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Heavy Metals Leaching from Fluorescent Lamps Physicochemical Treatment Residuals Heavy metals leaching from fluorescent lamps physicochemical treatment residuals

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Author(s): Inga Urniežaitė | Gintaras Denafas

Journal: Environmental Research, Engineering and Management
ISSN 1392-1649

Volume: 49;
Issue: 3;
Start page: 64;
Date: 2009;
Original page

Keywords: mercury | fluorescent lamps | leaching kinetics | heavy metals | EDTA

ABSTRACT
Waste generated during the process of physicochemical treatment of fluorescent lamps contains relatively high quantities of heavy metals. Physicochemical treatment is employed with the aim to concentrate toxic substances present in the lamps. This study attempts to evaluate the leaching properties of treatment residuals. Waste of a similar composition has been not fully researched yet, thus the limited data are available on leaching of heavy metals from residues of similar processes. Concentrations of heavy metals leaching from the residuals into various complex-forming agents (ethylenediamine tetraacetic acid (EDTA), Citric acid, Tartar acid) have been analyzed. EDTA is selected for further kinetics experiments as a complex-forming agent known for its most effective leaching properties as stated in literature on this subject and in most cases practically observed. Kinetic experiments have shown that almost all water-soluble heavy metals are mobilized from the samples within the period of approximately 20 hours, with time variation for different heavy metals. An increase in the leaching concentrations when using EDTA as a complex-forming agent has been observed. Extraction with EDTA has resulted in heavy metal concentrations ranging from 0.41 mg kg-1 of dry mass (DM) for Co to as much as 1576.00 mg kg-1 DM for Zn. Exposure of the samples to different temperatures has revealed the influence of the temperature as an important factor of experimental conditions. The concentration of leaching Hg has increased 3 times after heating the samples in the temperatures from 20o to 120oC. Waste, generated during the process of physicochemical treatment of fluorescent lamps, contains relatively high amounts of heavy metals. Physicochemical treatment is employed with the aim to concentrate toxic substances present in the lamps. The aim of this study was to evaluate leaching properties of the treatment residuals. Waste of similar composition has not been widely investigated earlier, thus limited data is available on leaching of heavy metals from residues of similar processes. Concentrations of heavy metals leaching from the residuals into various complex-forming agents (ethylenediamine tetraacetic acid (EDTA), Citric acid, Tartar acid) were analyzed. EDTA was selected for further kinetics experiments, as the complex-forming agent, known for the most effective leaching properties, as stated in the literature and observed practically in most cases. Kinetic experiments showed that almost all water-soluble heavy metals were mobilized from the samples within the period of approximately 20 hours, with time variation for different heavy metals. Increase in the leaching concentrations when using EDTA as complex-forming agent was observed. Extraction with EDTA resulted in heavy metals concentrations ranging from 0,41 mg kg-1 of dry mass (DM) for Co to as much as 1576,00 mg kg-1 DM for Zn. Exposing the samples to different temperatures revealed the influence of the temperature as an important factor of the experimental conditions. The leachable Hg concentration increased 3 times after heating the samples in the temperatures from 20oC to 120oC.

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