Study on Purification Diatomite with nitric acid by Thermal Closed System Meng Kuang, Ping Wang, Qiu-yun Luo, Hu Peng, Yu-hong Wei and Zhong-hua Wei MATEC Web Conf., 67 (2016) 06050 Published online: 29 July 2016 DOI: 10.1051/matecconf/20166706050