Search Results (1,317)

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

The study presents research on the use of modified lignocellulosic biomass as a waste sorbent for the removal of anionic dyes from aqueous solutions. The sawdust used as sorption material was subjected to an acid-base modification and further functionalised by introducing amino groups into the biomass structure. Dynamic sorption experiments were carried out in two reactor types (airlift and column) with two sorbents: sawdust treated under acid-base conditions (S-AB) and sawdust aminated with epichlorohydrin after acid-base treatment and preactivation (S-AB-EA). The anionic dye Reactive Black 5 (RB5) was used as a sorbate. The experiments were carried out at two flow rates (0.1 and 0.5 dm³/h) and two feed concentrations (10 and 50 mg/dm³), maintaining the pH of the solution at 3, as determined in previous studies. The experimental data allowed the maximum sorption capacities of the tested sorbents to be determined under dynamic conditions and were described using the Thomas, Adams-Bohart and Yoon-Nelson models. The results showed that the flow rate, the dye concentration and the reactor type strongly influence the efficiency of dye removal. The highest capacity, 73.89 mg/g, was achieved in the airlift reactor for aminated sawdust and preactivation with epichlorohydrin (S-AB-EA) at a feed concentration of 50 mg/dm³ and a flow rate of 0.1 dm³/h. Full article

The removal of cationic dyes from industrial wastewater presents a significant environmental challenge. This research examines the effectiveness of functionalized cellulose-based silica aerogels as sustainable adsorbents for methylene blue (MB) dye. This research provides a systematic comparative study on the effectiveness of four distinct functionalization strategies, carboxylate (CCNC), double carboxylate (DCCNC), carboxymethyl (CMC), and thiol-modification, applied to cellulose-based silica aerogels as sustainable adsorbents for methylene blue (MB) dye. Cellulose nanocrystals (CNCs) were extracted from sugarcane bagasse waste and subsequently functionalized into carboxylate (CCNC), double carboxylate (DCCNC), carboxymethyl (CMC), and thiol-modified variants. The materials were later integrated into a silica matrix, resulting in the formation of porous aerogel nanocomposites. The materials underwent thorough characterization through FTIR, XRD, SEM, TGA, and BET analyses, validating successful functionalization and the development of mesoporous structures. Batch adsorption tests demonstrated that the CMC-silica aerogel exhibited superior performance, attaining a maximum adsorption capacity of 197 mg/g and complete removal efficiency under ideal circumstances (pH 10, 25 °C, 60 min). The adsorption process is accurately characterized by the Langmuir isotherm and pseudo-second-order kinetic models, signifying monolayer adsorption and chemisorption as the rate-limiting step. The thermodynamic parameters indicate that the adsorption process is exothermic and spontaneous. The CMC-silica aerogel exhibited significant reusability, maintaining over 90% efficiency after six consecutive cycles. The findings illustrate the efficacy of functionalized cellulose–silica aerogels, especially the CMC form, as effective, environmentally sustainable, and reusable adsorbents for the treatment of dye-polluted water. Full article

In this study, Fe₂O₃–TiO₂ nanocomposites with different TiO₂ contents (1–50%) were synthesized via a solvothermal method using pre-formed α-Fe₂O₃ nanoparticles as cores. We systematically evaluated the influence of TiO₂ loading on the nanocomposites’ structural, morphological, optical, and photocatalytic properties. X-ray diffraction revealed the coexistence of hematite and anatase phases, with an increase in TiO₂ content inducing reduced crystallite size, enhanced dislocation density, and microstrain, indicating interfacial lattice distortion. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) showed a uniform elemental distribution at low TiO₂ contents, evolving into irregular agglomerates at higher loadings. Fourier-transform infrared (FTIR) spectra indicated the suppression of Fe–O vibrations and the appearance of hydroxyl-related bands with TiO₂ enrichment. Diffuse reflectance spectroscopy (DRS) analysis confirmed the simultaneous presence of hematite (~2.0 eV) and anatase (3.2–3.35 eV) absorption edges, with a slight blue shift in the TiO₂ band gap at higher concentrations. Photocatalytic activity, assessed using methylene blue degradation under xenon lamp irradiation, demonstrated a strong dependence on the TiO₂ fraction. The composite containing 33% TiO₂ achieved the best performance, with 98% dye removal and a pseudo-first-order rate constant of 0.045 min⁻¹, outperforming both pure hematite and commercial P25 TiO₂. These results highlight that intermediate TiO₂ content (~33%) provides an optimal balance between structural integrity and photocatalytic efficiency, making Fe₂O₃–TiO₂ heterostructures promising candidates for water purification under simulated solar irradiation. Full article

This study transformed discarded courgette biomass into biochar (BC) via pyrolysis at 500 °C and employed it as an activator of potassium periodate (PI) for atrazine (ATZ) degradation. Characterization analyses confirmed that the synthesized BC possessed a porous structure, a high carbon content (76.13%), crystalline SiO₂, KCl, and CaCO₃ phases, as well as abundant oxygen-containing functional groups (–OH, C=O, C=C, –COOH), which are favorable for catalytic activation. The point of zero charge of 4.25 indicates that the BC surface carries a suitable charge distribution, promoting effective electrostatic interactions under near-neutral pH conditions. Under optimal operating conditions (neutral pH, [ATZ]_o = 7.3 mg/L, [PI]_o = 2.7 mM, [BC]_o = 0.55 g/L, and 25 ± 0.5 °C), the system achieved 99.35% ATZ removal (first-order kinetic rate constant = 0.0601 min⁻¹) and 64.23% TOC mineralization within 60 min. Quenching tests confirmed iodate radicals and singlet oxygen as the primary species, with hydroxyl and superoxide radicals playing secondary roles. The proposed mechanism suggests that electron transfer from oxygen-containing groups on the BC surface activates PI, leading to the generation of reactive oxygen species that facilitate ATZ degradation via synergistic radical and non-radical pathways. The BC catalyst exhibited strong recyclability, with only ~9% efficiency loss after five cycles. The BC/PI system also demonstrated high removal of tetracycline (79.54%) and bisphenol A (85.6%) within 60 min and complete Congo red dye degradation in just 30 min. Application to real industrial wastewater achieved 72.77% ATZ removal, 53.02% mineralization, and a treatment cost of 1.2173 $/m³, demonstrating the practicality and scalability of the BC/PI system for sustainable advanced wastewater treatment. Full article

Although fast-paced ongoing industrial growth, on the one hand, enhances the lifestyle of the population, on the other hand, it affects human health and the environment as a result of the discharge of pollutants. To address this, designing a novel and effective photocatalyst is necessary to mitigate increasing environmental pollutants. In the present work, we aim to synthesize a single-phase high-entropy zirconate pyrochlore oxide (Ce_0.2Pr_0.2Zn_0.2Nd_0.2Tb_0.2)₂Zr₂O₇ using a modified Pechini method. The physicochemical properties of the prepared nanoparticles were investigated using X-ray diffraction, UV-visible spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic properties were examined using cationic dye (methylene blue), anionic dye (Congo red), and Cr(VI). Photocatalytic degradation experiments demonstrate exceptional efficiency in the removal of persistent organic pollutants. The photocatalytic results indicate that the prepared high-entropy (Ce_0.2Pr_0.2Zn_0.2Nd_0.2Tb_0.2)₂Zr₂O₇ zirconate pyrochlore oxide could effectively degrade dyes and reduce Cr(VI). Radical trapping experiments indicate that the degradation of dyes was driven by the hydroxyl radicals, superoxide radicals, and holes. Furthermore, the position of the valence band and conduction band promoted efficient photocatalytic reaction kinetics. The prepared photocatalyst remains structurally stable and can be reused three times without losing activity. Full article

The main goal of this study is to address the problem of environmental water pollution caused by organic dyes through waste valorization by synthesizing geopolymer-based adsorbents. In this work, geopolymers were synthesized using fly ash modified with chitosan and polyvinyl alcohol as a starting material. The obtained materials were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and determination of the point of zero charge. We examined the adsorption potential for organic dye (methylene blue, brilliant green, crystal violet) removal through the influence of contact time, initial pH and concentration of adsorbate solution, and temperature on adsorption. The obtained results were analyzed using theoretical kinetics and isotherm models. Interpretation of the obtained results was performed using the Box–Behnken design and chemometric methods of multivariate analysis. The findings showed that modification with chitosan significantly enhanced the adsorption efficiency of the synthesized materials up to 95.9% for methylene blue adsorption. The parameters identified as having the greatest influence on the adsorption process were contact time, pH-value, initial dye concentration, and the type of dye being adsorbed. Full article

Emerging contaminants such as per- and polyfluoroalkyl substances (PFASs) pose significant challenges for conventional wastewater treatment technologies. Non-thermal plasma (NTP) has gained attention as a promising advanced oxidation process capable of degrading persistent pollutants via hydrated electrons and reactive oxygen/nitrogen species under ambient conditions. This review summarizes recent progress in the application and scale-up of NTP for water treatment, with a focus on reactor configurations, degradation mechanisms, and energy efficiency. Key plasma reactor types—including dielectric barrier discharge, corona discharge, plasma jets, and gliding arc discharge—are evaluated for their suitability in large-scale applications. Pilot-scale studies addressing pharmaceuticals, dyes, and PFASs are reviewed to assess scalability, cost, and operational viability. Although NTP systems consistently achieve >80% contaminant removal, optimizing energy use and maintaining performance across complex water matrices remain critical challenges. Hybrid systems integrating NTP with ozonation, ultrafiltration, or cavitation show potential to improve treatment efficacy and reduce energy demands. Future research priorities include reactor design optimization, contaminant-specific plasma tuning, and technoeconomic analysis to support the translation of NTP technologies from lab-scale innovation to field-scale implementation. Full article

Bio-gels are a class of functional polymeric materials with three-dimensional network structures. Their exceptional biocompatibility, biodegradability, high specific surface area, and tunable physicochemical properties make them highly promising for environmental remediation. This article systematically reviews the classification of bio-gels based on source, cross-linking mechanisms, and functional attributes. It also elaborates on their fundamental properties such as porous structure, high water absorbency, stimuli-responsiveness, and mechanical stability and examines how these properties influence their environmental remediation efficiency. This review comprehensively analyze the mechanisms and efficacy of bio-gels in adsorbing heavy metal ions, removing organic dyes, improving soil water retention, and restoring ecosystems. Special attention is given to the interactions between surface functional groups and contaminants, the role of porous structures in mass transfer, and the ecological effects within soil–plant systems. Additionally, this review explores extended applications of bio-gels in medical tissue engineering, controlled release of drugs and fertilizers, and enhanced oil recovery, highlighting their versatility as multifunctional materials. Finally, based on current progress and challenges, this review outline key future research directions. These include elucidating microscopic interaction mechanisms, developing low-cost renewable feedstocks, designing multi-stimuli-responsive structures, improving long-term stability, and establishing full life-cycle environmental safety assessments. These efforts will help advance the efficient, precise, and sustainable use of bio-gels in environmental remediation, offering innovative solutions to complex environmental problems. Full article

The discharge of dye-laden effluents remains an environmental challenge since conventional treatments remove color but not the organic load. This study systematically compared anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes for three representative industrial dyes, such as Coriasol Red CB, Brown RBH, and Blue VT, and their ternary mixture, using boron-doped diamond (BDD) and Ti/IrO₂–SnO₂–Sb₂O₅ (MMO) anodes. Experiments were conducted in a batch reactor with 50 mM Na₂SO₄ at pH = 3.0 and current densities of 20–60 mA cm⁻². Kinetic analysis showed that AO-BDD was most effective at low pollutant loads, EF-BDD became superior at medium loads due to efficient H₂O₂ electrogeneration, and PEF-MMO dominated at higher loads by fast UVA photolysis of surface Fe(OH)²⁺ complexes. In a ternary mixture of 120 mg L⁻¹ of dyes, EF-BDD and PEF-MMO achieved >98% decolorization in 22–23 min with pseudo-first-order rate constants of 0.111–0.136 min⁻¹, whereas AO processes remained slower. COD assays revealed partial mineralization of 60–80%, with EF-BDD providing the most consistent reduction and PEF-MMO minimizing treatment time. These findings confirm that decolorization overestimates efficiency, and electrode selection must be tailored to dye structure and effluent composition. Process selection rules allow us to conclude that EF-BDD is the best robust dark option, and PEF-MMO, when UVA is available, offers practical guidelines for cost-effective electrochemical treatment of textile wastewater. Full article

A highly active Co/Beta catalyst was prepared via ion-exchange method, in which sodium cations in the beta zeolite framework were replaced by cobalt ions using an aqueous cobalt nitrate solution. Based on XRD, SEM, TEM, XPS, and nitrogen adsorption–desorption analyses, it was confirmed that cobalt species successfully took the place of sodium ions in beta zeolite, while the cobalt species diffused with a uniform dispersion. Strong electronic coupling between cobalt species and zeolite framework oxygen stabilizes Co²⁺ sites in the material. The catalysts perform high efficiency in dye Acid Orange II (AO7) degradation reactions, which gives more than 99.5% removal efficiency at room temperature and initial pH within 10 min under low catalyst dosage. The advantages of the Co/Beta catalyst are reasonably attributed to its maximized metal−zeolite synergistic efficiency. Full article

Textile industries release dyes into wastewater, and when present above certain levels, these dyes pose serious risks because of their high toxicity. This study investigates the removal of Sunset Yellow (SY) and Methylene Violet (MV) dyes from wastewater using chitosan (CS) and polysilicate acid (pSi) in the structure of aluminum-based coagulants, resulting in hybrid formulations (CS@Al, Al/pSi, and CS@Al/pSi). Among the various treatment methods that have been applied for the removal of dyes, the coagulation/flocculation process was chosen in the present study, as it is a cheap and effective method. Coagulation performance was optimized for pH, coagulant dosage, temperature and mixing time. The Al/pSi coagulant achieved nearly complete SY removal (98.8%) at 25 mg/L dosage and pH 3.0. MV removal in single-dye solutions was limited, with Al/pSi achieving only 26.6% removal at pH 3.0. However, in mixed-dye systems (SY/MV), synergistic interactions increased MV removal up to 94.4% and SY removal to 100%. Hybrid CS@Al/pSi showed lower SY removal (36.4%) for SY at 50 mg/L but provided stable floc formation, particularly in mixtures of anionic and cationic dyes. Application to real textile wastewater confirmed the high efficiency of the optimized coagulants, particularly with Al/pSi_20,A and AlCl₃, indicating their potential for industrial wastewater treatment. SEM, EDS, XRD, and FTIR analyses revealed structural consolidation, increased surface area, and successful dye adsorption, explaining the high removal efficiency. Full article

Bio-waste from potato shell agro-waste-based photocatalyst is introduced using potato shell integrated with Fe₃O₄ nanoparticles as a novel photocatalyst for photo-Fenton oxidation reaction. The catalyst was prepared via thermal activation of biochar, followed by co-precipitation of magnetite nanoparticles, resulting in a stable and reusable material. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques augmented with the energy dispersive X-ray spectroscopy (EDX) analysis with elemental mapping were used to assess the prepared sample. The prepared material, PtS200–Fe₃O₄, is then applied for oxidizing Procion Blue dye using biochar-supported magnetite catalyst. The oxidation process was evaluated under varying operational parameters, including pH, temperature, catalyst loading, oxidant dosage, and dye concentration. Results revealed that the system achieved complete dye removal within 20 min at 60 °C and pH 3, demonstrating the strong catalytic activity of the composite. Furthermore, the kinetic modeling is evaluated and the data confirmed that the degradation followed first-order kinetics. Also, the thermodynamic parameters indicated low activation energy with PtS200–Fe₃O₄ composite in advanced oxidation processes. The system sustainability is also assessed, and the reusability test verified that the catalyst retained over 70% efficiency after six consecutive cycles, highlighting its durability. The study confirms the feasibility of using biochar-supported magnetite as a cost-effective, eco-friendly, and efficient catalyst for the treatment of textile effluents and other dye-contaminated wastewater. Full article

The increasing discharge of organic pollutants such as dyes and antibiotics poses severe threats to aquatic ecosystems and human health. Conventional wastewater treatment methods are often limited by high energy consumption, secondary pollution, or low efficiency under visible light. It is crucial to design novel photocatalysts that can simultaneously utilize visible photons and enable swift transport of photoinduced charge carriers to drive contaminant decomposition. Herein, novel BiOCl/MIL-121 composites were synthesized via a straightforward hydrothermal route. A suite of complementary microscopic and spectroscopic analyses, including SEM, TEM, XRD and XPS, were employed to elucidate the material’s composition. Furthermore, collective evidence from spectroscopic and electrochemical analyses confirms markedly improved light absorption and charge separation efficiency within the BiOCl/MIL-121 photocatalyst. The 5% BiOCl/MIL-121 composite achieved 93.7% removal of Rhodamine B in 60 min, exhibiting a high photocatalytic degradation rate. Similarly, 5% BiOCl/MIL-121 photodegraded 80.4% of tetracyclin, which was much better than that of BiOCl. A plausible interfacial charge-transfer mechanism was deduced from the band structure of the 5% BiOCl/MIL-121 composite and experimental evidence from radical scavenger studies. This study provides an effective strategy for constructing a composite photocatalyst and offers a green way for the efficient degradation of organic pollutants. Full article

Eco-friendly clay-based adsorbents with low cost and high adsorption capacity for toxic dyes have attracted significant attention. In this study, a novel citric acid-modified sepiolite (CA-SEP) composite was developed for the efficient removal of methylene blue (MB) from aqueous solutions. The morphological, crystalline, and structural properties of the composite were characterized using XRD, FTIR, SEM, and BET analyses. Compared to pristine SEP, CA-SEP exhibited a 2.6-fold increase in adsorption capacity for MB and demonstrated excellent reusability. The effects of key parameters—including solution pH (2.0–10.0), contact time (0–300 min), adsorbent dosage (0.2–2.0 g/L), and initial MB concentration (10–150 mg/L)—on adsorption performance were systematically investigated. Modeling results indicated that the Sips isotherm provided the optimal fit for the equilibrium data. In kinetic studies, the adsorption process was best described by the pseudo-second-order model. The maximum adsorption capacity of CA-SEP for MB was estimated to be 40.61 mg/g. Moreover, the adsorbent retained high removal efficiency after five adsorption-desorption cycles, demonstrating good regenerability. These results indicate that CA-SEP is a highly efficient, sustainable, and economically viable adsorbent for the elimination of MB from contaminated water. Full article