Preparation and application of polyaluminum chloride for demulsification of colloidal biliquid aphron and density modification for DNAPLs

Abstract

The preparation and application of suitable demulsifiers in the process of density control of DNPALs is in urgent demand. In this study, we prepared a demulsifier -polyaluminum chloride (PACl), for density modifier -colloidal biliquid aphron (CBLA). We found that PACl2 (PACl with [OH]/[Al] = 2) can make CBLA to completely release light organic liquids within 30 min. The prepared PACl was characterized by SEM, XRD, the reaction curve of PACl with ferron reagent, 27Al NMR and charge density test in order to identify the reactive groups and elucidate the demulsification mechanisms. The system achieved 95% demlusification efficiency in acidic environment (pH < 4). The demulsification process followed pseudo-second-order kinetics model. A small amount of aquifer material could promote demulsification due to natural demulsifiers. We also used PACl2 to break CBLA and modify the density of two DNPALs, trichloroethylene (from 1.464 g/cm3 to 0.980 g/cm3), and nitrobenzene (from 1.197 g/cm3 to 0.921 g/cm3). The results show that the density of DNAPL can be reduced to less than that of water, which effectively prevents the downward migration of DNAPLs during remediation process. The findings will improve our understanding of the mechanism of CBLA demulsification and its density modification of DNAPLs for enhanced groundwater remediation.