Trung, D. 2020. Research application of K2CO3 activated coal coal and processing by HNO3 from cake shoulder to process Methylene Blue color. VNUHCM Journal of Earth Science and Environment. 4, 1 (Jun. 2020), 170-177. DOI:https://doi.org/https://doi.org/10.32508/stdjsee.v4i1.534.