scholarly journals The sensitivity of the ice-nucleating ability of minerals to heat and the implications for the heat test for biological ice nucleators

2021 ◽  
Author(s):  
Martin Ian Daily ◽  
Mark Duncan Tarn ◽  
Thomas Francis Whale ◽  
Benjamin John Murray
Keyword(s):  
Active Sites ◽  
Radiative Properties ◽  
Mineral Particle ◽  
Mineral Surfaces ◽  
Organic Contamination ◽  
Biological Origin ◽  
Dry Heat ◽  
Before And After ◽  
Ice Nucleators ◽  
Wet Heat

Abstract. Ice-nucleating particles (INPs) are atmospheric aerosol particles that can strongly influence the radiative properties and precipitation onset in mixed-phase clouds by triggering ice formation in supercooled cloud water droplets. The ability to distinguish between INPs of mineral and biological origin in samples collected from the environment is needed to better understand their distribution and sources, but this is challenging. A common method for assessing the relative contributions of mineral and biogenic INPs in samples collected from the environment (e.g., aerosol, rainwater, soil) is to determine the ice-nucleating ability (INA) before and after heating, where heat is expected to denature proteins associated with biological ice nucleants. The key assumption is that the ice nucleation sites of biological origin are denatured by heat, while those associated with mineral surfaces remain unaffected; we test this assumption here. We exposed atmospherically relevant mineral samples to wet heat (INP suspensions warmed to above 90 °C) or dry heat (dry samples heated to 250 °C) and assessed the effects on their immersion mode INA using a droplet freezing assay. K-feldspar, thought to be the dominant mineral-based atmospheric INP type where present, was not significantly affected by wet heating, while quartz, plagioclase feldspars and Arizona test Dust (ATD) lost INA when heated in this mode. We argue that these reductions in INA in the aqueous phase result from direct alteration of the mineral particle surfaces by heat treatment rather than from biological or organic contamination. We hypothesise that degradation of active sites by dissolution of mineral surfaces is the mechanism in all cases due to the correlation between mineral INA deactivation magnitudes and their dissolution rates. Dry heating produced minor but repeatable deactivations in K-feldspar particles but was generally less likely to deactivate minerals compared to wet heating. We also heat tested proteinaceous and non-proteinaceous biogenic INP proxy materials and found that non-proteinaceous samples (cellulose and pollen) were relatively heat resistant. In contrast, the proteinaceous ice-nucleating samples were highly sensitive to wet and dry heat, as expected, although their activity remained non-negligible after heating. We conclude that, while INP heat tests have the potential to produce false positives, i.e., deactivation of a mineral INA that could be misconstrued as the presence of biogenic INPs, they are still a valid method for qualitatively detecting proteinaceous biogenic INP in ambient samples, so long as the mineral-based INA is controlled by K-feldspar.

scholarly journals Effect of pedogenic iron-oxyhydroxide removal on the metal sorption by soil clay minerals

2021 ◽  
Vol 21 (4) ◽  
pp. 1785-1799
Author(s):  
Péter Sipos ◽  
Viktória Kovács Kis ◽  
Réka Balázs ◽  
Adrienn Tóth ◽  
Tibor Németh
Keyword(s):  
Clay Minerals ◽  
Close Association ◽  
Direct Analysis ◽  
Alkaline Soil ◽  
Mineral Surfaces ◽  
Iron Oxyhydroxide ◽  
Metal Sorption ◽  
Before And After ◽  
Fe Oxyhydroxides ◽  
Cu And Zn

Abstract Purpose The close association of Fe-oxyhydroxides and clay minerals might influence the sorption properties of these components. We aimed to study the effect of removing the pedogenic Fe-oxyhydroxides on the sorption of Cd, Cu, Pb, and Zn by the clay mineral particles in soils with contrasting pH. Methods Competitive batch sorption experiments before and after Fe-oxyhydroxide extraction in soils were carried out together with the direct analysis of the metal sorption on individual particles of ferrihydrite, smectite, and illite/smectite by TEM. Results Ferrihydrite was a more effective metal sorbent than clay minerals, although its removal resulted in decreased sorption only for Cd, Cu, and Zn. Ferrhydrite coating blocked metals’ access for certain sorption sites on clay surfaces, which were only accessible for Pb as the most efficient competitor after removing the coating. This observation was the most remarkable for the smectite particles in the alkaline soil. Mineral surfaces sorbed higher Cu than Pb concentrations and higher Zn than Cd concentrations despite the former metals’ lower bulk sorption. Thus, organic surfaces and precipitation contributed to Pb and Cd’s retention to a greater extent than for Cu and Zn. The structural Fe of smectite also promoted the metal sorption in both soils. Conclusion Removal of iron-oxyhydroxide coatings from the soil affects metal sorption selectively. Direct study of metal sorption on individual soil particles enables us to gain a more in-depth insight into soil minerals’ role in this process.

Influence of particle size on copper recovery from sulfide ore by the moderately thermophilic microorganisms

2019 ◽  
Vol 116 (1) ◽  
pp. 119
Author(s):  
Wen-bo Zhou ◽  
Kai Li ◽  
Yu-guang Wang ◽  
Li-juan Zhang ◽  
Hai-na Cheng ◽  
...  
Keyword(s):  
Particle Size ◽  
Xrd Analysis ◽  
Microbial Interactions ◽  
Copper Recovery ◽  
Mineral Particle ◽  
Copper Ore ◽  
Thermophilic Microorganisms ◽  
Moderately Thermophilic ◽  
Before And After ◽  
Leaching Condition

The bioleaching of copper ore by the defined moderately thermophilic consortium containing Leptospirillum ferriphilum and Acidithiobacillus caldus was carried out in the bench-scale column. Bioleaching experiments showed that the leaching rate was 25% higher than that of a conventional leaching and the acid consumption was reduced by 33% at the optimal leaching condition. Meanwhile, the effect of different particle sizes on the rate of the copper leaching was also investigated, and it was shown that the particle size affects the bioleaching rate significantly in the range of 5–25 mm, in which approximately 89.27% of copper was extracted at 5–10 mm, while only 57.08% at 15–25 mm. The results obtained by X-ray diffraction (XRD) analysis of the mineral samples before and after microbial and chemical leaching revealed that the decrease in particle size of the minerals resulted in an enhancement of complex microbial interactions. Especially for the particle size of 5–10 mm, a significant amount of elemental sulfur and jarosite formed on the surface of the mineral, while it was further confirmed that critical microbe-mineral interactions have taken place on the mineral surface. The results indicated that mineral particle size is an integral factor to improve the copper recovery from ore in heap leaching operation. This will provide a reference to the heap construction for the bioleaching.

scholarly journals Uptake of Cationic Dyes by Cement Kiln Dust: Sorption Mechanism and Equilibrium Isotherm

2002 ◽  
Vol 20 (7) ◽  
pp. 657-668 ◽  
Author(s):  
Mamdouh M. Nassar ◽  
Abd. El Hakim A. Daifullah ◽  
Yehia H. Magdy ◽  
Ebrahiem E. Ebrahiem
Keyword(s):  
Sodium Silicate ◽  
Active Sites ◽  
Freundlich Isotherm ◽  
Cement Kiln Dust ◽  
Cement Kiln ◽  
X Ray Diffraction ◽  
Exchange Reactions ◽  
Sorptive Capacity ◽  
Before And After ◽  
Kiln Dust

The mechanistic aspects of the sorption of Basic Blue-3 and Basic Red-22 on to cement kiln dust (CKD) have been investigated. The by-pass kiln dust before and after washing with water was characterized by X-ray diffraction methods, IR spectroscopy and elemental analysis. Two forms of by-pass kiln dust were used in this study without any treatment, i.e. in powder and pelletized form (the latter being achieved using water or sodium silicate). Equilibrium isotherms to assess the maximum capacity of the two basic dyes on the two forms of CKD were evaluated using a computer program. This allowed two-, three- and four-parameter adsorption models to be studied; it was found that the piecewise Freundlich isotherm yielded an excellent overall fit. Washing with water led to the loss of some active sites responsible for the sorptive capacity. The increase in capacity observed after pelletization with water rather than with sodium silicate could be explained by an increase in hydroxy moieties that undergo exchange reactions. In both cases of pelletization, the adsorption capacity was less than for the unwashed powdered form. The uptake order was found to be: unwashed powder > pellets with water > pellets with sodium silicate.

ELIMINATION AND SEPARATION OF VIRUSES IN APPLE CLONES BY EXPOSURE TO DRY HEAT

1965 ◽  
Vol 45 (5) ◽  
pp. 443-454 ◽  
Author(s):  
Maurice F. Welsh ◽  
George Nyland
Keyword(s):  
Heat Exposure ◽  
Exposure Period ◽  
Virus Infections ◽  
Maximum Heat ◽  
Dry Heat ◽  
Lateral Buds ◽  
Before And After ◽  
Accurate Forecast ◽  
Minimum Heat ◽  
Stem Pitting

Virus infections have been eliminated from apple clones by propagation of lateral buds from potted apple trees after their exposure to dry heat at 38 °C for varying periods. For several clones the minimum heat exposure period imposed (7 days, following preheating 7 days at 35 °C) inactivated viruses that cause stem pitting of Virginia crab; foliage and shoot symptoms on Hopa crab; rubbery wood on Lord Lambourne apple; foliage and dieback symptoms on Spartan apple (McIntosh pucker virus); and leaf pattern, epinasty, and bark necrosis of Spy 227.The apple clones displayed wide differences in heat tolerance. Minimum heat exposure periods for virus inactivation varied among clones treated. For two clones, the buds sampled after maximum heat exposure periods, approaching survival threshold of the plants, gave higher levels of positive indexing on Spy 227, Hopa crab, and Virginia crab than those sampled after short or intermediate periods. Virginia crab stem pitting and Virginia crab decline were shown to have distinct etiology: the virus causing stem pitting proved very sensitive to heat, whereas that causing decline was heat-tolerant. Indexing before and after heat exposure provided evidence that distinct viruses or strains induce the reactions of Hopa crab and Spy 227, Hopa crab and Virginia crab, and probably also Virginia crab and Spy 227.Indexing of internodal bark chips at the time buds were removed from the heat chamber for propagation yielded readings quickly and provided a generally accurate forecast of the indexing results for trees derived from the treated buds.

scholarly journals Nanoscale Structural and Mechanical Analysis of Bacillus anthracis Spores Inactivated with Rapid Dry Heating

2013 ◽  
Vol 80 (5) ◽  
pp. 1739-1749 ◽  
Author(s):  
Yun Xing ◽  
Alex Li ◽  
Daniel L. Felker ◽  
Larry W. Burggraf
Keyword(s):  
High Temperature ◽  
Bacillus Anthracis ◽  
Exposure Time ◽  
Mechanical Analysis ◽  
Mechanical Stresses ◽  
Heat Inactivation ◽  
Content Type ◽  
Dry Heat ◽  
Wet Heat ◽  
Dry Heating

ABSTRACTEffective killing ofBacillus anthracisspores is of paramount importance to antibioterrorism, food safety, environmental protection, and the medical device industry. Thus, a deeper understanding of the mechanisms of spore resistance and inactivation is highly desired for developing new strategies or improving the known methods for spore destruction. Previous studies have shown that spore inactivation mechanisms differ considerably depending upon the killing agents, such as heat (wet heat, dry heat), UV, ionizing radiation, and chemicals. It is believed that wet heat kills spores by inactivating critical enzymes, while dry heat kills spores by damaging their DNA. Many studies have focused on the biochemical aspects of spore inactivation by dry heat; few have investigated structural damages and changes in spore mechanical properties. In this study, we have inactivatedBacillus anthracisspores with rapid dry heating and performed nanoscale topographical and mechanical analysis of inactivated spores using atomic force microscopy (AFM). Our results revealed significant changes in spore morphology and nanomechanical properties after heat inactivation. In addition, we also found that these changes were different under different heating conditions that produced similar inactivation probabilities (high temperature for short exposure time versus low temperature for long exposure time). We attributed the differences to the differential thermal and mechanical stresses in the spore. The buildup of internal thermal and mechanical stresses may become prominent only in ultrafast, high-temperature heat inactivation when the experimental timescale is too short for heat-generated vapor to efficiently escape from the spore. Our results thus provide direct, visual evidences of the importance of thermal stresses and heat and mass transfer to spore inactivation by very rapid dry heating.

scholarly journals Dynamics and fragmentation mechanism of (C5H4CH3)Pt(CH3)3 on SiO2 surfaces

2018 ◽  
Vol 9 ◽  
pp. 711-720 ◽  
Author(s):  
Kaliappan Muthukumar ◽  
Harald O Jeschke ◽  
Roser Valentí
Keyword(s):  
Electron Beam ◽  
Active Sites ◽  
Density Functional ◽  
Fragmentation Mechanism ◽  
Functional Theory ◽  
Before And After ◽  
Surface Active ◽  
Dynamics Simulations ◽  
Precursor Molecules

The interaction of trimethyl(methylcyclopentadienyl)platinum(IV) ((C5H4CH3)Pt(CH3)3) molecules on fully and partially hydroxylated SiO2 surfaces, as well as the dynamics of this interaction were investigated using density functional theory (DFT) and finite temperature DFT-based molecular dynamics simulations. Fully and partially hydroxylated surfaces represent substrates before and after electron beam treatment and this study examines the role of electron beam pretreatment on the substrates in the initial stages of precursor dissociation and formation of Pt deposits. Our simulations show that on fully hydroxylated surfaces or untreated surfaces, the precursor molecules remain inactivated while we observe fragmentation of (C5H4CH3)Pt(CH3)3 on partially hydroxylated surfaces. The behavior of precursor molecules on the partially hydroxylated surfaces has been found to depend on the initial orientation of the molecule and the distribution of surface active sites. Based on the observations from the simulations and available experiments, we discuss possible dissociation channels of the precursor.

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