Copper leaching from a sandy soil: mechanism and parameters affecting EDTA extraction.
A series of 24h batch tests of copper extraction from a sandy soil were performed by washing the soil with aqueous solution of ethylenediaminetetraacetic acid, EDTA. EDTA versus copper molar ratio were in the range between 1 (equimolar tests) and 13.3. The tests were performed at three selected liquid/solid ratio, 5, 12.5 and 25. Results show that decreasing the pH of the washing solution an higher copper extraction yield was achieved: an almost complete copper extraction was achieved after 23 h of mixing at a L/S = 5, and after 5 h of mixing at an L/S = 12.5. The mechanism of copper extraction was found to involve two sequential processes: the former dissolution of metal salts, that lead to an initial high concentration of both copper and some competitive cations (essentially Ca(2+)), and the following EDTA exchange reaction between calcium and copper complexes, which corresponded an increase of pH in the washing solution. A negligible extraction of Fe(3+) was also observed at the investigated operative conditions.
Di Palma
L
L
Dipartimento di Ingegneria Chimica, dei Materiali, delle Materie Prime, Metallurgia, Università di Roma La Sapienza, Italy. luca.di.palma@ingchim.ing.uniroma1.it
Ferrantelli
P
P
D002614:Chelating Agents / Q000737:chemistry; D011232:Chemical Precipitation; D003300:Copper / Q000737:chemistry*; D004492:Edetic Acid / Q000737:chemistry*; D006256:Hazardous Waste / Q000517:prevention & control*; D008956:Models, Chemical; D012822:Silicon Dioxide; D012989:Soil Pollutants / Q000032:analysis*
D002614:Chelating Agents; D006256:Hazardous Waste; D012989:Soil Pollutants; D012822:Silicon Dioxide; D003300:Copper; D004492:Edetic Acid