Influence of diatomite calcination temperature on the purification of coking wastewater

As pretreatment or post-treatment for coking wastewater, two kinds of diatomites from Linjiang and Zhangjiakou in China were selected for the adsorption and purification of coking wastewater. The influences of diatomite calcination temperature on their properties and purification performance were studied during coking wastewater treatment. The feasibility of using the diatomite as a sorbent in coking wastewater treatment was also discussed. Energy dispersive spectroscopy results indicate that raw Zhangjiakou diatomite shows a higher organic content. The morphologies and crystal structures of both the diatomites do not significantly change before and after calcination. A decrease in carbon content was observed for both the diatomites after calcination. As to the color removal at 254 and 269 nm, Linjiang diatomite is particularly superior to Zhangjiakou diatomite whether the diatomites are calcined or not. For example, after calcination at 500℃, the removal of chemical oxygen demand achieves to 61.8% for Linjiang diatomite while it only reaches 30.3% for Zhangjiakou diatomite. In addition, the removal of ammonia nitrogen can achieve to 50.4% for Linjiang diatomite after the calcination. It is concluded that the diatomite involved can be used for the pretreatment and post-treatment of coking wastewater.