Isothermal, kinetic and thermodynamic studies on basic dye sorption onto tartaric acid esterified wheat straw

Abstract

In this paper, a new cation sorbent, which bore carboxyl and hydroxyl groups of tartaric acid (TA) derived from esterified wheat straw (EWS), was originally prepared by solid phase thermochemistry method. The isotherm, kinetics and thermodynamics of basic dye sorptions from aqueous solution onto EWS were investigated for the first time. Two basic dyes, methylene blue (MB) and crystal violet (CV) were selected as sorbates. The isothermal data correlated with the Langmuir model better than the Freundlich model. The maximum sorption capacity (Qm) of EWS for MB and CV was 129.87 and 112.36
mg/g, respectively. The equilibriums of dye sorptions were respectively reached about 13 and 18 h for MB and CV. The sorption processes could be described by the pseudo-second-order kinetic model and there were two intra-particle diffusion steps in the dye sorption processes. The thermodynamic study indicated that the dye sorptions were spontaneous and endothermic in nature.