Effects of soil properties on water absorption of super absorbent polymers

The water absorption ratio of four super absorbent polymers(SAP) mixed with four different kinds of soil which are sand loamy soil, loamy sand soil, sand clay soil 1 and sand clay soil 2, were tested. Effects of soil properties on water absorption of the SAP, were analyzed. The soils that mixed with SAP were dry and the proportion of SAP to soil was 0.5%. Results show that water absorption ratio of SAP decreases remarkably compared with controls(SAP soaked in TAP water without soils). The decrease trend increase with time for water absorption. The water absorption ratio of four kinds of SAP decreases by 14.4%～58.0% in 10 minutes and by 41.8%～90.2% in 70 minutes. At the beginning of absorption in the soils, the water absorption ratio of SAP is restricted by the soil porosity and is affected gradually by ions in solution as absorption time increase because solvent ions in soils is increased. The quantity of solvent soil ions is related to the clay percent. The higher clay percent the soil contains, the more solvent ions exist in the solution. Conversely the lower clay percent the soil has, the less solvent ions present in solution, the water absorption ratio is lower in the soil that its clay percent is higher than in the soil which its clay percent is lower. Soil properties not only reduce water absorption ratio of SAP, but also change the regulation of water absorption of SAP. For the controls, water absorption ratio increases with the increase of water absorption time and then remains unchanged while the water absorption ratio decreases with the increase of absorption time after 10 minutes absorption for the treatments which SAP are mixed with soils.