Removal of toluidine blue by manganese/graphene coated titaniferous sand and optimization of decolouration process via Box-Behnken design

Abstract

An adequate modification of a titaniferous sand fraction by manganese/graphene coating (GMnTS) was carried out. Indeed, the surface of titaniferous sand (TS) with a particle size less than 100 μm was functionalized by chemical precipitation of manganese oxide on which were coated graphene oxide nano-sheets. Modified Hummer method was used to produce a stable suspension of graphene oxide. In this study, the adsorption affinity was tested using toluidine blue (BT) as an aquatic contaminant. According to the Langmuir model, GMnTS has an adsorption capacity about 12 times higher than that of unmodified titaniferous sand. This is a coating rate of about 0.73 ± 0.02 %. The response surface methodology based on Box–Behnken design was applied to optimize the linear and interactive effects of four factors (BT concentration, pH, solid/liquid ratio and KCl concentration) influencing the discoloration process by GMnTS.