Degradation of Surfactants by an Integrated Nanobubbles/VUV Irradiation Technique

Abstract

Recently, many efforts have been devoted to the elimination of alkylbenzene sulfonate (ABS) surfactants from aqueous systems. In this paper, a water and wastewater treatment technique that uses an 8-W low-pressure mercury lamp in the presence of nanobubbles (diameter = 720 nm) was demonstrated for the decomposition of sodium dodecylbenzenesulfonate (SDBS), as a model compound in aqueous solution. Degradation experiments were conducted with an ozone lamp (185−254 nm), both with and without nanobubbles. The result shows that the oxidation and mineralization rate of SDBS were significantly enhanced under 185−254 nm irradiation by oxygen nanobubbles. Although a high concentration of surfactant was used in this study, SDBS removal is effective in the integrated nanobubbles/vacuum ultraviolet (VUV) system, via the observation of 99.8% SDBS oxidation and 76.8% total organic compound (TOC) removal after 24 h of irradiation. The current study investigates the effect of size of bubble on the mineralization rate of SDBS. Furthermore, the rates of surfactant degradation were compared with those of nonsurfactant such as benzene sulfonate (BS). It was found that the mineralization of SDBS surfactants with nanobubbles was observed to be more effective than that with microbubbles (diameter = 75.8 μm). The comparative results show that the mineralization rate of surfactants was much faster than nonsurfactant in the presence of nanobubles under 185−254 nm irradiation. Based on the experimental results and kinetic degradation model, we concluded that the enhancement on the mineralization of surfactants is attributed to the high adsorption capability of nanobubbles, because of the small particle size offering a large surface area to facilitate the reaction.