Efficient removal of Cr(VI) by polyaniline modified biochar from date (Phoenix dactylifera) seed

Though multiple number of strategies have investigated for toxic Cr(VI) removal, still researchers are chasing after innovative and environmental friendly substrate for efficient removal of pollutant. Herein, we report a polyaniline coated date seed derived biochar (PANIDSC) prepared via polymerization which acts as a proficient adsorbent for Cr(VI) remediation. A thorough investigation using FESEM, Raman, TGA, FTIR, XRD, zeta potential, and BET analytical techniques confirmed the structural stability and suitable morphology of the as-made PANIDSC. Spongy like carbonaceous structure with uniformly distributed pore is evidenced from FESEM and broad XRD peak. Increment in I_D/I_G value from 0.73 to 0.93, and appearance of significant peak at 1288 cm⁻¹ for PANIDSC material confirmed the surface modulation. Thermal stability up to 650 °C of material is demonstrated even after polyaniline grafting. Conducting batch experiments, the influence of adsorbent dose, pH, time, initial concentration, temperature, and stirring rate on removal of Cr(VI) is investigated. Experimental findings from adsorption kinetics and isotherms are fitted to Langmuir, Temkin, Dubinin Radushkevich, Redlich-Peterson isotherms models and pseudo first order, pseudo second order, intra particle diffusion, Elovich kinetics models, consecutively. However, present polyaniline grafted biochar adsorbent is well-fitted with pseudo second order model having the R² value 0.995. In agreement with the isoelectric point at 5.8, maximum Cr(VI) adsorption on PANIDSC perceived at pH range of 4–5. The thermodynamic parameters indicated that the process of adsorption is spontaneous and endothermic in nature (ΔH = 25.084 kJ mol⁻¹). Furthermore, the efficient regeneration up to 5 successive cycles makes the low-cost bio adsorbent a promising one for field applications study.