The use of large quantities of synthetic dyes in the process industry mainly for colouring products has given rise to aqueous effluents containing high levels of this pollutant. Sugarcane bagasse, a by-product of sugar processing, was modified with benzoyl peroxide and sodium hydroxide independently. The unmodified and modified materials were characterized for their swelling ratio, pH of point zero charge, bulk density and FT-IR spectra. The comparative sorption capacities of the modified surfaces were studied using batch experimental protocol. The effect of initial dye concentration, contact time, adsorbent dosage, temperature, pH, ionic strength and desorption of dye from the adsorbents were investigated. The mercerized sugarcane bagasse (MSB) was the most effective adsorbent material, with equilibrium sorption (qReR = 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 the dye onto the modified surfaces decreases with increase in temperature and ionic strength. The 4% NaOH gave the best desorption of dye from the adsorbents. Kinetic studies showed that the experimental data obeyed the pseudo second-order reaction model. The Langmuir isotherm model with the highest RP2P values gave the best fit to the data from the adsorption of the anionic dye onto the modified surfaces. The thermodynamic results with ∆GPoP values of -12.42 to -4.16 KJ/mol for MSB and -15.13 to -7.55KJ/mol for BSB, showed the spontaneity and feasibility of the sorption process. The values 0.256-0.334 KJmol/K for ∆SPoP and -18.41 -10.17 KJ/mol for ∆HPoP, depicts the randomness of dye uptake by the modified surfaces at the solid-solution interface and exothermic nature of the sorption process respectively. This study has shown that MSB and BSB are effective sorbent materials for the removal of anionic dyes from waste effluents.

Keywords: sugarcane bagasse, congo red dye, adsorption, kinetics, thermodynamics