Re‐using bauxite residues: benefits beyond (critical raw) material recovery

Since the world economy has been confronted with an increasing risk of supply shortages of critical raw materials (CRMs), there has been a major interest in identifying alternative secondary sources of CRMs. Bauxite residues from alumina production are available at a multi‐million tonnes scale worldwide. So far, attempts have been made to find alternative re‐use applications for bauxite residues, for instance in cement / pig iron production. However, bauxite residues also constitute an untapped secondary source of CRMs. Depending on their geological origin and processing protocol, bauxite residues can contain considerable amounts of valuable elements. The obvious primary consideration for CRM recovery from such residues is the economic value of the materials contained. However, there are further benefits from re‐use of bauxite residues in general, and from CRM recovery in particular. These go beyond monetary values (e.g. reduced investment / operational costs resulting from savings in disposal). For instance, benefits for the environment and health can be achieved by abatement of tailing storage as well as by reduction of emissions from conventional primary mining. Whereas certain tools (e.g. life‐cycle analysis) can be used to quantify the latter, other benefits (in particular sustained social and technological development) are harder to quantify. This review evaluates strategies of bauxite residue re‐use / recycling and identifies associated benefits beyond elemental recovery. Furthermore, methodologies to translate risks and benefits into quantifiable data are discussed. Ultimately, such quantitative data are a prerequisite for facilitating decision‐making regarding bauxite residue re‐use / recycling and a stepping stone towards developing a zero‐waste alumina production process. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Thermoelectric properties of silicon at high pressures in the region of the semiconductor-metal transition

The thermo emf in Czochralski grown silicon single crystals annealed at 450°C was experimentally studied in a range of pressures up to 16 GPa in a chamber with synthetic diamond anvils. There is a correlation between the curves of thermo emf versus pressure, the semiconductor-metal transition pressure, and the mechanical properties (microhardness, compressibility) of samples with various oxygen content. The values of thermo emf in the high-pressure metallic phases have been determined.     

The corroding action of zirconium tetrachloride vapors on 1Khl8N9T steel and nickel at high temperatures

We found that the corrosion resistance of lKh18N9T steel in an atmosphere of zirconium tetrachloride vapors decreases with increase in temperature and pressure of the ZrCl₄ vapors. The corrosion of lKh18N9T steel proceeds uniformly but that of nickel obeys a logarithmic law, which points to the formation of a protective film of nickel chloride on the surface of the metal.     

Use of radioactive catalysts for dehydrating alcohols

The authors show that catalytic processes can be influenced by radioactive radiation. The addition of radioactive material to a catalyst greatly changes the velocity and apparent activation energy of the process, and sometimes changes the direction of a heterogeneouscatalytic reaction. It is shown that radioactive radiations produce qualitative changes in the catalyst and have a marked effect on the adsorbed layer of molecules on the catalyst surface which become polarized, the degree of polarization depending on the structure of the reacting molecule.Translated from Atomnaya Énergiya, Vol. 21, No. 4, pp. 277–281, October, 1966.     

β-Tricalcium phosphate silica aerogel as an alternative bioactive ceramic for the potential use in dentistry

ABSTRACT

In this study, a mesoporous silica aerogel with β-tricalcium phosphate (β-TCP-AE) was manufactured. The effect of β-TCP-AE on gene expressions (BMP2, BMP7, Runx2 and OSX) of SAOS-2 cells was tested. For the in vivo evaluation, the ‘calvaria critical-size defect’ model was used: following 1 and 3 months of the artificial surgical bone defects filled with β-TCP-AE, histopathological analyses were performed. Gene expression studies demonstrated a mild osteoblastic differentiation of the SAOS-2 cells triggered after seven days of β-TCP-AE treatment. Digital histology of rat’s calvarial bone defects reconstructed with β-TCP-AE showed that after 1 month, calcifications and early ossifications developed with the presence of capillary-rich fibrous inflammation and remnants of exogenous compounds which nearly disappeared by the third month, and replaced with multiple newly formed bone islets mediated by osteoblasts. Based on our results, this bioceramic compound appears to have favourable properties for the use as a scaffold in the reconstructive medical practice.     

Novel amino acid-based polymers for pharmaceutical applications

Summary Entirely amino acid-based polymers were prepared by side-chain attachment to polysuccinimide derived from the thermal polycondensation of aspartic acid. Following deprotonation of various amino acid ester hydrochlorides by a secondary amine, the restored primary amino groups initiated the ring-opening of succinimide to form amide bonds. ¹H and ¹³C NMR measurements revealed that the mole fraction of the introduced amino acid side chains could be controlled by the reaction time, while no hydrolysis of methyl ester groups was observed. The synthesized polymers contain exclusively amino acids, which makes them promising candidates as base materials of controlled drug delivery systems.     

Growing and stability of gold nanoparticles and their functionalization by cysteine

Gold nanoparticles in aqueous dispersion were prepared using the trisodium citrate reduction method to control the size of particles by changing the concentration of HAuCl₄. The average particle size measured by DLS is higher than that obtained by TEM at a zeta potential of -40 mV. When trisodium citrate concentration is kept constant, the particle size increases with gold concentration. The kinetics of growth was studied and apparent kinetic rate constants were determined at various gold/citrate ratios. Gold nanoparticles were attached to silanized glass surfaces; Au rods were grown (ca. 200 nm) by adding more precursors and the rods’ growth rate was monitored by UV-Vis spectroscopy as well as by AFM. Surface functionalization of gold surface was influenced by cysteine. The surface modification by cysteine at pH=6.0 results in aggregation and the red shift of absorption maximum is nearly 200 nm. When glutathione molecules are bound onto the cysteinelinked Au rods on the glass surface, the spectral shift reaches only an amount of 5–10 nm, because the surface attachment hinders the tendency to aggregate.     

Radiosynthesis and Preclinical Investigation of 11C-Labelled 3-(4,5-Diphenyl-1,3-oxazol-2-yl)propanal Oxime ([11C]SZV 1287)

The radiosynthesis, as well as the in vivo and ex vivo biodistribution of the ¹¹C radiolabelled 3-(4,5-diphenyl-1,3-oxazol-2-yl)propanal oxime ( 6 , [¹¹C]SZV 1287) are reported. SZV 1287 is a novel semicarbazide-sensitive amine oxidase (SSAO) inhibitor and a promising candidate to be a novel analgesic for the treatment of neuropathic pain. Its radiolabelling was developed via a four-step radiosynthesis which started from the reaction of a Grignard reagent with [¹¹C]CO₂ to produce [¹¹C]oxaprozin ( 3 ). In the next step this carboxylic acid 3 was directly reduced to yield the corresponding aldehyde, which was then converted into the oxime. [¹¹C]SZV 1287 was administered to male NMRI mice. The animals were examined with dynamic PET/MR imaging for 90 minutes. Biodistribution studies were performed at 10, 30, 60 and 120 minutes post injection. The accumulation of the labelled compound was observed in the brain of the animals. The main excretion pathway was found to be through the liver and intestines. These studies provide preliminary information for pharmacokinetic characterization of the SZV 1287.