Adsorption of Arsenite and Arsenate in Variable Charge Soils of New Zealand Mahimairaja S1,*, Bolan N.S.2 1Dept. of Environmental Science, Tamil Nadu Agricultural University, Coimbatore – 641003, India 2Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095, Australia *Corresponding author: E Mail: rajasmahimai@yahoo.co.in
Online published on 11 June, 2014. Abstract The chemical species and their physico-chemical reactions in soils determine the chemistry and biotoxicity of arsenic (As) in soils. Therefore, in the current study, the adsorption of arsenite - As(III), and arsenate – As(V) in selected soils of New Zealand that differ in their charge components was examined. The adsorption kinetics showed that irrespective of soil types, the adsorption of As(III) continued upto 48 hrs, although more than 90% occurred within 24 hrs. In contrast, the adsorption of As(V) was initially rapid (> 80% within 30 min) and continued afterwards at a slow rate upto 48 hrs. The results of batch experiments have shown that the sorption data for both As(III) and As(V) were adequately described by the Freundlich equation. Marked differences were observed among the soils. In general, soils with allophonic clay mineral and high CEC adsorbed more As than soils with mica/illite minerals and low CEC. The phosphate addition markedly reduced [20 to 43% in As(III); 13 to 54% in As(V)] the adsorption, particularly at lower concentration of As. Top Keywords Arsenite, arsenate, adsorption, isotherms, bioavailability, cation exchange capacity. Top |