The role of carbon chain length in the attachment between microbubbles and aqueous solutions of ionic liquid.

HYPOTHESIS: The effects of varying carbon chain lengths (CCLs) and concentrations of aqueous solutions of imidazolium based ionic liquids on bubble particle attachment (BPA) will provide a better understanding in catering for the varying degrees of surface activities in the application of the flotation technology. The general trends of this study should also be applicable to homologous series of other cationic surfactants and ionic liquids. EXPERIMENTS: Zeta potentials of small air bubbles and bunker oil drops dispersed in aqueous solutions of n-methylimidazolium chloride ionic liquids (n=0, 2, 3, 6, 8, 10, 12) of concentrations ranging from 1000PPM to 8000PPM, as were interfacial tensions of these solutions with bunker oil (180cst) and contact angles made by air bubbles at interfaces between these solutions and thin layers of bunker oil on flat solid surfaces were investigated. Finally, interparticle forces analysis using the Derjaguin-Landau, Verwey-Overbeek (DLVO) theory is also included. FINDINGS: Analysis using the DLVO theory showed attractive forces between the oil particles and micro-bubbles are significantly more prevalent in short CCLs solutions of imidazolium-based ILs in low concentrations, namely [C0mim][Cl] and [C2mim][Cl] at a maximum zeta potential difference of 75.3mV. The results from CA measurements follows similarly whereby low concentrations of ILs with short CCLs were in favor for the bubble-particle attachment process with angles ranging between 93.95° for [C0mim][Cl] and 97.28° for [C2mim][Cl]. IFT which is important in reducing coalescence for the preferential BPA process to occur in flotation decreases with an increase of CCL and concentration of IL.

Bathroom greywater recycling using polyelectrolyte-complex bilayer membrane: Advanced study of membrane structure and treatment efficiency.

Polyelectrolyte-complex bilayer membrane (PCBM) was fabricated using biodegradable chitosan and alginate polymers for subsequent application in the treatment of bathroom greywater. In this study, the properties of PCBMs were studied and it was found that the formation of polyelectrolyte network reduced the molecular weight cut-off (MWCO) from 242kDa in chitosan membrane to 2.71kDa in PCBM. The decrease in MWCO of PCBM results in better greywater treatment efficiency, subsequently demonstrated in a greywater filtration study where treated greywater effluent met the household reclaimed water standard of <2 NTU turbidity and <30ppm total suspended solids (TSS). In addition, a further 20% improvement in chemical oxygen demand (COD) removal was achieved as compared to a single layer chitosan membrane. Results from this study show that the biodegradable PCBM is a potential membrane material in producing clean treated greywater for non-potable applications.

Extraction techniques for polycyclic aromatic hydrocarbons in soils.

This paper aims to provide a review of the analytical extraction techniques for polycyclic aromatic hydrocarbons (PAHs) in soils. The extraction technologies described here include Soxhlet extraction, ultrasonic and mechanical agitation, accelerated solvent extraction, supercritical and subcritical fluid extraction, microwave-assisted extraction, solid phase extraction and microextraction, thermal desorption and flash pyrolysis, as well as fluidised-bed extraction. The influencing factors in the extraction of PAHs from soil such as temperature, type of solvent, soil moisture, and other soil characteristics are also discussed. The paper concludes with a review of the models used to describe the kinetics of PAH desorption from soils during solvent extraction.

Remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAHs).

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic micropollutants which are resistant to environmental degradation due to their highly hydrophobic nature. Concerns over their adverse health effects have resulted in extensive studies on the remediation of soils contaminated with PAHs. This paper aims to provide a review of the remediation technologies specifically for PAH-contaminated soils. The technologies discussed here include solvent extraction, bioremediation, phytoremediation, chemical oxidation, photocatalytic degradation, electrokinetic remediation, thermal treatment and integrated remediation technologies. For each of these, the theories are discussed in conjunction with comparative evaluation of studies reported in the specialised literature.