Green synthesis and influence of calcined temperature on the formation of novel porous diatomite microspheres for efficient adsorption of dyes

The novel porous diatomite microspheres were prepared by spray drying and subsequent calcination. Effects of calcined temperatures on the microstructure, specific surface area and adsorption properties of the microspheres were investigated systematically. Results showed that the porous microspheres exhibited spherical characteristic with both macropore and mesoporous features. The phases of the microspheres kept amorphous at 800 °C and crystallized into crystobalite at 1000 °C. The microspheres after calcined at 600 °C showed removal efficiency of 95.6% with the dosage of 20 g/L under the starting concentration of 100 mg/L. The adsorption process of methylene blue onto microspheres followed the pseudo-second-order kinetic model and Langmuir equation. The dye solutions could be easily filtrated by the microsphere layers and became colorless. It suggested that the porous diatomite microspheres had potential application in dyeing wastewater filtration and adsorption treatment.