Removal Of Benzoic Acid By Adsorptive Micellar Flocculation Of Anionic Surfactant And Aluminum Salt

Surfactant has been widely used in industry,agriculture and daily life,because it could significantly alter the interface state and nature of the system.It could wrap some insoluble organics through forming micelles and carry insoluble organics to the environment,affecting water quality and public health.Due to the complexity of surfactant wastewater,flocculation and other physical and chemical methods have been usually used as the pretreatment techniques,but flocculation process was affected by various factors.Adsorption micellar flocculation?AMF?based on the flocculation of anionic surfactant and aluminum salt has been considered as a simple and low-cost pretreatment method,which has broad prospects for development and is currently in research stage.On the basis of surfactant micellar theory and existed water treatment flocculation studies,sodium dodecyl sulfate?SDS?and sodium dodecyl benzene sulfonate?SDBS?were chosen as the typical anionic surfactants,meanwhile aluminum sulfate?Al₂?SO₄?₃?was used as the flocculant and benzoic acid?BA?was selected as the coexisting organic pollutant in aionic surfactant wastewater to investigate the influence of C_Al/C_S?the initial concentration ratio of Al ions and anionic surfactants?,pH and CBA?the concentration of BA?on anionic surfactants and BA removal.The interaction mechanism between anionic surfactants,Al₂?SO₄?₃ and BA was explored from the perspective of solution chemistry,and the corresponding conclusions were verified from structural aspects through scanning electron microscopy?SEM?and fourier transform infrared spectroscopy?FTIR?analysis on the precipitated flocs.The results suggestted that:?1?The solubility of BA,an acidulous organic matter,would increase significantly due to micellar solubilization.BA could be removed effectively by adsorption micellar flocculation between anionic surfactants and Al₂?SO₄?₃.BA could solubilize into the anionic surfactant micelles and form Al-BA complexes that would be adsorbed by micelles.Then BA monomers and Al-BA complexes were adsorbed or trapped by flocs.?2?The complexation of Al ions and BA played an important role in BA removal.The increase of Al ions concentration(that is,C_Al/C_S)was beneficial for BA removal,but the strong ionic strength at high C_Al/C_S would weaken the chemical activity of Al ions to bind with micelles.So removal efficiency of BA would decrease and the removal of anionic surfactants would not be significantly enhanced by increasing C_Al/C_S.When C_Al/C_SDS and C_Al/C_SDBS were 2.00 and 3.00,SDS,SDBS and BA removal was more efficient.?3?pH affected the hydrolysis of Al ion and the dissociation of BA,and the decrease of H+ concentration would promote the formation of various hydroxy aluminums and BA dissociation.Low pH was unfavorable to remove BA while the high pH was adverse to BA and anionic surfactants removal.[Al2?OH?2?H2O?8]4+,[Al3?OH?4?H2O?10]5+ and other strong flocculants might be formed at pH 4.0 5.0 by condensation polymerization between hydroxy aluminums.And complexation between Al ions and BA was enhanced within this pH range.Therefore,the optimal p H for anionic surfactants and BA removal was 4.00 5.00.?4?Compared with the SDBS-Al₂?SO₄?₃ flocculation system,SDS-Al₂?SO₄?₃ flocculation system was easier to destabilize and could be effective in wider pH range at the optimal C_Al/C_S.At the optimal C_Al/C_S and pH,removal efficiencies of anionic surfactants and BA were higher in SDS-Al₂?SO₄?₃ flocculation system,which might be affected by the size,shape and aggregation number of anionic surfactant micelles,the solubilization ability of micelles and the initial concentration of Al salt.