Industrial Wastewater Research Articles

Z-type heterojunction construction and photocatalytic performance of O-C3N4/Bi2Mo2O9 composites for the effective degradation of tetracycline

The antibiotic tetracycline (TCH) is a common pollutant seen in industrial wastewaters and municipal wastewaters, which poses an environmental problem. To solve this, oxygen modified carbon nitride (O-C3N4) and a Z-type heterojunction O-C3N4/Bi2Mo2O9 with excellent photocatalytic performance was constructed. The degradation efficiency of O-C3N4/Bi2Mo2O9-60 % for TCH (10 mg/L) was as high as 89.9 % under 3 h of illumination. The corresponding degradation rate was 1.9 and 3.1 times higher than that of O-C3N4 and Bi2Mo2O9, respectively, due to the effective carrier separation and the increased specific surface area. The Z-type heterojunction construction of the O-C3N4/Bi2Mo2O9-60 % composite and corresponding TCH degradation mechanism were further assessed through exploring the electron transfer, active radical and reaction paths. Furthermore, the O-C3N4/Bi2Mo2O9-60 % composite exhibited a high cyclic stability, and its degradation efficiency remained at 87.5 % after 5 cycles. The O-C3N4/Bi2Mo2O9-60 % composite also had excellent adaptability to the actual aqueous environment, and the degradation efficiency for TCH in different actual aqueous environments remained above 70 %. All results indicated that O-C3N4/Bi2Mo2O9 composites have significant visible photocatalytic performance and can be used for the practical removal of TCH pollutants.

Mechanistic insight into the simultaneous removal of Cr(VI) and phosphate by a novel versatile bimetallic material

Industrial wastewater containing hexavalent chromium Cr(VI) and phosphate poses a great threat to human health and the aquatic ecological environment. In this study, a novel La(OH)3- and CaO2-fabricated CNT (La-Ca-CNT) material was developed for the simultaneous and highly effective removal of aqueous Cr(VI) and phosphate. Characterization results showed that synergistic effects existed between the CNT support and La and Ca species. La-Ca-CNT showed high phosphate and Cr(VI) removal rates in acidic conditions with high stability. Kinetic study suggested that the fast adsorption of phosphate on La-Ca-CNT was controlled by intraparticle diffusion. The removal of Cr(VI) and phosphate interacted with each other, and the removal of Cr(VI) went through a slow-fast-slow reaction, reaching a Cr(VI) removal rate of over 97% within 180min. La-Ca-CNT had a high phosphate adsorption capacity (174.3mg/g), and over 70% of the adsorbed phosphate could be recovered. The presence of co-existing anions showed negative effects on phosphate adsorption but negligible effects on Cr(VI) reduction, while organic carbon in natural water showed no effect on phosphate and Cr(VI) removal. A mechanistic study revealed that phosphate was removed by physical-chemical adsorption (outer-sphere complexation and ligand exchange) over La-Ca-CNT, while Cr(VI) was reduced by H2O2 generated from CaO2 or directly by surface CaO2.

Two novel 3D polyoxometalate-based metal–organic frameworks for structure-directed selective adsorption and photodegradation of organic dyes

Degradation of organic dyes from industrial wastewater is crucial for human health and ecological balance. Synergy adsorption and photodegradation is one of the effective methods to degrade organic dyes at present. The former is usually limited by the challenge of its the recovery and the poor adsorption capacity of the adsorbent, whereas the latter frequently suffers from sluggish reaction kinetics. Herein, the introduction of the unique electron-rich Keggin polyoxometalates (CuW12 and SiW12) into electron-deficient metal photosensitive viologen framework to construct two polyoxometalate(POM)-based metal organic frameworks (POMOFs) of 3D porous layered structures, namely [Cu2(ipbp)2(H2O)2][CuW12O40]·3H2O (1) and [Co2(H2ipbp)3(H2O)2(CoO6)2][SiW12O40]·H2O (2); (H2ipbp·Cl = 1-(3,5-dicarboxyphenyl)-4,4′-bipyridinium), which enable selective adsorption of methylene blue (MB) and effectively photocatalytic degradation cationic dyes. In addition, POMs and metal-organic frameworks act in synergy to result in much improved adsorption of certain cationic dyes as well as enhanced photocatalytic activity that allow the catalyst to show better excellent reusability and stability. The adsorption degradation rate of MB and rhodamine B (RhB) of 2 is faster than that of 1 because of the lower Zeta potential of 2 suggesting that there are electrostatic interactions in the adsorption process. This work adopted a novel view to comprehening the technology.

A comparison of biofilm and suspension methods in removing heavy metals (chromium) from industrial wastewater with Scenedesmus obliquus and Chlorella vulgaris

The study investigated the factors influencing chromium absorption by the microalgae species S. obliquus and C. vulgaris using an ANOVA approach. The analysis revealed significant independent effects of contact time, temperature, pH, density, algal species, and production methods, as well as notable interactions among these factors. Under standardized conditions of pH 7, 105 minutes of contact time, a temperature of 25°C, light intensity of 3500 lux, and a density of 60, S. obliquus showed the highest chromium absorption. The biofilm production method was consistently more effective than the suspension method for both species. At a pH of 5, C. vulgaris outperformed S. obliquus, achieving maximum absorption rates in both production methods. The study also found that higher temperatures facilitated increased chromium absorption, peaking at 27.5°C for suspension and 26.5°C for biofilm methods, with S. obliquus demonstrating superiority. Significant interactions resulted in the combination of the biofilm method and S. obliquus yielding the best absorption rates at specified conditions. Density trends indicated decreasing absorption rates for both microalgae at densities of 30 and 40, but S. obliquus later exhibited a reversal of this trend, unlike C. vulgaris. Contact time results indicated increased absorption from 60 to 115 minutes, but a decline afterwards, with S. obliquus again leading. The optimal conditions for chromium absorption were identified as pH 5, temperatures around 26–28°C, with particular density levels, highlighting the importance of production method in enhancing absorption rates for both microalgae species.

Engineering cellulose aerogel composites for mercury ion sequestration and aquatic real time monitoring based on the immobilization of metal-organic frameworks.

Industrial wastewater effluents containing elevated levels of mercury are a significant menace to both the ecosystem and human health. Despite the advent of metal-organic frameworks (MOFs) as promising adsorbents, their application in treatment of industrial wastewater has been impeded by the challenges associated with handling their powdered form. In this work, we introduce a straightforward method for fabricating MOF composite cellulose aerogels (5MM-101@CA). The resulting adsorbent showed a high adsorption capacity of 409.84 mg/g for Hg (II), with over 75 % removal efficiency maintained after five consecutive adsorption-desorption cycles. Furthermore, the material exhibited high sensitivity for the real-time detection of Hg (II), with a detection limit as low as 6.89×10-8 M. The adsorbent also showed remarkable fluorescence stability for up to a week, indicative of its excellent optical performance. Dynamic adsorption demonstrated the adsorbent's ability to sustain continuous and stable system operation without compromising adsorption efficiency. These findings underscore the effectiveness of post-synthetic modification (PSM) technology in enhancing the performance of MOFs, while highlighting the utility of low-cost cellulose as an effective carrier. Thus, the composite material developed in this work is promising as it not only maximizes the adsorption capabilities of MOFs but also circumvents the risk of secondary pollution.

A novel neutralization process for improving dehydration performance of industrial by-product gypsum

By-product gypsum, produced through the traditional neutralization precipitation method for treating industrial acidic wastewater, is difficult to recycle due to its high moisture content. In this study, we proposed a novel neutralization process i.e. the two-stage neutralization method. By-product gypsum was used as an alkaline neutralizer and recycled as seed crystals for the first time. The original by-product gypsum has the poor dehydration performance due to its small particle size and the presence of colloids on its surface. After adding the by-product gypsum to the acidic wastewater, the ratio of CaO/SO3 in the system descended and colloids were dissociated. On the one hand, the alkaline component of the incomplete reaction continues to play a neutralizing role. On the other hand, CaSO4·2H2O particles act as seed crystals, promoting rapid growth of new crystals along their surface, which effectively improved crystallization performance and dehydration performance of the neutralization slag (outward discharge of slag). Compared with the original method, the wet weight of the neutralization slag is decreased from 186.0 g/L to 88.8 g/L, and the water cut is declined from 64.5% to 34.1%. The utilization ratio of the carbide slag augmented from 63.0% to 99.47%.

The trends of per-and polyfluoroalkyl substances (pfas) in drinking water systems in Maryland United States

Per- and polyfluoroalkyl substances (PFAS) have become a major concern in water quality management because of their persistence in the environment and associated health risks. In Maryland, the diverse water resources and densely populated areas, faces unique challenges culminating from PFAS contamination. This research paper presents a comprehensive overview of PFAS contamination trends in Maryland's drinking water systems across four distinct phases, spanning from 2019 to 2022, it highlights the trends of PFAS contamination, environmental and public health risks, and strategies for effective management. Utilizing data from extensive monitoring efforts conducted in the state, the study reveals a persistent and evolving environmental health challenge characterized by the dominance of different PFAS compounds, particularly PFOS and PFOA, found at concerning concentrations. Mean concentrations of total PFOA/PFOS across the sampling periods were at 18.78 ng/L, 7.28 ng/L, 14.60 ng/L, 12.46 ng/L, significantly surpassing the EPA's 2024 maximum contaminant levels of 4 ng/L for PFOA and PFOS. Despite fluctuations observed across sampling phases, PFAS levels consistently surpass EPA health advisory levels, indicating widespread contamination. Potential sources, such as industrial sites and wastewater treatment plants, underscore the need for robust regulatory enforcement and innovative remediation strategies to safeguard public health. The findings emphasize the necessity for continuous monitoring and multi-faceted mitigation approaches to address PFAS contamination effectively, ensuring the safety of Maryland's water resources and the health of its residents.

PE/PP fibrous adsorbents with bifunctional groups of tertiary amine and phosphate prepared by electron beam induced co-grafting for heavy metal adsorption of both cationic and anionic forms in acidic conditions.

A novel fabric adsorbent having bifunctional groups of tertiary amine and phosphate was prepared by co-graft polymerization of 2-diethylaminoethyl methacrylate (NMA) and 2-hydroxyethyl methacrylate phosphate (PMA) onto a polyethylene/polypropylene nonwoven fabric (PE/PP NF) under low-energy electron beam acceleration. The process involved pre-irradiating the fabric and immersing it in the comonomer solution for grafting. The kinetics of radiation-induced graft polymerization at a total dose of 100 kGy was investigated. For pre-irradiation at 100 kGy, the optimum condition offering highest degree of grafting was at 12 wt% of NMA, 8 wt% of PMA and 4 h of reaction time. The adsorption of anions using hydrogen chromate (HCrO4−) or Cr(VI) and cations using lead (Pb(II)), cadmium (Cd(II)) and copper (Cu(II)) in aqueous solution was carried out. The results demonstrated that the bifunctional adsorbent was able to adsorb both heavy metal anionic and cationic ions from water. The co-grafted adsorbents with tertiary amine and phosphate were able to adsorb 85% Cr(VI) anion and 29% Pb(II) cations from mixed Cr(VI) and Pb(II) solution at pH 3.0 and 71% Pb(II), 13% Cd(II) and 31 % Cu(II) from mixed Pb(II), Cd(II) and Cu(II) solution at pH 5.0. The unique achievement of this study is its hypothesis that a bifunctional adsorbent can be prepared from radiation-induced graft polymerization of two different monomers onto NF, along with proof that the prepared bifunctional adsorbent can actually absorb both cationic or anionic heavy metals forms. Additionally, the adsorbent's preparation offers a rapid and straightforward one-step grafting technique. Therefore, the new bifunctional adsorbents can remove heavy metal ions in aqueous solution, either in the cation or anion form, thus offering highly promising applications in industrial wastewater treatment.

Enhanced Biofilter and Ultrafiltration for Clean Water from the Soy Sauce, Bread, and Sticker Peeling Industries Wastewater

Enhanced Biofilter and Ultrafiltration for Clean Water from the Soy Sauce, Bread, and Sticker Peeling Industries Wastewater

Rapid and efficient removal of organophosphorus pollutant and recovery of valuable elements: A boosted strategy for eliminating organophosphorus from wastewater

Considering the significant hazards of organophosphorus compounds (OPs) and the potential crisis of phosphorus (P) resource shortage, there is a great necessity to develop economically feasible, highly effective, and sustainable strategies to remove OPs and recover P resources. In this study, low-cost microscale zero-valent iron (mZVI) was used to activate hydrogen peroxide for the rapid and efficient elimination of Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) from the aquatic environment. Compared to the conventional Fenton reaction and commercial mZVI, mZVI/H2O2-based Fenton-like reaction exhibited superior removal performance for THPS. The removal mechanism of the mZVI/H2O2 system for THPS was thoroughly elucidated through the identification of reactive oxygen species, characterization analysis, and theoretical calculation. Furthermore, the valuable components of the degradation products were successfully recovered through thermally induced precipitation of the sample followed by high-temperature calcination. The mZVI/H2O2 system has demonstrated significant advantages in removing organic compounds from various types of actual wastewater and improving the biodegradability of the wastewater. This study presented an environmentally friendly and highly efficient strategy to eliminate OPs pollution and recover P resources. It also provided an easy-to-operate method for remediating actual industrial wastewater.

Nanocomposite membrane for simultaneous removal of dye and heavy metal ions from wastewater.

A catalytic 2D nanocomposite membrane (CNC) was fabricated and used for the simultaneous removal of methylene blue (MB) and heavy metal ions in aqueous solution. Both molybdenum disulfide (MoS2) and graphene oxide (GO) were incorporated in a chitosan polymer matrix, and the fabricated CNC membrane exhibited performance as a nanofiltration membrane. Here MoS2 activated H2O2 to generate very reactive oxygen species (ROS), such as hydroxyl radicals, allowing the catalytic breakdown of the organic dye contaminants and reducing heavy metal ions. Greater than 99% efficiencies were achieved for the simultaneous removal of methylene blue (MB) and the heavy metal Co2+. Moreover, significant removal efficiencies in the 89-96% range were demonstrated for other heavy metal ions of Cu2+, Pb2+, and Ni2+. The generated ROS were trapped by terephthalic acid (TA) and confirmed by fluorescence emission spectroscopy. The used membrane was regenerated and reused with a flux recovery rate of more than 91% after 4 experimental cycles. These promising results indicated that the novel catalytic 2D nanocomposite membrane showed a high potential for the simultaneous removal of organic contraminants and heavy metal ions from textile industry wastewater.

Development of a liquid crystal-based sensor utilizing EDTA-cyclodextrin polymer for real-time optical detection of methylene blue in natural water samples

The discharge of dyes in industrial wastewater poses significant environmental and health risks when released into natural water resources. In this study, we report the development of an EDTA-crosslinked cyclodextrin polymer (ECDP)-based sensor for the real-time, naked-eye detection of hazardous methylene blue (MB) dye in aqueous solutions and natural water samples. The sensor functions via a competitive host–guest inclusion mechanism involving sodium dodecyl sulphate (SDS) and ECDP, which modulates the alignment of liquid crystals (LCs). Initially, SDS induces homeotropic ordering at the fluid interface, but when complexed with ECDP, it causes a tilted LC alignment. Upon the introduction of MB, SDS is displaced from the ECDP cavity and re-adsorbs at the LC/aqueous interface, triggering an orientational transition from tilted to homeotropic. This transition is clearly observed as a distinct bright-to-dark shift under crossed polarizers. The host–guest (ECDP/MB) inclusion complexation mechanism was further confirmed by FT-IR, XRPD, and DSC analyses. The developed sensor exhibits high selectivity for MB in dye-contaminated natural water samples and sensitivity to MB concentrations upto 0.10 mM. This study demonstrates the potential of cyclodextrin-based polymers for liquid crystal sensing applications, offering promising pathways for future developments in environmental monitoring.

Microalgae-Assisted Treatment of Wastewater Originating from Varied Sources, Particularly in the Context of Heavy Metals and Antibiotic-Resistant Bacteria

The increasing prevalence of heavy metals and antibiotic-resistant bacteria in wastewater (WW) raises serious environmental and public health concerns. This study investigates the efficiency of the microalgal strain Chlorella vulgaris EV-465 in treating wastewater and evaluates the antibiotic resistance profile of bacterial strains obtained from WW samples. Chlorella vulgaris EV-465 was used to treat four types of wastewater—domestic, municipal, hospital, and industrial wastewater—through 21 days of incubation. The findings demonstrated pH stabilization and significant decreases in nutrients (total nitrogen—TN, total phosphorus—TP), biological oxygen demand (BOD), chemical oxygen demand (COD), heavy metal (HM) concentrations, and bacterial count. Copper (Cu) showed the highest reduction, decreasing by 80% in industrial wastewater within 14 days, while lead (Pb) proved more resistant to removal, with only a 50% decrease by day 21. Additionally, the algae decreased bacterial counts, lowering colony-forming units (Log CFU/mL) from 9.04 to 4.65 in municipal wastewater over the 21-day period. Antibiotic susceptibility tests for isolated bacterial strains revealed high levels of resistance, with seven out of nine bacterial strains exhibiting multidrug resistance. Notably, Enterococcus faecium (PBI08), Acinetobacter baumannii (YBH19), and Pseudomonas aeruginosa (NBH16) displayed resistance to all nine antibiotics tested. Among the tested antibiotics, Ciprofloxacin showed the highest efficacy, with 66% susceptibility of tested bacterial strains. Cluster and phylogenetic analyses showed that the majority of the isolated bacterial strains belonged to the genera Pseudomonas and Escherichia, highlighting their genetic diversity and varied resistance mechanisms.

Synergistic effect of rice husk-derived activated carbon modified by Ni/Al-layered double hydroxides for lead removal from industrial wastewater

Synergistic effect of rice husk-derived activated carbon modified by Ni/Al-layered double hydroxides for lead removal from industrial wastewater

A Comprehensive Review of Advanced Treatment Technologies for the Enhanced Reuse of Produced Water

Produced water (PW) is considered to be the largest source of industrial wastewater associated with oil and gas extraction operations for industrial production. It is a mixture of organic and inorganic compounds that has high complexity in terms of various characteristics. Globally, the volume of PW is increasing along with the expansion of gas and oil fields, leading to major impacts on the environment. Existing treatment technologies involve partially treating the PW through removing the suspended solids, heavy metals, without removing organic components and re-injecting the water underground using water disposal injection wells. The treatment process consists of a primary treatment unit to remove the particles, followed a secondary biological or chemical processing treatment, while the final treatment stage involves the use of a tertiary treatment unit to improve the water quality and remove the remainder of the undesired components. Moreover, while PW is considered one of the available options to be utilized as a water source, no alternate advanced treatment options on a commercial scale are available at present due to the limitations of existing PW treatment technologies, associated with their maintainability, sustainability, cost, and level of quality improvement. As such, research focused on finding an optimal treatment approach to improve the overall process continues to be conducted, with the aim of reusing the water instead of injecting it underground. This literature review discusses the latest advanced technologies for PW treatment aimed at reusing the full stream capacity of PW and eliminating the need for wastewater disposal via injection. It is concluded that researchers should focus on hybrid treatment technologies in order to remove the pollutants from PW, effectively allowing for its reuse.

Upcycling of Beer Industry Wastewater: Biosurfactant Production and Application in Brewery Effluent Treatment

ABSTRACTThe beer processing industry generates large amounts of effluents rich in organic and inorganic material, and complex and expensive systems are commonly used for their treatment. Therefore, new alternatives capable of ensuring sustainable industrial growth through cost‐effective solutions are being studied. In this context, biosurfactants stand out due to their ability to degrade and remove contaminants from the environment. Therefore, the objective of this study was to evaluate the potential treatment of effluents from the beer industry using biosurfactants produced from wastewater from the beer industry. The biosurfactants were obtained by submerged cultivation at 30°C for 48 h using the bacterium Corynebacterium aquaticum in a mineral medium added of carbon source. The characterization of the biosurfactants was performed in relation to surface tension, emulsifying activity (EA), pH, and ionic character. The analyses were performed at 0, 24, and 48 h. The efficiency of the effluent treatments was evaluated by characterization in duplicate, before, during and after the treatment, regarding the concentrations of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total solids (TS). The best biosurfactant results were obtained using C. aquaticum in a medium with 10% (v/v) of brewing industry wastewater (BIW) as a carbon source after 48 h of cultivation, reaching a surface tension of 35.1 ± 0.2 mN/m, EA of 40.9 ± 0.5%, and stability under extreme conditions of temperature (−20°C to 121°C), salt (1% to 10%), and pH (4 to 10). Thus, the biosurfactant was applied for 10 days in an aerated biological treatment system. Best results were observed in biosurfactant concentrations of 0.5 CMD (critical micellar dilution), reaching improvement of up to 55.9% for BOD, 23.8% for COD, and 50.6% for TS. Thus, the biosurfactant produced (10% BIW) shows potential as an accelerator in the brewing industry effluent (BIE) treatment process, without purification and sterilization of the biocompound. Therefore, brewery wastewater proved to be a sustainable and nutritional substrate to obtain biosurfactants.

Enhanced industrial wastewater monitoring: method development for non-target screening of highly polar substances using ZIC-HILIC-HRMS.

Non-target screening (NTS) plays a major role in the monitoring and management of water bodies. While the NTS of moderate to non-polar substances is well-established, the screening of highly polar chemicals remains challenging. In this study, a robust separation method for highly polar substances using zwitterionic hydrophilic interaction liquid chromatography coupled with high-resolution mass spectrometry (ZIC-HILIC-HRMS) was developed. This method was specifically designed for the NTS of industrial wastewater, with the objective of capturing a wide range of polar contaminants in each acquisition run. Method validation included assessing key parameters such as repeatability, reproducibility, linearity, and limit of detection (LOD). For repeatability and reproducibility, the average %RSD of intensity and retention time across all substances in different matrices-solvent, influent, and effluent-remained below 6% and 1%, respectively (n = 10). The method demonstrated good linearity (R2 > 0.99) for 75% of the substances, while LODs varied between 0.1 and 40µg/L depending on the compound tested. The method was then applied for NTS analysis of untreated wastewater at various locations within a chemical industrial park. Additionally, the overall influent and effluent of an industrial wastewater treatment plant (WWTP) were monitored over a 10-day period. Principal component analysis (PCA) was performed to interpret the data, identifying irregularities in the wastewater content. Moreover, the method demonstrated the WWTP's ability to achieve an average removal efficiency of approximately 90% for this category of substances in this period, while also detecting their degradation products in the effluent. Finally, the method was successfully integrated into the daily monitoring routine of the WWTP, ensuring continuous surveillance and improved management of wastewater treatment processes.

Pre-treatment of composite industrial wastewater by Fenton and electro-Fenton oxidation processes.

The present study aims to characterize three industrial wastewater samples collected from petrochemical, food and beet sugar industries to determine the pollution potential and select the appropriate pre-treatment approach. According to the biodegradability profile of the multi-sourced mixed (composite) sample, the advanced oxidation process (AOPs) namely, Fenton (F) and Electro-Fenton (EF) were adopted as pre-treatment techniques and the operating parameters such as time, type of electrodes, pH, voltage, iron and H2O2 concentrations were critically examined. Analysis of Variance (ANOVA) was conducted to compare the performance efficiency of F& EF AOPs for treating the composite samples and the total operating costs for both approaches were assessed. The results revealed that, the initial values of the composite sample were 7.11, 19.2, 32.6, 19.3, 937, 1512, 860, 3.9, 2110 and 2.34 for pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), Salinity, BOD, COD, Oil and grease (O&G), Total Phosphorous (TP), Total Suspended Solids (TSS) and Total Kjeldahl Nitrogen (TKN), respectively. In addition, EF process achieved more removal efficiency for COD, O&G, BOD, TSS, and TKN (84.3%, 69%, 85%, 72% and 71.27%) compared to Fenton which displayed 78.43%, 66%, 69%, 70.1%, and 61%, respectively. Moreover, there are statistically significant differences (p < 0.05) between the initial and final (pretreated) values of the composite industrial wastewater for the addressed parameters and EF was significantly (p < 0.05) more effective than F process. The total operating costs were 3.117 and 2.063$ for F and EF, respectively, which confirmed that EF is more efficient and cost effective than F process. It was concluded that electro-Fenton process is favorable, eco-friendly and cost-effective option for pretreating real complicated multi-sourced industrial wastewater. The present study demonstrated a new avenue for achieving efficient management of industrial wastewater generated from similar industries.

Synthesis and investigation of optical properties and enhancement photocatalytic activity of TiO2-SnO2 semiconductor for degradation of organic compounds.

Industrial wastewater treatment using UV irradiation in combination with oxidants or catalysts (TiO2) has attracted attention as a promising substitute for conventional methods. Studying the preparation and characterization of TiO2-SnO2 nanocomposites with different ratios, as well as their use in the enhanced photocatalytic degradation of acid red 37 dye in aqueous solution under UV irradiation as a model pollutant, are the goals of the research. The crystalline structures of the prepared nanomaterials were confirmed by XRD and the surface morphology of the samples was studied by TEM. The elemental compositions of the catalysts were confirmed by EDAX. The optical properties of the powder samples were analyzed with UV-Vis spectroscopy and their band gaps were estimated. The photocatalytic degradation was investigated using several advanced oxidation techniques using a batch photoreactor. The TiO2-SnO2 (90:10) nanocomposite showed the best degradation efficiency.

Engineering Charge Transfer Characteristics in ZnO NRs/Ag2O NPs p-n Heterojunctions: Toward Highly Efficient and Recyclable Photocatalysts.

Staggered gap p-n heterojunction ZnO nanorods/Ag2O nanoparticles, a paradigm of photocatalysts, were developed via engineering the hydrothermal and coprecipitation method. Under simulated sunlight, the photocatalytic characteristics of ZnO/Ag2O(Zn/A) heterojunctions with varying mole ratios (from 8:1 to 8:4, named Zn/A-1-Zn/A-4) were systematically evaluated through the degradation of methylene blue (MB). The influence of key experimental variables, including photocatalyst concentration, MB concentration, and solution pH, on the photocatalyst performance was further analyzed. The incorporation of Ag2O enhanced visible-light absorption, improved electron-hole separation efficiency, and significantly improved the photocatalytic recyclability of the Zn/A heterojunctions. Additionally, metallic Ag generated during photodegradation was found to enhance the photocatalytic activity further. Kinetic studies indicated that the photocatalytic degradation of MB followed pseudo-first-order kinetics, with the Zn/A-3 heterojunction showing the highest photocatalytic activity, achieving a degradation rate constant (k) of 0.028 min-1. Scavenger experiments confirmed that •OH radicals, holes (h+), and superoxide radicals (•O2-) were the primary reactive species involved in the degradation process. The photocatalytic mechanism was identified as a Z-scheme charge transfer system, facilitating efficient charge separation. Moreover, the Zn/A-3 heterojunction exhibited remarkable recyclability, retaining >91% of the photocatalytic activity after five cycles. This study demonstrates the potential of Zn/A heterojunctions for practical applications in industrial wastewater treatment using solar energy.