Recycling of lead-contaminated EDTA wastewater.
Ethylene diaminetetraacetic acid (EDTA) is one of the chelating agents used in the soil washing process for the decontamination of lead-contaminated soil. Lead-EDTA complexes in the wastewater from the soil washing process must be removed before the wastewater can be safely discharged. This study outlines a method to recycle Pb-EDTA wastewater by substituting the Pb complexed with EDTA with Fe(III) ions at low pH, followed by precipitation of Pb ions with phosphate or sulfate ions. Fe(III) ions complexed with EDTA were then precipitated at high pH using sodium hydroxide. The resulting solution (Fe-precipitated solution) was tested on three lead-contaminated soils. The Fe-precipitated EDTA solution was found to have similar extraction capabilities as fresh EDTA solution. Experimental results showed that the recycled EDTA solution may be recycled several times without losing its extractive power. Recycled EDTA wastewater with phosphate precipitation was found to be slightly more effective than recycled EDTA solution using sulfate precipitation. The recycling procedure may be applied to wastewater generated during soil washing of lead-contaminated soil, resulting in a reduction in wastewater generated and savings in the amount of EDTA used.
Effect of adsorption of Pb(II) and Cd(II) ions in the presence of EDTA on the characteristics of electrical double layers at the ion exchanger/NaCl electrolyte solution interface.
The main propose of this work was to describe the basic parameters of electrical double layer structures of the ion exchanger/NaCl before and after the sorption process of Pb(II) and Cd(II) ions from aqueous solutions in the presence of the complexing agent EDTA (ethylenediaminetetraacetic acid). In the studies the following ion exchangers were used: cation exchangers Micro-ionex (in the H(+) and NH(+)(4) forms), Dowex 50W x 4 (in the H(+) form), and Dowex 50W x 12 (in the H(+) form); anion exchangers Dowex 1 x 4 (in the Cl(-) form) and Dowex 1 x 8 (in the Cl(-) form). Study of the physicochemical properties of the sample surface was carried out. The influence of ionic strength, pH, and solution interface was investigated. Electrophoretic mobility, surface charge density, and parameters for different concentrations of the electrolytes under question were presented. pH was changed from 3 to 10. The studies were carried out for the M(II)-EDTA = 1:1 system. The effects of the concentration of the solution containing the above-noted complexes and of the ion exchange/solution phase contact time on sorption capacities of the ion exchangers under consideration were studied. Kinetic parameters of the sorption process were also determined.
The Lay of the Land: English Landscape Themes in Early Modern Painting in England
The Lay of the Land: English Landscape Themes in Early Modern Painting in England