Study On Wet-Way Purification Of Bentonite By Hydrocyclone And Its Mechanism

Bentonite is one of the clay mineral with higher value and development potential together with a growing market demand. This paper aimed at the abundant bentonite resources of Guangxi were in a low level of development and utilization due to its poor quality, putting forward that using hydrocyclone for wet purification experiment research of bentonite, in order to provide some references for its development and utilization direction. In this paper, the natural bentonite mineral of Binyang in Guangxi province was purified by using hydrocyclone, the influence of structural parameters and operating parameters of hydrocyclone together material properties on purification effect of bentonite has been studied. The main original conclusions of the work are drawn as following parts.(1) In the wet-way purification process of bentonite, both of the montmorillonite content in overflow product and the slurry concentration in underflow product could be improved, meaning that hydrocyclone had the function of separation and dehydration.(2) The change of feed concentration affected the density and viscosity of bentonite slurry, thus to affect the purification effect. Lower feed concentration had little effect to the result of the purification. When feed concentration came to10%～20%, the content and recovery of montmorillonite in overflow were both enhanced significantly. Under the experimental condition, the suitable feed concentration ranged from10%to20%.(3) The content of montmorillonite in overflow increased with a increasing of the apex diameter while the recovery of montmorillonite in overflow decreased. When feed concentration was10%, the suitable apex diameter ranged from4mm to6mm. When feed concentration was15%, the appropriate apex diameter ranged from6mm to8mm.(4) With the increasing of feed pressure, coarse gangue minerals were given lager centrifugal force as a result more of them entered into underflow, while fine bentonite minerals were affect only a little. The effect of purification was improved with the increasing of feed pressure. There is interaction between feed concentration, apex diameter and feed pressure. The results indicated that the optimal test conditions were as that feed concentration, apex diameter and feed pressure were15%,6mm and0.35MPa respectively. Under the optimal condition, the content and the recovery of montmorillonite in overflow were80.03%and50.16%, respectively.(5) Adding (NaPO3)6and Na2CO3had little effect on the content of montmorillonite in overflow but had an evidently effect on the recovery and the solid yield of montmorillonite in overflow. Compared with that of without chemical reagents, when adding6%(NaPO3)6the recovery and solid yield of montmorillonite in overflow were increased12.31%and11.74%, respectively. And when adding6%Na2CO3the recovery and the solid yield of montmorillonite in overflow were increased14.44%and13.81%, respectively.(6) The sodium modification of purified bentonite was carried out. The results indicated that the impact order of the influence factors on the sodium modification was as follow:the amount of Na-modified agent> the slurry concentration> the conversion time> the conversion temperature. The results showed the optimal conditions were that:the amount of Na2CO3was3%, the slurry concentration was5%, the conversion time was90min, the conversion temperature was50℃. The Na-modified bentonite products achieved the standards of precision casting bentonite.(7) The properties of bentonite were learned by physicochemical properties test, SEM analysis and XRD analysis. The properties were as follows:compared with raw bentonite, the physicochemical properties of purified bentonite was significantly improved. The particles size were smaller and the structure was more loose. The layer distance of montmorillonite was decreased slightly, while the amout of impurity minerals were reduced markedly.(8) The process mechanisms of bentonite purified by hydrocyclone when adding chemical reagents was studied through SEM analysis, XRD analysis, viscosity test and sedimentation characteristics test. The results indicated that adding chemical reagents could improve the viscosity and sedimentation characteristics of bentonite slurry, then led to an increase of recovery and productivity of montmorillonite in overflow.