On the electrostatic interactions in the transfer mechanisms of iron during nanofiltration in high concentrated phosphoric acid. - Université de Rennes Accéder directement au contenu
Article Dans Une Revue Journal of Membrane Science Année : 2013

On the electrostatic interactions in the transfer mechanisms of iron during nanofiltration in high concentrated phosphoric acid.

Résumé

Concd. phosphoric acid issued from the "wet process" contains at least 19 different contaminants, among which are metal elements, that must be removed to obtain purified acid valuable in many applications. Nanofiltration of concd. inorg. acids is an emerging application for NF that could be used for purifn. of raw phosphoric acid. Nevertheless, an in-depth study of transfer mechanisms is required in order to properly understand the obsd. retentions of metal species during NF of raw phosphoric acid and to be able to propose a better management of the process for further purifn. NF mechanisms concerning metal ions in dild. aq. solns. are extensively studied, but up to now limited literature data deal with concd. acids. This paper is a contribution to a better understanding of transfer of low amt. of metal species in concd. phosphoric acid, the concn. of which can be as high as 5.9 mol L-1. The study focuses on the transfer of iron that is the main metal contaminant of the raw acid. To achieve this goal, model solns. without and with iron chloride (18.6×10-3 mol L-1 FeCl3) in H3PO4 (0.12-1.2-5.9 mol L-1) are filtered in a stirred dead-end cell using a MPF34 membrane. Retentions of phosphoric acid, that can be in neutral (H3PO4) and charged (H2PO4-) form, is discussed. Dealing with iron-phosphate chelates, Fe(H2PO4)4- is the predominant one whereas two cations can sometimes exist: Fe(HPO4)+ and Fe(H2PO4)2+. The divalent cation is in significant amt. only in 0.12 mol L-1 acid concn. medium. Retentions of iron chelates by the NF membrane are detd. from both the mass balance of iron and their dissocn. consts. For 5.9 and 1.2 mol L-1 media, retentions decrease in the following order: Fe(H2PO4)4-\textgreaterH3PO4\textgreaterH2PO4-\textgreaterH+.Cl-. At high acid concn., chloride retention is neg. suggesting that electrostatic interactions can be involved in transfer mechanism at both 5.9 and 1.2 mol L-1. [on SciFinder(R)]

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Dates et versions

hal-01069943 , version 1 (30-09-2014)

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Houda Diallo, Murielle Rabiller-Baudry, Khaoula Khaless, Bernard Chaufer. On the electrostatic interactions in the transfer mechanisms of iron during nanofiltration in high concentrated phosphoric acid.. Journal of Membrane Science, 2013, 427, pp.37--47. ⟨10.1016/j.memsci.2012.08.047⟩. ⟨hal-01069943⟩
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