Comprehensive batch and continuous methyl orange removal studies using surfactant modified chitosan-clinoptilolite composite

Abstract

In the present study, the adsorption of methyl orange (MO) onto surfactant modified chitosan clinoptilolite composite (SMCSCL) from aqueous solution was investigated in batch and continuous adsorption systems. The characterization techniques of FTIR, FE-SEM, XRD, TGA and N2 adsorption–desorption were evaluated to find the functional group, morphology, crystalline structure, thermogravimetry and surface area of SMCSCL. The effect of process parameters including adsorbent dosage, contact time, solution pH and temperature on dye removal were studied in batch operation. Maximum dye adsorption at the optimum conditions was obtained as a loading of 0.22 g/20 mL, solution pH of 3.5, contact time of about 10 min and temperature of 30 °C. Thermodynamic studies showed that the adsorption process of MO onto SMCSCL was spontaneous, physical and unfavorable with the temperature rise. To evaluate kinetic data, the pseudo-second-order model showed a better correlation with the experimental data. The equilibrium data was in better agreement with the Toth isotherm model. Also, the Langmuir monolayer capacity was obtained 14.5 mg/g at the optimized operation parameters. The continuous adsorption experiments were carried out in the fixed-bed column and the operating conditions as influent flow rate (4.5–7.5 mL/min) and the bed depth (1–1.4 cm) on methyl orange adsorption. Maximum adsorption capacity in continuous experiments was obtained 32.09 mg/g at the influent flow rate of 4.5 mL/min and the bed depth of 1.4 cm. Thomas and Yoon-Nelson models provide the best description of the breakthrough curve and fixed-bed column hydrodynamic. Also, the bed depth service time (BDST) model can be practical to the prediction of breakthrough behavior and its scale-up. It was concluded that the adsorption of MO onto SMCSCL from aqueous solution in batch and continuous operation could be used effectively due to their applicability at the low-temperature range.