ABSTRACT Clay is one of natural resources in Indonesia, one of which there is in Province of Riau. Natural clay used in this study was taken from the village Cengar. Minerals found in the clays including from the group muscovite, kaolinite and quartz. Liquid coagulant was obtained through calcination process at a temperature of 700 °C for 1 hour and the leaching used 0.2 mol H2SO4, the te…