Palm Oil Removal from Fabric Using Microemulsion-Based Formulations

Laundry detergency of palm oil on a polyester/cotton blend was measured using an anionic extended surfactant/nonionic secondary alcohol surfactant blend under conditions corresponding to ultralow oil/water interfacial tension microemulsion formation. The oil removal for the surfactant blend could exceed 90%, which was greater than that for either component surfactant alone or for a commercial liquid laundry detergent. Presoaking produced better detergency than increasing the number of wash cycles beyond two due to fabric abrasion (leading to a brightness decrease) with an excessive number of wash cycles. Higher oil contact angles and shorter oil droplet detachment times were found to correspond to higher detergency. High speed photography showed that snap-off occurred rather than roll-up for these systems.     

Photocatalytic activity of nanocrystalline mesoporous-assembled TiO2 photocatalyst for degradation of methyl orange monoazo dye in aqueous wastewater

In this work, nanocrystalline mesoporous-assembled TiO₂ photocatalyst was synthesized by a sol–gel process with the aid of a structure-directing surfactant and employed for the photocatalytic degradation of methyl orange azo dye (monoazo dye), as compared to various commercially available non-mesoporous-assembled TiO₂ powders. The experimental results showed that the synthesized mesoporous-assembled TiO₂ nanocrystal calcined at 500 °C provided superior decolorization and degradation performance to the non-mesoporous-assembled commercial TiO₂ powders. In addition, several operational parameters affecting the decolorization and degradation of methyl orange, namely photocatalyst dosage, initial dye concentration, H₂O₂ concentration, and initial solution pH, were systematically investigated, using the mesoporous-assembled TiO₂ nanocrystal. The optimum conditions were a photocatalyst dosage of 7 g/l, an initial dye concentration of 5 mg/l, a H₂O₂ concentration of 0.5 M, and an initial solution pH of 4.7, exhibiting the highest decolorization rate of methyl orange.     

Hydrogen production from water splitting under visible light irradiation using sensitized mesoporous-assembled TiO2–SiO2 mixed oxide photocatalysts

This work focused on hydrogen production from the photocatalytic water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled TiO₂–SiO₂ mixed oxide photocatalysts, of which the mesoporous-assembled TiO₂–SiO₂ mixed oxides with various TiO₂-to-SiO₂ molar ratios were synthesized by a sol–gel process with the aid of a structure-directing surfactant. The effects of SiO₂ content, calcination temperature, and phase composition of the mixed oxide photocatalysts were investigated. The experimental results showed that the TiO₂–SiO₂ mixed oxide photocatalyst with the TiO₂-to-SiO₂ molar ratio of 97:3 and calcined at 500 °C provided the maximum photocatalytic hydrogen production activity. The characterization results supported that the 0.97TiO₂–0.03SiO₂ mixed oxide photocatalyst (with the suitable SiO₂ content of 3 mol%) possessed superior physicochemical properties for the photocatalytic reaction as compared to the pure TiO₂, particularly higher specific surface area, lower mean mesopore diameter, higher total pore volume, and lower crystallite size, which led to an enhanced photocatalytic activity.     

Hydrogen production over metal-loaded mesoporous-assembled SrTiO3 nanocrystal photocatalysts: Effects of metal type and loading

Mesoporous-assembled SrTiO₃ photocatalysts with different loaded metal co-catalysts (Au,Pt, Ag, Ni, Ce, and Fe) synthesized by the single-step sol–gel method with the aid of a structure-directing surfactant were tested for the photocatalytic activity of hydrogen production from a methanol aqueous solution under both UV and visible light irradiation. The Au, Pt, Ag, and Ni loadings had a positive effect on the photocatalytic activity enhancement, whereas the Ce and Fe loadings did not. The best loaded metal was found to be Au due to its electrochemical properties compatible with the SrTiO₃-based photocatalyst and its visible light harvesting enhancement. A 1 wt.% Au-loaded SrTiO₃ photocatalyst exhibited the highest photocatalytic hydrogen production activity with a hydrogen production rate of 337 and 200 μmol h⁻¹ g_cat⁻¹ under UV and visible light irradiation, respectively. The hydrogen diffusivity from the liquid phase to the gas phase also significantly affected the photocatalytic hydrogen production efficiency. An increase in the hydrogen diffusability led to an increase in the photocatalytic hydrogen production efficiency.     

Formation of W/O microemulsion based on natural glycolipid biosurfactant, mannosylerythritol lipid-a

Mannosylerythritol lipid-A (MEL-A) is a glycolipid biosurfactant abundantly produced from soybean oil by microorganisms at a yield of up to 100 g/L. In this study, the formation of water-in-oil (W/O) microemulsion based on the single component of MEL-A was confirmed using dynamic light scattering (DLS) and freeze fracture electron microscopy (FF-EM). DLS and FF-EM measurements revealed that the diameter of the microemulsion increases with an increase in water-to-surfactant mole ratio (W(0)) ranging from 20 to 60 nm, and the maximum W(0) value was found to be 20, which is as high as that of soybean lecithin. Glycolipid biosurfactant has a great potential for the formation of W/O microemulsion without using any cosurfactants.     

Mechanistic Studies of Particulate Soil Detergency: II: Hydrophilic Soil Removal

In this work, the removal mechanism of kaolinite and ferric oxide (model hydrophilic particulate soils) from hydrophilic (cotton) and hydrophobic (polyester) fabrics was studied using three surfactant types: sodium dodecyl sulfate (SDS), octylphenol ethoxylate (OP(EO)10), and cetyltrimethylammonium bromide (CTAB). This work investigated the relations between zeta potential, surfactant adsorption, contact angle, solid/liquid spreading pressure, and dispersion stability in washing solutions as compared to detergency performance and antiredeposition as a function of surfactant concentration and pH level. The SDS showed the best detergency for both particulate soils, followed by OP(EO)10, with CTAB being the least effective surfactant. For SDS, the electrostatic repulsion between fabric and soil was found to be the dominant force for hydrophilic particulate soil removal. For the nonionic surfactant OP(EO)10, electrostatics are also important and steric effects aid particulate soil detergency. Electrostatic forces and solid/liquid interfacial tension reduction aids CTAB detergency. These same detergency mechanisms have previously been found for the case of hydrophobic soil removal from fabrics. Dispersion stability did not prove to be a dominant mechanism governing particulate soil detergency. From the SEM photos of soiled fabric, ferric oxide attaches to the fabric surface with no entrapment between fabric yarns; moreover, ferric oxide tends to form larger aggregates on cotton compared to polyester fabric. The adhesion of larger particles is hypothesized to be weaker than the smaller ones. Therefore ferric oxide can be more easily removed from cotton fabric than polyester. The SEM photos for kaolinite show little visual difference in particle agglomeration on polyester compared to cotton. Removal of kaolinite from cotton was found to be higher than from polyester, but there is less difference than for ferric oxide.     

Enhanced triolein removal using microemulsions formulated with mixed surfactants

In previous work, a microemulsion-based formulation approach yielded excellent laundry detergency with hydrophobic oily soils hexadecane and motor oil. In this work, the same approach is used in detergency of triolein, which is a model triglyceride, some of the most difficult oils to be removed from fabric. The linker concept was applied in formulation of the microemulsion system. Three different surfactants were used: (i) dihexyl sulfosuccinate, an ionic surfactant with a moderate hydrophile-lipophile balance (HLB); (ii) secondary alcohol ethoxylate, a lipophilic nonionic surfactant with a very low HLB; and (iii) alkyl diphenyl oxide disulfonate (ADPODS), a hydrophilic anionic surfactant with a very high HLB. The phase behavior and interfacial tension (IFT) of the surfactant systems were determined with different concentrations of ADPODS. The results indicate that as the HLB of the system increases, a higher salinity is required to shift the phase transition from Winsor Type I to Type III to Type II. The three formulations at different salinities were used in detergency experiments to remove triolein from polyester/cotton sample fabric. The results showed that there were two peaks of maximum detergency in the range of salinity from 0.1% to 10% NaCl. The higher the hydrophilicity of the system, the higher the salinity required for maximum detergency. The results of the dynamic IFT and the detergency performance from two rinsing methods lead to the hypothesis that one of these maxima in detergency results from a spreading or wetting effect. The other maximum in detergency is believed to be related to ultralow IFT associated with oil/water middle-phase microemulsion formation. Triolein removal exceeding 80% was attained, validating the microemulsion approach to detergency.     

Dissolution of Soap Scum by Surfactant. Part II: Effects of NaCl and Added Chelant on Equilibrium Solubility and Dissolution Rate of Calcium Soap Scum in Amphoteric Surfactant Solutions

The effects of solution pH and NaCl on the equilibrium solubility and dissolution rate of a model soap scum (calcium octadecanoate or calcium stearate) in aqueous solutions of dimethyldodecylamine oxide surfactant (DDAO) with and without chelant disodium ethylenediaminetetraacetate are reported. The equilibrium solubility and dissolution rate of soap scum increased with increasing solution pH when the chelant was added in the DDAO system while in the chelant-free systems the opposite trend was observed. The added NaCl has an ambiguous effect on the solubility and dissolution rate of soap scum in the absence of chelant, but a small level of added NaCl reduces both solubility and the dissolution rate constant in the presence of chelant. Both equilibrium and kinetics of dissolution are maximized at high pH with DDAO/chelant and no added salt.     

Hydrogen production from alcohol wastewater with added fermentation residue by an anaerobic sequencing batch reactor (ASBR) under thermophilic operation

The objective of this study was to investigate the enhancement of hydrogen production from alcohol wastewater by adding fermentation residue using an anaerobic sequencing batch reactor (ASBR) under thermophillic operation (55 °C) and at a constant pH of 5.5. The digestibility of the added fermentation residue was also evaluated. For a first set of previous experiments, the ASBR system was operated to obtain an optimum COD loading rate of 50.6 kg/m³ d of alcohol wastewater without added fermentation residue and the produced gas contained 31% H₂ and 69% CO₂. In this experiment, the effect of added fermentation residue (100–1200 mg/l) on hydrogen production performance was investigated under a COD loading rate of 50.6 kg/m³ d of the alcohol wastewater. At a fermentation residue concentration of 1000 mg/l, the produced gas contained 40% H₂ and 60% CO₂ without methane and the system gave the highest hydrogen yield and specific hydrogen production rate of 128 ml/g COD removed and 2880 ml/l d, respectively. Under thermophilic operation with a high total COD loading rate (51.8 kg/m³ d) and a short HRT (21 h) at pH 5.5, the ASBR system could only break down cellulose (41.6%) and hemicellulose (21.8%), not decompose lignin.