For further demonstrating the flexibility and absorbance rate of the compressed cellulose aerogels (in Table 1b), we used a cellulose aerogel absorbing 7.4 times of its dry weight of water for 20 min in the first test. Normally, absorbed water can only be removed from superabsorbent polymers by drying. In contrast, water absorbed by the cellulose aerogel is removed easily by simply squeezing it (Fig. 3d). The mass measurements in Table 1 show that almost all of the absorbed water (99.8%) was removed from the compressed sample (mr = 0.998). The volume ofthe compressed sample is about
1/3 of that of the original sample. When the compressed sample was placed back into water (Fig. 3e), it recovered to almost its original shape within 30 s. The wet sample was removed from the water after 20 min only. There is some shrinkage of the wet sample (Fig. 3f) compared to the one in Fig. 3b, possibly due to partial collapse of pores within the aerogel during squeezing. The volume ratio of the wet sample after the second 20-min water absorption
test and the original dry sample is only 0.42. In the second test, the sample absorbed 3.8 times of its dry weight of water. Again, most of the absorbed water can be removed (mr = 0.998). The volume of the wet sample after the third 20-min water absorbance test is similar to that of the wet sample after the second test indicating no further shrinkage of the aerogel (Fig. 3g). The amount of absorbed water in the third test is almost the same as that in the second test.
A mr value of 0.999 for the third water absorption test again indicates that nearly all the absorbed water was eliminated simply by squeezing the aerogel. For practical applications, flexibility of the recycled cellulose aerogel is very important.