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Membrane recovery of metal pollutants from waste waters of the fertilizers industry

Obiettivo

- Analysis of the viability of the membrane processes (non-dispersive solvent extraction, supported liquid membrane, emulsion liquid membrane, hybrid liquid membranes and ion exchange) for the reduction and recovery of Cd and U in the waste waters of the fertilisers industry, studying two different options: - reduction of the metallic content in the phosphoric acid (30% P205) - reduction of the metallic content in the waste waters;
- Study of the selective recovery of Cd and U in the presence of Cu, Pb, V and Zn;
- Selection of the best membrane technology and design of the integrated process for the recovery of metal pollutants from waste waters of the fertilisers' industry.
Results so far

- The most economic way to undertake the removal of heavy metals from waste waters in the fertilisers' industry consists on their removal from the raw phosphoric acid.
- For the removal of Cd using liquid membranes a literature search pointed to the selection of dithiophosphinic acids as selective extractants, namely CYANEX 301 and CYANEX 302. The stripping step could be conducted using high acidic media, specifically working with hydrochloric acid at high concentrations.
- The optimum conditions for the removal and recovery of Cd from synthetic samples of phosphoric acid have been established and the kinetic modelling and optimisation of the separation processes has been carried out.
- Working with industrial phosphoric acid (28% P205), it has been observed that copper is coextrated with cadmium, except in the SLM technology where a selective separation seems to be possible. In the former case the regeneration of the organic phase becomes extremely difficult limiting the application of the studied technologies (NDSX, ELM, and HLM). New processes including different extractants and different regeneration agents must be considered.
- SIX appears as the optimum technology for the recovery of U from industrial phosphoric acid, it has not been observed any interference of the other metals initially present in the acid.

Follow-up

The main activities until the conclusion of the project will deal with the following :

- The selection of new extractants that allow the removal of Cd from phosphoric acid with a negligible loss of efficiency;
- Kinetic modelling of the separation processes and estimation of design parameters;
- Design and comparison of the studied technologies for the removal of heavy metals, especially Cd, and U from industrial phosphoric acid. The work will conclude with the selection of the optimum technological alternative.
* The first ten months were dedicated to the study of the feasibility of Cd separation by simultaneous Non-Dispersive Extraction and Back-Extraction (NDSX), Supported liquid membrane (SLM), Emulsion Liquid Membrane (ELM), Hybrid Liquid Membrane (HLM) and Ion Exchange (SIX) working with samples simulating aqueous effluents and samples of phosphoric acid. The results were presented at the second progress meeting held in Izmir (Turkey) during 1-2 November 1995;
* Between November 1995 and May 1996 the work was concentrated on the optimisation of Cd removal from phosphoric acid by NDSX, ELM, SLM and HLM technologies using either synthetic and industrial acid and analysing at the same time the influence of the variables. The recovery of U in the industrial H3P04 was analysed with SIX. Results were presented at the third progress meeting held in London (UK) during 3-5 June 1996;
* During the next six months, the joint research is concentrated on the selective separation of Cd and Cu from industrial H3P04 (28% P205) using NDSX, ELM, SLM and HLM technologies and on the optimisation of U recovery by SIX. Results will be presented and compared at the fourth meeting, among 4-6 February 1997 in Jerusalem (Israel).

Argomento(i)

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Invito a presentare proposte

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Meccanismo di finanziamento

CSC - Cost-sharing contracts

Coordinatore

Universidad de Cantabria
Contributo UE
Nessun dato
Indirizzo
S/N,Avenida de los Castros
39005 Santander
Spagna

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Costo totale
Nessun dato

Partecipanti (4)