Pyrometallurgical upgrading of PGM-rich leach residues from the Western Platinum Base Metals Refinery through roasting

The production of Platinum Group Metals (PGMs) normally entails the smelting of PGM flotation concentrates, converting of the furnace matte and removal of the bulk of the Ni, Cu, Co, S and Fe through atmospheric and pressure leaching in a base metals refinery to produce a PGM-rich concentrate. A number of impurities, mostly Se, Te, As, Bi, Os and Pb, are not removed significantly during the oxidising leach process in sulphuric acid media. In addition slag inclusions in matte leads to contamination of the PGM residues with silica, fayalite, magnetite and trevorite phases. Furthermore some Cu, Ni, Fe and S also remain. For this reason a typical Precious Metal Refinery (PMR) feed material contains less than 65% PGMs. The PMR is based on a chloride process and requires contaminants to be within narrow specification limits to prevent the formation of PGM residues that must be reprocessed or tolled, leading to poor first pass metal efficiencies and extending the duration of the production pipeline for efficient recovery. A process has been developed to significantly upgrade the BMR leach residues through pyrometallurgical processing, which include a multistep process of roasting under oxidising atmospheres, a two-step smelting process of the roasted calcine (with engineered slag chemistry and slag-refractory interactions) and subsequent atomisation of the molten alloy which can be fed as a slurry into the HCl/Cl2 dissolution reactors in the precious metals refinery. These pyrometallurgical steps upgrade the BMR residue from a 45–50% grade up to an alloy grade of ca. 90% PGMs, whilst removing the most deleterious elements with major process impacts on the PMR. This paper will focus primarily on the roasting step and it will investigate the thermochemical and mineralogical changes occurring during roasting. These changes were evaluated through a combination of thermochemical modelling and experimental investigation. The roasting step needs to be in an oxidative environment in order to achieve the vapourisation of Se, Te, As, Os and S. The speciation of PGMs and their vapourisation behaviour are presented, as well as the sensitivity of precious metals deportment to changes in roast conditions.http://www.elsevier.com/locate/minenghb2014ai201

The 'causes' of teenage pregnancy: review of South African research - Part 2

This article forms the second of a two-part series in which South African research on teenage pregnancy is reviewed. Part 1 of the series dealt with the consequences of teenage pregnancy; this paper reviews the 'causes' thereof. International literature is incorporated in the discussion by way of comparison. Contributory factors which have been investigated by South African researchers include: reproductive ignorance; the earlier occurrence of menarche; risktaking behaviour; psychological problems; peer influence; co-ercive sexual relations; dysfunctional family patterns; poor health services; socio-economic status; the breakdown of cultural traditions; and the cultural value placed on children. Preston-Whyte and colleagues present a revisionist argument, stating that early pregnancy may represent a rational life choice for certain adolescent women. The article is concluded with comments on methodological problems encountered in the South African research, and a discussion on the implications in terms of policy formulation

The parent?infant dyad and the construction of the subjective self

Developmental psychology and psychopathology has in the past been more concerned with the quality of self-representation than with the development of the subjective agency which underpins our experience of feeling, thought and action, a key function of mentalisation. This review begins by contrasting a Cartesian view of pre-wired introspective subjectivity with a constructionist model based on the assumption of an innate contingency detector which orients the infant towards aspects of the social world that react congruently and in a specifically cued informative manner that expresses and facilitates the assimilation of cultural knowledge. Research on the neural mechanisms associated with mentalisation and social influences on its development are reviewed. It is suggested that the infant focuses on the attachment figure as a source of reliable information about the world. The construction of the sense of a subjective self is then an aspect of acquiring knowledge about the world through the caregiver's pedagogical communicative displays which in this context focuses on the child's thoughts and feelings. We argue that a number of possible mechanisms, including complementary activation of attachment and mentalisation, the disruptive effect of maltreatment on parent-child communication, the biobehavioural overlap of cues for learning and cues for attachment, may have a role in ensuring that the quality of relationship with the caregiver influences the development of the child's experience of thoughts and feelings

The SARAO MeerKAT 1.3 GHz Galactic Plane Survey

We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251○ ≤l ≤ 358○ and 2○ ≤l ≤ 61○ at |b| ≤ 1 5). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8″ and a broadband RMS sensitivity of ∼10–20 μJy beam−1. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908–1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE H II region candidates are not true H II regions; and a large sample of previously undiscovered background H I galaxies in the Zone of Avoidance

The MeerKAT Galaxy Cluster Legacy Survey: I. Survey overview and highlights

Please abstract in the article.The South African Radio Astronomy Observatory (SARAO), the National Research Foundation (NRF), the National Radio Astronomy Observatory, US National Science Foundation, the South African Research Chairs Initiative of the DSI/NRF, the SARAO HCD programme, the South African Research Chairs Initiative of the Department of Science and Innovation.http://www.aanda.orghj2022Physic

Genetic diversity and population structure of Eritrean pepper (Capsicum species) as revealed by SSR markers

Pepper (Capsicum spp.) is one of the most important vegetable crops and the most widely used spice worldwide including Eritrea. Diversity studies are an essential step for crop breeding and improvement. Therefore, the objectives of the study were to determine the diversity and population structure of local Eritrean pepper collected from farmers and research institutions and to evaluate the relatedness of the Eritrean pepper with accessions obtained from five other countries. A total of 407 individual pepper plants from 150 seed samples were evaluated using 28 SSR markers. The results showed that varieties maintained in situ by farmers were heterogeneous. Diversity parameters indicated extensive genetic variation among the Eritrea genotypes. The 28 markers revealed a total of 352 alleles with an average of 13 alleles per marker. Mean Polymorphic Information Content was 0.62 and, mean Observed Heterozygosity was 0.41. The analysis of molecular variance showed only 10% variation was among populations, 30% among individuals within populations and 60% within individuals. This can be explained by the high mean number of effective migrants (2.25) that ranged from 1.01 to 10.45 among populations indicating movement of germplasm among farmers in different geographic and agro-ecological regions. A factor analysis, neighbour joining clustering and the model based clustering (Structure) classified the 407 individuals into 3 groups. However, in the model based clustering; increasing the number of populations to 4 (K=4 ) caused all non-Eritrean genotypes to fall in a separate cluster suggesting availability of potentially rich diversity within the Eritrean populations justified by the large number of private alleles observed

Infestation mechanisms of two woodborer species in the mangrove Sonneratia alba J. Smith in Kenya and co-occurring endophytic fungi

Insect damage on trees can severely affect the quality of timber, reduce the fecundity of the host and render it susceptible to fungal infestation and disease. Such pathology weakens or eventually kills the host. Infestation by two insect woodborer species (a moth and a beetle) is causing mortality of Sonneratia alba, a wide-ranging pioneer mangrove species of the Indo-Pacific. Establishing the infestation mechanism of the two insect woodborer species is an initial and essential step towards understanding their ecological role in the mangroves and in determining sustainable management priorities and options. Our main objectives were to investigate the infestation mechanism employed by the two insect woodborers which infest S. alba trees, to establish the occurrence of secondary infestation by endophytic fungi in the infested S. alba branches, and to explore a control management option to the woodborer infestation. We conducted an external inspection of infested branches in two large embayments in Kenya, Gazi Bay and Mida Creek, and by splitting infested branches we determined the respective internal infestation mechanisms. Infested wood samples from Gazi Bay and Mida Creek were incubated at 28±1°C for 3.5 days to establish the presence of fungi. A survey was conducted in both Gazi Bay and Mida Creek to ascertain the presence of ants on S. alba. The infestation characteristics of the two insect woodborer species were different. It took 6.8 months for the beetle to kill a branch of 150 cm.200 cm long. For the moth to kill a branch, it depended upon several factors including the contribution by multiple species, other than the moth infestation alone. A total of 15 endophytic fungal species were identified. Two ant species Oecophylla longipoda and a Pheidole sp. inhabited 62% and 69% respectively of sampled S. alba trees in Gazi Bay whereas only Pheidole sp. inhabited 17% of the sampled S. alba trees in Mida Creek. In summary, we have documented the time it takes each woodborer species to kill a branch, the infestation mechanism of the two insect woodborers, and we hypothesized on the role of two ant species. The presence of several different fungal species was ascertained, and we discussed their possible role in the infested wood. Our results cannot unambiguously associate the woodborers and identified fungi. We recommend further studies to investigate the presence or absence, and if present, the nature of fungi in the gut of the woodborers.SCOPUS: ar.jiiTSEinfo:eu-repo/semantics/publishe

Pyrometallurgical upgrading of PGM-rich leach residues from the Western Platinum base metals refinery through roasting

The production of Platinum Group Metals (PGMs) normally entails the smelting of PGM flotation concentrates, converting of the furnace matte and removal of the bulk of the Ni, Cu, Co, S and Fe through atmospheric and pressure leaching in a base metals refinery to produce a PGM-rich concentrate. A number of impurities, mostly Se, Te, As, Bi, Os and Pb, are not removed significantly during the oxidising leach process in sulphuric acid media. In addition slag inclusions in matte leads to contamination of the PGM residues with silica, fayalite, magnetite and trevorite phases. Furthermore some Cu, Ni, Fe and S also remain. For this reason a typical Precious Metal Refinery (PMR) feed material contains less than 65% PGMs. The PMR is based on a chloride process and requires contaminants to be within narrow specification limits to prevent the formation of PGM residues that must be reprocessed or tolled, leading to poor first pass metal efficiencies and extending the duration of the production pipeline for efficient recovery. A process has been developed to significantly upgrade the BMR leach residues through pyrometallurgical processing, which include a multistep process of roasting under oxidising atmospheres, a two-step smelting process of the roasted calcine (with engineered slag chemistry and slag-refractory interactions) and subsequent atomisation of the molten alloy which can be fed as a slurry into the HCl/Cl2 dissolution reactors in the precious metals refinery. These pyrometallurgical steps upgrade the BMR residue from a 45–50% grade up to an alloy grade of ca. 90% PGMs, whilst removing the most deleterious elements with major process impacts on the PMR.This paper will focus primarily on the roasting step and it will investigate the thermochemical and mineralogical changes occurring during roasting. These changes were evaluated through a combination of thermochemical modelling and experimental investigation. The roasting step needs to be in an oxidative environment in order to achieve the vapourisation of Se, Te, As, Os and S. The speciation of PGMs and their vapourisation behaviour are presented, as well as the sensitivity of precious metals deportment to changes in roast conditions