Effects of Oxalate and Humic Acid on Arsenate Sorption by and Desorption from a Chinese Red Soil

Abstract

Abstract. Studies on arsenate (As(V)) sorption and desorption have been mainly limited to soil minerals and sorption and desorption reactions in whole soils are poorly understood. In this study the sorption of As(V) by and phosphate-induced desorption from a Chinese red soil were studied in the presence of oxalate and humic acid (HA). Arsenate was strongly sorbed mainly through ligand exchange reactions on the soil. Arsenate sorption decreased in the presence of oxalate or HA. Oxalate and HA influenced As(V) sorption mainly by competing for sorption sites and reducing sorption sites, and oxalate could also decrease sorption through dissolving clay minerals. Oxalate and HA could also facilitate As(V) desorption from the soil. Both sorption and desorption kinetics were two stage processes. Sorption kinetics conducted from 0.2-840 h showed that As(V) sorption increased with increasing residence time. Sorption equilibrium was retarded and the maximum sorption decreased in the presence of oxalate or HA. Phosphate-induced desorption kinetics conducted on the soil with 24 h and 840 h of sorption equilibrium time showed a significant effect of equilibrium time on As(V) desorption. The presence of oxalate or HA during the sorption process resulted in more As(V) desorption. Due to the degradation of oxalate, soil treated with oxalate and with a sorption equilibrium time of 840 h showed no significant difference in desorption kinetics from untreated soil.

In situ oxalic acid injection to accelerate arsenic remediation at a superfund site in New Jersey

“…[19, 20] Studies suggest that dissolution of Al and Fe species by organic acids leads to As release or that there is competitive sorption between organic acids and As (or a combination of the two processes play a role). [8, 21–23] Oxalic acid is often included in sequential soil extraction schemes investigating As phases. [24–27] Additionally, studies have shown As release in the presence of oxalic acid [7, 8, 22, 28, 29] and inhibition of As sorption in the presence of oxalic acid under certain conditions.…”

Individual and combined influence of calcium and anions on simultaneous removal of chromate and arsenate by Fe(II) under suboxic conditions

“…Some other researchers also reported that HA, oxalate and salicylic acid could form soluble complexes with Fe and Al to dissolve clay minerals and adsorption was reduced accordingly [41,42].…”

Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

“…Further, previous studies [10,20,21,22] have also reported the higher adsorption affinity of HA molecules for iron oxide than As species, which tends to change the surface properties of sorbent and compete with As species for active sorption sites, in turn increasing the mobility of As in water. The presence of HA also impedes the precipitation of ferric hydroxide at lower coagulant dosage due to the formation of soluble complexes with Fe 3+ during the C/F/S process [23,24,25]. A recent study [17] exploring the complexation behavior of As with HA and FA in water found results indicating the increased binding affinity of organic ligands with As(V) as compared to with As(III).…”