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

Abstract

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.

Anaerobic Digestion Alters Copper and Zinc Speciation

“…27 Cu(I)-S could thus represent an amorphous Cu sulfide phase with a disordered local structure similar to that of Cu(I)methionine. This hypothesis has been well documented in the literature, for instance Villa-Gomez et al 40 suggested that the instantaneous reaction kinetics and low Cu sulfide solubility over the entire pH range makes Cu sulfide precipitation prevail over the formation of another Cu species, while also leading to the formation of amorphous Cu sulfide precipitates. The studies of Shea and Helz 41 and Pattrick et al 42 also demonstrated the precipitation of amorphous Cu sulfide in batch experiments at room temperature and in anaerobic conditions.…”

Highly-defective nanocrystals of ZnS formed via dissimilatory bacterial sulfate reduction: A comparative study with their abiogenic analogues

“…Among the efforts to synthesize metal sulfide nanostructures of specific physicochemical properties, the biological pathways via microbial sulfate-reduction are gaining noticeable traction being less energy-intensive and eco-friendly. To date, a variety of microorganisms including bacteria, algae, yeasts, and fungi have been, or are being, tested for the ability to synthesize metal sulfide nanoparticles (Bai et al, 2006;Mandal et al, 2006;Zhou et al, 2010;da Costa et al, 2012;Duran and Seabra, 2012;Hazra et al, 2012;Edwards et al, 2013;Miradeh et al, 2013;Su et al, 2013;Villa-Gomez et al, 2013;Mala and Rose, 2014;Moon et al, 2014).…”

Abiological Granular Sludge Formation Benefit for Heavy Metal Wastewater Treatment Using Sulfide Precipitation

“…). This sludge settling performance was also much better than that in the SRB process . Furthermore, the moisture content was reduced from 99 to 95% due to the formation of ABGS.…”

“…In sulfide precipitation, the source of sulfide can be chemicals (such as Na 2 S) . However, Na 2 S precipitation is always limited by its low‐effective sludge solid–liquid separation.…”