Abstract:

The effects of different conditions, including chloride salt solution concentration, cyclic water absorption-drying, and evaporation on the long-term water absorption-release performance and water retention of Super Absorbent Polymer (SAP) were investigated, to provide a basis for the evaluation of the applicability of SAP in saline environments. Using four polyacrylic SAPs (18, 60, 120 and 200 mesh), we conducted standard water absorption test, six cycles of drying-rehydration tests, and the water retention tests under different evaporation conditions to evaluate their water absorption-release capacity, salt tolerance and water retention. The results showed that as chloride salt solution concentration increased, the water absorption ratio of all SAPs decreased. In deionized water, the 60-mesh SAP exhibited the highest absorption ratio (602.0 g/g), but its salt tolerance was poor, at 2000 mg/L salt concentration, absorption dropped to 112.7 g/g (a reduction of 81.3%). The water absorption ratio of 120-200 mesh SAPs was only 53%-66.8% of the 60 mesh SAP in deionized water, but their salt tolerance was superior, indicating a negative correlation between particle size and salt tolerance. After six drying-rehydration cycles, the 60 mesh SAP still retained 90.1% of its initial absorption capacity, while the 200 mesh SAP showed the poorest durability, only 55.7%. Under 60°C constant temperature and natural evaporation (indoor/outdoor), water retention declined linearly. No significant relationship was observed between water retention and salt concentration, nor were there significant differences among the four SAPs.The comprehensive analysis suggested that 18-60 mesh SAPs were more suitable for environments with salt solution concentrations ≤450mg/L, while 120-200 mesh SAPs perform better at 450-2000 mg/L. The 60 mesh SAP had the best comprehensive performance, balancing high water absorption and retention stability. These findings provided practical data support for the feasibility of SAPs in saline-alkali soil remediation.

Key words: super absorbent polymer (SAP), salt ion concentration, durability, salinity tolerance, water absorption-release performance, water retention capacity