Insolubilization of Water-Soluble Sodium Alginate by Ionic Crosslinking and Redissolution Thereof in Aqueous Salt Solutions
Vol. 58, No. 2, pp. 80-86,
Apr. 2021
10.12772/TSE.2021.58.080
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Abstract
In this work, the insolubilization of water-soluble sodium alginate, which is a representative
biomass natural polymer, was investigated for various purposes, including coatings
on paper cups. It was observed that sodium alginate could be insolubilized well in
calcium chloride by formation of ionic crosslinks through replacement of Na+ ions with
Ca2+ ions on a block of L-guluronic acid of alginate to form calcium alginate. Water-insolubilization
of alginate is a critical prerequisite for the coatings on cups to retain water. However,
the calcium alginate coating needs to undergo re-dissolution in water to enable
recycling of the paper cups after use. It was observed that calcium alginate could be easily
re-dissolved in a specific aqueous salt solution containing disodium phosphate (Na2HPO4).
The re-dissolution of calcium alginate was confirmed by scanning electron microscopy and
energy-dispersive X-ray spectroscopy (EDS). The process developed in this study is
expected to be used for various eco-friendly applications without the need to use organic
solvents.
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