Sorption of Congo red Dye from Aqueous Solution by Mercerized and Benzoylated Sugarcane Bagasse: Isotherm, Kinetic and Thermodynamic Studies

Abstract

The use of large quantity of synthetic dye in process industries to colour products amongst other things has given rise to aqueous effluents containing high level of this pollutant. This paper therefore evaluates the use of isotherm, kinetic and thermodynamic to study the sorption capacities of congo red dye by mercerized sugarcane bagasse (MSB) and benzoylated sugarcane bagasse (BSB) in aqueous solution using batch experimental protocol. Data obtained show that MSB was the most effective adsorbent material, with equilibrium sorption (q_e = 13.64 mg/g) after 50 minutes. The optimum pH and dosage for dye uptake were 3.0 and 3.5 g respectively. Sorption of dye by the modified surfaces decreases with increasing temperature and ionic strength.  The 4% NaOH presented the best desorption of dye on the adsorbents. Kinetic studies showed pseudo second-order model fit for the experimental data. Adsorption of the anionic dye on the modified surfaces fits the Langmuir isotherm model based on the R² values. Thermodynamic results showed ∆G^o values (-12.42 to -4.16 KJ/mol) for MSB and (-15.13 to -7.55KJ/mol) for BSB, consistent with the spontaneity and feasibility of the sorption process. The uptake of dye by the modified surfaces depicts a random nature at the solid-solution interface and showed that the sorption is exothermic as evidenced by value (0.256-0.334KJmol/K) and (-18.41 to -10.17 KJ/mol) for ∆S^o and ∆H^o respectively. The results present MSB and BSB as effective sorbent materials for removal of anionic dye from waste effluents.