Browsing by Author "Paddon, Brian D A"

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    The manufacture of monosodium phosphate from wet process acid by amine extraction
    (1974) Price, Roger Nelson Davey; De Kock, J W; Paddon, Brian D A
    Monosodium phosphate (NaH₂PO₄) may be prepared from a mixture of phosphoric acid and sodium chloride on the principle that an amine in organic solution can extract the elements of hydrochloric acid (HCl). This is possible because amines are more selective for hydrochloric than for phosphoric acid. If wet process phosphoric acid is used, the impurities must be separated in some way from the final product. The work described here involves a study of the distribution of phosphoric acid itself, and the impurities trivalent iron and sulphate, between aqueous solutions and kerosene solut ions of the commercial amine Amberlite LA-1. In a countercurrent extraction process, approximately twenty theoretical stages would be needed to reduce the iron concentration to the food grade level. Sulphate is held in the organic phase. Monosodium phosphate can be recovered by stripping the organic phase with a sodium chloride solution. An attempt was made to explain the extraction of phosphoric and sulphuric acids from a mixture. It was found that amine extraction followed a pattern similar to that of gas adsorption, and a modified BET equation gave a fair but not highly accurate fit of the distribution data.
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    The recovery of potassium from seawater and brines using dipicrylamine
    (1985) Venn, John Garrett; Paddon, Brian D A
    This thesis gives a literature survey of the physical and chemical properties of dipicrylamine (2,4,6,2',4',6' hexanitrodiphenylamine), its synthesis and analysis, and its use in a process for the recovery of potassium from seawater and brines. Where data is not available in the literature it is obtained by experiment. The published and experimental data are used for the design of a process using dipicrylamine for the recovery of potassium and an analysis of its economic viability. Four process steps are identified and examined. These are (i) the precipitation of the potassium salt of dipicrylamine (KDPA) from seawater or brines, (ii) the recovery of dipicrylamine from the spent seawater or brine, (iii) the conversion of KDPA to produce a potassium salt and the insoluble hydrogen form of dipicrylamine (HDPA) by reaction with an acid and (iv) the conversion of HDPA to a soluble form for recycling and reuse. It is concluded that the recovery of potassium from seawater and brines is technically viable. While the brine process is economically viable at present, the large flowrates found in process step (ii) limit the viability of the seawater process.