Pilot-scale ex situ electrokinetic restoration of saline greenhouse soil

Abstract

This study was conducted to investigate the feasibility of using an ex situ electrokinetic system for the restoration of saline greenhouse soil. An experiment was conducted in a pilot-scale reactor (1 × 1 × 0.25 m) during 14 days. Chloride accumulated in the top layer through pore-water evaporation. There was no removal of the nitrate in the top layer because of the continuous upward transport of nitrate accompanying the evaporation of soil moisture. However, the removal of sulfate was uniform across all the layers. In the case of cations, a significant amount (64.4%) of potassium was removed, and there was no removal of the magnesium in the top layer. The electrokinetic treatment changed the speciation of calcium in the soil, resulting in an increase in the amount of exchangeable calcium. Furthermore, nitrate was transported toward the anode and reduced to nitrogen gas as the result of an electrochemical reaction at the surface of the anode. Sulfate formed a very stable and insoluble precipitate with calcium—calcium sulfate (gypsum). Ex situ electrokinetic system removed salts from nitrate and sulfate-accumulated saline soil. However, the overall removal efficiency was not high enough because of relatively short operation time.