Search Results (152)

The heavy metal contamination of soils is a global environmental challenge threatening water quality, food safety, and human health. Using a systematic literature review approach, this study aimed to assess the potential of bacterial strains to immobilize cadmium (Cd²⁺), lead (Pb²⁺), and copper (Cu²⁺) in contaminated soils. A total of 45 articles were analyzed, focusing on studies that reported heavy metal concentrations before and after bacterial treatment. The analysis revealed that bacterial genera such as Bacillus, Pseudomonas, and Enterobacter were most commonly used for the immobilization of these metals. Immobilization efficiencies ranged from 25% to over 98%, with higher efficiencies generally observed when microbial consortia or amendments (e.g., phosphate compounds and biochar) were applied. The main immobilization mechanisms included biosorption, bioprecipitation (such as carbonate-induced precipitation), bioaccumulation, and biomineralization, which convert mobile metal ions into more stable, less bioavailable forms. These findings highlight the promising role of microbial-assisted immobilization in mitigating heavy metal pollution and reducing ecological risks. Further laboratory and field studies are needed to optimize the use of these microbial strains under site-specific conditions to ensure effective and sustainable soil remediation practices. Full article

Industrial effluents pose a significant concern because they contain a variety of metals and metalloids that have detrimental effects on the environment. Conventional techniques are widely used in effluent treatment plants (ETPs) to remove metallic pollutants; however, they are less effective, are costly, and generate secondary toxic waste. Mycosorbent would be a sustainable and economical alternative to conventional techniques, as it offers numerous advantages. In this study, we shed light on the development of mycosorbent, which could be potentially applicable in the treatment of industrial effluent. In a competitive (i.e., multimetal system) optimisation study, mycosorbent AD2 exhibited a maximum biosorption capacity of 3.7 to 6.20 mg/g at pH 6.0, with an initial metal ion concentration of 25 mg/L, a contact time of 2 h, at 50 ± 2 °C, and a pH_PZC of 5.3. The metal-removal capacity increased up to 1.23-fold after optimisation. The thermodynamic parameters confirmed that the AD2 mycosorbent facilitated an endothermic, feasible, and spontaneous biosorption process. The FT-IR and SEM characterisation analysis confirmed the adsorption of metals on the surface of the mycosorbent from the aqueous system. This study demonstrated that mycosorbent could be an effective tool for combating metallic pollutants in various industrial effluents. Full article

The risk of contamination of the vital resource of water continues to increase and represents an urgent problem for modern society. Globalisation, industrialisation and technological progress have led to the need to treat more and more wastewater streams before they can be released into the environment. A high chemical and biochemical oxygen demand as well as the sum of dissolved and suspended organic and inorganic components are the main characteristics of highly contaminated wastewater. Research into environmentally friendly and sustainable technologies is becoming increasingly important in wastewater treatment. Bioremediation utilises the ability to restore the biogenic elements of the environment and is an environmentally friendly method for removing contaminants from the surrounding ecosystem. Forming microbial consortia that exhibit both excellent biosorption properties and a high resistance to toxic conditions is crucial for the biodegradation of complicated systems, such as highly contaminated wastewater. The development of systematic biological molecular tools can further improve the bioremediation process. By integrating innovative technologies with the already existing natural microbial capacity, it is possible to further improve the sustainability of biological treatments of wastewater streams while preserving the natural environment. Full article

This study investigates the adsorption and desorption efficiencies of Cu (II) and Cd (II) from industrial effluents using orange peel powder and a newly developed mixed adsorbent composed of equal parts of activated charcoal (AC) and bone charcoal (BC). The mixed adsorbent (AC + BC) exhibited significantly higher removal efficiencies for both copper and cadmium metal ions compared to orange peel powder. This can be attributed to the high surface area of AC and the negative surface charge of BC, resulting in a synergistic adsorption effect. Batch adsorption experiments were conducted in an orbital shaker at 150–180 rpm for 60 min, followed by thorough rinsing to remove any residual metal ions. The optimal pH for maximum adsorption of Cu (II) and Cd (II) was found to be 6. The effects of adsorbent dosage (ranging from 0.5 to 5 g/L) and contact time (ranging from 15 min to 4 h) on adsorption performance were systematically studied. Regeneration experiments using 0.2 M HCl demonstrated that the adsorption of Cu (II) and Cd (II) on the mixed adsorbent was highly reversible, achieving desorption efficiencies of 90% and 94%, respectively. Notably, Cd (II) consistently exhibited higher desorption rates across all tested dosages. These results confirm the potential of the proposed adsorbent and regeneration strategy for efficient and economical removal of heavy metals from industrial wastewater. Full article

The study examines the biosorption potential of Ulva intestinalis (UI) and calcium oxide-modified Ulva intestinalis (CaO-UI) for the environmentally favorable removal of cadmium (Cd²⁺), nickel (Ni²⁺), and lead (Pb²⁺) from aqueous solutions. This research addresses the critical need for sustainable water treatment solutions by developing a green-synthesized biosorbent that combines renewable biomass with enhanced adsorption properties. The adsorption properties of the biomass were improved by preparing calcium oxide (CaO) using Ulva intestinalis extract by green synthesis. Langmuir, Freundlich, and Temkin isotherms were employed to model the results of adsorption experiments that were conducted under a variety of conditions, such as contact time, biosorbent dose, and initial metal ion concentration. Langmuir (R² = 0.999) and Freundlich (R² = 0.999) models both provided an exceptionally well-fitted model for the adsorption isotherms, suggesting a hybrid mechanism that integrates monolayer chemisorption at CaO-active sites and multilayer adsorption on the heterogeneous algal matrix. Key findings demonstrate that the maximum adsorption capacity (qm) of CaO-UI was substantially higher than that of UI, with values of 571.21 mg/g for Cd²⁺, 665.51 mg/g for Ni²⁺, and 577.87 mg/g for Pb²⁺, respectively, in comparison to 432.47 mg/g, 335.75 mg/g, and 446.65 mg/g for UI. The adsorption process was dominated by pseudo-second-order (PSO) chemisorption, as evidenced by kinetic studies (R² = 0.949–0.993). CaO-UI exhibited substantially higher rate constants (k₂ = 9.00–10.15 mg/mg·min) than raw UI (k₂ = 4.72–5.71 mg/mg·min). The green synthesis of calcium oxide has resulted in an increase in surface area, porosity, and functional group density, which is responsible for the enhanced performance of CaO-UI. The adsorption efficacy of Pb²⁺ was the highest, followed by Cd²⁺ and Ni²⁺, which was indicative of the differences in metal ion affinity and hydration energy. These results underscore the potential of CaO-UI as a biosorbent that is both cost-effective and sustainable for the removal of heavy metals in wastewater treatment applications. Full article

This study investigates the biosorption of heavy metal ions (Pb, Fe, Cu, Cd, Zn, and Mn) from wastewater using the powdered biomass of Phragmites australis (common reed) under varying conditions, including temperature, pH, retention time, plant powder size, and biosorbent weight. The results showed that plant powder size significantly influenced the biosorption efficiency, with the 0.5 mm diameter powder yielding the highest removal rates for the heavy metal ions. The optimal temperature for biosorption was found to be between 30 and 50 °C, achieving up to 99.94% removal for Pb. The ideal pH for the biosorption of all metals was seven, and the best retention time for ion removal was 30 min, with a mean biosorption rate of 99.82% for Fe. A biosorbent weight of 10 g/L was also identified as the most effective for metal ion removal. Furthermore, two forms of P. australis, dry pieces and powdered biomass, were tested, with the powdered biomass exhibiting a superior biosorption performance. FTIR analysis revealed the involvement of carboxyl and hydroxyl functional groups in the biosorption process, while SEM imaging confirmed the surface interactions between metal ions and the plant material. The adsorption of heavy metals onto P. australis was effectively described by both Langmuir and Freundlich isotherm models, indicating a mix of monolayer coverage and heterogeneous interactions. The Langmuir model showed the highest adsorption capacities for Mn²⁺ (6.29 mg/g) and Cd²⁺ (5.10 mg/g), with strong affinities for Pb²⁺ (K_L = 0.0122 L/mg), Fe²⁺ (K_L = 0.0137 L/mg), and Cu²⁺ (K_L = 0.0130 L/mg). Similarly, the Freundlich model indicated favorable adsorption (n > 1) for all ions. Cu²⁺ and Fe²⁺ had the highest adsorption intensities (n = 2.06), with the strongest capacities being observed for Fe²⁺ (K_f = 0.231) and Cu²⁺ (K_f = 0.222). These findings confirm the high potential of P. australis as a sustainable and eco-friendly biosorbent. Full article

Molybdenum (Mo) is a critical industrial metal valued for its corrosion resistance and strength-enhancing properties. However, increasing demand necessitates more efficient and sustainable recovery methods. Bio-recovery of Mo by biosorption is a promising resolution, especially by the use of surface-engineered microbes that express metal binding proteins on its cell surface. This study investigates the potential of Saccharomyces cerevisiae strain ScBp6, which displays a molybdate-binding protein (ModE) on its cell surface, immobilized on porous materials. Our findings reveal that polyurethane sponges (PS) significantly outperform ceramic materials in yeast immobilization, entrapping 1.76 × 10⁷ cells per sponge compared to 1.70 × 10⁶ cells per ceramic cube. Furthermore, the yeast–PS complex demonstrated superior Mo adsorption, reaching 2.16 pg Mo per yeast cell under 10 ppm Mo conditions, comparable to free yeast cells (1.96 pg Mo per yeast cell). These results establish PS as an effective and scalable platform for Mo recovery, offering high biosorption efficiency, reusability, and potential for industrial wastewater treatment applications. Full article

Industrial hemp (Cannabis sativa L.) was investigated as a sustainable biosorbent for removing Congo Red (CR) and Remazol Brilliant Blue R (RBBR) from wastewater. The unmodified hemp biosorbent exhibited moderate but practically relevant sorption capacities (4.47 mg/g for CR; 2.44 mg/g for RBBR), outperforming several agricultural waste materials. Kinetic studies revealed rapid uptake, with CR following pseudo-first-order kinetics (t₁/₂ < 15 min) and RBBR fitting the Elovich model, indicating heterogeneous surface interactions. Equilibrium data showed CR adsorption was best described by the Temkin isotherm (R² = 0.983), while RBBR followed the Langmuir model (R² = 0.998), reflecting their distinct binding mechanisms. Thermodynamic analysis confirmed spontaneous (ΔG° < 0), exothermic (ΔH° ≈ −2 kJ/mol), and entropy-driven processes for both dyes. Molecular docking elucidated the structural basis for performance differences: CR’s stronger binding (−7.5 kcal/mol) involved weak noncovalent interaction arising from partial overlap between the π-electron cloud of an aromatic ring and σ-bonds C-C or C-H (π-σ stacking) and hydrogen bonds with cellulose, whereas RBBR’s weaker affinity (−5.4 kcal/mol) relied on weak intermolecular interaction between a hydrogen atom (from a C-H bond) and the π-electron system of an aromatic ring (C-H∙∙∙π interactions). This work establishes industrial hemp as an eco-friendly alternative for dye removal, combining renewable sourcing with multi-mechanism adsorption capabilities suitable for small-scale water treatment applications. Full article

The effects of acid and alkali pretreatments on the physicochemical and textural properties of Macrocystis pyrifera were evaluated to assess its potential for removing recalcitrant organic pollutants from aquatic systems. Untreated (UB), acid-pretreated (A_CPB), and alkali-pretreated (A_LPB) seaweed biomass were characterized using SEM, FTIR-ATR, N₂ adsorption–desorption, and potentiometric titrations. Adsorption isotherms and kinetic studies, using methylene blue (MB) as a model pollutant, were conducted to evaluate removal performance. All biosorbents exhibited Langmuir behavior, with maximum adsorption capacities of 333 mg g⁻¹ (UB), 189 mg g⁻¹ (A_CPB), and 526 mg g⁻¹ (A_LPB). FTIR-ATR and SEM analyses revealed that alkali pretreatment increased the abundance of hydroxyl, carboxylate, and sulfonated functional groups on the seaweed cell walls, along with greater porosity and surface roughness, resulting in enhanced MB adsorption. In contrast, acid pretreatment increased the exposure of carboxylic, amine, and amide functional groups, reducing the electrostatic interactions. The adsorption energy values further supported this, while the intra-particle diffusion model indicated a two-step process involving MB diffusion onto the seaweed surface, followed by diffusion into internal pores. These findings highlight the potential application of Macrocystis pyrifera-based biosorbents in the treatment of wastewater containing recalcitrant organic pollutants. Full article

At present, the amount of heavy metals in some aquifers exceeds the limits established by standards, especially in developing countries. Cadmium is present in high concentrations in aquifers; contact with cadmium can lead to some adverse health effects. Adsorption is one of the most efficient and low-cost methods currently used to separate heavy metals from water systems. In order to obtain a sustainable heavy metal adsorption system, abundant, low-cost, biodegradable, and easy-to-treat organic waste compounds were sought. Three biosorbents were chosen: orange, peanut, and banana peel, which, due to their functional groups, can attract the positive ions of metals and form a bond that allows them to be absorbed and separated from the aqueous solution. The presence of functional groups such as -OH, -CO, -COO⁻, and -N-H were found to be the main responsible for biosorption (FTIR). Square wave voltammetry was used to analyze the amount of cadmium in an aqueous solution. It was found that the systems with the best adsorption capacities were untreated peanut peel (284.2 mg/g), untreated orange peel (275.5 mg/g), and treated banana peel (229.21 mg/g). Treatment of the peels for cadmium uptake is not recommended. Full article

The rapid expansion of industrial and agricultural activities in recent years has significantly contributed to water pollution leading to a decline in water quality and the need for effective treatment and reuse strategies. Metal contamination in water bodies poses severe environmental and health risks, making the development of cost-effective and sustainable remediation methods essential. Among the various treatment approaches, biosorption using biological adsorbents has emerged as a promising alternative due to its low cost and high efficiency. However, while the adsorption mechanisms of single metals are well understood, the competitive interactions between multiple metal ions during the sorption process remain less explored. In this review, we analyze the competitive biosorption of metals in multi-metallic wastewater systems. Key factors influencing metal removal, such as pH, contact time, biosorbent dosage, and initial metal concentration, are discussed, along with the intrinsic properties of biosorbents and metal ions that affect sorption efficiency. Additionally, we highlight recent studies on agroforestry byproducts as effective biosorbents for metal removal, showcasing their potential for sustainable water treatment. Heavy metals pose significant risks even at low concentrations, necessitating robust regulations and advanced treatment technologies; biomass byproducts, as cost-effective biosorbents, can be optimized through pre-treatment, activation, pH and temperature control, and particle size reduction, while effectively managing competitive multi-metal adsorption remains crucial for industrial effluent treatment. Full article

This study aims to develop a novel use of baker’s yeast in biosorption as a sustainable metal recovery process for cost-effective and practical applications in recovering copper and zinc from waste gravity-thickened sludge generated at livestock wastewater treatment facilities. The supernatant of the acid-extracted product was separated from the residues through centrifugation. To ensure cost efficiency, the supernatant was treated with 2N acetic acid for 24 h, with the addition of hydrogen peroxide, and used for the biosorption experiments. The filtrated supernatant was adjusted to various pH values (4.5, 5.0, and 5.5) to explore the effects of acidity on the subsequent biosorption of extracted zinc and copper by baker’s yeast. A diluted molasses solution was added to the filtrate as a carbon source to support yeast growth during the 4 h biosorption experiments. The results revealed that the removal efficiency of zinc from the filtrate by baker’s yeast was 97.3%, while the removal efficiency for copper was about 48.8% at pH 5.5 with a reaction time of 4 h. In summary, this combined approach is expected to reduce and recycle heavy metals in livestock sludge. Acetic acid with hydrogen peroxide can extract copper and zinc from the sludge, and baker’s yeast can absorb both metals from the filtrate at pH 5.5 in a 4 h reaction time. This technological innovation has the potential to transform waste management practices in the livestock industry, contributing to resource recovery and environmental sustainability. Full article

The pressure on the environment from wastewater has been increasing in line with industrialization and urbanization, thus calling for better and eco-friendly solutions for wastewater treatment. Extremophilic microorganisms, which can grow in extreme conditions including high salinity, acidity, and temperature, can be applied in wastewater bioremediation. This review assesses the various functions of extremophiles, halophiles, thermophiles, alkaliphiles, and acidophiles in the treatment of organic and inorganic pollutants. They are capable of catabolizing a wide range of hazardous chemicals, such as polycyclic aromatic hydrocarbons, phenolic compounds, and heavy metals. Moreover, extremophilic microalgae, like Galdieria sulphuraria, have been effective in nutrient removal, biosorption of heavy metals, and pollutant conversion into valuable biomass. This dual-functioning, therefore, helps not only in wastewater treatment but also in the production of biofuel and biofertilizer, making the process cost-effective. The use of extremophiles in biofilm reactors improves pollutant removal, with less energy input. Extremophilic microorganisms can, therefore, be used to revolutionize wastewater management by providing green solutions to current treatment approaches. This review discusses the existing drawbacks of wastewater treatment along with the additional requirements needed to enhance the capability of bioremediation and potential future research. Full article

Copper contamination in coastal water environments poses a significant health risk, and traditional treatments for copper intoxication include gastric lavage, chelation, and hemodialysis. Recent research suggests that probiotics may help mitigate heavy metal toxicity by promoting biosorption in the intestinal tract. To explore this potential, we investigated the protective effects of Heyndrickxia coagulans (H. coagulans) against copper-induced toxicity in rats. After eight weeks of exposure, rats receiving both copper and H. coagulans exhibited significant improvements in renal function, lipid profiles, antioxidant enzyme activity, and histological markers compared to the copper-only group. However, liver function remained largely unchanged, suggesting a more pronounced protective effect on renal health. These findings highlight the potential of H. coagulans as a supportive intervention for mitigating the adverse effects of copper intoxication. Full article

Chitosan-based biosorbents are particularly valuable in environmental applications, such as wastewater treatment for contaminant removal. However, several challenges remain in optimizing their production and performance related to improving adsorption efficiency, stability, scalability, cost, and sustainable sourcing for large-scale applications. The removal of Methylene Blue (MB) and Orange 16 (O16) from aqueous solutions was studied using a biosorbent derived from the waste biomass of the brewing industry, specifically Saccharomyces pastorianus immobilized into chitosan. The biosorbent (obtained by a straightforward entrapment technique) was characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) to evaluate its structural properties. The biosorption behavior toward organic contaminants, specifically a cationic and an anionic dye, was investigated. Key operational factors that influenced the biosorbent’s efficiency were examined, including the initial dye concentration, dye type, pH of the aqueous solution, and the amount of biosorbent used. These factors were evaluated during the initial stage of the biosorption studies to assess their impact on the overall performance and effectiveness of the biosorbent in removing the dyes from aqueous solutions. Using this eco-friendly biosorbent, the biosorption capacities obtained using the Langmuir isotherm model were 212.77 mg/g in the case of MB dye and 285.71 mg/g in the case of O16 mg/g, and the results confirmed that the biosorption process is based on a physical mechanism as suggested by the energy values of the process, E, obtained using the DR model: the obtained values of 6.09 kJ/mol (MB dye) and 7.07 kJ/mol (O16 dye) suggest a process based on electrostatic interaction bonds. These results indicate that residual biomass of Saccharomyces pastorianus, as a byproduct of a biotechnological process, can be exploited as a biosorbent by immobilization in an organic matrix (chitosan) for the retention of polluting organic species from the aqueous environment present in aqueous solutions in moderate concentrations. Full article