Low-cost Biosorbent Research Articles

The low-cost biosorbents of Mangosteen (Garcinia mangostana Linn) doped magnesium oxide and titanium dioxide beads for eliminating methylene blue dye

Two methylene blue (MB) dye adsorbents were synthesized from mangosteen peels modified by magnesium oxide and titanium dioxide called mangosteen peel doped magnesium oxide beads (MMB) and mangosteen peel doped titanium dioxide beads (MTB) to examine which material could greater adsorb MB dye. In addition, several techniques of BET, XRD, FESEM-FIB, EDX, and FT-IR were used for their characterizations. Their MB dye removal efficiencies were investigated by batch experiments, desorption experiments, adsorption isotherms, kinetics, and thermodynamic studies. MTB had a higher specific surface area (15.24 m2/g) and smaller pore size (1.69 nm) than MMB. The results of XRD, FESEM-FIB, EDX, and FT-IR demonstrated the successful additions of magnesium oxide and titanium dioxide into MMB and MTB because they found the specific peaks, characteristic structures, elements, and functional groups of magnesium oxide and titanium dioxide in MMB and MTB. Batch experiments showed they had high MB dye removal efficiencies of more than 97 %, and they could reuse more than three cycles. Freundlich and pseudo-second-order kinetic models were good explanations for their adsorption patterns correlated to chemisorption and their mechanisms to be a chemisorption process. In addition, they were an endothermic process since their MB dye adsorptions increased with increasing temperature.

Low-Cost Biosorbents Derived from Corn Husks for the Exclusion of Fe(II) and Cr(VI) Ions Undertaken Aqueous Media: Application for Wastewater Treatment

Low-Cost Biosorbents Derived from Corn Husks for the Exclusion of Fe(II) and Cr(VI) Ions Undertaken Aqueous Media: Application for Wastewater Treatment

Methylene blue adsorption by chemical-activated Trichanthera gigantea leaf

ABSTRACT This study investigated the potential of NaOH-treated Trichanthera gigantea leaf (TGL) powder as a sustainable, low-cost biosorbent for methylene blue (MB) removal from wastewater. Characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller, and energy-dispersive X-ray spectroscopy (EDX) techniques confirmed favorable morphology, identifying micropores, suitable functional groups, notable surface area, pore volume, and elemental diversity. Batch experiments systematically investigated the influence of operational parameters, including contact time, initial MB concentration (5–35 mg/L), pH (2–10), and biosorbent dosage (2–10 g/L) on adsorption performance. The Langmuir isotherm model best represented the experimental data (R² values of 0.993 and 0.9725), indicating favorable adsorption (RL < 1) and maximum MB adsorption capacities of 0.822 and 0.330 mg/g for treated and untreated TGL, respectively. Statistical analysis (ANOVA) results further identified the most significant factors influencing MB biosorption. These findings highlight the potential of NaOH-treated TGL powder as an effective and eco-friendly solution for removing MB dye from industrial effluents, contributing to sustainable wastewater treatment and environmental protection.

Sorbent selection for the recovery of gallium and indium from aqueous solutions: a sustainable approach to the recovery of strategic metals from LED lamps.

Gallium and indium, metals present in light-emitting diode (LED) lighting technology, can be effectively recovered from aqueous solutions by sorption. For this purpose, carbonaceous materials, such as activated carbon, or low-cost biosorbents as beer bagasse, spent coffee grounds or peanut shells, and a low-cost zeolite as chabazite, were characterized by BET, FTIR, XRD, and SEM analysis prior use. Protonated chabazite, with high surface area (505m2/g) and a Si/Al molar ratio of 3.4, showed high sorption capacities for gallium (56mg/g) and indium (92mg/g), which is 10 to 30 times higher than those of our carbonaceous materials (T = 298K, pH < 3, dosage = 1g/L). Sorption experiments with both metals in solution showed a competitive effect between gallium and indium for the sorption sites of the chabazite, showing more affinity toward gallium than indium. Ga3+sorbed/In3+sorbed molar ratio above 2 was achieved for the same initial concentration of both metals, increasing to almost 3 when the initial gallium concentration increased, which was appropriate since gallium concentration tends to be higher in LED chips. However, the sorption capacity for both metals was always around 0.35mmol Ga + In/g. The selectivity of the chabazite was conditioned by different behavior of both metals in aqueous solution at the sorption pH (below 3.5) being the predominant species in solution Ga(OH)2+ for gallium and In3+ for indium. Sorption with protonated chabazite can be used in the treatment of spent LEDs leachate for the dual purpose of water purification and selective metal separation.

Application of Marine Mollusk Shells (Meretrix lusoria) as Low-Cost Biosorbent for Removing Cd2+ and Pb2+ Ions from Aqueous Solution: Kinetic and Equilibrium Study

The present work aims to evaluate the applicability of mollusk (Meretrix lusoria) shells as a biosorbent for toxic metal ions (Cd2+ and Pb2+) following the batch mode biosorption procedure. Some well-known analytical methods have been used to characterize the biosorbent such as a scanning electron microscope (SEM), an energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction. The mechanism of metal ion biosorption was examined using various analytical techniques. Therefore, an evaluation of operating factors such as contact time, pH, initial concentration of metal ions, biosorbent dose, and temperature was performed. The results obtained in this investigation indicated that the optimum conditions for the biosorption of Cd+2 and Pb+2 ions are as follows: pH = 6; contact times of 90 min; and the 20 mg/L of initial [M2+]. And a biosorbent dosage of 1.0 g/100 mL for each metal ion solution was also determined. The maximum removal efficiency results were 90.6% for Cd+2 and 91.5% for Pb+2 at pH 6.0. The biosorption isotherm was investigated using three forms of linear equilibrium (Freundlich, Langmuir, and Temkin models). Kinetic studies were also conducted to determine the equilibrium time for the biosorption of the studied metals utilizing the pseudo-second-order, pseudo-first-order, and intraparticle diffusion model. The data indicate that the biosorption kinetics of Cd2+ and Pb2+ follow the pseudo-second-order models. According to the present study, it can be identified that the shell of Meretrix lusoria is a suitable biosorbent for Cd2+ and Pb2+ ions and can contribute to their removal from environmentally polluted water.

Machine learning for the adsorptive removal of ciprofloxacin using sugarcane bagasse as a low-cost biosorbent: comparison of analytic, mechanistic, and neural network modeling.

Contamination with traces of pharmaceutical compounds, such as ciprofloxacin, has prompted interest in their removal via low-cost, efficient biomass-based adsorption. In this study, classical models, a mechanistic model, and a neural network model were evaluated for predicting ciprofloxacin breakthrough curves in both laboratory- and pilot scales. For the laboratory-scale (d = 2.2cm, Co = 5mg/L, Q = 7mL/min, T = 18°C) and pilot-scale (D = 4.4cm, Co = 5mg/L, Q = 28mL/min, T = 18°C) setups, the experimental adsorption capacities were 2.19 and 2.53mg/g, respectively. The mechanistic model reproduced the breakthrough data with high accuracy on both scales (R2 > 0.4 and X2 < 0.15), and its fit was higher than conventional analytical models, namely the Clark, Modified Dose-Response, and Bohart-Adams models. The neural network model showed the highest level of agreement between predicted and experimental data with values of R2 = 0.993, X2 = 0.0032 (pilot-scale) and R2 = 0.986, X2 = 0.0022 (laboratory-scale). This study demonstrates that machine learning algorithms exhibit great potential for predicting the liquid adsorption of emerging pollutants in fixed bed.

Biocomposite Material Based on Lactococcus lactis sp. Immobilized in Natural Polymer Matrix for Pharmaceutical Removal from Aqueous Media.

Ecosystems are negatively impacted by pharmaceutical-contaminated water in different ways. In this work, a new biosorbent obtained by immobilizing Lactococcus lactis in a calcium alginate matrix was developed for the removal of pharmaceuticals from aqueous solutions. Ethacridine lactate (EL) was selected as the target drug. Lactococcus Lactis biomass was chosen for the biosorbent synthesis for two reasons: (i) the microbial biomass used in the food industry allows the development of a low-cost biosorbent from available and renewable materials, and (ii) there is no literature mentioning the use of Lactococcus Lactis biomass immobilized in natural polymers as a biosorbent for the removal of pharmaceuticals. The characterization of the synthesized biosorbent named 5% LLA was performed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis. Additionally, particle size and the point of zero charge were established. Batch biosorption investigations showed that using 5% LLA at an initial pH of 3.0 and a biosorbent dose of 2 g/L resulted in up to 80% EL removal efficiency for all EL initial concentrations (20-60 mg/L). Four equilibrium isotherms, given in the order of Redlich-Peterson > Freundlich > Hill > Temkin, are particularly relevant for describing the experimental data for EL biosorption on the 5% LLA biosorbent using correlation coefficient values. Kinetic parameters were determined using kinetic models such as pseudo-first-order, pseudo-second-order, Elovich, Avrami and Weber-Morris. The pseudo-second-order kinetics model provides the greatest fit among the evaluated equations, with correlation coefficients greater than 0.99. According to the study's findings, the developed biocomposite is a potentially useful material for the removal of pharmaceuticals from aqueous matrices.

Biosorption of Cd&lt;sup&gt;2+&lt;/sup&gt; Ni&lt;sup&gt;2+&lt;/sup&gt; and Zn&lt;sup&gt;2+&lt;/sup&gt; from Contaminated Well Water by Garlic Peel

The application of garlic peel was investigated as a low-cost biosorbent for Cd2+, Ni2+, Zn2+, and Pb2+ from aqueous solutions in a continuous system. Experiments were carried out in a fixed bed column, and the influence of different flow rates (from 2.0 to 3.3 ml min-1) on the breakthrough was studied. Column data obtained at different conditions were described using the Bohart-Adams, Thomas, and Yan models. The maximum amount of absorption was obtained for a lead ion with the amount of 490.68 mg g-1. The column removed 472.78 and 135.17 mg g-1 of cadmium and nickel ions, respectively, and the minimum value was obtained for zinc ions (55.08 mg g-1). The garlic peel was regenerated and reused two to four times in successive biosorption-desorption cycles. Differential pulse voltammetry (DPV) was used to measure kinetic models for the biosorption of lead and cadmium ions on garlic peels. Using DPV for lead and cadmium ions, the amount of adsorbed material was obtained at 2.58 and 2.23 mg g-1 using the pseudo 1st order equation and this value was obtained at 8.26 and 4.70 mg g-1 using the pseudo 2nd order equation for lead and cadmium ions, respectively. The results show that garlic peel absorbs lead and cadmium ions more than zinc and nickel ions. Because it is made up of several sulfur compounds, sulfur as a soft atom has a stronger interaction with lead and cadmium than other ions.

Innovative optimization for maximum magnetic nanoparticles production by Trichoderma asperellum with evaluation of their antibacterial activity, and application in sustainable dye decolorization

A pioneer microbial-based synthesis of various nanoparticles is gaining more attention due to their potent applications in various industries. The magnetic nanoparticles (M-nps) were fabricated for the first-time using the cell free extract of Trichoderma asperellum. The M-nps bioprocess optimization was performed using Response Surface Methodology and Artificial Neural Network.The bioprocess was significantly (P < 0.05) affected by pH, stirring speed, and incubation period. The M-nps displayed a strong antibacterial efficiency against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus in a dose-dependent manner. The minimum inhibitory concentration (MIC) for E. coli, P. aeruginosa, and S. aureus were respectively found to be 25.0, 6.25, and 3.125 µg/ml. While the minimum bactericidal concentration (MBC) was 25.0, 12.5, and 6.25 µg/ml. The highest inhibition zone of 22 mm was recorded for B. subtilis at 80 µg/ml with MIC and MBC of 3.125 µg/ml. The sodium alginate/M-nps microbeads was successfully prepared without any crosslinkers. The microbeads exhibited the highest adsorptive efficiency (84.32%) for malachite green at pH 8.0, dose 0.1 g, and time 60 min. The experimental data were superlative fitted to Langmuir’s isotherm, hinting monolayer adsorption of MG molecules with 117.65 mg g‐−1 adsorptive capacity. The regenerated beads continued up-to six consecutive cycles and maintained more than 90%, indicating the multiple time use of the prepared material. Hence, the green magnetic nanoparticles display promising application in combating bacterial pathogens. The magnetic microbeads can be employed as an alternative eco-friendly, highly efficient, sustainable, and low-cost biosorbent in removing contaminants from wastewater.

Remediation of 2,4,6-trichlorophenol from aqueous solution by raw and chemical modified date palm stone biomass: Kinetics and isotherms studies

Raw and citric acid chemically treated date palm stone agro-waste biomass (RDSB and CA-MDSB) powders were used to remove an important class of emerging industrial pollutants, i.e., 2,4,6-trichlorophenol (2,4,6-TCP) from aqueous solutions towards sustainable waste utilization to develop cost-effective technology for treating wastewater. The biomass characterization was performed by using different analytical techniques such as CHN elemental analysis, particle size, BET, FTIR, and SEM-EDX, TGA analysis. The FTIR spectral analysis revealed that the main chemical groups (N–C, O=C, H-O, H-C, and O–C) were involved in trapping 2,4,6-TCP. The highest adsorption was achieved with a contact time of 150 and 120 min, an initial concentration of 50-200 mg/L, and a biosorbent dosage ranging from 0.1 to 1.0 g/L RDSB and CA-MDSB, respectively. The experimental kinetic data of the adsorption process for both adsorbents (RDSB and CA-MDSB) fitted very well with the pseudo-second-order kinetic model and Langmuir equilibrium data. The 2,4,6-TCP maximum monolayer adsorption capacities were 53.7, and 123.8 mg/g for RDSB and CA-MDSB, respectively. The present research confirms that the date palm stone biomass could be used as an effective and low-cost biosorbent for the remediation of 2,4,6-TCP from an aqueous environment.

Acid-activated corn silk as a promising phytosorbent for uptake of Malachite green and Cd (II) ion from simulated wastewater: equilibrium, kinetic and thermodynamic studies

Malachite green (MG) dye and cadmium metal ion are toxic pollutants that should be removed from aqueous environment. The recent study aimed to examine the adsorption behavior of MG dye and Cd (II) from wastewater onto low-cost adsorbent prepared by activating corn silk with nitric acid (ACS) and characterized by SEM, FTIR, XRD, BET and TGA. The optimum MG and Cd (II) adsorption was observed at pH 7 and pH 9 and maximum uptake of both pollutants was at 0.5 g dosage, 60 mins contact time and 20 mg/L initial concentration. The retention of dye and metal ion by the studied adsorbent was best fit to Langmuir isotherm and Pseudo-second order kinetics. The maximum monolayer coverage capacity of ACS for MG dye and Cd (II) ion was 18.38 mg/g and 25.53 mg/g, respectively. Thermodynamic studies predicted a spontaneous reaction with exothermic process for MG dye whereas an endothermic and spontaneous process was confirmed for Cd ion based on estimated parameters. The adsorption mechanism of MG dye and Cd (II) uptake was by combination of electrostatic interaction, pore diffusion, ion exchange, pie-pie attraction, hydrogen bonding, and complexation. The adsorbed pollutants were effectively desorbed with significant regeneration efficiency after successive five cycles that proved the potential of low-cost biosorbent for selective sequestration of cationic dye and divalent metal ion from effluents.

Effective removal of fluoride and arsenic from groundwater via integrated biosorption and membrane ultrafiltration

Fluoride (F−) and arsenic, present as As(III) and As(V), are widespread toxins in groundwater across India, as well as in other countries or regions like Pakistan, China, Kenya, Africa, Thailand, and Latin America. Their presence in water resources poses significant environmental and health risks, including fluorosis and arsenicosis. To address this issue, this study developed an integrated process combining biosorbents and ultrafiltration (UF) for the removal of F−, As, and turbidity from contaminated water. Laboratory-scale adsorption experiments were conducted using low-cost biosorbents with different biosorbent dosages, specifically Moringa oleifera seed powder (MSP) and sorghum bicolor husk (SBH), along with sand as a binding medium. F− and As concentrations ranging from 2 to 10 mg/L and 3 to 12 mg/L, respectively, were investigated. Biosorbents and their different combinations were tested to determine their efficacy in removing dissolved F− and As. The results showed that a blend of 10-g/L MSP with SBH achieved the highest F− (97.20%) and As (78.63%) removal efficiencies. Subsequent treatment with a UF membrane effectively reduced turbidity and colloidal impurities in the treated water, achieving a maximum turbidity removal efficiency of 95.40%. Equilibrium kinetic and isotherm models were employed to analyze the experimental data, demonstrating good fit. Preliminary cost analysis indicated that the hybrid technology is economically viable and suitable for the separation of hazardous contaminants from aqueous solutions. This study underscores the potential of inexpensive biosorption technologies in providing clean and safe drinking water, particularly in industrial, rural, and urban areas.

Removal of Chromium (VI) from Water Using Orange peel as the Biosorbent: Experimental, Modeling, and Kinetic Studies on Adsorption Isotherms and Chemical Structure

The present work aims to assess the effectiveness and efficiency of orange peels as a low-cost biosorbent for removing Cr(VI) from an aqueous solution by the biosorbent process. The orange peels as adsorbent was characterized using different methods, such as FTIR, pHpzc, equilibrium pH, TGA, XRD, SEM, and (BET). The tests were conducted in the batch mode, and the effects of different parameters, such as the pH, dosage of the bioadsorbent, influent Cr(VI), and time, on the biosorption of Cr(VI) were investigated. The adsorption kinetics proved that a contact time of 90 min resulted in the highest (approximately 97.8%) Cr(VI) removal, with an adsorption capacity of 4.96 mg/g. Moreover, the increase in the biosorbent dosage (from 1 to 10 g/L) resulted in the enhancement in the Cr(VI) removal effectiveness. Moreover, the pH of the solution also affected significantly the effectiveness of the removal. The tests were conducted under acidic pH solution conditions, and the prediction of the pH value at a zero charge (pH pzc) was confirmed experimentally. Furthermore, the results from the batch-mode assays were successfully tested by an experimental design (full factorial design). The biosorption of Cr(VI) on orange peels occurred mostly according to the pseudo-second-order kinetic model and the uptake of Cr(VI) was satisfactorily described by the Langmuir model.

Kinetic and Equilibrium Modelling of Lead, Zinc and Copper Ions Sorption from Aqueous Solution Using Charcoal Fines

The potential of chemically modified charcoal fines UCF (unmodified charcoal fine) and MCF (modified charcoal fines) as low cost adsorbents for the removal of Pb2+, Cu2+ and Zn2+ ions from aqueous solution was studied. MCF was prepared by chemical modification of UCF with HNO3 and KOH followed by pyrolysis. The factors influenced the effectiveness of biosorption process were pH, contact time, initial metal concentration, temperature and adsorbent dosage. FT–IR spectra confirmed the existence and interaction of the adsorbents with the effluent pollutants. MCF exhibited optimum pH, temperature, contact time, initial metal ion concentration and biosorbent dosage values of 5, 35 0C, 90 minutes, 15 mg/L and 2 g, respectively. UCF exhibited optimum pH, temperature, contact time, initial metal ion concentration and biosorbent dosage values of 6, 35 0C, 100 minutes, 20 mg/L and 2.5 g, respectively. The adsorption isotherm modelling using both adsorbents showed that the equilibrium data conformed more to Langmuir than the Freundlich model. Kinetic studies showed that the adsorption processes followed a pseudo-second order kinetic model. Thermodynamic studies confirmed the spontaneity and feasibility of the adsorption process. The results showed that both adsorbent have the potential to be applied as alternative low cost biosorbent.

Biosorption of hexavalent chromium by biochar prepared from the Ceratonia siliqua pod: Kinetic, equilibrium, and thermodynamics studies

Ceratonia siliqua pod biochar sample (CBC) was generated in this work from C. siliqua (carob pod waste) biomass (CBM) by slow pyrolysis for 5h at 400°C as an alternative low-cost biosorbent for the removal of Cr(VI). The biosorption parameters that were adjusted were the initial pH (2.0–10.0), temperature (30°C, 40°C, and 50°C), biosorbent dose (0.01–0.03 g/50 mL), initial Cr(VI) concentration (10–100 mg/L), and contact period (0–360 min). The interaction between the surface functional groups on the CBM and CBC and the Cr(VI) ions was found to be the primary mechanism for Cr(VI) sorption via surface complexation and electrostatic interactions, according to the investigation of the pH influence. The Langmuir isotherm was shown to be more well-fitting than the Freundlich and Dubinin-Radushkevich isotherms for the concentration range of 10 to 100 mg/L. The testing results indicated a sorption capacity of 90.909 mg/g of CBM and 131.579 mg/g of CBC. According to kinetic investigations, the absorption of Cr(VI) ions onto CBM and CBC was defined in pseudo-second order. The findings of thermodynamic investigations showed that the biosorption of Cr(VI) ions onto CBM and CBC was an exothermic, spontaneous process. These findings demonstrated that, even for high concentrations of Cr(VI) in industrial wastewater, CBM and CBC could be viable, affordable alternatives as adsorbents.

Facile chemically activation process of kapok husk as a low-cost biosorbent for removal methylene blue dye in aqueous solution

This study discusses kapok husk (KH) activated by HNO3 as a biosorbent for methylene blue dye and analyses its adsorption ability. The adsorption capacity of KH is 330.161 mg g-1 with optimum conditions at pH 9, concentration 5500 mg L-1, contact time 15 min, and biosorbent temperature 25?C. The isotherm study followed the Langmuir isotherm model, as seen from the R2 value of 0.9993 and maximum adsorption capacity of 312.5 mg g-1, which indicated a monolayer in the adsorption process. The kinetic data show that KH followed the pseudo-second-order model. The results of the TGA analysis show that thermal stability affects the performance of biosorbents in the adsorption process. FTIR and SEM-EDS characterisation results showed that electrostatic interactions, cation exchange, and pore filling regulate the methylene blue dye adsorption mechanism on the surface of the KH. The reusability of KH through adsorption?desorption cycle analysis was achieved five times. This indicates that the biosorbent can be economically feasible for real wastewater treatment based on its good reusability and simple preparation and activation.

The role of biochar in heavy metal-contaminated wastewater and soil treatment: A Comprehensive review

As a result of water shortages, farmers are forced to use wastewater as an irrigation source for agricultural land, primarily for vegetables. Although wastewater contains abundant plant nutrients and are always readily available, it also contains hazardous contaminants, including heavy metals. Wastewater contains dangerous levels of heavy metals, particularly lead (Pb). Vegetables irrigated with Pb-contaminated wastewater create growth and yield problems and pose serious health risks to those who consume them. Thus, increased global demand for soil remediation is driven by concerns about heavy metal contamination. Toxic metals are prevented from entering food crops by using biochar as a low-cost biosorbent, which can immobilize heavy metals in wastewater-irrigated soil. Sorption, redox state alteration of heavy metals, soil pH modification, and precipitation are just some of the many mechanisms by which biochar can immobilize metals in soil. This can boost crop development and yield while also lowering human health risks. Soil heavy metals can be immobilized by several methods using biochar's features, like its high surface area and wide pH range, as well as its long-term stability and the presence of oxygen-containing functional groups. This review focuses on using biochar to reclaim soil and water that have been contaminated by heavy metals as well as to fertilize plants.

Sustainable utilization of nutmeg fruit rind waste for Cr(VI) removal and resource recovery from industrial wastewater: An integrated approach

The present study demonstrates an innovative circular economic process to repurpose agricultural waste, nutmeg fruit rind into an effective adsorbent followed by its value addition/safe disposal, thereby seamlessly aligning with the principles of green chemistry and sustainable waste management. Low-cost bio-sorbents are one of the most promising substances for pollutant removal in water treatment research. Fruit shells and peels are annoying to the environment because they contribute to solid trash after consumption and add to the daunting challenge of municipal solid waste management. This study investigated the potential of nutmeg fruit rind waste, a readily available agricultural byproduct, for the removal of hexavalent chromium (Cr(VI)) from contaminated streams. The findings highlight the significant removal efficiency of Cr(VI) ions through adsorption onto the nutmeg fruit rind waste, underscoring its potential as an affordable and eco-friendly solution for wastewater treatment. The study showed that pH, adsorbent dosage, adsorbate concentration, contact time, and temperature significantly influence adsorption. The insights into the adsorption mechanism revealed that the electrostatic interaction, hydrogen bonding, ion exchange, and surface complexation primarily contributed to the removal of Cr(VI) ions. The kinetics studies matched well with the pseudo-second-order kinetic model, and the sorption fits the Sips isotherm, while thermodynamic studies confirmed the spontaneity and exothermic nature of the process. The quantitative removal of Cr(VI) and other co-existing heavy metals from real textile wastewater samples was demonstrated. Finally, the spent adsorbent was subjected to anaerobic digestion to recover biogas and Cr(VI), which offers a sustainable solution to mitigate the contamination risk associated with discarding the spent adsorbent while contributing to resource recovery.

The shells of edible freshwater snails as a biosorbent for multi-metal ions from wastewater: Implication in effluent purification and waste valorisation

The generation of waste shells of edible freshwater snails, Filopaludina bengalensis and Pila globosa, following human consumption and use in aquaculture, encourages their utilisation as a potential biomaterial. In this experiment, we employed the shell dust derived from F. bengalensis (FSD) and P. globosa (PSD) shells as a biosorbent of Cd2+, Co2+, Cr2O72- and Cu2+ from single- and multi-metal solutions. The results of batch adsorption experiments and characterisation of FSD and PSD using SEM, EDS, ICP-OES, FTIR, and XRD indicated that the metal ion removal process involved chemical adsorption (formation of CdCO3, Cu2CO3(OH)2 and CoCO3), ion exchange (reduced quantity of various elements on the shell dust following their release into the solution during adsorption) and surface precipitation. The best-fitted Langmuir isotherm specified monolayer adsorption with maximum adsorption capacity for Cd2+ (in single-metal system: FSD- 254.42, PSD- 327.76 mg/g; in multi-metal system: FSD: 93.79, PSD: 94.45 mg/g) and Cu2+ (in single-metal system: FSD- 234.63, PSD- 289.71 mg/g; in multi-metal system: FSD: 150.01, PSD: 160.51 mg/g). In multi-metal systems, the adsorption of Cd2+ and Cu2+ was antagonistic, and the adsorption of Co2+ and Cr2O72- was synergistic in nature. The thermodynamic parameters suggest that the adsorption is endothermic, feasible and spontaneous. The successful removal of metal ions from single- and multi-metal solutions and real wastewater recommended FSD and PSD as eco-friendly and low-cost biosorbent for wastewater amelioration with implication in waste valorisation.

Efficiency evaluation of Falcaria vulgaris biomass in Co(II) uptake from aquatic environments: characteristics, kinetics and optimization of operational variables

In the present research, the seeds of Falcaria vulgaris were extracted from the investigated environment and used for crop cultivation. This study has focused on the efficiency evaluation of Falcaria vulgaris biomass (FVB) in cobalt ions removal from aqueous solutions. The biosorbent was characterized using FTIR, BET, EDAX-EDS, and SEM. The optimal conditions were determined by the response surface methodology (RSM) based on a Box-Behnken design (BBD) model. The BBD model had R 2 , R adj 2 and R pred 2 values of 0.9919, 0.9774, and 0.8929, respectively. The cobalt removal under different conditions of the BBD model varied from 36.14% to 82.11%. Based on the numerical optimization of the quadratic model, the maximum cobalt removal at a biosorbent-to-metal ratio of 10:1, pH = 4.88 and contact time of 70 min was calculated at 80.941%. The high accuracy of the model in predicting the optimal conditions for cobalt adsorption by FVB was confirmed using statistical analysis and validation tests. The adsorption process of FVB also follows a pseudo-second-order kinetic model, which suggests that the rate-controlling step in cobalt removal is the chemical interaction between functional groups in FVB and Co+2 ions. This study shows that FVB, a low-cost biosorbent, can be a suitable candidate for removing heavy metals such as cobalt from aqueous solutions.