Transport af overflademodificeret kulstofnanorør gennem en Soil kolonne
Summary
Surface properties of a nanoparticle are important for their interaction with the surrounding medium. Therefore the surface modification of carbon nanotubes can be critical for their transport and retention through porous media. Here, lab scale column experiments are used to understand the possible transport and retention of these nanoparticles.
Abstract
Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.
Introduction
Med den seneste udvikling inden for nanoteknologi, der bruger forskellige typer af nanopartikler til at forbedre en række teknologier inden for brancher som informationsteknologi, energi, miljø, medicin, Homeland Security, fødevaresikkerhed og transport; en grundig forståelse af transport og opbevaring af nanopartikler i jord og grundvand er kritisk for risikovurdering og miljømæssige anvendelser af nanopartikler 1-3. Kulstofnanorør (CNT) er en af de mest producerede kulstofbaserede nanopartikler 2,4. CNTs er lange og cylindriske form af graphene med en diameter typisk under 100 nm og en længde i området fra 100 nm til 50 um. De har unikke egenskaber, som har accelereret deres anvendelse i mange applikationer, såsom elektronik, optik, kosmetik og biomedicinsk teknologi (f.eks kompositmaterialer) 5. Med øget brug, er der også en øget rISK til human eksponering og effekt på sundhed samt negative økologiske konsekvenser efter CNT og andre kulstof baserede nanomaterialer rådighed for miljøet 5-8.
Med ingen overflademodifikationer (ikke-funktionaliserede) CNTs er yderst hydrofobe og har tendens til at aggregere i en vandig opløsning. Funktionaliserede CNTs kan dog fortsat spredt og stabil i vandige opløsninger og anvendes til biomedicinske formål såsom drug delivery 9. Her er det vigtigt, at CNTs forbliver dispergeret og mobiliseret, så lægemidlet kan leveres i det menneskelige legeme 10. På den anden side, for at reducere miljørisici, er der behov for undersøgelser, der fokuserer på, hvordan man kan immobilisere CNTs for at undgå deres indgang til grundvandsmagasiner og drikkevand ressourcer 11. Nylige undersøgelser har rapporteret den toksiske virkning af CNTs om levende organismer og også risici for økosystemerne i form af CNTs ind og akkumuleres i fødekæderne, daCNTs er svære at nedbrydes biologisk 5,8. Selv med barrieresystemer på lossepladser indeholdende CNTs, kan det være muligt for CNTs at passere gennem barrierer. I sådanne tilfælde CNTs kunne træde i grundvandsmagasiner og overfladevandområder. Da CNT bortskaffelse regler ikke er veldefinerede og transport mekanismer er dårligt forstået, er det nødvendigt med en bedre forståelse af mobilitet CNTs at formulere og konstruktion svarende bortskaffelsessystemer 12. Derfor er det vigtigt at studere og forstå skæbne og transport af CNTs i porøse medier og effekten af fysiske og kemiske faktorer almindeligvis er til stede i undergrunden miljø overflademodificeret CNT tilbageholdelse.
En række forskning er blevet udført om effekten af solfangeren kornstørrelse 13-15, flow rate 16, og overfladeegenskaber af kornene 17 om transport af nanopartikler i porøse medier. Dog, systematiske undersøgelser af effekten af solution kemi (såsom pH og ionstyrke) om muligt deposition onto samler overflader er stadig begrænset 18-20. Derudover er den kombinerede effekt af fysiske faktorer, opløsning kemi af mediet, og overfladeegenskaber kulstofnanorør ikke godt forstået og varierer i forskellige litteratur. I denne undersøgelse vil en fremstillingsmetode til overfladebehandling af MWCNTs påvises sammen med en systematisk laboratorieskala søjle pakket med syre renset kvartssand vil blive anvendt til at undersøge transport, opbevaring og remobilisering af overflademodificerede CNTs mættede porøse medier .
Protocol
Representative Results
Discussion
Virkning af MWCNT funktionalisering
Som figur 2 bekræfter stabiliteten af funktionaliserede MWCNTs den observerede forskel i eluerede volumen MWCNT skyldtes funktionalisering og især på grund af tilsætning af carboxyl (-COOH) grupper til overfladen af MWCNTs (figur 3 og 4). I lignende funktionalisering processen blev tilstedeværelsen af oxygen bekræftes ved røntgen fotoelektronspektroskopi 14. Det har vist …
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors would like to acknowledge the support from the Department of Earth Sciences, Uppsala University for supporting part of this research.
Materials
| Name of Material/ Equipments | Company | Catalog Number | Comments/Description |
| MWCNT | Cheap Tubes Inc., USA | sku-03040304 | Purchased as semi-functionlized powder |
| Quartz sand | Sibelco Nordic, Baskarp, Sweden | B44 | Purchased with more than 91% silica sand |
| H2SO4 | VWR | 1.01833.2500 | 95-97% purity |
| HNO3 | VWR | 1.00441.1000 | 70% purity |
| HCl | VWR | 1.00317.2500 | 37-38% purity |
| H2O2 | VWR | 23615.248 | 30% purity |
| NaCl | VWR | 1.06404.0500 | 99.5% purity |
| NaOH | Sigma-Aldrich | S8045-500G | 99.99% pur pellets |
| Ultrasonic Homogenizer | Biologics Inc. Manassas, Virginia | Model 3000, 0-127-0002 | Operated for fix time interval |
| Sonicator (bath) | Kerry Ultrasonic Ltd | 1808 | Common bath sonicator |
| Peristaltic pump | Ismantec, Glattbrugg, Switzerland | ISM931 | Work with tygon tubing in the pump |
| Spectrophotometer | Hach Lange | DR500, LPV408.99.0001 | Operate with manual cuvette as well as automated sampling |
| pH meter | Metrohm | 781 | pH analysis |
| Glass column | Chromaflex | 420830-1510 | Column with adjustable cap |
| Fraction collector | Spectrum Labs Europe | CF-2, 124846 | Fixed at regular interval of time |
| Fraction collector tubes | VWR | 212-9599 | 6 ml volume glass tube |
| Hot plate stir | Thermo Scientific | SP131320-33 | Adjustable tempurature |
| Oven | Elektro Helios | 259 | For oven dry of sand |
| Balance | Mettler Toledo | AE 160 | For accurate weight |
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