Effects of Moisture Content and Voltage Gradient on the Removal of Cd, Pb and Zn From a Calcareous Contaminated Soil

Document Type : Research Paper

Authors

Abstract

Electrokinetic removal of heavy metals from the contaminated soils seems an innovative approach for their remediation. This technique may require much less time for the removal particularly in the soil with lower permeability comparing to the conventional leaching methods. In the current study electrokinetic remediation of a calcareous soil contaminated by three heavy metals (Zn=1400 mg kg-1, Cd=15 mg kg-1 and Pb=250 mg kg-1) due to the release of sludge's from mining industry around Zanjan city north west of Iran, was investigated in disturbed soil columns. Treatments imposed during the experiment were three moisture contents (saturated, FC and 0.7 FC), and two voltage gradients (1.3 and 2.66 volts per cm of the column length). Effects of three electrolytes (distilled water, Acetic acid, EDTA), electrolyte circulation and anodes displacement on the removal efficiency were also studied. Experimental data showed that raising voltage gradient and water content both enhanced ion migration through the column and thus led to considerably grater removal. After 10 days imposing the above voltage gradient under saturation condition, the removal of Cd, Zn and Pb achieved to 32.6%, 31.3% and 18.9%, respectively. Reducing water content to 0.7 FC reduced the removal percents to 21%, 18.4% and 12.3%, respectively. The largest removal belonged to Cd; with Zn and Pb being the second and third in this respect.

Keywords

Main Subjects


1-   کارایی حذف فلزات سنگین در رطوبت اشباع نسبت به رطوبتهای دیگر بالاتر بوده و با کاهش رطوبت، درصد حذف فلزات سنگین کاهش می­یابد.
2-   تأثیر افزایش شیب ولتاژ در تیمارهای مختلف بر کارایی حذف فلزات سنگین نتایج متفاوتی دارد و در تیمار آندهای نزدیک شونده  و تیمار EDTA افزایش شیب ولتاژ بالاترین افزایش در کارایی حذف فلزات سنگین را دارد.
3-   موادی مانند EDTA به علت قدرت کمپلکس کنندگی بالا کارایی حذف فلزات سنگین توسط روش الکتروسینتیکی را تا حد قابل توجهی افزایش می­دهند.
4-     استفاده از مواد اسیدی در خاکهای آهکی در افزایش کارایی حذف فلزات سنگین چندان مؤثر نمی­باشد.
5-   استفاده از سیستم جریان گردشی به عنوان تعدیل کننده pH در خاک­هایی که ضریب آبگذری پایینی دارند در شیبهای ولتاژ بالا در افزایش کارایی حذف فلزات سنگین چندان موفقیت آمیز نمی­باشد.
 
منابع مورد استفاده
بیرامی ح، 1388، اصلاح الکتروسینتیکی یک خاک آلوده به Pb، Cd و Zn و راهکارهای افزایش کارایی آن، پایاننامه کارشناسی ارشد، دانشکده کشاورزی، دانشگاه تبریز.
Al-HamdanAZ and Reddy KR, 2008. Transient behavior of heavy metals in soils during electrokinetic remediation. Chemosphere 71:860–871.
Altaee A, Smith R and Mikhalovsky S, 2008. The feasibility of decontamination of reduced saline sediments from copper using the electrokinetic process. Journal of Environmental Management 88:1611–1618.
Altin A, Degirmenci M, 2005. Lead (II) removal from natural soils by enhanced electrokinetic remediation. Science of the Total Environment 337:1-10.
Baek K, Kim D, Park S, Ryu B, Bajargal T and Yang J, 2009. Electrolyte conditioning-enhanced electrokinetic remediation of arsenic-contaminated mine tailing. Journal of Hazardous Materials 161:457–462.
Darmawan and Wada SI, 2002. Effect of clay mineralogy on the feasibility of electrokinetic soil decontamination technology. Applied Clay Science 20:283-293.
Giannis A, Gidarakos E and Skouta A, 2008. Transport of cadmium and assessment of phytotoxicity after electrokinetic remediation. Journal of Environmental Management 86:535–544.
Kim D, Jeon C, Baek K, Ko S and Yang J, 2009. Electrokinetic remediation of fluorine-contaminated soil: Conditioning of anolyte. Journal of Hazardous Materials 161:565–569.
Kim SO, Moon SH and Kim KW. 2001. Removal of heavymetals from soils using enhanced electrokinetic soil processing. Water, Air, and Soil Pollution 125:259-272.
Kim SS and Han SJ, 2003. Application of an enhanced electrokinetic ion injection system to bioremediation. Water, Air, and Soil Pollution 146:365–377.
Lee HH, and Yang JW, 2000. A new method to control electrolytes pH by circulation system in electrokinetic soil remediation. Journal of Hazardous Materials B77:227-240.
Popov K, Glazkova I,  Yachmenev V and Nikolayev A, 2008. Electrokinetic remediation of concrete: Effect of chelating agents. Environmental Pollution 153:22-28.
Ravera M, Ciccarelli C, Gastaldi D, Rinaudo C, Castelli C and Osella D, 2006. An experiment in the electrokinetic removal of copper from soil contaminated by the brass industry. Chemosphere 63:950–955.
Reddy KR, Saichek RE, Maturi K and Ala P, 2002. Effects of soil moisture and heavy metal concentrations on electrokinetic remediation. Indian Geotechnical Journal 32(2):258- 288.
Reddy KR,  Xu CY and Chinthamreddy S, 2001. Assessment of electrokinetic removal of heavy metals from soils by sequential extraction analysis.Journal of Hazardous Materials B84279–296.
Reddy KR, Danda S and Saichek RE, 2004. Complicating factors of using ethylenediamine tetraacetic acid to enhance electrokinetic remediation of multiple heavy metals in clayey soils. Journal of Environmental Engineering 130(11):1357-1366.
Sah JG and Chen JY, 1998. Study of the electrokinetic process on Cd and Pb spiked soils. Journal of Hazardous Materials 58:301-315.
Saichek RE, Reddy KR, 2003. Effect of pH control at the anode for the electrokinetic removal of phenanthrene from kaolin soil. Chemosphere 51:273–287.
Sposito G, Lund LJ and Chang AC, 1982. Trace metal chemistry in arid-zone fields soil amended with sewage sludge. 1. Fractionation of Ni, Cu, Zn, Cd and Pb in solid phases. Soil Sci. Soc. Am. J. 46:260-264.
Turer D and  Genc A, 2005. Assessing effect of electrode configuration on the efficiency of electrokinetic remediation by sequential extraction analysis. Journal of Hazardous Materials B119:167–174.
Vázquez MV, Vasco DA,  Hernández-Luis F, Grandoso D, Lemus M, Benjumea DM and Arbelo CD,  2009. Electrokinetic study of the buffer capacity of some soils from Tenerife. Comparison with a volumetric technique. Geoderma 148:261–266.
Virkutyte J, Sillanpää M and Latostenmaa P, 2002. Electrokinetic soil remediation - critical overview. The Science of the Total Environment 289:97-121.
Wang JY, Huanga XJ, Kaob JCM and Stabnikova O, 2007. Simultaneous removal of organic contaminants and heavy metals from kaolin using an upward electrokinetic soil remediation process. Journal of Hazardous Materials 144:292-299.
Yuan S, Wu C, Wan J and Lu X, 2009. In situ removal of copper from sediments by a galvanic cell.Journal of Environmental Management 90:421-427.
Yuan C and Chiang T, 2008. Enhancement of electrokinetic remediation of arsenic spiked soil by chemical reagents. Journal of Hazardous Materials 152:309–315.
Zhou DM, Deng CF, Alshawabkeh AN and Cang L, 2005. Effects of catholyte conditioning on electrokinetic extraction of copper from mine tailings. Environment International 31:885 – 890.