Recent developments in flotation for the beneficiation of lowgrade finely disseminated ores

Rapid increase in consumption rate of metals and minerals over the last few decades and consequent depletion of mineral resources have necessitated the effective utilization oflow-grade finely disseminated ores. The utilization of such reserves and recycling of metallic waste can help to maintain an adequate supply of minerals to meet economic and strategic needs of our nation. Since the yield of low-grade ores is generally very low, the technoiQgy/ process should be efficient to make it cost effictive. Recent equipments like flotation column and Jameson ceil which are basically designed to float fine particles are energy efficient. Selective reagents are being designed for the separation of individual minerals from complex assemblage. The necessity of biodegradable and eco-friendly reagents is highlighted. In the present paper; recent developments in flotation celis and beneficiation of low-grade ores was presented and discussed. Beneficiation of low-grade barite sample from Mangampet deposit was conducted both by direct flotation using oleic acid and reverse flotation by cationic collector. Production of barite concentrate assaying Less than 1% silica by reverseflotation was demonstrated. Similarly, limestone concentrate assaying 97% of CaC03 and Less than 1% Si02 was achieved by reverseflotation process. The viability offlotation processfor up-graddtion of siliceous iron ores waS also studied and discussed

Beneficiation of low-grade iron ores

The Government of India highlighted, processing and utilization of iron ore fines as pre-requisite to meet the domestic raw material requirements for the projected 110 million tonnes of domestic steel production by the year 2019-20 in the National Steel Policy announced in November 2005. This would require 190 million tonnes of iron ore. The depletion of high grade iron ore and increased generation of fines during mining and handling and demand for high grade iron orefines for export has necessitated the processing of low to medium grade fines. The R&D efforts undertaken at NML-Madras Centre, India in this direction have been highlighted. Beneficiation of iron ores in general and column flotation in particular are highlighted in this paper. This would also mitigate the environmental problem created by the dumping of huge quantities of low and medium grade iron orefines. Three case studies involving iron ore fines of varying silica and alumina content from Goa and Kudremukh regions of India have been discussed. The results clearly indicate the feasibility and significance of flotation process in treating the fines to obtain marketable concentrates

Adsorption of thiol collectors on Chalcopyrite

Adsorption of diethyldithiocarbamate and ethylxanthate on chalcopyrite mineral surface was studied by static bed adsorption method. The qualitative nature of surface species was examined by selective solvent extraction and UV-visible spectroscopic technique.The results clearly indicate that the interaction between surface metal ions and thiols is chemical in nature. As a result of chemical interaction of ligand molecules, metal ions from mineral surface are dislodged from the lattice and precipitates of metal-ligand complexes were formed on the surface. Surface complexes were found to be identical to that of bulk complexes with metal-to-ligand ratio of 1:2

Electrokinetic studies on covellite, cuprite and tenorite

Detailed electrokinetic measurements are conduct.ed on synthetic covellite, cuprite and tenorite particles. The role of potential determining ions identical to that of the particle lattice is considered in addition to usual H+ and hydroxide ions. In the case of CuS, additional charge reversals are noticed between pH ~ 2.5 and < 6.0 in addition to the usual charge reversals that occur by direct hydrolysis in the socalled region of metal ion precipitation. Interaction of protons with hydrous mineral surface and the adsorption of desorbed or exces metal ions with protonated surface sites are explained by ion exchange mechanism. Effect of reducing environment and oxidation-reduction reactions o

Adsorption mechanism of diethyldithio carbamate on covellite, cuprite and tenorite

Adsorption of diethyldithiocarbamate (DTC) on covellite, cuprite and tenorite was investigated under different experimental conditions. The qualitative nature of surface species formed at the interface was examined by selective solvent extraction and UVvisible spectrophotometric techniques. The presence of surface species such ::lB [Cu(DTC)]+, Cu(DTC)2and Cu(I) DTC at different concentrations of the reagent and pH of the suspension was investigated. The results of this study indicate a surface reactionbetween DTC ligand molecules and surface copper sites. As a result of interaction with DTC, cations on the mineral surface are dislodged from the lattice and precipitated on the surface as copper dithiocarbamate complexes. Depending on the concentration of DTC, two types of copper complexes, i.e. [Cu(DTC)]+at low concentration and Cu(DTCh at higher concentration, are noted on copper(II) substrates, whereas on cuprite Cu(I) DTC was formed along with [Cu(DTC)]+ and Cu(DTCh. From the kinetic study, the overall adsorption was found to be mainly controlled by diffusion processes

Removal of organic dyes and tannins by electrochemical techniques.

Removal of organic dyes, tannins and phenol based molecules from aqueous solutions and the amenability of electrochemical techniques for the treatment of dye bath and tannery effluents was discussed. In the case of electro-coagulation/flotation, aluminum and steel were used as electrodes whereas graphite and IrO2 / TaO2/RuO2 coated Ti electrodes were tried for electro-oxidation. The degradation of dyes such as CI reactive blue 221 and CI Acid orange 10, phenol based tannins and phenolics such as resorcinol, pyrogallol, catechol and phloroglucinol was studied both by electrocoagulation and electro-oxidation techniques. The decolourization and degradation of the dye molecules was monitored by UV-Visible spectrophotometer and the mineralization trend of all these compounds was followed by chemical oxygen demand (COD) and total organic carbon (TOC) measurements. The effect of operating parameters such as nature of the electrolyte, pH, and applied current density were discussed. The generation of chlorine based insitu oxidants has been confirmed by cyclic voltammetric technique. Electro-oxidation of the dyes and tannin molecules was evaluated and found that the graphite material was effective to achieve the complete mineralization. Although, IrO2 / TaO2/RuO2 coated Ti anode is chemically inert and structurally stable, it fails to generate more molecular oxygen and hydroxyl radicals. The purification of textile and tannery effluent was successfully achieved by electrochemical treatment

Electroflotation-A critical review

Problems related to processing of fine particles and separation of minerals by electro-flotation was described

Treatment of pharmaceutically active compounds by electrooxidation using boron doped diamond and platinum anodes

Clean and hygiene water is a critical environmental issue that touches the life of every human being. In recent years, presence of some pharmaceutical compounds and their metabolites in surface and ground water has become a potential health risk to human beings. Non-steroidal anti-inflammatory drugs (NSAID) are prescribed for muscle pain and inflammatory rheumatic disorders. Ketoprofen one of the NSAIOs, is categorized as a pharmaceutically active compound which resists both the abiotic and biotic degradation. Similarly, P-blockers are a class of drugs used for various indications particularly to control high blood pressure, anti-angina and cardiovascular diseases. One among the P-blockers, atenolol is most toxic to humans and aquatic organisms. The presence of both ketoprofen and atenolol in ground water has been reported at concentrations up to 10 figlL. A bench scale study was carried out to treat synthetically prepared pharmaceutical compounds (ketoprofen and atenolol) contaminated water in lower concentrations (fig/I) using boron doped diamond (BOD) and platinum anodes. The results were explained in terms of in situ generated of hydroxyl radical COH), peroxodisulfate (S20t), and active chlorine species (CI2, ocr and HOCI). The physisorbed 'OH on BOD was observed to trigger the combustion of pollutant molecules in to CO2 and H20. The BOD anode was found to be effective in the presence ofNa2S04 whereas Pt yields better removal in the presence of NaCI. The influence of electrolyte pH on the mineralization of ketoprofen molecules was found to be insignificant

Studies on the adsorption of arsenic on Cali[6]arene.

p-tert-butyl calix[6]arene (PTC6) was synthesized and characterized by solid- and liquid-state NMR and LC-MS techniques. The adsorption of arsenite and arsenate on calix[6]arene under different pH conditions and adsorbate doses was studied. The maximum adsorption of arsenic species on calix[6]arene was observed around neutral pH and the adsorption density of As (III) was higher than that of As (V). The adsorption of neutral H3AsO3 and negatively charged H2AsOS4 molecules on calix[6]arene was attributed to the condensation reaction between hydroxyl groups of PTC6 and arsenic species. The complexation of arsenite with phenolic oxygen was confirmed by solid-state 13C NMR CP-MAS. Exo attack mechanism was proposed to describe the interaction of arsenous and arsenic acid molecules with PTC6. The specific interaction between calix[6]arene and arsenic species was further substantiated by zeta-potential (z-potential) measurements and free energy of adsorption. The free energy of adsorption (Gads) estimated from Stern–Grahame equation was found to be 25 kJ/mole for As (III) and 19 kJ/mole for As (V)

Adsorption of Oleic Acid on Calcium Minerals

Adsorption of oleic acid on nuorite and calcite was studied by adsorption isotherms and Electro kinetic measurements. The adsorption of oleic acid on calcium minerals was observed to proceed initially by monolayer formation at lower concentrations followed by the physical adsorption of hydrocarbon chains in the second layer and finally the precipitated calcium oleate at higher concentrations. Compared to calcite. oleic acid was found to adsorb on fluorite at very low equilibrium concentrations. From the zeta potential measurements. the iso electric point (iep) values of fluorite and calcite are found to be 10.5 and 8,5 respectively. In presence of oleic acid the iep values of fluorite and calcite are shifted to 3.0 and 5.8 indicating specific chemical-interaction between surface calcium and oleate ions. The Free energy of adsorption was calculated from adsorption and Zetapotential measurements. The sign and magnitude of free energy of adsorption suggest the chemisorption of oleic acid on fluorite