Search Results (2,615)

Manganese dioxide (MnO₂) modified biochar catalysts derived from biomass and waste polymer feedstocks were synthesized and evaluated as heterogeneous Fenton-like catalysts for solar-driven degradation of Rhodamine B (RhB) in aqueous systems. Biochars produced from maple wood and plastic waste (high-density polyethylene) provided porous carbon matrices with oxygen-rich surface functionalities that enabled effective MnO₂ loading and catalytic activity. Photocatalytic experiments conducted under real sunlight using a solar-collector reactor demonstrated faster RhB degradation compared to a conventional ultraviolet (UV) system, confirming the advantage of solar-driven operation. Complete RhB removal was achieved at initial concentrations of 100–300 ppm, whereas higher dye concentrations (500 ppm) exceeded the catalytic capacity within the tested reaction time. Kinetic analysis revealed catalyst-dependent reaction behaviors, indicating that degradation pathways were strongly influenced by the biopolymer-derived carbon structure and MnO₂ dispersion. Degradation efficiency was correlated with solar irradiance and reactor temperature, with higher UV index conditions enhancing catalytic performance. Reusability tests showed that the catalysts remained active over multiple cycles, although gradual decreases in reaction rates and catalyst recovery were observed. These results demonstrate the potential of biopolymer-derived carbon materials as effective solar-driven catalysts for wastewater treatment applications. Full article

A heteroatom-rich pyridine-based adsorbent (Pyridine PC) was synthesized through a multicomponent strategy and structurally confirmed by ¹H/¹³C NMR spectroscopy and mass spectrometry. To further enhance adsorption activity and surface reactivity, waste-derived CuO nanoparticles were immobilized onto the porous heterocyclic framework, generating a sustainable CuO@Pyridine PC hybrid nanocomposite. Batch adsorption experiments demonstrate highly efficient removal of malachite green (MG) dye and Cd(II) ions from aqueous solutions. Kinetic analysis reveals that adsorption follows the pseudo-second-order model, while equilibrium data are best described by the Freundlich isotherm, indicating adsorption on heterogeneous surfaces. Thermodynamic parameters confirm that the adsorption processes are spontaneous and exothermic. Surface and structural characterization using SEM/EDX, elemental mapping analysis and FT-IR before and after adsorption verifies strong pollutant binding and highlights the role of nitrogen- and oxygen-containing functional groups as dominant interaction sites. BET measurements show that CuO incorporation increases surface area and pore volume, while zeta potential analysis indicates excellent colloidal stability of the composite in aqueous media. Consequently, the CuO-modified sorbent exhibits enhanced adsorption capacities, increasing from 169.8 to 176.13 mg g⁻¹ for MG and from 276.5 to 368 mg g⁻¹ for Cd(II). The adsorbent demonstrated effective pollutant removal from real wastewater. The adsorption mechanism involves synergistic interactions between functional groups in the Pyridine PC matrix and CuO nanoparticles, providing enhanced active binding sites. Full article

Textile wastewater is among the most challenging industrial effluents due to its complex composition, high pollutant load, and low biodegradability. Conventional treatment methods often fall short in achieving complete removal of dyes and emerging contaminants. Photocatalytic composite membranes have emerged as a promising solution by integrating membrane separation and advanced oxidation processes. This review provides a comprehensive overview of the design, fabrication, and performance of photocatalytic composite membranes for textile wastewater treatment. Key aspects include the types of photocatalysts employed, methods of incorporation into membranes, and their synergistic role in pollutant removal and membrane fouling mitigation. Recent advancements in materials science, such as visible-light-responsive catalysts, carbon-based nanocomposites, and self-cleaning surfaces, are discussed, along with current limitations related to catalyst stability, operational scalability, and cost. This review underscores the potential of photocatalytic composite membranes as a next-generation platform for sustainable and effective textile wastewater treatment. Full article

Large wastewater treatment plants (WWTP) are increasingly supplemented with quaternary treatment. Classical monitoring hereby relies mostly on the measurement of oxygen demand, micropollutants and the nutrients phosphorus and nitrogen. From a microbiological perspective, relevant parameters to assess treatment performance include the removal efficacies of the fecal gene load as a proxy of pathogenic risk, antibiotic resistance genes and the bacterial regrowth potential. For this purpose, a combination of flow cytometry and quantitative PCR, together with a viability assessment, was applied to characterize a full-scale pilot plant. The pilot plant comprised conventional treatment and MBR and ozonation for advanced treatment. The assessment of fecal gene load was based on the quantification of Bacteroidales of human origin, as these obligate anaerobic bacteria cannot replicate within wastewater treatment plants. Whereas conventional treatment resulted in only moderate removal of these parameters, quaternary treatment typically led to a much stronger decrease. MBR treatment contributed most strongly to the removal with an appr. 6 log reduction compared to the primary clarification effluent, corroborating its microbiological merit for wastewater treatment. In addition to removing microorganisms and their genetic content, data also suggested a 95% reduction in extracellular DNA. Ozonation further enhanced microbiological removal. From an analytical perspective, the study shows the added value of using a long amplicon qPCR approach together with sample treatment with a viability dye to minimize false-positive signals and to avoid underestimation of treatment performance. The chosen diagnostic approach shows promise in assessing the microbiological treatment efficacy of WWTPs and as a basis to decide on the microbiological necessity of treatment upgrades. Full article

The textile industry consumes a significant quantity of water and produces effluent containing water-soluble dyes and heavy metals such as Lead (Pb), Cadmium (Cd), Chromium (Cr), Copper (Cu), and Zinc (Zn), among others. Heavy metal contamination of water bodies and their impact on aquatic life, as well as on human health, is of prime importance. This review examined the potential of phytoremediation, a low-cost and eco-friendly process for removing contaminants from textile effluent. This review also investigated the impact of heavy metal toxicity on aquatic plants used for biogas production post phytoremediation application. This review evaluated textile effluent characteristics, efficiency evaluation of phytoremediation of textile wastewater, metal uptake mechanisms of aquatic plants, and anaerobic digestion processes with emphasis on Water hyacinth (Eichhornia crassipes), Duckweed (Lemna minor), and Water lettuce (Pistia stratiotes). The findings indicated that these aquatic plants possess immense potential for removing heavy metals and other impurities by employing phytoextraction and rhizofiltration methods. Their rapid growth rate makes them preferred candidates for anaerobic digestion. However, accumulation of heavy metals in plant tissues inhibits microbial activities during anaerobic digestion, resulting in fluctuations in biogas and methane production. Findings also showed that these aquatic plants are efficient in the removal of heavy metals in water while yielding considerable biomass that can be used to produce bioenergy through anaerobic digestion. However, the sequestration of heavy metals in plant biomass may affect the rate of methane generation efficiency. The findings of this review suggest that phytoremediation has promising potential for the recycling of textile wastewater and, when coupled with biogas production, contributes towards a circular bioeconomy, an approach that integrates closed-loop resource utilization with renewable biological systems to minimize waste. Full article

Textile wastewater contains recalcitrant dyes and organic matter, requiring efficient, scalable treatment technologies. This study optimized an aluminum-based electrocoagulation (EC) process to maximize color removal (Y₁) and chemical oxygen demand (COD) reduction (Y₂) using synthetic textile wastewater (SWW), and evaluated the practical transferability of the optimized conditions using real textile wastewater (RTW). A rotatable central composite design (CCD) coupled with response surface methodology (RSM) was used to assess the effects of treatment time, NaCl concentration, and applied voltage on both responses. From a modeling perspective, the results reveal the coexistence of symmetric and asymmetric response behaviors; quadratic effects define locally symmetric regions around the optimum, while interaction terms introduce asymmetry due to coupled electrochemical phenomena. Under the optimized conditions (16.5 min, 2.9 g·L⁻¹ NaCl, 18 V), removal efficiencies reached 99% for color and 97% for COD reduction, with a specific energy consumption of 6.6 kWh·m⁻³ and sludge moisture content of 92–94%. To assess applicability beyond bench scale, the optimized voltage, current, and electrolyte concentration were applied to a 50 L batch of RTW collected from the final rinsing stage of a denim dyeing process. Treatment time was extended to 84 min to compensate for the lower current density at the larger scale; under these conditions, 95% color removal and 80% COD reduction were achieved. Full article

Developing practical low-cost adsorbents for dye-contaminated wastewater remains a critical challenge, especially for persistent cationic dyes such as crystal violet (CV). Here, raw rockmelon skin (RMS), an abundant fruit-processing residue, and its NaOH-modified derivative (NaOH-RMS) were investigated as adsorbents for CV adsorption. Alkaline treatment altered the biomass’s characteristics and affected its adsorption behaviour. Equilibrium was reached within 120 min, and the kinetic data were best fit by the pseudo-second-order model. Equilibrium analysis showed that the Freundlich model best described RMS. In contrast, NaOH-RMS was better represented by the Langmuir model, indicating that alkaline treatment altered the adsorption behaviour of the biomass surface. The Langmuir-derived maximum adsorption capacities were 343.7 mg g⁻¹ for RMS and 295.2 mg g⁻¹ for NaOH-RMS, indicating that NaOH modification did not increase the maximum adsorption capacity. Adsorption was spontaneous across 298–343 K, and both materials retained satisfactory removal performance over five regeneration cycles, particularly under basic desorption conditions. Overall, NaOH treatment altered the adsorption behaviour from heterogeneous adsorption on RMS to a more Langmuir-type adsorption pattern on NaOH-RMS, despite not increasing the maximum adsorption capacity. These findings support the valorisation of fruit-processing residues as practical adsorbents for dye-contaminated wastewater. Full article

The development of efficient and low-cost adsorbents for dye-contaminated wastewater remains an important challenge in environmental remediation. In this study, an interlayer-expanded polypyrrole/maghnite–Cu²⁺ nanocomposite (PPy/Mag–Cu²⁺) was successfully synthesized through purification of raw maghnite, sodium activation, Cu²⁺ ion exchange, and in situ oxidative polymerization of pyrrole. The obtained hybrid was characterized by X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, UV–Vis spectroscopy, scanning electron microscopy, and cyclic voltammetry. The results confirmed the successful incorporation of Cu²⁺ and polypyrrole while preserving the layered aluminosilicate framework. XRD analysis revealed a progressive increase in basal spacing from 17.49 Å for raw maghnite to 25.95 Å for the final nanocomposite, indicating effective intercalation and formation of an expanded hybrid structure. The adsorption performance of PPy/Mag–Cu²⁺ was evaluated for methylene blue removal under batch conditions. Adsorption was strongly influenced by contact time, pH, and initial dye concentration, with equilibrium reached after approximately 80 min and optimum removal at pH 9. Equilibrium data were best fitted by the Langmuir model, with a maximum monolayer adsorption capacity of 43.66 mg g⁻¹, while kinetic data followed the pseudo-second-order model. These findings demonstrate that PPy/Mag–Cu²⁺ is a promising and cost-effective hybrid adsorbent for cationic dye removal from aqueous media. Full article

Sunset Yellow is a water-soluble synthetic dye resistant to degradation and stable under various conditions, posing an environmental challenge. In the present study pure chitosan hydrogel (PCH) films were synthesized, followed by the assessment of sorption capacity and recyclability compared to chitosan-based films doped with niobium oxide (CHN) or activated carbon (CHC). The aim was to promote the application of sorption methods for Sunset Yellow dye using these films as a treatment option for the pollutant, with the analysis of the effectiveness of the method and its behavior using adsorption kinetic models and thermodynamic analysis. Equilibrium was reached at 240 min for all films tested, with the adsorbed amounts ranging from 18.58 to 18.79 mg g⁻¹ at 30 °C, when the highest kinetic rate constants were observed. The pseudo-first-order kinetic model best described the experimental data, with the lowest Bayesian information criterion, Akaike information criterion, and mean absolute error values. Thermodynamic analysis indicated a spontaneous, exothermic process, with interactions ranging from electrostatic interactions in CHC and PCH to physisorption in CHN. Recycling tests showed 80% efficiency after the third cycle for all three films. These findings highlight the potential of chitosan-based films as an efficient option for removing Sunset Yellow dye from water, thus improving water quality and enhancing wastewater treatment. Full article

Azo dyes demonstrate dose-dependent carcinogenic and mutagenic effects in exposed cells. Among remediation approaches, microbial adsorption is the most sustainable and environmentally friendly method for eliminating azo dyes. A novel Aspergillus terreus silica composite was developed as a sustainable adsorbent for crystal violet dye (CVD) removal. The fungal strain was isolated from dye wastewater and was genetically identified by 18S rRNA gene sequencing. Dried mycelia of A. terreus (PX920301) were combined with SiO₂ (1:1 w/w) through iterative hydration-drying cycles, yielding a composite characterized by FTIR analyses. Removal CVD %, adsorption capacity, and CVD residual were calculated, and the adsorption process was optimized using Box–Behnken design (four factors, 25 runs). The biosafety of the composite was assessed for phytotoxicity and microbial toxicity. The composite was also applied to real dyes wastewater collected from the bacteriological laboratory. Aspergillus terreus-silica composite showed the highest CVD removal percentage by 85.4%, adsorption capacity (qe) 121.1 mg/L, and lowest CVD residual by 7.26 mg/L, followed by the dried active mycelia (DA-mycelia) with CVD removal 40.23%, adsorption capacity (qe) 57.05 mg/L, and CVD residual by 29.73 mg/L. Optimization data cleared that the maximum experimental values of CVD removal (%) was 99.59% (predicted value 100%) obtained in run number (4) using initial CVD concentration (200 mg/L), pH (8), adsorbent composite weight (0.1 g), and contact time (48 h). Biosafety evaluation demonstrated negligible phytotoxicity against Triticum aestivum seedlings post-treatment, with restored germination and growth comparable to controls. Microbial toxicity assays via well-diffusion to seven microbial isolates confirmed no toxic activities against the tested bacteria, yeast, and fungi, underscoring the composite’s environmental safety. The composite could decolorize the real dye wastewater of laboratories by 95.37%. In conclusion, A. terreus mycelial-silica composite offers a cost-effective, sustainable, and eco-friendly alternative solution for dye bioremediation. Full article

Metanil Yellow (MY), a highly toxic azo dye used in food products, was removed from aqueous solution using a metal- and halide-free ordered mesoporous carbon (OMC) adsorbent. MY exhibited a strong affinity towards OMC in batch as well as column operations, and OMC performed much better than previously reported adsorbents. The pH, dye concentration, adsorbent dosage, and contact time were optimised, and detailed adsorption experiments were performed under these conditions. Several isotherm models were fitted to the adsorption data, showing that the Langmuir and the Freundlich adsorption models were followed. Adsorption was spontaneous and endothermic at all measurement temperatures. On the basis of pH studies, enthalpy data, and adsorption isotherm analysis, adsorption was determined to be by physisorption. In kinetics studies, the adsorption process was found to be pseudo-second order with interparticle diffusion as the rate-limiting step. Column experiments using a fixed bed of OMC resulted in almost 100% column efficiency and a fractional column capacity of 0.999. During adsorption/desorption cycles of the exhausted column, 99.71% of the dye was recovered after the first cycle and 97.66% after the eleventh. These findings indicate that OMC is a promising and efficient material for the adsorptive removal of toxic MY dye. Full article

Water is one of the most valuable resources on the planet; without it, life as we know it could not exist. Consequently, its increasing scarcity and pollution, which are mainly due to industrialization and changing consumption patterns, intensify the stress on water resources. At the same time, industrial activities contribute to water contamination with pollutants such as heavy metals, further reducing water availability. Due to their risks to human health and ecosystems, effective removal strategies are essential. Among the emerging approaches, polymer-based additive manufacturing (AM), commonly known as 3D printing (3DP), has gained attention for water treatment due to its versatility, precise control over structure and porosity, and ease of processing, while remaining at a low cost. Additionally, the polymers used have interesting adsorbent properties and allow for the incorporation of functional additives, further enhancing their performance. This review analyses the recent advances in 3D-printed polymeric materials for the removal of heavy metals and dyes, focusing on material composition, manufacturing technologies, geometry, removal mechanisms, performance, and regeneration. It was concluded that metal ions and cationic dyes are primarily removed through adsorption, due to interactions with negatively charged surfaces that are often enhanced by high-affinity additives. Anionic dyes are generally less effectively removed by adsorption and often rely on degradation mechanisms. However, adsorption of anionic dyes can occur, for instance when the adsorbent surface is modified to introduce positively charged functional groups. The ability of 3DP to create hierarchical porous structures combining micro-, meso-, and macropores improves fluid flow and contact area, thereby enhancing the removal efficiency. Full article

In line with circular economy principles, raw spent yerba mate (Ilex paraguariensis) waste (YMs) was transformed into a high-value aminated adsorbent (AYMs) for the removal of anionic dyes, namely Reactive Black 5 (RB5) and Reactive Yellow 84 (RY84). The modification involved a two-step process using epichlorohydrin and aqueous ammonia, and the adsorbents were characterized via FTIR, BET, C/N elemental analysis, and pH_PZC. Batch experiments evaluated pH effects, kinetics (PFO, PSO, and intraparticle diffusion), and equilibrium isotherm analysis (single- and dual-site Langmuir models and Freundlich models). The results confirmed successful functionalization of the biomass with amino groups, shifting the point of zero charge (pH_PZC) from 4.74 (YMs) to 8.73 (AYMs). The optimal adsorption pH was 2.0 for YMs and 3.0 for AYMs. Kinetic data were best described by the pseudo-second-order model, while equilibrium data followed the dual-site Langmuir model, indicating energetic heterogeneity of the AYMs surface. The maximum adsorption capacity of AYMs reached 62.81 mg·g⁻¹ for RB5 and 61.78 mg·g⁻¹ for RY84, representing a fivefold and threefold increase over the YMs, respectively. These findings demonstrate that AYMs is a high-performance, sustainable alternative to commercial activated carbons, providing a scalable waste-to-value solution for industrial effluent treatment. Full article

Global water scarcity has intensified over recent decades, with projections suggesting that nearly six billion people may face limited access to clean water by 2050. Water reuse has emerged as a viable strategy to alleviate pressure on freshwater resources, particularly for non-potable applications. However, safe implementation requires wastewater to be treated to meet fit-for-purpose quality standards established through regional and national regulatory frameworks. Despite high levels of basic sanitation coverage in high-income countries such as the United States, persistent gaps remain in affordable and equitable wastewater management, particularly in small and underserved communities. This review focused on current knowledge of sustainable low-cost materials, including plant-based, clay, and clay-based ceramics; animal-derived products; and industrial by-products, used to remove a broad range of contaminants, including heavy metals, dyes, nutrients, emerging contaminants, and pathogens, from wastewater. The mechanisms governing their performance, such as adsorption, coagulation–flocculation, and filtration, were examined alongside contaminant-specific performance. The review further highlights the emerging role of 3D printing in developing customizable, efficient, and scalable treatment units using low-cost or waste-derived materials. Life cycle assessment (LCA) studies were evaluated to highlight their role as a flexible framework for assessing environmental impacts across life-cycle stages and for guiding the selection of sustainable materials and treatment systems. Together, these perspectives provide a comprehensive foundation for developing decentralized, community-oriented wastewater treatment solutions that support safe and effective water reuse, especially in rural and small communities. Full article

Constructed wetlands (CWs) are a low-energy alternative for treating dye-containing wastewater; however, the mechanisms enabling azo dye removal without external carbon supplementation remain unclear. This study demonstrates that azo dye reduction can proceed under oxic bulk conditions in CWs through vegetation-induced microscale redox heterogeneity. Lab-scale CWs planted with cattail and papyrus were evaluated for the removal of Reactive Orange 16 (RO16, monoazo) and Reactive Black 5 (RB5, diazo) at influent concentrations of 10–50 mg/L under varying ambient temperature (2–36 °C) and hydraulic retention time (1–15 days). Vegetated CWs consistently outperformed the unplanted system, achieving 60–95% removal for RO16 and up to 98% removal for RB5, whereas the unplanted CW showed substantially inferior performance, with removal efficiencies below 54% for RO16 and below 37% for RB5. Dye-decolorizing bacteria, including Priestia megaterium and Clostridium spp., were isolated exclusively under anaerobic conditions from vegetated CWs despite oxic bulk dissolved oxygen levels. The isolates did not decolorize dyes under aerobic conditions or when dyes were provided as sole carbon sources, indicating that azo dyes functioned as electron acceptors and required additional electron donors. These results suggest that vegetation promotes localized reductive microenvironments and supplies endogenous organic carbon, enabling anaerobic azo bond reduction within otherwise oxic systems. The findings indicate a mechanistic basis for plant–microbe interactions in CWs and support the design of sustainable treatment systems for dye-containing wastewater without external carbon input, particularly in warm regions. This study resolves a long-standing question of how azo dye reduction proceeds in CWs without external carbon input. Full article