Uday Kumar Banala Normally alginate beads need stabilizing by moderately high calcium concentration (0.1 to 0.2 M). The beads are relatively stable under acidic conditions. Your conditions probably are against you, i.e. alkaline conditions and low calcium conc (1 mM).

alginate particles disintegrated in alkaline, but not in acidic, media

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Article Effects of pH on the Shape of Alginate Particles and Its Rel...

Alginate bead formation requires high calcium conc

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https://www.researchgate.net/post/CaCl2_concentration_and_hardening_time_affect_on_alginate_bead_strength

M. Y. Shukor Thank you very much.

I used 0.2 M calcium chloride for cross-linking and 1 mM is the carbonate-bicarbonate buffer concentration used for heavy metal sequestration.

will increase in calcium chloride concentration above 0.2 M for cross-linking can stabilize the beads in alkaline environments?

Uday Kumar Banala

At the application stage, the calcium conc is too low at 1 mM, maybe you can try to increase it to 10, 20 mM etc. metal absorption at alkaline conditions might be a problem because many metals have solubility issue at alklaine pH

Dear M. Y. Shukor Thanks for the valuable suggestion.

I will try with the high concentration of calcium chloride.

My current research interest is to sequester uranium from alkaline wastes (generated in alkaline leaching process). In alkaline conditions, uranyl ion will form stable and soluble complexes with carbonates such as mono-, di- and tri-nuclear uranyl carbonate, UO2CO3(aq), UO2(CO3)22- and UO2(CO3)34-.