Separation of pyrite from arsenopyrite by flotation

This thesis reports investigations into the flotation separation of pyrite from arsenopyrite using xanthates and the new collectors Fl, S7 and F2B developed by Dow Chemical Company. The Dow surfactants were classified as chelating collectors by the manufacturer. For this purpose Hallimond tube, bench and column flotation tests were run in order to assess the flotation behaviour of these minerals. In addition to these experiments other tests performed were adsorption characteristics of Fl on pyrite and arsenopyrite, the effect of Fl on electrophoretic mobility and surface tension of Fl solutions. The effect of pH on the recovery of pyrite and arsenopyrite was studied for all collectors with the Hallimond tube. pH values ranging from 2 to 12 were tested at constant collector concentrations. At the optimum pH values further experiments were carried out under varying collector concentrations. The results obtained for five different collectors showed that selectivity was rather poor at all conditions except for Fl. A successful separation was seen to be possible employing Fl and by floating pyrite. This was proven by using a mixture of equal amounts of pyrite and arsenopyrite and selectively floating pyrite. Bench and column flotation tests were carried out in order to confirm the results obtained with the Hallimond tube. A Denver flotation cell was used and a column cell was constructed. In these tests Fl was used as a collector and in some cases amyl xanthate was blended. The effect of collector concentration was monitored and other parameters were adjusted for an optimum separation. Observations showed that a selective flotation of pyrite from arsenopyrite could be possible. Adsorption characteristics of Fl on pyrite and arsenopyrite were studied as a function of collector concentration, pH and time. Though there was not a direct correlation between the amount of Fl adsorbed and the success of flotation, in general pyrite was found to adsorb more Fl than arsenopyrite. Electrophoretic mobility of pyrite and arsenopyrite against pH and collector concentration was measured. It was observed that Fl did not have a substantial effect on the electrophoretic mobility of these minerals. The measured pK value of Fl indicated that most of the collector in solution was in molecular form above pH 9.2.Open Acces

The prevalence of microalbuminuria and relevant cardiovascular risk factors in Turkish hypertensive patients.

Objectives: A growing body of data illustrates the importance of microalbuminuria (MAU) as a strong predictor of cardiovascular risk in the hypertensive population. The present study was designed to define the prevalence of MAU and associated cardiovascular risk factors among Turkish hypertensive outpatients. Study design: Representing the Turkish arm of the multinational i-SEARCH study involving 1,750 sites in 26 countries around the world, a total of 1,926 hypertensive patients from different centers were included in this observational and cross-sectional survey study. Patients with reasons for a false-positive MAU test were excluded. The prevalence of MAU was assessed using a dipstick test, and patients were inquired about comorbidities, comedication, and known cardiovascular risk factors. Results: The overall prevalence of MAU was 64.7% and there was no difference between genders. Most of the patients (82.5%) had uncontrolled hypertension, 35.6% had dyslipidemia, and 35.5% had diabetes, predominantly type 2. Almost one-third of the patients (26.4%) had at least one cardiovascular-related comorbidity, with 20.3% having documented coronary artery disease (CAD). Almost all patients (96.8%) had one or more risk factors for cardiovascular disease in addition to hypertension, including family history of myocardial infarction or CAD, diabetes, dyslipidemia, lack of physical exercise, and smoking. A trend towards higher MAU values in the presence of CAD was determined. Conclusion: Microalbuminuria tests should be routinely used as a screening and monitoring tool for the assessment of subsequent cardiovascular morbidity and mortality among hypertensive patients. © 2011 Turkish Society of Cardiology