Journal of Surface Science and Technology

P. Somasundaran ¹, Joy T. Kunjappu ¹

Affiliations
1 Langmuir Center for Colloids and Interfaces, School of Engineering and Applied Science, Columbia University, New York, N.Y. 10027, US

Abstract

While a macroscopic understanding of most colloid and surface phenomena can be obtained from bulk property measurements, a deeper understanding of such imponant processes as adsorption, flotation and flocculation is possible only by the application of specialized spectroscopic and related techniques yielding molecular-level information. In chis paper, our recent efforts to explore the microscopic structures of surfactant and polymer layers on solids are outlined. In an attempt to delineate the microstructure of the polymer and surfactant adsorbates, computer-assisted tomographic (CAT) scan as well as small-angle neutron scattering (SANS) method are used in addition to luminescence, magnetic resonance and time-resolved resonance Raman spectroscopic studies. New information on the floc as well as adsorbed layer characteristics are presented. A simple method for studying short-term (< 1 min) adsorption kinetics of polymers on solids is also described.

Keywords

Interface, Solloids, Hemimicelles, Microviscosity, Luminescence.

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P. Patra ¹, D. Gunaseelan ², R. Sen ², P. Somasundaran ¹

Affiliations
1 Department of Earth and Environmental Engineering, Columbia University, NY, 10027, US
2 Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal, 721302, IN

Abstract

Surfactants are commonly used in many personal care, pharmaceutical and food products that humans and others come in contact with in our daily life. The impact of the surfactants on human health is of growing concern and has been recognized by industries, governments and the general public. Thus, there is recognition for the need for benign or “greener” surfactants. Surfactants are typically considered greener if they are acquired from natural sources and undergo greener processing routes. In this regard, greener surfactants are biosurfactants derived from microbes and plant. Bacteria produce a variety of surfactants, such as Emulsan, which is produced by gram-negative bacterium Acinetobacter calcoaceticus strain RAG-1, extracellular sophorolipids produced by Candida bombicola species, rhamnolipids produced by Pseudomonas aeruginosa in L-Rhamnosyl-L-Rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate and L- rhamnosyl-β-hydroxydecanoyl-β-hydroxyd ecanoate forms, and lipopeptide produced by Bacillus subtilis. Furthermore, using today’s advanced synthesis biological tools, bacteria can be genetically modified to produce surfactants with molecular structures for desired performance. For example, Bacillus subtilis strains can be developed which are capable of producing different types of fatty acid and glutamate based surfactants. These bio-surfactants exhibit surface active properties similar to conventional surfactants. It is to be noted that biosurfactant molecules are complex in terms of the surfactant functional groups and varying carbon chain lengths and understanding of the structure-property-performance relationships of these complex molecules is therefore key to their optimum usability.

Keywords

Alkyl Chain Length, Biosurfactants, Emulsan, Fatty Acid Glutamate, Green Chemistry, Rhamnolipids

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