Production of Gypsum from Clam Shells and Waste Acid Recovered from End-of-Life Lead Acid Batteries

Abstract

Gypsum exists in the Dihydrate (CaSO₄ 2H₂O), Hemihydrate (CaSO₄. ½H₂O) and the Anhydrite (CaSO₄) forms. The exploitation of the natural rock form deposit of gypsum is on the increase, necessitating the need to find alternative and efficient sources of gypsum so as to sustain all the industries dependent on gypsum as raw material. This work investigates the production of gypsum from clamshells and waste sulphuric acid from end-of-life car batteries. Clamshells obtained from the Volta Region of Ghana were calcined at a temperature of about 1150 ËšC with a view to producing CaO which was pulverised to particle size of 87.4 % passing 106 μm. Samples of the Pulverised Clam Shells (PCS) were then reacted with five different concentrations of the Waste Battery Acid (WBA). The reaction was observed to be very exothermic; a temperature of 101 ËšC was obtained for the 6.5 M concentration of WBA. The resulting mixture was filtered and an XRD analysis was performed on the oven dried residue to ascertain its composition. The findings from the work evaluated that the purity of CaO produced is dependent on the calcination temperature and time; this is evident in the mass of the dried residue obtained to be an average of 134 grams and the peaks of SiO₂ from the XRD analysis. The CaCO₃ peaks also indicated that the reaction between PCS and WBA was incomplete. Conclusively, the results from the XRD analysis showed peaks of the three forms of gypsum that was successfully produced.