PRODUCTION OF SODIUM SILICATE AND SODIUM ALUMINATE FROM ALUM PRODUCTION WASTE

Industrial solid waste accumulation poses a great hazard for the environment. The aim of this work was the utilization of alum waste produced from the production of Alum {Al2(SO4)3} using kaolin to produce sodium aluminate and sodium silicate. This was carried out by the leaching of calcined Alum waste using several acids (H2SO4, HCl, HNO3) with different concentrations (2, 4, 6, 8 and 10 M) at 90 oC for 2 hrs to achieve maximum Al2O3 recovery followed by filtration process. The filtrate (concentrated Al2O3) was treated with NaOH to produce sodium aluminate while the precipitate (concentrated SiO2) was treated with NaOH to produce Sodium Silicate via two different processes. The first process was by fusing the precipitate with NaOH with ratio 1:1 to 1:5 (Solid: NaOH) at 60 oC followed by dissolving in water at 60 oC. The second process was by treating the precipitate with several NaOH concentrations (1, 2, 3, 4, 5 M) at 90 oC for varying times (1, 2, 3 hrs). Results showed that maximum Al2O3 recovery was achieved with 10M H2SO4 leaching at 90 oC for 3hrs (89.28 %) which is used to produce Sodium Aluminate. Sodium Aluminate solution was dried at 130-150 oC and analyzed using X-Ray diffraction (XRD). Sodium Silicate was produced with SiO2/Na2O weight ratio (WR) from 2.15 to 3.44 in the first process while was nearly 2 in the second process.