No abstract

No abstract

Contamination of water from nanomaterials will be an emerging problem in the future due to incorporation of nanomaterials in many commercial products and improper disposal of waste materials. In this report, electrospun polyvinyl alcohol nanofibers (PVA NFs) with diameters ranging between 300 and 500 nm were used for the extraction of nanosized contaminants from the aqueous environment. To obtain the best extraction efficiency, surface hydroxyl groups of PVA NFs were chemically modified with functional groups, such as thiols and amines. Two model nanoparticles (silver and gold) dissolved in water were used for adsorption studies. Depending on the nature of the surface functionalities, the fibers showed unique ability to adsorb nanoparticles. The extraction studies revealed that the amine and thiol modified PVA NFs showed 90% extraction efficiency for both silver and gold nanoparticles. The thiol and amine functionalized PVA NFs showed maximum adsorption capacities (Q(t)) towards Au NPs, which were around 79-84 mg g(-1). Similarly for Ag NP extraction, amine functionalized PVA NFs showed a value for Q(t) at 56 mg g(-1). Our results highlight that functionalized nanofibers have high extraction efficiency for dissolved nanoparticles in water and can be used for removal of the nanocontaminants from the aqueous environment.

The increased use of nanoparticles in various commercial products enhances the contamination of nanomaterials in the environment which may cause serious health concern in the near future. To address this problem, new methods need to be developed for removal of nanomaterials from the environment. In this report, we explored the removal of nanoparticles from water using cellulosic nanofibers extracted from a renewable source such as sugarcane bagasse. The nanofibers were coated with chitosan to introduce additional functional groups on the surface. The designed cellulosic nanofibers showed high extraction efficiency (80-90%) towards silver (Ag) and gold (Au) nanoparticles. The maximum adsorption efficiency (Q t ) towards citrate and polyvinylpyrrolidone (PVP) capped Ag-nanoparticles using chitosan coated cellulose nanofibers was 13.1 mg g À1 . Similarly, Q t values for citrate and PVP capped Au-nanoparticles were 17.9 mg g À1 and 17.4 mg g À1 , respectively. The adsorption of nanoparticles onto the nanofibers was confirmed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Even though we used spiked solutions for the current study, it is expected that such low cost, highly abundant nanofibers may be used for setting up a large-scale nanoparticle removal system for water purification.

Carbon nanoparticles often contain several tunable functional groups on the surface that bring about many interesting and unique properties. In this study, a novel class of hydrophilic carbons on a nanometer scale was prepared from waste biomass with hydroxyl groups on the surface. Electron microscopic studies showed that the prepared carbon particles have sizes of 50-70 nm. Raman spectroscopy revealed that these particles were amorphous in nature with no aromatization. Zirconium(IV) was then chemically immobilized to the hydroxyl group of the carbon under basic conditions. It was found that zirconium (Zr) ions were successfully bound onto the nano-scale carbons (NSC). The toxicity of the Zr-immobilized NS carbon (ZNC) was investigated using breast cancer stem cells (MCF7); no cytotoxic effects on the cells were found after 5 days of incubation. The nano-scaled adsorbent was used for the adsorption of arsenic. It was found that 70 to 75% of its final adsorption was achieved within the first 10 min, much faster than many other adsorbents. The high oxophilicity of Zr(IV) ions results in the fast adsorption of arsenate anions. The Langmuir equation well described the adsorption isotherm; the maximum adsorption capacity was around 110 mg g À1 at the optimal pH. The commonly existing anions such as fluoride, phosphate and nitrate as well as humic acid had no significant effects on the uptake. However, silicate ions had a large influence on the adsorption. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopic analysis revealed that the negatively charged arsenate forms chemical linkages with the ZNCs (via the electropositive metal (Zr 4+) precursor). From this study it was concluded that adsorption by ZNC would be a better solution for arsenic contaminated surface and groundwater.