Effect of pyrolytic temperature on the adsorption of Pb(II) from synthetic wastewater onto bamboo chopstick biochar: a conventional vs. microwave-assisted pyrolysis approach

Abstract

This study investigated the effects of different pyrolytic temperatures on Pb(II) adsorption from synthetic wastewater using waste bamboo chopsticks (BCs) produced via conventional and microwave-assisted pyrolysis. Eleven biochars were prepared and characterized using Brunauer‒Emmett‒Teller analysis, elemental analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. Thereafter, the selected biochars were further analyzed through batch adsorption studies. The influence of adsorbent dose, initial Pb(II) concentration, and contact time on the removal of Pb(II) from synthetic wastewater was studied. For the adsorbent dose, good removal efficiencies and adsorption capacities were observed at an adsorbent dose of 2 g L−1 and at an initial concentration of 50 mg L−1. For the initial Pb(II) concentration, high adsorption capacities and removal efficiencies were observed at 50 mg L−1 for concentrations ranging from 5 to 100 mg L−1. The contact time reached equilibrium within 24 h, where BC 450 W had the highest removal efficiency of 99.9%. Furthermore, the Langmuir isotherm model best represented the adsorption of Pb(II) onto biochar, with the highest qm of 81 mg g−1 at R2 = 0.978. Pseudo-second-order kinetics provided the best overall fit for the adsorption kinetics of the biochars, with R2 = 1.00 for BC 450 W and BC 700 °C. Among the many chemisorption processes identified in previous studies, surface complexation has been identified as a possible adsorption mechanism for Pb(II) on the biochars produced. BC biochar could be a sustainable means for remediating polluted mine water and managing waste.