Application of chemically-cross-linked chitosan for the removal of Reactive Black 5 and Reactive Yellow 84 dyes from aqueous solutions

Abstract

Abstract The study analyzed the sorption effectiveness of reactive dyes, Reactive Black 5 (RB5) and Reactive Yellow 84 (RY84), onto non-cross-linked chitosan beads (CHs) and onto CHs cross-linked with glutaraldehyde (ALD) i.e., ALD-CHs and epichlorohydrin (ECH) i.e., ECH-CHs. The study enabled determination of the optimal ratio of the cross-linking agent to chitosan and the optimal pH of the sorption process (from the range of 1:10–10:1, to 2–12, respectively). The time needed to reach the equilibrium concentration reached 504 h. Satisfactory effects of RB5 and RY84 sorption were achieved after 24 h sorption. Data were described with the heterogenous Langmuir’s model (double Langmuir’s equation). For RB5 dye, the most effective sorbent turned out to be CHs – the maximum sorption capacity reached 2025.11 (mg/g). For the other sorbents, ALD-CHs and ECH-CHs, the capacity accounted for 1797.0 mg/g and 1816.1 mg/g, respectively. In the case of RY84 dye, the most effective sorbent appeared to be ECH-CHs – 2234.3 mg/g. For CHs and ALD-CHs, the highest sorption capacities against RY84 reached 1774.2 and 2000.1 mg/g, respectively.