Coagulation of oil in water and the floating coagulated material
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The coagulation of oil in water is attractive for removal of oil from water. The coagulant consisting of sawdust (79.6 vol.%), bentonite (15.8 vol.%) and calcium hydroxide (4.7 vol.%) gives coagulation efficiency ≥ 94%. The oil content in the coagulated material, which floats on water, decreases with decreasing amount of added oil. It ranges from 69 to 81 vol.%, while the solid content ranges from 19 to 31 vol.%. The oil consists of strongly bonded oil (16 vol.% of the oil, with relative dielectric constant 32, due to interaction with the coagulant) and weakly bonded oil (with relative dielectric constant 2.0, same as that for the as-received oil). The solid part of the coagulated material exhibits relative dielectric constant 7.6 and 1.6 before and after 110°C drying respectively, due to decreased continuity after drying. The specific interfacial capacitance at the specimen-electrode interface decreases with decreasing water or oil content. Coagulation finishes in 45 s. The maximum amount of oil that 0.022 cm 3 /cm 2 coagulant can coagulate is 0.116 cm 3 /cm 2 . The minimum amount of oil (below which the coagulated material sinks undesirably) that can be coagulated by 0.022 cm 3 /cm 2 coagulant is 0.052 cm 3 /cm 2 .