Publications (3)6.57 Total impact
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ABSTRACT: Increasing attention has been given, by the industrial sector, to the removal of heavy metals from liquid effluents to satisfy environmental regulations. For this purpose, the most common methods utilized include: chemical precipitation, cementation, ion exchange, adsorption and solvent extraction. All these methods have limitations such as slow kinetics, low adsorption capacity and they are usually very expensive. Thus, new technologies for heavy metal removal are of great interest. This study consisted on a screening of industrial minerals to check their efficiencies to remove mercury from liquid effluents. The methodology employed a batch adsorption technique. The tested minerals included: atapulgites, zeolites, magnetites, kaolin, vermiculite and bentonite. Results show relatively high efficiencies of magnetite and zeolite on mercury removal. These minerals were capable to remove mercury species from effluents with concentrations reaching 1,000 ppm, corresponding to a sorption capacity of 10,000 mg Hg/kg. The sorption maximum was not reached in these tests. In addition, it became evident the importance of mercury speciation at the solid:liquid interface, with relevant consequences on the application of this technology to effluent treatment.Science of The Total Environment 10/2006; 368(1):403-6. · 3.29 Impact Factor
Article: Field assessment of lead immobilization in a contaminated soil after phosphate application.[show abstract] [hide abstract]
ABSTRACT: A pilot-scale field demonstration was conducted at a Pb-contaminated site to assess the effectiveness of Pb immobilization using P amendments. The test site was contaminated by past battery recycling activities, with average soil Pb concentration of 1.16%. Phosphate amendments were applied at a 4.0 molar ratio of P/Pb with three treatments: T1, 100% P from H(3)PO(4); T2, 50% from H(3)PO(4)+50% from Ca(H(2)PO(4))(2); and T3, 50% from H(3)PO(4)+5% phosphate rock. Soil samples were collected and characterized 220 days after P application. Surface soil pH was reduced from 6.45 to 5.05 in T1, to 5.22 in T2, and to 5.71 in T3. Phosphate treatments effectively transformed up to 60% of total soil Pb from the non-residual fraction (sum of water soluble and exchangeable, carbonate, Fe-Mn oxide, and organic fractions) to the residual fraction relative to the control. In addition, P treatments reduced Toxicity Characteristic Leaching Procedure (TCLP) Pb from 82 mg l(-1) to below EPA's regulatory level of 5 mg l(-1) in the surface soil. Scanning electron microscopy-energy dispersive X-ray elemental analysis and X-ray diffraction analysis indicated formation of insoluble chloropyromorphite [Pb(5)(PO(4))(3)Cl] mineral in the P-treated soils. Although H(3)PO(4) is necessary to dissolve meta-stable Pb in soil for further lead immobilization, it should be used with caution due to its potential secondary contamination. A mixture of H(3)PO(4) and Ca(H(2)PO(4))(2) or phosphate rock was effective in immobilizing Pb with minimum adverse impacts associated with pH reduction.Science of The Total Environment 05/2003; 305(1-3):117-27. · 3.29 Impact Factor
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ABSTRACT: A long-term field-scale demonstration project on the feasibility of using P to immobilize Pb in a Pb-contaminated urban soil was conducted. Phosphate was applied at an average rate of 3040 mg P/kg soil based on a P/Pb molar ration of 4.0, with four treatments: T0, no P application; T1, H3PO4 only; T2, 1/2 H3PO4+1/2 CaH2PO4; and T3, 1/2 H3PO4+1/2 phosphate rock. Soil samples were collected and analyzed 220 days after the P applications. For all P treatments, toxicity characteristic leaching procedure (TCLP) extractable Pb levels in surface soils (0–10 cm) were reduced to below 5.0 mg Pb/l, with T2 also effective in reducing the TCLP Pb level in subsurface soils (10–30 cm, <4.63 mg/l). Sequential extraction analysis indicates that P was effective in transforming soil Pb from non-residual fractions to a residual fraction. Such a transformation was mainly through dissolution of Pb associated with carbonate fraction and precipitation of pyromorphite-like minerals, which were confirmed using X-ray diffraction (XRD). Among these three treatments, T3 was the most effective in reducing Pb mobility and minimizing P and Pb leaching in the soil. Our research clearly demonstrates that P amendments were effective in immobilizing Pb in contaminated soil.Advances in Environmental Research.