The separation of oily water using low-cost natural materials: Review and development

This paper reviewed the recent progress on a number of important natural/biomass materials (fibers, leaves, woods, nutshells, algae, and sands, etc.) for the separation of oily water mixture/emulsions. Experiments were conducted with desert pristine sand samples, which were collected, sieved, characterized and tested for the separation of two surfactant-stabilized oil in water (O/W) emulsions in a simple cross-flow sand bed filter under the simulated natural gravity. The wettability of the sand samples was checked through contact angle measurements. The morphology of sands was characterized with SEM/EDX and FTIR. Experimental results revealed that natural sand filtration is a promising technology with the characteristics of: 1) a surface of superhydrophilicity and underwater superoleophobicity; 2) sands bed achieved separation efficiency and flux comparable or higher than commercial microfiltration membranes under natural gravity conditions, and 3) the separation efficiency and flux of the sand bed are relatively stable with respect to the operation parameters. This technology is technically feasible, low-cost, and environmental-benign and can play an important role in the practical applications.