Application of biochar derived from date palm biomass for removal of lead and copper ions in a batch reactor: Kinetics and isotherm scrutiny

Abstract

Abstract Batch absorptive potential of biochar derived from date palm waste biomass (DPb) for lead (Pb2+) and copper (Cu2+) was explored and batch adsorption conditions were optimized in this study. Scanning electron microscopy, Fourier transform infrared, and powder X-ray diffraction analyses of DPb were performed to characterize the adsorbent. An initial rapid adsorption followed by slow uptake of both Pb2+ and Cu2+ by DPb resulted in equilibrium times of 30–60 min and 2–3 h for Pb2+ and Cu2+, respectively. The optimum pH levels were 4.5 and 5.5 for maximum adsorption capacity for Pb2+ (98.9 mg g−1) and Cu2+ (41 mg g−1), respectively. Linear decrease in the metal uptake and removal efficiency occurred respectively by increasing the DPb dose (0.2 to 1.8 g) and initial concentrations of both heavy metal ions (50–250 mg L−1). The optimum amount of DPb for Pb2+ adsorption was 1.0 g, whereas the removal efficiency continued to increase for Cu2+ (92 mg g−1), up to the maximum dose used in this study (1.8 g DPb). The Freundlich-Langmuir (R2 = 0.95) and Harkins–Jura (R2 = 0.92) isotherms were the best-fit models for the Pb2+ and Cu2+ adsorption data, respectively. A strong correlation between the pseudo second-order kinetic model and experimental data of Pb2+ and Cu2+ adsorption was observed, supporting the hypothesis of chemisorption as the rate-controlling step. Successful application of DPb for Pb2+ and Cu2+ point to its potential for economically beneficial large-scale application in wastewater treatment.