Adsorption of Ciprofloxacin onto Lotus Stem-Derived Biochar: Effects of Solution pH, Temperature, and Coexisting Cations

High performance of Fe(III)-modified maize stover biochar for adsorptive removal of sulfamethoxazole from aqueous solutions

Adsorptive Removal of Cd²⁺ from Aqueous Solution Using Arecanut Husk-Derived Biochar under Different Experimental Conditions

Heavy metals occur naturally in soil due to the weathering of parent materials.  At trace levels, they are nontoxic. Cadmium is a heavy metal that is highly toxic at low levels.  This study investigates the potential of Arecanut husk-derived biochar as a low-cost and eco-friendly adsorbent for removing cadmium ions (Cd²⁺) from aqueous solutions. Biochar production was carried out using a pyrolysis process. The results demonstrated that adsorption capacity (qe) was strongly influenced by biochar dosage, contact time, solution pH, and temperature, on cadmium removal efficiency. Optimal performance was observed at a biochar dosage of 60–80 mg, contact time of 60 minutes, pH range of 6–8, and a temperature of 50°C.  Under these optimal conditions, the maximum adsorption capacity was found to be 1.73 mg/g and removal efficiency was achieved up to 89.8%. FTIR analysis revealed the involvement of functional groups, including C-H, –COOH, and C=O, in the adsorption process through coordination and complexation with cadmium ions. XRD analysis confirmed the successful immobilization of Cd²⁺ via the formation of cadmium-containing crystalline phases, without altering the biochar’s amorphous carbon structure. These findings indicate that chemisorption mechanisms, including surface complexation and mineral precipitation, primarily govern cadmium adsorption. To the best of our knowledge, this research study signifies a novel, acceptable, innovative method that is eco-friendly, cost-effective, and utilizes readily available materials, such as biochar derived from arecanut husk, which helps as a promising, sustainable, and efficient adsorbent for the remediation of cadmium-contaminated water.

Enhanced adsorption of ciprofloxacin from water using raw and phosphoric acid-modified cauliflower-leaves derived biochar: response surface optimization

Ciprofloxacin (CIP), a widely prescribed fluoroquinolone antibiotic, has emerged as an environmental concern because of its persistence in aquatic systems, limited removal by conventional treatment processes, and role in the spread of antibiotic resistance. While biochar adsorption has gained attention for pharmaceutical removal, the use of cauliflower-leaf-derived biochar, particularly after chemical modification, has received limited investigation. Furthermore, studies integrating optimization of both biochar preparation and adsorption performance remain scarce. In the present study, raw cauliflower-leaf biochar (CLB10) and phosphoric-acid-modified biochar (PAM-CLB1.5) were evaluated for CIP removal from water using Response Surface Methodology based on a Box–Behnken experimental design. The optimized preparation conditions, i.e., pyrolysis time, temperature, and particle size for CLB10 were identified as 90 min, 475 °C, and 272.5 μm, respectively. Under optimized adsorption conditions, CLB10 achieved 78.43% CIP removal, whereas PAM-CLB1.5 exhibited substantially higher removal efficiency (97.54%), demonstrating the beneficial effect of phosphoric acid modification. Surface characterization showed that acid treatment enhanced pore development, increased specific surface area from 15.03 to 24.65 m2 g-1, and introduced phosphorus-containing functional groups that promoted stronger adsorbent–adsorbate interactions. CIP adsorption data were better described by the Langmuir isotherm model for both CLB10 and PAM-CLB1.5, suggesting predominant monolayer-type adsorption behavior under the investigated conditions. Kinetic data followed the pseudo-second-order model, indicating that adsorption was strongly influenced by surface-site-controlled interactions. Higher removal efficiency was attributed to the combined effects of pore filling, hydrogen bonding, electrostatic attraction, and π–π interactions. Regeneration experiments demonstrated satisfactory reusability, with the modified biochar retaining approximately 87% removal efficiency after five adsorption–desorption cycles. It was concluded that PAM-CLB1.5 could be used as an efficient adsorbent for the removal of CIP from water.

Removal of phosphate from activated biochar prepared from bentonite biochar composite: Kinetic, equilibrium, thermodynamic adsorption

Excess phosphorus threatens both aquatic ecosystems and human health. This study investigated the kinetic, equilibrium, and thermodynamic behavior of phosphate (PO43–) adsorption using a low-cost composite adsorbent synthesized from bentonite and rice-husk–derived activated carbon. Batch experiments examined the influence of initial PO43– concentration, temperatures, contact time, pH, and co-existing anions. The findings revealed that the PO43– adsorption onto synthesized material was best represented by Langmuir isotherm theory. Kinetic analyses showed that PO43– adsorption follows both pseudo-first and pseudo-second-order models, exhibiting strong correlation coefficients (R² = 0.99). The optimal pH for adsorption was identified as 7. The presence of co-existing anions such as CO32–, SO42–, and Cl⁻ notably decreased the efficiency of PO43– removal. The synthesis of material based on bentonite and biochar from rice husk demonstrates strong potential for PO43– removal and recovery from water.

Sustainable methylene blue adsorption using lignocellulosic biochar with mechanistic isotherm, kinetics, thermodynamic and error insights

Adsorption of chromium ions using two types of aqueous biochar

Biochar is a porous, carbon-rich substance created when biomass is thermally broken down in an oxygen-limited environment. The removal of chromium ions from polluted water has been extensively investigated because of its large surface area and surface functional groups. This study observes the production of biochar from a variety of biomass sources, such as Pomegranate husks (Po-Biochar) and animal waste (An-Biochar), and assesses how well these methods remove Cr(VI) from aqueous solutions. FTIR, FE-SEM, and BET were used to describe the biochar samples. The effects of pH, contact duration, Cr(VI) concentration, and biochar dose were evaluated using adsorption studies. According to the data, An-Biochar exhibited the maximum adsorption capacity. The adsorption process also followed pseudo-second-order kinetics, and the Freundlich isotherm was found to be the best one that can describe the adsorption of chromium ions Cr(VI) over Po-Biochar and An-Biochar samples, compared with the Langmuir isotherm, all of which were noted from the correlation coefficient values R2.