Benign-by-Design: Synthesis of Engineered Silicon Nanoparticles and their Application to Oil Sands Water Contaminant Remediation

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  • Oil sands are naturally occurring mixtures of sand or clay, water, fine silts, and bitumen. The oil sands extraction process consumes large volumes of water (i.e., ca. 3 barrels of fresh water for every 1 barrel of oil). Following the extraction of bitumen from the oil sands, a tailings slurry is produced that consists of oil sands process-affected water (OSPW), sand, silt, clay particles and trace quantities of unrecovered bitumen. This slurry is hydraulically transported to large containment facilities (i.e., open tailings ponds) that, in Alberta, currently occupy approximately 130 km2 with 200 million litres of mature fine tailings produced each day. These vast storage facilities pose a risk to the environment, wildlife, and society. There are many candidate technologies that could be applied to the treatment of OSPW. Advanced oxidation processes (AOPs) are particularly useful for degrading biologically toxic or non-degradable materials such as aromatics, pesticides, petroleum constituents, and volatile organic compounds in wastewater. In this report, we investigate the use of advanced oxidation processes via photocatalysts based on nanoparticles. Silicon nanoparticles were specifically engineered for water remediation by making them water soluble and more potent towards contaminant removal. Si nanoparticles of different sizes and morphologies were investigated for model contaminant (methanol) removal in the presence of UV light. A medium pressure UV lamp was used for the purpose. Control experiments were also performed to ascertain the extent of remediation by the Si nanoparticles. Effect of methanol concentration, nanoparticle concentration and exposure time of UV were systematically studied to optimize the remediation parameters. Moreover, a cost effective and high yielding synthetic protocol was also developed for large scale synthesis of Si nanoparticles which is crucial for scale up. Quantum yield calculations were performed on different Si nanoparticles and compared with titanium dioxide (TiO2), the most commonly proposed nanoparticle system.

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    Attribution 3.0 International