Periplasmic bacterial biomineralization of copper sulfide nanoparticles

Metal sulfides are a common group of extracellular bacterial biominerals. Only few cases of intracellular biomineralization have been reported in this group, mostly limited to greigite (Fe3S4) in magnetotactic bacteria. Here, we report the intracellular but periplasmic biomineralization of copper sulfide by the magnetotactic bacterium Desulfamplus magnetovallimortis (strain BW-1) that is known to mineralize greigite and magnetite (Fe3O4) in the cytoplasm. BW-1 produces hundreds of spherical nanoparticles, composed of 1-2 nm substructures of a poorly crystalline hexagonal copper sulfide that remains in a thermodynamically unstable state. Differential proteomics suggests that periplasmic proteins, such as a DegP-like protein and a heavy metal-binding protein, could be involved in this process. The unexpected periplasmic formation of copper sulfide nanoparticles in BW-1 reveals previously unknown possibilities for intracellular biomineralization.

Current progress of metal sulfides derived from metal organic frameworks for advanced electrocatalysis: potential electrocatalysts with diverse applications

The large-scale application of clean electrochemical storage and conversion devices such as water splitting and Zn-air batteries greatly depends on the development of low cost and highly efficient electrocatalysts. Transitional...

Rh, Ir, and Ru Partitioning in the Cu-Poor IPGE Massive Ores, Talnakh Intrusion, Skalisty Mine, Russia

Pyrrhotite (or Cu-poor) massive ores of the Skalisty mine located in Siberia, Russia, are unique in terms of their geochemical features. These ores are Ni-rich with Ni/Cu ratios in the range 1.3–1.9 and contain up to 12.25 ppm Ir + Rh + Ru in bulk composition, one of the highest IPGE contents for the Norilsk-Talnakh ore camp. The reasons behind such significant IPGE Contents cannot simply be explained by the influence of discrete platinum-group minerals on the final bulk composition of IPGE because only inclusions of Pd minerals such as menshikovite, majakite, and mertieite II in Pd-maucherite were observed. According to LA-ICP-MS data obtained, base metal sulfides such as pyrrhotite, pentlandite, and pyrite contain IPGE as the trace elements. The most significant IPGE concentrator being Py, which occurs only in the least fractionated ores, and contains Os up to 4.8 ppm, Ir about 6.9 ppm, Ru about 38.3 ppm, Rh about 36 ppm, and Pt about 62.6 ppm. High IPGE contents in the sulfide melt may be due to high degrees of partial melting of the mantle, interaction with several low-grade IPGE impulses of magma, and (or) fractionation of the sulfide melt in the magma chamber.

Review elucidating graphene derivatives (GO/rGO) supported metal sulfides based hybrid nanocomposites for efficient photocatalytic dye degradation

Photocatalysis by utilizing semiconductors for the removal of toxic pollutants has gained tremendous interest for remediation purposes. The organic pollutants usually include; pesticides, dyes and other phenolic compounds. An imperative restraint associated with the photocatalytic effectiveness of the catalyst is the rapid recombination of the light generated electrons and holes. The particle agglomeration and electron-hole recombination hinders the rate of pollutant removal. For decades, researchers have used metal-sulfides efficiently for photocatalytic dye degradation. The recent use of hybrid nanomaterials with the combination of graphene derivatives such as graphene oxide and reduced graphene oxide (GO/rGO)-metal sulfide has gained interest. These composites have displayed an impressive upsurge in the photocatalytic activity of materials. The current review describes the various researches on dye photodegradation by employing (GO/rGO)-metal sulfide, exhibiting a boosted potential for photocatalytic dye degradation. A comprehensive study on (CuS, ZnS and CdS)–GO/rGO hybrid composites have been discussed in detail for effective photocatalytic dye degradation in this review. Astonishingly improved dye degradation rates were observed in all these studies employing such hybrid composites. The several studies described in the review highlighted the varying degradation rates based on diverse research parameters and efficacy of graphene derivatives for enhancement of photocatalytic activity.

Laboratory-Based Bacterial Weathering of the Merensky Reef and Its Impact on Platinum Group Mineral Migration

Weathering of the Merensky reef was enhanced under laboratory conditions by Fe- and S-oxidizing bacteria: Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans. These bacteria preferentially colonized pyrrhotite and pyrite, versus pentlandite and chalcopyrite (all of which were common within the rock substrate), promoting weathering. Weathering of base metal sulfides resulted in the precipitation of Fe oxides, Fe phosphate, and elemental sulfur as secondary minerals. Fe pyroxene weathered readily under acidic conditions and resulted in mineral dissolution, while other silicates (orthopyroxene and plagio-clase) precipitated Fe phosphate spherules or coatings on their surface. The deterioration of the platinum group metal (PGM) matrix (base metal sulfides and silicates) and the occurrence of a platinum grain associated with platinum nanoparticles observed in the biotic thin sections demonstrate that biogeochemical acid weathering is an important step in the active release of intact PGM grains. A platinum grain embedded in secondary Fe oxides/phosphate that had settled by gravity within the weathering solution demonstrates that secondary minerals that formed during weathering of PGM-hosting minerals also represent targets in PGM exploration by trapping and potentially slowing PGM migration. Dispersion halos surrounding or occurring downstream from PGM occurrences will likely produce two physical target classes—i.e., grains and colloids—under surficial weathering conditions.