Sulfolane facilitates diisopropylamine dissolution in water, potentially enhancing pollutant transport

• Sulfolane and diisopropylamine are found as co-pollutants in groundwater. • Sulfolane promotes diisopropylamine miscibility in water. • Sulfolane hampers diisopropylamine sorption onto minerals. • Sulfolane can promote diisopropylamine migration across aquifers. Diisopropylamine (DIPA) and sulfolane are emerging groundwater co-contaminants, used in different industrial processes including carbon capture. In binary aqueous mixtures, sulfolane is freely miscible in water, with limited sorption onto minerals. Instead, DIPA yields sub-micron dispersions in water and sorbs onto different minerals. This limits DIPA migration in groundwater. Ternary aqueous mixtures of DIPA and sulfolane have not been studied before. Here we show that sulfolane enhances DIPA miscibility in water, although sulfolane and DIPA are immiscible without water. This unexpected co-solvency effect inhibits DIPA sorption onto minerals. Small angle neutron scattering experiments reveal composite droplets with a small DIPA core (diameter ≈ 12 Å) surrounded by sulfolane, which disperses DIPA. Fourier transform infrared spectroscopy and computer simulations show interactions between DIPA and sulfolane in water, which in aid in solubilizing DIPA in water. These findings will aid in predicting and preventing co-pollutant migration in groundwater.