Acetone and ethanol solvents are causing frequent interaction between the beads(not giving any protection to prevent agglomeration). The water or moisture and pore volume present in that beads are also completely removed or occupied might cause the collapse of the beads. there might be another chance that interaction of this solvents with the beads might be stronger compared to the aq ones which may disturn the actual structure of the indivudal calcium alginate molecules which might finaly giving this result.