Author(s)

C Ferreira, A B Ribeiro & L M Ottosen

Abstract

Study of different assisting agents for the removal of heavy metals from MSW fly ashes C. Ferreira1,2, A. B. Ribeiro3, L. M. Ottosen2 1 Escola Sup. Agraria de Coimbra, Portugal. 2Dep. of Civil Engineering, DTU, Denmark. 3DCEA-Faculdade de Ciencias e Tecnologia, Univ. Nova de Lisboa, Portugal. Abstract This work presents the results of the extraction of Zn, Pb, Cu, Mn and Cd from Municipal Solid Waste (MSW) incinerator fly ashes. In the present work the following assisting agents were evaluated for their capacity to remove heavy metals from fly ash into solution, in a wide pH range: EDTA, ammonium acetate, ammonium citrate, Na-Gluconate and water. Results obtained in these extractions indicate that cadmium and lead present the highest removals with 75% and 61% of total concentration, although not obtained with the same extraction agent. Removal for the other metals was up to 49% for Cu, 20% for Zn and only 2% for Mn. The results indicate that Na-gluconate presents the best removal efficiencies for both zinc and lead, while performing also well for the other metals. Na- gluconate is aprox. 2 times more efficient in extracting lead than EDTA (which is the second best) and 61 times better than ammonium acetate. Ammonium acetate performs best for cadmium and copper. Na-gluconate stands out as a good assisting agent. Besides the good performance observed in the extraction tests it also presents some additional characteristics such as non-toxicity, good performance at high pH values, formation of charged complexes with the metals and reasonable price, that points out the possibility of using it as an assisting agent in the electrodialytic remediation of fly ash.

Keywords