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

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 PACl(2) (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, Al-27 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 PACl(2) to break CBLA and modify the density of two DNPALs, trichloroethylene (from 1.464 g/cm(3) to 0.980 g/cm(3)), and nitrobenzene (from 1.197 g/cm(3) to 0.921 g/cm(3)). 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.

Automated summary

This study successfully prepared a novel demulsifier PACl(2) which can effectively enhance the density modification of DNPALs, especially in acidic environments. The research also revealed the mechanism by which a small amount of aquifer material can promote demulsification.