Table 2. IFT of the Heavy Crude Oil/Water Interface with Different Demulsifier Concentrations in the Aqueous Phase at 25 °C.

demulsifier	concentration (mg L–1)	IFT (mN/m)
DNPA-6	0	33.5 ± 1
	250	23.5 ± 0.8
	500	19 ± 0.5
	1000	11 ± 0.1
DNPA-5	0	33.5 ± 1
	250	23.3 ± 0.8
	500	20.2 ± 0.5
	1000	11.7 0.1
DNPA-4	0	33.5 ± 1
	250	26 ± 0.5
	500	21.5 ± 0.5
	1000	15 ± 0.4