Simultaneous removal of phenol and Cu(II) from wastewater by tallow dihydroxyethyl betaine modified bentonite

An organobentonite modified with an amphoteric surfactant, tallow dihydroxyethyl betaine (TDHEB), was used as an adsorbent to simultaneously remove Cu(II) and phenol from wastewater. The characteristic of the organobentonite (named TDHEB-bentonite) was analyzed by X-ray diffraction, Fourier-transform infrared spectra and nitrogen adsorption-desorption isotherm. Batch tests were conducted to evaluate the adsorption capacities of TDHEB-bentonite for the two contaminants. Experiment results demonstrated that the adsorption of both contaminants is highly pH-dependent under acidic conditions. TDHEB-bentonite had about 2.0 and 5.0 times higher adsorption capacity toward Cu(II) and phenol, respectively, relative to the corresponding raw Na-bentonite. Adsorption isotherm data showed that the adsorption processes of both contaminants were well described by Freundlich model. Kinetic experiment demonstrated that both contaminants adsorption processes correlated well with pseudo-second-order model. Cu(II) had a negative impact on phenol adsorption, but not vice versa. Cu(II) was removed mainly through chelating with the organic groups (-CH2CH2OH and -COO-) of TDHEB. Otherwise, partition into the organic phase derived from the adsorbed surfactant was the primarily mechanism for phenol removal. Overall, TDHEB-bentonite was a promising adsorbent for removing Cu(II) and phenol simultaneously from wastewater.