Zinc Adsorption Characteristics by Biochar Derived from Spent Coffee Grounds

Abstract

Zinc (Zn) adsorption characteristics of biochar derived from spent coffee grounds (SCGB) were evaluatedunder various conditions. Zinc adsorption was well described by pseudo-second order and Langmuir isothermmodels with maximum adsorption capacity of 26.6 mg g-1. Additional fitting of intraparticle model showedthat Zn in SCGB was controlled by both external surface adsorption and intraparticle diffusion. As a result ofadsorption of Zn on SCGB according to the initial pH, the adsorption capacity of Zn increased as pH increasedfrom 2 to 6, but decreased dramatically from pH 7. The adsorption capacity of Zn by SCGB in the presence ofother metals was remarkably reduced. In particular, the adsorption amount of Zn in the Pb and Zn complexsolution was reduced by 82.9% compared with that of the Zn single solution, which is considered to be closelyrelated to the properties of the metal itself such as electronegativity and hydrate radius. The FTIRdemonstrated that Zn in SCGB was related to carbon and oxygen functional groups. Overall, SCGB could beapplied as an adsorbent for Zn removal from aqueous solution, and its direct production through pyrolysis ofspent coffee grounds could make it an economic option as absorbent for treating Zn-rich wastewater.