Investigating the role of dithiophosphate in the flotation of base metal sulfides

The behaviour of sodium diethyl dithiophosphate (SEDTP) in flotation systems is of major interest to the Platinum Group Mineral (PGM) and Base Metal Sulphide (BMS) industry. Operationally, SEDTP has proved to be a point of contention as there are conflicting views regarding the role of collector with regard to its behaviour at the air-water and solid-water interface in the flotation process. The main objective of this thesis is to attempt to elucidate the surfactant behaviour of SEDTP and in particular its role at both the air-water and solidwater interface. To interpret its behaviour at the air-water interface, bubble pressure tensiometry was used to investigate the effect that SEDTP had on equilibrium surface tension. This was compared to the surface tension of a polypropylene glycol (PPG) frother, which was selected as a benchmark due to it being a surface active agent at the air-water interface and its general use in the industry as a frother. One of the most common collectors used in the PGM industry, sodium ethyl xanthate (SEX), was used as a benchmark collector, which is not known to affect the surface tension. Reagent concentrations were pushed high enough for the air-water surfactant, the frother, to reduce the surface tension (5-100 mM). The maximum concentrations of the three different reagents were tested at pH 7, 9 and 11. The pH was kept constant for other experiments at pH 9 and throughout the investigation the make-up water was deionized water (DIW). To investigate SEDTP’s behaviour at the air-water interface, a frothing column was used to determine its effect on foam stability. Reagent dosages used were similar to those used on plant operations, which are much lower than those used in surface tension experiments. Foam stability experiments were carried out at pH 9 using synthetic plant water (SPW) the constitution of which is shown in the thesis. Solids were subsequently introduced to investigate the effect that SEDTP had on froth stability (3-phase) and compare it to foam stability (2- phase). The solids used were samples from a PGM-containing silicate ore, milled to 60% passing 75 micron. As with the foam stability investigation, the froth stability experiments were carried out at pH 9. The pulp phase floatability of pyrite and galena with SEDTP was measured to investigate the effect that SEDTP had on particle hydrophobicity. Collector-less and pure reagent flotation recoveries were established to relate the effect that reagents had on the floatability. The microflotation of pyrite was carried out at pH 4 and pH 9 to investigate the effect of pH on the flotation of pyrite when using either SEDTP or SEX as single reagents and in the presence of a PPG frother. The effect of frother type and chain length in a mixture containing SEDTP was also investigated on pyrite at pH 4. Microflotation of galena was done at pH 4 to test the relative effect of SEDTP either as a single reagent or in conjunction with a frother compared to pyrite at the same conditions. Collector dosages for all microflotation experiments were determined so as achieve 50% of a single monolayer surface coverage on the mineral surface. This was done by determining the BET surface area of the mineral and using the known surface area footprint of a single collector molecule. Frother concentrations were similar to those used in previous studies. Furthermore, to minimize surface oxidation of the minerals, the samples were stored in nitrogen in a desiccator and acid-washed prior to the experiments. SPW was used to simulate a plant-like solution. Equilibrium surface tension results showed that the reagents used reduced the surface tension in the order: PPG frother, SEDTP, SEX. This is ascribed to the role of these reagents when adsorbing at the air-water interface. Foam stability tests were shown to be more sensitive than surface tension measurements in predicting the surface activity of SEDTP at much lower concentrations than the concentrations used for surface tension experiments. SEDTP did not have any significant effect on foam stability when used as a single reagent. However, when combined with a frother there was a significant improvement in the foam stability. SEX did not display any foam stabilizing effect with either a frother or in a collector mixture with a frother. This is consistent with the surface tension results, thus indicating that, compared to SEX, SEDTP has surface active properties, and more so when in the presence of a frother. The presence of solids in the froth stability experiments diminished the role of SEDTP at the air-water interface since no froth stabilizing effect was observed when it was combined with a frother compared to the two-phase foam system. This may be due to SEDTP partially adsorbing on the solid particles (as was shown by UV-Vis experiments) and thus not being available to affect the air-water interface. The collector mixture containing SEDTP and SEX decreased the froth stability. This may be attributed to increased particle hydrophobicity upon the addition of a collector, which could lend to the destabilization of the froth. Microflotation mineral recoveries are indicative of the bubble-particle attachment efficiency and hydrophobicity. At pH 9, no single reagents improved the recovery of pyrite. Combining SEDTP with a frother did, however, improve the recovery significantly. This was not observed for SEX as a single reagent or when combining SEX with a frother. However a 90 SEDTP: 10 SEX collector mixture containing frother exhibited further synergy by improving the total recovery and flotation rate of pyrite. At pH 4, single reagent flotation improved reagent-less flotation in all cases. The more acidic conditions would give rise to a more reducing environment which accommodates adsorption of surfactants at the solid-water interface. A 90 SEDTP: 10 SEX collector mixture showed synergy in terms of recovery, i.e. the combined effect was much greater than would have been expected from a weighted sum of each individual contribution. It has been proposed that this may be due to the heterogeneity of the surfaces, viz. the stronger collector adsorbing onto the coarser size fraction and weaker, possibly more selective collectors adsorbing onto a finer particle fraction. Once again, a mixture of SEDTP and a frother improved the flotation recovery synergistically, which is not observed when SEX is combined with a frother. Surfactant type, size and structure all contribute to the strength of the surfactant at the airwater interface. However, variable frother types (alcohols and PPG’s) at different molecular weights all displayed a similar synergistic effect with SEDTP. Furthermore, the mineral specificity of this synergistic phenomenon was tested on a second mineral, galena. The galena responded similarly to pyrite, in that an SEDTP-frother mixture significantly improved flotation rate and recovery above any single reagent. The findings in the thesis indicate that SEDTP plays a surfactant role as indicated by its ability to reduce surface tension and improve foam stability. However the presence of solids reduced this effect. In microflotation experiments, SEDTP displayed a synergistic effect when combined with a frother, therefore indicating that it also plays a collecting role by adsorbing at the solid-water interface. This synergistic effect between SEDTP and a frother can be explained by the ability of SEDTP, as well as the frothers, to adsorb at both the air-water interface and the solid-water interface. Furthermore, the presence of one of these surfactants at an interface improves the adsorption of the other in order to maintain electroneutrality. It is proposed that these observations provide supporting evidence for the classical Leja-Schulman penetration theory on the respective role of frothers and collectors in flotation. This theory proposes that during bubble-particle attachment, these interfaces come into contact with one another and condense to form a new mixed collector-frother monolayer at the bubble-particle film. The combination of surfactants that have bubble stabilizing ability and increase particle hydrophobicity at the bubble-particle interface will ultimately improve the flotation of the particles. However, it was shown in this dissertation, that this synergistic interaction is significant only in the case of SEDTP. SEX showed no evidence of this mechanism operating at all. This may be because all available xanthate molecules are adsorbed onto the solid surface and are unavailable to act at the airwater interface. In addition, it was shown that SEX is an extremely poor surfactant at the airwater interface. These findings have important ramifications for the current processing of PGMs and BMS where DTP is widely used

Gesinsgeweld: 'n kriminologiese ondersoek

The purpose of this research was to describe and explain family violence in the Gauteng Province of South Africa. It was conducted by means of a literature review, followed by empirical research, based on police dockets, against the background of Seligman's theory on learned helplessness. Other theories were also applied eclectically. The literature review was used to design a research schedule (questionnaire). This schedule was used for data capturing from police dockets from the Crime Information Analysis Centre (CIAC) at their Gauteng Regional office in Johannesburg. From this data, a convenience sample consisting of 415 cases, was compiled. These cases were reported at the charge offices of Laudium, Alexandra, Hillbrow, Rietgat, Eersterust and Mamelodi, during the period between 1 January 2001 and 1 March 2002. Domestic violence is caused by macrosocial-, gender- and relationship factors. These causes can be explained by certain aspects of structural- process- reaction and the learned helplesness theories. The adjudication of this causes and explanations focus on primary, secondary and tersiary aspects of prevention. Triggering facors, confrontation, crime incidents and restoring the equalibrium were studied in relation to the dynamics of domestic violence. All these factors such as causes, explanations, prevention and dynamics , are considered to explain the stabilization of domestic violence.Die doel van hierdie navorsing was om gesinsgeweld in die Gauteng-Provinsie van Suid-Afrika te beskryf en te verklaar. E)it is gedoen aan die hand van 'n literatuurstudie, en is uitgebrei met 'n empiiiese ondersoek wat op polisiedossiere gebaseer is, teen die agtergrond van Seligman se teorie van aangeleerde hulpeloosheid, asook ander teoriee wat eklekties bygewerk is. Die literahmrstudie is gebrnik om 'n skedule (vraelys) te ontwerp. Die navorsingskedule is gebruik vir datavangs uit polisiedossiere. Die polisiedossiere van die Misdaadinligting- Analisesentrum (MIAS) van Gauteng se streekkantoor in Johannesburg is gebruik vir die samestelling van 'n geriefHkheidsteekproef bestaande uit 415 gevalle. Hierdie gevalle kom uit die aanmeldings by die aanklagkantore van Laudium, Alexandra, Hillbrow, Rietgat Eersterust en Mamelodi, tussen 1 Jamiaiie 2001 en 1 Maart 2002. Makrososiale faktore, geslagsrolsosialisering en verhoudingsfaktore veroorsaak gesinsgeweld. Sekere elemente van die struktuur- proses- reaksie- en aangeleerde hulpeloosheidsteoriee kan dit verklaar. Die beregting van bogenoemde fokus op primere, sekondere en tersiere voorkomingsaksies. Die dinamika waarop gefokus word met betrekking tot gesinsgeweld sluit in aspekte soos: die snellerfaktore, konfrontasie, die praktiese misdaadinsident en uiteindelik die herstelde ekwillibrium. A1 die faktore (oorsake, verklarings, voorkoming en dinamika) lei uiteindelik tot die stadium waar waar verduidelik word hoe gesinsgeweld gestabilliseer word.Criminology and Security ScienceD. Litt. et Phil. (Criminology

Communication between PLC different vendors using OPC server improved with application device

Many industries often use different devices and controllers in automation systems. They all face the same difficulty how to exchange data between all those components. This paper proposed the implementation of OPC Server as software interface on communication between two different controllers, PLC Mitsubishi and PLC Omron. The main advantage of the method is the compatibility and solution for the factory difficulty problem because of using several driver controller. The compatibility among the different platforms of both controller, PLC Mitsubishi and PLC Omron, can be reached by use of KEPServerEx6 (OPC server) as a software interface. To test the compatibility amongst two different controllers, there was developed and implemented two field application devices, bottle unscramble and bottle filling station. This implementation shows OPC Server technology resolving data compatibility issues between different platforms and reducing development costs. It is envisaged that the method can be very useful to realize integration

केरल के मुनम्बम में खुला सागर पिंजरा पालन और प्लवकों और नितलस्थ जीबों पर इसका प्रभाव

कृपया पूरा लेखा पढ

Preliminary studies on the impact of open sea cage culture of Lates calcarifer (Bloch) on the planktonic and benthic fauna off Cochin, Kerala

The plankton and benthic macrofauna in relation to the open sea cage culture of Lates calcarifer during the period from October 2008 to March 2009 off Munambam near Cochin were studied. The cage site and a reference site were selected for simultaneous sampling. During the study, the cage culture activity was not found to influence the plankton population but there is an indication of its influence on the benthic macrofauna

कोच्ची की समुद्री स्फुटनशाला में मृदु प्रवाल लोबोफाइटम साक्रोफाइटोइडस का पालन

Culture of soft coral, labophytus sacrophytoides in marine hatchery at Koch

Osteogenic capacity of nanocrystalline bone cement in a weight-bearing defect at the ovine tibial metaphysis

The synthetic material Nanobone® (hydroxyapatite nanocrystallines embedded in a porous silica gel matrix) was examined in vivo using a standardized bone defect model in the ovine tibial metaphysis. A standardized 6 × 12 × 24-mm bone defect was created below the articular surface of the medial tibia condyles on both hind legs of 18 adult sheep. The defect on the right side was filled with Nanobone®, while the defect on the contralateral side was left empty. The tibial heads of six sheep were analyzed after 6, 12, and 26 weeks each. The histological and radiological analysis of the defect on the control side did not reveal any bone formation after the total of 26 weeks. In contrast, the microcomputed tomography analysis of the defect filled with Nanobone® showed a 55%, 72%, and 74% volume fraction of structures with bone density after 6, 12, and 26 weeks, respectively. Quantitative histomorphological analysis after 6, and 12 weeks revealed an osteoneogenesis of 22%, and 36%, respectively. Hematoxylin and eosin sections demonstrated multinucleated giant cells on the surface of the biomaterial and resorption lacunae, indicating osteoclastic resorptive activity. Nanobone® appears to be a highly potent bone substitute material with osteoconductive properties in a loaded large animal defect model, supporting the potential use of Nanobone® also in humans

Dose-related beneficial long-term hemodynamic and clinical efficacy of irbesartan in heart failure

AbstractOBJECTIVESThe primary purpose of this study was to determine the acute and long-term hemodynamic and clinical effects of irbesartan in patients with heart failure.BACKGROUNDInhibition of angiotensin II production by angiotensin-converting enzyme (ACE) inhibitors reduces morbidity and mortality in patients with heart failure. Irbesartan is an orally active antagonist of the angiotensin II AT1receptor subtype with potential efficacy in heart failure.METHODSTwo hundred eighteen patients with symptomatic heart failure (New York Heart Association [NYHA] class II–IV) and left ventricular ejection fraction ≤40% participated in the study. Serial hemodynamic measurements were made over 24 h following randomization to irbesartan 12.5 mg, 37.5 mg, 75 mg, 150 mg or placebo. After the first dose of study medication, patients receiving placebo were reallocated to one of the four irbesartan doses, treatment was continued for 12 weeks and hemodynamic measurements were repeated.RESULTSIrbesartan induced significant dose-related decreases in pulmonary capillary wedge pressure (average change −5.9 ± 0.9 mm Hg and −5.3 ± 0.9 mm Hg for irbesartan 75 mg and 150 mg, respectively) after 12 weeks of therapy without causing reflex tachycardia and without increasing plasma norepinephrine. The neurohormonal effects of irbesartan were highly variable and none of the changes was statistically significant. There was a significant dose-related decrease in the percentage of patients discontinuing study medication because of worsening heart failure. Irbesartan was well tolerated without evidence of dose-related cough or azotemia.CONCLUSIONSIrbesartan, at once-daily doses of 75 mg and 150 mg, induced sustained hemodynamic improvement and prevented worsening heart failure

Prevalence and antimicrobial susceptibility of Arcobacter species in human stool samples derived from out- and inpatients: the prospective German Arcobacter prevalence study Arcopath

Background: Arcobacter species, particularly A. butzleri, but also A. cryaerophilus constitute emerging pathogens causing gastroenteritis in humans. However, isolation of Arcobacter may often fail during routine diagnostic procedures due to the lack of standard protocols. Furthermore, defined breakpoints for the interpretation of antimicrobial susceptibilities of Arcobacter are missing. Hence, reliable epidemiological data of human Arcobacter infections are scarce and lacking for Germany. We therefore performed a 13-month prospective Arcobacter prevalence study in German patients. Results: A total of 4636 human stool samples was included and Arcobacter spp. were identified from 0.85% of specimens in 3884 outpatients and from 0.40% of specimens in 752 hospitalized patients. Overall, A. butzleri was the most prevalent species (n = 24; 67%), followed by A. cryaerophilus (n = 10; 28%) and A. lanthieri (n = 2; 6%). Whereas A. butzleri, A. cryaerophilus and A. lanthieri were identified in outpatients, only A. butzleri could be isolated from samples of hospitalized patients. Antimicrobial susceptibility testing of Arcobacter isolates revealed high susceptibilities to ciprofloxacin, whereas bimodal distributions of MICs were observed for azithromycin and ampicillin. Conclusions: In summary, Arcobacter including A. butzleri, A. cryaerophilus and A. lanthieri could be isolated in 0.85% of German outpatients and ciprofloxacin rather than other antibiotics might be appropriate for antibiotic treatment of infections. Further epidemiological studies are needed, however, to provide a sufficient risk assessment of Arcobacter infections in humans