Biosorption of Congo red in a fixed-bed column from aqueous solution using jujube shell: Experimental and mathematical modeling

Jujube shell (JS) is agricultural waste and environmentally friendly biosorbent was used for the removal of Congo red (CR) from aqueous solution in a fixed-bed column system. The biosorbent was characterized by FTIR, SEM and TGA-DTA analysis. Variables in the process were bed depths (2, 4 and 6 cm), flow rate (2.8, 4.5 and 6.4 min/L), influent CR concentrations (100, 200 and 300 mg/L) and particles size (50-100, 100-315, 315-500 and 500-1000 mu m). The highest biosorption capacity (80.49 mg/g) on a 100 mg/L of CR solution was achieved within a flow rate of 2.8 mL/min, bed depth of 4 cm and JS particles size of 50-100 mu m. The results of this study have shown that CR can be effectively adsorbed on JS. The breakthrough and exhaustion times decreased with increasing flow rate, decreasing bed depth, increasing influent CR concentration and increasing size particles. Thomas and Bohart-Adams models were successfully used for predicting breakthrough curves for CR removal different parameters. It was found the biosorption of CR on JS agreed very well with the Thomas model. Desorption was carried out with NaOH solution (0.1 N) as the desorbing agent, and reuse of JS for four cycles was investigated. (C) 2016 Elsevier Ltd. All rights reserved.