Effective treatment of high-concentration SDBS solution by developing a novel integrated technology of foam separation and photocatalysis

Abstract

With the rapid increasing drainage of industrial sewage, the problems arising from sewage containing high-concentration surfactant become more urgent. In order to purify the high-concentration surfactant solution, a novel integrated technology of foam separation and TiO2 photocatalysis was developed. An anionic surfactant of sodium dodecyl benzene sulfonate (SDBS) was used as the model surfactant and its initial concentration in the simulated solution was 0.5 g/L. First, foam separation had been performed to primitively reduce SDBS concentration in the simulated solution. Based on the results of independent factor test, a five-level-three-factor central composite design (CCD) based on response surface design (RSM) was used to predict the optimal experimental conditions. Under above conditions, the enriching proportion and removing percentage of SDBS were 4.69 ± 0.14 and 84.85 ± 0.71 %, respectively. The surface tension and foam stability of the residual solution after foam separation had been measured using pulling ring method and bubbling method, respectively. The residual solution after foam separation possessed a higher surface tension and weaker foam stability compared with those of freshly prepared SDBS solution. Extrinsic fluorescence spectra using pyrene showed that interfacial adsorption had led to the generation of hydrophilic SDBS micelles. In order to perform TiO2 photocatalysis, the adsorption capacity of SDBS on TiO2 nanoparticles had been studied. The adsorption of SDBS on TiO2 nanoparticles obeyed Pseudo-second-order dynamics model and Freundlich isotherm model. Based on the unique optical property and particle entrainment capacity of foam, a coupling operation of foam separation and TiO2 photocatalysis was proposed to degrade SDBS in the residual solution. The suitable operating conditions were identified and the maximum degradation percentage of SDBS reached 94.86 ± 1.06 %. The total SDBS removing percentage of developed technology was 99.38 ± 0.10 %. Total organic carbon (TOC) concentrations of SDBS solution before and after treatment were measured using combustion oxidation coupled nondispersive infrared absorption method. Finally, the economic analysis was carried out to assess the cost effectiveness of the integrated technology of foam separation and TiO2 photocatalysis.