicals according to the free radical quenching experiments and electron spin resonance spectra. Combined with the XPS characterization results, the electron transfer mechanism of the S-scheme heterojunction was deeply revealed. Additionally, the degradation pathway of CBZ was proposed through both the intermediate identification and the theoretical calculation derived from the DFT Fukui index. Finally, the toxicity of CBZ and the degradation intermediates were predicted based on the T.E.S.T.

Iron coagulant regulating reactive species in ionizing radiation process for enhanced degradation of bisphenol A

In the treatment of industrial wastewater by electron beam technology, the flocculation process was frequently coupled with electron beam radiation to improve the water quality to meet the discharge standard. Iron-containing coagulant was widely used in the flocculation process. Therefore, this study investigated the impact of residual iron-containing coagulants on pollutant degradation by the ionizing radiation process. Results showed that the absorbed dose required for complete removal of 50 mg/L bisphenol A decreased from 5 kGy to 2.5 kGy in the presence of 100 μM typical iron coagulant (FeCl3). BPA degradation efficiency increased with the increase of FeCl3 dosage over a wide pH range (3.0–10.0), and the TOC removal efficiency increased from 20% to 45% with the addition of 300 μM Fe(III). The mechanistic investigation demonstrated that •OH was the primary reactive species responsible for BPA degradation. The residual iron coagulants (FeCl3) significantly enhanced the degradation and mineralization efficiency. Under suitable pH conditions (3.0–6.0), the reducing reactive species (eaq‒ and •H) could effectively reduce Fe(III) to Fe(II), which then reacted with H2O2, thus inducing in-situ Fenton reaction to generate more •OH, thus promoting the radiolysis degradation of micropollutants. This study explored the potential of using residual iron coagulants from the flocculation process to enhance the performance of electron beam technology for wastewater treatment.

Synergistic enhancement in hydrodynamic cavitation combined with peroxymonosulfate fenton-like process for bpa degradation: New insights into the role of cavitation bubbles in regulation reaction pathway

The combination of hydrodynamic cavitation (HC) and Fenton-like oxidation technology can dramatically enhance the pollutant removal capacity, however, the synergistic effect of cavitation and catalysts on reactive oxygen species (ROS) generation remained enigmatic. In this study, we established a combined system based on HC and Ce-MnFe2O4 activated peroxymonosulfate (PMS) for BPA removal, and attentions were paid on the role of cavitation bubbles. The results show that the combination of HC in Ce-MnFe2O4 activated PMS could mediate the degradation of BPA from the non-radical pathway dominated by 1O2 to •O2− dominated radical pathway. Both controlled experiments and theoretical calculations revealed that the cavitation bubbles with different sizes play the dominant role in ROS generation. The microjets produced by the collapse of cavitation bubbles could create a large number of oxygen vacancy defects on Ce-MnFe2O4 surface, which modify the activation barrier of PMS and facilitate the generation of •O2− thermodynamically. The stable existing cavitation bubbles with the size of 100∼400 nm could create considerable gas-liquid interface. The molecular dynamics simulations show that the nano bubbles can concentrate the BPA and increase the probability of contacts between BPA and Ce-MnFe2O4, hence effectively solve the issues of short lifetime of •O2− radicals and limited mass transfer distance to strengthen the reaction. In addition, the PMS/Ce-MnFe2O4/HC system not only achieves the satisfied COD (95 %) and TOC (65 %) removal efficiency but also enabled the BPA-contaminated water with a low energy cost of 0.065 kWh·m−3 and oxidant cost, highlighting the application potential of the HC technology for contaminated water.

Sustainable approach for landfill leachate treatment through dielectric barrier discharge/ferrate (DBD/Fe(VI)) enhanced nanofiltration

Landfill leachate, with its high concentrations of persistent organic pollutants, salts, heavy metals, and emerging contaminants, presents significant environmental challenges. This study investigated the combination of dielectric barrier discharge (DBD) and ferrate (Fe(VI)) pretreatment technology in landfill leachate treatment, focusing on its effectiveness in enhancing oxidation performance and mitigating membrane fouling. The results indicated that after DBD/Fe(VI) treatment, TOC and UV254 removal efficiencies increased by 44 % and 67 %, respectively. Additionally, the DBD/Fe(VI) system excelled in removing fluorescent substances and high molecular weight organic compounds, thereby reducing the formation of the cake layer on the nanofiltration membrane. This system enhanced oxidation performance through the synergistic production of reactive intermediates, with Fe(V)/Fe(IV) and •OH being the main active species, O2•-, and 1O2 also contributing significantly. The degradation pathway of perfluorooctanoic acid was investigated by utilizing it as the representative pollutant. Compared to the raw landfill leachate system, the DBD/Fe(VI) increased membrane flux by 104 %, while reducing reversible and irreversible fouling resistances by 67 % and 75 %, respectively. Furthermore, the advantages and practical application potential of the DBD/Fe(VI) system were evaluated from energy consumption, economic cost, and carbon dioxide emissions. The study offers an innovative method for landfill leachate treatment and fouling mitigation.

Assembly of artificial photo-enzyme coupling nanoreactor for boosting photodegradation of trace bisphenol A pollutant in water

It is a difficult issue to remove the trace persistent organic phenolic pollutants in water. Herein, a new artificial horseradish peroxidase (HRP)/hierarchical carbon nitride (HCN) photo-enzyme coupling nanoreactor is assembled by immobilizing HRP on HCN, which achieves the high-efficiency degradation performance for trace bisphenol A (BPA) in water. Besides the promoted charge separation efficiency as well as visible light harvest capacity, the hollow and abundant pores structure of HCN/HRP can provide a confinement effect and molecular diffusion channels to promote photo-enzyme synergic catalytic effect, thus boosting degradation reaction of BPA. Compared with original HCN, the optimal HCN/HRP-3 sample obtain a higher degradation rate of 0.0575 min−1, which is 3.60 and 125 times as large as that over original HCN (0.016 min−1) and HRP (0.00046 min−1), respectively. Meanwhile, the mineralization ability of the HCN/HRP photo-enzyme coupling nanoreactor is enhanced dramatically owing to the far higher TOC removal efficiency of BPA with 81.05 % within 60 min than original HCN (37.63 %). The photocatalytic reaction mechanism investigations demonstrate that h+, •O2− and •OH all take part in the degradation process of BPA and the importance order of h+ > •O2− > •OH. This work provides an innovative design philosophy for the assembly of photo-enzyme synergic catalytic system to effectively remove the organic pollutants in water.

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.

Electrocoagulation process for phosphate recovery of agricultural wastewater: effect of calcium adding, voltage, and time.

Recovery of valuable resources, such as phosphate recovery from wastewater, can help close the nutrient cycle and is interesting to investigate. This study aims to evaluate phosphate recovery and set aside TOC, OC, and IC in agricultural wastewater using electrocoagulation with a helix electrode configuration. This study employed the Response Surface Methodology (RSM) for statistical analysis and modeling, utilizing a central composite design (CCD). Variation of calcium concentration (2-7mg/L), voltage (15-45V), and electrocoagulation time (5-15min) was applied in an electrocoagulation reactor with a helix-shaped stainless steel cathode and a solid cylindrical Mg anode. Based on RSM analysis, electrocoagulation with a helical electrode configuration significantly affects phosphate recovery and the removal of TOC, OC, and IC when treating agricultural wastewater. Under operating conditions of 15V, 15min time, and 2mg/L calcium concentration, we achieved the lowest phosphate concentration of 0.003mg/L (99.74% reduction). The highest TOC allowance is > 100% of the initial concentration, the TC allowance is 55.79%, and the IC allowance is 30.91%. The formation of metal hydroxides affects the efficiency of TOC removal in the electrocoagulation process, and higher electrolysis times lead to higher TOC removal efficiency. Higher voltages also improve the coagulation and flotation processes in the reactor. Calcium concentration plays a role in enhancing the flocculation process and binding phosphonates from wastewater.

Photo Fenton-like oxidation of real textile wastewater: Operating conditions, kinetic modelling and cost analysis

The reusability of the pretreated textile wastewater was improved by using bismuth ferrite/activated carbon hybrid photocatalysts in photo-Fenton-like oxidation process. BiFeO3/WAC (WAC: walnut shell based activated carbon) and BiFeO3/CAC (CAC: Commercial activated carbon) catalysts were synthesized and used for the photocatalytic oxidation of in-situ pretreated textile wastewater. The influences of the mixing speed, oxidant dosage, light source, catalyst loading, and temperature were studied. The highest TOC removal efficiencies were evaluated as 56.3% and 76.2% in the presence of BiFeO3/WAC and BiFeO3/CAC, respectively. A kinetic study was performed to derive the kinetic models expressing the TOC removal as a basis for the semi-pilot and industrial scale studies. The kinetic data fit to a two-step second order reaction rate model in the presence of both of the catalysts. The activation energies of the first and the second steps were calculated as 36.0 and 16.0 kJ/mol, respectively, on BiFeO3/WAC catalyst while 43.4 and 13.3 kJ/mol of activation energies were calculated on BiFeO3/CAC.

Efficient and stability electrochemical degradation of Bisphenol A on Ti/TiO2-NTA/PbO2-Nd anode: Mechanistic analysis

The Ti/TiO2-NTA/PbO2-Nd electrodes were fabricated using anodic oxidation and electrodeposition techniques for the electrocatalytic treatment of bisphenol A (BPA) pollutants in coking wastewater. Characterization revealed well-organized TiO2 nanotube arrays (TiO2-NTA) with a hollow structure, featuring a wall thickness of 36 nm and an inner diameter of approximately 83 nm. The TiO2-NTA interlayer restricted PbO2 growth, leading to a compact crystal structure and increased electrode surface area. Electrochemical tests showed that the Ti/TiO2-NTA/PbO2-Nd electrode outperformed Ti/TiO2-NTA/PbO2 and Ti/PbO2 electrodes, exhibiting the highest oxygen evolution potential, lowest charge transfer resistance, optimal hydroxyl radical generation, and longest service lifetime. The removal efficiencies for BPA were 95.4 % for Ti/TiO2-NTA/PbO2-Nd, 90.8 % for Ti/TiO2-NTA/PbO2, and 80.6 % for Ti/PbO2. The Ti/TiO2-NTA/PbO2-Nd electrode also achieved the lowest energy consumption at 0.157 kWh/(g·COD), a 40 % reduction compared to Ti/PbO2. The introduction of TiO2-NTA enhanced electrode stability, electron transfer, and surface area, while neodymium (Nd) doping improved oxygen evolution potential and hydroxyl radical production. Under optimized conditions, the Ti/TiO2-NTA/PbO2-Nd electrode achieved BPA removal efficiencies of 99.24 %, COD removal efficiencies of 82.77 %, and TOC removal efficiencies of 78.92 %. UV–Vis spectrophotometry, three-dimensional excitation-emission matrix fluorescence spectra (3D EEM), and gas chromatography–mass spectrometry (GC–MS) analyses revealed potential BPA degradation pathways.

Electro-activated periodate for organic contaminants degradation: Insights into the pH-dependent mechanism of active species

Although electro-activated periodate (PI) has demonstrated significant efficiency in degrading emerging contaminants (ECs), there has been limited research investigating the pH-dependence of active species generation and pollutant degradation. A graphite felt-based electrochemical system (GF-PI) was chosen to deeply explored. It exhibited significant differences in contaminants removal under different pH conditions. Notably, an interesting result is found that the GF-PI system at pH=3 exhibited exceptional removal performance specifically for phenolic contaminants, such as bisphenol A (BPA) and acetaminophen (ACT), whereas it displayed poor efficiency for other compounds, including sulfamethoxazole (SMX), carbamazepine (CBZ), benzoic acid (BA), and atrazine (ATZ). However, there is no selectivity for contaminants removal in pH=4, 7, and 9 system. The experiment of probe capture and quenching are conducted to thoroughly investigate the variety of reactive oxygen species (ROSs) generated. It has been proven that hypoiodous acid (HOI) is the main active species in the system with pH=3. In addition, the system with pH=4 exhibits the highest degradation efficiency and TOC removal efficiency, despite the low yield of hydroxyl radical (·OH), indicating that the iodate radical (IO3·) plays a pivotal role. Under neutral and alkaline conditions, ·OH, IO3·, and singlet oxygen (1O2) are the main active species. Moreover, the system exhibits remarkable stability, anti-interference capabilities, and cost-effectiveness, indicating the superiority for treatment of authentic wastewater. Additionally, the degradation intermediates and biotoxicity of SMX are evaluated through multiple measures. A comprehensive understanding of pH is indispensable in electro-activated PI system for treatment of emerging organic contaminants.

Enhanced degradation of sulfathiazole by ionizing radiation activated persulfate and periodate: Performances and mechanisms

Ionizing radiation has attracted significant interests in water purifying. However, it suffers from poor mineralization performance during the decontamination of organic micropollutants such as antibiotics. Herein, the radiolytic degradation of sulfathiazole (STZ) by gamma radiation was investigated. STZ could be completely degraded at 2.0 kGy absorbed dose but TOC removal efficiency was only 22.62 %. Quenching experiments demonstrated that •OH was the main reactive species. Toxicity assessment and phytotoxicity experiments indicated that gamma radiation can comprehensively decrease the toxicity of STZ. Significant enhancements of degradation and mineralization were observed in gamma/persulfate (Gamma/PS) and gamma/periodate (Gamma/PI) processes. The rate constant (k) increased by 1.08 times and TOC removal efficiency increased by 2.01 times with PS addition (1 mM). The k value enhanced by 4.05 times and TOC removal ratio enhanced by 2.66 times with the presence of PI (1 mM). Mechanistic investigation indicated that 1O2 played a major role in STZ degradation in the Gamma/PS and Gamma/PI systems. PI was almost completely transferred into the nontoxic iodate (IO3-), and no toxic reactive iodine species were produced in the Gamma/PI process. Moreover, Gamma/PS and Gamma/PI systems showed a broad-spectrum ability to remove a series of antibiotics. The removal performances and the costs of these systems were competitive compared with other advanced oxidation processes for antibiotics elimination. This study supplied an efficient and sustainable choice for the degradation of antibiotics, and clarified the intrinsic reaction mechanisms in the ionizing radiation-activated PS and PI systems.

Synthesis of ZnV2O6 nanosheet photocatalysts for efficient photodegradation of Rhodamine B: Experimental and RSM modeling

A ZnV2O6 photocatalyst with nano-sheet morphology was synthesized using a facile solvothermal approach. To optimize the photo-decomposition of Rhodamine B (RhB), a new surface response methodology (RSM) based on the Central Composite Design (CCD) approach was employed. Several structural/microstructural and spectroscopic characterization techniques were utilized to describe the physical and chemical characteristics of ZnV2O6 (ZVO) nanosheet such as XRD, Raman, SEM-TEM, DRS, PL/TRF. The optimal conditions for RhB photo-decomposition were mathematically discussed as a function of four variables such as pollutant dose, pH values, photocatalyst-weight, and irradiation time, which were modeled by CCD-RSM employing a quadratic statistical model and an optimization approach (ANOVA analysis). RhB degradation efficiency of 97 % was achieved for the optimal conditions of pH = 8, photocatalyst mass = 95 mg, RhB concentration = 9 ppm, and irradiation time = 120. The registered reaction constant was 0.029 min−1. The removal efficiencies of TOC and COD when using the ZVO photo-catalyst for the RhB degradation were 83 % and 88 % respectively. The re-usability of ZnV2O6 samples has been assessed in 4 consecutive series revealing a high stability of the material after extended periods of photo-catalytic reaction. Furthermore, the active radical species involved in the breakdown of RhB were further confirmed through quenching tests in which hydroxyls and holes were found to be the major species contributing to the decomposition of RhB.

Catalytic ozonation promoted by Mn-doped sludge-based catalyst treating refractory industrial wastewater

Attributed to the refractory characteristic of industrial wastewater, it usually needs advanced treatment. Moreover, massive hazardous activated waste sludge generated from wastewater treatment introduces additional ecological risks. In this study, sludge-based catalysts were prepared by doping Mn to treat typical refractory wastewater of petrochemical secondary wastewater. Results showed that the Mn-doped catalyst (PS-M700) prepared by pyrolysis at 700 °C was optimal for the catalytic ozonation of petrochemical secondary wastewater. The optimal ozone and catalyst dosage were 216 mg/L and 1.0 g/L, respectively. Catalytic ozonation of petrochemical secondary wastewater using PS-M700 showed an excellent TOC removal efficiency of 56.6 %. In addition, hydroxyl radicals (OH) played a major role in the catalytic ozonation of the petrochemical secondary wastewater. Results of excitation-emission matrix fluorescence spectroscopy showed that catalytic ozonation can further enhance the removal efficiency of not readily biodegradable compounds compared to ozone alone. Moreover, the catalytic ozonation process mainly targeted substances within the molecular weight (MW) < 1 kDa range in petrochemical secondary wastewater. In addition, transformation processes occurred between pollutants of different MW. Fourier Transform ion cyclotron resonance mass spectrometry showed that oxygen (CHO), nitrogen (CHONO) and sulfur (CHOS) containing contaminants were decreased by 6.0 % (2359 vs 2216), 34.9 % (2505 vs 1631) and 62.8 % (1227 vs 456). The present study shows the satisfactory prospect of a sustainable “wastes-treating-wastes” process for wastewater treatment.

Combination of TiCl3 reduction/coagulation and ceramic membrane filtration for heavy metal complex removal

Ni-EDTA is a common heavy metal complex found in electroplating wastewater. As heavy metal complexes are stable and highly toxic, it is essential to develop efficient strategies to remove. In this work, TiCl3 coagulation and ceramic microfiltration membrane were combined in the removal of Ni-EDTA. Based on the results, this combinative process exhibited a high Ni-EDTA removal efficiency. When compared to employing the TiCl3 coagulation process only, the combinative process improved Ni2+ and TOC removal efficiencies from 91 % to 97 % and from 60 % to 93 %, respectively. Furthermore, it was found that the in-situ formed titanium hydrolysates possessed good adsorption for EDTA and Ni-EDTA, with maximum capacities reaching 713 mg/g and 213 mg/g, respectively, which also enabled the cake layer a considerable secondary removal for TOC. Mechanistic investigations confirmed that the reducibility of Ti3+ contributed to both Ni-EDTA and EDTA removal. In the presence of Ti3+, Ni-EDTA was decomplexed and the released Ni2+ was reduced to Ni0 synchronously. Meanwhile, some dissociated EDTA would combine with oxidized Ti4+ to form Ti-EDTA and ultimately promote the formation of TiO2 crystals. The formation of the insoluble chelate Ti-EDTA and the adsorption by surface hydroxyl of TiO2 were the key reasons for the efficient removal for released EDTA. This work provides a new approach for the decomplexation and harmless separation of heavy metal complexes.

Enhancing pollutant removal and desalination in microbial desalination cells using a rotating algal biofilm cathode

Currently, most photosynthetic microbial desalination cells (PMDCs) employ suspended algae as cathode organisms to produce oxygen. However, this method requires expensive platinum as a catalyst to catalyze the binding of oxygen to cathode electrons. In this study, a PMDC using a rotating algal biofilm (RAB) as a biocathode was demonstrated. RAB not only generates enough oxygen as an electron acceptor but also enhances the combination of oxygen and electrons on the cathode. Furthermore, the RAB-MDC system exhibited excellent performance in pollutant removal and desalination. When using simulated wastewater as anolyte and catholyte, the RAB-MDC achieved impressive removal efficiencies for COD, TOC, and NH4+-N, reaching 91.0 ± 0.1 %, 74.7 ± 0.03 %, and 95.0 ± 0.05 %, respectively. The power density reached 89.5 mW/m3 at an external resistance of 1000 Ω, while the desalination efficiency was 36.0 %, with a desalination rate of 190.9 mg/d. Additionally, high-throughput 16S rDNA sequencing was employed to assess the relative abundance of microorganisms in the RAB-MDC device, facilitating guided culture in subsequent studies. In conclusion, this research demonstrates the potential of RAB as a biocathode in MDCs for comprehensive wastewater treatment, desalination, power generation, and nutrient recovery.