Recovery of Boron from Tincal Wastes

Boron ores are some of Turkey's most important underground riches. Tincal (Na2B4O7·10H2O), having the largest deposit, originally contains clay minerals such as illite and montmorillonite. One of the most important problems in refined borax production is separating tincal from the clay minerals, which are in a colloidal state in an aqueous solution and cannot be filtered. To separate clay particles, various additives are used as coagulants and cause both increasing production cost and borax loss. In this study, the reactor waste forming during borax production from tincal ore was dissolved in distilled water, CO2-saturated water, and SO2-saturated water to recover its B2O3 contents, to investigate dissolution kinetics, and to determine the filtration conditions in these dissolving media. The dissolution kinetics of tincal waste were investigated by choosing the temperature as a parameter, and it was found that activation energies and Arrhenius constants were 62.2 kJ mol-1 and 1.8 × 1010 for SO2-saturated water and 24.5 kJ mol-1 and 1.6 × 104 for CO2-saturated water, respectively. On the other hand, the effects of passing SO2 and CO2 gases through a tincal solution on spoiling the colloidal state of clay minerals were studied by using the temperature and stirring time for dissolution as parameters. It was seen that the colloidal state could be spoiled by passing SO2 or CO2 gases through the suspension. The filtration rate increased by increasing the temperature and stirring time for dissolution when SO2-saturated water was used, but filtration was difficult in CO2-saturated water and impossible in distilled water.