I would like to understand the changes on adding increasing concentrations of a calcium solution to an alginate solution and why there is a difference when you add the alginate solution to the calcium solution instead of the other way round. Many Thanks!
Both questions can be answered by taking into consideration the gel formation process, which is assumed to be controlled by the diffusion of the two components involved in it: sodium alginate and Ca2+ ions. In this regard, the fact that the metallic cation has a smaller size than the polymer molecules means that it is mainly the cation that diffuses between the alginate chains, binding to unoccupied binding sites on the polymer.
Thus, in capsules formation, once the cationic solution is dropped into the alginate solution, a capsular membrane forms instantaneously around the droplet, and this will grow from the flux direction of the Ca2+ ions. When the mass of the calcium ions contained within the core capsule is exhausted, the gelation process finishes.
On the contrary, when alginate is dropped into calcium clhoride solutions, gel beds (instead of capsules) are formed, as Ca2+ cations diffuses rapidly in alginate solution droplets binding to this polymer.
Both questions can be answered by taking into consideration the gel formation process, which is assumed to be controlled by the diffusion of the two components involved in it: sodium alginate and Ca2+ ions. In this regard, the fact that the metallic cation has a smaller size than the polymer molecules means that it is mainly the cation that diffuses between the alginate chains, binding to unoccupied binding sites on the polymer.
Thus, in capsules formation, once the cationic solution is dropped into the alginate solution, a capsular membrane forms instantaneously around the droplet, and this will grow from the flux direction of the Ca2+ ions. When the mass of the calcium ions contained within the core capsule is exhausted, the gelation process finishes.
On the contrary, when alginate is dropped into calcium clhoride solutions, gel beds (instead of capsules) are formed, as Ca2+ cations diffuses rapidly in alginate solution droplets binding to this polymer.
Many thanks Ana! Your answer was very helpful! Do you happen to know what the effects of adding increasing amount of calcium ions to the sodium alginate will have on the viscosity, loss and storage modulus of the alginate gels?
Hi Jayne you can see my paper regarding the reaction between Alginate and metal ions
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