| |
The degradation of our nation’s water quality and the resulting pollution is a critical issue that requires innovation in drinking water technologies. A case in point is the issue of arsenic (As) contamination of water resources, which is well-documented and a serious global health problem. In the US, an action limit has been put forth by the EPA, and the maximum contaminant level (MCL) previously set at 50µg As/L has been lowered to match the World Health organization’s (WHO) safe limit for drinking water of 10µg/L. There is a need for novel and efficient water treatment technologies to help meet the new MCL and protect water quality.
In this study, we take advantage of the increase in specific surface area and the decrease in kinetic reaction time offered by the nano-zero valent iron (nZVI) particles to remove As from aqueous solutions through a combination of sorption mechanisms. Batch sorption studies were conducted by equilibrating nZVI particles and As-contaminated water. The effects of key water chemistry parameters on As removal were investigated. nZVI particles were characterized by a combination of techniques including DLS, SEM-EDS, and XPS. Concentrations of As in aqueous phase were determined by hydride generation atomic fluorescence spectrometry (HG-AFS). The PVP-coated nZVI resulted in more stable and well dispersed suspensions as compared to bare nZVI. The experimentally determined rate (Kobs) of As removal from aqueous solutions by PVP-nZVI was 0.138 min-1 as compared to 0.056 min-1 for bare-nZVI. The determined maximum sorption capacities were 33.21mg As/g and 24.46 As/g for PVP-nZVI and bare-nZVI, respectively. However, this sorption capacity was negatively impacted by pH or increasing concentrations of competitive anions. Overall, the results show that PVP-nZVI particles can effectively remove As from solution down to levels below 10 µg/L. The ultimate goal of this research program is to develop a water filtration unit for removal of dissolved As and other toxic metals.
|