Experiments in use of bentonite for energy recovery of used oils Mihai Dragne, Elena Pop, Cristina Ileana Covaliu, Ecaterina Matei and Ionel Pîşă E3S Web Conf., 112 (2019) 04009 Published online: 20 August 2019 DOI: 10.1051/e3sconf/201911204009