Role of Mixed Collector Systems in Selective Separation of Albite from Greek Stefania Feldspar Ore

The adsorption behaviour of mixed cationic alkyl diamine and anionic sulfonate/oleate collectors and a combined cationic-anionic collector, N-tallow 1, 3-propane diamine dioleate (Duomeen TDO) at acidic pH values on albite and quartz minerals was investigated through Hallimond flotation, electrokinetic and diffuse reflectance FTIR studies. The reagent schemes are tested in bench scale flotation for the separation of albite from Greek Stefania feldspar ore. The single mineral flotation tests showed the feasibility of selective albite flotation from quartz at pH 2 where the doubly positively charged collector species adsorb on albite but not on quartz. However, the adsorption behaviour of mixed collectors on albite and quartz at the same pH value, as evidenced from zeta-potential and FTIR studies, is almost similar. The IR spectra show the co-existence of neutral oleic acid together with charged amine species at low pH values. The bench scale flotation results indeed showed that selective albite flotation takes place only after desliming the feed material. An albite concentrate exceeding 10 Wt% Na2O content is produced from a material containing about 6.5 wt% Na2O, where an albite product more than 9 wt% Na2O is considered to be valuable

Liquid phase hydrogenation of crotonaldehyde over Pt/SiO2 catalysts

The dependence of the catalytic properties of Pt/SiO2 catalysts for the hydrogenation of crotonaldehyde on the hydrogen pressure, the reaction temperature, the nature of the solvent and the presence of several additives were investigated. Strong deactivation of the catalysts mainly caused by decarbonylation of crotonaldehyde and irreversible adsorption of CO was observed. The initial activity of the deactivated catalysts is regained by oxidation of the adsorbed CO to CO2 by purging with air. The selectivity to crotylalcohol increased with increasing number of turnovers per metal site. This is explained with preferential blocking of the nonselective sites on the metal crystallites by CO and by a slow surface modification of the aging catalyst with organic deposits. The overall rate and the selectivity to the saturated aldehyde are markedly enhanced by an increase in hydrogen pressure and by a decrease in reaction temperature. The addition of modifiers such as potassium acetate, triphenylphosphine and thiophene had only little influence on the activity and the selectivity of the catalysts

Froth Flotation and its Application to Concentration of Low Grade Iron Ores

Froth flotation is a process used to separate minerals, suspended in liquids, by attaching them to gas bubbles to provide selective levitation of the solid particles. It is most extensively used process for the separation of chemi-cally similar minerals, and to concentrate ores for econo-mical smelting. Flotation is a selective process and can be used to achieve separation from complex ores such as lead-zinc, copper- zinc etc.Initially developed to treat the sulphides of copper, lead, and zinc, the field of flotation has now expanded to include oxides, such as hematite and cassiterite, oxidised minerals, such as mala-chite and cerussite, and non-metallic ores, such as fluo-rite, phosphates, and fine coal

Kinetics And Efficacy Of Froth Flotation For The Recovery Of Metal Values From Pulverized Printed Circuit Boards

Printed circuit boards (PCBs) constitute a major part of electrical and electronic equipment containing valuable metals such as Cu, Ni, Au, Ag, Pd, Fe, Sn, Pb, etc. The concentration of base and precious metals in PCBs is observed to be several times more than those in their respective ores. Therefore, the recycling of PCBs is necessary to recover the valuable materials. However, the ultrafine particles pose a big challenge. Removal of them is suggested prior to processing by flotation. Froth flotation is observed to be a promising technique for rejecting the plastics from the comminution product. In the present work, enrichment of ground 1.0 mm PCB powder was investigated through flotation route by varying the operating variables such as frother dosage, pulp density, air flow rate and rotational speed of the impeller. The liberation studies indicate that excellent liberation of metal values is achieved from the non-metallic constituents at -1.0 mm size and below. The particulate system is quite rich in metal value with about 23% total metal content. The non-metallic constituents such as plastics are observed to possess strong hydrophobicity while the metal particles in the pulverized mass are hydrophilic in nature. Froth flotation kinetics is studied in depth with a view to facilitate high rejection of the plastics and identify optimum operating conditions for the same. A number of experiments are performed to establish the influence of the operating variables on flotation performance. The conditions for achieving higher yield of the metal-rich fraction with respect to a specified grade are discussed in the light of the experimental results. It is found that the requirement of reagents is negligible which could be a very important factor from the commercial stand point. Single-stage flotation increases the metal content from 23% to over 32% with a mass yield of around 75% and over 90% recovery of metal values. 32% of the materials in the feed could be effectively rejected in the float fraction losing less than 4% metal values. The dependence of kinetics on the process variables is also discussed. It was concluded that a high rotor speed helps in efficiently rejecting the plastics. Frother should be added to help stabilize the froth and enhance the kinetics. A moderate air flow is required while pulp density must be kept low for efficient pre-concentration. It is established that the entire -1.0 mm comminution product could be treated by flotation for generating a pre-concentrate

Reduction of phosphorous content in LD slag through spiral concentrator for industrial utilization

Slag generated from basic oxygen converter (LD slag) is one of the recyclable wastes in integrated steel plants. LD slag may be used in refining of steel or in iron-making due to its high metal value and lime content. Presently, it is neither used in steel making nor in iron making. The LD slag processing conducted in waste recycling plant recovers about 20-25% of its total weight. The non-magnetic fraction which is -6mm in size is either discarded or utilized as aggregate in roads construction application. The reject of waste recycling plant, post metal recovery, is virtually stripped of metallic iron content, apart from the fact that the sparse or meagre iron value content mostly happens to be in oxide form. However, these rejects of recycling do contain considerable quantity of calcium bearing mineral phases like mono, di and tri-calcium silicates. These calcium silicates with its inherent advantage in possessing good fluxing value finds productive utilisation in iron ore sintering. However the steel slag rejects cannot be utilized as such since these contains 1.2-1.5% P which is not acceptable for iron ore sintering. Thus, the primary focus and concern lies in its effective recycling for exploiting its utilization for various applications. In the current study, the efficacy of 7-turn coarse spiral followed by 8-turn fine spiral concentrator was evaluated to process fine (-0.5 mm) LD slag for lowering Phosphorus (P) content to the desired level for its application in iron ore sintering. The effect of varying operating parameters on the performance of spiral has been studied through optimization experiments at different feed flow rates ranging from 18-22.2 Kg/min and altering the splitter positions for varying the density of feed pulp from 18-20%. Under optimized conditions, the results indicate that the concentrate product with low phosphorous content of about 0.76% is achieved, which is far too less from industry requirement perspective of <0.90% phosphorous content with a yield of 31%, and this can be effectively utilized for iron ore sintering. However, the yield of concentrate in the experiments undertaken varied proportionally from 31-57%, depending upon the level of phosphorus content desired in the concentrate i.e 0.76-0.90%. The main mineral phases contained in the slag were identified using X-ray diffraction (XRD) and complementary analysis were undertaken using scanning electron microscopy (SEM) coupled with energy dispersive spectrometer (EDS). The results were discussed in the light of our experimental results

Adsorption Mechanism of Longchain Alkylamines on Quartz and Albite

The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz and albite using the direct methods of FTIR and XPS spectroscopy. The spectroscopic data were correlated with the data of indirect methods of zeta-potential measurements and Hallimond flotation results. It was shown from infrared spectra that the amine cation forms strong hydrogen bonds with surface silanol groups. The XPS spectra revealed the presence of molecular amine together with the protonated amine on silicate surface. Based on these observations, a model of successive two-dimensional and three-dimensional precipiation was suggested to explain amine adsorption on silicate surface

Recovery of clean coking coal from difficult-to-wash low volatile coking coal fines of Jharia coalfield by multi gravity separator

Multi gravity separator (MGS) is a centrifugal gravity separator deployed for beneficiation of fine particles with relatively low concentration. It is for the first time, that a statistical tool was engaged to evaluate effects of the most influencing process variables and their actual impact upon the performance of MGS with respect to its potential to clean the difficult-to-wash low volatile coking (LVC) coal fines. Characteristics of LVC coal sample was analysed and discussed in terms of physical properties, petrographic composition, washability, XRD and SEM analysis. Three different feed sizes such as –500 μm, –250 μm and –150 μm were used for assessing the separation mechanism and efficacy of MGS along with three different process variables such as drum speed, shaking amplitude and wash water rate to study and ascertain the most efficient experimental design for obtaining optimal result. Results revealed that drum speed and feed size turned out to be most significant parameters for reduction of ash concentration. In design of experiments, clean coal ash, combustible recovery and separation efficiency were considered as response functions. Material balance for MGS unravelled that about 74% clean coal produced with 10% ash reduction from the feed ash of 32.8% could be achieved in single stage, in optimized process conditions

A Critical Review of Subclinical Hypothyroidism in Ayurveda

Subclinical Hypothyroidism is a clinical syndrome which result from the deficiency of Thyroid hormones. Usually, it runs a chronic course with slow and insidious onset. Sometimes it is only accidentally diagnosed. Thyroid gland abnormality where, on one hand influences body metabolism up to a great extent, on the other hand, it is found more in females with ratio of male to female being 1:6, if left untreated it can lead to severe complication. In Ayurveda there is no direct comparison regarding symptoms of Subclinical Hypothyroidism but on the basis of clinical presentation it can be correlated with different entities as syndrome, so it is difficult to give a single Ayurvedic term for it, as there are many systems which are involved in the pathogenesis of Subclinical Hypothyroidism. Hence the symptoms of Pre-clinical and post clinical findings are compared with Rasapradoshaja Vikaras

Flotation Of Quartz And Hematite: Adsorption Mechanism Of Mixed Cationic/Anionic Collector Systems

Using pure quartz and hematite minerals, the adsorption mechanism of mixed cationic/anionic reagent schemes was investigated through Hallimond flotation studies. The flotation response of quartz and hematite independently with cationic and anionic collectors as well as with mixed cationic/anionic collector systems is assessed. The flotation response as a function of pH and collector concentration was investigated. The single mineral flotation tests in the presence of anionic collectors, quartz does not respond to flotation but the C12 amine flotation of quartz was observed to be pH and concentration dependent. It was observed that hematite flotation recovery is maximum at acidic pH with sodium dodecyl sulphate (SDS), neutral pH with oleate, and at basic pH about 9.5 with C12 amine. Flotation results with both quartz and hematite indicate an increased adsorption of cationic collector in the presence of anionic collector apart from its own co-adsorption. The incorporation of oleate in between C12 amine molecules decreases the electrostatic head-head repulsion and thereby increasing the adsorption of C12 amine due to attractive tail-tail hydrophobic bonds, besides forming a closely packed adsorbed layer enhancing the hydrophobicity. The increase in oleate concentration beyond C12 amine concentration leads to the formation of soluble diamine-oleate complex / precipitate and the adsorption of these species decreased the flotation since the alkyl chains are in chaotical orientation with a conceivable number of head groups directing towards the solution phase

Modeling of Fine Coal Processing in a Teeter Bed Separator

Beneficiation of fine coal using Floatex density Separator (FDS) is investigated through experimental and computational approaches. Performance of the FDS is determined through detailed experimentation. The separation in the FDS is also described theoretically using a slip velocity correlation and steady state mass balance equations. The performance of the FDS is estimated by solving the resulting set of mathematical equations. The computed data are found to be in reasonable agreement with the experimental observations albeit with certain deviations. It is shown that at a low bed pressure the FDS acts as a size classifier. At an elevated bed pressure density based concentration is the dominant mode of separation. Low teeter water flow rate is inadequate for hydraulic transport of particles while too high a value leads to misplacement. It is shown that a velocity model based on modified Richarson and Zaki equation in which the dissipative pressure gradient is considered to be the primary driving force for separation predicts the performance more accurately than the other models