Green grape marc biosorbents preparation for mercury removal in aqueous media

Abstract

In this study, grape marc waste from Negroamaro (a South of Italy vine variety) winery production was used to prepare biosorbents for Hg(II) removal in aqueous media. A green approach was used to develop a proper biosorbent through two different grape marc washing procedures. In particular, the common chloridric acid and the greener citric acid were evaluated. The biosorbent prepared using citric acid as a washing agent (GM-CA) gave similar results to the biosorbent washed with HCl (GM-HCl) with a maximum adsorption capacity of 36.39 mg g-1. Isothermal studies revealed heterogeneous physical adsorption of Hg(II) on the biosorbents. Moreover, FTIR analysis of the grape marc-based biosorbent without and with Hg(II) confirmed ionic interactions in the biosorbent that fit with a pseudo-second-order kinetic model. Furthermore, no significant adsorption on the biosorbent was observed when two other heavy metals, copper(II) and nickel(II), previously studied for similar sorbents, were considered. Finally, the reusability of GM-CA biosorbent was also demonstrated over three cycles. Thus, the green preparation approach used in this work can be considered suitable for developing grape marc-based biosorbents.

Keywords

• adsorption isotherms
• citric acid
• hg(ii) removal
• grape marc
• green waste biosorbent
• kinetic study