Effect of processing time on removal of harmful emerging salt pollutants from saline-sodic soil during electrochemical remediation

Abstract

The recent climate change has spawned a new emerging environmental hazard known as soil salinity. The lacks of rainfall and global warming have drastically increased the concentration of harmful emergent salt pollutants (HESPs) to toxic levels for natural and human assets. Electrochemical remediation (ECR) has been successfully used in remediation of contaminated soils. This research aims to investigate the effect of processing time (PT) on the removal of HESPs during ECR. The experiments were operated in a designed laboratory cell, using two different PT of 3 and 5 days with a voltage gradient of 1.5 V/cm. The results show that the increase of PT enhances the removal of monovalent cations, including sodium (Na⁺) and potassium (K⁺), reaching an efficiency of 63 and 83%, respectively. However, calcium (Ca²⁺) and magnesium (Mg²⁺) have exhibited irreversible behavior, where the increase of PT seems hindering their removal, namely near the cathode. Longer periods induce sharp increase in the basic front, which curb their desorption and mobilization. For the anionic salts, the raises of PT lead to better elimination of monovalent anions, with a removal of 92 and 63% for nitrate (NO₃^-) and chloride (Cl^-), respectively. Nevertheless, the effect of PT was less significant on the elimination of sulfate (SO₄^2-), due to their chemical nature. It can be concluded that the removal rate is an intrinsic parameter, strongly related to set of parameters, including the soil pH, chemical nature, ionic valence of the targeted salts and their selectivity on clay particles in clay-water-electrolyte system.

Keywords: Electrochemical; Emerging salt pollutants; Processing time; Remediation; Removal; Saline-sodic soil.