Valorisation of Lignocellulosic Biomass Wastes for the Removal of Metal Ions from Aqueous Streams: A Review

Abstract

Heavy metal pollution derived from anthropogenic activities is a relevant environmen‐ tal threat nowadays due to their toxic nature, persistence and accumulation potential in the food chain. A wide variety of lignocellulosic‐based biomaterials have been thoroughly assessed by the scientific community as sorbents for the removal of metals from aqueous streams. This kind of biomaterials, mainly constituted by lignin and cellulose, bear functional groups such as alcohol, ketone and carboxylates that provide active sorption points for the effective removal of heavy metals. The role of lignin in the sorption process is especially relevant, since this substance provides polyhydroxy and polyphenol functional groups—especially effective in the coordination of metals—and that provide ion exchange functionality to the material. Depending on their nature, these materials can be used either in their raw form or chemically modified form so as to enhance their sorption capacity and/or to achieve improved mechanical and mass transfer properties.