CaCl2-in-mesoporous silica grown on superabsorbent polymer to enhance water uptake

Abstract

Super absorbent polymer (SAP) sorbs copious amount of liquid water but its sorption power for water vapor is quite low. On the other hand, mesoporous silica loaded with CaCl2 (MPS-CC) has high sorption capacity for water vapor. However, this is determined by the salt loading, which is limited due to its corrosiveness. Even by simple powder blending of 75 mass% of SAP and the balance of MPS-CC (SAP75/MPS-CC25), the 3-hour maximum specific water uptake (g H2O/g sorbent) reached the maximum, 3 times the equilibrium uptake of MPS-CC. The sorption property was further enhanced by developing a new sorbent in which mesoporous silica was grown on the surface of swelling SAP and then impregnated by CC in ethanol. In the new sorbent (SAP-iMPS-CC), MPS grew organized, straight and lengthwise by the help of SAP. Owing to such intimate contact between MPS and SAP, the 3-hour specific water uptake of the new sorbents grown for more than 24 h (SAP-iMPS-CC24) was kept constant at the value of 2 times that of SAP75/MPS25. The SAP mass% of SAP-iMPS-144 could reach 25 without the sacrifice of sorption capacity.