流动电位法研究高岭石胶体对包铝石英砂zeta电位的影响

STUDY ON EFFECT OF KAOLINITE COLLOIDS ON ZETA POTENTIAL OF Al OXIDE COATED QUARTZ WITH STREAMING POTENTIAL METHOD

为探讨采用流动电位法表征带电颗粒间相互作用的可行性,采用自制的流动电位测量装置测定了高岭石胶体流经包铝石英砂时zeta电位的变化(Δζ),研究高岭石与包铝石英砂之间的作用程度,考察了包铝程度、介质离子强度和离子种类对带电颗粒之间相互作用的影响。结果表明,可采用流动电位法表征不同尺寸的异电荷颗粒间的相互作用。随着石英砂表面包铝程度的增加和介质离子强度的降低,包铝石英砂的Δζ增加,说明其与高岭石之间的作用程度增加。含低价态离子的溶液中高岭石胶体与包铝石英砂的作用程度大于其在含有高价离子的溶液中。采用经典的DLVO理论计算得到的高岭石胶体与包铝石英砂间的作用能可以很好地解释高岭石对包铝石英砂表面电化学性质的影响,两种异电荷颗粒间的静电引力大小是决定高岭石与包铝石英砂间作用程度的关键因素。在静电力的作用下,高岭石通过电荷屏蔽作用和双电层重叠作用改变包铝石英砂的zeta电位。高岭石与包铝石英砂间的静电引力越大,高岭石对包铝石英砂表面电化学性质的影响越大。

To evaluate feasibility of using streaming potential method to characterize interactions between charged particles, change in zeta potential of A1 oxide coated quartz （ △ζ） induced by colloidal kaolinite was measured with a self-made streaming potential apparatus in studying extent of the interaction between kaolinite and A1 oxide coated quartz. The study also covered effects of A1 oxide coating degree of quartz, ionic strength and ionic species of supporting electrolyte on the interaction between A1 oxide coated quartz and kaolinite colloids. Results show that it is feasible to use the streaming potential method to characterize interactions between oppositely charged particles different in size. When kaolinite suspension flowed through the porous A1 oxide coated quartz package, the interaction between oppositely charged particles led to change of zeta potential, which increased with rising A1 oxide coating degree and declining ionic strength of electrolyte. These findings suggest that the increase in interaction between the oppositely charged particles with rising A1 oxide coating degree may be attributed to the increase in positive charge on the A1 oxide coated quartz and the decrease in ionic strength of the electrolyte as a result of the decrease in diffuse layers on the particles. The interaction between kaolinite and A1 oxide coated quartz was stronger in the solution containing monovalent ions than in the solution containing divalent ions, causing greater change in zeta potential of A1 oxide coated quartz in the former environment. The interaction energy between kaolinite and A1 oxide coated quartz can be calculated with the equation derived from the classic DLVO theory. The obtained data could be used to explain the effect of kaolinite on the electrochemical properties at the interface of kaolinite/A1 oxide coated quartz. The electrostatic attraction force between the oppositely charged particles was the key factor influencing the interaction between kaolinite and A1 oxide coated quartz. Under the effect of electrostatic attraction force, kaolinite induced change in zeta potential of the A1 oxide coated quartz through its effect of physical masking when depositing on A1 oxide coated quartz and the overlapping of the diffuse layers of electrical double layers on the oppositely charged particles. The higher electrostatic attraction between kaolinite and A1 oxide coated quartz, the stronger the influence of kaolinite on the electrochemical properties of the interface. Therefore, the streaming potential method can be used to characterize the interaction between charged particles. The findings in this study may be of some fundamental significance to the studies on the effects of micro-particles on surface electrochemical properties of the bulk soil or other large-scale porous materials during the migration process of colloidal particles and on strategies to reduce soil erosion in tropical and subtropical regions.