Search Results (474)

This study investigates two novel algal biosorbents (Ulothrix sp. and Spirogyra sp.) from Djelfa, Algeria, for methylene blue (MB) removal from aqueous solutions. A comprehensive characterization, including scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS), Brunauer–Emmett–Teller (BET) analysis, porosity measurements, and Fourier-transform infrared spectroscopy (FTIR), revealed distinct physicochemical properties. Ulothrix exhibited a surface area of 5.35 m²/g with an average pore diameter of 32.77 nm, whereas Spirogyra showed values of 3.47 m²/g and 20.97 nm for the surface area and average pore diameter, respectively. Despite their modest surface areas, both algae demonstrated effective adsorption capacities (6.94 mg/g for Spirogyra vs. 6.38 mg/g for Ulothrix), with optimal doses of 0.01 g and 0.08 g (for 50 mL of MB solution), respectively. Kinetic analysis confirmed pseudo-second-order adsorption (R² > 0.97), indicating chemisorption dominance. Isotherm data best fit the Sips model (R² = 0.94), suggesting heterogeneous monolayer formation. Thermodynamic studies revealed an endothermic (ΔH° > 0), spontaneous (ΔG° < 0), yet favorable adsorption process, highlighting the potential of these naturally abundant algae as sustainable biosorbents for dye wastewater treatment. Full article

The exponential increase in electronic waste (e-waste) from end-of-life electrical and electronic equipment presents a growing environmental challenge. E-waste contains high concentrations of rare earth elements (REEs), which are classified as critical raw materials (CRMs). Their removal and recovery from contaminated systems not only mitigate pollution but also support resource sustainability within a circular economy framework. The present study proposed the use of hazelnut shells as a biosorbent to reduce water contamination and recover REEs. The sorption capabilities of this lignocellulosic material were assessed and optimized using the response surface methodology (RSM) combined with a Box–Behnken Design (three factors, three levels). Factors such as pH (4 to 8), salinity (0 to 30), and biosorbent dose (0.25 to 0.75 g/L) were evaluated in a complex mixture containing 9 REEs (Y, La, Ce, Pr, Nd, Eu, Gd, Tb and Dy; equimolar concentration of 1 µmol/L). Salinity was found to be the factor with greater significance for REEs sorption efficiency, followed by water pH and biosorbent dose. At a pH of 7, salinity of 0, biosorbent dose of 0.75 g/L, and a contact time of 48 h, optimal conditions were observed, achieving removals of 100% for Gd and Eu and between 81 and 99% for other REEs. Optimized conditions were also predicted to maximize the REEs concentration in the biosorbent, which allowed us to obtain values (total REEs content of 2.69 mg/g) higher than those in some ores. These results underscore the high potential of this agricultural waste with no relevant commercial value to improve water quality while providing an alternative source of elements of interest for reuse (circular economy). Full article

Aimed at developing an economical and efficient biosorbent for the adsorption and separation of rare earth ions, this study employed Spirulina dry powder biomass as a biosorbent to investigate its removal performance for Pr³⁺ in aqueous solutions. Experimental results demonstrated that under optimized conditions (pH = 5, adsorbent dosage = 2.0 g/L, initial Pr³⁺ concentration = 100 mg/L, and adsorption time = 60 min), the removal efficiency of Pr³⁺ reached 79.0%. FT-IR and XPS characterization confirmed the participation of various functional groups on the Spirulina surface in the adsorption process. When 0.1 mol/L HNO₃ was used as the desorption agent, the desorption rate of Pr³⁺ from Spirulina reached 91.7%, demonstrating excellent regeneration performance. At different temperatures (298–318 K), the adsorption data were fitted using Langmuir, Freundlich, Dubinin–Radushkevich, and Redlich–Peterson models. Among them, the Langmuir model (R² ranged from 0.993 to 0.999) provided the best fit, and the adsorption capacity of Spirulina for Pr³⁺ was in the range of 51.10 to 55.31 mg/g. Kinetic studies revealed that the pseudo-second-order model (R² = 0.999) best described the adsorption process, with a rate constant of 0.054 g/(mg·min) (R² was 0.999) at an initial Pr³⁺ concentration of 300 mg/L, indicating chemisorption-controlled behavior. Thermodynamic parameter analysis showed that within the experimental temperature range, ΔG⁰ < 0 and ΔS⁰ > 0, confirming that the adsorption process was spontaneous and endothermic. This study provides a novel technical approach for the green recovery of rare earth elements and highlights the potential of Spirulina biomass in rare earth resource recycling. Full article

Chemically demethoxylated and Ca-cross-linked orange-peel waste was engineered as a biosorbent for Mn(II) removal from water. A three-factor Box–Behnken design (biosorbent dose 3–10 g L⁻¹, initial Mn²⁺ 100–300 mg L⁻¹, contact time 3–8 h; pH 5.5 ± 0.1, 25 °C) required only 16 runs to locate the optimum (10 g L⁻¹, 100 mg L⁻¹, 8 h), at which the material removed 94.8% ± 0.3% manganese removal under the optimized conditions (10 g L⁻¹, 100 mg L⁻¹, 8 h, pH 5.5) of dissolved manganese and reached a Langmuir capacity of 29.7 mg g⁻¹. Equilibrium data fitted the Freundlich (R² = 0.968) and Sips (R² = 0.969) models best, indicating a heterogeneous surface, whereas kinetic screening confirmed equilibrium within 6 h. FTIR and SEM–EDX verified abundant surface –COO⁻/–OH groups and showed Mn deposits that partially replaced residual Ca, supporting an ion-exchange component in the uptake mechanism. A preliminary cost analysis (<USD 10 kg⁻¹) and > 90% regeneration efficiency over three cycles highlight the economic and environmental promise of this modified agro-waste for polishing Mn-laden effluents. Full article

Arsenic (As) contamination in the Tambo River (Perú), linked to mining activities and volcanic eruptions, poses significant health and agricultural risks. This study evaluated sodium alginate extracted from the brown macroalgae Lessonia trabeculata (LT) as a biosorbent for As removal. Water samples from three river points revealed As concentrations up to 0.309 mg/L, exceeding regulatory limits (0.1 mg/L). Sodium alginate was obtained via a simplified alkaline method, yielding an average of 21.44% (w/w relative to dry algae biomass) and characterized by Fourier Transform Infrared Spectroscopy (FTIR), showing structural similarity to industrial alginate (A1). Biosorption assays under simulated environmental conditions (neutral pH, 20 °C) demonstrated that LT alginate (A2) reduced As by 99% at 48 h with a 1.0 g/L dose, outperforming A1. Langmuir (q_max = 0.0012 mmol/g; b = 506.9 L/mg) and Freundlich (n = 1.94) isotherms confirmed favorable adsorption, while kinetics followed a Pseudo-Second-Order Model, suggesting physisorption. These results highlight LT alginate as a sustainable and scalable solution for remediating As-contaminated water, promoting the conservation of a vulnerable marine resource. This study underscores the potential of algal biopolymers in bioremediation strategies aligned with environmental and socioeconomic needs. Full article

Spent coffee grounds (SCG) are a widely available agro-industrial residue rich in carbon and phenolic compounds, presenting significant potential for biotechnological valorization. This study evaluated the use of SCG as a suitable substrate for fungal laccase production and the application of the resulting fermented biomass (RFB), a mixture of fermented SCG and fungal biomass as a biosorbent for textile dye removal. Two fungal strains, namely Lentinus crinitus UCP 1206 and Trametes sp. UCP 1244, were evaluated in both submerged (SmF) and solid-state fermentation (SSF) using SCG. L. crinitus showed superior performance in SSF, reaching 14.62 U/g of laccase activity. Factorial design revealed that a lower SCG amount (5 g) and higher moisture (80%) and temperature (30 °C ± 0.2) favored enzyme production. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses confirmed significant structural degradation of SCG after fermentation, especially in SSF. Furthermore, SCG and RFB were chemically activated and evaluated as biosorbents. The activated carbon from SCG (ACSCG) and RFB (ACRFB) exhibited high removal efficiencies for Remazol dyes, comparable to commercial activated carbon. These findings highlight the potential of SCG as a low-cost, sustainable resource for enzyme production and wastewater treatment, contributing to circular bioeconomy strategies. Full article

The present study compared the adsorption properties of two plant materials and the waste products after their essential oil extraction for removing Cu(II) ions from contaminated water. Methods like SEM, XRD, nitrogen adsorption, DTA, TGA, FTIR, and XPS were used for characterization of the materials. All materials showed similar porosity and structure, favoring Cu(II) biosorption. The effects of contact time, pH, temperature, sample amount, and initial metal concentration on Cu(II) removal were examined. Optimal pH was 4, with equilibrium reached in less than 10 min. Temperature and sample amount do not significantly influence the biosorption. The experimental data were fitted to the Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models, and maximum adsorption capacities were calculated. The four plant materials proved to be effective biosorbents for removing copper ions from contaminated water. Desorption experiments using 1 M HNO₃ and 0.1 M EDTA showed 100% recovery. The reusability of the most effective biosorbent was confirmed through four adsorption/desorption cycles with EDTA. This material was also used to study the possibilities of purifying a real sample of contaminated water. Full article

In this study, the presence of heavy metals (HMs) is determined to assess surface water contamination; biosorbent materials are also used to remove them and thus improve their quality. The objective of this work was to study the spatial distribution of HMs in water samples from Tequesquitengo Lake, Morelos, Mexico; pectin was also used for HM biosorption. For this, fifteen water samples were collected from the central and peripheral zones of the lake; HMs such as Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, As, and Hg were identified and quantified by atomic absorption spectroscopy (AAS). The metal evaluation index (HEI) was calculated, as well as the percentage of HM removal with pectin. The water samples presented high concentrations of Pb, Cr, and Mn in contrast to the other HMs studied. Furthermore, these showed high concentrations (161.2, 85.2, and 65.6 µg/L, respectively) in the peripheral zone. Therefore, these values exceed the permissible limit for human consumption, except for Mn. The HEI value indicated that the lake water exhibits low contamination. After the adsorption of HMs with pectin, Cr (100%), Ni (83%) and Cd (37%) were removed, reducing the total concentration of HMs in the water in all samples. Full article

In this study, Ni²⁺ and Cd²⁺ resistant Pseudomonas aeruginosa 18, Enterobacter ludwigii 11Uz, and Enterobacter cloacae Uz_5 strains were isolated from soils contaminated with heavy metals in the Samarkand and Kashkadarya regions (Uzbekistan), and tested to remove Ni²⁺ and Cd²⁺ ions from the environment via biosorption. The biosorption capacity of these strains was observed under in vitro conditions. The biosorption process was highly dependent on the growing conditions, with the highest biosorption rate observed after 300 min of incubation at pH 7.0, and 40 °C. The presence of functional groups such as S=O, NH₂, and COOH in the biosorbing microorganisms was confirmed by IR spectroscopy. The adsorption capacity decreased when the initial metal concentration was increased and was enhanced with higher microbial biomass. Enterobacter ludwigii 11Uz strain was found to alter the toxic oxidation state of Ni²⁺ and Cd²⁺ cations, while Pseudomonas aeruginosa 18 and Enterobacter cloacae Uz_5 strains reduced the toxicity of Ni²⁺ cations only by changing their oxidation state. It was confirmed in our studies that the three selected bacterial strains actively participated in the detoxification of Cd²⁺ through the synthesis of cysteine amino acid. 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 combined application of coagulation–flocculation–sedimentation (CFS) and adsorption using corncob (CC) biosorbent for the removal of textile dyes from aqueous solutions. Two synthetic dyes Bemacron Blue RS 01 (BB-RS01), a disperse dye, and Bemacid Marine N-5R (BM-N5R), an acid dye were selected for evaluation. The coagulation–flocculation process utilized aluminum sulfate as the coagulant and Superfloc 8396 as the flocculant, with operational parameters including coagulant concentrations ranging from 50 to 600 mg/L, flocculant concentrations between 30 and 125 mg/L, and pH levels spanning from 2 to 11. The corncob biosorbent was characterized using FTIR, SEM, BET, TGA/DTA, and pHpzc analyses. Adsorption isotherm experiments indicated a more favorable correlation with the Langmuir model (R² = 0.92–0.96), which supports monolayer adsorption. At pH 8, the CFS process achieved a dye removal efficiency of 95.1% for BB-RS01 and 92.3% for BM-N5R was achieved at pH 6.5. The maximum adsorption capacities of BB-RS01 were determined to be 99.5 mg/g, while BM-N5R was found to be 46.08 mg/g. These results indicate that the integration of CFS with raw corncob adsorption provides a cost-effective and efficient method for the remediation of textile dyes. Full article

The need to use environmentally friendly and cost-effective methods to remove heavy metals from wastewater is a permanent concern worldwide. Eggshells have been indicated as a worthy biosorbent for the adsorption of heavy metals due to their bioavailability and composition. In the present study, the absorption capacity of untreated chicken (CEs) and quail (QEs) eggshells for the removal of Pb and Zn ions from aqueous solutions was evaluated at room temperature and 40 °C, using four types of agitation systems: classical and orbital agitation and ultrasonic and microwave-assisted activation. The monitoring of aqueous solutions was performed by electrochemical and spectro-analytical (AAS) procedures before and after the adsorption process. FTIR and RAMAN spectroscopy, SEM-EDAX microanalysis, and X-ray diffraction were used to investigate the characteristics of eggshell samples post-exposure to Pb²⁺ or Zn²⁺. For any type of agitation and temperature, the CEs were able to induce more than 65% removal efficiency for lead and over 80% in the case of zinc. Concerning the Zn removal efficiency of QEs, notable results were recorded when microwaves were applied (>90%) and at 40 °C for orbital shaking and ultrasound (>80%). The results of the present study may offer new and valuable information for the optimal removal of Pb²⁺ and Zn²⁺ using eggshells, thus contributing to the sustainable management of waste through the recycling of this type of biomaterial. 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

Generally, cheap and environmentally friendly biosorbent materials attract the attention of researchers and become the focus of research. Cellulose and hemicellulose come to the fore among biosorbent materials in biosorption processes. However, lignin is also a very abundant and underutilized biopolymer resource that can be preferred for biosorbent production. Lignin is an amorphous phenolic biopolymer with a structurally three-dimensional branched network structure. This biopolymer has advantages such as being available in large quantities, as well as high selectivity and sorption capacity. However, one of the biggest disadvantages is that lignin exhibits a heterogeneous structure for the balanced production of biosorbents. The structural behavior of lignin depends largely on the source and the processing conditions from which it is isolated. Today, although the use of lignin-based biosorbents is increasing, only 5% of the available lignin globally is used. This review summarized the world’s current trends, perspectives, and recent developments in lignin-based biosorbents in terms of all properties of lignin. Full article

Spent coffee grounds (SCG) are produced in large quantities during coffee brewing, contributing to environmental concerns. Additionally, cationic dyes from textile, paper, and leather wastewater pose a major pollution issue. This study explores SCG as an adsorbent for methylene blue (MB) dye. A novel comparison of SCG cleaning methods with warm water, accelerated solvent extraction (ASE), supercritical fluid extraction (SFE), and ultrasound-induced cavitation (US) is presented. In addition, the chemical modifications of SCG using acetylation, acid (HNO₃), and base (KOH) treatment that have not been reported before are presented. ATR-FTIR confirmed the inclusion of functional groups, for example, the nitro group in SCG treated with HNO₃, and an increase in carboxylic groups in the samples treated with KOH and HNO₃. SEM analysis revealed a consistent porous texture across samples, with SCG-SFE, SCG-US, and SCG-HNO₃ showing smaller pores, and SCG-ASE displaying elongated cavities. Adsorption isotherm tests followed the Freundlich and Langmuir models, indicating favorable adsorption. The Langmuir maximum adsorption capacity (q_max) varied among cleaning methods from 65.69 mg/g (warm water) to 93.32 mg/g (SFE). In contrast, in base- and acid-treated SCG, a three- to four-fold increase in adsorption capacity was observed, with q_max values of 171.60 mg/g and 270.64 mg/g, respectively. These findings demonstrate that SCG washed with warm water and chemically treated achieves adsorption capacities comparable to other biosorbents reported in the literature. Therefore, SCG represents a promising, low-cost, and sustainable material for removing cationic dyes from wastewater, contributing to waste valorization and environmental protection. Full article