Search Results (187)

The present work investigates the efficacy of ultrasound (US)-based pretreatment methods for the process intensification of biological oxidation (BO) of real pharmaceutical industrial effluent with a high initial COD of 50,000 mgL⁻¹. US, combined with advanced oxidation processes (AOPs), was used to degrade recalcitrant compounds. Conventional BO could only reduce the COD by 3.85% and confirmed the requirement of pretreatment. US, under established optimised conditions of 120 W power, 70% duty cycle, pH 6, and 30 °C temperature, gave a COD reduction of 5.77%. Combining US with oxidants like O₃ (2 L/ min), H₂O₂ (1000 mgL⁻¹), Fenton (1:5 Fe²⁺:H₂O₂), and peroxone (2 L min⁻¹ O₃ with 1000 mgL⁻¹ H₂O₂) as pretreatment gave COD reductions of 30.77%, 17.31%, 19.23%, and 42.31%, respectively. Toxicity assays using the agar well diffusion method revealed that the pretreatment techniques reduced the toxicity of the effluent and did not introduce any toxic secondary metabolites into the system. The optimised treatment time for BO was fixed at 30 h, and the COD reduction obtained for the streams pretreated with US, US + O₃, US + H₂O₂, US + Fenton, and US + peroxone were 14.3%, 88.46%, 57.69%, 61.54%, and 94.23%, respectively. The US combined with peroxone method was the best pretreatment for the effluent in terms of overall COD reduction. This work effectively demonstrates the usefulness of US-based methods to intensify the biological oxidation of real industrial effluent with high organic load. Full article

This study systematically investigates the catalytic degradation performance and reaction mechanism of Fe₈₀P₁₃C₇ Metal Glass (MG) in a Fenton-like system for the removal of Methylene Blue (MB). Kinetic experiments on degradation reveal that under acidic conditions (pH = 3), Fe₈₀P₁₃C₇ MG exhibits exceptional catalytic activity, achieving complete degradation of a 50 mg/L MB solution within 12 min. Its degradation rate significantly surpasses that of Fe₇₈Si₉B₁₃ MG and commercially available ZVI powder. Key parameters such as catalyst dosage, H₂O₂ concentration, solution pH, and initial dye concentration were systematically examined to determine the optimal reaction conditions. The characterization results indicate that Fe₈₀P₁₃C₇ MG maintains high activity even after multiple cycles of use, attributed to surface selective corrosion and crack formation during the reaction process. This “self-renewal” mechanism continuously exposes fresh active sites. Mechanistic studies confirm that the degradation process is driven by an efficient redox cycle between Fe²⁺/Fe³⁺ within the material, ensuring sustained and stable generation of •OH, which ultimately leads to the complete mineralization of MB molecules. This research provides solid experimental and theoretical foundations for the application of Fe₈₀P₁₃C₇ MG in dye wastewater treatment. Full article

Sulfanilic acid (SA) is a representative sulfonated aromatic amine commonly found in industrial effluents, posing significant risks to both human health and the ecosystem. Efficient and cost-effective treatment of SA-containing wastewater is crucial for sustainable environmental management. This study investigates the performance of the photo-Fenton process in degrading SA-containing wastewater. Three process variables are selected to study their effects on percent total organic carbon (%TOC) removal and final pH (pH_Final): initial total organic carbon concentration (TOC₀) (150–250 mg/L), Fe²⁺ concentration (15–85 mg/L), and H₂O₂ concentration (1000–1500 mg/L). A combination of response surface methodology (RSM) and Box-Behnken design (BBD) is applied to examine both the individual and interactive effects of these variables. A total of 15 experimental trials are conducted, with the center point repeated three times. The results indicate significant interaction effects between Fe²⁺ and H₂O₂ concentrations on %TOC removal, while the interaction between TOC₀ and H₂O₂ concentration notably influences pH_Final. The optimal operating parameters to maximize %TOC removal within 45 min of operation are determined as a TOC₀ of 54.2 mg/L, an Fe²⁺ catalyst concentration of 33.7 mg/L, and an H₂O₂ concentration of 1403 mg/L. Under these conditions, the predicted %TOC removal and pH_Final were 89.2% and 2.93, respectively, which confirmed through validation experiments. Additionally, a correlation between pH_Final, TOC₀, and final TOC concentration (TOC_Final) is observed, leading to the development of a linear model capable of predicting TOC_Final based on TOC₀ and ${\mathrm{p}\mathrm{H}}_{\mathrm{F}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l}}$ within the experimental space. The latter finding facilitates online monitoring of the process progress. Full article

Water pollution caused by synthetic dyes is a major environmental concern due to their stability, toxicity, and resistance to conventional wastewater treatments. This study presents a sustainable approach for synthesizing zinc oxide (ZnO) nanoparticles using artichoke biomass (waste) as a green precursor and enhancing their visible light photocatalytic activity through phosphorus doping. ZnO nanoparticles were successfully synthesized via a simple green route and doped with 3–6% phosphorus using NH₄H₂PO₄. The structural, morphological, and optical properties of the resulting P-ZnO were characterized by XRD, SEM/EDX, TEM, FTIR, and UV-Vis spectroscopy. (6 wt%) Phosphorus doping effectively reduced the band gap from 3.06 eV to 2.95 eV, extended light absorption into the visible range, and improved electron–hole separation, resulting in enhanced photocatalytic performance. The P-ZnO nanoparticles were evaluated for methylene blue (MB) degradation under visible light in a photo-Fenton-like process, with H₂O₂ as an oxidant. The degradation efficiency reached 87.05% with 6% P-ZnO and further increased to 92.35% upon addition of H₂O₂. Durability and reusability tests demonstrated that the 6% P-ZnO catalyst maintained its activity and structural integrity over four consecutive cycles, indicating negligible loss of efficiency and excellent resistance to surface poisoning. The photocatalytic activity was strongly impacted by the quantity of catalyst, solution pH, and initial dye levels, with optimal performance at 0.3 g/L catalyst loading, pH 3, and lower MB concentrations. Full article

To address the limitations of traditional photo-Fenton reactions in antibiotic wastewater treatment, this study designed a continuous flat-plate photo-Fenton reactor based on the Fe₃O₄/TiO₂@Al₂SiO₅ fiberboard photocatalyst and applied it to the degradation of tetracycline HCl (TCH). The supported catalyst Fe₃O₄/TiO₂@Al₂SiO₅ was prepared via a calcination method, using the Al₂SiO₅ fiberboard as the carrier. This not only effectively addresses the issue of catalyst recovery but also enhances the dispersion and stability of the Fe₃O₄/TiO₂ catalyst as a support. Moreover, the catalyst mainly exhibited an amorphous structure. TiO₂ and Fe₃O₄ were successfully loaded onto the surface of the carrier. The operating parameters of the reactor were systematically optimized, and the optimal conditions were determined as follows: TCH influent concentration of 50 mg/L, hydraulic retention time (HRT) of 120 min, initial pH of 4.5, H₂O₂ dosage of 10 mmol/L, and ultraviolet (UV) light intensity of 2.36 kW/m³. Under these conditions, the TCH removal efficiency could reach over 90%. Active species trapping experiments indicated that hydroxyl radicals (•OH) were the main active substances responsible for TCH degradation. With the assistance of HPLC-MS/MS and GC-MS analyses, 19 types of degradation intermediates were identified. It was proposed that the TCH degradation pathway mainly included •OH-mediated hydroxylation addition reactions and demethylation reactions initiated by •OH and h⁺. The toxicity assessment showed that the toxicity of the degradation intermediates gradually decreased with the progress of the reaction. This reactor features high efficiency, stability, and easy operation, providing a feasible solution for the large-scale treatment of antibiotic wastewater. Full article

We studied the impact of some magnetic nanoparticles on two wastewater models of Rhodamine B dye, with 5 µM and 10 µM concentrations. The magnetite nanoparticles, synthesized by the co-precipitation technique, having less than 20 nm diameter and typical crystallinity features, were used to treat the Rhodamine B solutions and the results were analyzed using spectral measurements. The biological efficacy of the photo-Fenton-like reactions underlying this wastewater treatment was assessed using the V79-4 fibroblast cell line of Chinese hamster. The MTT test (colorimetric method with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) was applied for the toxicity testing of Rhodamine B 10 µM and 5 µM, initially, and degraded with 8 g/L MNP and 10 mM hydrogen peroxide for 120 min of UV exposure, the cell viability decreasing to 57–59% and 69–74%, respectively, for the dose of 80 µL/mL. Morphological changes were identified by microscopy analysis, such as membrane disruption, cell content extravasation, apoptotic bodies, and also colored spherical inclusions suggesting non-metabolized dye solution aliquots. The simpler molecules consisting of Rhodamine B degradation products, i.e., benzoic acid, benzyloxyamine, and phthalic acid were analyzed for their theoretical reactivity through quantum chemical computational modeling, which revealed a significant chemical potential compared to Rhodamine B. Full article

The heterogeneous Fenton-like catalysts TiO₂/Fe₃O₄ were fabricated using maize straw as template (MST-TiO₂/Fe₃O₄) by calcination followed by the hydrothermal method. The characterization showed that higher Fe₃O₄ particle dispersion, closer interaction between TiO₂ and Fe₃O₄, stronger electron transfer ability, and lower leaching of Fe ions of MST-TiO₂/Fe₃O₄ catalyst resulted in higher catalytic activity towards the degradation of tetracycline (TC) compared to pure Fe₃O₄. The best conditions for TC degradation were initial pH = 6.74, 11.52 mmol/L of H₂O₂, 0.38 g/L of MST-TiO₂/Fe₃O₄, and a reaction time of 56.63 min according to the response surface methodology (RSM) result based on the Box–Behnken design (BBD). The quadratic model was well-fitted to the experimental data with R2 (0.9843) and adj-R2 (0.9660) by the analysis of variance (ANOVA). Under the optimum reaction conditions, a maximum removal rate of 98.67% was achieved. The findings of the present study revealed that heterogeneous UV–Fenton process catalyzed by MST-TiO₂/Fe₃O₄ was a suitable way for the degradation of TC from aqueous environment. Full article

Textile dyeing effluents are characterized by recalcitrant organics and high salinity, requiring robust pretreatments prior to biological polishing. The heterogeneous Fenton-type (HFT) oxidation over Prussian Blue nanoparticles supported on γ-alumina (PBNP/γ-Al₂O₃) was investigated in a liquid batch-recycle packed-bed reactor treating a synthetic textile wastewater (STW) reproducing an industrial dye bath with the Reactive Black 5 (RB5) dye, together with simplified RB5 and RB5 + NaCl matrices. Hydrogen peroxide decay followed pseudo-first-order kinetics. Using fixed initial doses (11, 20, 35 mmol L⁻¹), the catalyst exhibited an early adaptation phase and then reproducible operation: from the fourth reuse onward, both the H₂O₂ decomposition rate constant and DOC removal varied by <10% under identical conditions. Among matrices, STW exhibited the highest oxidant efficiency. With an initial H₂O₂ dose of 11 mmol L⁻¹, the treatment enabled complete discoloration and produced effluents with negligible toxicity. Increasing the initial dose to 20 or 35 mmol L⁻¹ did not improve treatment and led to a decrease in the hydrogen peroxide decomposition rate with reuses and loss of PB ν(C≡N) Raman bands, indicating surface transformation. Overall, PBNP/γ-Al₂O₃ demonstrated reproducible activity and structural resilience in saline, dyeing-relevant matrices at H₂O₂ doses that preserve catalytic integrity, confirming its feasibility as a stable and reusable pretreatment catalyst for saline dyeing effluents, and supporting its integration into hybrid AOP–biological treatment schemes for dyeing wastewater. Full article

Gasoline alkali residue raw liquid, a kind of highly toxicity containing organic waste generated during petroleum refining, is characterized by its complex composition, high pollutant levels, and significant emission volume. The effective treatment of this wastewater remains a considerable challenge in environmental engineering. This study systematically investigates the degradation efficiency and mechanism of Fenton oxidation in reducing the chemical oxygen demand (COD) of raw gasoline alkali residue sourced from Kashi. The effects of H₂O₂ concentration and the H₂O₂/Fe²⁺ molar ratio on COD and TOC removal were examined. Results demonstrated that the COD and TOC removal efficiency exhibited an initial decrease followed by an increase with rising concentrations of Fe²⁺ and H₂O₂. Comparative assessment of different combined Fenton processes revealed distinct mechanistic differences among the composite oxidation systems. The integration of pretreatment with UV-Fenton oxidation was identified as the optimal strategy. Under optimal conditions (pH = 3.0, H₂O₂ concentration = 1.0 mol/L, H₂O₂/Fe²⁺ molar ratio = 5:0.10), the COD was reduced from 25,041 mg/L to 543 mg/L, achieving a COD removal rate of 97.8%. This study elucidates the reaction mechanism of the Fenton system in treating alkali residue and provides a theoretical foundation for the advanced treatment of high-concentration organic wastewater. Full article

The confectionery industry produces effluents with diverse and complex compositions and high organic loads, which are typically not treated by conventional treatment plants. In this context, the Fenton process presents itself as an advanced chemical treatment alternative due to its ease of application, cost-effectiveness, and ability to improve the degradability of challenging effluents. This study addressed the question: How can Fenton’s reagent be applied as a pretreatment to reduce the organic load in real effluents from the food industry? The research evaluated this chemical pretreatment for effluents from a starch-based gummy candy production process, aiming to reduce the organic load and aid subsequent conventional treatments. Parameters such as COD, total dissolved solids (TDS), temperature, pH, electrical conductivity, dissolved oxygen, and degrees Brix (°Bx) were monitored before and after 2 and 4 h of pretreatment. The results showed that Fenton pretreatment reduced COD by more than 31%, with efficiency influenced by effluent composition and concentration. This removal can reduce discharge rates and operating costs, providing an economic advantage. The process proved to be a promising pretreatment option, contributing to the initial removal of pollutants and improving the performance of wastewater treatment systems, thus supporting sustainable industrial practices. Full article

Heterocyclic compounds in high-salinity wastewater are highly resistant to degradation, posing significant treatment challenges. A hybrid micro-nano bubble Fenton system (FT-MNBs) was developed to enhance Fe²⁺ activation via interfacial effects. The FT-MNBs achieved a significantly higher indole degradation rate (0.0380 min⁻¹) compared with micro and nano bubbles (MNBs) alone (0.0046 min⁻¹) and conventional Fenton (0.01008 min⁻¹). In real coking wastewater with a total dissolved solid (TDS) content of 3.266 g/L, FT-MNBs achieved COD removal efficiencies of 93.42% (initial COD 200 mg/L) and 72.54% (initial COD 10,000 mg/L), demonstrating excellent adaptability and efficiency in treating refractory high-salt organic wastewater. Electron spin resonance confirmed •OH as the main reactive species. Molecular simulations revealed that the MNB interface enhances the adsorption energy of Fe and H₂O₂, alters the Fe 3d orbital to better overlap with the O–O 2p orbital, and increases electron density—thus promoting O–O bond cleavage and free radical generation. The FT-MNBs not only enhances reaction kinetics but also offer scalability and energy efficiency, showing great potential for advanced industrial wastewater treatment. Full article

This study explores the visible-light-driven photolysis of Ferrioxalate complexes for the degradation of Toluidine Blue (TB), a persistent phenothiazine dye, using a 1 L recirculating batch-loop photoreactor. The reactor system incorporated two tubular photochemical units (35 cm × 3 cm each) in series: the first equipped with an immersed blue fluorescent lamp (12 W, 30 cm-tube), and the second with dual external blue LED lamps (18 W total, 30 cm) encasing a double-walled glass cell. Continuous flow between the units was maintained via a peristaltic pump. Experimental investigations were used to evaluate the effects of key parameters such as Fe(III) and oxalate concentrations, initial TB load, pH, light source, flow rate, ligand type, dissolved gas type, external H₂O₂ addition, and the presence of various inorganic ions. The results demonstrate efficient dye degradation, with ~75% TB removal within 1 h under combined fluorescent and LED irradiation, where each reactor contributing comparably. The optimal performance was achieved at pH 4, with a 10 oxalate-to-Fe(III) molar ratio (1 mM:0.1 mM) and a flow rate of 25 mL s⁻¹. Among various ligands tested (oxalate, acetate, citrate, EDTA), oxalate proved to be the most effective. The presence and type of anions significantly influenced degradation efficiency due to their potential scavenging effects. Although the process achieved high dye removal, TOC analysis indicated only moderate mineralization, suggesting the accumulation of non-colored intermediates. External H₂O₂ addition moderately improved TOC removal, likely due to enhanced hydroxyl radical generation via the Fenton mechanism. These findings highlight the promise of Ferrioxalate-based photochemical systems under visible light for dye removal, while also emphasizing the need for further research into by-product identification, mineralization enhancement, and toxicity reduction to ensure safe effluent discharge. Full article

The development of stable and efficient heterogeneous Fenton oxidation for organic pollutant degradation is crucial to avoid iron sludge formation and cumbersome filtration processes. In this study, iron oxide/carbon aerogel was prepared via the sol–gel method, freeze-drying, and high-temperature carbonization using iron nitrate heptahydrate, ammonium hydroxide, and cellulose as raw materials, with polyvinylimine serving as the crosslinking agent. To enhance the pH adaptability of the catalyst, copper and cerium elements were introduced. The characterization results demonstrate the iron (III) oxide within the carbon aerogel, achieving phenol degradation efficiency exceeding 95% within 120 min. Meanwhile, the introduction of copper and cerium accelerated the degradation of phenol while maintaining a certain catalytic degradation effect at pH 5-7. In addition, the catalyst exhibited excellent recyclability, retaining 85% of its initial degradation efficiency after five reaction cycles. This work offers a new method for the development of heterogeneous Fenton catalysts. Full article

The presence of acetaminophen (ACTP) in aquatic environments has become a significant concern due to its environmental persistence and the potential formation of toxic transformation products. This study systematically compares the performance of three electrochemical advanced oxidation processes (EAOPs), electro-oxidation (EO), electro-Fenton (EF), and solar photo-electro-Fenton (SPEF), for the degradation and mineralization of ACTP in aqueous media using boron-doped diamond (BDD) electrodes. Reactions were conducted under varying operational parameters, including current densities (15–60 mA cm⁻²), initial ACTP concentrations (10–30 mg L⁻¹), and Fe²⁺ dosages. In the SPEF system, natural sunlight was utilized as the source of UV-A irradiation (30–35 W m⁻²). Among the evaluated processes, SPEF exhibited the highest degradation efficiency, achieving up to 97% ACTP removal and 78% chemical oxygen demand (COD) reduction within 90 min. High-performance liquid chromatography (HPLC) analysis identified phenol and catechol as major intermediates, suggesting a degradation pathway involving hydroxylation, aromatic ring cleavage, and subsequent oxidation into low-molecular-weight carboxylic acids. Kinetic modeling revealed pseudo-first-order behavior, with a maximum rate constant of 0.0865 min⁻¹ under optimized conditions determined via Box–Behnken experimental design. Additionally, SPEF demonstrated enhanced energy efficiency (~0.052 kWh gCOD⁻¹) and improved oxidant regeneration under solar radiation, highlighting its potential as an environmentally friendly and cost-effective alternative for pharmaceutical wastewater treatment. These results support the implementation of SPEF as a sustainable strategy for mitigating the environmental impact of emerging contaminants, especially in regions with high solar availability and limited technological resources. Full article

Sulfamethazine (SMT) is an antibiotic with good antimicrobial effect and is widely used to treat human and livestock diseases. Though the degradation of SMT by the conventional Fenton and electro-Fenton (EF) processes is efficient, it is limited by a narrow pH and iron sludge generation. Herein, we constructed a cost-effective EF system with the synergistic effect of zero-valent iron (Fe⁰) and sulfite (Fe⁰-EF/Sulfite), and key parameters such as applied current, catalyst dosing, sulfite dosage, and initial pH were optimized. Under the optimal conditions (Fe⁰ dosing of 50 mg/L, sulfite dosage of 1.5 mM, current of 40 mA, and pH of 3), the removal efficiency of 10 mg/L SMT reached 100% within 30 min, and the degradation rate constant reached 0.194 min⁻¹. Electron paramagnetic resonance (EPR) analysis and quenching experiments confirmed the generation of various reactive oxygen species (ROS), such as ^•OH, SO₄⁻, O₂⁻, and ¹O₂, which significantly improved the pollutant removal efficiency. Sulfite accelerated iron cycling and inhibited the formation of iron sludge, thus broadening the pH range of the reaction from three to eight and overcoming the limitations of the conventional EF process. The Fe⁰-EF/Sulfite system performs cost-effectively at a wide pH range, providing an efficient and low-carbon solution for environmental pollution remediation with broad application prospects. Full article