C. Thakulsukanant et al., ADSOLUBILIZATION AND STABILITY CHARACTERISTICS OF HYDROCARBON AGGREGATES CHEMICALLY BONDED TO POROUS SILICA, Langmuir, 13(17), 1997, pp. 4595-4599
The desorption of surfactant may be a problem in the development of ad
micellar catalysis for organic synthesis or for wastewater cleanup. Th
e formation of hydrocarbon aggregates chemically bonded to mineral oxi
de surfaces has been investigated to solve this problem. In this study
, octadecyltricklorosilane (ODS) was chemically bonded with silanol gr
oups of a silica surface. The adsolubilization capabilities and stabil
ity of the bonded ODS were then studied and compared to those of physi
cally adsorbed aggregates of cetyltrimethylammonium bromide (CTAB). Th
e adsorption of ODS increases with increasing ODS concentration in the
bulk phase and reaches a constant value when the equilibrium ODS conc
entration is higher than 17 000 mu M. The maximum ODS adsorption of 34
0 mu mol/g is slightly higher than that of CTAB (300 mu mol/g). The cr
itical micelle concentration of CTAB is approximately 3000 mu M. The a
dsolubilization of two organic substrates, trichloroethylene (TCE) and
phenol, was also measured. The adsolubilization of TCE was similar in
CTAB and bonded ODS, while the phenol adsolubilized to a greater exte
nt in CTAB than in ODS. The bonded ODS was stable under agitation up t
o 310 rpm and temperatures below 40 degrees C. The pH value has very l
ittle effect on ODS debonding. The rate of oxidation of ODS by ozone i
ncreases with increasing ozone concentration, but pH has no effect on
ODS oxidation.