Efficient adsorption of malachite green dye using novel reduced graphene oxide/β-cyclodextrin epichlorohydrin composite: batch and fixed-bed studies

Abstract

ABSTRACT A novel ternary composite (RGO-βCD-ECH) consisting of epichlorohydrin (ECH) cross-linked beta-cyclodextrin polymer (βCD-ECH) with reduced graphene oxide (RGO) as a carrier was synthesised and used for the removal of malachite green (MG) dye from water. The adsorption performance was systematically investigated in batch mode, and the optimised parameters were as follows: initial MG dye concentration 100 mg/L, solution pH 8.0, contact time 90 min, adsorbent dosage 0.4 g/L, and temperature 30°C. The adsorption data follow the Langmuir model (R2 = 0.998) and the maximum sorption capacity (qm) was 902.125 mg/g. The kinetic data of adsorption follows the pseudo-second-order kinetic model (R2 = 0.999). The positive value of ΔHo = 102.047 kJ/mol indicates the endothermic nature of the adsorption process. The effects of bed height (2–4 cm) and MG dye flow rate (5–15 mL/min) were investigated in the fixed-bed column study. The exhaustion time (te), breakthrough time (tb), and bed capacity (qbed) of the column increases with bed height increases, and the value decreases with flow rate increases. The most important feature of this adsorbent is it could efficiently and easily regenerate from the MG dye loaded composite with a negligible effect on percentage removal. These characteristics of these novel composites could exhibit a bright future in the application of MG dye removal from wastewater.