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Effect of surfactant loading and type upon the sorption capacity of organobentonite towards pyrogallol A Physicochemical and engineering aspects

Martinez-Costa, J.I., Leyva-Ramos, R.
Colloids and surfaces 2017 v.520 pp. 676-685
bentonite, cationic surfactants, cetyltrimethylammonium bromide, desorption, dissociation, hydrophobicity, pH, pyrogallol
In this work, the bentonite surface nature was modified by adsorbing the cationic surfactants HexaDecylTriMethylAmmonium bromide (HDTMA), DoDecylTriMethylAmmonium bromide (DDTMA) and BenzylTriMethylAmmonium bromide (BTMA), and the organobentonites were designated as OBHDTMA, OBDDTMA and OBBTMA. The bentonite capacity for sorbing pyrogallol was negligible; however, it was considerably enhanced by the modification with the surfactant since the sorption capacity of OBHDTMA was 45 times higher than that of bentonite. The sorption capacity of organobentonites towards pyrogallol decreased as follows: OBHDTMA>OBDDTMA>OBBTMA. The capacity of OBHDTMA varied somewhat in the pH range of 3–7 but reduced considerably when the pH was raised from 7 to 9. The small capacity observed at pH=9 was due to the pyrogallol dissociation, which reduced the pyrogallol affinity for the organic phase of OBHDTMA. The pyrogallol was sorbed on OBHDTMA at pH=7 and then desorbed at pH 7 or 9. The desorption was irreversible and reversible when the desorbing solution pH was 7 and 9, respectively. The capacity of OBHDTMA was linearly increased by raising HDTMA loading; therefore, the pyrogallol sorption on OBHDTMA was due to a partition mechanism attributed to hydrophobic and organophilic interactions at pH≤7.