Sita Krajangpan

Sita Krajangpan is a Ph.D. student in Civil Engineering at North Dakota State University. She holds a M.S. in Environmental and Hazardous Waste Management (Chulalongkorn University, Bangkok, Thailand, 2005) and a B.S. in Environmental Science (Chulalongkorn University, 2002) and a diploma in Analytical Chemistry (Chulalongkorn University, 2000). Currently, her research is focused on developing a metal nanoparticle delivery system for groundwater remediation.


Polymer Modified Zero-valent Iron Nanoparticles for Arsenic Remediation: Longevity and Ionic Strength Effect Studies (Final Phase)

Fellow: Sita Krajangpan

Advisor: Achintya Bezbaruah, Ph.D., Assistant Professor, Department of Civil Engineering, North Dakota State University.

Co-Advisor: Bret Chisholm, Ph.D., Director of Combinatorial Materials Research Laboratory, Center for Nanoscale Science and Engineering, North Dakota State University.

Matching Support:North Dakota State University.

Degree Progress: Ph.D. in Environmental Engineering expected in Fall 2009.

Project Background:

Zero valent iron (Fe0) nanoparticles (nZVI) have been used for groundwater remediation of various contaminants because of their unique physiochemical properties. Various chlorinated aliphatic hydrocarbons, explosive materials, and arsenic have been successfully remediated by nZVI. However, nZVI are not only highly reactive with the contaminants, but also rapidly react with surrounding media in the subsurface and other non-target compounds. Thus, significant loss of nZVI reactivity occurs before the particles reach the target contaminant. Additionally, strong Van der Waal and magnetic atteractions between particles causes agglomeration, limiting colloidal stability and reduction in reactive surface. Considering the requirements of an effective delivery system for nZVI, functionalized amphiphilic polysiloxane graft copolymers (APGC) are an ideal class of polymers for this application. The hydrophilic graft will increase colloidal stability of nZVI in an aqueous medium. The hydrophobicity of the polysiloxane polymer backbone will protect the nZVI from excessive oxidation by water/non-target compounds. The proposed APGC coated nZVI (CnZVI) was successfully synthesized under NDWRRI fellowship for 2007 and 2008. The new CnZVI here shown very good colloidal stability and enhanced contaminant degradation characteristics. The final goal of this new delivery vehicle is remediation TCE and arsenic (As) in groundwater environment. Groundwater contains monovalent (e.g., Na+, K+) and divalent (e.g., Ca2+, Mg2+) cations and they make water ionic. It is, therefore, important to know effects of ionic strength on CnZVI. Longevity (shelf-life) of the coated nanoparticles will be checked through sedimentation and degradation studies.

The present research is in continuation of the work proposed for the 2008 NDWRRI program.

Project Objectives:

The main objective of this study is to enhance the effectiveness and longevity of CnZVI for groundwater remediation. The specific objectives of the study are as follows:

  1. Fine tune the design of the modified nZVI (i.e., CnZVI) for effective degradation of Arsenic (and also TCE, NO3--N, and RDX),
  2. Determination of longevity (shelf-life) of CnZVI,
  3. Determine ionic strength effects on colloidal stability and contaminant degradation by CnZVI, and
  4. Study of corrosion characteristics of bare nZVI and CnZVI.


The nZVI, APGC, and CnZVI were successfully synthesized and characterized. The colloidal stability comparison between CnZVI and bare nZVI were completed. Batch experiments using CnZVI were conducted with replications and showed promising results in As, TCE, and NO3--N removal as compare to nZVI. Shelf-life of CnZVI (over 7 month-periods) showed stable colloidal stability. Ionic strength study showed no significant change in colloidal stability and TCE removal. SEM/EDX was used to study surface corrosion of the metal particles. The results indicate that CnZVI markedly protects nZVI surface from undesired corrosion.

Research Outcomes:


Successful development of a delivery vehicle for iron nanoparticles will have broader ramifications in the field of groundwater remediation. Targeted delivery of the nZVI will save resources and time needed for remediation of contaminants in the subsurface and, thus, will help in protecting our water resources. Successful development of a polymeric delivery vehicle (APGC) can also be pilot tested to create a reactive barrier/wall to contain the arsenic trioxide plume in southeast North Dakota. The results from this project will stimulate further research for the development of target specific delivery vehicles for contaminants of environmental concern.

Dr. Achintya Bezbaruah

Advisor: Dr. Achintya Bezbaruah,

Assistant Professor of Civil Engineering, North Dakota State Uhiversity, Fargo

Phone: (701) 231-7461
Fax: (701) 231-6185


Co-Advisor: Dr. Bret Chisholm

Senior Research Scientist at Center for Nanoscale Science and Engineering

North Dakota State University

Phone: (701) 231-5328