Selective solvent filters for non-aqueous phase liquid separation from water

Abstract

Injectable filters permeable to water but impermeable to non-polar solvents were developed to contain non-aqueous phase liquids (NAPL) in contaminated aquifers, hence protecting downstream receptors during NAPL remediation. Filters were produced by injecting aqueous solutions of 0.01% chitosan, hydroxyethylcellulose and quaternized hydroxyethylcellulose into sand columns, followed by rinsing with water. Polymer sorption onto silica was verified using a quartz-crystal microbalance with dissipation monitoring. Fluorescence and gas chromatography mass spectroscopy showed low ppm range concentrations of non-polar solvents (e.g., hexane and toluene) in water eluted from the filters (in the absence of emulsifiers). The contact angles between polymer-coated surfaces and hexane or toluene were > 90°, indicating surface oleophobicity. Organic, polar solvents (e.g. tetrahydrofuran and tetrachloroethylene, TCE) were not separated from water. The contact angles between polymercoated surfaces and TCE was also > 90°. However, the contact area with polymer coated surfaces was greater for TCE than non-polar solvents, suggesting higher affinity between TCE and the surfaces. Emulsifiers can be used to facilitate NAPL extraction from aquifers. Emulsion separation efficiency depended on the emulsifier used. Emulsions were not separated with classical surfactants (e.g. Tween 20 and oleic acid) or alkaline zein solutions. Partial emulsion separation was achieved with humic acids and zein particles. Petroleum hydrocarbons (e.g. toluene) are common soil and groundwater contaminants because of their historical and current use in industry 1. Oil spills in surface waters can also occur during transport by boat, threatening surface water bodies and ecosystems in their proximity 2-4. In 1969, the oil well blowout in Santa Barbara, California released 4.1-4.6 million barrels of oil 5,6. Since then, American waters have been contaminated by more than 44 oil spills (each over 420,000 US gallons) 7. Spills have also occurred in Greece (where the Agia Zoni II released over 2,500 tonnes of oil in 2017 8), in India (where the Ennore spill released 160 tonnes of oil 9) and in east China (where the Sanchi oil tanker released 136,000 tonnes of natural-gas condensate in 2018 10). In addition to sorbents 11,12 , separation sponges have been developed to clean-up oil spills in surface waters. Separation sponges can be attached onto suction ports on boats, to selectively extract oil from surface waters 13. Oil-water separation sponges are produced using different methods, including dip coating, chemical vapor deposition, in situ chemical reaction, wet chemical reaction, thermal treatment, polymerization, electroless deposition, or carbonization 13. Different materials have been used to produce sponges for oil-water separation. For instance, graphene/polyurethane sponges have been obtained by in situ polymerization of N-methylpyrrolidone in the presence of graphene 14. These sponges have been used to selectively extract hexane, crude oil and engine oil flo...

Fabrication of the superhydrophobic natural cellulosic paper with different wettability and oil/water separation application

“…However, the stearic acid‐treated materials cannot be applied in the separation of oil‐in‐water emulsions due to the as‐prepared superhydrophobic filter paper can be changed into hydrophilicity by adjusting the drying temperature (200°C) 58 . In actual separation applications, the separation performance of filter paper will be different for organic solutions with different polarities 81 . The density and weight of organic solvent droplets can certainly affect the contact area.…”

“…The density and weight of organic solvent droplets can certainly affect the contact area. Meanwhile, the affinity between stearic acid coating and organic solvent, likely explaining why some oil‐in‐water emulsions could flow through stearic acid coated filter papers such as trichloromethane and petroleum ether 81 …”

Decontamination of water co-polluted by copper, toluene and tetrahydrofuran using lauric acid

“…11). www.nature.com/scientificreports/ Our previous studies showed that injectable filters could retain hydrophobic solvents such as toluene and hexane 51 , and that HEC + injectable filters retained diesel droplets emulsified by bacterial biosurfactants 81 . Here, HEC + injectable filters retain toluene containing Cu 2+ ions, as shown by ICP-OES analyses (Table 9).…”

Development of a novel experimental technique for the measurement of residual wall layer thickness in water-oil displacement flows

“…We use Nile red as the hydrophobic dye and tetrahydrofuran (THF) as organic solvent. The hydrophobic property of Nile red has previously been utilized for selective staining and detection of lipid droplets 13 , for protein characterization 14 , and to measure the effectiveness of injectable aqueous filters for subsurface separation of non-aqueous phase liquids 15 . Finally, ultraviolet-visible (UV–Vis) spetrophotometry is subsequently used to measure the dye concentration in the THF solution, which in turn is proportional to the residual oil volume.…”