Morphology, Mineralogy, and Solid–Liquid Phase Separation Characteristics of Cu and Zn Precipitates Produced with Biogenic Sulfide

• Published in: Environmental science & technology 2014-01, Vol.48 (1), p.664-673
• Main Authors: Villa-Gomez, D. K, van Hullebusch, E. D, Maestro, R, Farges, F, Nikitenko, S, Kramer, H, Gonzalez-Gil, G, Lens, P. N. L
• Format: Article
• Language: English
• Subjects: Agglomeration; Analytical chemistry; Applied sciences; Biological and medical sciences; Biological treatment of waters; Bioreactors; Biotechnology; Chemical Precipitation; Copper; Copper - chemistry; Copper - isolation & purification; Durapatite - chemistry; Earth Sciences; Environment and pollution; Exact sciences and technology; Fluorescence; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Industrial applications and implications. Economical aspects; Industrial wastewaters; Mineralogy; Minerals - chemistry; Morphology; Particle Size; Pollution; Scanning electron microscopy; Sciences of the Universe; Spectrum analysis; Sulfides - chemistry; Wastewaters; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - isolation & purification; Water treatment and pollution; X-Ray Absorption Spectroscopy; Zinc; Zinc - chemistry; Zinc - isolation & purification; Zinc Compounds - chemistry
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es402795x

The morphology, mineralogy, and solid–liquid phase separation of the Cu and Zn precipitates formed with sulfide produced in a sulfate-reducing bioreactor were studied at pH 3, 5, and 7. The precipitates formed at pH 7 display faster settling rates, better dewaterability, and higher concentrations of settleable solids as compared to the precipitates formed at pH 3 and 5. These differences were linked to the agglomeration of the sulfidic precipitates and coprecipitation of the phosphate added to the bioreactor influent. The Cu and Zn quenched the intensity of the dissolved organic matter peaks identified by fluorescence–excitation emission matrix spectroscopy, suggesting a binding mechanism that decreases supersaturation, especially at pH 5. X-ray absorption fine structure spectroscopy analyses confirmed the precipitation of Zn–S as sphalerite and Cu–S as covellite in all samples, but also revealed the presence of Zn sorbed on hydroxyapatite. These analyses further showed that CuS structures remained amorphous regardless of the pH, whereas the ZnS structure was more organized at pH 5 as compared to the ZnS formed at pH 3 and 7, in agreement with the cubic sphalerite-type structures observed through scanning electron microscopy at pH 5.