Rapid screening of surfactant and biosurfactant surface cleaning performance

Surface Plasmon Resonance (SPR) and rubisco protein stain were used as tools to screen the effectiveness of detergent formulations in cleaning a protein stain from solid surfaces. Surfactant and biosurfactant-based formulations, with and without added protease, were screened for cleaning performance. Enzyme-free detergent formulations at 1500 ppm total surfactant were insufficient to cause complete surface cleaning, despite the high concentration of surfactant. The cleaning performance of a "home-made" formulation containing 2 ppm subtilisin A (SA) and 2 ppm sodium dodecyl benzyl sulphonate (SDOBS) was as efficient as the best amongst the three enzyme-free 1500 ppm formulations. The cleaning performance of 2 ppm SA in the absence of SDOBS was less effective than the combined formulation, even though 2 ppm SDOBS alone did not cause any protein removal. The observed synergistic performance was attributed to the cooperative mechanisms (chemical and physical attack) by which these two agents act on a rubisco stain. Replacing SDOBS in the enzyme-surfactant formulation with the same amount of surfactin biosurfactant (2 ppm) gave the best rubisco removal of all formulations examined in this study, irrespective of the surface chemistry underlying the protein film. It was found that 75% and 80% of immobilised rubisco stain could be removed from hydrophobic and hydrophilic surfaces, respectively, by the biosurfactant-SA formulation (compared with 60% and 65%, respectively, using the SDOBS-SA formulation). Our results suggest that it may be possible to generate fully renewable biochemical-based cleaning formulations that have superior cleaning performance to existing technologies. In developing optimised formulations, there is a pressing need for chip-based tools similar to that developed in this research

Adsorption of an anionic surfactant at air-liquid and different solid-liquid interfaces from solutions containing high counter-ion concentration

The self-assembly (adsorption) of the anionic surfactant, sodium dodecylbenzenesulphonate (SDBS), at air-liquid and different (octadecanethiol, β-mercaptoethanol, α-lipoic acid) solid-liquid interfaces from aqueous solutions containing high concentrations of counter-ion has been investigated. SDBS adsorption at the solid-liquid interfaces was obtained using surface plasmon resonance (SPR) while its adsorption at the air-liquid interface was extracted from surface tension measurements. The results have demonstrated that SDBS packing at the air-liquid interface is similar to its packing at the hydrophobic octadecanethiol-liquid interface. Additionally, SDBS packing at the three solid-liquid interfaces increases with increasing surface hydrophobicity, irrespective whether the surface is neutral or negatively charged. Nonetheless, SDBS adsorption is always within monolayer coverage (no evidence of bilayer or admicelle formation). The results have also revealed that SDBS affinity for the solid-liquid interfaces increases with increasing surface hydrophobicity. Furthermore, SDBS affinity for the air-liquid interface is more than 10-fold its affinity for the solid-liquid interfaces.Scopu

Influence of polyelectrolytes and other polymer complexes on the flocculation and rheological behaviors of clay minerals: A comprehensive review

Separation of clay minerals from industrial wastewaters is of great academic and practical importance. Current treatment techniques are either not economically viable, not environmentally friendly, or both. Thus, researchers are actively trying to develop optimal and more environmentally friendly wastewater treatment processes. Clay minerals like montmorillonite, bentonite, kaolinite and illite have numerous applications in various industries including, mineral processing, cosmetics, pharmaceuticals, paint, dyes, cement, concrete, functional fillers, paper making, clarification of wines and oils, water treatment and improving drilling mud properties. Their wide applications increased the volume and treatment complexity of water contaminated with them since they form highly stable suspensions in water. Flocculating agents such as polyelectrolytes have the potential to separate the above-mentioned minerals from industrial wastewater effluents. Polyelectrolytes are more effective and environment-friendly flocculants, in contrast to inorganic metal salts and some non-biodegradable synthetic polymers that pose serious hazards to human health and the environment. The development of polyelectrolytes is considered to be among the most important breakthroughs in solid-liquid separation processes, which have resulted in an improved treatment of water polluted with minerals. In the characterization of clay mineral separation using polyelectrolytes, it has been common practice in the past to either emphasize on the flocculation behavior of colloidal clay-polyelectrolyte suspensions (i.e., settling behavior or floc sizes) or on the behavior of networked clay-polyelectrolyte suspensions (i.e., filterability or dewaterability of sediment). However, flocculation and rheological parameters, which are very important factors in optimizing the wastewater treatment process, have rarely been reported in the literature. The aim of this paper, therefore, is to offer a comprehensive review of the state-of-the-art contributions for polyelectrolyte systems, focusing on the development of different types of polyelectrolytes and their applications in flocculating and dewatering clay minerals. Electrokinetics and rheological behavior of different clay minerals using different polyelectrolytes are critically evaluated. The effect of several parameters related to the clay mineral (type, composition), the polyelectrolyte (e.g., synthetic/natural, molecular weight, charge type, charge density, linear vs branched) and the flocculation medium properties (e.g., pH, ionic strength, clay mineral and polyelectrolyte concentration and type) are reviewed. This paper provides up-to-date progress in the treatment of water contaminated with clay minerals using various polyelectrolytes. The gaps and potential parameters of investigation in flocculation optimization studies are identified and more economical and environmentally friendly reagents in wastewater treatment are highlighted.Scopu

Demulsification of stable emulsions from produced water using a phase separator with inclined parallel arc coalescing plates

A novel and highly efficient oil-water separator equipped with a series of inclined multiple arc coalescence plates is developed and optimized for the removal of stable oil emulsions from produced water. The synthetic high salinity produced water with stable emulsions was prepared by mixing Catenex oil and the emulsifying surfactant (Armac T) with brine water. A series of experiments were performed to evaluate the effects of the arc coalescence plate geometry, produced water volumetric flow rate, influent oil concentration, and treatment temperature on the oil removal efficiency using the developed separator. Optimal coalescence plate arc geometry for maximum oil removal at different operating conditions was determined. Using the optimal coalescence plate arc geometry. , strong correlations between oil removal efficiency from produced water, volumetric flow rate, and treatment temperature were established. The results demonstrated that the developed oil-water separator is highly effective in the treatment of stable emulsions in produced waters due to the combined effects of chemical demulsification and oil droplet coalescence.Scopu

Strategies to Enhance ZnO Photocatalyst's Performance for Water Treatment: A Comprehensive Review

Despite the photocatalytic organic pollutant degradation using ZnO started in 1910?1911, many challenges are still ahead, and several critical issues have to be addressed. Large band gap, and short life-time of photogenerated electrons and holes are critical issues negatively affect the photocatalytic activity of ZnO. Various approaches have been introduced to overcome these issues including intrinsic doping, extrinsic doping, and heterostructure. This review introduces unique and deep insights into tuning of the photocatalytic activity of ZnO. It starts by description of how to tune the photocatalytic activity of pristine ZnO through tuning its morphology, surface area, exposed face, and intrinsic defects. Afterward, the review explains how the Z-scheme approach succeed to address the redox weakened issue of heterojunction approach. In general, this review provides a clear image that helps the researcher to tune the photocatalytic activity of pristine ZnO and its heterostructure.Scopu