孔隙空间对聚苯乙烯胶体滞留与释放的影响

为加深孔隙空间对胶体运移影响的认识,在不同pH与离子强度下,研究了胶体在经酸洗或水洗后的玻璃珠或石英砂中的迁移行为。结果表明:粒径相同的玻璃珠与石英砂(0.45~0.60mm)相比,形状一致的玻璃珠形成的孔隙空间(孔隙率0.38)小于石英砂(0.45)。酸洗与水洗后的玻璃珠表面成分变化不大(0~0.6%),经酸洗的介质后能提供更多有利吸附位点。在高pH(10)环境下,石英砂经酸洗或水洗后,胶体滞留量增大(72.1%和69.2%)。提高溶液pH到10后出现的胶体吸附增加,是颗粒接触点、非流动区或低流速区和涡流区滞留等孔隙空间滞留机制引起的,用DLVO理论无法解释。在离子强度为0.001mol/L或0.05mol/L环境下,酸洗石英砂中胶体滞留量比酸洗玻璃珠的分别高16.3%和28.0%,表明介质孔隙空间增大可加强颗粒接触点、非流动区或低流速区和涡流区滞留,然而优先流能够削弱孔隙空间滞留机制对胶体的滞留。此外,超纯水解吸时仅使少量胶体(3.9%)从玻璃珠与石英砂介质的孔隙涡流区中解吸出来,表明涡流区对胶体的保留不是胶体滞留在介质中的主要机制。

Impacts of Pore Scale on Retention and Release of Polystyrene Colloid

In order to understand about the impact of pore scale on colloid migration more deep, migration processes of colloid in acid-washed glass beads/quartz, Milli-Q-washed glass beads/quartz were compared under different pH and ionic strength. Results showed that the pore scale of glass beads with the same shape (porosity 0.38) was smaller than that of quartz sand with various shapes (porosity 0.45), although the glass beads and quartz sand had a uniform particle size (0.45~0.60 mm). The surface components of glass beads changed at a very small range from 0 to 0.6% after acid washing and Milli-Q washing. The acid-washed media could provide more favorable adsorption sites. The colloid retention of quartz sand increased after the acid washing or Milli-Q washing(72.1% and 69.2%, respectively) when the pH of the solution raised to 10. The enhancement of adsorption was induced by pore scale retention mechanism, such as retention in particle contact points, non-flowing area or low velocity area and eddy current area, which could not be explained by the DLVO theory. The retention of colloid in the acid-washed quartz sand was about 16.3% and 28.0% higher than that of the acid-washed glass beads under the environments of ion strength of 0.001 mol/L and 0.05 mol/L, respectively, which implied that increased pore scale enhanced colloid retention in particle contact points, non-flowing area or low velocity area and eddy current area. However, occurrence of preferential flow in soil columns impaired the retention of colloid in pores greatly. In addition, only a small parts of colloids (<3.9%) was desorbed from eddy zones in the glass beads and the quartz sand after using ultra-pure water, indicating that the colloid retention in the eddy zones wasn''t the dominant mechanism.