Effect of organic matter on arsenic(V) and antimony(V) adsorption in soils

Abstract

The interaction of toxic oxyanions with organic matter can affect their stability and binding mechanisms in soils. The adsorption/desorption properties of arsenic (As V )/antimony (Sb V ) oxyanions were tested with two types of soil with a variable content of natural organic matter (NOM). Sample JEZ (I) represented a locality near a brown-coal power plant, and therefore formerly exposed to large amounts of atmospheric pollution, while sample LIZ (II) originated in an uncontaminated region without anthropogenic impact. Soil samples were investigated from the organic O and mineral B horizons. Different As/Sb fixations were indicated by their different adsorption affinity to O and B horizons. Arsenic as As V was strongly adsorbed in B horizons, while antimony as Sb V was predominantly bound in O horizons. The sorption followed the Langmuir model with maximum adsorption capacities of 1.4 × 10 −2 mmol g −1 for As and 1.0 × 10 −2 mmol g −1 for Sb adsorptions. The release of As and Sb to distilled water and 0.1 m KCl illustrated the significantly larger stability of As and Sb oxyanions in ionic solutions, where available ions prevented the aggregation of organic matter, thus maintaining the balanced distribution of surface charge. Distilled water with a pH of about 6 supported a negative surface charge density and enhanced the release of As/Sb oxyanions.

Highly efficient As(v)/Sb(v) removal by magnetic sludge composite: synthesis, characterization, equilibrium, and mechanism studies

“…3 Of the various species of As/Sb, As(V) and Sb(V) oxyanions are predominant and stable in oxic systems, possibly transforming to more toxic species under certain conditions, thereby presenting a more serious threat. 4 The World Health Organization (WHO) has set thresholds for safe drinking water of 10 mg L À1 (10 ppb) for As and 5 mg L À1 (5 ppb) for Sb. 5,6 Globally, and especially in South and Southeast Asia, tens of millions of people are at risk of exposure to these contaminants in groundwater.…”

Insight into the Adsorption Behaviors of Antimony onto Soils Using Multidisciplinary Characterization

“…As shown in Figure 3 , Sb (III) existed as neutral molecules such as Sb (OH) 3 , H 3 SbO 3 , or HSbO 2 in the pH range of 2–10.7 and existed as SbO + or Sb (OH) 2 + under strong acid conditions [ 45 ]. In a strong alkaline environment, it existed as SbO 2 − or Sb (OH) 4 − , and only as Sb 3+ under extremely acidic conditions.…”

Chemical Processes Affecting the Mobility of Heavy Metals and Metalloids in Soil Environments

“…Indeed, some anions may bond indirectly to organic groups through a bridging with hydrolytic species of Al and Fe held on humic substances forming ternary As complexes [15]. According to Sharma et al [16,17] and Mitsunobu et al [18], a similar mechanism with much greater affinity to organic matter could be expected with Sb [19].…”