S Prabhakar

Alteration Characteristics Of Ilmenites From South India

Two different placer samples from the Navaladi and Surungudi area of Teri,Tamilnadu, in southern India, were collected and characterized in terms of their heavy mineral content. Mineralogical analysis on both the samples revealed the presence of high amounts of garnet and ilmenite. The alteration characteristics of ilmenite from these deposits were investigated by optical and electron probe microanalysis. Optical microscopic studies revealed that the alteration of ilmenite was seen to proceed along grain boundaries and/or fractures resulting in an amorphous to crypto- or microcrystalline mass resembling leucoxene. The alteration is in the nascent stage. Mineral chemistry by electron probe micro-analysis revealed the enrichment of TiO2, MgO, Al2O3, Cr2O3, SiO2, V2O5 and Na2O in the altered products and loss of iron oxide and manganese oxide from the ilmenite grains during weathering leading to the formation of leucoxene. Similarly EPMA studies on garnet indicated that it is of the almandine variety. This study reveals that the alteration of ilmenite by weathering leads to unstable phases, with complex elemental distribution patterns. The physico-chemical characteristics of the mineral and, in turn, the down-stream metallurgical processing are affected by such alteration processes. Key words: Placer Ilmenite, Alteration, EPMA, Navaladi

Flotation and adsorption studies of chalcopyrite with cupferron

Abstract Flotation tests were conducted in a Hallimond tube on chalcopyrite, with a collector system of cupferron and fuel oil. The reagent concentration, pH and conditioning time were studied as variables. The necessity of the fuel oil was verified by conducting experiments without it. Contact-angle measurements have been conducted by the captivebubble technique. From the results it was found that fuel oil is necessary to promote adhesion of the conditioned mineral particles to the air bubbles. Adsorption experiments were carried out in a column apparatus under similar conditions as in flotation, except for the addition of fuel oil. The adsorption density and flotability were high at weakly acidic range where the reagent complexes the metal ions effectively in an aqueous medium.

Beneficiation of low grade graphite ore of eastern India by two-stage grinding and flotation

A low grade graphite run-of-mine (r.o.m) ore from eastern India was studied for its amenability to beneficiation by flotation technique. The petrography studies indicate that the ore primarily consists of quartz and graphite with minor quantity of mica. It analyzed 89.89% ash and 8.59% fixed carbon. The ore was crushed in stages followed by primary coarse wet grinding to 212 μm (d80). Rougher flotation was carried out in Denver flotation cell to eliminate gangue as much as possible in the form of primary tailings with minimal loss of carbon. Diesel & pine oil were used as collector and frother respectively. Regrinding of rougher concentrate to150 μm (d80) was resorted to further liberate the graphite values and was followed by multi-stage cleaning. This two-stage grinding approach involving a primary coarse grinding and regrinding of rougher float followed by its multi-stage cleaning was found to yield required grade of concentrate for applications such as refractories, batteries and high temperature lubricants. This approach is supposed to retain the flake size of coarse, free and liberated graphite, if available, during primary coarse grinding and rougher flotation stage with minimal grinding energy costs as against the usual practice of single stage grinding in the case of many ores. A final concentrate of 8.97% weight recovery with 5.80% ash and 92.13% fixed carbon could be achieved.

Degradation of Tannic Acid Using TiO2 Nanotubes as Electrocatalyst

Structured TiO2 nanotubes were grown on 2 mm thick titanium sheet by anodization of titanium in ethylene glycol medium containing 0.025 M NaF. The morphology of TiO2 nanotubes (TNT) was characterized using field emission scanning electron microscope. The potential of TNT as anode and also as photocatalyst for the degradation of tannic acid was studied. The mineralization of tannic acid was measured in terms Total Organic Carbon (TOC). Only 50% of TOC could be removed by exposing the tannic acid solution to UV-radiation (photolysis), whereas it was improved to 70% by electrooxidation (EO) using TNT as anode. Maximum degradation of 83% was achieved when electrooxidation was conducted under the influence of UV-radiation (photoelectrocatalytic process (PEC)). Among the electrolytes tried, Na2SO4 was observed to be very effective for the degradation of tannic acid. The kinetics of tannic acid degradation by photoelectrocatalytic process was found to follow zero-order rate expression.

Degradation of Tannic Acid Powered by TiO2 Nanoparticles

The wastewater from the coir, pharmaceutical, leather, paper and pulp industries is contaminated with water-soluble poly phenolic compounds (tannins). Among various tannins, tannic acid is a typical hydrolysable tannin prevalent in wastewater. The degradation of tannic acid using TiO2 nanoparticles as photocatalyst was investigated. The effect of catalyst concentration, pH of aqueous suspension and also electron acceptors such as hydrogen peroxide (H2O2) and ozone (O3) on the degradation of tannic acid was studied. The degradation of tannic acid was found to be more efficient and complete in the presence of UV/TiO2/O3 compared to UV/TiO2/H2O2. The kinetics of degradation was observed to follow first order rate equation which indicates that the mineralization process is diffusion controlled.

Pilot-scale studies on the treatment of tannery effluents by electroflotation

A pilot-scale electroflotation system with a treatment capacity of 0.8 m³ per hour has been designed and built. The system is equipped with a conditioning tank, a rectifier, flow meters, an energy meter and pumps. Iron, aluminium and titanium coated with oxides of tantalum, ruthenium and iridium were used as electrodes. The system was installed within the premises of the Common Effluent Treatment Plant (CETP), which receives effluents from nearly 200 tanneries. The effectiveness of electroflotation for the separation of suspended solids, sulphur species, chromium and other chemicals contributing to COD and BOD were studied. The separation of suspended solids and chromium by electroflotation was nearly complete (>95%) and their concentration in the processed samples can be maintained well below the discharge limits. The removal of COD was observed to be 15?20% greater than with conventional chemical coagulation. Furthermore, the entire spectrum of pathogenic bacteria was eliminated to the extent of 99.97% by subjecting the effluent to electroflotation.

Studies on the Zetapotential of Calcite/p-Sulfonato-calix[4,8]arenes

Zeta potential of calixarenes has been reported for the first time. The water-soluble calixarenes has been used as dispersion media in solid/liquid interface. p-sulfonato-calix[4]arene (PSC4) and p-sulfonato-calix[8]arene (PSC8) were synthesized and characterized by FTIR, NMR, mass spectrometry, and HPLC techniques. It was proved that the zeta potential is a fast and simple measurement to know the adsorption behavior of sufonato calixarnes on calcite. The chemisorption of p-sulfonato-calix[n]arene was confirmed by shift in iso electric point, adsorption studies and FTIR. The calculated free energy of adsorption value and its sign suggests the chemical interaction between the calcite surface and p-sulfonato calix[4]and[8]arene.

Electrokinetic Behavior of Fluorite

The electrokinetic behavior of fluorite mineral was studied under various partical sizes and different concentrations of oleic acid at constant pH. The particle size has been reduced with an increase in activation time. The surface energies of milled fluorite minerals were calculated theoretically and experimentally. The zeta potential of the fluorite/water system has shifted to lower side with an increase in particle size. The isoelectric point (iep) of fluorite minerals has been shifted to lower side with increase in oleic acid concentration. This indicates the chemisorbed oleate formation on fluorite. A sharp decrease in zeta potential in the pH range of 6.5–8.4 and the decrease in calculated free energy of adsorption shows the formation of calcium dioleate precipitate on fluorite.