Multistage optimizations of slow pyrolysis synthesis of biochar from palm oil sludge for adsorption of lead.

This research investigated the removal of lead (Pb 2+ ) by a novel biochar derived from palm oil sludge (POS-char) by slow pyrolysis. Multistage optimizations with central composite design were carried out to firstly optimize pyrolysis parameters to produce the best POS-char for Pb 2+ removal and secondly to optimize adsorption conditions for the highest removal of Pb 2+ . The optimum pyrolysis parameters were nitrogen flowrate of 30 mL min −1 , heating rate of 10 °C min −1 , temperature of 500 °C and time of 30 min. The optimum Pb 2+ adsorption conditions were concentration of 200 mg L −1 , time of 60 min, dosage of 0.3 g and pH of 3.02. The various functional groups within POS-char played a vital role in Pb 2+ uptake. Regeneration was demonstrated to be feasible using hydrochloric acid. Adsorption equilibrium was best described by Freundlich model. At low concentration range, adsorption kinetic obeyed pseudo-first-order model, but at high concentration range, it followed pseudo-second-order model. Overall, the results highlighted that POS-char is an effective adsorbent for Pb 2+ removal. [ABSTRACT FROM AUTHOR]