Optimization of Removal of Calcium Ions Forming During Synthesis of Boric Acid from Ulexite Ore by Using Ion Exchange Resin

Ulexite ( Na 2 O·2CaO·5B 2 O 3 ·16H 2 O) is one of the most important raw materials for boric acid, synthesized by dissolving the ore in an acid solution. Since ulexite ore was dissolved in a phosphoric acid solution, the final solution included boric acid (H 3 BO 3 ), sodium dihydrogen phosphate [NaH 2 PO 4 ], and calcium dihydrogen phosphate [Ca(H 2 PO 4 ) 2 ] . The presence of several ions in the solution causes separation problems for boric acid. This study includes a special separation step to increase the purity of the boric acid that is synthesized from the dissolution of ulexite ore in phosphoric acid. For this purpose, c alcium ions in the final solution were removed using Dowex HCR-S cationic ion exchange resin. Additionally, the Taguchi optimization method was employed to monitor the removal of calcium ions . The design of experiments included an orthogonal array technique in L 9 array for three parameters with three different values; reaction temperature (12 o C, 25 o C, 40 o C), stirring rate (250 rpm, 300 rpm, 350 rpm), and the amount of resin material (10% wt., 30% wt., 50% wt.). The results of the calculations revealed that the optimum values of temperature, stirring rate, and amount of resin are 12 o C, 350 rpm, and 50% wt., respectively. The amount of calcium removed under optimum conditions was found as 79.49%.