Thermochemical purification of talc with ammonium sulphate as chemical additive

This study reports on the thermochemical reactivity of talc with ammonium sulphate, a low-cost, recyclable chemical additive commonly used in the thermochemical extraction of strategic metals from low-grade ores and industrial and mine residues. The talc sample used in this study contained 70% talc, 15% lizardite and 10% kaolinite, following the removal of carbonate minerals by HCl leaching as a pre-concentration step. The solid product obtained by thermochemical treatment followed by aqueous leaching contained high-grade purified talc (>98%) as the principal mineral phase. It was depleted of lizardite and kaolinite, which had reacted with ammonium sulphate to form water-soluble hydrated ammonium metal sulphates. A comparative analysis of the TGA profiles of the concentrated parent sample, the solid product and the solid residue highlighted an identical mass loss between 850 °C and 1000 °C, which is the temperature range at which the dehydroxylation of talc occurs. This indicated minimal, if any, structural denaturation of the talc phase following thermochemical treatment with ammonium sulphate under the experimental condition studied. This process may therefore represent a promising technology for the purification of talc under the right market conditions, provided the mineral co-exists with phases featuring a high degree of reactivity with ammonium sulphate under thermal conditions.The University of Pretoria and the National Research Foundation of South Africa.http://www.elsevier.com/locate/mineng2022-02-19hj2021Chemistr

Comparison of CO2 capture by ex-situ accelerated carbonation and in in-situ naturally weathered coal fly ash

Natural weathering at coal power plants ash dams occurs via processes such as carbonation, dissolution, co-precipitation and fluid transport mechanisms which are responsible for the long-term chemical, physical and geochemical changes in the ash. Very little information is available on the natural carbon capture potential of wet or dry ash dams. This study investigated the extent of carbon capture in a wet-dumped ash dam and the mineralogical changes promoting CO2 capture, comparing this natural phenomenon with accelerated ex-situ mineral carbonation of fresh fly ash (FA). Significant levels of trace elements of Sr, Ba and Zr were present in both fresh and weathered ash. However Nb, Y, Sr, Th and Ba were found to be enriched in weathered ash compared to fresh ash. Mineralogically, fresh ash is made up of quartz, mullite, hematite, magnetite and lime while weathered and carbonated ashes contained additional phases such as calcite and aragonite. Up to 6.5 wt % CO2 was captured by the fresh FA with a 60% conversion of calcium to CaCO3 via accelerated carbonation (carried out at 2 h, 4Mpa, 90 o C, bulk ash and a S/L ratio of 1). On the other hand 6.8 wt % CO2 was found to have been captured by natural carbonation over a period of 20 years of wet disposed ash. Thus natural carbonation in the ash dumps is significant and may be effective in capturing CO2.Web of Scienc

Preparation of sodium silicate solutions and silica nanoparticles from South African coal fly ash

Please read abstract in the article.UNISA, University of Pretoria, Council for Geoscience, and the National Research Foundation of South Africa (NRF; Grant No.93641).https://link.springer.com/journal/126492020-06-20hj2020Chemistr

Predicting in vivo starch digestibility coefficients in newly weaned piglets from in vitro assessment of diets using multivariate analysis.

The study was based on correlating a dataset of in vivo mean starch digestibility coefficients obtained in the immediate post-weaning phase of piglets with a range of dietary in vitro variables. The paper presents a model that predicts (R2 0·71) in vivo average starch digestibility coefficients in the 0·5 small-intestinal region of newly weaned piglets fed cereal-based diets using seven in vitro variables describing starch properties that are fundamentally associated with the quality of feed materials, i.e. hydration, structure and amylolytic digestion. The variables were: Rapid Visco Analyser (RVA; measures the viscosity of materials when sheared under defined hydration and temperature regimens); RVA end viscosity; RVA (gelatinisation) peak viscosity; ΔH (gelatinisation enthalpy that provides an estimate of helical order or degree of crystallinity in starch); water solubility index (WSI; that denotes the amount of soluble polysaccharides released from starch granules to the aqueous phase); grain endogenous amylase (concentration of endogenous α-amylase in cereals, assessed by pasting cereal flours in 25 g of AgNO3, an amylase inhibitor v. water using RVA)

A novel function for the Caenorhabditis elegans

Torsin proteins are AAA+ ATPases that localize to the endoplasmic reticular/nuclear envelope (ER/NE) lumen. A mutation that markedly impairs torsinA function causes the CNS disorder DYT1 dystonia. Abnormalities of NE membranes have been linked to torsinA loss of function and the pathogenesis of DYT1 dystonia, leading us to investigate the role of the Caenorhabditis elegans torsinA homologue OOC-5 at the NE. We report a novel role for torsin in nuclear pore biology. In ooc-5–mutant germ cell nuclei, nucleoporins (Nups) were mislocalized in large plaques beginning at meiotic entry and persisted throughout meiosis. Moreover, the KASH protein ZYG-12 was mislocalized in ooc-5 gonads. Nups were mislocalized in adult intestinal nuclei and in embryos from mutant mothers. EM analysis revealed vesicle-like structures in the perinuclear space of intestinal and germ cell nuclei, similar to defects reported in torsin-mutant flies and mice. Consistent with a functional disruption of Nups, ooc-5–mutant embryos displayed impaired nuclear import kinetics, although the nuclear pore-size exclusion barrier was maintained. Our data are the first to demonstrate a requirement for a torsin for normal Nup localization and function and suggest that these functions are likely conserved