Effect of thermal regeneration of diatomite adsorbent on its efficacy for removal of dye from water

Reduction in adsorption capacities of adsorbents is limiting of its wider application for water treatment. In this study, we developed a new approach for recycling diatomite to be used adsorbent. The laser scattering particle size analyzer, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray and Brunauer–Emmett–Teller analysis were used to evaluate the structural characteristics of treated samples. The adsorption efficacy of raw and heated diatomite at 300, 600 and 900 °C for textile dyestuff removal from wastewater was investigated. The characterization results show insignificant changes except some deconstructions were occurred after treatment at 900 °C. The maximum adsorption capacities were obtained at pH 2 and adsorbent dosage of 4 g L ⁻¹ . The required time to reach the equilibrium was 30 min, and diatomite treated at 600 °C is acted as an excellent adsorbent. The kinetic studies were better described by the pseudo-second-order kinetic model. The isotherms experimental data showed that the adsorption of dye onto raw diatomite, DH300 and DH600 follows the Brunauer–Emmett–Teller isotherm model, but its adsorption onto DH900 conforms well to Freundlich isotherm model. Recycling of diatomite using thermal treatment was useful. At 600 °C which is considered the best regeneration temperature, the adsorbed dye was completely despaired, and around 73% was restored after three regeneration cycles.