Search Results (857)

The existence of dissolved organic matter (DOM) in aquatic environments presents significant challenges to both the environment and public health. This study examines the adsorption efficacy of six organic adsorbents, such as three commercial (coconut shells [CS], palm kernel shells [PKS], and graphite [GR]) and three waste-based materials (plantain peels [PP], water hyacinth leaves [WHL], and corn cobs [CC]) for DOM removal. The waste-derived adsorbents were prepared using thermal and chemical activation techniques, while the commercial adsorbents were used in their standard forms. Adsorption experiments were conducted and analyzed using both kinetic and isotherm models to evaluate removal efficiency and underlying mechanisms. Kinetic modeling revealed that CS, PP, CC, and GR followed pseudo-second-order kinetics, PKS conformed to pseudo-first-order kinetics, and WHL exhibited intra-particle diffusion dominance. The Freundlich isotherm model effectively characterizes the adsorption equilibrium for every material, indicating the multilayer adsorption and heterogeneity of the adsorbent surfaces. Among all tested materials, GR showed the highest DOM removal efficiency (up to 96%) and excellent thermal stability, making it the most effective adsorbent overall. WHL also showed competitive performance, while CS emerged as the most economically viable option despite having slightly lower removal efficiency. Surface area alone does not guarantee adsorption efficiency. Pore accessibility (governed by size/distribution) and surface chemistry (functional group diversity) are equally critical. The findings suggest that both commercial and waste-derived adsorbents hold promise for sustainable and cost-effective water treatment applications. Integrating such materials could enhance the circular economy and offer scalable solutions for addressing water quality issues in developing regions. Full article

The observed increase in the diversity and level of pollutant content in the water environment forces the development of more effective technologies for their removal. Using nanomaterials in water and wastewater treatment offers numerous opportunities to remove organic and inorganic contaminants that are hardly removable in conventional processes. In this group, carbon-based nanomaterials, mainly carbon nanotubes (CNTs), graphene (Gr), and graphene oxide (GO), are very popular. This review aims to present the directions and diversity of applications of carbon-based nanomaterials (CNMs) in water and wastewater technology, as well as the challenges and environmental dangers that new solutions entail. Authors also present the results of the research on the changes in properties of GO produced in the laboratory as water suspension and a freeze-dried product over time. The results confirm the significant influence of the form of graphene oxide and its storage time on the structural properties, hydrophilicity, and stability of GO. Therefore, they should be considered when selecting an adsorbent or reaction catalyst in environmental applications for developing new greener and sustainable methods of treatment and purification, which use fewer reagents and release safer products. Full article

Bambara groundnut (Vigna subterranea), a vital yet underutilized African legume, significantly boosts food security due to its nutritional value and adaptability to harsh climates and soils. However, its processing yields substantial waste like husks, shells, and haulms, which are often carelessly discarded, causing environmental damage. This paper highlights the urgent need to valorize these waste streams to unlock sustainable growth and economic development. Given their lignocellulosic composition, Bambara groundnut residues are ideal for generating biogas and bioethanol. Beyond energy, these wastes can be transformed into various bio-based products, including adsorbents for heavy metal removal, activated carbon for water purification, and bioplastics. Their inherent nutritional content also allows for the extraction of valuable components like dietary fiber, protein concentrates, and phenolic compounds for food products or animal feed. The nutrient-rich organic matter can also be composted into fertilizer, improving soil fertility. These valorization strategies offer multiple benefits, such as reduced waste, less environmental contamination, and lower greenhouse gas emissions, alongside new revenue streams for agricultural producers. This integrated approach aligns perfectly with circular economy principles, promoting resource efficiency and maximizing agricultural utility. Despite challenges like anti-nutritional factors and processing costs, strategic investments in technology, infrastructure, and supportive policies can unlock Bambara groundnut’s potential for sustainable innovation, job creation, and enhanced food system resilience across Africa and globally. Ultimately, valorizing Bambara groundnut waste presents a transformative opportunity for sustainable growth and improved food systems, particularly within African agriculture. Full article

Heavy metals represent long-lasting contaminants that pose significant risks to both human health and ecosystem integrity. Originating from both natural and anthropogenic activities, they bioaccumulate in organisms through the food web, leading to widespread and long-lasting contamination. Industrialization, agriculture, and urbanization have exacerbated soil and water contamination through activities such as mining, industrial production, and wastewater use. In response to this challenge, biochar produced from waste materials such as sewage sludge has emerged as a promising remediation strategy, offering a cost-effective and sustainable means to immobilize heavy metals and reduce their bioavailability in contaminated environments. Here we explore the potential of phosphate-enriched biochar, derived from sewage sludge, to adsorb and stabilize heavy metals in polluted soils. Sewage sludge was pyrolyzed at various temperatures to produce biochar. A soil incubation experiment was conducted by adding phosphate-amended biochar to contaminated soil and maintaining it for one month. Heavy metals were extracted using a CaCl₂ extraction method and analyzed using atomic absorption spectrophotometry. Results demonstrated that phosphate amendment significantly enhanced the biochar’s capacity to immobilize heavy metals. Amending soils with 2.5 wt% phosphate-enriched sewage sludge biochar led to reductions in bioavailable Cd (by 65–82%), Zn (40–75%), and Pb (52–88%) across varying pyrolysis temperatures. Specifically, phosphate-amended biochar reduced the mobility of Cd and Zn more effectively than unamended biochar, with a significant decrease in their concentrations in soil extracts. For Cu and Pb, the effectiveness varied with pyrolysis temperature and phosphate amendment, highlighting the importance of optimization for specific metal contaminants. Biochar generated from elevated pyrolysis temperatures (500 °C) showed an increase in ash content and pH, which improved their ability to retain heavy metals and limit their mobility. These findings suggest that phosphate-amended biochar reduces heavy metal bioavailability, minimizing their entry into the food chain. This supports a sustainable approach for managing hazardous waste and remediating contaminated soils, safeguarding ecosystem health, and mitigating public health risks. Full article

This study explores the enhancement of fluoride adsorption using biochar derived from the brown macroalga Sargassum polycystum, which was treated with iron oxide (Fe₃O₄). The macroalgal biomass underwent pyrolysis at 400 °C, followed by Fe₃O₄ impregnation, to improve surface functionality and create active sites for fluoride ion binding. Various factors affecting fluoride removal were systematically examined. A maximum fluoride removal effectiveness of 90.2% was attained under ideal circumstances (pH 2, 60 mg adsorbent dose, 30 mg/L fluoride concentration, and 150 min contact duration). Adsorption isotherm analysis showed that the Langmuir model provided a better fit (R² = 0.998) than the Freundlich model (R² = 0.941), with a maximum adsorption capacity (qₘ) of 3.41 mg/g, indicating monolayer adsorption on a homogeneous surface. Kinetic modeling revealed that the pseudo-second-order model best described the adsorption process (R² = 0.9943), suggesting chemisorption as the dominant mechanism, while the intraparticle diffusion model also showed a good fit (R² = 0.9524), implying its role in the rate-limiting step. Surface complexation, facilitated by the enhanced surface area and porosity of the iron-modified biochar, was identified as the primary mechanism of fluoride ion interaction. This study highlights the potential of Fe₃O₄-modified macroalgal biochar as an effective and sustainable solution for fluoride remediation in contaminated water sources. Full article

This study explores the sustainable extraction and application of natural dyes from figs (Ficus carica) and Eucalyptus leaves using an aqueous alkaline medium. The dyeing process was optimized for cotton fabric using the exhaust-dyeing method. Fabrics dyed with Ficus carica extract and its blend with Eucalyptus exhibited enhanced color strength, excellent crocking fastness (rated 4–5), and good washing fastness (rated 3–4 on the gray scale). The use of Aloe barbadensis Miller as a bio-mordant significantly improved dye fixation, resulting in deeper, earthy shades, such as green, yellow–green, and yellowish brown. The highest K/S value (5.85) was recorded in samples treated with a mordant, sodium chloride (NaCl), and the combined dye extracts, indicating a synergistic effect among the components. Mosquito repellency tests revealed that treated fabrics exhibited up to 70% repellency, compared to just 20% in undyed samples. Antibacterial testing against E. coli showed that dyed fabrics achieved over 80% bacterial reduction after 24 h, indicating promising antimicrobial functionality. Air permeability slightly decreased post-dyeing due to the potential shrinkage in cotton fabrics. Furthermore, adsorption studies showed a removal efficiency of 57% for Ficus carica dye on graphene oxide (GO) under ultrasonication. These findings confirm the potential of GO as an effective adsorbent material for treating wastewater from natural textile dyes. Overall, the study highlights the environmental safety, functional performance, and multifunctional advantages of plant-based dyeing systems in sustainable textile applications. Full article

This study investigates the adsorption performance of activated carbon (AC) derived from food and agricultural waste, specifically coffee grounds, coffee skin, bamboo, and palm leaves, for the removal of two antibiotics: amoxicillin (AMX) and sulfamethoxazole (SMX). The ACs were synthesized via KOH and ZnCl₂ chemical activation and characterized through BET surface area analysis, thermal stability, electrical conductivity, SEM, EDS, and FTIR. Among all samples, bamboo-derived AC (B-AC) exhibited superior properties, such as the highest surface area (860 m²/g), thermal stability (855 °C), conductivity (0.063 S/cm), and adsorption capacities (292.6 mg/g for AMX and 195.7 mg/g for SMX). SEM and EDS analyses confirmed successful antibiotic adsorption with morphological and elemental changes, while FTIR spectra indicated interaction with surface functional groups. Adsorption data were best described by the Langmuir and Dubinin–Radushkevich isotherm models, suggesting a monolayer physical adsorption process dominated by micropore filling (E < 8 kJ/mol). In contrast, BET and Flory–Huggins models exhibited poor fit, confirming the absence of multilayer or partition-based adsorption mechanisms. Kinetic modeling showed that AMX followed a pseudo-second-order model, while SMX exhibited a more complex adsorption behavior. Thermodynamic studies confirmed that both processes were spontaneous, with AMX adsorption being endothermic and entropy-driven and SMX being exothermic but favorable. These findings demonstrate the high potential of B-AC as a low-cost, eco-friendly, and efficient adsorbent for pharmaceutical removal from water, supporting circular economy and sustainability goals. Full article

This study evaluates the structural properties and adsorption capacities of four bio-based adsorbents, sawdust (SD), straw (ST), chicken feathers (CFs), and shrimp shells (SSs), for chemical oxygen demand (COD) removal from olive mill wastewater (OMW). Response Surface Methodology (RSM) with a Box–Behnken Design (BBD) was applied to optimize the operational parameters, resulting in maximum COD uptake capacities of 450 mg/g (SD), 575 mg/g (ST), 700 mg/g (CFs), and 750 mg/g (SSs). Among these materials, SSs exhibited the highest COD removal efficiency of 85% under optimal conditions (pH 8, 20 g/L, 30 °C, 5 h, 111 rpm). A mixture design approach was then used to explore the synergistic effects of combining lignocellulosic (SD and ST), chitin-based (SSs), and keratin-based (CFs) adsorbents. The optimized blend (SD 10%, ST 28.9%, SS 38.3%, and CF 22.6%) achieved a COD removal efficiency of 82%, demonstrating the advantage of using mixed biopolymer systems over individual adsorbents. Adsorption mechanisms were investigated through isotherm models (Langmuir, Freundlich, Temkin, and Redlich–Peterson) and kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion). Lignocellulosic adsorbents predominantly followed physisorption mechanisms, while chitin- and keratin-rich materials exhibited a combination of physisorption and chemisorption. Thermodynamic analysis confirmed the spontaneous nature of the adsorption process, with SSs showing the most favorable Gibbs free energy (ΔG = −21.29 kJ/mol). A proposed mechanism for the adsorption of organic compounds onto the bio-adsorbents involves hydrogen bonding, electrostatic interactions, π–π interactions, n–π stacking interactions, hydrophobic interactions, and van der Waals forces. These findings highlight the potential of biopolymer-based adsorbents and their optimized combinations as cost-effective and sustainable solutions for OMW treatment. Full article

In the present research, a novel magnetic adsorbent was developed via the sol–gel method by coating CuFe₂O₄ nanoparticles on biochar sourced from brewed tea waste. The synthesized adsorbent was utilized for the removal of Ni(II) ions from aqueous media. The adsorption efficiency of Ni(II) ions was assessed under crucial experimental conditions such as initial solution pH, contact time, adsorbent dosage, and initial Ni(II) concentration. The adsorbent exhibited rapid adsorption kinetics, achieving equilibrium in approximately 15 min, and maintained high efficiency across a wide pH range. Adsorption experiments were conducted for Ni(II) solutions at their natural pH (5.6) to minimize chemical usage and enhance process simplicity. An impressive maximum adsorption capacity of 232.6 mg g⁻¹ was recorded, outperforming many previously reported adsorbents. Furthermore, desorption studies demonstrated nearly 100% recovery of Ni(II) ions using 1.0 M HCl solution, indicating excellent regeneration potential of the adsorbent. Additionally, the prediction performance of an artificial neural network (ANN) model was evaluated to predict Ni(II) removal efficiency based on experimental variables, showing strong agreement with experimental data. Isotherm and kinetic models were also applied to the data to estimate the adsorption mechanisms. These findings demonstrate the promise of CuFe₂O₄-modified tea waste biochar for sustainable water treatment applications. Full article

Soil co-contamination with antimony (Sb) and arsenic (As) presents significant ecological and human health risks, demanding effective stabilization solutions. This study evaluated iron–manganese-modified hydrochar (FMHC) for synergistic Sb-As stabilization in contaminated smelter soils. Through 60-day natural aging and 30 accelerated aging cycles, we assessed stabilization performance using toxicity leaching tests (acid/water/TCLP), bioavailable fraction analysis, bioaccessibility assessment, and Wenzel sequential extraction. The key findings reveal that FMHC (5 wt%) achieves durable stabilization: (1) leaching concentrations remained stable post-aging (Sb: 0.3–4.5 mg·L⁻¹, >70% stabilization; As: <0.4 mg·L⁻¹, >94% stabilization); (2) bioavailable fractions showed maximum reductions of 64% (Sb) and 53% (As), though with some fluctuation; and (3) bioaccessible As was consistently reduced (55–77%), while Sb exhibited greater variability (maximum 58% reduction). Speciation analysis revealed similar stabilization pathways: Sb stabilization resulted from decreased non-specifically and specifically adsorbed fractions, while As stabilization involved the reduction in non-specifically/specifically adsorbed and amorphous to poorly crystalline Fe/Al hydrous oxide-bound fractions. These transformation mechanisms explain FMHC’s superior performance in converting labile Sb/As into stable forms, offering a sustainable solution for the green remediation of Sb-As co-contaminated soils in mining areas. Full article

Surface functionalization is a key enabler that imparts solid materials with excellent chemoselectivity. With this aim, halloysite and sepiolite clay particles were functionalized with carboxyethylsilanetriol sodium salt (CES) and 3-aminopropyltriethoxysilane (APTES), affording carboxy-terminated and amino-terminated clay, respectively. In the case of halloysite, the grafting occurs at Al-OH groups of the lumen surface (tube inner surface) and Al-OH and Si-OH groups at the edges and external surface defects of the nanotubes. For sepiolite, silanol groups located on the edges of the structural channels were at the origin of a chemical reaction between this fibrous clay and the terminal alkoxysilane. The resulting modified clays were examined for removal of Congo red (CR) and malachite green (MG) as anionic and cationic dyes, respectively. Clay bearing only carboxylic groups display more affinity towards cationic dye (MG), recording 926 mg·g⁻¹ and 387 mg·g⁻¹ for HNT-CES and SEP-CES, respectively, while amino-functionalized clays show very high adsorption for anionic dye (CR), reaching 1232 and 1228 mg·g⁻¹ for HNT-APTES and SEP-APTES, respectively. Simultaneous grafting of the two silyl coupling reagents was also attempted through one-pot and sequential grafting method, with the latter being more appropriate to access amphoteric clay featuring both carboxylic and amino groups. The behavior of the bifunctional adsorbents was investigated with respect to pristine and monofunctional clay. The obtained results provide insights to fulfill the requirement for handling complex water effluent containing both anionic and cationic pollutants, towards more sustainable development. Full article

This study focuses on the removal of arsenic (As) from contaminated water originating from an abandoned mercury mine landfill. To obtain results that more accurately reflect the material’s behavior under real-world conditions, tests were conducted starting with agitation, followed by column tests, and subsequently channel tests. The results demonstrated high efficacy of industrial waste materials (FA, HA, and EA) in adsorbing As, with a significant reduction of this contaminant in the leachates. Practical applications of this methodology include its potential use in large-scale remediation projects, improving water quality in mining-affected areas, and contributing to sustainable waste management practices. Full article

This study developed a new magnetic adsorbent from waste coconut shells using high-temperature carbonization, EDTA-2Na chelation, and Fe₃O₄ magnetic loading. Response surface methodology optimized the preparation conditions to a mass ratio of activated carbon: EDTA-2Na:Fe₃O₄ = 2:0.6:0.2. Characterization (SEM, XRD, FT-IR, and EDS) showed that EDTA-2Na increased the surface carboxyl and amino group density, while Fe₃O₄ loading (Fe concentration 6.83%) provided superior magnetic separation performance. The optimal adsorption conditions of Cu²⁺ by EDTA-2Na-Fe₃O₄-activated carbon composite material are as follows: when pH = 5.0 and the initial concentration is 180 mg/L, the equilibrium adsorption capacity reaches 174.96 mg/g, and the removal rate reaches 97.2%. The optimal adsorption conditions for Pb²⁺ are as follows: when pH = 6.0 and the initial concentration is 160 mg/L, the equilibrium adsorption capacity reaches 157.60 mg/g, and the removal rate reaches 98.5%. The optimal adsorption conditions for Cd²⁺ are pH = 8.0 and an initial concentration of 20 mg/L. The equilibrium adsorption capacity reaches 18.76 mg/g, and the removal rate reaches 93.8%. The adsorption followed the pseudo-second-order kinetics (R² > 0.95) and Langmuir/Freundlich isotherm models, indicating chemisorption dominance. Desorption experiments using 0.1 mol/L HCl and EDTA-2Na achieved efficient desorption (>85%), and the material retained over 80% of its adsorption capacity after five cycles. This cost-effective and sustainable adsorbent offers a promising solution for heavy metal wastewater treatment. Full article

Ammonia emissions in poultry houses are common and pose health concerns for animals and workers. However, effective control of these emissions with sustainable products is lacking. Therefore, we investigated if an agricultural byproduct, cottonseed hulls, could be recycled through pyrolysis and used to remove ammonia from air. In this study, the efficacy of ammonia removal was observed using cottonseed hull biomaterials pyrolyzed at seven different temperatures: 250, 300, 350, 400, 500, 600, and 700 °C. In this study, ammonia was passed through a column filled with pyrolyzed material, and ammonia in the filtered air was monitored. The results showed that materials pyrolyzed at intermediate temperatures of 350 and 400 °C were the most efficient at ammonia removal and were able to adsorb approximately 3.7 mg NH₃/g of material. Despite extensive characterization, ammonia adsorption could not be linked to intrinsic material properties. Evaluation of the materials showed that the carbon in the pyrolyzed materials would be stable over time should the spent material be used as a soil amendment. Full article

The presence of ciprofloxacin antibiotic in water is a threat to humans and aquatic life since antibiotics are currently regarded as emerging contaminants of major concern. This work reported the use of Nexar^TM film, a sulfonated pentablock copolymer, to effectively remove ciprofloxacin antibiotic from water in a sustainable approach. The removal efficiency of Nexar film was evaluated in aqueous or salty (NaCl 0.5 M) ciprofloxacin solutions as a function of contact time and the initial ciprofloxacin concentration. In the investigated conditions, the polymeric film totally removed ciprofloxacin in MilliQ solution while its removal efficiency in salty solution was approximately 73%. This lower value is due to the presence of Na⁺ ions that compete with antibiotic molecules for adsorption on active surface sites of the polymeric film. No further release of adsorbed antibiotic molecules occurred. The kinetic studies, conducted for ciprofloxacin adsorption on Nexar film in both MilliQ and salty solutions, revealed that the overall sorption process is controlled by the rate of surface reaction between ciprofloxacin molecules and active sites on Nexar surface. Furthermore, at equilibrium conditions, the isotherm model that best fits experimental parameters was not linear. This indicates that the competition between the solute and the solvent for binding sites on the adsorbent should be considered to describe adsorption processes in both MilliQ and salty solutions. Full article