Freundlich adsorption isotherm coefficients for sodium dodecyl sulphate (SDS) and sodium lauroyl isethionate (SLI) monolayer and bilayer adsorption profiles determined from linear fittings in Fig. 3A(i) and (ii). Here, K_d and 1/n are the Freundlich coefficients related to the adsorption affinity and intensity respectively, is the maximum monolayer collector adsorption density (i.e. monolayer to bilayer transition point), and are the collector supernatant equilibrium and initial dosed concentration respectively at the monolayer to bilayer transition point.

Isotherm value	Sodium dodecyl sulphate (SDS)		Sodium lauroyl isethionate (SLI)
	Monolayer	Bilayer	Monolayer	Bilayer
Freundlich R2	0.89	0.99	0.87	0.96
K d (mg g−1)	3.21 × 10−2	1.60 × 10−3	4.43 × 10−2	1.21 × 10−4
K d (μmol m−2)	1.39 × 10−2	6.94 × 10−4	1.61 × 10−2	4.39 × 10−5
1/n	0.43	1.41	0.2	2.44
n	2.30	0.71	5.10	0.41
(μmol m−2)	∼0.11		∼0.05
(mg g−1)	∼0.24		∼0.14
(μM)	∼111		∼95
(mg g−1)	∼0.03		∼0.03
(μM)	∼172		∼188
(mg g−1)	∼0.05		∼0.03
Linear R2	0.98		0.99