Phenanthrene removal from aqueous solutions using well-characterized, raw, chemically treated, and charred malt spent rootlets, a food industry by-product

Abstract

Malt spent rootlets (MSR) are biomaterials produced in big quantities by beer industry as by-products. A sustainable solution is required for their management. In the present study, MSR are examined as sorbents of a hydrophobic organic compound, phenanthrene, from aqueous solutions. Raw MSR sorb phenanthrene but their sorptive properties are not competitive with the respective properties of commercial sorbents (e.g., activated carbons). Organic petrography is used as a tool to characterize MSR after treatment in order to produce an effective sorbent for phenanthrene. Chemical and thermal (at low temperature under nitrogen atmosphere) treatments of MSR did not result in highly effective sorbents. Based on organic petrography characterization, the pores of the treated materials were filled with humic colloids. When pyrolysis at 800 °C was used to treat MSR, a sorbent with new and empty pores was produced. Phenanthrene sorption capacity was 2 orders of magnitude higher for the pyrolized MSR than for raw MSR.