Adsorption of arsenic (V) and arsenic (III) onto different uncalcined and calcined aluminium hydroxide powder

I.N. Bhattacharyaa1,*, P.K. Gochhayata1, S. Paulb2 and P.K. Mitrab2

1 Regional Research Laboratory, Bhubaneswar, Orissa, India
2 Department of Metallurgy, Jadavpur University, Kolkata-700032, India

Accepted 10 September 2004


Fine (1.5m) and coarse (~100m) aluminium trihydroxide (ATH), gibbsitic in nature and low bulk density (0.3g/cm3) gel aluminium hydroxides (basic aluminium sulfate, BAS) were used as precursor material for obtaining various calcined products at different temperatures up to 1200oC. These calcined products were used for adsorption of As(III) and As (V) from aqueous media. As(III) and As(V) adsorptions were found effective for fine gibbsitic materials calcined at 350oC and for coarse gibbsite particles calcined at 400oC. Similarly low bulk density BAS calcined at different temperatures up to 900oC showed high adsorptibility for As(V) but As(III) separation was not effective. Gibbsite when heated between 350oC 400oC transformed to boehmite while low bulk density BAS remained amorphous up to 800oC and at 900oC it transformed to η-alumina. It was found that chi and kappa forms of transition aluminas formed by calcining gibbsite at 500oC and 1000oC respectively showed lower adsorption efficiencies than boehmite phase. The α-alumina obtained from different sources showed different adsorptibility for As(V) and As(III). Variation of temperature and pH showed dependency of adsorptribility on such parameters. It was found further that degree of dehydroxylation had effect on the adsorptibility. Total dehydroxylation such as in the case of α-alumina, had no or less activity. Surface area showed beneficial effect on adsorption. The crystalline phase, extent of dehydroxylation and desulfurisation, surface area, starting precursor etc., were found to have bearing on adsorption efficiency of a material. The As(III) adsorption showed major dependency on surface area but As(V) adsorption showed combined dependency on above parameters.

Keywords: Arsenic; Adsorption; η-alumina; Boehmite; Gibbsite; Transitional alumina; BET surface area

* Corresponding author
   E-mail : inbhattacharya@ rrlbhu.res.in