Pb(II) sorption by biochar derived from Cinnamomum camphora and its improvement with ultrasound-assisted alkali activation

Conversion of solid wastes into biochar for removal of toxic heavy metals provides a cleaner method for waste management and benefits environmental protection. Ultrasound-assisted alkali activation of biochar prepared by pyrolysis of camphor leaves (Cinnamomum camphora) was used as sorbent (AABC) for Pb(II) sorption. The biochar was characterized by XPS, FTIR, XRD and SEM. Ultrasound-assisted alkali activation results in more surface groups, larger surface area and pore volume, contributing to larger sorption capacity of AABC. AABC shows larger sorption rate than biochar (BC) without alkali activation. Chemisorption between surface groups and Pb(II) ions is verified by the pseudo-second order kinetics. Langmuir isotherm suggests that the maximum monolayer sorption capacity of Pb(II) onto AABC is 98.33 mg g(-1), 2.5 times higher than BC and comparable to reported biochar. Ultrasound-assisted alkali activation provides a promising method for improving sorption capacity of biochar in terms of heavy metals sorption.