The interaction between microparticles and porous media, such as packed beds, has been investigated extensively over the past few decades due to both academic and industrial relevance. Examples include filtration of solids crystals from the mother liquor in the pharmaceutical and agrochemical industries; removal of fine particulates from micron scale fabricated surfaces in the electronic industry; release of particles from biological surfaces in the biotechnology sector; and transportation of contaminants in groundwater. One of the common fundamental issues is how to overcome the attractive interaction between the deposited particles and the surface of the porous media. This work is concerned with the utilization of a flowing liquid to remove deposited particles from a model porous medium.

Bergendahl and Grasso (1999) experimentally investigated the use of liquid shear to remove 1 micron polystyrene particles from a packed bed of glass beads and achieved ~50% removal at a shear rate of 100 s-1. Such a high shear leads to high pressure drops and in some cases damage to surfaces due to, for example, abrasion. In this work, nanoparticle suspensions have been used to assist the removal of microparticles from model porous media. The motivation behind this work is the research published by Wasan and Nikolov (2003) and Chengara (2004) who have shown that when nanoparticle suspensions are confined in for example a wedge region between an adhered microparticle and a surface, they exhibit particle structuring, which leads to a large repulsive structural disjoining pressure.

Experiments were perfomed with a HPLC system, which involved using DLVO theory to adhere micrparticles to glass beads inside a packed bed, under favourable depositon conditions. Varous nanoparticle suspension were then injected into the column at different flowrates and particle concentrations. The results showed that the structuring effect of confined nanofluids can aid in the removal strongly adhered microparticles from model porous media.