Effect of aluminum sulfate, Al
2(SO
4)
3, on dispersion state of sodium carboxymethylcellulose, NaCMC, in aqueous solution was investigated by rheological measurements and X-ray photoelectron spectroscopy (XPS). Rheological properties of NaCMC aqueous solutions containing Al
2(SO
4)
3 were investigated using a cone-plate type rheometer. When NaCMC concentration was 0.5 wt %, shear stress of the solution slightly decreased with increasing concentration of Al
2(SO
4)
3. On the other hand, when NaCMC concentration was 5 wt %, the shear stress increased with increasing Al
2(SO
4)
3 concentration. In this case, both dynamic storage and loss moduli also increased. These results suggest that the addition of Al
2(SO
4)
3 increased crosslinking density and caused heterogeneous aggregation of NaCMC. This was confirmed by the fact that diluted Al
2(SO
4)
3-containing NaCMC solution was separated to microgel-like particle and homogeneous solution. XPS revealed that aluminum ion was concentrated in the microgel-like particle. From these results, dispersion state of NaCMC in aqueous solution containing Al
2(SO
4)
3 was modeled as microgel-like particle containing concentrated aluminum ions are suspended in the network of NaCMC chains.
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