The Adsorption and Elution of Platinum Group Metals (Pt, Pd, and Au) from Cyanide Leach Solutions using Activated Carbon

This paper investigates the recovery of platinum group metals (PGMs) from a dilute cyanide leach solution containing base metals, in a manner similar to that used for gold extraction in a typical CIP process, and focuses on both the adsorption and elution stages. The carrier-phase extraction of precious metals using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs. As a sorbent, activated carbon is still by far the most important material because of its large surface area, high adsorption capacity, porous structure, negligible environmental toxicity, low cost, and high purity standards. Adsorption tests were performed on a pregnant alkaline leach solution (0.15 ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) resulting from cyanide extraction performed in column leach tests. The initial adsorption rates of platinum, palladium, and gold were very fast and recoveries of these three metals were approximately 90 per cent after 2 hours and 100 per cent, 97.4 per cent, and 99.9 per cent respectively after 72 hours. The parameters that influence the extraction of PGMs and Au were examined to assess their relative importance during the adsorption process in order to provide the basis for process optimization. The concentration of thiocyanate was not identified as significant factor for PGMs adsorption, while nickel concentration was the most significant extraction process parameter. Base metal cyanide complexes adsorb and compete with the PGM complexes for sites on activated carbon, and while copper adsorption can be minimized by adjusting the residence time, nickel adsorbs at approximately the same rate as that of the PGMs, influencing the loading capacity and adsorption kinetics of the PGMs.The feasibility of eluting platinum and palladium cyanide complexes from activated carbon using an analogue of the AARL process was investigated. Platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold still to be eluted after 16 bed volumes. Cyanide pre-treatment was found to have a significant influence on PGM elution. Higher cyanide concentration in the pre-treatment step results in more efficient elution up to a point, and experiments suggest the possibility of an optimum cyanide concentration, beyond which elution efficiency starts decreasing

The application of activated carbon for the adsorption and elution of platinum group metals from dilute cyanide leach solutions

The research presented in this paper investigated the practical aspects of the recovery of platinum group metals (PGMs) from a dilute cyanide leach solution containing base metals, in a manner similar to that used for gold extraction in a typical CIP process, and focuses on both the adsorption and elution stages. The carrier phase extraction of precious metals using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs. As a sorbent, activated carbon is still by far the most important material because of its large surface area, high adsorption capacity, porous structure, negligible environmental toxicity, low cost, and high purity standards. Adsorption tests were conducted on a pregnant alkaline leach solution (0.15 ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) resulting from cyanide extraction performed in column leach tests. The initial adsorption rates of Pt, Pd, and Au were very fast and recoveries of these three metals were approximately 90 per cent after 2 hours, and 100 per cent for Pt, 97.4 per cent for Pd, and 99.9 per cent for Au after 72 hours. The parameters that influence the extraction of PGMs and Au were examined to assess their relative importance during the adsorption process in order to provide the basis for process optimization. The concentration of thiocyanate was not identified as significant factor for PGMs adsorption, while Ni concentration was the most significant extraction process parameter. Base metal cyanide complexes adsorb and compete with the PGM complexes for sites on activated carbon, and while copper adsorption can be minimized by adjusting the residence time, Ni adsorbs at approximately the same rate as the PGMs, influencing the loading capacity and adsorption kinetics of the PGMs.The feasibility of eluting platinum and palladium cyanide complexes from activated carbon using an analogue of the AARL process was investigated. Platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold still to be eluted after 16 bed volumes. The equilibrium loading of gold is exothermic in nature (Fleming and Nicol, 1984) which will result in an increase in gold elution kinetics with an increase in temperature at similar pre-treatment conditions. A similar result was found for the elution of Pt and Pd. Cyanide pre-treatment was found to have a significant influence on PGM elution. Higher cyanide concentration in the pre-treatment step results in more efficient elution up to a point, and results suggest the possibility of an optimum cyanide concentration, beyond which elution efficiency starts decreasing due to increased ionic strength

Developing a health and human rights training program for french speaking Africa: lessons learned, from needs assessment to a pilot program

<p>Abstract</p> <p>Background</p> <p>The importance of human rights education has widely been recognized as one of the strategies for their protection and promotion of health. Yet training programs have not always taken into account neither local needs, nor public health relevance, nor pedagogical efficacy.</p> <p>The objectives of our study were to assess, in a participative way, educational needs in the field of health and human rights among potential trainees in six French-speaking African countries and to test the feasibility of a training program through a pilot test. Ultimately the project aims to implement <it>a health and human rights training program most appropriate to the African context</it>.</p> <p>Methods</p> <p><it>Needs assessment </it>was done according to four approaches: Revue of available data on health and human rights in the targeted countries; Country visits by one of the authors meeting key institutions; Focus group discussions with key-informants in each country; A questionnaire-based study targeting health professionals and human rights activists.</p> <p><it>Pilot training program</it>: an interactive e-learning pilot program was developed integrating training needs expressed by partner institutions and potential trainees.</p> <p>Results</p> <p>Needs assessment showed high public health and human rights challenges that the target countries have to face. It also showed precise demands of partner institutions in regard to a health and human rights training program. It further allowed defining training objectives and core competencies useful to potential employers and future students as well as specific training contents.</p> <p>A pilot program allowed testing the motivation of students, the feasibility of an interactive educational approach and identifying potential difficulties.</p> <p>Conclusion</p> <p>In combining various approaches our study was able to show that training needs concentrate around tools allowing the identification of basic human rights violations in the health system, the analysis of their causes and coordinated responses through specific intervention projects.</p

Health and Human Rights Education in U.S. Schools of Medicine and Public Health: Current Status and Future Challenges

BACKGROUND: Despite increasing recognition of the importance of human rights in the protection and promotion of health, formal human rights education has been lacking in schools of medicine and public health. Our objectives were: 1) to determine the nature and extent of health and human rights (HHR) education among schools of medicine (SOMs) and public health (SPHs); 2) to identify perceived barriers to implementing HHR curricula; 3) to learn about deans' interests and attitudes toward HHR education, and; 4) to identify factors associated with offering HHR education. METHODS AND PRINCIPAL FINDINGS: We conducted a cross-sectional survey among deans of all accredited allopathic SOMs and SPHs in the United States and Puerto Rico. Seventy-one percent of U.S. SOMs and SPHs responded. Thirty-seven percent of respondents indicated that their schools offered some form of HHR education. Main barriers to offering HHR education included competition for time, lack of qualified instructors and lack of funding. Among schools not offering HHR education, 35% of deans were interested in offering HHR education. Seventy-six percent of all deans believed that it was very important or important to offer HHR education. Multiple regression analysis revealed that deans' attitudes were the most important factor associated with offering any HHR education. CONCLUSION: Findings indicate that though a majority of deans of SOMs and SPHs believe that knowledge about human rights is important in health practice and support the inclusion of HHR studies in their schools, HHR education is lacking at most of their institutions. These results and the growing recognition of the critical interdependence between health and human rights indicate a need for SOMs and SPHs to work towards formal inclusion of HHR studies in their curricula, and that HHR competency requirements be considered to overcome barriers to its inclusion

Morphinofobia: the situation among the general population and health care professionals in North-Eastern Portugal

<p>Abstract</p> <p>Background</p> <p>Morphinofobia among the general population (GP) and among health care professionals (HP) is not without danger for the patients: it may lead to the inappropriate management of debilitating pain. The aim of our study was to explore among GP and HP the representation and attitudes concerning the use of morphine in health care.</p> <p>Methods</p> <p>A cross-sectional study was done among 412 HP (physicians and nurses) of the 4 hospitals and 10 community health centers of Beira Interior (Portugal)and among 193 persons of the GP randomly selected in public places. Opinions were collected through a translated self-administered questionnaire.</p> <p>Results</p> <p>A significant difference of opinion exists among GP and HP about the use of morphine. The word morphine first suggests drug to GP (36,2%) and analgesia to HP (32,9%.). The reasons for not using morphine most frequently cited are: for GP morphine use means advanced disease (56%), risk of addiction (50%), legal requirements (49,7%); for HP it means legal risks (56,3%) and adverse side effects of morphine such as somnolence - sedation (30,5%) The socio-demographic situation was correlated with the opinions about the use of morphine.</p> <p>Conclusions</p> <p>False beliefs about the use of morphine exist among the studied groups. There seems to be a need for developing information campaigns on pain management and the use of morphine targeting. Better training and more information of HP might also be needed.</p

What "best practice" could be in Palliative Care: an analysis of statements on practice and ethics expressed by the main Health Organizations

<p>Abstract</p> <p>Background</p> <p>In palliative care it would be necessary to refer to a model. Nevertheless it seems that there are no official statements which state and describe that model. We carried out an analysis of the statements on practice and ethics of palliative care expressed by the main health organizations to show which dimensions of end-of-life care are taken into consideration.</p> <p>Methods</p> <p>The official documents by the most representative health organisations committed to the definition of policies and guidelines for palliative and end-of-life care had been considered. The documents were analysed through a framework of the components of end-of-life care derived from literature, which was composed of 4 main "areas" and of 12 "sub-areas".</p> <p>Results</p> <p>Overall, 34 organizations were identified, 7 international organisations, and 27 organisations operating on the national level in four different countries (Australia, Canada, UK and United States). Up to 56 documents were selected and analysed. Most of them (38) are position statements. Relevant quotations from the documents were presented by "areas" and "sub-areas". In general, the "sub-areas" of symptoms control as well as those referring to relational and social issues are more widely covered by the documents than the "sub-areas" related to "preparation" and to "existential condition". Indeed, the consistency of end-of-life choices with the patient's wishes, as well as completion and meaningfulness at the end of life is given only a minor relevance.</p> <p>Conclusions</p> <p>An integrated model of the best palliative care practice is generally lacking in the documents. It might be argued that the lack of a fixed and coherent model is due to the relevance of unavoidable context issues in palliative care, such as specific cultural settings, patient-centred variables, and family specificity. The implication is that palliative care staff have continuously to adapt their model of caring to the specific needs and values of each patient, more than applying a fixed, although maybe comprehensive, care model.</p

Identification of the significant factors determining extractability of Ni and Cu after sulfation roasting of a PGM-bearing chromitite ore

Selective sulfation-roast-water leach process of a complex, chromite-rich Cu-Ni-PGM ore to dissolve water-soluble base metal sulfates contained therein was investigated as an alternative process to remove base metals prior to the extraction of precious metals. Ground run-of-mine ore (P80 &lt; 75 µm) was mixed with concentrated H2SO4 (sulfating agent) and Na2SO4 (dual catalyst and sulfating agent) to intensify atmospheric sulfation roast reaction in an unvented electric furnace (static roast under reducing conditions). The acquired calcine was water leached to extract the Ni and Cu sulfates. The roasting conditions were optimized using a Response Surface Methodology which included a Desirability Function Approach in order to maximize Cu and Ni extraction whilst limiting reagent consumption and suppressing Fe and Cr co-dissolution. It was possible to decompose the chromatic-ferritic structure and produce water-soluble metal species by roasting the ore containing 12.80 g/t Pt, 15.20 g/t Pd, 0.0646% Cu, 0.31% Ni, 13.60% Fe and 10.40% Cr. Approximately 90% Ni and 77% Cu were recovered after roasting at 550 °C in closed atmosphere for 2 h with 462 kg/t H2SO4, 76.9 kg/t Na2SO4 and by leaching at 80 °C with 2 wt% solid density for 24 h. The raw ore, roasted mass and water-leach residue were characterized by fire assay and Tescan Integrated Mineral Analysis (TIMA GM Model). Pt + Pd grade has been upgraded from 28 (raw ore) to 32.38 g/t (water-leach residue)

A conceptual hybrid process flowsheet for platinum group metals (PGMs) recovery from a chromite-rich Cu-Ni PGM bearing ore in oxidized mineralization through a single-stage leach and adsorption onto ion exchange resin

The availability of oxidized PGM ore deposits, at or near the earth's surface, present lucrative prospects for future PGM production owing to the large resource estimates, the relatively high PGM grades and they can be mined through relatively lower-cost open-pit mining processes. However, these oxidized PGM ores are currently not mined or treated due to insufficient recoveries using established metallurgical techniques. The complex mineralogy and polymodal distribution of PGM in the oxidized ores pose a number of challenges to the metallurgist from a mineral liberation and extraction perspective. A conceptual route to the integrated processing of a Ni-Cu-PGM bearing chromite ore in oxidized mineralization for the recovery of base and precious metals is presented based upon earlier work of the authors and recent research on metal recovery from solution. This paper presents laboratory batch-scale results of simultaneous adsorption of Pd(II) and Pt(IV) onto commercially available weak-base anion exchange resin, diethylaminoethyl (DEAE) cellulose, from hydrochloric acid solutions. Effects of various variables such as equilibration time, thiocyanate and tin chloride concentrations were studied. Without any prior scrubbing step to remove co-extracted impurities, the uptake of Pd(II) and Pt(IV) was successfully accomplished with recoveries approximating 100% within 15 min. The presence of Fe(III) and other non-ferrous metal accompanying ions didn't show any marked tendency to adsorb. Among the adsorption parameters, thiocyanate concentration had the most significant effect on the process. The dual role of Sn(II) i.e. labilizing agent and PGM collector at a time, was simply overridden, overshadowed by the DEAE high selectivity for PGMs. Thiourea proved to be a better stripping reagent for bulk elution of combined Pd(II) and Pt(IV). A conceptual flowsheet is disclosed for hydrometallurgical pilot scale testing, economic evaluation and assessment of potential environmental impacts

Evaluation of theMerrill–Crowe process for the simultaneous removal of platinum, palladium and gold from cyanide leach solutions

Studies were conducted to evaluate the Merrill–Crowe cementation method for the simultaneous extraction of platinum, palladium and gold associated with copper and nickel from cyanide solutions, particularly high temperature eluates from carbon adsorption and desorption process. The paper reviews the Merrill–Crowe method and its potential for platinum and palladium recovery in the presence of gold, copper and nickel. In a mechanically stirred tank reactor and in the presence of pure nitrogen gas, statistically designed experiments were performed at two levels of the five operating parameters which were the free cyanide concentration, temperature, cementation time, base and precious metal concentrations and their studied ranges were 50–150 ppm, 60–90 °C, 15–90 min, 175–1350 ppm and 220–880 ppm, respectively. The optimum experimental conditions resulted in a solution with free cyanide concentration of 150 ppm at 60 °C and a reaction time of 90 min, base metal concentration of 175 ppm and precious metal concentration of 880 ppm. Under these conditions, cementation yield obtained was 91; 54; 19% for Au(I), Pd(II) and Pt(II) respectively. Zn addition was 1.5 times the stoichiometric amount for complete cementation for the low level case, while it was 0.68 times less the stoichiometric for the high level, in order to monitor competitive aspects of cementation from a mixed solution on a time scale and at conditions that might be relevant to industrial operationsIn contrast to Au cementation reaction, Pd and Pt cementation did not go to completion even though excess zinc powder (0.15 g Zn i.e. 1.5 to 3.4 stoichiometric ratio) was used with their mono-ionic solutions, which gave 48 and 36% of Pd(II) and Pt(II) respectively. In preliminary kinetic studies, deviations from the first-order rate law were observed. The rate of cementation of Au(I) was about 5 times higher than for Pd(II) and 15 times higher than for Pt(II), based on the apparent rate constant, k'1. It was also found that the ratio k'1/k'2 was smallest for Pt, in other words the deviation from 1st order linear kinetics was greatest