A novel route to the engineering of zirconium immobilized nano-scale carbon for arsenate removal from water

Abstract

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⁻¹ 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 (Zr⁴⁺) precursor). From this study it was concluded that adsorption by ZNC would be a better solution for arsenic contaminated surface and groundwater.