Environmental Engineering Reference
In-Depth Information
calcium carbonate powder commercially available as Precarb 100 is inherently needle-
shaped but hydrophilic. To create an oleophilic surface, the powder is modiied with ste-
ric acid, which absorbs to the calcium carbonate surface via carboxyl group complexing
calcium ions and orienting the alkyl chain away from the surface. Steric acid modiication
and calcium stearate precipitation also generates a hierarchically rough surface morphol-
ogy leading to superhydrophobicity (Figure 7.6). The resulting powder when mixed with
a diesel-water mixture selectively absorbs the hydrocarbon, leading to clumps of solid
material that can be easily removed from the water (Figure 7.7). The two main advantages
(a)
(b)
100 nm
100 nm
(d)
(c)
100 nm
1 µm
FIGURE 7.6
SEM images of the porous structure of Precarb 100 calcium carbonate. (a, b) Before the treatment with steric
acid; (c, d) after treatment with steric acid.
(a)
(b)
(c)
FIGURE 7.7
Oil-water mixture (a) before powder addition; (b) right after powder addition; and (c) after separation.
