Fluoride Leaching from Plaster Board Waste: Effect of Sodium, Calcium and Aluminium Electrolytes

摘要

Plaster board waste generated from industries, usually contains major proportion of calcium as calcium sulfate. In addition, fluoride is remarkably one among the constituents of this waste material. Experimental studies were conducted to determine the fluoride leaching as a function of particle size, pH of leaching solvent (distilled water), L/S ratio, electrolytes of sodium, calcium and aluminium, electrolyte mixture, acids (as leaching solvent) and temperature. It was explored that one gram of plaster board waste contains 18.54 mg of fluoride, 3560 mg of Ca2+ (as CaC03) and 5515 mg of dissolved solids. High leaching of 3.72 mg F per liter was studied at pH 6.02 with Ca2+ and TDS contents of 1050 mg L-l and 1640 mg L-l respectively. The influence of fluoride leaching by sodium phosphate recorded a high value of 12.75 mg L-l with no detectable amount of calcium ions. The leaching mechanism enabled due to the exchange between Na+ and Ca2+ was corroborated by XRD and FE - SEM studies. The leaching rate as a consequence of shaking and stirring dynamics was also investigated at different conditions. The author Sivasankar VENKATARAMAN thank JSPS for the award of the fellowship (ID No. 16544).