Vadose Zone Soil Moisture Wicking Using Super‐Absorbent Polymers

Abstract

Super‐absorbent polymers (SAPs) have the potential to remove water and associated contaminants from unsaturated sediments. Laboratory experiments were conducted to test four types of SAPs. Column experiments, with a layer of polymer on top of unsaturated porous media, showed the ability of the SAPs to extract up to 80% of initial water during periods up to 4 wk. In column experiments where the sorbent was emplaced between layers of unsaturated porous media, gel formation was observed at both the sorbent–porous medium interfaces. The extraction percentages were similar for both configurations and no obvious differences were observed for the four SAPs. Two flow cells were used to test the wicking behavior in two dimensions using three configurations. The largest removal percentages occurred for the horizontal sorbent layer configuration, which had the largest interfacial area. In a larger flow cell, a woven nylon “sock” was packed with sorbent and placed between perforated metal plates, mimicking a well configuration. After 1 wk of contact time, the sock was removed and replaced by a fresh sock. The results showed that the sorbent was able to continuously extract water from the porous media, although the rate decreased with time. The declining yield was associated with the sharp reduction in water saturation and relative permeability near the sorbent. The capillary pressure continued to increase during the total contact time, indicating that the sorbent remained active during that period. This work has demonstrated the potential of soil moisture wicking using SAPs at the proof‐of‐principle level.