With the acceleration of urbanization and the rapid development of industry and agriculture, a large number of industrial wastewater containing heavy metal is produced. In this study we worked on industrial rejection. The method for removing heavy metals from industrial wastewater based on chemical precipitation method is proposed in this paper, which utilizes lime (CaO), limestone (CaCO3), and sodium hydroxide (NaOH). Research on gypsum (CaSO4, 2H2O) in byproducts resulted from precipitation is carried out based on thermal analyses, infrared spectra and XRD examinations. The characterization of the effluent showed that's very hard, rich in sulphate, chlorides, orthophosphate and in heavy metals. The results show that the examined chemical coagulants were all efficient in the removal of the studied metals (Cu, Cd, Fe, Co and Zn). The overall results indicate that the optimum pH for hydroxide precipitation of the studied metals is varied between pH 6.0 and 10.0. Since all effluent guidelines require an effluent pH between 7 and 8, the use of carbonate treatment is, therefore, recommended because its buffering capacity value is around pH 7. The analyzes carried out on the byproducts of treatment (FTIR, XRD, TGA/TDA) show that they are mostly composed of gypsum: calcium sulphate dihydrate (CaSO4·2H2O).

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