HR: 1330h
AN: B33B-04    [Abstracts]
TI: Effect of Solution Properties on Arsenic Adsorption by Drinking Water Treatment Residuals
AU: * Nagar, R
EM: rnagar@utsa.edu
AF: University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249 United States
AU: Sarkar, D
EM: dsarkar@utsa.edu
AF: University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249 United States
AU: Datta, R
EM: rdatta@utsa.edu
AF: University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249 United States
AU: Sharma, S
EM: ssharma@utsa.edu
AF: University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, TX 78249 United States
AB: Arsenic (As) is a ubiquitous element in the environment. Higher levels of As in soils may result from various anthropogenic sources such as use of arsenical pesticides, fertilizers, wood preservatives, smelter wastes, and coal combustion. This is of great environmental and human health concern due to the high toxicity and proven carcinogenicity of several arsenical species. Thus there is a need for developing cost effective technologies capable of lowering bioavailable As concentrations in soils to environmentally acceptable levels. In-situ immobilization of metals using inexpensive amendments such as minerals (apatite, zeolite, or clay minerals) or waste by-products (steel shot, beringite, and iron-rich biosolids) to reduce bioavailability is an inexpensive alternative to the more expensive ex-situ remediation methods. One such emerging in-situ technique is the application of drinking water treatment residuals (WTRs). WTRs can be classified as a byproduct of drinking water treatment plants and are generally composed of amorphous Fe/Al oxides, activated C and cationic polymers. WTRs possess amorphous structure and generally have high positive charge. Because As is chemically similar to phosphorus, the oxyanions As (V) and As (III) may have the potential of being retained by the WTRs. Thus, it is hypothesized that WTRs retain As irreversibly, thereby reducing As biavailability. As mobility of arsenic is controlled by adsorption reactions, knowledge of adsorption of As by WTRs is of primary relevance. Although the overall rate of adsorption is dependent on numerous factors, review of the literature indicates that competing ions in solution play an important role in the overall retention of As; however, little work has been conducted to identify which ions provide the most competition. As arsenic adsorption appears to be influenced by the variable pH-dependent charges developed on the soil particle surfaces, the effect of pH is also of critical importance. Hence, the purpose of the present study is to investigate the effect of solution properties, such as pH, ionic strength and competing ions on the adsorption of As by WTRs and WTR amended soils. Three types of WTRs are being used, namely Fe- WTR, Al- WTR and Ca-WTR. Effect of pH is being studied by varying the pH values between 3 and 9. The solid/solution ratio has been fixed at 1:5 and a 24 h equilibration has been chosen based on the results of earlier adsorption experiments. Furthermore, As adsorption will be studied in presence of potentially competing ions such as phosphate, sulfate, and selenate. Keywords: Adsorption, water treatment residuals, oxyanions, in-situ remediation, Arsenic
DE: 0400 Biogeosciences
DE: 1803 Anthropogenic effects
DE: 4825 Geochemistry
DE: 4857 Pollution
DE: 4875 Trace elements
SC: Biogeosciences [B]
MN: 2005 Joint Assembly