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A study of a cyclic amine leach-carbonate precipitation process for lead sulfate

Aziz, Muhammed Abdul (1985) A study of a cyclic amine leach-carbonate precipitation process for lead sulfate. Masters by Research thesis, Murdoch University.

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Abstract

The leaching of lead sulfate in aqueous diethylenetriarnine (dien) is pH dependent with a maximum leaching capacity at pH 11.6. Chloride and nitrate ions suppress the leaching of lead by dien; however, addition of sulfate ion does not diminish the leaching capacity of aqueous dien for lead sulfate. Indeed, addition of sulfate ion significantly increases the solubility of lead chloride and nitrate in aqueous dien. The presence of carbonate ions in the leachant (dien) converts lead sulfate into insoluble lead compounds plumbonacrite, leadhillite and lanarkite, and thus preventing further leaching by dien.

Depending on the precipitant, lead is precipitated as hydrocerussite, cerussite or NaOH.2PbCO2, but not as lead dihydroxycarbonate, Pb(OH)2.PbCO2 .

The major cause of deactivation of recycled dien appears to be protonation of dien during the precipitation of lead using carbon dioxide. pH adjustment using sodium hydroxide restores the leaching capacity of the dien solution. Alternatively, sodium carbonate can be used as precipitant, and a procedure for the precipitation of lead using sodium carbonate is suggested to overcome the undesired protonation of dien.

The kinetics of precipitation of lead carbonates was studied and it was shown that dissolution of carbon dioxide in aqueous dien, followed by addition to a solution of lead ions, leads to slow precipitation. The slowness was attributed to the slow, reversible formation of carbamate by reaction of carbon dioxide with dien. Direct passing of carbon dioxide into a lead dien sulfate solution gives a precipitation rate greater than for the addition of carbon dioxide solution but less than for the In addition of sodium carbonate solution.

Crystalline lead diethylenetriarnine sulfate and lead diethylenetriamine nitrate have been synthesised and physical properties recorded. The X-ray diffractogram of lead diethylenetriamine sulfate is presented.

A simple gas volumetric apparatus has been designed for rapid determination of total carbonate and bicarbonate in a wide range of solids and solutions. The apparatus has been tested to determine 0.12 1 mmol (7 - 6 0 mg) CO2^2- , and reproducible results have been obtained.

The use of sodium chloride as a potentiornetric breaking reagent has been found to compare favourably with sodium iodide in the titration of dien.

Direct titration of lead by ethylenediaminetetraacetic acid following dissolution of lead sulfate in aqueous dien was found to provide a simple and accurate analysis for lead in the presence of sulfate.

Item Type: Thesis (Masters by Research)
Murdoch Affiliation: School of Mathematical and Physical Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Giles, Dion
URI: http://researchrepository.murdoch.edu.au/id/eprint/52724
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