Effective Adsorption of Pb2+ on Porous Carbon Derived from Functional Octadecahedron ZIF-8

Abstract

An adsorbent ZO (oxidized ZIF-8-derived carbon) was prepared on the ZIF-8-derived carbon (ZC) by modified Hummer’s method. The removal rate and adsorption amount of Pb2+ were measured on the different molar ratios of 2-Hmim to 2, 2′-bipyridine in ZO, including 1:1 (1:1 ZO) and 1:2 (1:2 ZO). The adsorption experiments show that the best condition to adsorb Pb2+ in Pb2+ solution for 1:1 ZO is an adsorbent dosage of 20 mg, adsorption time of 16 h, initial Pb2+concentration of 15 mg/L, and pH = 3; that for 1:2 ZO is the adsorbent dosage of 15 mg, adsorption time of 18 h, initial Pb2+ concentration of 15 mg/L, and pH = 4. The adsorption data fits the quasi-second-order kinetics (R2 = 0.99998), indicating that chemical adsorption plays a leading role. The fitted isotherm adsorption curve is more consistent with the Langmuir adsorption model (1:1 ZO, R2 = 0.95058; 1:2 ZO, R2 = 0.97488). The competitive adsorption results show that the removal rate of Pb2+ by 1:1 ZO and 1:2 ZO is more than 98%, indicating that 1:1 ZO and 1:2 ZO have a superior selectivity for Pb2+ competing with Cu2+ and Fe2+. The maximum adsorption amount of Pb2+ is 15.52 mg/g by 1:1 ZO and 18.09 mg/g by 1:2 ZO. This study shows that 1:2 ZO is more helpful for the removal of Pb2+ than 1:1 ZO.