Precipitation of rhodium from a copper sulphate leach solution in the selenium/tellurium removal section of a base metal refinery

Copper sulphate solutions are produced during the pressure leaching of first-stage leach residue in a typical base metal refinery process. Apart from impurities such as selenium and tellurium, this leach solution also contains other precious metals (Rh, Ru, and Ir) due to dissolution in the pressure leaching stage. Selenium and tellurium are removed from the leach solution by precipitation with sulphurous acid, since these elements negatively affect electrowinning. This study investigates the feasibility of modifying the Se/Te precipitation process step to achieve significant rhodium precipitation in addition to selenium and tellurium precipitation, in order to reduce the rhodium inventory of the process. Thiourea, SO2, formaldehyde, formic acid, and sodium thiosulphate were evaluated to determine which of these reagents would achieve the highest Rh precipitation. Based on these screening tests, SO2 and thiourea were selected to be used as precipitation reagents in optimization tests. During these optimization tests, the operating temperature (80 to 150°C) and the amount of reagent added (80 to 140 per cent excess) were varied to evaluate the effects that these operating conditions have on the precipitation behaviour of Rh as well as Se, Te, Cu, and Ni, and to propose appropriate operating conditions. It was found that thiourea resulted in good Rh and Se precipitation (typically in excess of 90 per cent), but precipitated noticeably more copper and nickel from the solution than when SO2 was used. In addition, thiourea had poor Te removal characteristics. SO2 achieved a maximum of 70 per cent precipitation of the rhodium. Faster kinetics and a larger extent of Te precipitation were, however, observed when using SO2 compared to thiourea

Dekonstruksie en Bybelse hermeneutiek

Deconstruction and biblical hermeneutics The purpose of this article is to evaluate deconstruction as a postmodern philosophical viewpoint in relation to biblical hermeneutics as a theological interpretation method. A short exposition of postmodernity is given to emphasise deconstruction’s aim of deconstructing traditional views on texts and metaphysics. This leads to intertextual reading which is in opposition to the textual reading of biblical hermeneutics. The consequences of deconstruction are finally evaluated in relation to the methods of Redaktionsgeschichte and the historische Jesus Forschung

TEACHER LEARNING IN CONTEXTS OF POLICY IMPLEMENTATION

Teacher education needs to be viewed as a continuum that begins with pre-service learning, followed by teacher induction, and then the continuing professional development (CPD) of teachers. To date researchers know much less about teacher induction relative to the other two phases of teacher education, in part because of its informal nature in most schools. Ethiopia is one of few exceptions in the world that has recently introduced an institutionalised and formal multi-year programme of induction for beginning teachers. This paper examines the organisation and practice of teacher induction in Ethiopia by exploring the experiences of three first year primary school teachers. Our findings suggest that while the structure and organisation of the mentoring programme are similar across schools, the professional guidance and assistance that is offered to the first year teachers varies greatly depending on a number of factors. We conclude with a discussion of the need to re-examine the conditions of implementations of the induction programme. Without proper resources, mentors, time allocated, and regular on-site monitoring, the formal teacher induction programme is unlikely to realise its intended benefits of supporting beginning teachers with adequate subject knowledge and skills required for quality teaching in the schools

Difference in blood pressure response to ACE-Inhibitor monotherapy between black and white adults with arterial hypertension: a meta-analysis of 13 clinical trials.

BACKGROUND: Among African-Americans adults, arterial hypertension is both more prevalent and associated with more complications than among white adults. Hypertension is also epidemic among black adults in sub-Saharan Africa. The treatment of hypertension among black adults may be complicated by lesser response to certain classes of anti-hypertensive agents. METHODS: We systematically searched literature for clinical trials of ACE-inhibitors among hypertensive adults comparing blood pressure response between whites and blacks. Meta-analysis was performed to determine the difference in systolic and diastolic blood pressure response. Further analysis including meta-regressions, funnel plots, and one-study-removed analyses were performed to investigate possible sources of heterogeneity or bias. RESULTS: In a meta-analysis of 13 trials providing 17 different patient groups for evaluation, black race was associated with a lesser reduction in systolic (mean difference: 4.6 mmHg (95% CI 3.5-5.7)) and diastolic (mean difference: 2.8 mmHg (95% CI 2.2-3.5)) blood pressure response to ACE-inhibitors, with little heterogeneity. Meta-regression revealed only ACE-inhibitor dosage as a significant source of heterogeneity. There was little evidence of publication bias. CONCLUSIONS: Black race is consistently associated with a clinically significant lesser reduction in both systolic and diastolic blood pressure to ACE-inhibitor therapy in clinical trials in the USA and Europe. In black adults requiring monotherapy for uncomplicated hypertension, drugs other than ACE-inhibitors may be preferred, though the proven benefits of ACE-inhibitors in some sub-groups and the large overlap of response between blacks and whites must be remembered. These data are particularly important for interpretation of clinical drug trials for hypertensive black adults in sub-Saharan Africa and for the development of treatment recommendations in this population

Case management reduces drinking during pregnancy among high-risk women

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