非利条件下胶体在砂土中的迁移和吸附.docVIP

 Transport and deposition of colloids in sand porous media under unfavorable chemical conditions# 5 10 15 20 25 30 35 40 45  Abstract: This study examines the morphology of colloid deposition onto rough surfaces under unfavorable conditions via theoretical analysis and laboratory experiments. Saturated column experiments were conducted with bacteria- and virus-sized latex particles and various collectors (sand and glass beads) at different ionic strengths and flow rates. A three-step procedure was used for colloid retention and release, following dissection of the columns to determine depth profiles of retained colloids. Results show that (i) colloids deposited in secondary minima mainly reside aside the asperities (up gradient of them with respect to flow direction) and these deposited colloids can be released by reduction of solution ionic strength but are relatively insusceptible to effect of hydrodynamics; (ii) colloids deposited in primary minima mainly reside atop the asperities and the deposited colloids cannot be released by changing solution ionic strength but are subjected to the influence of flow velocity; (iii) surface roughness not only favors colloid deposition in primary minimum via decreasing energy barrier but also increases secondary-minimum deposition because colloids associated with secondary minima can reside aside asperities and the asperities increase dominance of adhesive over hydrodynamic drag torques. Our study indicates that it is critical to combining mechanical (e.g., increase flow rate) and chemical (e.g., decrease solution ionic strength) methods for efficient particle removal, which is required in many industrial and environmental cleaning processes (e.g., cleaning of semiconductor surfaces and remediation of contaminated soil). Keywords: soil science; colloid; transport; deposition; porous media 0 Introduction A thorough understanding of colloid deposition mechanisms is essential for protecting groundwater from being contaminat