Highly Water‐Dilutable and <scp>pH</scp> ‐Responsive Microemulsions: Fabrication and Potential Applications in Remediation of Benzo[g,h,i]Perylene‐Contaminated Soil

ABSTRACT Microemulsions (MEs), which possess the properties of both high water‐dilutability (HWD) and on‐demand demulsification, might be more advantageous for their applications in actual technical fields. Hence, triethylamine laurate was utilized as the surfactant to construct HWD pH‐responsive MEs (C 12 TEA‐MEs) by means of the phase diagram. The structural features of C 12 TEA‐MEs were respectively characterized through conductivity, dynamic light scattering, and cryogenic transmission electron microscopy. Upon acidification with HCl, the monophasic MEs are rapidly and efficiently demulsified into oil–water phase separation regardless of the type of MEs. The C 12 TEA‐MEs can be diluted to a possible water mass fraction as high as 99.2%. The C 12 TEA‐MEs possess an excellent solubilization capacity for benzo[g,h,i]perylene (BghiP) from topsoils. The removal rate of BghiP can be up to 99.8%, even when the mass fraction of surfactant in C 12 TEA‐ME is diluted to 0.3%. More than 99.8% of the total BghiP in eluent enters the oil phase after demulsification, and the minimum mass ratio of the BghiP‐containing oil phase to the eluent can reach ∼1.0%. Meanwhile, the chemical oxygen demand of the water phase can be remarkably reduced to ~9.7 mgO 2 L −1 after a simple and conventional treatment, resulting in the treated water phase containing minimal organic species.