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Precipitation and recovery of metal sulfides from metal containing acidic wastewater in a sulfidogenic down‐flow fluidized bed reactor
Author(s) -
GallegosGarcia Marisol,
Celis Lourdes B.,
RangelMéndez René,
RazoFlores Elías
Publication year - 2008
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.22049
Subject(s) - sulfate , sulfide , chemistry , precipitation , fluidized bed , wastewater , metal , sulfur , effluent , pyrite , nuclear chemistry , environmental chemistry , inorganic chemistry , mineralogy , waste management , organic chemistry , physics , meteorology , engineering
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 (FeS 2 ), 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. Biotechnol. Bioeng. 2009;102: 91–99. © 2008 Wiley Periodicals, Inc.