Susanta Malik

A review on natural surfactants

Natural surfactants or biosurfactants are amphiphilic biological compounds, usually extracellular, produced by a variety of microorganisms from various substances including waste materials. There is increasing interest on this topic because of their unique properties such as low toxicity, functionality under extreme conditions, based on renewable substances and biologically degradable nature. The diversity of these molecules supports their potential application in the field of petroleum, medicine, agriculture, food, cosmetics etc. They are also effective in curtailing the green-house effect by reducing the emission of CO2. They can be termed as ‘green’ because of their low toxicity, biodegradability and relative stability under a wide range of physicochemical environments. In spite of possessing diverse structures and better physicochemical properties than chemical surfactants, biosurfactants are not able to compete with their synthetic counterparts because of their high production & downstream costs. The commercial realization of these eco-friendly biomolecules is restricted by low productivity, expensive downstream processing and lack of appropriate understanding of the bioreactor systems for their production. But we expect that in future better reactor design and product recovery technology would be developed and overproducer microbial strain would be screened. Then production cost would be decreased and yield would be increased i.e. the production would be both ecologically & economically favored. The present review deals with an overall view on biosurfactants, their properties, advantages & disadvantages, production, characterization, application along with a recommendation for future research.

Modernization of surfactant chemistry in the age of gemini and bio-surfactants: a review

Modern surfactant science demands chemistry which is benign by design. Efficient green chemicals like gemini surfactants along with natural resource derived bio-surfactants are thus most dependable in this case. In the search for less pollution and more ecologically beneficial solvents, more and more environmentally accepted trends are emerging every day into the market; species related to properties such as lower toxicity, higher biodegradability, chemical stability, environmental safety, efficient solubilization and of course, ease of recycling, can be vital tools. Bio-surfactants along with geminis are of great interest for their very efficient working ability, lower CMC and other up to date features that modern science desires for the betterment of mother nature. This review contains elaborate discussions on the efficiencies of gemini and bio-surfactants as modern generation green chemicals in various fields viz. in laboratory based kinetic experiments, electron transfer reactions, emulsification, solubilization, and agro-industrial and bio-medicinal fields which provides us with the hope of an amazing future prospect with these types of green chemicals.

Combination of Best Promoter and Micellar Catalyst for Cr(VI) Oxidation of Lactose to Lactobionic Acid in Aqueous Medium at Room Temperature

Abstract In aqueous acidic media, picolinic acid, 2,3-dipicolinic acid, and 2,6-dipicolinic acid promoted Cr(VI) oxidation of lactose to lactobionic acid has been carried out at room temperature. A possible reaction mechanism, which is based on the kinetic results and the product analysis, has been proposed. The anionic surfactant sodium dodecyl sulphate (SDS) and nonionic surfactant Triton-X-100 (TX-100) accelerate the process while the cationic surfactant N-cetylpyridinium chloride (CPC) retards the reaction.

Best combination of promoter and micellar catalyst for the rapid conversion of sorbitol to glucose

Kinetic data for oxidation of D-sorbitol to glucose by hexavalent chromium in aqueous medium and aqueous surfactant medium (SDS, TX-100) have been reported. Effect of promoter such as PA, bipy and phenanthroline on the reaction has been investigated. The reaction is performed under pseudo first order condition with an excess of substrate over the oxidant. The reaction is first order with respect to substrate and oxidant. The micelles have a catalytic effect on the reaction. Combination of phen and TX-100 produces almost twelve times increase in rate of oxidation.

Combined effect of promoter and surfactant on the chromium(VI) oxidation of D-ribose in aqueous media at room temperature

ABSTRACT Effect of polypyridine derivatives on chromium(VI) oxidation of D-ribose in aqueous media was studied spectrophotometrically. The oxidized product D-erythrose was detected by paper chromatography. The promoters 1,10-phenanthroline, 2,2΄-bipyridine, 2-picolinic acid, and 2,3-dipicolinic acid accelerated the oxidation, whereas isomeric 4,7-phenanthroline, 4,4΄-bipyridine, 4-picolinic acid, and 2,6-dipicolinic acid did not influence the oxidation. Formation of Cr(VI)-promoter complex was identified through fluorescence spectroscopy. Rate constants depended on promoter concentration. SDS and TX-100 enhanced the D-ribose oxidation, while CPC retarded the reaction. Location of D-ribose inside micelles was observed through 1H NMR. DLS study showed that the relative size of SDS and TX-100 micelles expanded in presence of chromium(VI). GRAPHICAL ABSTRACT

Review on chemically bonded geminis with cationic heads: second-generation interfactants

Cationic gemini surfactants are a special class of second-generation smart surfactants. Since Menger first named them, gemini surfactants have drawn a wide and immense attraction from scientists throughout the whole world. These dimeric surfactants possess two or more hydrophilic with two or more hydrophobic head groups, chemically bonded with a linker, called the spacer group. These kinds of surfactants are used mainly in homogeneous catalytic reactions, as well as for solubilisation, emulsification, and many more technical applications. They are used in industries for electro-decoating, stabilization of adhesive polymer latex, anti-friction agents, mining, paper manufacturing, preparation of surfactants including softeners, cosmetics, and most importantly, recent advancement in drug designing, synthesis, and application in medicine. The aim of this paper is to bring attention to the high performance second generation interfactants, with a focus on their synthesis, structure, types, and greener industrial application with high possibility of future prospect.

Employment of different spectroscopic tools for the investigation of chromium(VI) oxidation of acetaldehyde in aqueous micellar medium

Different spectroscopic methods have been applied to investigate the chromic acid oxidation of acetaldehyde in aqueous media, catalysed by surfactants. Three representative heteroaromatic nitrogen base promoters, 2-picolinic acid (PA), 2,2’-bipyridine (bpy) and 1,10-phenanthroline (phen), have been associated along with surfactants as promoters to the kinetic study. Comparative studies of unpromoted and promoted reactions invoked that 2,2’-bipyridine produced maximum rate enhancement. The mechanism of the reaction path has been proposed with the help of kinetic results and spectroscopic studies. The observed net enhancement of rate effects has been explained with scientific manipulations and data obtained. The combination of TX-100 and1,10-phenanthroline is found to be most effective for acetaldehyde oxidation.Graphical AbstractChromium(VI) oxidation of acetaldehyde in aqueous micellar media has been carried out. Micellar catalysis by TX-100 in association with a ‘phen’ promoter increases the rate of the reaction almost 60 fold. The combination of TX-100 and ‘phen’ is the most suitable one for chromic acid oxidation of acetaldehyde to acetic acid in aqueous media.

Optimal Process Condition for Room Temperature Hetero-Aromatic Nitrogen Base Promoted Chromic Acid Oxidation of p-Chlorobenzaldehyde to p-Chlorobenzoic Acid in Aqueous Micellar Medium at Atmospheric Pressure

Abstract The present paper describes the kinetics of oxidation of p-chlorobenzaldehyde by chromic acid in aqueous and surfactant media in the presence of a promoter at 303 K. The rate constants were found to increase with introduction of hetero-aromatic nitrogen base promoters such as picolinic acid (PA), 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen). The product p-chlorobenzoic acid has been characterized by NMR. The mechanism of both unpromoted and promoted reaction paths has been proposed. In presence of the anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant N-cetylpyridinium chloride (CPC) and non-ionic surfactant Triton X-100 (TX-100) the reaction can undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation. Both SDS and TX-100 produce a normal micellar effect whereas CPC produces a reverse micellar effect in the presence of p-chlorobenzaldehyde.

Characterization of Pyrene Solubilization in Selective Micellar Media of Novel Bio-degradable Natural Surfactant Saponin (Extracted from Soap Nut) and Conventional Surfactant SDBS in Presence and Absence of Common Salt NaCl

Abstract Solubilisation of pyrene (PAHs) in aqueous micellar solutions of natural surfactant saponin and conventional surfactant sodium dodecylbenzene sulfonate (SDBS) has been examined by UV-Vis and steady state fluorescence spectrometry at 30°C. The effect of addition of common salt NaCl on the I1/I3 of fluorescence has also been determined. The experiment concludes that the pyrene molecules were incorporated in the palisade layers of both micelles because of their hydrophobic character. The interaction of pyrene with a neutral saponin micelle resulted in a red shift of UV absorption spectra, while the negative headed surfactant SDBS showed no such phenomena. The resulting thermodynamic parameters proved the better efficiency of the bio-surfactant saponin for the solubilization of pyrene with respect to that of the conventional surfactant SDBS. With increasing ionic strength (on addition of NaCl) the solubilization of pyrene was found to be better and effective in both the surfactant mediums.

Extraction of Natural Surfactant Saponin from Soapnut (Sapindus mukorossi) and its Utilization in the Remediation of Hexavalent Chromium from Contaminated Water

Abstract In this study optimization of extraction conditions for saponin from soapnut (Sapindus mukorossi) has been investigated. This investigation showed that a better extraction of saponin can be achieved with increasing the dielectric constant of solvent employed. The best yield was attained in a 50% v/v aqueous ethanol medium. Another objective of the present study is to assess the thermodynamics of the uptake-reduction of hexavalent chromium in contaminated water samples using saponin. Pyrene has been employed to determine the critical micellar concentration (CMC) (in the UV-vis method of determination) of saponin as a spectroscopic probe. Thus, the effectiveness of the bio-surfactant as a self-motivated adsorbent for hexavalent chromium is investigated. Several physico-chemical parameters like contact time, sorbate concentration, pH and temperature have been determined. The findings of the investigation invoked a very efficient uptake of 213.48 mg g−1 of hexavalent chromium from the contaminated water sample at a lower value of pH 2 and temperature 35°C. It is observed that the method followed a pseudo-first order kinetics, where the evaluated ΔG0 has supported the sorption as a feasible and spontaneous process. The HR-MS, FTIR, steady state Fluorescence spectroscopy, HR-TEM and UV-Vis spectroscopy have been employed for the current scientific studies.