Moisture content-affected electrokinetic remediation of Cr(VI)-contaminated clay by a hydrocalumite barrier

Abstract

An electrokinetic-permeable reaction barrier (EK-PRB) system was introduced in this study with hydrocalumite as the barrier material. The combined system effectively remediated the Cr(VI)-contaminated clay after a 72-h treatment, and the Cr(VI) removal efficiency increased with the initial soil moisture content. Further evidence was found that the changing soil pH value and current density were highly associated with the initial moisture content, showing its important roles in the Cr(VI) removal process. Additionally, the total Cr removal efficiency was much lower than that of Cr(VI) owing to the partial conversion of Cr(VI) to Cr(III) in the electrokinetic remediation process. Under high soil moisture conditions (40%), the removal efficiency of Cr(VI) and total Cr was 96.6 and 67.3%, respectively. Further analysis also revealed the new mineral phase, chromate hydrocalumite, for Cr fixation in the hydrocalumite barrier, which was significantly affected by the initial soil moisture content. Our results showed that the EK-PRB system with a hydrocalumite barrier is highly promising with great potential for the effective remediation of Cr(VI)-contaminated clay and engineering implementation.

Medium-scale ex suit electrokinetic remediation of Cd and Zn polluted soil enhanced by EDTA, tartaric acid, citric acid and acetic acid

“…7-8 indicated the quantity of metals extracted in each step of the sequential extraction analysis. As we know, the EK process alters heavy metals speciation in soils and the process is strongly influenced by pH and redox potential [4,23]. F1 and F2 fractions of Cd and Zn were extremely high in the middle section soils for the enhanced EK remediation and slightly high in the middle section soils for the control test.…”

Remediation of As/Cr co-contaminated soil by electrokinetic coupled with permeable reactive barrier

“…In this experiment, the plate-shaped graphite electrodes were directly inserted into the wet soil. Soil moisture contents of all tests were 30% according previous report [21]. The removal efficiency of TCr and TAs by different PRB insertion sites (A, A + B, A + C), voltage gradients (1, 1.5 and 2 V/cm), running time (24, 48, 72, 96 and 120 h) and different PRB materials (CaAl-LDH and CaFe-LDH) were investigated.…”

“…Sajadadhami et al [19] used electrokinetic method combined with Fenton technology to remove 93% of phenanthrene in the soil, and the removal efficiency was 100% higher than that of traditional electrokinetic method. Among the above combined technologies, the technology combining EK and PRB can improve the removal efficiency of pollutants and the performance of EK by accelerating the transport of pollutants, thus reducing manpower and material inputs [20][21][22][23].…”

“…However, ZVI is easily affected by pH, ion composition and other factors, which will lead to PRB precipitation in the degradation process, thus reducing its permeability, reactivity and durability [19,28]. Layered double hydroxides (LDHs) is an increasing concern due to their low cost and long-term operability as PRB materials [21,30]. Meanwhile, recent studies have found that LDHs also has the ability to remove oxyanion contaminants.…”

“…However, most of the surveys were carried out on soils contaminated with single metals. The previous work of our group [14,21] only explored the remediation of single metal (Cr) contaminated soil by EK-PRB technology in detail. Cappai et al [26] enhanced the removal of Cr and As by transforming red mud (TRM) into an active material for PRB, and evaluated the synergic interaction between the EK and the PRB system.…”