Volume 59, Issue 1

Biosurfactants are amphiphilic microbial compounds synthesized from plants and micro organisms that have both hydrophilic and hydrophobic zones, which are classified into liquid-liquid, liquid-solid and liquid-gas interfaces. Due to their versatile nature, low toxicity, and high reactivity at extreme temperatures, as well as – extremely important – their good biodegradability and environmental compatibility, biobased surfactants provide approaches for use in many environmental industries. Biosurfactants produced by microorganisms have potential applications in bioremediation as well as in the petroleum, agricultural, food, cosmetics and pharmaceutical industries. In this review article, we include a detailed overview of the knowledge obtained over the years, such as factors influencing bio-surfactant production and developments in the incorporation of biomolecules in different industries and future research needs.

Surfactants are amphipathic molecules that are generally chemically derived. Compared to these surfactants, biosurfactants have a better environmental profile and are derived from microorganisms. Among the biosurfactants, sophorolipids (SLs) are probably the most promising biosurfactants. In general, the costs of raw materials in the synthesis of biosurfactants accounts for about 10–30% of the total costs. These costs can be reduced to some extent by using industrial by-products as substrates for the synthesis of SLs. In this study, sunflower acid oil (SAO), a by-product of sunflower oil refining, and crude glycerol (so-called “sweetwater”), which is the glycerol-rich solution from the mixed fat hydrolysis reaction, also an industrial by-product, are used for the synthesis of SLs. We obtained comparable yields (0.8/50 mL) to previous reports using a combination of treated SAO (10% w/v) and sweetwater (19% w/v). For the bleaching process, we used 1% and 3% activated earth for normal and heavy treatments over a period of 1 h and 3 h, respectively. Glycerol is inexpensively available in the form of sweetwater from fat-splitting plants and was used as the hydrophilic source. The purification of the SL can be achieved by crystallization at pH 7. The purified SL is analyzed by thin layer chromatography (TLC), Fourier transform infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC). Then, it was incorporated into different liposomal formulations for the encapsulation of the non-steroidal anti-inflammatory drug (NSAID) ibuprofen. The ratio of drug to cholesterol and SL was 1:1:0.5. The liposomal structures were examined for their size of 2 µ by direct light scattering.

Castor oil-based quaternary ammonium surfactant (COQA) was synthesized by an ester-exchange reaction of refined castor oil (CO) (raw material) with N,N -dimethyl ethanol amine followed by quaternization with epichlorohydrin (ECH). Its surface activity and structural features were determined. The critical micelle concentration (CMC) of the surfactant at 25 °C was 1.79 × 10 −3  mol/L. The surface tension of an aqueous COQA solution at CMC was 38.19 mN/m. Subsequently, the synthesized COQA was used to modify attapulgite (ATP) by binding it to the surface of ATP. The change in the morphology of the modified-ATP (M-ATP) was attributed to the presence of the COQA bound to the surface of the rod-shaped crystals, although the crystal structure of the silicate did not change. Compared to ATP, the microstructure of the M-ATP was less rigid.

Fischer-Tropsch syncrude prepared via the Fischer-Tropsch synthesis (FTS) using a Fe-based catalyst is featured by its high content of linear α-olefins (C 5 –C 13 ). The utilization of C 6 –C 8 α-olefins for the synthesis of alkyl benzene sulfonate surfactants was performed in the present work via dimerization, benzene alkylation, and sulfonation. The effects of the reaction conditions on benzene alkylation over a trimethyl amine hydrochloride-acidic anhydrous aluminum chloride ionic liquid catalyst (Et 3 NHCl-AlCl 3 ) have been studied in detail using C 6 α-olefin dimers as a model alkylation agent. Under the optimal reaction conditions (molar ratio of AlCl 3 to Et 3 NHCl = 2, catalyst loading = 0.29 mol %, reaction temperature = 30 °C, and molar ratio of benzene to C 6 α-olefin dimer = 10) the conversion of the C 6 α-olefin dimer was 100% and the selectivity toward the mono alkylbenzene product was 91.0%. C 6 –C 8 α-olefin dimer alkylbenzene sulfonates (C 6 –C 8 DBS) were synthesized via sulfonation using chlorosulfonic acid and characterized using Fourier Transform Infrared (FT-IR) spectroscopy and Liquid Chromatography–Mass Spectrometry (LC–MS). The surfactant properties of the C 6 –C 8 DBS, including their equilibrium and dynamic surface tension, foaming, wetting and emulsifying capabilities, were closely explored and compared with a commercial linear alkylbenzene sulfonate (LAS). The limiting surface tension ( γ CMC  = 34.62 mN m −1 ) and critical micelle concentration (CMC = 2.15 mmol L −1 ) of C 6 α-olefin dimer alkylbenzene sulfonate (C 6 -DBS) were similar to those of LAS. Upon increasing the hydrocarbon chain length, the γ CMC of C 6 -DBS, C 7 -DBS, and C 8 -DBS remained unchanged, while the CMC decreased. C 6 –C 8 -DBS exhibited foaming, emulsifying, and wetting properties comparable to LAS.

In this paper, a novel series of ester-functionalized cationic Gemini surfactants with amide groups (abbreviated as C m -(BAE)-C m ( m  = 12, 14, 16)) were synthesized and their surface tension as well as the thermodynamic surface parameters were determined with conductivity and fluorescence measurements, respectively. The structures of these Gemini surfactants were characterized by FT-IR, 1 H NMR, and MS. The Krafft points of the three surfactants are below 0 °C, indicating better water solubility. The critical micelle concentration (CMC) of these surfactants decreases with the increase in the length of hydrophobic chain. The micellization process of these surfactants was found to be entropy-driven. The polar functional ester groups in the spacer form hydrogen bonds with water molecules, which increases the solubility of these Gemini surfactants in aqueous systems, facilitates the aggregation of their monomers and improves the stability of their micelles.

The influence of chain length of n -alcohols such as 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol on cationic dodecyl trimethyl ammonium bromide (DTAB) micelles has been investigated. The effect of concentration was determined at alcohol concentrations of (10, 20, 30, 40 and 50) mM and at temperatures of 298.15 K, 303.15 K, 308.15 K and 313.15 K using ultrasonic velocity, density, viscosity and conductivity measurements. To study molecular interactions in micelles of various mixtures of DTAB and n -alcohols by using acoustical parameters, such as adiabatic compres-sibility ( β ad ), intermicellar free length ( L f ), acoustic impedance ( Z ), molar volume ( V M ) have been calculated by using ultrasonic velocity ( U ) and density ( ρ ). With the help of the trends observed when varying these parameters, the molecular interactions and thus the micellar growth of mixed systems of DTAB and n –alcohol were discussed. Viscosity data such as absolute viscosity, viscous relaxation time, oil solubilization, foam stability and conductance data complemented the observed ultrasonic data.

Microemulsions were formulated with the ionic liquid ethylammonium nitrate (EAN) used instead of water as the polar phase, hydrocarbon solvents ( n -alkanes) and sugar-based non-ionic surfactants, and their phase behaviour and microstructure were investigated. The sugar-based non-ionic surfactants used are non-toxic, biodegradable and environmentally friendly. Due to these properties, their use in microemulsion systems is a clear alternative to the conventionally used non-ionic surfactants from the class of alkyl polyoxyethylene ethers (C i E j ). The influence of n -alkanes with different chain lengths and of sugar-based nonionic surfactants with hydrophobic chains of different lengths on the microemulsion system was also investigated. The results obtained for the microemulsions with EAN described here are similar to those obtained for microemulsion systems formulated with water as the polar solvent. Liquid crystalline ( LC ) phases were observed in microemulsion systems with sugar-based nonionic surfactants having longer hydrocarbon chains, at lower temperatures and higher surfactant mass fraction.

Fifteen percent hydrochloric acid (HCl) solutions are used for some cleaning processes in the petroleum industry. The use of such a corrosive medium is mainly responsible for the corrosion of the stainless steel (SS-410) vessels and pipings. In this study, the corrosion inhibiting properties of Oryza sativa plant extract (OSPE) from agricultural residues are investigated on SS-410 steel surfaces in a 15% HCl medium. Gravimetric analysis showed a maximum corrosion inhibition of 91.92% with 4 g/L OSPE in 15% HCl solution. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction studies confirmed the adsorption of OSPE on the SS-410 surface. The adsorption of OSPE on SS-410 followed the Langmuir adsorption isotherm, indicating the formation of a monolayer on the SS-410 surface. The theoretical study confirmed that the anticorrosive effect could be mainly related to the phytochemical 9,12,15-octadecatrienoic acid 2,3-dihydroxypropyl ester. Consequently, the OSPE containing this phytochemical shows an anticorrosive behavior on the SS-410 surface in an acidic 15% HCl solution.

Drought is the major challenge of the present century in agricultural areas. Water scarcity has led to the use of contaminated water. The objective of the study was to determine the tolerance of wheat, Sirvan cultivar, to detergent contaminated water and drought at germination and early growth stages. The research included germination and pot experiments. In the germination experiment, laundry detergent concentrations of 0.05 g L −1 , 0.5 g L −1 , and 5 g L −1 were used to produce contaminated water and isoosmotic potential of polyethylene glycol (PEG) was used to produce water stress. In the pot experiment, the concentrations used in the germination experiment were applied with two irrigation intervals of 2 and 4 days. The results showed that at an osmotic potential of −0.217 MPa of laundry detergent and PEG, all germination traits were drastically reduced, but radicle length and length-based seed vigor were reduced at an osmotic potential of −0.035 MPa of detergent. A laundry detergent concentration of 5 g L −1 combined with drought reduced plant height, leaf area, fresh weight of leaves and stems, and relative water content of leaves. The seed germination stage was more sensitive to the laundry detergent than the early growth stage. It is recommended to irrigate wheat (Sirvan variety) at the germination stage with water that is not contaminated with detergent.

In this work, three multi-alkyl polyamines, i.e., pentahexadecyl diethylenetriamine (PHDETA), hexahexadecyl triethylenetetramine (HHTETA) and heptahexadecyl tetraethylenepentylamine (HHTEPA), were synthesized and evaluated as pure flow improvers for crude oil. Under certain conditions, PHDETA, HHTETA and HHTEPA were able to improve the flow properties of L401 crude oil samples by reducing the viscosity of the crude oil by 97.5%, 94.3% and 97.1%, respectively. The three synthesized alkyl polyamines PHDETA, HHTETA and HHTEPA were able to reduce the viscosity of L1316 crude oil to a maximum of 94.3%, 93.7% and 94.9%, respectively. The pour point of L401 crude oil could be greatly reduced by 3.1 °C, 3.3 °C and 3.4 °C with PHDETA, HHTETA and HHTEPA, respectively. The pour point of L1316 crude oil with PHDETA, HHTETA and HHTEPA was strongly decreased by 2.8 °C, 2.9 °C and 3.2 °C, respectively. Photomicrographs showed the co-crystallization of L401 and L1316 crude oil in the presence of PHDETA, resulting in the formation of a non-close-packed network of wax crystals. The multi-alkyl polyamines have multiple alkyl side chains that extend in different directions into the oil phase and can co-crystallize with the wax molecules, allowing the wax crystals to disperse.