Research On Bauxite Desilication By Selective Grillding-aggregation Flotation

Aiming at efficient utilization of diaspore type bauxite with medium and low alumina-silica ratio, the bauxite desiliciation by beneficiation was studied. It is concluded that Al2O3of all sizes must be recovered in bauxite beneficiation, in which the key technology is the comprehensive recovery of both micro size resource and coarse intergrowth. Based on hydrophobic aggregation of combined colletors, a new processing technology of bauxite-selective grinding-aggregation flotation was investigated, and its mechanism was discussed.It was shown that the bauxite grinding products with alumina-silica ratio3-6exhibited a great difference not only in size distribution, but also in disintegration. Usually, bauxite with+0.074mm size after grinding is1-2higher in alumina-silica ratio than that of the raw ores, but the mineral particles in thus size is mainly intergrowth and its flotability was very poor. The adsorption of sodium oleate on diaspore surface was considerably higher than that on aluminosilicate surface and it exhibited a selective collection of diaspore. In this way, bauxite selective grinding-aggregation process was commonly suitable for bauxite with medium and low alumina-silica ratio.The same-phase aggregation between diaspore particles could be observed due to hydrophobic aggregation when sodium oleate was used as collector. The flotability of diaspore was positively correlated with the apparent size of hydrophobic aggregate. That is to say, the factors affecting aggregate apparent size could also affect the mineral flotability: sodium hexametaphosphate depresses diaspore flotation because it decreased the aggregate size; Both the aggregate size and flotability of diaspore were greatly promoted when increasing sodium oleate dosage, increasing flotation temperature and using combined collector consisting of sodium oleate, hydroximic acid and OLThe adsorption of sodium oleate on diaspore surface changed as a function of temperature which affected the flotation of diaspore. It could be observed that adsorption isotherm of sodium oleate on diaspore surface presents a typical S type consisting of three line segments under low temperature (15℃). The concentration of semi-micelle adsorption of sodium oleate was much higher than that of flotation. When the temperature was increased to32℃, the adsorption isotherm of sodium oleate turned to L type. The adsorption of sodium oleate in low concentration increased, resulting in the increases of aggregate size and flotability of diaspore correspondingly.The diaspore flotation and hydrophobic aggregation tended to appear in the area where surface tension of collector solution was low. A little hydroximic acid and surfactant OL could decrease the surface tension of sodium oleate solution and correlate with improvement the hydrophobic aggregation and flotation of diaspore, in which benzohydroxamic acid could increase the adsorption of sodium oleate on diaspore. So the combined collectors with sodium oleate dominating could be preliminarily selected out by using reagent surface tension as a criterion. A new combined collector with sodium oleate, benzohydroxamic acid and OL was developed and applied in bauxite desilication.The aggregation flotation performance of bauxite could be affected by such factors as collector combination and stirring intensity. Selective grinding-aggregation flotation process with combined collector KL was pretty suitable for bauxite desilication by beneficiation and satisfying technology index of bauxite with different alumina-silica ratio could be obtained. Bench-scale tests on bauxite from Shanxi was carried out and beneficiation index of concentrator alumina-silica ratio11.23and Al2O3recovery85.28%were obtained from a raw ore with alumina-silica ratio4.32. Industrial tests on bauxite from Zhongzhou showed that beneficiation index of concentrator alumina-silica ratio12.33and recovery88.74%could be obtained from a bauxite ore with alumina-silica ratio6. And for bauxite with alumina-silica ratio as low as4, index of concentrator alumina-silica ratio9.34and recovery79.15%could also be obtained. Selective grinding-aggregation flotation process has been applied in Zhongzhou Branch, Aluminum Corporation of China and has obtained good desilication performance for bauxite with alumina-silica ratio5.5and3.5. This process provided reliable quality raw materials for aluminium oxide production by Bayer’s method has been served as an effective way for alleviating high quality bauxite shortage.