Removal of Chromium from a Contaminated Soil Using Oxalic Acid, Citric Acid, and Hydrochloric Acid: Dynamics, Mechanisms, and Concomitant Removal of Non-Targeted Metals

Abstract

Soil leaching is an effective remediation technique using agents to leach the target pollutants from the soil. However, the dynamics and mechanisms for leaching of Cr and other non-pollutant metals from Cr-contaminated soils are not yet well understood. Here, column leaching experiments were conducted to determine the effect of hydrochloric acid (HCl), citric acid (CA), and oxalic acid (OX) on the leaching of Cr, as well as of Ca, Mg, Fe, and Mn, from a soil contaminated by a Cr slag heap. Acid leaching decreased soil pH and enhanced the mobility of all the surveyed metals. Leaching dynamics varied with both metals and acids. OX had the highest removal rates for Cr, Fe, Mn, and Mg, but had the poorest ability to leach Ca. HCl leached the largest amount of Ca, while CA leached similar amounts of Mg and Mn to OX, and similar amounts of Fe and Cr to HCl. Cr in the leachates was correlated with Ca, Mg, Fe, and Mn. Cr mainly interacted with soil mineral components and showed a punctate distribution in soil particles. The X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) analyses showed soil mineralogical and morphological properties were differently altered after leaching by different acids. Complexation of Cr(III), competitive desorption, and reduction of Cr(VI) make significant contribution to Cr leaching by organic acids. In conclusion, OX can be applied in leaching remediation of Cr-contaminated soil, but the concomitant removal of other non-targeted metals should be taken into account because of the loss of soil minerals and fertility.

Remediation of Cr(VI)-Contaminated Soil by Nano-Zero-Valent Iron in Combination with Biochar or Humic Acid and the Consequences for Plant Performance

“…E). The detailed characteristics of the two kinds of soil samples were described in our previous studies [7,36]. The soils were first air-dried, then sieved (2 mm).…”

Isolation and Identification of Chromium Reducing Bacillus Cereus Species from Chromium-Contaminated Soil for the Biological Detoxification of Chromium

“…By comparing the experimental data, the bacteria isolated in this study demonstrated a higher chromium reduction efficiency, not only in the initial chromium reduction concentration but also in the chromium reduction time. Furthermore, the leaching method has been mostly used as a strategy for the in situ treatment of polluted soils [53][54][55][56], where the chromate in the soil was continuously eluted by the eluent, typically using the bacteria as the eluent. For example, previous reports demonstrated the use of the bacteria Acidithiobacillus ferrooxidans as the eluent to elute chromium from soil; however, this took as long as 5 weeks [57].…”

Fuzzy Coordination Control Strategy and Thermohydraulic Dynamics Modeling of a Natural Gas Heating System for In Situ Soil Thermal Remediation

“…(4) There is no chemical interaction, and the gas is assumed to be ideal gas. (5) It is assumed that the solid, liquid, and gas phases are continuous in unsaturated soil, separately. (6) It is assumed that the migration of liquid and gas do not affect each other.…”

“…A cornucopia of remediation technologies has been developed to treat contaminated soils [5][6][7][8]. Among these technologies, in situ soil thermal remediation holds an important niche role due to its ability to clean pollutants quickly and reliably [9].…”