State Water Resources Research Institute Program

Project Id: 2009ND186B
Title: Development of GAC-NZVI Adsorbent for Arsenic Removal
Project Type: Research
Start Date: 3/01/2009
End Date: 2/01/2011
Congressional District: 1
Focus Categories: Treatment, Water Quality, Water Supply
Keywords: Arsenic, Granular Activated Carbon, Non zero valent iron, Nano particles, adsorption
Principal Investigator: Lin, Wei (North Dakota State Univeristy)
Federal Funds: $ 12,000
Non-Federal Matching Funds: $ 24,000
Abstract: The high levels of arsenic in North Dakota groundwater are attributed to the historical use of arsenic-based grasshopper bait as well as naturally occurring sources. In 2006, USEPA started to enforce a new regulation on arsenic in drinking water 10µg/L, downward from 50µg/L. This stringent new regulation presents a major compliance challenge to the existing water supply systems; 26 public water systems in North Dakota were required to reduce their arsenic levels to 10µg/L. The compliance is even tougher for the small rural community systems that until recently had few regulation requirements. Some small communities are attempting to apply for regulatory exemptions due to the high costs associated with meeting the new regulation. While exemptions offer temporary cost savings, they do not defend the population from possible negative health impact. There is, therefore, an urgent need to develop safe and affordable technologies to meet the new drinking water standard in small rural communities in North Dakota. Adsorption technology is considered an effective and efficient method to control the odor/taste and remove contaminants from drinking water. Among available adsorbents, activated carbon is widely used due to its commercial availability and excellent properties: huge specific surface area and advanced pore structure. Many of research found adsorption capacity for arsenic can be improved significantly after granular activated carbon (GAC) is impregnated with iron. This study includes three phases: Phase I - development of an iron impregnation method and characterization of GAC-Fe adsorbents; Phase II - improvement of the iron impregnation method and systematic study of arsenic adsorption capacity and kinetics; and Phase III - application of GAC-Fe adsorbents in removing arsenic from groundwater. Most of the work in Phase I was finished in 2008: a new synthesizing method was developed and GAC-Fe adsorbents with iron content 1.64%-12.13% were synthesized. SEM/EDS analyses of these GAC-Fe adsorbents demonstrated that iron distributes evenly inside GAC. Iron nano particles were found inside GAC with different morphologies (rod shape and round crystal); and iron was found both in crystalline (akaganeite) and amorphous (ferrihydrite) species. Arsenic adsorption tests using 5 GAC-Fe adsorbents indicated that GAC-Fe adsorbents have high affinity for arsenate and GAC-Fe adsorbent with 4.22% iron performed the best. Phase II covered most of the work in the 2009-2010 funding cycle, in which the synthesizing method was modified to improve impregnating efficiency, iron stability, and adsorption capacity. A new arsenic analytical method was established using GFAAS; and arsenic adsorption tests were carried out to determine adsorption capacity, as well as to investigate the relationship between iron content and arsenic adsorption capacity/efficiency at low arsenic concentrations that are common in groundwater. Phase III will focus on the impact of iron contents on arsenic adsorption kinetics, the impact of iron morphologies and species on arsenic adsorption capacity, adsorption tests on arsenite (As3+), adsorption tests on real groundwater samples from southern North Dakota, and column tests on synthetic groundwater and real groundwater samples from southern North Dakota.

Progress/Completion Report, 2009, PDF
Progress/Completion Report, 2010, PDF

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