Precipitation and recovery of metal sulfides from metal containing acidic wastewater in a sulfidogenic down-flow fluidized bed reactor.
This study reports the feasibility of recovering metal precipitates from a synthetic acidic wastewater containing ethanol, Fe, Zn, and Cd at an organic loading rate of 2.5 g COD/L-day and a COD to sulfate ratio of 0.8 in a sulfate reducing down-flow fluidized bed reactor. The metals were added at increasing loading rates: Fe from 104 to 320 mg/L-day, Zn from 20 to 220 mg/L-day, and Cd from 5 to 20 mg/L-day. The maximum COD and sulfate removals attained were 54% and 41%, respectively. The biofilm reactor was operated at pH as low as 5.0 with stable performance, and no adverse effect over COD consumption or sulfide production was observed. The metals precipitation efficiencies obtained for Fe, Zn, and Cd exceeded 99.7%, 99.3%, and 99.4%, respectively. The total recovered precipitate was estimated to be 90% of the theoretical mass expected as metal sulfides. The precipitate was mainly recovered from the bottom of the reactor and the equalizer. The analysis of the precipitates showed the presence of pyrite (FeS2), sphalerite (ZnS) and greenockite (CdS); no metal hydroxides or carbonates in crystalline phases were identified. This study is the first in reporting the feasibility to recover metal sulfides separated from the biomass in a sulfate reducing process in one stage.
Gallegos-Garcia
Marisol
M
División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, Col. Lomas 4a. Sección, C.P. 78216, San Luis Potosí, S.L.P., México.
Celis
Lourdes B
LB
Rangel-Méndez
René
R
Razo-Flores
Elías
E
D018441:Biofilms; D019149:Bioreactors; D011232:Chemical Precipitation; D000431:Ethanol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D008670:Metals / Q000378:metabolism*; D013440:Sulfides / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*; D017967:Zinc Compounds / Q000378:metabolism
D008670:Metals; D013440:Sulfides; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds; C011342:pyrite; D000431:Ethanol; D007501:Iron; C031238:zinc sulfide