Cesaro Raffaele, Esposito Giovanni
Department of Hydraulic, Geotechnical and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy.
J Environ Monit. 2009 Feb;11(2):307-13. doi: 10.1039/b816295f. Epub 2008 Dec 9.
The present research deals with the optimization of the operating parameters (cathode replacement time, hydraulic retention time, current intensity and pH) of an electrochemical process aimed at the regeneration of a soil washing EDTA solution used for heavy metal extraction from a natural contaminated soil (excavated from Bellolampo, Palermo, Italy), which was vastly polluted with Cu (59 261.0 mg kg(-1)), Pb (14 178.1 mg kg(-1)) and Zn (14 084.9 mg kg(-1)). The electrolytic regeneration of the exhausted washing solution was performed in a laboratory scale electrolytic cell with 50 ml each cathodic and anodic chambers divided by a cation exchange membrane. Experiments II and III showed maximum Cu and Zn removal efficiencies from the EDTA solution, of 99.2+/-0.2 and 31.5+/-9.3%, respectively, when a current intensity of 0.25 A and a hydraulic retention time of 60 min were applied to the electrolytic cell, while the maximum Pb removal efficiency of 70.9+/-4.6% was obtained with a current intensity of 1.25 A and a hydraulic retention time of 60 min. During Experiment I the overall heavy metals removal efficiency was stable and close to 90% up to 20 h, while decreased to values lower than 80% after 40 h, indicating the occurrence of a significant saturation of the cathode graphite bed between 20 and 40 h. The capability of the regenerated EDTA solution to treat heavy metals polluted soils was tested in further experiments applying both a single and a multi-step washing treatment procedure. In particular, the latter showed the feasibility to increase heavy metal soil extractions over subsequent washing steps with Cu, Pb and Zn total removal efficiencies of 52.6, 100.0 and 41.3%, respectively.
本研究涉及对一种电化学过程操作参数（阴极更换时间、水力停留时间、电流强度和pH值）的优化，该过程旨在再生用于从天然污染土壤（从意大利巴勒莫的贝洛兰波挖掘）中提取重金属的土壤洗涤乙二胺四乙酸（EDTA）溶液，该土壤被铜（59261.0毫克/千克）、铅（14178.1毫克/千克）和锌（14084.9毫克/千克）严重污染。在实验室规模的电解池中进行耗尽洗涤溶液的电解再生，阴极室和阳极室各50毫升，由阳离子交换膜隔开。实验二和实验三表明，当向电解池施加0.25安的电流强度和60分钟的水力停留时间时，从EDTA溶液中去除铜和锌的最大效率分别为99.2±0.2%和31.5±9.3%，而当电流强度为1.25安和水力停留时间为60分钟时，铅的最大去除效率为70.9±4.6%。在实验一中，直至20小时，重金属的总体去除效率稳定且接近90%，而在40小时后降至低于80%的值，表明在20至40小时之间阴极石墨床发生了显著饱和。在进一步的实验中，采用单步和多步洗涤处理程序测试了再生EDTA溶液处理重金属污染土壤的能力。特别是，后者表明在后续洗涤步骤中提高重金属土壤提取量是可行的，铜、铅和锌的总去除效率分别为52.6%、100.0%和41.3%。
