Chars from co-gasification of rice wastes as Cr(III) removal agents

Rice husk (80% w/w) and polyethylene (20% w/w) were submitted for co-gasification. The resulting char (GC) was characterized and used in Cr(III) liquid-phase removal assays. A Commercial Activated Carbon (CAC) was also used for comparison purposes. GC was mainly composed of ashes (68.3% w/w), with Si being the major mineral element and K the most soluble one. GC presented an alkaline character, which was responsible for an ecotoxic level in the char. In the Cr(III) removal assays, three Solid/Liquid ratios (S/L) were used: 2.5, 5.0 and 10.0 g L⁻¹. Generally, GC performed better than CAC: in the S/L of 10.0 g L⁻¹, GC removed 98.9% of Cr(III) (mainly by precipitation), while in the S/L of 5.0 g L⁻¹, GC removed 42.3% of Cr(III) by adsorption. The ionic exchanges of K+ from GC and Cr(III) in the liquid medium were the predominant removal mechanism.