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  • Articles  (2)
  • pilot plant process  (2)
  • 1995-1999  (2)
  • 1960-1964
  • 1
    ISSN: 1573-5176
    Keywords: alginate ; pilot plant process ; pre-extraction ; Macrocystis pyrifera ; acid treatment ; formalin treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the extraction of alginate from brown seaweeds, the acid pre-extraction treatment has been considered by many authors as an essential step because it makes the alginate more readily soluble in an alkaline solution. At pilot plant level, extractions were made (i) using formalin treatment prior to the acid pre-extraction treatment (ii) using different acid treatments so the calcium ions exchanged varied from 83% to 4%. The use of formalin treatment gave a product with less color. During the acid pre-extraction treatment, it was possible to reduce the calcium exchanged from 33.4% to almost zero with a maximum reduction in alginate yield of 7%. The degree of acid treatment was positively correlated to calcium exchanged and yield but negatively correlated with alginate viscosity. Using strong acid conditions the viscosity was 168 mPa s, while mild acid conditions produced an alginate with 623 mPa s. The direct extraction from calcium alginate to sodium alginate is possible because strong alkaline conditions were used, pH 10 at 80 °C for two hours and with a low water volume. The best pre-extraction treatment to obtain an alginate with high viscoity is to hydrate the alga with 0.1% formalin overnight, then wash the alga once with hydrochloric acid at pH 4 using a batch system with continuous agitation during 15 min.
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  • 2
    ISSN: 1573-5176
    Keywords: Alginate ; pilot plant process ; extraction ; Macrocystispyrifera ; filtration ; centrifugation ; flocculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of temperature (70, 80, 90 °C) and time (1–9 h) during the alkaline extraction step on alginate yield and quality were studied. The alginate yield increased with time and maximum yield was obtained after 3.5 h treatment, ranging from19.4% at 70 °C to 21.9% at 90 °C. The viscosity of the alginate produced was inversely correlated with the temperature and time. At70 °C the slope of the curve was almost zero(753 to 923 mPa s); at 90 °C the viscosity loss was 154 mPa s per hour during the first two hours, reducing from 523 to 86 mPa s after 5 h; 80 °C yielded values between those for 70 °C and90 °C. The best conditions for alkaline extraction were using pH 10 at 80 °C for two hours. The curves obtained gave useful information for controlling the viscosity of the alginate during production. It was found that viscosity of the paste formed during alkaline extraction (`process viscosity') was the best parameter to determine there action rate during extraction. Alginate yield increased during filtration time from 17.6% to 23.7%after 55 min at 70 °C. In this step the viscosity of the alginate obtained remained almost constant (522–610 mPa s), indicating no degradation of the products during filtration. The best dilution to filter the alginate extract was obtained at 45 mPa s. Diatomaceous earth (Celite) and expanded lava(Perlite) were tested as filter aids. Expanded lava was the best filter aid, using 1 kg per kilogram of alginate produced. Three methods were studied to separate the alkaline-insoluble residues after extraction: filtration, centrifugation, flocculation, and combinations of them. The best system found was filtration with flocculant in a rotary vacuum filter, with a knife advance of 0.1 mm every 3.5 seconds and drum rotation of 2 rpm, yielding an average filtration flow rate of 10.5 L min-1.
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