Process for preparing detergent builder Zeolite-A from Kimberlite tailings

A process for preparing detergent builder Zeolite-A from Kimberlite tailings generated as solid waste during diamond mining and having chemical constituents in the range of SiO2 30-32%, Al2O3 2-5%, TiO2 5-8%, CaO 8-10%, MgO 20-24%, and Fe2O3 5-11% and a loss on ignition of 13-15%, the process comprising:

• (i) passing Kimberlite tailing through a 60 mesh screen and treating the sieved fraction with 1 to 10 N hydrochloric or nitric acid at temperature in the range of 75 to 100° C. for a period in the range of 1 to 6 hours to remove acid soluble impurities,
• (ii) recovering acid treated Kimberlite tailings after washing with demineralized water until free from acid and digesting acid treated Kimberlite tailing having a chemical composition in the range of SiO2 73-77%, R2O3 3-4%, TiO2 10-13% and CaO+MgO 0.5-1.0% and loss on ignition of 5-6% with an alkali comprising a sodium hydroxide solution having concentration in the range of 6 to 10 percent at 95-200° C. for a period of 1 to 6 hours either in an open vessel or in a closed system to prepare sodium silicate having 13-21% SiO2 and 4-7% Na2O with molar ratio of SiO2:Na2O=2.8-3.3,
• (iii) obtaining a sodium silicate solution wherein a Na2O/SiO2 mole ratio is in the range of 0.5 to 0.8 and a H2O/Na2O mole ratio is in the range of 30 to 40 by adding sodium hydroxide to the sodium silicate,
• (iv) dosing a sodium aluminate solution, prepared separately by dissolving aluminum trihydrate in sodium hydroxide solution at 70 to 100° C. so as to obtain a Na2O/Al2O3 mole ratio in the range of 1.8 to 2.2 and H2O/Na2O mole ratio in the range 25 to 30, to the sodium silicate solution under continuous stirring at ambient temperature in the range of 25 to 40° C. and in a specified period in the range of 30 to 120 minutes to form aluminosilicate gel, comprising 3.2 ±0.1 Na2O:
• 2.0±0.2 SiO2:
• Al2O3:
• 105±10 H2O,
• (v) heating the aluminosilicate gel at in a temperature in the range of 70 to 100° C. for a time in the range of 1 to 5 hours, thereby converting the amorphous aluminosilicate gel to crystalline Zeolite-A in a product slurry,
• (vi) cooling the product slurry to <50° C. and separating the Zeolite-A product by filtration,
• (vii) washing the wet cake of the product with demineralized water until a pH of the wash water is between 11 and 10.5, and
• (viii) drying the washed wet cake containing 40 to 50% moisture in a dryer at 110° C. for 5 to 7 hours followed by pulverizing the dried wet cake using a micro or impact type pulverizer to obtain Zeolite-A as a fine powder.