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From waste came forth surfactants: Humic acid like substances isolated from 0-60 day-old compost display excellent surface activity and solvent properties. These biosurfactants were used to solubilize a dye in water below and above their critical micellar concentration. The biosurfactant unimers appear to have higher dye-solubilizing power than the corresponding micelles.Humic acid like substances isolated from compost show potential as chemical auxiliaries. In the present study, three surfactant samples were obtained from green waste composted for 0-60 days to assess aging effects of the source on the properties of the products. The surface activity, dye solubility enhancement, and chemical nature of these substances were compared. No differences in performance were established among the samples. They lower water surface tension and enhance the dye solubility upon increasing their concentration. However, the ratio of soluble dye to added surfactant is higher in the premicellar than in the postmicellar concentration region. Structural investigations indicated the humic acid like substances to be amphiphiles with molecular weights in the range of 1-3 x 10(5) g mol(-1). The surfactant samples were also compared to sodium dodecylbenzenesulfonate, polyacrylic acid, and soil and water humic substances. The results encourage the application of compost as a source of low-cost biosurfactant.

A sol–gel‐derived microporous ceramic membrane with an exceptionally low permeability for CO2 from gaseous streams was developed and characterized. The sols were prepared from a mixture of niobium and silicon alkoxide precursors by acid‐catalyzed synthesis. Microporous films were formed by coating asymmetric γ‐alumina disks with the polymeric sol (Si/Nb=3:1), followed by calcination at 500 °C. The membrane consists of a 150‐nm‐thick layer with a Si/Nb atomic ratio of about 1.5. The single‐gas permeance of small gas molecules such as H2, CH4, N2, and SF6 decreases steadily with kinetic diameter. Hydrogen, helium, and carbon dioxide follow an activated transport mechanism through the membrane. The permeance of CO2 in this membrane is much lower than that in pure silica, and its behavior deviates strongly from the general trend observed with the other gases. This is attributed to a relatively strong interaction between CO2 and adsorption sites in the niobia–silica membrane.

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Acid soluble biopolymeric substances (SBP) were isolated from different urban biowastes comprised of a range of materials available from metropolitan areas. These biowastes provided products with a chemical nature and solubility properties changing over a wide range and, thus, allowed to assess the effect of the variability of the chemical nature on molecular conformation and surface activity in water solution. For this scope, the SBP were characterized for chemical composition and molecular weight (MW) by microanalysis, potentiometric titration, (13)C NMR spectroscopy, and size exclusion chromatography (SEC) coupled with an online multiangle light scattering (MALS) detector. These materials were found to have 67-463 kg mol(-1) MW and 6-53 polydispersity index and to contain carboxylic acid and phenol groups bonded to aromatic and aliphatic C chains. An empirical parameter (LH) was calculated for use as an index of the lipophilic/hydrophilic C atoms ratio. The products solubility properties in solvents of different polarity, surface activity, power to enhance the water solubility of hydrophobic compounds, and particle size in water solution were also investigated by measurements of the products partition coefficient between polyethylene glycol and water (KPEGW) and of air-water surface tension (γ), water-hexane interfacial tension (IFT), disperse red orange dye solubility (DS), and dynamic light scattering (DLS) versus added SBP concentration (Cs). The results indicate that LH correlates well with KPEGW and with the products surface activity properties. Both γ and DS are shown to depend on Cs, although in opposite ways, that is, higher Cs values yield lower γ and higher DS values. Both DS-Cs and γ-Cs plots showed a significant slope change at approximately the same 1.8-2.5 g L(-1) Cs value. This suggested a change of molecular conformation taking place at the above Cs values. Hydrodynamic diameter values for SBP in solution at Cs ≤ 10 g L(-1) were found to range from 130 to 300 nm, consistent with their macromolecular nature. The DLS coupled to the γ data were consistent with molecules at the water-air interphase and in the bulk water phase having different conformations, but not significantly different molecular sizes. Molecular aggregates more likely form at 50-100 g L(-1) Cs. The results confirm that urban biowastes are a sustainable source of biobased products that may have real commercial perspectives.

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