HR: 08:30h
AN: B31A-01    [Abstracts]
TI: Arsenite Sorption by Drinking-Water Treatment Residuals: Redox Effects
AU: * Makris, K C
EM: konstantinos.makris@utsa.edu
AF: Univ. of Texas, San Antonio, 6900 N Loop 1604 W, San Antonio, tx 78249 United States
AU: Sarkar, D
EM: dibyendu.sarkar@utsa.edu
AF: Univ. of Texas, San Antonio, 6900 N Loop 1604 W, San Antonio, tx 78249 United States
AU: Datta, R
EM: rupali.datta@utsa.edu
AF: Univ. of Texas, San Antonio, 6900 N Loop 1604 W, San Antonio, tx 78249 United States
AB: Arsenic (As) is a major human carcinogen and could pose a serious human health risk at concentrations as low as 50 ppb in drinking water. Elevated As concentrations in soils currently used for residential purposes (located on former agricultural lands amended with arsenical pesticides) have increased the possibility of human contact with soil-As. Studies have shown that As bioavailability in the environment is primarily a function of its chemical speciation, which depends upon the redox potential. Arsenic toxicity and carcinogenicity to living organisms is primarily due to exposure to the reduced species of As - arsenite, i.e., As(III), rather than the oxidized species - arsenate, i.e., As(V); the mobility of As(III) is much higher than As(V). One of the most promising methods to decrease the mobility of arsenite in the soil-water system is promoting its retention onto amorphous Fe/Al hydroxides. Drinking-Water Treatment Residuals (WTRs) are an inexpensive source of such Fe/Al hydroxides, which can be land-applied following the USEPA-regulated biosolids application rules. The WTRs are byproducts of drinking-water purification processes and generally contain sediment, organic carbon, and Al/Fe hydroxides. The hydroxides are typically amorphous and have tremendous affinity for oxyanions (e.g., arsenate). Preliminary work showed that WTRs are characterized by large internal surface area and porosity that partly explains their high affinity for As(V). The current study examines the potential of two WTRs (Fe-based and Al-based) to adsorb arsenite from solution. We hypothesize that As(III) adsorption onto the Fe-based WTR (whose stability is highly redox-sensitive) would be vastly different from the adsorption of As(III) onto the redox-insensitive Al-based WTR. Our main objective is to characterize As(III) sorption by both Fe- and Al-based WTRs by changing critical factors, such as the solid:solution ratio, contact time, and initial As(III) load. Results from this study are expected to identify the optimal conditions for As(III) sorption onto WTRs as a function of solution pH and redox potential. Potential desorption of the retained As will be assessed in batch studies using phosphate as the competing ligand.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2005 Joint Assembly