Volume 60, Issue 5

Gastric-lipase (GL) binding to a lipid layer was investigated for the phase of the layer adjusted with the ratio of stigmasterol to the lipid using surface plasmon resonance. While the layer was formed on the hydrophobic surface, more stigmasterol led to lower surface density only in the dipalmitoylphosphatidylcholine (DPPC) layer. The addition of stigmasterol was believed to transform the phase (condensed liquid-phase) of DPPC layer closer to the phase (expanded liquid-phase) of dioleoylphosphatidylcholine (DOPC) layer. At a ratio greater than 15:85, the effect of the stigmasterol on the DPPC was saturated. The adsorption behavior of GL showed the similar trend with the lipid formation. The adsorption increased with the increase in the ratio of stigmasterol to lipid up to 15:85. On the DOPC layer of the expanded liquid-phase, the most adsorption seemed to occur and was indistinguishable from that in the DPPC layer of 15:85. The surface density of the adsorbed GL was interpreted into the fraction of the stigmasterol-dependent DPPC, 0.33, 0.67, and 1.00 for 10:90, 5:95, and 0:100 of DPPC. Furthermore, the equilibrium constant was between 1 × 10 13  M −1 and 2 × 10 13  M −1 and the kinetics of the adsorption showed an increase in the adsorption rate constant with the increase of the ratio up to 15:85.

Biosurfactants are amphiphilic compounds synthesized from plants and microorganisms and are known for their high biodegradability, low toxicity, and eco-friendliness. They have diverse applications in industrial and environmental fields, including oil recovery, bioremediation, and cleaning up hydrocarbons from polluted areas. Surfactin is a potent lipopeptide biosurfactant produced by Bacillus subtilis bacteria. In this study, we produced surfactin by B. subtilis using cassava wastewater as the fermentation medium. This production was monitored by high performance liquid chromatography (HPLC). Approximately 600 mg L −1 of surfactant was produced. The oil displacement test was then performed to evaluate the effectiveness of crude and purified surfactin compared to a synthetic surfactant and a biosurfactant. Three types of surfactants were tested: the synthetic surfactant sodium lauryl sulfate (SDS), the commercial biosurfactant rhamnolipid (Rh), and surfactin in its crude form and purified one – after acid precipitation. The analysis results indicated that surfactin, in both its crude and purified forms, was more effective at dispersing oil than the other surfactants tested, even at lower concentrations. This suggests that biosurfactants have great potential as a more sustainable and effective alternative to petroleum-derived synthetic surfactants. Surfactin can be applied without the need for downstream processes.

Cocamidopropyl betaine is a coconut oil-based surfactant that is widely used in cosmetics and personal care products due to its milder and less irritating properties compared to conventional petroleum-based surfactants. Palm kernel oil can be used for the synthesis of betaine (palm kernel amidopropyl betaine), following the same route as for the synthesis with coconut oil via two reaction steps. However, there was little information on the optimal operating conditions for each process. The method for the production of betaine and its operating conditions were studied in order to obtain a compatible betaine product with better properties than those of the commercial product. The studied method and operating conditions allowed the production of low viscosity betaine with a higher surfactant content (31.55 wt%) than that of the commercial betaine products (25.10 wt%). In addition, other feedstocks such as coconut oil, split palm kernel oil and coconut oil-based fatty acid methyl ester were used in this study to produce betaine from low-cost production.

This paper reports the novel synthesis of an interpenetrating polymer network (IPN) from semi-IPN. This semi-IPN is based on naturally occurring Colocasia esculenta corn starch. The toxicity levels were compared through various biodegradation methods. The polymer network was synthesised from the corresponding semi-IPN via a green pathway by using green solvent (water) and polyvinyl alcohol (PVA) as secondary monomer. The biodegradability of synthesized IPN was tested by vermi-composting, composting and soil burial methods. The study was divided into three stages that lasted up to 70 days. The synthesised IPN degraded 78.94 %, 69.23 % and 67.24 % within 70 days by vermi-composting, composting and burying in the soil, respectively. This was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with electron dispersion analysis (SEM-EDX) for each stage. Therefore, the system could be considered for agrochemical release without affecting soil fertility.

In this work, we performed the cloud point extraction with low and high concentrations of Cu(II) and Cr(III), two particularly toxic metallic pollutants, that have been shown to have adverse effects on human health and the environment. Removal of the metal ions was achieved in the presence of Triton X-100 as a non-ionic surfactant and N,N′-bis(salicylidene)-thiocarbohydrazide as a chelating ligand in concentrated chloride medium. The behavior of the Schiff base was initially investigated in homogeneous DMSO-water and micellar Triton X-100-water media. The obtained values of the acid constants show that the extractant is more acidic in micellar media than in pure aqueous medium. The recorded cloud point temperatures of Triton X-100 are significantly impacted by the sodium chloride concentration, the surfactant concentration, and the Schiff base ligand. Under the optimised experimental conditions, a quantitative extraction of Cu(II) and a maximum extraction rate of 74 % of Cr(III) were obtained. The reduction of the metal concentration from 10 −3  mol L −1 to 10 −6  mol L −1 resulted in a reduction of the temperature by 10 °C and a reduction of the contact time from 10 h to 3 h.

Chitosan and hydroxyapatite are commonly used materials for adsorption. In this work, chitosan was modified by polyethylene glycol and maleic anhydride. Subsequently, a hydroxyapatite-chitosan composite was synthesised by precipitation. The composite was characterised and analysed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Adsorption experiments were used to investigate the effects of external factors such as different pH values, adsorbent dosage, adsorption time and initial nickel ion concentration on the adsorption capacity of Ni 2+ and to discuss the mechanism of Ni 2+ removal by composites. The results show that the hydroxyapatite-chitosan composite has significant adsorption of Ni 2+ . The adsorption capacity of the hydroxyapatite-chitosan composite for Ni 2+ reaches 63.8 mg g −1 . The adsorption process is consistent with the pseudo-second-order kinetic model and the Langmuir isothermal model.

The influence of replacing water with isopropanol (IP) on the rheological properties of aqueous solutions containing wormlike micelles (WLMs) prepared by mixing cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) at 25 °C was investigated. Viscosity of CTAB aqueous solutions exhibits two maxima and one minimum with increasing amounts of NaSal, consisting of entangled WLMs. When water is replaced by increasing amount of IP, the viscosity maxima and the minimum changes drastically. The elastic plateau modulus G ° of these solutions remains almost the same with increasing IP contents (up to ∼5 wt%), whereas their relaxation time changes drastically. Critical micelle concentration (CMC) of CTAB has increased with further IP addition, indicating an increase in the micellar hydrophilicity. For WLMs at minimum viscosity, increasing addition of IP (>5.0 %) to WLMs at maximum and minimum viscosities, leads to a drastic decrease in the elastic modulus G °, indicating the formation of smaller micellar aggregates. The influence of IP as a co-solvent on the WLMs rheological properties is also compared to that of glycerol and 1,3 butanediol (1,3 BD) for the same NaSal/CTAB viscoelastic system.

The effect of the ionic liquid analogue tetrabutylammonium bromide on the aggregation behaviour of the cationic surfactant dodecyltrimethylammonium bromide in aqueous medium was investigated with volumetric and compressibility measurements over a wide temperature range (293.15–313.15) K. The data obtained were used to obtain density data. Based on the density data obtained, the volumetric properties (apparent molar volumes and partial molar volumes) of the surfactant in unimeric and micellar forms were evaluated and discussed in terms of the respective ionic and dipolar interactions. The data obtained were analysed to determine the effects of (i) temperature and (ii) salt added to the surfactant. The results were also interpreted in terms of the molecular interactions occurring in the binary mixtures of the present study. The addition of tetrabutylammonium bromide has a lowering effect on the CMC values of the surfactant studied in aqueous medium.

In the present work, the anionic biomass surfactant cardanol sulfonate (CDS) was compounded in different molar fractions ( α 1 ) with the commonly used amphoteric surfactant lauryl amidopropyl betaine (LAB) and the nonionic surfactant alkyl glycoside (APG), respectively. By measuring the surface tension of the binary compound system, the relationship between the surface chemical properties of the compound system and α 1 was investigated, and then the synergistic parameters and thermodynamic parameters of the compound system were calculated. The results showed that both CDS/LAB and CDS/APG systems exhibited non-ideal mixing behavior. The CDS/LAB compound system has the best synergistic effect when the two components were mixed in a 1:1 molar ratio, corresponding to a CMC of 3.06 × 10 −4  mol L −1 and a γ CMC of 32.60 mN m −1 . The formation of mixed micelles was a spontaneous exothermic process driven by enthalpy. The CDS/APG compound system at the molar ratio of n (APG): n (CDS) = 9:1 has a more significant synergistic effect, corresponding to a CMC of 1.13 × 10 −4  mol L −1 and a γ CMC of 29.10 mN m −1 . The application performance of the compound systems was the best at the optimal molar ratio, which confirms the existence of synergistic effect in the compound systems.

A series of novel gemini surfactants ( m -E 2 Ph- m ) with ester groups and a benzene ring as rigid spacer were synthesized and characterized by IR, 1 H NMR and Mass spectrometry. The effect of hydrophobic chain length on the surface properties and aggregation behavior of the gemini surfactants were investigated by the measurements of surface tension, electrical conductivity, fluorescence. The critical micelle concentration (CMC) of these surfactants decreases with increasing alkyl chain length. The thermodynamic parameters exhibited that the micellization was a spontaneous and exothermic process in environment. The micellization process became more beneficial with the increase of alkyl chain length and the decrease of temperature.