Bio-based surfactant-like molecules from organic wastes : the effect of waste composition and composting process on surfactant properties and on the ability to solubilize tetrachloroethene (PCE)

In this work, four surfactant-like humic acids (HAS) obtained from garden lignocellulose wastes and kitchen food wastes mixed with garden-lignocellulose wastes, both before and after composting, were tested for surfactant properties and the ability to solubilize tetra chloroethene (PCE). The waste-derived HAS showed good surfactant properties, lowering the water surface tension from 74 mN m(-1) to 45.4 +/- 4.4 mN m(-1), with a critical micelle concentration (CIVIC) of 1.54 +/- 1.68 g L-1, which is lower than many synthetic ionic surfactants. CMC was affected by both waste origin and composting processes. The addition of food waste and composting reduced CIVIC by adding alkyl-C (measured by CP MAS C-13 NMR) and N- and S-HA contents (amide molecules), so that a multistep regression was found [CIVIC = 24.6 - 0.189 alkyl C - 2.64 (N + S); R-2 = 0,77, P < 0.10, n = 61. The four HAS solubilized PCE at the rate of 0.18-0.47 g PCE/g aqueous biosurfactant. These results were much higher than those reported in the literature for a commercial HA (0.026 g/g), but they were in line with those measured in this work for nonionic surfactants such as Tween-80 (0.69 g/g) and Triton X-100 (1.08 g/g).