Coagulation of Oil in Water Using Sawdust and Bentonite and the Formation of a Floating Coagulated Material

The coagulation of oil in water is potentially cost-effective for removing oil from water. A coagulant consisting of sawdust (79.6% by volume), bentonite (15.8% by volume), and calcium hydroxide (4.7% by volume) gives coagulation efficiency of $\ge 94\%$ and coagulation time of $\le 45\mathrm{s}$. The resulting coagulated material (a semisolid) floats on water. Its oil (liquid) content, which decreases with a decreasing amount of oil originally present in the water, ranges from 69–81% by volume. This paper provides the first identification of multiple forms of oil in a coagulated material that is made from a single form of oil. The oil consists of strongly bonded oil (16% by volume, with relative dielectric constant 32) and weakly bonded oil (84% by volume, with the same relative dielectric constant of 2.0 as the original oil). The maximum and minimum volumes of oil per unit area that can be coagulated by $0.022{\mathrm{cm}}^3/{\mathrm{cm}}^2$ of coagulant volume per unit area are 0.116 and $0.052{\mathrm{cm}}^3/{\mathrm{cm}}^2$, respectively. Below the minimum amount of oil, the coagulated material sinks in water, thus hindering oil removal.