Thermodynamic and kinetic studies for the adsorption of malachite green from textile water, using a low-cost natural material, diatomite

Abstract

Pollution by dyes is one of the main pollution of industrial effluents. In this research we examined Moroccan diatomite (DT) as a low cost adsorbent to remove one of these dangerous dyes, malachite green (MG). BET, SEM, pHpzc and XRD were used to assess the characterization of diatomite. The studies were carried out at different levels, of pH, diatomite mass and MG concentrations, with a temperature of 25°C. Equilibrium, kinetics and thermodynamic characteristics were also studied. Results show that the diatomite consisted of an integrated and nearly circular sieve plate with many small ordered pores, giving it a high specific surface area of 17.36 m2 g−1. The ideal pH was found to be 7, with a saturation period of 90 minutes. The results indicate that MG removal increased accordingly as pH increased and also as adsorbent mass increased. The results of the isotherms showed that the Langmuir model is the most adequate, while the adsorption of MG was better characterized by the monolayer. The maximum adsorption capacity obtained from Langmuir is about 22.17 mg. g−1 at 25°C. Kinetic studies were indicated as the pseudo-second-order and most adequate model. He also revealed that intra-particle diffusion was not the only rate-controlling step. The thermodynamic data concluded that the adsorption was endothermic, i.e., adsorption is more favorable at high temperatures. Research has confirmed the applicability of diatomite as an effective adsorbent and an inexpensive process for removing hazardous materials.