Determination of the optimum conditions for the boric acid extraction from colemanite ore in HNO3 solutions

In this paper, Taguchi method was applied to determine the optimum boric acid extraction from colemanite (2CaO·3B3O3·5H2O) ore in nitric acid solutions. An orthogonal array (OA9) experimental design that allows to investigate the simultaneous variations of four parameters (particle size, acid concentration, stirring speed and reaction time) having three levels was employed to evaluate the effects of experimental parameters. Performance measure analysis was followed by performing a variance analysis, in order to determine the optimum levels and relative magnitude of the effect of parameters. Because the desired characteristic for response has been maximum boric acid extraction, Taguchi’s ‘the larger the better’ performance formula was used. The optimum conditions were found to be particle size, 2.4 mm; acid concentration, 2.2 M; stirring speed, 500 rpm; reaction time, 11 min; solid-to-liquid ratio, 0.25 and reaction temperature, 94 ◦C. Under these optimum conditions, it was found that the boric acid extraction from colemanite ore was 99.66%.