HYGROSCOPIC PROPERTIES AND WATER-VAPOUR SORPTION KINETICS OF GRANULATED FERTILIZER-AMELIORANTS BASED ON PHOSPHOGYPSUM AND MECHANOCHEMICALLY ACTIVATED PHOSPHORITE
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Ospanov T.A., Reymov A.M., Erkaev A.U., Kurbaniyazov R.K.
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The storage stability of granulated mineral fertilizers is governed by their ability to sorb atmospheric moisture, yet for multicomponent systems based on industrial waste this relationship remains poorly quantified. The aim of the work was to determine the hygroscopic point and the sorption behaviour of four fertilizer-ameliorant compositions prepared from phosphogypsum, Central Kyzylkum phosphorite mechanochemically activated with ammonium sulphate at a mass ratio of 80 : 20, Kyrantau glauconite and organic components. The isopiestic (desiccator) method of N.E. Pestov was applied: samples of the 2–4 mm fraction were held for 30 days at 25 ± 0.5 °C in environments of 40–100 % relative humidity maintained by saturated salt solutions. The hygroscopic points fell within 69–78 % RH and the 30-day moisture uptake within 2.4–4.2 %. The sorption isotherms proved to be S-shaped curves of type II in the BET classification, comprising monomolecular adsorption, capillary condensation and deliquescence stages. Hygroscopicity was shown to be governed by the proportion of soluble ionic components and by the density of hydrophilic functional groups in the organic phase. For the pilot-scale product the hygroscopic point was 74–78 % RH, and after 30 days of storage both the particle-size distribution and the mechanical strength remained within the applicable agrotechnical requirements. The results provide a quantitative basis for specifying packaging and warehouse humidity limits for this class of products.
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Authors
Ospanov T.A., Reymov A.M., Erkaev A.U., Kurbaniyazov R.K.
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References:
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