A versatile sorbent that can clean metals from wastewater at a lower cost – Chemical Engineering

June 1, 2024 | By Mary Page Bailey

At the 2024 Spring Meeting of the American Institute of Chemical Engineers (AIChE; www.aiche.org), a team from the National Energy Technology Laboratory (NETL; www.netl.doe.gov) presented on a recently patented technology for the removal of critical and heavy metals from wastewater (diagram). The Multi-Functional Sorbent Technology (MUST) is composed of an epoxy-amine crosslinked polymer network immobilized within the pores of a silica support, explains NETL researcher McMahan Gray. When compared to activated carbon, a commonly used sorbent for recovery and removal of metals from water, MUST binds the metals much more strongly, while also being more selective toward specific metals. It also boasts a simple, one-pot preparation method that can be easily scaled, and is readily regenerable. According to the NETL, MUST costs around $300/ft³, whereas competitive technologies may range from $500–800/ft³.

MUST is produced via wet impregnation, which involves the suspension of silica particles in a dilute solution of amine, crosslinkers and solvent. “Then, pulling a vacuum under extended modest heating evaporates the solvent and completes the crosslinking reaction. This produces a dry, granular sorbent after only 1 h of total preparation time,” says Gray.

An 18-kg batch of a single-crosslinker MUST formulation was produced by a commercial partner and used for the recovery of rare-earth elements, and a prior generation of the sorbent, which was used for CO₂ capture, was produced at the ton scale. “The sorbent was initially developed to treat fossil-related wastewaters, like acid-mine drainage and fluegas desulfurization wastewater. However, the sorbent was successful in removing metals like lead from tap water, manganese from simulated hydraulic fracturing water and various metals from nonaqueous waste streams, as well as natural and synthetic dyes. We further expect the sorbent to successfully remove per- and polyfluoroalkyl substances (PFAS),” adds Gray. The next step for MUST is a potential commercial partnership that will see the sorbent cleaning industrial-effluent waste streams.