Kinetics of coupled primary- and secondary-minimum deposition of colloids under unfavorable chemical conditions
Kinetics of coupled primary- and secondary-minimum deposition of colloids under unfavorable chemical conditions
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DOI：
10.1021/es070210c
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发表时间：
2007-10-15
影响因子：
11.4
通讯作者：
Jin, Yan
中科院分区：
文献类型：
--
作者：
Shen, Chongyang;Li, Baoguo;Jin, Yan
本研究通过理论分析和实验室柱实验探讨了不利条件下胶体保留的沉积/释放机制。利用麦克斯韦方法估计了初级最小沉积和次级最小沉积的耦合效应。理论分析表明，二次能量最小值在胶体沉积中起主导作用，即使是纳米级颗粒（如20 nm），而当扩散是主导过程时，大颗粒（如1000 nm）很少发生初级最小值沉积。采用聚苯乙烯乳胶颗粒（30 nm和1156 nm）和洁净砂在不同溶液离子强度、pH恒定为10、流速为0.0012 cm/s的条件下进行三步色谱柱实验。实验结果证实，小的胶体也可以在次级极小值中沉积。另外涉及流动中断的柱实验进一步表明，当二次能最小值与平均布朗值相当时，沉积在二次能井中的胶体可以自发地释放到体溶液中。动能。实验碰撞效率与麦克斯韦模型的预测结果一致，但与由界面力边界层近似计算的理论值不同。我们提出了一种先验分析方法来估计碰撞效率，考虑到初级和次级最小沉积，并建议在运输模型中必须考虑胶体（如病毒和细菌）沉积的可逆性，以便准确预测它们在地下环境中的传播时间。
This study examines the deposition/release mechanisms involved in colloid retention under unfavorable conditions through theoretical analysis and laboratory column experiments. A Maxwell approach was utilized to estimate the coupled effects of primary- and secondary-minimum deposition. Theoretical analysis indicates that the secondary energy minimum plays a dominant role in colloid deposition even for nanosized particles (e.g., 20 nm) and primary-minimum deposition rarely happens for large colloids (e.g., 1000 nm) when diffusion is the dominant process. Polystyrene latex particles (30 and 1156 nm) and clean sand were used to conduct three-step column experiments at different solution ionic strengths, a constant pH of 10, and a flow rate of 0.0012 cm/s. Experimental results confirm that small colloids can also be deposited in secondary minima. Additional column experiments involving flow interruption further indicates that the colloids deposited in the secondary energy well can be spontaneously released to bulk solution when the secondary energy minimum is comparable to the average Brownian. kinetic energy. Experimental collision efficiencies are in good agreement with Maxwell model predictions but different from the theoretical values-calculated by the interfacial force boundary layer approximation. We propose a priori analytical approach to estimate collision efficiencies accounting for both primary- and secondary-minimum deposition and suggest that the reversibility of colloid (e.g., viruses and bacteria) deposition must be considered in transport models for accurate predictions of their travel time in the subsurface environments.