Acid Dissolution Kinetics of Synthetic Aluminum-Substituted Maghemites (γ-Fe2-xAlxO3)
- Marcelo A. Batista *a,
- Antonio C. S. da Costaa,
- Jerry M. Bighamb,
- Ivan G. Souza Juniorc and
- Franklin S. Jonesd
- a Univ. Estadual de Maringá UEM Dep. de Agronomia DAG, 87020-900 Maringá, PR, Brazil
b The Ohio State Univ. School of Environ. and Natural Resour. SENR 2021 Coffey Rd. Columbus, OH 43210-1085
c Univ. Estadual de Maringá UEM Dep. de Agronomia DAG, 87020-900 Maringá, PR, Brazil
d The Ohio State Univ. School of Environ. and Natural Resour. SENR 2021 Coffey Rd. Columbus, OH 43210-1085
The isomorphic substitution (IS) of Al for Fe can alter many properties of Fe oxide minerals, including their aqueous solubility. The resistance of these minerals to dissolution in soils can, in turn, influence the availability of Fe and the formation of new Fe oxides. In this study, the dissolution kinetics of synthetic, Al-substituted maghemites (γ-Fe2−xAlxO3) were investigated in 2 M HCl. The IS values varied from 0.0 to 14.3 mol% Al, and the dissolution reaction was conducted under controlled temperature (20°C ± 1) over a period of 288 h. Successive, 5-mL aliquots of suspension were withdrawn after set times, and Fe and Al were analyzed by ICP–MS. The overall dissolution rates of Fe and Al were similar throughout the experiment, indicating congruent dissolution. The resulting data were described equally well by using the Kabai and Avrami-Erofejev equations. Dissolution rates considering the specific surface area (SSA), as k2 = k/SSA, were the most efficient for describing the influence of IS on mineral dissolution and demonstrated that the maghemites became more resistant to dissolution with increasing Al substitution. Observations from transmission electron microscopy (TEM) supported isotropic dissolution of individual particles.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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