Adsorption of ammonium and phosphates by biochar produced from oil palm shells: Effects of production conditions

Abstract

This study investigated the effects of production conditions on the ammonium and phosphate adsorption capacity of oil-palm-shell-biochar. Biochar was prepared at three pyrolysis temperatures (350, 650, and 750 °C), under three activation conditions (no oxidation, partial oxidation at 250 °C, and chemical activation with K2CO3), and using three washing methods (no washing, acid washing, and hot water). Physicochemical properties of certain biochar samples were characterized by SEM, CHON-S, XRF, FTIR, and area BET. The highest ammonium adsorption capacity (1.49 mg/g) was observed for chemically activated biochar pyrolyzed at 650 °C without washing. The best phosphate adsorption capacity (0.89 mg/g) was observed for partially oxidized biochar pyrolyzed at 650 °C with acid washing. The BET surface area ranged from 4 to 253 m2/g. The biochar produced at 350 °C without washing had more surface functional groups than that produced at higher temperatures. The chemical activation process promoted the development of numerous functional groups on the biochar surface.