Important Role of Concave Surfaces in Deposition of Colloids under Favorable Conditions as Revealed by Microscale Visualization
Important Role of Concave Surfaces in Deposition of Colloids under Favorable Conditions as Revealed by Microscale Visualization
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DOI：
10.1021/acs.est.1c07305
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发表时间：
2022-04-05
影响因子：
11.4
通讯作者：
Xing, Baoshan
中科院分区：
文献类型：
--
作者：
Li, Tiantian;Shen, Chongyang;Xing, Baoshan
通过饱和水柱实验，系统地研究了1微米带正电的聚苯胶乳微胶(代表微塑性颗粒)在带负电的粗沙、玻璃微珠和土壤上的沉积情况，发现孔速在4.9×10~(-5)~8.8×10~(-4)m/S范围内存在一个临界值，在该临界值以下，胶体附着效率(AE)随带负电的粗沙、玻璃微珠和土壤的孔速增大而增大。随着PWV的增加，声发射的增加归因于胶体的增强输送和随后在粗糙收集器表面凹陷位置的附着。超过阈值后，随着PWV的进一步增加，AE值降低，这是因为凸起的位置不能用于胶体附着。通过用魏尔斯特拉斯-曼德尔布罗特方程模拟粗糙表面，扩展的Derjaguin-Landau-Verwey-Overbeek(XDLVO)相互作用能计算和扭矩分析表明，即使在有利的条件下，粘附力矩也可以降低到与流体动力矩相当或更小的水平。有趣的是，扫描电子显微镜实验表明，在所有离子强度(ISS)下，堵塞发生在凸起部位(例如，即使当胶体-胶体相互作用具有吸引力时)，而在凹面部位，堵塞和成熟(即附着的胶体有利于后续附着)分别在低ISS和高ISS下发生。据我们所知，由于收集器表面形貌的变化，我们的工作第一次显示出在高ISS下存在阻塞和成熟共存的现象。
This study conducted saturated column experiments to systematically investigate deposition of 1 mu m positively charged polystyrene latex micro-colloids (representing microplastic particles) on negatively charged rough sand, glass beads, and soil with pore water velocities (PWV) from 4.9 x 10-5 to 8.8 x 10-4 m/s. A critical value of PWV was found below which colloidal attachment efficiency (AE) increased with increasing PWV. The increase in AE with PWV was attributed to enhanced delivery of the colloids and subsequent attachment at concave locations of rough collector surfaces. The AE decreased with further increasing PWV beyond the threshold because the convex sites became unavailable for colloid attachment. By simulating the rough surfaces using the Weierstrass-Mandelbrot equation, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) interaction energy calculations and torque analysis revealed that the adhesive torques could be reduced to be comparable or smaller than hydrodynamic torques even under the favorable conditions. Interestingly, scanning electron microscopic experiments showed that blocking occurred at convex sites at all ionic strengths (ISs) (e.g., even when the colloid-colloid interaction was attractive), whereas at concave sites, blocking and ripening (i.e., attached colloids favor subsequent attachment) occurred at low and high ISs, respectively. To our knowledge, our work was the first to show coexistence of blocking and ripening at high ISs due to variation of the collector surface morphology.