Enhanced electrokinetic remediation of fluorine-contaminated soil by applying an ammonia continuous circulation system

Aluminium sulfate synergistic electrokinetic separation of soluble components from phosphorus slag and simultaneous stabilization of fluoride

In this study, fluoride (F) was stabilized and soluble components, namely phosphate (P), K, Ca, Cr, Mn, and Pb, were extracted from phosphorus slag (PS) by using aluminum sulfate (AS) synergistic electrokinetic. PHREEQC simulation was used to determine the occurrence form of each ion in the PS. The mechanisms by which various electrokinetic treatment methods affected conductivity and pH distribution were carefully investigated. Electrokinetic treatment increased P concentration of the anode chamber from 22.7 mg/L to 63.39 mg/L, whereas K concentration increased from 15.26 mg/L to 93.44 mg/L. After AS-enhanced electrokinetic treatments, the concentrations of the different components were as follows: P, 131.66 mg/L; K, 198.2 mg/L; and Ca, 331.3 mg/L. The removal rate of soluble P in PS slices increased to 80.88% by 1.5 V/cm of treatment, and it increased to 94.04% after AS enhancement treatment. For water-soluble F, the removal rate from the PS slices in the anode region was 86.03%, decreasing F concentration in the electrode chamber to 9.57 × 10^-3 mg/L. Different extraction efficiencies and stability levels of each component in the PS were regulated at various electrode regions by using different processes such as electromigration, electro-osmotic flow, flocculation, and precipitation. Good results can be obtained if fluoride is solidified concurrently with the removal or recovery of P, K, Ca, and other elements using 2%-4% AS enhanced electrokinetic treatment. Furthermore, CaSO₄·2H₂O whiskers were produced in the electrode regions when AS content was 6%. The findings of this study indicated that the AS synergistic electrokinetic method is suitable for stabilizing F and removing heavy metals from PS, thus providing a promising technology for recycling valuable components such as P, K, Ca, and Sr and for the simultaneous production of CaSO₄·2H₂O whiskers. This study provides insights for developing novel technologies for the clean treatment and high-value utilization of PS.

The Role of pH, Electrodes, Surfactants, and Electrolytes in Electrokinetic Remediation of Contaminated Soil

Electrokinetic remediation has, in recent years, shown great potential in remediating polluted environments. The technology can efficiently remove heavy metals, chlorophenols, polychlorinated biphenyls, phenols, trichloroethane, benzene, toluene, ethylbenzene, and xylene (BTEX) compounds and entire petroleum hydrocarbons. Electrokinetic remediation makes use of electrolysis, electroosmosis, electrophoresis, diffusion, and electromigration as the five fundamental processes in achieving decontamination of polluted environments. These five processes depend on pH swings, voltage, electrodes, and electrolytes used in the electrochemical system. To apply this technology at the field scale, it is necessary to pursue the design of effective processes with low environmental impact to meet global sustainability standards. It is, therefore, imperative to understand the roles of the fundamental processes and their interactions in achieving effective and sustainable electrokinetic remediation in order to identify cleaner alternative solutions. This paper presents an overview of different processes involved in electrokinetic remediation with a focus on the effect of pH, electrodes, surfactants, and electrolytes that are applied in the remediation of contaminated soil and how these can be combined with cleaner technologies or alternative additives to achieve sustainable electrokinetic remediation. The electrokinetic phenomenon is described, followed by an evaluation of the impact of pH, surfactants, voltage, electrodes, and electrolytes in achieving effective and sustainable remediation.