Abstract
This work demonstrates very high removal rates (below the detection limit of 0.045 ppb) of inorganic arsenic from water using electrospun polyvinylidene difluoride (PVDF) membranes enhanced by the addition of functionalized graphene oxide in membrane distillation. This shows potential for applications in the many parts of the world suffering from arsenic-contaminated groundwater. These membranes were enhanced by the addition of reduced graphene oxide functionalized with superhydrophobic polyhedral oligomeric silsesquioxane molecules (POSS-rGO) into the spinning solutions. The flux of the best-performing rGO-enhanced membrane (containing 2 wt % POSS-rGO) was 21.5% higher than that of the pure PVDF membrane and almost double that of a commercial polytetrafluoroethylene (PTFE) membrane after 24 h of testing, with rejection values exceeding 99.9%. Furthermore, the flux of this membrane was stable over 5 days (∼28 L m–2 h–1) of continuous testing and was more stable than those of the PTFE and control membranes when treating a concentrated fouling solution of calcium carbonate and iron(III) sulfate heptahydrate. It also achieved higher permeate quality in these conditions. The Young’s modulus and ultimate tensile strength of the best-performing membrane increased by 38 and 271%, respectively, compared to the pure polymer membrane, while both had similar porosities of ∼91%.
Highlights
Arsenic contamination in groundwater is a growing problem, threatening drinking water supplies in many parts of the world.Locations such as the Ganga River Basin, encompassing considerable parts of India, Bangladesh, Nepal, and Tibet;[1] the Amazon Basin, including regions of Brazil and Peru;[2] and the Datong Basin in North West China[3] are but a few of the many areas that are experiencing dangerously high (>10 ppb4) levels of arsenic in the groundwater
polyhedral oligomeric silsesquioxane (POSS)-graphene oxide (GO) and POSS-rGO surveys expectedly show the presence of silicon and nitrogen as a consequence of the GO functionalization
High-performance electrospun polyvinylidene difluoride (PVDF) membranes were enhanced in terms of mechanical properties, hydrophobicity, and membrane distillation performance with the addition of hydrophobic POSS-functionalized graphene
Summary
Arsenic contamination in groundwater is a growing problem, threatening drinking water supplies in many parts of the world. Locations such as the Ganga River Basin, encompassing considerable parts of India, Bangladesh, Nepal, and Tibet;[1] the Amazon Basin, including regions of Brazil and Peru;[2] and the Datong Basin in North West China[3] are but a few of the many areas that are experiencing dangerously high (>10 ppb4) levels of arsenic in the groundwater. Arsenic can exist in four valence states: −3, 0, +3, and +5, with inorganic As3+ and As5+ being the most common and relevant to groundwater contamination. There are a variety of both natural and man-made sources of arsenic in the environment, and both must be monitored in order to mitigate risk to human health
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