Evaluation of beet sugar processing carbonation sludge for the remediation of synthetic dyes from aqueous media

Abstract

Waste management is still one of the most significant problems faced by industry. Spent lime cake or carbonation sludge from cane or beet-sugar processing is a major problem for the sugar industries owing to its pollution, storage and disposal issues. The goal of this study was to evaluate beet sugar carbonation sludge (BCS) for use in separation of synthetic dyes from aqueous media. Methylene blue, a synthetic and toxic dye that is widely used in industry was selected as the model coloring agent. The BCS was analyzed by FT-IR, SEM, EDX, TGA, BET and BJH analyses. The adsorption system reached equilibrium after 240 min and followed pseudo-second-order kinetics. The efficiency was nearly constant in the range of pH 4.6-12.2, indicating that BCS can be effectively used for this purpose over a wide pH range. Adsorption efficiency increased with temperature and BCS dosage but decreased with MB concentration. Thermodynamic measurements indicated that the process was endergonic and endothermic. Maximum adsorption capacity and efficiency were 13.05 mg/g and 96.8%, respectively. The isotherm models, Langmuir, Freundlich and Temkin were employed to interpret the data. More than 75% of MB was desorbed using acetonitrile after three consecutive trials and BCS was shown to be re-usable for at least 3 cycles. This study clearly shows the potential use of BCS for the remediation of synthetic and toxic dyes from aqueous media.