Fixing sulfur dioxide by feeding calcine oxide into the rotary volatilization kiln in zinc smelting plant.

Sulfur dioxide (SO2) is a toxic pollutant and its fixation is a high cost but imperative task for sulfide metallurgy industry. Although being a mature technology for on-line fixation of SO2 by limestone injection in coal-fired boilers, its application is rarely investigated in the sulfide metallurgy plant. Extending this technology to the metallurgy industry is highly plausible, but with the feasibility and practicability waiting to be uncovered. Herein, feeding CaO into the rotary volatilization kiln as SO2-fixation agent is demonstrated to be an efficient in-furnace desulfurization strategy for zinc smelting plant. The sulfur distribution within the entire smelting process is systematically analyzed, determining that the critical procedure for pressuring the desulfurization system is the rotary volatilization kiln. The thermodynamics analysis shows that addition of CaO is feasible for SO2 fixation by forming CaS or restraining the reductive decomposition of SO42-. The industrial tests, including the online monitoring of kiln flue gas and kiln slag analysis, validate the thermodynamics analysis, realizing a 24.6% reduction of SO2 in the flue gas by converting gaseous SO2 to solid CaS via feeding 20% CaO. The present study highlights an effective strategy for on-line fixing the SO2, being a potential way for relieving the desulfurization pressures in zinc sulfide metallurgy plant.

Extending Ag Nanoparticles as Colorimetric Sensor to Industrial Zinc Electrolyte for Cobalt Ion Detection.

The direct and rapid determination of trace cobalt ion (Co2+) in the electrolyte of zinc smelting plants is urgently needed but is impeded by the severe interference of extremely high-concentration zinc ions in the solution. Herein, colorimetric detection of Co2+ by the polyvinylpyrrolidone functionalized silver nanoparticles (PVP-AgNPs) is realized in solutions with the Zn/Co ratio being high, up to (0.8-5) × 104, which is located within the ratio range in industrial solution. The high concentration of Zn2+ induces a strong attenuation of Co2+-related signals in ultraviolet-visible (UV-vis) extinction spectra; nevertheless, a good linear range for detecting 1-6 mg/L Co2+ in 50 g/L Zn2+ solution is still acquired. The strong anti-interference toward other metal ions and the mechanism understanding for trace Co2+ detection in such a high-concentration Zn2+ solution are also revealed by systematic analysis techniques. The results extend the AgNPs as colorimetric sensors to industrial solutions, providing a new strategy for detecting trace-metal ions in industrial plants.

Mechanism Understanding for Size Regulation of Silver Nanowires Mediated by Halogen Ions.

The controllable preparation of silver nanowires (AgNWs) with a high aspect ratio is key for enabling their applications on a large scale. Herein, the aspect ratio regulation of AgNWs mediated by halogen ion composition in ethylene glycol system was systematically investigated and the size evolution mechanism is elaborately understood. The co-addition of Br- and Cl- results in AgNWs with the highest aspect ratio of 1031. The surface physicochemical analysis of AgNWs and the density functional theory calculations indicate that the co-addition of Br- and Cl- contributes to the much-enhanced preferential growth of the Ag(111) crystal plane. At the same time, when Cl- and Br- coexist in the solution, the growth of the Ag(100) crystal plane on the AgNWs was restrained compared with that in the single Cl- system. Resultantly, the enhanced growth of Ag(111) and the inhibited growth of Ag(100) contribute to the formation of AgNWs with a higher aspect ratio in the Cl-Br mixed solution. The results can provide new insights for understanding the morphology and size evolution during the AgNWs preparation in ethylene glycol system.

Efficient Coagulation Removal of Fluoride Using Lanthanum Salts: Distribution and Chemical Behavior of Fluorine.

La-loaded absorbents have been widely reported for fluoride removal due to the strong affinity of La3+ towards fluoride ion. Herein, chemical removal of fluoride from flue gas scrubbing wastewater using lanthanum salt is investigated. The retaining free F- concentration, phase composition and morphology of filtration residues, and the distribution of fluorine have been investigated using ion-selective electrode, analytical balance, scanning electron microscopy, and X-ray diffractor. The results show that at La/F molar ratio ≥1:3.05, the majority of fluorine exists as LaF x 3-x complexes, leading to the failure of fluoride removal. At 1:3.20 ≤ La/F molar ratio ≤1:3.10, the formation of LaF3 is facilitated. However, co-existing LaF x 3-x tends to absorb on the surface of LaF3 particles, leading to the formation of colloidal solution with large numbers of LaF3·LaF x 3-x suspended solids. At an optimized La/F molar ratio of 1:3.10, a fluoride removal of 97.86% is obtained with retaining fluorine concentration of 6.42 mg L-1. Considering the existing of positively charged LaF x 3-x and LaF3·LaF x 3-x , coagulation removal of fluoride is proposed and investigated using lanthanum salts and negatively charged SiO2·nH2O colloidal particles, which is in-situ provided via Na2SiO3 hydrolysis at pH near 5.5. At a La/F molar ratio of 1:3.00 and Na2SiO3 dose of 0.50 g L-1, a fluoride removal of 99.25% is obtained with retaining fluorine concentration of 2.24 mg L-1. When Na2SiO3 dose increases to 1.00 g L-1, the retaining fluorine concentration could be further reduced to 0.80 mg L-1.

Comparative Genomics Provides Insights into the Genetic Diversity and Evolution of the DPANN Superphylum.

DPANN is known as highly diverse, globally widespread, and mostly ectosymbiotic archaeal superphylum. However, this group of archaea was overlooked for a long time, and there were limited in-depth studies reported. In this investigation, 41 metagenome-assembled genomes (MAGs) belonging to the DPANN superphylum were recovered (18 MAGs had average nucleotide identity [ANI] values of <95% and a percentage of conserved proteins [POCP] of >50%, while 14 MAGs showed a POCP of <50%), which were analyzed comparatively with 515 other published DPANN genomes. Mismatches to known 16S rRNA gene primers were identified among 16S rRNA genes of DPANN archaea. Numbers of gene families lost (mostly related to energy and amino acid metabolism) were over three times greater than those gained in the evolution of DPANN archaea. Lateral gene transfer (LGT; ∼45.5% was cross-domain) had facilitated niche adaption of the DPANN archaea, ensuring a delicate equilibrium of streamlined genomes with efficient niche-adaptive strategies. For instance, LGT-derived cytochrome bd ubiquinol oxidase and arginine deiminase in the genomes of "Candidatus Micrarchaeota" could help them better adapt to aerobic acidic mine drainage habitats. In addition, most DPANN archaea acquired enzymes for biosynthesis of extracellular polymeric substances (EPS) and transketolase/transaldolase for the pentose phosphate pathway from Bacteria. IMPORTANCE The domain Archaea is a key research model for gaining insights into the origin and evolution of life, as well as the relevant biogeochemical processes. The discovery of nanosized DPANN archaea has overthrown many aspects of microbiology. However, the DPANN superphylum still contains a vast genetic novelty and diversity that need to be explored. Comprehensively comparative genomic analysis on the DPANN superphylum was performed in this study, with an attempt to illuminate its metabolic potential, ecological distribution and evolutionary history. Many interphylum differences within the DPANN superphylum were found. For example, Altiarchaeota had the biggest genome among DPANN phyla, possessing many pathways missing in other phyla, such as formaldehyde assimilation and the Wood-Ljungdahl pathway. In addition, LGT acted as an important force to provide DPANN archaeal genetic flexibility that permitted the occupation of diverse niches. This study has advanced our understanding of the diversity and genome evolution of archaea.

Insights into the Metabolism and Evolution of the Genus Acidiphilium, a Typical Acidophile in Acid Mine Drainage.

Here, we report three new Acidiphilium genomes, reclassified existing Acidiphilium species, and performed the first comparative genomic analysis on Acidiphilium in an attempt to address the metabolic potential, ecological functions, and evolutionary history of the genus Acidiphilium In the genomes of Acidiphilium, we found an abundant repertoire of horizontally transferred genes (HTGs) contributing to environmental adaption and metabolic expansion, including genes conferring photosynthesis (puf, puh), CO2 assimilation (rbc), capacity for methane metabolism (mmo, mdh, frm), nitrogen source utilization (nar, cyn, hmp), sulfur compound utilization (sox, psr, sqr), and multiple metal and osmotic stress resistance capacities (czc, cop, ect). Additionally, the predicted donors of horizontal gene transfer were present in a cooccurrence network of Acidiphilium Genome-scale positive selection analysis revealed that 15 genes contained adaptive mutations, most of which were multifunctional and played critical roles in the survival of extreme conditions. We proposed that Acidiphilium originated in mild conditions and adapted to extreme environments such as acidic mineral sites after the acquisition of many essential functions.IMPORTANCE Extremophiles, organisms that thrive in extreme environments, are key models for research on biological adaption. They can provide hints for the origin and evolution of life, as well as improve the understanding of biogeochemical cycling of elements. Extremely acidophilic bacteria such as Acidiphilium are widespread in acid mine drainage (AMD) systems, but the metabolic potential, ecological functions, and evolutionary history of this genus are still ambiguous. Here, we sequenced the genomes of three new Acidiphilium strains and performed comparative genomic analysis on this extremely acidophilic bacterial genus. We found in the genomes of Acidiphilium an abundant repertoire of horizontally transferred genes (HTGs) contributing to environmental adaption and metabolic ability expansion, as indicated by phylogenetic reconstruction and gene context comparison. This study has advanced our understanding of microbial evolution and biogeochemical cycling in extreme niches.

Correction to: Microbial synergy and stoichiometry in heap biooxidation of low-grade porphyry arsenic-bearing gold ore.

In the original publication the section heading "Classification of microorganisms" appearing above the sub-section "Air and liquid circulation in the heap" in page four is incorrect. The correct section heading should be read as "Results and discussion".

Microbial synergy and stoichiometry in heap biooxidation of low-grade porphyry arsenic-bearing gold ore.

Heap biooxidation method was used to evaluate the availability of Paodaoling gold ore in Anhui province, China. 15,000 tons of gold ores (≤ 10 mm in diameter) were bioxidized under mesophilic conditions. Under the synergistic effect of microbial community, arsenic and sulfur were oxidized by 42% and 38% after 80 days. Relatively, leaching of gold was improved from 36 to 78% after heap biooxidation. The sequencing results showed there were 28 operational taxonomic units identified the microbial community in the heap. The main genera were Acidithiobacillus, Ferroplasma, Acidiferrobacter and Nitrospira. According to stoichiometry, the content of microorganisms with various functions tended to be balanced. The biomass production rate was 10 g/s, the CO2 fixation rate was 18 g/s, and the oxygen consumption rate was 60 g/s. This study provides a good basis for the further design and application of heap biooxidation technology.

Molecular modelling and synthesis of a new collector O-butyl S-(1-chloroethyl)carbonodithioate for copper sulfide ore and its flotation behavior.

Based on the homology principle in advanced pharmaceutical chemistry, a new high efficiency and low toxicity collector, O-butyl S-(1-chloroethyl)carbonodithioate, was designed. By using molecular simulation technology, MS (Materials Studio) was used to build the molecular model of the collector. The molecular structure was relaxed and optimized. The process of interaction between reagent and mineral surface was simulated and the interaction energy of reagent and mineral surface was calculated by density functional theory (DFT). The interaction process of the new collector and butyl xanthate on the mineral surface and the interaction energy of these two reagents and mineral surface were compared. The molecular structure of the new collector was designed from the perspective of the difference of the interaction energy between the reagents and the mineral surface. According to the results of molecular design and modelling, the new collector was synthesized. The flotation tests of pure minerals and real ores were carried out to verify the new collector. The experimental results showed that the collector has the characteristics of low toxicity, high selectivity, moderate collecting ability and low cost, and it is more suitable for flotation of the complex and refractory copper sulfide with low grade and fine dissemination.

Comparative Genomic Analysis Reveals the Distribution, Organization, and Evolution of Metal Resistance Genes in the Genus Acidithiobacillus.

Members of the genus Acidithiobacillus, which can adapt to extremely high concentrations of heavy metals, are universally found at acid mine drainage (AMD) sites. Here, we performed a comparative genomic analysis of 37 strains within the genus Acidithiobacillus to answer the untouched questions as to the mechanisms and the evolutionary history of metal resistance genes in Acidithiobacillus spp. The results showed that the evolutionary history of metal resistance genes in Acidithiobacillus spp. involved a combination of gene gains and losses, horizontal gene transfer (HGT), and gene duplication. Phylogenetic analyses revealed that metal resistance genes in Acidithiobacillus spp. were acquired by early HGT events from species that shared habitats with Acidithiobacillus spp., such as Acidihalobacter, Thiobacillus, Acidiferrobacter, and Thiomonas species. Multicopper oxidase genes involved in copper detoxification were lost in iron-oxidizing Acidithiobacillus ferridurans, Acidithiobacillus ferrivorans, and Acidithiobacillus ferrooxidans and were replaced by rusticyanin genes during evolution. In addition, widespread purifying selection and the predicted high expression levels emphasized the indispensable roles of metal resistance genes in the ability of Acidithiobacillus spp. to adapt to harsh environments. Altogether, the results suggested that Acidithiobacillus spp. recruited and consolidated additional novel functionalities during the adaption to challenging environments via HGT, gene duplication, and purifying selection. This study sheds light on the distribution, organization, functionality, and complex evolutionary history of metal resistance genes in Acidithiobacillus spp.IMPORTANCE Horizontal gene transfer (HGT), natural selection, and gene duplication are three main engines that drive the adaptive evolution of microbial genomes. Previous studies indicated that HGT was a main adaptive mechanism in acidophiles to cope with heavy-metal-rich environments. However, evidences of HGT in Acidithiobacillus species in response to challenging metal-rich environments and the mechanisms addressing how metal resistance genes originated and evolved in Acidithiobacillus are still lacking. The findings of this study revealed a fascinating phenomenon of putative cross-phylum HGT, suggesting that Acidithiobacillus spp. recruited and consolidated additional novel functionalities during the adaption to challenging environments via HGT, gene duplication, and purifying selection. Altogether, the insights gained in this study have improved our understanding of the metal resistance strategies of Acidithiobacillus spp.

Preparation of MgAl-EDTA-LDH based electrospun nanofiber membrane and its adsorption properties of copper(II) from wastewater.

Adsorption is recognized as one of the most promising technologies applied to remove heavy metals from contaminated water. However, the adsorption efficiency often decreases because of the aggregation and loss of adsorbents. Herein, a novel adsorbent was synthesized by intercalation ethylenediaminetetraacetic acid (EDTA) into layered double hydroxides (LDH) and subsequent encapsulated into PAN polymer matrix using electrospinning. The synthesized electrospun nanofiber membrane (MgAl-EDTA-LDH@PAN) was found to combine the advantages of LDH@PAN nanofiber membrane (high surface area, easy to separate, free from aggregation and loss) and EDTA (powerful chelating agent). The adsorption performance of the MgAl-EDTA-LDH@PAN was evaluated using Cu(II) as target metals by varying experimental conditions such as pH, contact time, initial adsorbent dosage, and temperature. The maximum adsorption capacity of MgAl-EDTA-LDH@PAN was 120.77mg/g with the initial Cu(II) concentrations ranging from 0.6 to 40mg/L. MgAl-EDTA-LDH@PAN was also used in real industrial contaminated water treatment, and the final effluent was approximate to class-I criteria of the National Wastewater Discharge Standard of China. (GB 8978-1996). In addition, Cu K-edge XAS and XPS analyses were applied for unraveling the adsorptive performance of MgAl-EDTA-LDH@PAN by revealing the molecular-level mechanism of Cu(II) uptake.

[Isolation and identification of Sulfobacillus sp. strains and their application in pyrite bioleaching].

OBJECTIVE: The work aimed to isolate and culture the acidophilic and moderately thermophilic microorganisms for leaching the sulfide ore. METHODS: We enriched and incubated iron- or sulfur-oxidizing strains from muddy water of acuric hot spring utilizing ferrous irons or elemental sulfur as substrates. Then, we identified the strains by their morphological, physiological, biochemical properties and phylogenetic positions, and estimated their bioleaching potential according to their oxidation rate of pyrite. RESULTS: Two acidophilic, aerobic and facultative heterotrophic bacterial strains, Costa C and Costa E, were isolated from the samples of sulfuric hot springs of Costa Rica. Cells of the two strains were gram-positive, spore-forming and rod-shaped [(0.4 - 0.6) microm x (2.5 - 4.0) microm and (0.4 - 0.7) microm x (2.4 - 4.9) microm, respectively]. Strain Costa C grew at a temperature range of 30 degrees C - 55 degrees C and a pH range of 1.2 - 5.0, optimally at 50 degrees C and 2.8. Strain Costa E grew at a temperature range of 30 degrees C - 55 degrees C and at a pH range of 1.4 - 5.0, optimally at 40 degrees C and 2.8. Two strains could autotrophically grow on inorganic substrates such as ferrous irons, element sulfur and K2 S4 O6 and also could utilize organic substrates like yeast extract for heterotrophic growth. Phylogenetic analysis based on 16S rRNA gene sequences alignment demonstrated that the highest similarity between strain Costa C, Costa E and other species of the genus Sulfobacillus was above 99%. CONCLUSION: Based on morphological, physiological and biochemical analysis, Costa C and Costa E can be affiliated to the genus Sulfobacillus, for which the names Sulfobacillus sp. strain Costa C and Sulfobacillus sp. strain Costa E were proposed. Both strains could oxidize pyrite, and the oxidation rates arrived 63.0 mg/L x d and 56.8 mg/L x d, respectively.