Zinc Adsorption Characteristics by Biochar Derived from Spent Coffee Grounds

Abstract

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