Land Risk Management Research
Parametric Evaluation of Arsenic Adsorption and Desorption on Titanium Dioxide Nanoparticles
- Parametric Evaluation of Arsenic Adsorption and Desorption on Titanium Dioxide Nanoparticles
- Relating Metal Speciation to Bioavailability in Contaminated Sediments
- Release of Heavy Metals from Ironite
- Environmental Transport and Transformation of Nanomaterials
This two-phase study investigates a new approach to arsenic removal for the treatment of drinking water that uses titanium dioxide (TiO2) nanoparticles. Because the photocatalytic process has been proven effective, it is postulated that arsenic adsorption on TiO2 particles will be higher and more stable than with on iron and aluminum oxides. We will investigate adsorption and desorption of arsenic by:
- Evaluating the efficiency of titanium dioxide (Anatase) nanoparticles during the adsorption of arsenic
- Witnessing the effect of various physiochemical factors on the adsorption characteristics of TiO2 particles
- Analyzing arsenic desorption from treatment residuals
The parameters that control the adsorption and desorption of arsenic are pH, redox potential, initial contaminant concentration, solid solution ratio, and the surface structure of TiO2 particles.
The research plan is divided into two main studies:
- Adsorption of arsenic, predominantly As (V) on TiO2 particles as a function of:
- Solution pH
- Solid:solution ratio
- Initial contaminant concentration
The surface properties of the TiO2 particles will also be determined with respect to change in the point of zero charge (PZC) and surface area and the effect of these properties on As (V) removal.
- Desorption of arsenic from the nano-sized particles. The solid treatment residue would be subjected to leaching tests, including the regulated Toxicity Characteristics Leaching Procedure (TCLP). Because the mechanism of desorption is pH-dependent, the effect of the aforementioned factors would also be investigated with respect to arsenic desorption.
Special attention will be paid to the characterization of the TiO2 particles (EXAFS, XPS, SEM, and XRD) prior to their treatment of arsenic and on the residual. Data obtained from the spectroscopic and microscopic analysis will help determine the mechanisms for arsenic adsorption and desorption. Arsenic total content and speciation analysis will be performed using ICP-AES.
The primary objective of this research is to develop novel treatment technologies for arsenic removal. The use of TiO2 nanoparticles for arsenic removal will greatly reduce operational cost, while improving stability of spent residuals. Prediction of arsenic leaching from these spent residuals will also be made based on their desorption mechanisms. Mechanistic modeling approach will be used to aid the development of more accurate geochemical codes as well as short-and long-term waste management programs. Thus, this research will help to solve many problems associated with arsenic treatment and disposal.
U.S. EPA National Risk Management Research Laboratory
Land Remediation and Pollution Control Division
26 W. Martin Luther King Dr.
Mail Code: 190
Cincinnati, OH 45268