Elimination of Lead (II) Ions from Aqueous Solution by Clay-Biochar Composite Prepared from Kaolin and Date Seeds

This paper reports the co-pyrolysis of kaolin clay (KC)/date seeds (DS) for developing a novel activated kaolin clay mineral-biochar (KC-BC) composite to be used in the adsorptive elimination (AE) of lead (II, Pb2+) from contaminated water. An optimal KC-BC was synthesized by the co-pyrolysis of a blend containing KC and DS in the ratio of 1:3 at 600 °C for 1 h and at the heating rate of 10 °C/min. This KC-BC was characterized through X-ray diffractometry, field-emission scanning electron microscopy, energy-dispersive analysis X-ray, and Brunauer–Emmett–Teller (BET) surface area analysis. The as-prepared KC-BC exhibited a BET surface area of 59.88 m2/g and a mean pore diameter of 11.42 nm, indicating its mesoporous structure. Superior AE % of 100 mg/L Pb2+ solution (95.10%) was obtained using 0.30 g of KC-BC at 35 °C for 210 min. The adsorption studies indicated that the Langmuir isotherm and the pseudo second-order kinetic model best described the adsorption of Pb2+ by the prepared KC-BC. Finally, the regeneration of the KC-BC for multiple cycles was explored as well.