Enhanced electrokinetic remediation of chromium-contaminated soil using approaching anodes

Abstract

As a new technology used for the cleaning of chromium-contaminated soil, worldwide interest in eletrokinetic (EK) remediation has grown considerably in recent times. However, owing to the fact that chromium exists as both cationic and anionic species in the soil, it is not an efficient method. This paper reports upon a study in which a process using approaching anodes (AAs) was used to enhance the removal efficiency of chromium by eletrokinetics. Two bench-scale experiments to remove chromium from contaminated soil were performed, one using a fixed anode (FA) and the other using AAs. In the AAs experiment, the anode moved toward the cathode by 7 cm every three days. After remediation, soil pH, total chromium, and fractionation of chromium in the soil were determined. The average removal efficiency of total chromium was 11.32% and 18.96% in the FA and AAs experiments, respectively. After remediation, acidic soil conditions throughout the soil were generated through the use of AAs, while 80% of the soil remained neutral or alkalic when using the FA approach. The acidic soil environment and high field intensity in the AAs experiment might have favored chromium desorption, dissolution and dissociation from the soil, plus the mobility of chromium in the soil was also enhanced. The results demonstrate that AAs used in the process of EK remediation can enhance the efficiency of chromium removal from soil.

Effect of polarity-reversal on electrokinetic enhanced bioremediation of Pyrene contaminated soil

“…The pH jump is detrimental to microorganism and thus hampers the efficiency of bioremediation. To overcome the drawback, a series of methods were used to control the pH, such as injecting solution [11][12][13], fixing the cathode and approaching anodes [14,15], electrolyte circulation [16,17] and non-uniform electrokinetics [5,18]. Polarity reversal was proposed for neutralizing soil pH and stimulating bioremediation of organic contaminated soil [4,9,19].…”

Remediation Experimental of Chromium- Contaminated Soft Soil by Temperature-Controlled Electric Combined Leaching

“…After 5 days of electrokinetic remediation, the total removal rates of heavy metals were 20-51%, 26-65% and 34-69%, respectively, and the removal rate of chromium was the highest when citric acid solution was used as electrolyte. Li et al [10] proposed to use the method close to the anode to enhance the effect of electro remediation of chromium contaminated soil, that is, the anode moves 7cm to the cathode every three days, which is beneficial to the desorption and dissolution of chromium, promote the dissociation of chromium from the soil, strengthen the migration ability of chromium in soil, and improve the removal efficiency of chromium in soil. The effects of acidification time, concentrations of acetic acid and citric acid on removal of chromium from soils were studied by changing the acidification pretreatment conditions, and then speciation analysis of the chromium was conducted to study the regularity of Cr in different speciation's [11].…”

Untitled

“…It has been confirmed that the initiates movement of contaminants by electromigration, electro osmosis, electrolysis and diffusion [5], and non-ionic species are transported along with the electroosmotic flow [6]. The key electron transfer reactions that occur at electrodes during the EKR process is the electrolysis of water: 12H 2 O+2e -→2OH -+H 2 (g) Equation 2Application of Combined TechnologyAccording to the experiments and pilot-scale studies conducted in the last 10 years, metals such as cadmium [7], chromium [8][9][10][11][12][13][14][15][16][17][18][19], copper [20][21][22][23][24][25][26][27][28], lead [29][30][31][32][33][34][35], manganese [36,37], mercury [38,39], nickel [40], uranium [41], and zinc [42], as well as dye [43,44], hydrocarbon[45-54], organochlorines [55-59], polychlorinated biphenyls [60,61], phenols [62,63], chlorophenols [64], are suitable for electrokinetic remediation and recovery. The author divides those technologies combined with EKR into physical technology, biotechnology and chemical technology, provides the application of these combination-technologies in soil remediation and evaluates these technologies.…”

“…According to the experiments and pilot-scale studies conducted in the last 10 years, metals such as cadmium [7], chromium [8][9][10][11][12][13][14][15][16][17][18][19], copper [20][21][22][23][24][25][26][27][28], lead [29][30][31][32][33][34][35], manganese [36,37], mercury [38,39], nickel [40], uranium [41], and zinc [42], as well as dye [43,44], hydrocarbon[45-54], organochlorines [55-59], polychlorinated biphenyls [60,61], phenols [62,63], chlorophenols [64], are suitable for electrokinetic remediation and recovery. The author divides those technologies combined with EKR into physical technology, biotechnology and chemical technology, provides the application of these combination-technologies in soil remediation and evaluates these technologies.…”