BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are common water resource and potable water pollutants that are often left undetected and untreated by municipal treatment systems in spite of the negative repercussions associated with their ingestion. The US EPA has classified these pollutants as priority pollutant, yet they are persistently present in a variety of water resources. In this review paper, we highlight the sources and reported concentrations of BTEX compounds in water and explore historical remediation techniques that have been applied such as bioremediation and natural attenuation. We also highlight emerging possibilities and future directions for remediation techniques, such as nanotechnology-based materials and novel green materials (tannins) that can be applied to ensure removal of these compounds in water.

This study examined the use of surface response methodology to investigate the influence of operating variables on the transesterification of waste cooking oil (WCO) to biodiesel over sodium silicate catalysts. The individual and interactive effects of three variables namely, reaction time, reaction temperature and amount of catalyst was evaluated using full 2 3 (+1) factorial design. The conversion of WCO to biodiesel was achieved through the transesterification reaction over the catalyst at a methanol-to-oil molar ratio of 6:1 in a batch reactor. Physicochemical properties of the sodium silicate catalyst were obtained using Fourier transform infrared spectroscopy (FT-IR) for surface chemistry, thermo-gravimetric analysis (TGA) for thermal stability, N 2 physisorption test for Brunauer-Emmett-Teller analysis and scanning electron microscopy (SEM) for morphology. The reaction temperature, reaction time and weight of the catalyst (expressed as a percentage of the amount of WCO) were varied to understand their effect on the yield of biodiesel via response surface methodology (RSM) approach. The BET analysis showed a surface area of 0.386 m 2 /g for the catalyst. Results from the transesterification reaction reveal that change in catalyst weight percentage had no considerable effect on the biodiesel yield and that there was no mutual interaction between the reaction time and catalyst weight percentage. The results also conveyed that the reaction temperature and reaction time were limiting conditions and a slight variation herein altered the biodiesel yield. The transesterification of WCO produced 57.92% maximum FAME yield at the optimum methanol to oil molar ratio of 6:1, catalyst weight of 2.5%, reaction time of 240 min and a reaction temperature of 64 • C. The variance ratio, VR < F value obtained from the cross-validation experiments indicate perfect agreement of the model output with experimental results and also testifies to the validity and suitability of the model to predict the biodiesel yields.

The oil producing and petroleum refining industries dispose of a significant amount of oily sludge annually. The sludge typically contains a mixture of oil, water and solid particles in the form of complex slurry. The oil in the waste sludge is inextractible due to the complex composition and complex interactions in the sludge matrix. The sludge is disposed of on land or into surface water bodies thereby creating toxic conditions or depleting oxygen required by aquatic animals. In this study, a fumed silica mixture with hydrocarbons was used to facilitate stable emulsion ('Pickering' emulsion) of the oily sludge. The second step of controlled demulsification and separation of oil and sludge into layers was achieved using either a commercial surfactant (sodium dodecyl sulphate (SDS)) or a cost-effective biosurfactant from living organisms. The demulsification and separation of the oil layer using the commercial surfactant SDS was achieved within 4 hours after stopping mixing, which was much faster than the 10 days required to destabilise the emulsion using crude biosurfactants produced by a consortium of petrochemical tolerant bacteria. The recovery rate with bacteria could be improved by using a more purified biosurfactant without the cells.

In this study, polyethersulfone (PES) was infused with iron nanoparticles (Fe-NPs) obtained from the leaf of pomegranate plant to enhance hydrophilicity of the PES membrane. The resulted nanocomposite Fe-NPs/PES membrane obtained via phase inversion was characterized using a scanning electron microscope (SEM) for the morphology; a texture analyzer for the mechanical strength; an atomic force microscope (AFM) for the surface roughness; and water contact angle measurement for the degree of hydrophilicity. The separation performance of the membrane was evaluated using BTEX-containing wastewater. SEM images show that Fe-NPs were distributed uniformly within the membrane with improved mechanical strength. Mechanical strength of PES was enhanced at increasing Fe-NPs loading from 1.2 MPa for the pure PES to 8.94 MPa for 20 wt.% Fe-NPs loaded membrane. AFM analysis reveals that membrane roughness increased with increase in Fe-NPs loading. Also, the contact angle measurement indicates that the hydrophilicity of the composite membrane was enhanced by the addition of Fe-NPs. The permeation properties reveal that pure water flux of the composite membrane increased with increasing Fe-NPs loading. In addition, the highest BTEX rejection obtained was 64.55% at 10 wt.% Fe-NPs loading when compared to the rejection 41.4% obtained from the pure PES membrane evaluated at similar conditions.

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