Performance of conventional drinking water treatment following dispersant remediation of an oil spill in surface water.

Physical remediation such as the use of booms has been applied for most oil-spill cleanup activities in surface water. The application of dispersants has been controversial primarily due to the unknown impacts on drinking water sources. This study investigated changes in surface water quality following dispersant application to crude oil spills and the subsequent impact on the efficiency of ballasted flocculation, a physicochemical treatment process applied in many drinking water treatment plants (DWTP). Contamination of surface water was performed in the presence of crude oil concentrations (109 ± 13 mg/L) with and without dispersants. Water quality parameters such as turbidity and UVA254 were monitored and ballasted flocculation efficiency was assessed based on water quality as well as the removal of oil droplets, residual dispersant, and petroleum hydrocarbons as total organic carbon (TOC). Results showed that the measured water quality parameters except TOC are unsuitable indicators of petroleum hydrocarbon contamination in surface water. However, TOC lacked sensitivity when used in settled water to detect hydrocarbon contaminants. Although ballasted flocculation efficiency was not limited by the presence of crude oil and low dispersant concentrations when an optimized alum dose was applied (41 mg dry alum/L), the process was unable to remove other dispersant-related compounds that are not identifiable by the monitored water quality parameters. Measured concentrations of these compounds in settled waters were above the U.S. EPA's aquatic life benchmark (40 µg/L). Findings would be beneficial to DWTP in their efforts to upgrade their treatment processes and prepare oil-spill contingency plans.

One-step processing of highly viscous multiple Pickering emulsions.

HYPOTHESIS: Solid-stabilized Pickering emulsions have attracted a lot of attention recently due to their surfactant-free character, and exceptional stability. At the moment, how the viscosities of the liquid phases impact the processing of Pickering emulsions remain to be clearly understood - it is however an important parameter to consider when developing chemical engineering processes employing these multiphase liquids. Our first assumption was that the amount of emulsified dispersed phase would drastically decrease as viscosity increases. EXPERIMENTS AND FINDINGS: In this work, we demonstrate that double water-in-oil-in-water (W/O/W) Pickering emulsions are obtained in a single processing step when using very high viscosity silicone oils (≥10,000 cSt) and a single type of sub-µm silica particles modified with two grafted silanes and sodium alginate. The formation of water sub-inclusions proceeds via a phase-inversion mechanism. These sub-inclusions are subsequently stabilized and retained in the oil phase due to its viscosity, limiting sub-inclusions mobility, and the presence of adsorbed particles forming dense layers at oil-water interfaces, acting as barriers. The process we present is simple, requires a minimum number of components, and allows the preparation of multiple emulsions which could then be used to efficiently protect and/or transport a variety of sensitive encapsulated compounds.

Sodium alginate-grafted submicrometer particles display enhanced reversible aggregation/disaggregation properties.

In this article, we demonstrate that submicrometer particles with surface-grafted sodium alginate (SA) display enhanced and reversible aggregation/disaggregation properties in aqueous solution. 300 nm silica particles were first functionalized with an aminosilane coupling agent, followed by the grafting of pH-sensitive SA, as confirmed by zeta potential, XPS and FTIR analyses. The SA-modified particles show enhanced aggregation properties at acidic pH compared to unmodified silica, with a 10 times increase in average aggregate diameter. The process is reversible, as the aggregates can be broken and dispersed again when the pH is increased back to 7.0. As a result, the sedimentation rate of SA-modified particles at pH 3.0 is both significantly faster and complete compared to the unmodified particles. This enhanced aggregation is most likely due to the formation of intermolecular hydrogen bonds between neighboring SA-modified particles. This work illustrates how surface-grafted macromolecules of natural origins can be used to tune interparticle interactions, in order to improve separation processes.