Journal of Environmental Sciences 19(2007) 910–919 Effect of competing solutes on arsenic(V) adsorption using iron and aluminum oxides Youngran Jeong 1,2 , FAN Maohong 1,2, * , Johannes Van Leeuwen 1 , Joshua F. Belczyk 3 1. Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011, USA. E-mail: mfan@iastate.edu 2. Center for Sustainable Environmental Technology, Iowa State University, Ames, IA 50011, USA 3. Bailey PVS, Canonsburg, PA 15317, USA Received 9 October 2006; revised 5 December 2006; accepted 26 March 2007 Abstract The study focused on the effect of several typical competing solutes on removal of arsenic with Fe 2 O 3 and Al 2 O 3 . The test results indicate that chloride, nitrate and sulfate did not have detectable effects, and that selenium(IV) (Se(IV)) and vanadium(V) (V(V)) showed slight effects on the adsorption of As(V) with Fe 2 O 3 . The results also showed that adsorption of As(V) on Al 2 O 3 was not affected by chloride and nitrate anions, but slightly by Se(IV) and V(V) ions. Unlike the adsorption of As(V) with Fe 2 O 3 , that with Fe 2 O 3 was affected by the presence of sulfate in water solutions. Both phosphate and silica have significant adverse effects on the adsorption of As(V) adsorption with Fe 2 O 3 and Al 2 O 3 . Compared to the other tested anions, phosphate anion was found to be the most prominent solute affecting the As(V) adsorption with Fe 2 O 3 and Al 2 O 3 . In general, Fe 2 O 3 has a better performance than Al 2 O 3 in removal of As(V) within a water environment where multi competing solutes are present. Key words: adsorption; arsenic; iron oxide; aluminum oxide; sulfate; selenium(IV); vanadium(V); phosphate; silica Introduction Arsenic (As) is well known as a useful compound in industrial applications such as smelting, agricultural pesticides and insecticides (LANL, 2004). However, As has also been considered as a strong poisonous chemical due to its odorless and nearly tasteless nature (Buchanan, 1962; Ferguson and Gavis, 1972). Even small amounts of arsenic in drinking water can have adverse effects on human health. Known consequences include cardiovas- cular diseases, conjunctivitis, and skin cancer (Tseng et al., 1968; Klaassen, 1996; Zhang et al., 2004; Safiullah et al., 2004; Yean et al., 2005; Zhang and Stanforth, 2005). Of organic and inorganic arsenic, inorganic arsenic commonly exists in two valence states, As(III) and As(V), in groundwater or surface water (Ferguson and Gavis, 1972; Reynolds et al., 1999). Inorganic arsenic also has adverse effects on human health. As(III) effects on human health are more adverse than those of As(V); however, it is easy to transform As(III) easily to As(V) in oxygenated environments (Brookins, 1988). In addition, the efficiency of removal of As(V) by mineral oxides is found to be greater than that of As(III). Therefore, the preoxidation of As(III) to As(V) by using oxidizing agents including oxygen and ozone, prior to adsorption is recommended (Oscarson et al., 1983; Frank and Clifford, 1986). Due to the serious effects of arsenic on people’s health, *Corresponding author. E-mail: mfan@iastate.edu. World Health Organization (WHO) recommended 10 μg/L as the guideline value for arsenic in drinking water in 2001 (WHO, 2001) and the U.S. Environmental Protec- tion Agency (USEPA) also promulgated 10 μg/L as its new arsenic standard for drinking water (USEPA, 2001a). Therefore, development of various arsenic removal tech- nologies is important. Metal oxides have been studied by many researchers as one of the most promising arsenic removal technologies. These materials include amorphous ferric hydroxide (Pierce and Moore, 1982), granular fer- ric hydroxide (GFH) (Thirunavukkarasu et al., 2003), amorphous aluminum oxide (Anderson et al., 1976), and activated alumina (Rosenblum and Clifford, 1983). Our previous research has shown that Fe 2 O 3 and Al 2 O 3 are good adsorption media (Jeong et al., 2005) for As(V) without the presence of competing solutes. It was observed that their arsenate adsorption capacities varied with the pH values of As(V) solutions, and the highest adsorption of As(V) on both Fe 2 O 3 and Al 2 O 3 was observed at pH 6. However, some soluble solutes in water are often present in groundwater and surface water (Meng et al., 2002; Roberts et al., 2004; Hug et al., 2005). Welch et al. (1998) reported that the phosphate (as P) in the shal- low groundwater from the southern Carson Desert in the United States is higher than 4 mg/L. Many studies have indicated that the competing solutes affect the removal of As(V) by adsorbents. The presence of phosphate resulted in a severe reduction in arsenate adsorption by ferrihy-