Green technological approach to synthesis hydrophobic stable crystalline calcite particles with one-pot synthesis for oil-water separation during oil spill cleanup

Green technological approach to synthesis hydrophobic stable crystalline calcite particles with one-pot synthesis for oil-water separation during oil spill cleanup

The process of separating oil and water from oil/water mixtures is an attractive strategy to answer the
menace caused by industrial oil spills and oily wastewater. In addition, water coproduced during hydrocarbon
exploitation, which can be an economic burden and risk for freshwater resources, can become an
important freshwater source after suitable water-oil separation. For oil-water separation purposes,
considerable attention has been paid to the preparation of hydrophobic-oleophilic materials with modified
surface roughness. However, due to issues of thermodynamic instability, costly and complex methods as
well as lack of ecofriendly compounds, most of hydrophobic surface modified particles are of limited
practical application. The study presents a facile procedure, to synthesize crystalline particles of calcite,
which is the most stable polymorph of CaCO3 from industrial CaCO3 using oleic acid as an additive in a onepot
synthesis method. The XRD results show that the synthesized particles were a well-crystallized formof
calcite. The FTIR results reflect the appearance of the alkyl groups from the oleic acid in synthesized particles
which promotes the production of calcite with ‘rice shape’ (1.64 mm) (aggregated by spherical
nanoparticle of 19.56 nm) morphology with concomitant changes in its surface wettability from hydrophilic
to hydrophobic. The synthesized particles exhibited near to super hydrophobicity with ~99% active
ratio and a contact angle of 143.8�. The synthesized hydrophobic calcite particles had an oleophilic nature
where waste diesel oil adsorption capacity of synthesized calcium carbonate (HCF) showed a very high
(>99%) and fast (7 s) oil removal from oil-water mixture. The functional group of long alkyl chain including
of C]Obounds may play critical roles for adsorption of diesel oils. Moreover, the thermodynamically stable
crystalline polymorph calcite (compared to vaterite) exhibited excellent recyclability. The isothermal study
reflects the comparatively high value of correlation coefficient (R2 ¼ 0.94) for the Langmuir isotherm
compared to those of the Freundlich isotherm(R2 ¼ 0.82) showed that the adsorption of diesel oil onto the
hydrophobic CaCO3 adsorbent was much better described by the Langmuir isotherm. The kinetics study of
second-order rate expression (R2 ¼ 0.99) more fitted with the experimental data compare to first-order
model (R2 ¼ 0.92). The synthesized calcite exhibited a significant dual oleophilic and hydrophobic nature
that can be applicable for oil adsorption/or removal purpose in oil contaminated areas in environment
and/or industrial oily wastewater for green, simple, and inexpensive environmental cleanup.

2nd place winner of the USQ Publication Excellence Awards for Journal Articles published during the period July - September 2017.
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