Flotation of calcareous Mussorie phosphate ore

Separation of Mussorie rock phosphate (P₂O₅ = 20%) from Uttar Pradesh, India, containing pyrite, calcite and other carbonaceous impurities by flotation has been successfully attempted to upgrade the phosphate values. Based on Hallimond cell flotation results of single and synthetic mineral mixtures of calcite and apatite using oleic acid and potassium phosphate, conditions were obtained for the separation of calcite from apatite which is considered to be the most difficult step in the beneficiation of calcareous phosphates. Further studies using 250 g of the mineral (?60 +150 and ?150 mesh fractions, deslimed) in laboratory size Fagergren subaeration machine employed a stagewise flotation viz. carbonaceous materials using terpineol, pyrite using potassium-ethyl xanthate and calcite using oleic acid respectively. Separation was, however, found to be unsatisfactory in the absence of a depressant.Among starch, hydrofluosilicic acid and dipotassium hydrogen phosphate, which were tried as depressants for apatite in the final flotation stage, dipotassium hydrogen phosphate proved to be superior to others. However, the tests with the above fractions did not yield the required grade. This was possibly due to insufficient liberation of the phosphate mineral from the ore body and different experimental conditions due to scale up operations. Experiments conducted using ?200 mesh deslimed fractions has yielded an acceptable grade of 27.6% P₂O₅ with a recovery of about 60%. The results have been explained in terms of the specific adsorption characteristics of phosphate ions on apatite and the liberation size of the mineral.     

The role of ionomolecular surfactant complexes in flotation

The formation of highly surface-active ionomolecular complexes has been suggested recently to be a phenomenon that governs the pH-dependence of hematite flotation using oleate. The differential thermogravimetric work reported in the literature on alkylamine-alkylamine hydrochloride mixtures shows complete complexing of them when present in equimolar amounts. The pH dependence of quartz flotation using amine, speculated in the past to be due to various mechanisms, is discussed in the light of these results. The additional correlation obtained for flotation with surfactant complex formation suggests the role of such complexes in froth flotation to be of wide application.     

Organization of amphiphiles, Part VIII: Role of polyoxyethylated alkylphenols in optimizing the beneficiation of hydrophilic mineral

The floatability of silica has been determined by adsorbing various concentrations of a series of polyoxyethylated nonyl and octyl alkyl phenols of varying oxyethylene units (10–40 units) to investigate the role of adsorbed layer. It is seen that the floatability of silica increases with increase in concentration till a maximum of  90% in premicellar region and then decrease to minimum of 40–45% in all cases in spite of the significant differences in adsorption densities. Zeta potential measurement reveals that a thin oxyethylene layer is formed at silica–water interface masking silica surface (Pramila K. Misra, P. Somasundaran, J. Surf. Deterg., Vol. 7, 2004, 373). This layer with oxyethylene units lying on silica surface and alkyl chain dangling to the bulk solution provides the same extent of hydrophobicity. The decrease in flotation recovery has been attributed to increase in the solvent hydrophobicity due to formation of premicellar aggregates and micelles.     

Effect of pretreatment of the electrokinetic properties of quartz

Effects of various commonly used pretreatments such as desliming, ultrasonic scrubbing and leaching with dilute nitric, hydrofluoric and sodium hydroxide solutions on the electrokinetic properties of quartz in aqueous solutions are reported. The study showed that treatments with various reagents often used in mineral processing research in the past to clean minerals can affect, sometimes severly, the electrokinetic properties of quartz. The change in these properties during subsequent aging is also found to be governed by the type of treatment used. This study also shows the need in mineral research for standardization of mineral preparation techniques in order that the discrepancy in data reported for surface properties in literature can be minimized.     

Subsidence of suspensions of phosphatic slime and its major constituents

The dewatering of stable phosphatic clay suspensions resulting from the processing of phosphate rock is a problem of much practical and theoretical significance. In order to investigàte this aspect, the sedimentation behavior of suspensions of major components of phosphatic slimes, or morphologically similar meterials, both separately and in appropriate combinations, was studied. Systems which behaved very similarly to phosphatic slimes were termed “model systems”. Study of these model systems revealed that the minerals montmorillonite and attapulgite, with their special properties — morphology, swelling, ion exchange capacity, surface charge, and viscosity — were responsible for the behavior of phosphatic slimes.Mechanisms by which coarse particles and micro air bubbles enhance the dewatering of the phosphatic slimes are reviewed. In both cases, creation of paths for water seepage as a result of their movement is considered to be mainly responsible for the enhanced subsidence of the slurry.     

Grinding of quartz in amine solutions

This study, initiated to investigate the effect of additions of surface active reagents on the wet-grinding of ores, has shown that improved grinding can be obtained at certain levels of amine concentration and pH. At some other levels, amine addition can also produce deleterious effects. The observed effects are discussed with the help of data obtained for flocculation and zeta potential of corresponding quartz/amine systems and those normally obtained for flotation. In addition, results of a photographic study of the milling process has been helpful in the study of the above effects. Most importantly, microscopic examination of the ground product (treated with dispersant and sieved) has clearly shown the possibilities for the existence of major experimental artifacts in the past works. Examination of the product under microscope is necessary to guarantee dispersion, especially if the system has been contacted with a surfactant or polymer.     

Study on seismic performance enhancement in bridges based on factorial analysis

The seismic performance of bridges depends on the ductile behavior of its column, as the deck and other substructural components except pile foundations are normally designed to be elastic to facilitate bridge retrofitting.Codes such as AASHTO, Caltrans, IRC: 112 etc.give guidelines for the seismic performance enhancement of columns through ductile detailing.In the present study, a methodology for the seismic performance enhancement of bridges is discussed by using a "Parameter-Based Influence Factor"(PIF) developed from factorial analysis.The parameters considered in the factorial analysis are: percentage of longitudinal reinforcement(P_t), compressive strength of concrete(f'_c), yield strength of steel(f_y), spacing of lateral ties(S) and column height(H).The influence of each parameter and their combination on the limit states considered is estimated.Pushover analysis is used to evaluate the capacity of columns, considering shear failure criteria.A total of 243(3~5 combinations) analysis results are compiled to develop ‘PIF’ used in the performance enhancement process.The study also encompasses other sub-objectives such as evaluating the discrepancies in using the Importance Factor(I) in designing bridges of varied functional importance; and estimating the aspect ratio and slenderness ratio values of bridge columns for its initial sizing.     

Selective flocculation of synthetic mineral mixtures using modified polymers

The role of the presence of active groups in polymers and operating variables such as conditioning time in producing flocculation in single and mixed mineral slimes made of hematite, quartz and chalcopyrite is examined at different conditions of pH. Selective flocculation was achieved on the basis of results obtained for single mineral systems as, for example, in the case of hematite—quartz mixtures using sulfonated polymer. Flocculation was found to go through a maximum as the mineral was conditioned with the polymer solution. Interestingly, the times of maximum flocculation for various minerals were sufficiently different from each other so that it could be considered as a potential factor for achieving selectivity. Also, cleaning of the selectively flocculated product by simple redispersion in water improved the separation. Electrokinetic studies conducted to study the mechanisms involved provided indication for the shift of shear plane.     

Petroleum hydrocarbon distribution in continental shelf region of southeast coast of India

In the surface sediment samples collected from 7 transects in the continental shelf region off Karaikkal, Parangipettai, Cuddalore-SIPCOT, Cheyyur, Chennai, Tammenapatanam and Singarayakonda in the s...