Effects of catholyte conditioning on electrokinetic extraction of copper from mine tailings.
Effect of electrokinetic treatment on copper partitioning and distribution in mine tailings were studied. In particular the effects of catholyte enhancement by HAc-NaAc, HCl, HAc-NaAc+EDTA and lactic acid+NaOH were evaluated. The results show that conditioning the catholyte plays a very important role in improving Cu removal. When HAc-NaAc is used in the catholyte, the removal percentage of total Cu from the mine tailings sample reached 12.3% under 40 V in 15 days of treatment. The removal percentage of Cu increased to 31.2% when EDTA was used together with HAc-NaAc in the catholyte. At the same time, increasing the applied voltage and treatment time result in an increase in the Cu removal from the mine tailings. Compared with HAc-NaAc (pH=3.52), the use of lactic acid+NaOH (pH=3.15) in the catholyte resulted in better performance in Cu removal from the mine tailings. HCl treatment resulted in removal of about 17.5% of Cu from the mine tailings; however, it resulted in production of significant amounts of toxic chlorine gas. Copper partitioning in the mine tailings was analyzed before and after the electrokinetic treatments. The analysis was conducted using 0.25 mol/l MgCl2 and 0.5 mol/l HCl as extractants, consequently, to assess the mobility of Cu after treatment. The results showed that lowering the pH of the mine tailings increased the exchangeable Cu fraction (or the portion extracted by MgCl2). Accordingly, further acidification results in an increased mobility of Cu and increase in the environmental risk of mine tailings.
The State Key laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. dmzhou@issas.ac.cn
Dong-Mei
DM
Zhou
Chang-Fen
CF
Deng
Akram N
AN
Alshawabkeh
Long
L
Cang
D019342:Acetic Acid / Q000737:chemistry; D002681:China; D003300:Copper / Q000737:chemistry / Q000302:isolation & purification*; D004492:Edetic Acid / Q000737:chemistry; D004563:Electrochemistry; D004787:Environmental Pollution / Q000517:prevention & control; D006851:Hydrochloric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis; D019344:Lactic Acid / Q000737:chemistry; D008906:Mining; D010084:Oxidation-Reduction; D019346:Sodium Acetate / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D012989:Soil Pollutants / Q000302:isolation & purification*
D007220:Industrial Waste; D012989:Soil Pollutants; D019344:Lactic Acid; D019346:Sodium Acetate; D012972:Sodium Hydroxide; D003300:Copper; D004492:Edetic Acid; D019342:Acetic Acid; D006851:Hydrochloric Acid