Recovery of Metal Ions from Aqueous Solutions by γ-Alumina Creates Value-Added Catalyst Products

Mining and extracting metals from hard rock adverselyimpact theenvironment. These impacts could be mitigated by capturing dissolvedmetals from water (i.e., mine runoff, industrial wastewaters, or eventap water) and converting the metals to products with potential economicbenefits (i.e., upcycled into high-value products). We sought to identifya sorbent that can remove dissolved metals from water and in the processof this low-temperature surface adsorption create a catalytic materialof potential economic value. We discovered that gamma-aluminum oxide(gamma-Al2O3) can produce a reactive catalystafter removing metal ions (copper (Cu), palladium (Pd), nickel (Ni),and cobalt (Co)) from water, even for dissolved metals at environmentallyrelevant concentrations. The resulting metal-coated gamma-Al2O3 behaved, comparable to high-temperature producedcatalysts, as a mono- or bimetallic catalyst capable of oxidizingor reducing pollutants (methylene blue, 4-nitrophenol, nitrite, andnitrate). Mono- or bimetallic catalysts synthesized from tap waterwith metal ions present efficiently oxidized methylene blue (by Cu/gamma-Al2O3) or reduced nitrate (by Pd-Cu/gamma-Al2O3) into less harmful species (i.e., ammonium anddinitrogen gas). Results demonstrated the versatile use of gamma-Al2O3 that removes metal ions from water (i.e., waterpurification) and produces a valuable gamma-Al2O3-based byproduct with proven catalytic reactivity (i.e., catalystproduction) and commercial markets. Gamma aluminumoxide remediated metals from water whileproducing metal-saturated catalysts with activity comparable to commercialcatalysts.