EDTA Leaching of Cu Contaminated Soils Using Ozone/UV for Treatment and Reuse of Washing Solution in a Closed Loop

Abstract

Ozone and UV irradiation were used for oxidative decomposition of EDTA-Cu complexes in washing solution obtained during multi-step leaching of Cu (344,1±36.5 mg kg −1 ) contaminated vineyard soil with EDTA as a chelant. The released Cu was absorbed from the washing solution on a commercial mixture of metal absorbing minerals, and the treated washing solution then reused for removal of soil residual Cu-EDTA complexes in a closed-loop process. Six consecutive leaching steps (6×2.5 mmol kg −1 of EDTA) removed 38.8 % of Cu from soils, and reduced Cu soil mobility, determined using the toxicity characteristic leaching test (TCLP), by 28.5%. The final washing solution obtained after soil remediation was colourless, with a pH close to neutral (7.5±0.2) and with low concentrations of Cu and EDTA (0.51± 0.22 mg L −1 and 0.083 mM, respectively). The proposed remediation method has therefore potential not just to recycle and save process water, but also not to produce toxic wastewaters. Soil treatment did not substantially alter the soil properties determined by pedological analysis, and had relatively little impact on soil hydraulic conductivity and soil water sorption capacity.

EDTA leaching of Cu contaminated soil using electrochemical treatment of the washing solution

“…The released metals were then removed from the washing solution by absorption on zeolite material. However, EDTA leaching of Cu contaminated soil produced a washing solution with an intensive green color [7]. The coloration probably blocked UV light and made ozone-UV based AOP efficient only when we treated the soil with low (2.5 mM kg −1 ) EDTA concentrations [7].…”

“…However, EDTA leaching of Cu contaminated soil produced a washing solution with an intensive green color [7]. The coloration probably blocked UV light and made ozone-UV based AOP efficient only when we treated the soil with low (2.5 mM kg −1 ) EDTA concentrations [7]. Another practical problem was removal of the released Cu, which consumed a significant quantity of expensive absorbent [7,8] and which later needs to be deposited.…”

Inorganic Amendments to Decrease metal Availability in Soils of Recreational Urban Areas: Limitations to their Efficiency and Possible Drawbacks

“…Several papers have been published by Leštan and co-workers (e.g. Udovič and Leštan 2007) where this material was used as metal immobilizer from solution, after extraction of the metals from a contaminated soil with solutions of a given chelator (ethylene-diamine-tetraacetic acid, EDTA, or ethylene-diamine disuccinate, [S,S]-EDDS) by means of a closed-loop process and removal of the chelator from the solution by oxidation, but little more has been documented in this respect.…”

Remediation of Cu-contaminated soil using chelant and EAOP

“…Finzgar and Lestan, [17] and Udovic and Lestan [18] reported that multiple-dosages of EDTA were substantially more effective for leaching Pb, Zn, Cd and Cu from contaminated soils than using one large single dose. Similarly, three-dosages of 5 mmol kg −1 [S,S]-EDDS removed significantly more Cu than one single dose of 15 mmol kg −1 [S,S]-EDDS (Fig.…”