Bleaching of red clay using Na2S2O4 and NaBH4 in acidic solution Bui Thi Hoa, Le Hong Phuc, Nguyen Quan Hien, Nguyen Thi Nhat Quynh, Dao Hiep Thanh, Tran Tan Nhat and Bui Xuan Vuong E3S Web Conf., 496 (2024) 01003 Published online: 12 March 2024 DOI: 10.1051/e3sconf/202449601003