Search Results (96)

This work focuses on the effectiveness of removing ammonium from real municipal wastewater using synthetic faujasite (FAU-type) and β (BEA-type) zeolites and a commercial β (BEA-type) sample. The results demonstrated that synthetic samples presented enhanced performance on ammonium removal in comparison with commercial zeolite due to higher Al content and larger specific surface area, promoting better accessibility to active adsorption sites of the adsorbents. Synthetic FAU-type and BEA-type zeolites achieved a maximum adsorption capacity of 28.87 and 12.62 mg·g⁻¹, respectively, outperforming commercial BEA-type zeolite (6.50 mg·g⁻¹). Adsorption assays, associated with kinetic studies and adsorption isotherms, were better fitted using the pseudo-second order model and the Langmuir model, respectively, suggesting that chemisorption, involving ion exchange, and monolayer formation at the zeolite surface, was the main mechanism involved in the NH₄⁺ adsorption process. After ammonium adsorption, the NH₄⁺-loaded zeolite samples were used to stimulate the growth of tomato seedlings; the results revealed a change in the biomass production for seedlings grown in vitro, especially when the BEA_C_NH₄ sample was employed, leading to a 15% increase in the fresh mass in comparison with the control sample. In contrast, the excess of ammonium adsorbed over the BEA_S_NH₄ and FAU_NH₄ samples probably caused a toxic effect on seedling growth. The elemental analysis results supported the hypothesis that the presence of NH₄⁺-loaded zeolite into the culture medium was important for the release of nitrogen. The obtained results show then that the investigated zeolites are promising both as efficient adsorbents to mitigate the environmental impact of ammonium-contaminated water bodies and as nitrogen-rich fertilizers. Full article

This study examined a strategy for effective reject water treatment involving hydrodynamic cavitation (HC) combined with subsequent adsorption using natural zeolites. Two experiments were conducted: The first involved the selection of optimal pre-treatment conditions of HC for biodegradability and to reduce the ammonium nitrogen and phosphate content. Three inlet pressures of 3, 5, and 7 bar and two types of cavitation inducers, i.e., multiple- and single-hole orifice plates, were evaluated. Adsorption experiments were conducted in batch mode using natural zeolite, and three doses of zeolite (50, 100, and 200 g/L) and six contact times (4–24 h) were examined. In the HC experiments, the application of 3 bar pressure, a single-hole cavitation inducer, and a cavitation time of 30 min resulted in the removal of ammonia nitrogen and phosphates amounting to 26.5 and 23%, respectively. In this case, 3.6-fold enhancement in the biodegradability index was also found. In the second experiment, the use of zeolite led to a decrease in the remaining content of both ammonia nitrogen and phosphates, improving the chemical oxygen demand-to-total nitrogen ratio. The highest removal efficacy was found for the highest zeolite dose of 200 g/L and the longest cavitation time of 24 h. Under these conditions, the ammonia nitrogen and phosphate removal rates were 70 and 94%, respectively. Full article

Implementing efficient strategies for the circular recovery and reuse of nutrients from wastewaters is mandatory to meet the Green Deal objectives and Sustainable Development Goals. In this context we investigated the use of zeolitic tuff (containing chabazite and phillipsite) in the selective recovery and reuse of N from various anaerobic liquid digestates in view of their implementation in farm-scale treatment plants. We tested the method on three livestock digestates and two municipal organic solid waste digestates. Adsorption isotherms and kinetics were assessed on each digestate, and a large set of parameters, including (i) contact time, (ii) initial NH₄⁺ concentration, (iii) presence of competing ions, (iv) total solids content, and (vi) separation methods (microfiltration and clarification), were considered in the experimental design. Our results showed that the adsorption mechanism can be explained by the Freundlich model (R² up to 0.97), indicating a multilayer and heterogeneous adsorption, while the kinetic of adsorption can be explained by the pseudo-second-order model, indicating chemical adsorption and ion exchange. The efficiency in the removal of NH₄⁺ was indirectly related to the K⁺ and total solids content of the digestate. Maximum NH₄⁺ removal exceeded 90% in MSW-derived digestates and 80% within 60 min in livestock-derived digestates at a 5% solid/liquid ratio. Thermodynamic parameters confirmed favorable and spontaneous adsorption (ΔG up to −7 kJ⋅mol⁻¹). Farm-scale projections estimate a nitrogen recovery potential of 1.2 to 16 kg N⋅day⁻¹, depending on digestate type and process conditions. These findings support the application of natural zeolitic tuffs as a low-cost, chemical-free solution for ammonium recovery, contributing to sustainable agriculture and circular economy objectives. Full article

Research on using biochar as an adsorbent of contaminants in aqueous matrices has gained significant relevance in recent years due to the surface chemistry and porous structure of biochar, which facilitate the retention of a wide range of pollutants. This study explores the adsorption performance of a novel biochar produced from agave bagasse—a readily available agro-industrial waste in Mexico—through low-temperature pyrolysis. The biochar was evaluated for its capacity to remove conventional water quality parameters (chemical oxygen demand (COD), nitrates (NO₃⁻), total nitrogen (TN), total phosphorus (TP), ammonium (NH₄⁺), turbidity, apparent color, and true color) from water samples collected from the polluted Bustillos Lagoon in Chihuahua, Mexico. Additionally, the removal of emerging pharmaceutical contaminants, specifically acetaminophen (Act) and diclofenac (Dfc), was assessed in synthetic aqueous solutions. Potentiometric titration analyses revealed a significant contribution of surface acidity in the adsorption of pharmaceutical derivatives, highlighting the relevance of functional groups retained during low-temperature pyrolysis. The biochar derived from agave bagasse (BBAF1) was tested in a fixed-bed column system and compared with two commercial activated carbons (CACCF2 and CVCF3). The BBAF1 biochar achieved average removal efficiencies ranging from 50% to 90% for all conventional parameters. In contrast, those of ACT and DFC were between 0.43 and 0.67 mg g⁻¹ (59–85%) and 0.34 and 0.62 mg g⁻¹ (37–79%), respectively, demonstrating their potential as an adsorbent material for improving water quality. This work supports the development of circular economic strategies by valorizing agricultural residues while offering an effective solution to environmental pollution challenges. Full article

Excess phosphorus (P) and nitrogen (N) in wastewater contribute to eutrophication, driving the need for low–cost and sustainable recovery technologies. This study presents a novel adsorbent synthesized from spent coffee grounds biochar (CB) chemically modified with Mn²⁺/Zn²⁺/Fe³⁺ (oxy)hydroxide nanoparticles (CB–M) for simultaneous removal of phosphate and ammonium. Batch adsorption experiments using both synthetic solution and municipal wastewater were conducted to evaluate the material’s adsorption performance and practical applicability. Kinetic, isotherm, thermodynamic, and sequential extraction analyses revealed that CB–M achieved maximum phosphate adsorption capacities ranging from 42.6 to 72.0 mg PO₄³⁻·g⁻¹ across temperatures of 20–33 °C, reducing effluent phosphate concentrations to below 0.01 mg·L⁻¹. Ammonium removal was moderate, with capacities ranging between 2.8 and 2.95 mg NH₄⁺·g⁻¹. Thermodynamic analysis indicated that phosphate adsorption was spontaneous and endothermic, dominated by inner–sphere complexation, while ammonium uptake occurred primarily through weaker, reversible ion exchange mechanisms. Sequential extraction showed over 70% of adsorbed phosphate was associated with Fe-Mn-Zn phases, indicating the potential for use as a slow–release fertilizer. The CB–M retained structural integrity and exhibited partial desorption, supporting its reusability for nutrient recovery. Compared to other biochars, CB–M demonstrated superior phosphate selectivity at a neutral–pH, avoided the use of hazardous metals, and transformed coffee waste into a multifunctional material for wastewater treatment and soil amendment. These findings underscore the potential of CB–M as a circular economy solution for nutrient recovery without introducing secondary contamination. Full article

N-nitroso dimethylamine (NDMA), a common nitrogen disinfection by-product and carcinogen, can be removed using rapid sand filtration (RSF) after coagulation; however, its removal mechanism has not been extensively studied. This study analyzed NDMA and the water pollutant parameter removal rate change tendency in the filtrates of simulated supernatants directly and after enhanced coagulation (EC) using composite PAC/PDMDAAC that mimics treated Yangtze River water separated into blank, single-component, and mixed multi-component (MMC) water systems containing NDMA and pollutants like diatomite (DTA), humic acid salt (HAs), dimethyl amine (DMA), and ammonium nitrate (NH₄NO₃). Meanwhile, a correlation analysis of removal rate changes and adsorption analysis using SEM (surface morphology), polar functional groups, and zeta potentials (surface charge) were performed to obtain mechanistic insights into NDMA removal via adsorption. The results revealed that removal rates gradually increased with an increasing volume of filtrates, and there were correlations for NDMA-HAs, NDMA-DMA, NDMA-DTA, and NDMA-NH₄NO₃. The highest NDMA removal rates in the blank system were 10.29% using RSF directly and 12.84% after enhanced coagulation, indicating improved efficiency with coagulation. However, single and mixed systems showed that NDMA removal rate changes were enhanced by water pollutants and coagulation functions. The NDMA removal mechanism was verified, and it was revealed that the level of NDMA adsorption on water pollutants varies based on microstructure, available polar functional groups, and surface charge interactions that are strengthened by coagulation functions for improving the affinity of NDMA and pollutants on the sand surface. These findings provide new insights into NDMA removal mechanisms via adsorption and highlight the role of water pollutants and enhanced coagulation in strengthening rapid sand filtration for NDMA removal. Full article

The introduction of nitrogen defects in graphitic carbon nitride (g-C₃N₄) has the important effect of improving its photocatalytic performance. This study employs a simple and environmentally friendly one-step pyrolysis method, successfully preparing g-C₃N₄ materials with adjustable N_3C defect concentrations through the calcination of a urea and ammonium acetate mixture. By introducing N_3C defects and adjusting the band structure, the conduction band of the g-C₃N₄ was shifted downward by 0.12 V, overcoming the traditional application limitations of N_3C defects and enabling an innovative transition from enhanced oxidation to enhanced reduction capabilities. This transition significantly enhanced the adsorption and activation of O₂. Characterization results showed that the introduction of N_3C defects increased the specific surface area from 44.07 m²/g to 87.08 m²/g, enriching reactive sites, while narrowing the bandgap to 2.41 eV enhanced visible light absorption capacity. The g-C₃N₄ with N_3C defects showed significantly enhanced photocatalytic activity, achieving peak performance of 54.8% for tetracycline (TC), approximately 1.5 times that of the original g-C₃N₄, with only a 5.4% (49.4%) decrease in photocatalytic efficiency after four cycles of testing. This study demonstrates that the introduction of N_3C defects significantly enhances the photocatalytic performance of g-C₃N₄, expanding its potential applications in environmental remediation. Full article

Rapid population and economic growth have increased the demand for depleting resources. Nitrogen (N) and phosphorus (P) are mineral elements that perform important functions in plants, but their extraction is not sustainable. In addition, these elements contribute significantly to the eutrophication of water bodies. The recovery of these nutrients from wastewater by adsorption techniques offers a promising solution. Previous studies have demonstrated the adsorption capabilities of materials such as zeolite for ammonium (NH₄⁺) and biochar for P. In addition, these materials can serve as a source of N and P for plants in a circular economy context. In this regard, this study aims to evaluate the recovery of N and P by the adsorption capacities of zeolite and biochar through a column test with treated wastewater. Two columns positioned in series, one filled with 2.7 kg of zeolite and the other with 397 g of biochar, were placed at the outlet of the full-scale sewage treatment plant of Marineo (Italy). The zeolite adsorbed 3.6 g of NH₄⁺ accumulated during the test with a rate of adsorption of 44% and adsorption of 1.33 mg g⁻¹ of NH₄⁺. The biochar adsorbed about 11 g of P accumulated during the test, with an adsorption percentage of 13% and an adsorption of 26.75 mg g⁻¹ of P. Despite some problems related to the effluent used during the test, the tested materials showed good adsorption properties. Full article

The conventional manganese carbonate preparation process faces challenges such as low resource utilization efficiency and difficulties in treating by-product Mg-containing ammonium sulfate solution. In this study, a two-stage leaching process was developed to efficiently extract Mn and Mg from the ore. NH₄HCO₃ was used as a precipitant to convert Mn²⁺ in the leachate to MnCO₃, achieving a Mn precipitation efficiency of 99.89%, and the resulting product contained 44.45% Mn, meeting the first-class product indicators of HG/T 4203-2011 (Chinese standard on manganese carbonate for industrial use). To further enhance resource utilization, a combined stripping–adsorption process was designed to treat the Mg-containing ammonium sulfate solution generated during the carbonization process. Subsequently, the economically valuable gypsum and magnesium oxide products were prepared. Additionally, 88.20% of the NH₃ in the solution was stripped and recycled to prepare NH₄HCO₃ and then used during carbonization. Finally, a purified solution free of ammonia nitrogen was obtained using 001×7 resin to dynamically adsorb the filtrates obtained during the stripping process, and the maximum adsorption capacity of resin for ammonia nitrogen was 51.14 mg/g. This process provides a novel approach to achieving clean production in the manganese carbonate production industry. Full article

The modification of the layered silicate with a structural type 2:1 montmorillonite by the cationic surfactant hexadecyltrimethylammonium bromide was carried out. The obtained organomontmorillonite was milled for 2–25 min in a high-energy planetary ball mill. The structural and physicochemical characteristics of the modified montmorillonite and the mechanochemically activated montmorillonite were investigated using various methods such as X-ray diffraction, thermal analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and determination of the specific surface area as well as the parameters of the porous structure by the low-temperature adsorption–desorption of nitrogen. The modification of montmorillonite with the quaternary ammonium salt led to a slowdown of deformation and subsequent amorphization of the montmorillonite structure during the high-energy milling. Mechanochemical activation of the modified montmorillonite increased its sorption capacity nine times, with the maximum uranium sorption achieved after mechanochemical treatment for 10 min. Full article

Biochars have emerged as a sustainable technology for converting waste into high-value, stable carbon products. Depending on its properties, biochar can retain various elements, including nitrogen (N) as ammonium (N-NH₄⁺). This study aimed to evaluate the rapid retention of N-NH₄⁺ in biochars produced from coffee husk (CH) and chicken manure (CM) at different pyrolysis temperatures (PTs) (300 °C, 400 °C, and 900 °C) and investigate the mechanisms involved. A rapid N-NH₄⁺ adsorption experiment was conducted, in which an NH₄Cl solution was passed through the biochars. The following analyses were performed: cation exchange capacity (CEC), surface area, pore volume and size, total N content, N retention, infrared analysis (ATR-FTIR), and leachate solution analysis, followed by chemical speciation using Visual MINTEQ software. The results indicated that different mechanisms were involved in rapid N-NH₄⁺ retention. In CH-derived biochars produced at 300 °C, N-NH₄⁺ retention occurred primarily through electrostatic interactions with negative charges (CEC), as confirmed by ATR-FTIR analysis. In CM-derived biochars produced at 400 °C, N-NH₄⁺ retention was mainly through the formation of struvite (NH₄MgPO₄·6H₂O), as confirmed by chemical speciation of leachate solution in Visual MINTEQ. In CH-derived biochars produced at 900 °C, N-NH₄⁺ ions were trapped in the pores of the charred matrix due to the increased biochar surface area, pore volume, and decreased pore size. The biochars studied proved effective in retaining N-NH₄⁺ through different mechanisms, suggesting that biochars can enhance rapid N retention and reduce N leaching, potentially serving as a source of N for crops. Full article

The detailed decomposition pathway of ammonium perchlorate (AP) is important for the design of solid propellants containing AP. In this paper, the possible decomposition reactions of AP upon nitrogen-doped graphene (N-Gr) as a catalyst are investigated via density functional theory. The reaction pathways of HClO₄ and NH₃ on the N-Gr surface are explored. The decomposition reaction path of the HClO₄ molecule on the N-Gr is HClO₄ → ${\mathrm{ClO}}_3^{-}$ → ${\mathrm{ClO}}_2^{-}$ → ClO⁻ → Cl⁻. The rate-determining step of the process is the Cl-O bond-breaking reaction of ${\mathrm{ClO}}_2^{-}$ anions, and the activation energy of the reaction is 0.849 eV. The oxidation of the N-Gr surface promotes the decomposition of both HClO₄ and NH₃. The OH groups produced during the decomposition process can promote the adsorption and decomposition of NH₃. This work provides new insights into the decomposition of AP on N-Gr at the molecular level. Full article

Riverbank filtration (RBF) technology has been applied and investigated worldwide for water supplies due to its sustainable water quantity guarantee and reliable quality improvement. In this work, the development history, application status, research progress, and technical overview of RBF are reviewed and summarized. RBF usually uses rivers, lakes, and groundwater as raw water, with a few cases using seawater. Nitrogen removal in RBF systems primarily occurs through key geochemical processes such as adsorption, denitrification, organic nitrogen mineralization, and dissimilatory nitrate reduction to ammonium (DNRA). For the attenuation of emerging contaminants in groundwater environments, key processes such as filtration, adsorption, and biotransformation play a crucial role, and microorganisms are essential. Based on a discussion of the advantages and disadvantages, we proposed the research prospects of RBF. To further enhance the water-supply safety and security with RBF, the mechanisms of surface water and groundwater interaction, pollutant removal, and blockage; the impact of capturing surface water on the stability of river ecosystems; and the coupling and synergistic effect of RBF with other water treatment technologies should be deeply investigated. Full article

NbVO_x mixed oxides were synthesized, characterized, and evaluated as catalysts for the extractive catalytic oxidative desulfurization (ECODS) of dibenzothiophene (DBT) using acetonitrile as a solvent. The mixed oxides were prepared using two different vanadium precursors: ammonium metavanadate and vanadium(IV)-oxy acetylacetonate. These precursors influenced the acidic/basic properties and the concentration of oxygen vacancies in the resulting catalysts. The texture and surface properties of the synthesized materials were analyzed using nitrogen adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy (UV-vis). Their catalytic activity was evaluated through the dehydration and dehydrogenation of 2-propanol and the ECODS of DBT. The mixed oxides synthesized with an excess of ammonium metavanadate (Nb:V = 1:2) demonstrated superior catalytic activity in removing DBT from the oil phase, achieving approximately 90% removal within 90 min at 60 °C. This enhanced activity is attributed to its higher acidity, greater concentration of oxygen vacancies, and the presence of vanadium peroxo ligands on its surface. Full article

The treatment of wastewater using microalgae is regarded as a green and potential technology. However, its engineering application has been largely hindered because of the limitation of microalgae separation and harvesting. Therefore, immobilization technology has been widely used to embed microalgae for wastewater treatment. In this paper, sodium alginate (SA) and polyvinyl alcohol (PVA) as the common immobilized carriers were used to immobilize ankistrodesmus falcatus for simulated slaughtering wastewater (SSW) treatment. The experimental results of the mass transfer and adsorption of immobilized carriers were found to show that the mass transfer of SA-SiO₂ gel balls (SS-GB) was better than PVA-SA gel balls (PS-GB) and that the adsorption of PS-GB was better than SS-GB. When immobilizing microalgae with the two kinds of carriers, it was found that SA-SiO₂ microalgal spheres (SS-MS) were better than PVA-SA microalgal spheres (PS-MS) for the maintenance of microalgal cell activity and that PS-MS were better than SS-MS for the resistance to biodegradation. This is because the carrier of PS-MS had a thick shell and dense structure, while the carrier of SS-MS had a thin shell and loose structure. The results of SSW treatment by PS-MS and SS-MS were found to show that the total phosphorus (TP) removal rates of PS-MS and SS-MS were 90.31% and 86.60%, respectively. This indicates that the TP removal effect of PS-MS was superior to that of SS-MS. The adsorption kinetics simulation showed that the adsorption of TP onto PS-GB was controlled by chemisorption and that the adsorption of TP onto SS-GB was controlled by physical adsorption. The chemical oxygen demand (COD) and ammonium nitrogen (NH₄⁺-N) removal of PS-MS were 9.30% and 10.70%, respectively, and the COD and NH₄⁺-N removal of SS-MS were 54.60% and 62.08%, respectively. This indicates that the COD and NH₄⁺-N removal effect of SS-MS were superior to PS-MS. This is the result of the combined action of the degradation by microalgal cells and adsorption by the carrier. Full article