Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies

Abstract

<title>Abstract</title> In the current work, three adsorbent materials were developed; biochar derived from date palm fiber (C), date palm fiber biochar/chitosan nanoparticles (CCS), and biochar/chitosan nanoparticles composite supplemented with glutamine (CCSG). These compounds were used as solid adsorbents to remove As⁵⁺ from polluted water. Several characterization approaches were used to investigate all the synthesized solid adsorbents, including TGA, N₂ adsorption/desorption isotherm, SEM, TEM, ATR-FTIR, and zeta potential. CCSG demonstrated good thermal stability, with a maximum specific surface area of 518.69 m²/g, a microporous radius of 0.97 nm, total pore volume of 0.25 cm³/g, an average particle size of 38 nm, and pH_pzc of 6.9. To optimize the reaction conditions, various sorption factors were examined, including contact time, pH, initial As⁵⁺ concentration, adsorbent dosage, temperature, and ionic strength. The study found that the modified samples were able to remove more As⁵⁺ (CCS; 256.0 mg/g and CCSG; 376.0 mg/g) than unmodified ones (C; 150.5 mg/g). The As⁵⁺ removal procedure corresponded well with Langmuir isotherm model. Thermodynamic and kinetic experiments show that the Elovich, PFO, and Van't Hoff plot with endothermic, spontaneous, and physisorption nature are the best fitted models. EDTA has the highest desorption efficiency percentage (98.8%). CCSG demonstrated enhanced reusability after six application cycles of As⁵⁺ adsorption/desorption, with only a 4% decrease in the efficiency of adsorption. This study demonstrates that CCSG effectively remove As⁵⁺ in wastewater and use agricultural solid waste residues (date palm fiber; DPF) for environmental remediation purposes.