Enhanced Adsorption of 2,4-Dichlorophenol by Nanoscale Zero-Valent Iron Loaded on Bentonite and Modified with a Cationic Surfactant

Bentonite-supported nanoscale zero-valent iron (Bent-nZVI) was modified by cetyltrimethylammonium bromide (CTMAB), a cationic surfactant, to form a composite material (Bent-nZVI/CTMAB) for adsorption and reduction of 2,4-dichlorophenol (2,4-DCP). The results show that the removal rate of 2,4-DCP increased from 7.6% by Bent-nZVI to 66.6% by Bent-nZVI/CTMAB, and this improvement increased with increasing concentration of the modifier. The surfactant modification altered the zeta potential of bentonite from negative to positive and increased the specific surface area of Bent-nZVI from 1.18 to 2.01 m 2 g –1, which was beneficial to the adsorption of neutral or anionic 2,4-DCP onto Bent-nZVI/CTMAB. SEM images, FTIR spectra, and HPLC chromatograms showed that 2,4-DCP existed in Bent-nZVI/CTMAB in the form of needle-like crystals and was not reduced by the nZVI particles after the removal. Yet, the possible reduction intermediates, 2-chlorophenol, 4-chlorophenol, and phenol, were not detected in the solution or solid phase after the removal of 2,4-DCP. Hence, the enhanced removal of 2,4-DCP was mainly attributed to adsorption rather than reduction.