Emulsified oily wastewater is difficult to treat because of its complex composition and high stability. This study developed a modified polyvinylidene fluoride (PVDF) membrane by integrating microcrystalline cellulose (MCC), tannic acid (TA), polydopamine (PDA), and controlled surface patterning, thereby combining multi-component chemical functionalization with hierarchical surface structuring. The membrane was fabricated by non-solvent-induced phase separation, surface embossing, MCC modification and regeneration, TA deposition, and PDA self-polymerization. The optimized D4 membrane, prepared with 3% MCC, 1% TA, 6h PDA polymerization, and a 20 μm imprinting depth, reduced the water contact angle from 81.7° to 44.0° and increased porosity from 67.32% to 82.67%. For edible-oil, engine-oil, and diesel-oil emulsions, D4 achieved fluxes of 170.24, 210.83, and 223.91L·m⁻²·h⁻¹ with rejection efficiencies of 94.73%, 98.03%, and 95.63%, respectively. In BSA fouling tests, FRR, Rt, Rr, and Rir were 89.6%, 40.3%, 29.9%, and 10.4%, respectively. The improved performance was associated with enhanced hydrophilicity and the SEM-observed peak–valley structure, supporting improved wetting, mass transfer, and fouling reversibility.
A systematic review complying with PRISMA 2020 synthesised 213 peer-reviewed publications published from 1 January 2021 to April 2026 on machine learning (ML)-based remote sensing for water-quality assessment in inland and watershed environments, selected from 902 Scopus records. China-affiliated authors contributed 51.2% of the publication, while Sentinel-2 MSI is the most frequently used platform, employed in 95 of the 213 studies (44.6%). Publication output increased at a compound annual growth rate of 40.3% between 2021 and 2025, based on complete publication years, indicating rapid expansion of the field. Ensemble methods and attention-enhanced deep learning architectures achieve R² values of 0.94 - 0.998 for optically active constituents (OACs), particularly chlorophyll-a and total suspended solids, under single-site calibration and validation conditions. Hybrid architectures such as HF-DFM and MDPC achieved R2 values of 0.81–0.93 for simultaneous retrieval of multiple non-optically active constituents, although performance was more variable under heterogeneous conditions. The evidence nonetheless indicates a persistent gap between local predictive accuracy and reliable cross-domain application, driven by limited spatial transfer across optically contrasting water bodies and by sensitivity to atmospheric-correction choices for the same Sentinel-2 imagery. Explainability and calibrated predictive uncertainty remain uncommon, reported in 9 and 8 of 213 studies (4.23% and 3.76%), respectively. The principal barriers to operational adoption are no longer incremental gains in site-specific accuracy, but insufficient evidence of spatial and temporal generalization, inconsistent preprocessing, limited uncertainty characterization, and geographic imbalance in training and validation data. Future research should therefore prioritise independent multi-site and multi-temporal validation, standardised atmospheric-correction protocols, transfer and representation learning for data-scarce environments, physics-informed modelling, and routine reporting of predictive uncertainty and model interpretability. Such advances are necessary to determine whether the high accuracies reported under controlled conditions can translate into reliable and transferable operational water-quality monitoring.
Chloride-induced corrosion is a major durability problem for reinforced concrete exposed to marine salts and cyclic wetting–drying. This study examines the long-term redistribution of water-soluble chloride and the evolution of pore alkalinity in reinforced M20 and M30 concrete subjected to atmospheric and alternate wetting–drying exposure, with and without zinc-based sacrificial cathodic protection (CP), over 700 days. Chloride profiles were determined at 12.5, 25, 37.5 and 50mm from the exposed surface using aqueous extraction followed by Mohr titration, while the local pH and electrochemical response of the reinforcement were monitored. In unprotected M30 concrete under atmospheric exposure, the measured chloride concentration increased from 0.459wt.% at 12.5mm to 0.716wt.% at 50mm in the nominally chloride-free condition, whereas CP produced the opposite depthwise trend, with values decreasing from 1.248 to 0.475wt.%. Under alternate wetting–drying, the corresponding unprotected M30 profile increased from 2.020 to 5.259wt.%, while CP reduced the 50mm value to 0.405wt.%. M20 showed the same qualitative response but greater chloride accumulation in the unprotected condition, consistent with its more permeable matrix. Across the investigated conditions, CP reduced the measured chloride concentration at reinforcement depth by approximately 33–92% relative to the corresponding controls and maintained pH values of about 12.6 near the steel. The results indicate that galvanic polarization can superimpose electromigration on diffusion- and moisture-driven transport, causing chloride depletion at the steel-side region and chloride enrichment in the outer cover. The study therefore contributes long-term, depth-resolved evidence linking galvanic CP, chloride redistribution and alkalinity evolution in two concrete grades under contrasting exposure regimes. The findings support the use of sacrificial CP as a corrosion-mitigation strategy, while the chloride profiles should be interpreted as redistribution measurements rather than direct proof of complete chloride extraction or guaranteed long-term passivity.
Air gap membrane distillation (AGMD) requires hydrophobic porous membranes that can minimize wetting while maintaining effective vapor transport, particularly for high-salinity water treatment. However, conventional polymeric membranes and nanocomposite modifications may not simultaneously provide adequate hydrophobicity and desalination performance. In this study, polysulfone (PSF) membranes were fabricated by non-solvent-induced phase separation using DMF at 17wt% and evaluated for AGMD desalination of 35g/L NaCl feed water. Six membrane configurations were prepared by incorporating raw graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs) at 0.05wt%, either individually or combined with a commercial silicone-based spray coating as a post-fabrication hydrophobic sealant agent (HSA). Membrane morphology, surface chemistry, topography, wettability, and porosity were characterized using FESEM, FTIR, AFM, water contact angle, and gravimetric measurements. Under identical operating conditions, the MWCNT-containing membrane with HSA coating (S5) achieved the best overall performance, with a water contact angle of 95°, salt rejection of 99%, and permeate flux of 11Lm⁻² h⁻¹. The results show that combining low-loading raw MWCNT incorporation with a simple post-fabrication HSA coating provides an effective surface-engineering strategy to improve membrane hydrophobicity and AGMD desalination performance without chemical functionalization.
Peanut shell waste was utilized for the recovery of cellulose and lignin and their potential environmental and cosmetic applications were investigated. Cellulose was extracted through sequential alkali treatment, acid reflux and bleaching, whereas lignin was recovered from the alkaline filtrate by acid precipitation. The extraction yields were approximately 42% for cellulose and 16% for lignin. FT-IR analysis showed the characteristic functional groups of the recovered biopolymers, while XRD analysis of extracted cellulose (EC) showed characteristic reflections near 22.6° and 34.8°. SEM revealed an irregular, porous morphology of EC and EDX detected 74.46% C and 18.86% O. TGA showed distinct thermal-decomposition profiles for EC and extracted lignin (EL), with EL retaining > 20% residual mass at 800 °C. UV-Vis analysis showed a marked decrease in the characteristic methylene blue (MB) absorption band at 663nm after treatment with EC, EL and extracted cellulose beads (ECBs), with powdered EC showing stronger removal performance than ECBs under the tested conditions. ECBs decreased in size from approximately 1.756mm when freshly prepared to 0.880mm after drying and were successfully incorporated into a laboratory-prepared facial scrubber. In the comparative survey, 58% of respondents preferred the laboratory-prepared formulation, highlighting the potential of peanut shell-derived biopolymers for dye remediation and biodegradable cosmetics.
The study was conducted to assess the characteristics of faecal sludge and septage collected from domestic septic tanks and latrine pits, and to develop a suitable eco-friendly treatment technology for mitigation of pollution caused by human excreta. A pilot scale model of integrated faecal sludge treatment plant of capacity, at the daily influent rate of 60litres, was established at Sonarpur, Kolkata, India. The plant composed of the treatment units - Bar Screen Chamber, Anaerobic Pond, Sludge Drying Beds, Aerobic Pond, Constructed Wetland, Polishing Pond and Stand-alone Filter, arranged in series. Nine complete cycles of treatment operations were completed from September, 2024 to August, 2025 across four climatic seasons. Performance evaluation of individual treatment units and the model plant was undertaken through laboratory examination and analysis of nine water quality parameters. Results showed that Anaerobic Pond and Sludge Drying Beds collectively removed major portion of contaminants. Total ‘average removal efficiency’ of these two units and that of the entire plant reached to: Total Suspended Solids - 94.53% / 98.44%, Chemical Oxygen Demand - 89.14% / 94.78%, Biochemical Oxygen Demand (BOD3) - 89.48% / 96.00%, Total Phosphorus – 72.88% / 95.12%, Total Nitrogen - 53.61% / 83.44%, Faecal Coliform - 96.10% / 99.69% and Total Coliform - 92.62% / 98.84%. The effluent water met the required discharge standard of government regulatory bodies (CPCB, India and EPA) in respect of the parameters - pH, TSS, COD and FC. However, further treatment and disinfection are needed to reduce the concentration of BOD3, TP, TN and TC to conform acceptable discharge standard and pathogen control.
The increasing production and use of surfactants have resulted in their widespread occurrence in municipal wastewater and aquatic environments. Routine monitoring remains challenging because conventional analytical methods are time-consuming, require large volumes of hazardous organic solvents, and are poorly suited to complex environmental matrices.This study evaluated the applicability of a simplified methylene blue active substances (MBAS) method for anionic surfactants and a modified spectrophotometric iodobismuthate (BiAS-thio) method for nonionic surfactants for routine monitoring in a full-scale municipal wastewater treatment plant serving approximately 67,500 population equivalent (PE).The proposed methods enabled reliable determination of both surfactant groups while substantially reducing analytical time and solvent consumption compared with conventional procedures. Statistical evaluation demonstrated excellent agreement between the simplified and reference MBAS methods. The treatment plant achieved removal efficiencies of 96.8% for anionic surfactants and 98.3% for nonionic surfactants.The scientific novelty of this work lies in the practical validation of simplified spectrophotometric methods that provide reliable, rapid, and less solvent-intensive determination of anionic and nonionic surfactants in complex municipal wastewater, making them suitable for routine environmental monitoring.
The influence of phase change material (PCM) concentration on solar still performance has received limited attention despite its importance for optimizing thermal energy storage and freshwater production. This study experimentally and theoretically investigated a 0.25m² conventional single-slope solar still enhanced with paraffin wax (PW) and external glass-cover cooling under the climatic conditions of Tabuk City, Saudi Arabia. Experiments were conducted at a constant basin−water depth of 0.50cm using PW loadings of 25%, 50%, and 100wt.% relative to the basin−water mass. Glass−cover cooling was investigated for the conventional still and in combination with 50wt.% PW. A transient heat−and mass−transfer model was also developed to predict temperatures and hourly freshwater productivity. The results showed that 50wt.% PW achieved the highest productivity among the PCM-only configurations (3.60L·m⁻²·day⁻¹), whereas 100wt.% PW reduced performance because of increased thermal inertia. Glass−cover cooling increased productivity from 2.49 to 3.41L·m⁻²·day⁻¹ and thermal efficiency from 46.01% to 54.24%. Combining 50wt.% PW with glass−cover cooling achieved the highest productivity of 5.10L·m⁻²·day⁻¹, approximately 106% higher than the conventional still. Experimental repeatability, spatial glass-temperature uncertainty, and statistical model assessments were performed to evaluate measurement reliability and model performance. These analyses demonstrated good experimental consistency, while the model reasonably captured the overall temperature and productivity trends. Overall, the findings highlight the importance of optimizing PCM loading and combining PW with glass-cover cooling to enhance solar-still performance.
The objective of this work is to develop a magnetic nanoadsorbent with easy separability and high efficiency for the heavy metal removal from aqueous media. For this purpose, Fe₃O₄@SiO₂@PSA–Schiff base is synthesized and applied as an efficient adsorbent for the removal of Cd²⁺ and Zn²⁺ ions. In this respect, Fe₃O₄ nanoparticles are synthesized and coated with a silica shell using Stöber method. To tackle the issue of low selectivity of the core-shell nanoparticle, the nanoparticles is functionalized with a new linker and selective synthesized complexing agent of polysalicylaldehyde (PSA). The structure of the synthesized nanoadsorbent is characterized using FT-IR, XRD, TGA, TEM and FE-SEM analyses. The adsorption performance of this nanoadsorbent is evaluated by investigating the effects of key parameters of extraction. The maximum adsorption capacity of Zn²⁺ and Cd²⁺ are obtained 107.9 and 100.0mg/g, respectively. Isotherm studies indicated that the adsorption process followed the Langmuir model suggesting the formation of a monolayer adsorption on the adsorbent surface. Kinetic studies revealed that the adsorption process is in agreement with the pseudo-second-order kinetic model. In conclusion, the synthesized magnetic nanoadsorbent is considered a promising candidate for the removal of heavy metal ions in water and wastewater treatment plant.
This study investigates the removal of the pharmaceutical contaminants atenolol and amoxicillin from wastewater using advanced oxidation processes (AOPs), specifically sonolysis and the electro-Fenton process. Furthermore, machine learning (ML) models were developed to predict and optimize the degradation efficiency of these treatment technologies under varying operational conditions. Four ML algorithms- artificial neural network (ANN), linear regression (LR), support vector machine (SVM), and gaussian process regression (GPR) were trained and validated using experimental data from our previous study. The results demonstrated that GPR was the superior predictive model across all scenarios, significantly outperforming the other algorithms. The GPR model achieved high predictive accuracy, with coefficients of determination (R2) of 0.999 for the sonolysis of both pharmaceuticals, 0.999 for the electro-Fenton treatment of atenolol, and 0.9854 for the electro-Fenton treatment of amoxicillin. To optimize the electro-Fenton process, the GPR model was integrated with a Genetic Algorithm (GA). This optimization framework successfully identified the optimal operational parameters for maximal degradation. For amoxicillin, the optimal hydrogen peroxide (H2O2) dosage was determined to be 3.5mM, achieving a predicted degradation of 91.45%. For atenolol, the optimal H2O2 dosage was 3.0mM, resulting in a 94.18% degradation. This study validates the use of a GPR-GA framework as a robust tool for accurately modeling and optimizing complex AOPs for pharmaceutical remediation.
In this study, a membrane-free electrodeionization (MFEDI) technology was demonstrated first time for the removal of hexavalent chromium (Cr(VI))-containing wastewater. Two packing configurations, namely, layered semimixed packing MFEDI (LSMP-MFEDI), and fully mixed packing MFEDI (FMP-MFEDI), were comprehensively investigated for Cr(VI)-containing wastewater treatment. During the treatment stage, the treatment capacity of FMP-MFEDI (132h) was twice that of LSMP-MFEDI (60h), with the effluent conductivity under 1 μS/cm. The enhancement is primarily due to the initial adsorption of dichromate(Cr2O72-) by quaternary amine groups, which promotes the co-adsorption activity of tertiary amines. More importantly, during the electroregeneration stage, FMP-MFEDI (229.7mg/L) exhibited higher regenerated average Cr(VI) concentrations than LSMP-MFEDI (170.5mg/L), along with a reduced energy consumption (0.19 kWh/g for FMP-MFEDI, 0.25 kWh/g for LSMP-MFEDI) and an increased water recovery rates (95.6% for FMP-MFEDI, 94.1% for LSMP-MFEDI). Such an enhanced electroregeneration performance in FMP-MFEDI was because that the strong-base and weak-base anion-exchange resins fully interact to form a “contact face”, which comprises both tertiary and quaternary amine functional groups. The tertiary groups promoted the release of Cr2O72- from the quaternary groups, thereby showing a synergistic effect in electro-releasing the adsorbed Cr2O72-. This provides abundant localized ion-depletion regions, consequently enhancing the electroregeneration property.
Solar-driven desalination represents a sustainable approach for freshwater production and constitutes an important building block for future zero-liquid-discharge (ZLD) systems. In this study, a photovoltaic-powered vacuum-assisted solar desalination unit was experimentally and theoretically investigated as the principal water-recovery component of a proposed ZLD framework. The downstream crystallization and salt recovery units are presented conceptually to illustrate the overall process configuration and were not included in the present experimental validation. Year-long measurements of solar irradiance, ambient temperature, brine temperature, salinity, density, evaporation rate, freshwater production, and energy consumption were collected and compared with theoretical predictions. Good agreement was obtained between the experimental observations and the developed mathematical model. Maximum freshwater productivity was achieved during periods of high solar irradiance, with a peak production of approximately 20.4kgm⁻² day⁻¹. The photovoltaic-powered vacuum operation significantly enhanced evaporation while reducing dependence on external electrical energy. The results demonstrate the potential of the proposed solar desalination unit as an effective renewable-energy-driven water recovery technology that can be integrated into future ZLD systems incorporating downstream brine concentration and crystallization processes.
Microplastics (MPs) are emerging contaminants increasingly detected in drinking water systems worldwide. However, comparative information on their occurrence and removal in drinking water treatment plants using different source waters remains scarce. This study evaluated the occurrence, characteristics, and removal efficiency of MPs in two drinking water treatment systems in Iran: a conventional freshwater DWTP and a seawater reverse osmosis (SWRO) desalination plant. In the freshwater DWTP, MP concentrations decreased from 118 ± 28 MPs/m³ in raw water to 28± 11 MPs/m³ in treated water, corresponding to a 76% removal efficiency. Fragment-shaped MPs in the 100–500 μm size range, predominantly blue in color, were the most abundant particles, while polyethylene terephthalate (PET), polypropylene (PP), and polyvinyl chloride (PVC) were the dominant polymers. In the SWRO desalination plant, MP concentrations declined from 140 ± 53 MPs/m³ in raw seawater to 17.6± 12 MPs/m³ after treatment, achieving an 87% removal efficiency. Fiber-shaped MPs measuring 500–1000 μm, mainly white and black, predominated, with polyethylene (PE) and PP identified as the most abundant polymers. The estimated daily intake ranged from 0.0008 to 0.006 items/kg/day. These findings provide practical insights into the occurrence, characteristics, and fate of MPs in freshwater and desalination-based water systems.
Access to safe drinking water remains a major public health challenge, particularly in developing countries. In this study, the efficiency of the electro-disinfection process for the removal of Escherichia coli and Bacillus subtilis from drinking water was systematically investigated. Batch experiments were conducted using aluminum anodes and stainless-steel cathodes in a monopolar parallel configuration. The results indicated that the optimum conditions were achieved at neutral pH (7.0), a current density of 2.5mA/cm², an IED of 2.0cm, and a contact time of 30–60min. Under these conditions, removal efficiencies of 100% and 99.6% were obtained for E. coli and B. subtilis, respectively. Kinetic analysis showed that the inactivation of E. coli followed an apparent first-order model (k = 0.0848min-1), whereas B. subtilis exhibited more complex behavior due to its greater physiological resistance compared with E. coli. The specific electrical energy consumption was calculated as 0.30666 kWh/m³, indicating relatively low specific electrical energy consumption under the investigated laboratory-scale conditions. Overall, these findings demonstrate the strong potential of electro-disinfection as a sustainable and safe alternative to conventional disinfection methods for drinking water treatment.
Desalination of high-salinity water remains a critical challenge for sustainable water management, as conventional membrane processes are inherently constrained by osmotic pressure limitations. In this study, graphitic carbon nitride (g-C3N4) nanosheets were incorporated into a polyamide (PA) selective layer via interfacial polymerization on a polyethersulfone (PES) ultrafiltration membrane for pervaporation (PV) desalination. Comprehensive characterization revealed that g-C3N4 incorporation increased surface hydrophilicity and modified the morphology and surface chemistry of the PA-selective layer. The optimized PA/g-C3N40.05@PES membrane exhibited an exceptional water flux of 74.83kgm−2 h−1 with a salt rejection exceeding 99.9% using a 3.5wt% NaCl feed at 70°C. Notably, the membrane demonstrated exceptional robustness under hypersaline conditions, sustaining a flux of 27kgm−2 h−1 and near-complete rejection even at 10wt% NaCl, a domain where conventional pressure-driven processes face severe osmotic limitations. Furthermore, the membrane exhibited improved resistance to fouling, with minimal performance degradation after exposure to humic acid foulant and stable long-term operation. Compared to conventional PA membranes and previously reported g-C3N4-based systems, the developed membrane demonstrates superior performance. This work highlights the potential of integrating g-C3N4 into PA matrices and demonstrates that PV is a highly promising strategy for efficient desalination of high-salinity water.
A green analytical method was developed for the simultaneous, rather than sequential, determination of Ni and Co using magnetic cellulose as a sorbent for preconcentration, coupled to high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) via a segmented flow injection device. Magnetic cellulose, synthesized by coprecipitation of iron oxide, proved to be an efficient, biodegradable sorbent for rapid metal uptake, providing preconcentration factors of 27.0 for Ni and 28.2 for Co under optimized conditions. Isotherm modeling and pH-dependent sorption behavior support an electrostatic ion-exchange mechanism governed by the oxygenated functional groups of cellulose, thereby enabling efficient and reversible metal recovery. Coupling magnetic cellulose microextraction with the flow injection system minimized sample dispersion, enhancing signal stability and enabling low characteristic concentrations (Ni 0.78µgL⁻¹ and Co 1.36µgL⁻¹), high extraction efficiency (>92%), high precision (RSD < 4.3%), and low detection limits (0.3µgL⁻¹ for Ni and 1.9µgL⁻¹ for Co). Recoveries of 96–103% in fortified real water samples confirmed its applicability under realistic conditions. The green metrics assessment (AGREE, AGREEprep, BAGI) further confirmed the environmental compatibility, practicality, and sustainability. Overall, this work introduces a novel, eco-friendly, robust, and sensitive strategy for the reliable simultaneous monitoring of Ni and Co in environmental water samples.
In this research work, synthesis and utilization of ZrO₂-Pistacia palaestina leaf (PPL) bio-composite for efficient removal of the Thionine (TH) dye from water have been discussed. Synthesis of bio-composite has been performed via eco-friendly method involving the use of PPL extract for reduction and stabilization of the composite. The characterization of the bio-composite has been made with the help of techniques like FTIR, SEM, XRD, and TEM, and the results of the analysis showed the synthesis of the bio-composite and also adsorption of the TH dye on it. Adsorption studies have shown that factors like adsorbent amount, pH, dye concentration, and temperature play crucial role in the performance of the adsorption capacity. In addition to this, Density Functional Theory (DFT) has been used to analyze the molecular stability and reactivity of the dye. Results of DFT study show that the dye has low ΔEgap value i.e., 1.599eV and therefore it possesses high chemical reactivity.
Synthetic dyes discharged from textile and related industries pose a major water-quality threat due to their chemical stability, structural complexity, and resistance to conventional treatment. This review critically evaluates polymer nanocomposite adsorbents for dye removal, focusing on polymer-matrix chemistry, nanofiller properties, fabrication, dispersion, surface modification, porosity, and adsorption mechanisms. Emphasis is placed on the interplay among polymer–nanofiller interactions, surface chemistry, pore accessibility, dye structure/charge, and solution conditions. Beyond maximum adsorption capacity (Qmax), performance is assessed through pH, contact time, temperature, kinetics, isotherms, regeneration, structural stability, nanofiller leaching, and water-matrix complexity. Azo dyes are emphasized as the dominant class, while methylene blue and malachite green serve as non-azo benchmark adsorbates; cross-linked polymers are used as reference materials to isolate nanofiller effects from those of the polymer matrix. The review highlights the persistent gap between laboratory-scale results and practical wastewater treatment, proposing a research roadmap centered on standardized reporting, authentic wastewater testing, repeated regeneration cycles, leaching assessment, continuous-flow validation, and preliminary cost/life-cycle evaluation. Overall, key factors governing adsorption are identified, and the evidence still required to establish real-world treatment potential and sustainability is defined.
This study reports treatment of pharmaceutical wastewaters via persulfate (PS) activation in a thin-layer flow photo-reactor exposed to standard solar light irradiation. The wastewater contained oxytetracycline, penicillin G, amoxicillin and erythrosine B drugs along with tartrazine and rhodamine B edible dyes. Under the established operating conditions of PS concentration of 223mg/L and circumneutral pH of 6.8, significant COD and TOC removals were achieved after 60min reaction. Adding only 1.5mg/L of ferrous ion, brought about 83.6 and 67.5% removals, respectively. Meanwhile, BOD5 removal was 84.7%, the BOD5/COD ratio reached to 0.74, and the turbidity removal was 62.9%. The ultimate COD was interestingly below the allowed limit of 100mg O2/L. The performance of the investigated homogeneous processes was appeared in the order of Solar/PS/ > Solar/PS >> PS/ > Solar/ > Solar, and preference was also revealed in comparison with various solar driven photochemical processes. Furthermore, the intermediates were identified through LC-MS analysis and the toxicity of the treated wastewater was evaluated via antibiogram test and quantitative structure activity relationship (QSAR) method, indicating substantial decrease in the antibacterial activity and low aquatic toxicity. Accordingly, based on different criteria, reusing of the treated wastewater for irrigation purpose was feasible.
Fluoride concentrations in groundwater above the WHO drinking-water guideline of 1.5mg/L cause irreversible dental and skeletal fluorosis, affecting an estimated 66million people in India. Low-cost defluoridation materials are urgently needed where membrane-based technologies are economically unviable. In this study, raw iron-rich laterite from Mancheswar, Odisha, is evaluated as a low-cost, zero-preparation fluoride adsorbent. SEM-EDS, XRD, FTIR and BET (24.6 m²/g) characterisation revealed a porous surface dominated by hematite, goethite, kaolinite and quartz, bearing Fe-OH and Al-OH surface hydroxyls. Batch experiments examined particle size (75–425µm), dose (0.5–10g/L), C₀ (0.5–10mg/L), pH (2–9), contact time (5–180min) and temperature (293–313K). At pH 6.5–7, a 2g/L dose and 100min, the 75µm fraction reduced 10mg/L fluoride to 0.7mg/L (93% removal). Equilibrium data fitted the Freundlich isotherm best (R² ≈ 0.99), indicating a heterogeneous surface; the Langmuir model, which does not best describe the data, gave a Langmuir-derived monolayer capacity of 0.201mg/g (300µm fraction), reported for comparison only. Pseudo-second-order kinetics (R² = 0.9999) describe the uptake rate, and thermodynamic analysis shows the adsorption to be spontaneous, endothermic and entropy-driven (ΔG° = −6.85 to −8.62kJ/mol; ΔH° = +19.03 ± 1.7kJ/mol; ΔS° = +88.3 ± 5.6J/(mol·K), 95% confidence interval from a three-temperature regression), confirmed by XPS surface speciation.
