The adsorption of dyes from aqueous solution using diatomite

Raw diatomite was calcined at 450 °C for dyes removal from aqueous solution. SEM and FTIR analysis show that the raw diatomite contains organic impurities, which are removed after the calcination. The impurities removal decreases the specific surface area and increases the average pore diameter of raw diatomite, while improves its adsorption capability of dyes. The adsorption isotherm and kinetics experiments of methylene blue onto calcined diatomite were then carried out to investigate the adsorption property. It shows that the adsorption capacity of methylene blue is about 50 mg/g. The adsorption isotherm was fitted by the Langmuir, Freundlich and Redlich-Peterson models, which reveals that the Redlich-Peterson isotherm is the best one. Two kinetic models, pseudo-first order and pseudo-second order, were rearranged for expediently investigating the adsortpion mechanisms. Fitting results show that the pseudo-first-order model is better in describing the adsorption process.