Igneous Phosphate Research Articles

Floatability of apatites and gangue minerals of an igneous phosphate ore

The presence of different apatite types is characteristic of igneous phosphate deposits. The flotation performances of primary and secondary apatites occurring in phoscorites, weathered phoscorites and pyroxenites were investigated. As a contribution towards the understanding of the behaviour of the flotation system, the major gangue minerals were also selected for the study: quartz, a pyroxene (augite), altered micas (vermiculite), calcite and dolomite. Zeta potential curves for all the above mentioned mineral species were determined as a function of pH, pCa and pMg. Microflotation experiments were performed in a modified Hallimond tube at different pH levels in the presence of sodium oleate as collector and corn starch as depressant.

Release of phosphorous from igneous phosphate rock through bioturbation: a low-cost approach for phosphorous fertilization in fish farms

The influence of bioturbation caused by common carp fry was treated in 24 transparent polythene jars (5 L each) in the laboratory and in outdoor vats (150 L), increasing the fertilizer value of phosphate rock in eight treatment combinations in triplicate. Input of water soluble reactive phosphate (SRP) was determined to quantify the effects of bioturbation, fish excrements and soil. The level of SRP in water was always lowest in the control series. Introduction of common carp fry resulted in a net increase of 0.009–0.010 mg phosphate g−1day−1 of SRP attributable to the effect of fish excrement. Bioturbation caused by common carp resulted in as high as a 64.8 to 90% influx of phosphate from bottom soil in the presence of phosphate rock but only about 6.3 to 7.2% in the absence of phosphate rock. The bioturbation that occurred in this treatment resulted in a significant release of phosphorous into the overlying water from an apatite source. The results confirm the environment friendly application of phosphate rock in fish-farming ponds at low cost.

Rare earth elements as tracers of sediment contamination by phosphogypsum in the Santos estuary, southern Brazil

In the Cubatão region, southern Brazil, sediments are transported by several rivers from the Serra do Mar Ridge into the Santos estuary. Fertilizer plants have been operating along the margins of one of these rivers (Mogi River) producing a large volume of phosphogypsum, which is stockpiled in nearby areas. Surface sediments of the Mogi River were sampled upstream and downstream in relation to the point where the effluents of the phosphogypsum piles flow into the drainage system. In the vicinity of this point one sediment core was collected. Results show that REE, Ba, Zr and Th concentrations in the non-contaminated sediments are of the same order as those present in the upper continental crust. The contaminated samples present a composition affected by that of the phosphogypsum, marked by a higher concentration of these elements and a stronger degree of REE fractionation. These phosphogypsum characteristics are inherited from the Catalão igneous phosphate ore and were moderately modified by the industrial process of phosphoric acid production. The phosphogypsum signal decreases rapidly downstream, pointing to a limited area of influence of the stacks. The deepest sediments of the core are also free of contamination, representing a time interval prior to the deposition of phosphogypsum wastes on the banks of the estuary.

Comparative utilization of phosphorus from sedimentary and igneous phosphate rock by major biotic components of aquatic ecosystem

Two laboratory experiments were conducted to evaluate the amount of P utilization from two different types of sparingly soluble phosphate rock by aquatic biotic communities. The first type was Mussoorie Phosphate Rock or MPR (sedimentary in origin) and other was Purulia Phosphate Rock or PPR (igneous in origin). The two trials were with eight different treatment combinations. Among various treatments, fish and Chironomid larvae contributed to some extent in increasing the available sediment phosphate content which in turn increased the soluble reactive phosphate (SRP) of overlying water. Concentration of SRP of overlying water decreased in the treatment with zooplanktons. Depletion of SRP of overlying water due to uptake of orthophosphate by Chlorella was also observed. The sedimentary type phosphate rock proved to be more efficient in releasing phosphate than igneous one.

Distribution of natural radionuclides in the production and use of phosphate fertilizers in Brazil

The Brazilian phosphate fertilizer is obtained by wet reaction of igneous phosphate rock with concentrated sulphuric acid, giving as final product, phosphoric acid and dehydrated calcium sulphate (phosphogypsum) as by-products. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP) and diammonium phosphate (DAP). The phosphate rock used as raw material presents in its composition radionuclides of the U and Th natural series. Taking this into account, the main aim of this paper is to evaluate the fluxes of natural radionuclides and radioactive disequilibria involved in the Brazilian industrial process of phosphoric acid production; to determine the content of radioactivity in several commercial fertilizers produced by this industry; to estimate their radiological impact in crop soils and the long term exposure due to their application. Radiological characterization of phosphate rock, phosphogypsum and phosphate fertilizers was performed by alpha and gamma spectrometry. The fertilizer samples, which are derived directly from phosphoric acid, MAP and DAP, presented in their composition low activity concentrations for 226Ra, 228Ra and 210Pb. As for U and Th, the concentrations found in MAP and DAP are more significant, up to 822 and 850 Bq kg −1, respectively. SSP and TSP, which are obtained by mixing phosphoric acid with different amounts of phosphate rock, presented higher concentrations of radionuclides, up to 1158 Bq kg −1 for 238U, 1167 Bq kg −1 for 234U, 1169 Bq kg −1 for 230Th, 879 Bq kg −1 for 226Ra, 1255 Bq kg −1 for 210Pb, 521 Bq kg −1 for 232Th, 246 Bq kg −1 for 228Ra and 302 Bq kg −1 for 228Th. Long term exposure due to successive fertilizer applications was evaluated. Internal doses due to the application of phosphate fertilizer for 10, 50 and 100 years were below 1 mSv y −1, showing that the radiological impact of such practice is negligible.

Natural radioactivity in phosphate rock, phosphogypsum and phosphate fertilizers in Brazil

Phosphate deposits are generally characterized by enhanced radionuclide concentrations compared to natural levels. The mining and processing of this phosphate ore redistribute radionuclides throughout the environment and introduce them into phosphoric acid and phosphogypsum. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), NPK fertilizers and di-calcium phosphate (DCP). Contents of natural radionuclides from thorium and uranium series, 226 Ra, 210 Pb and 228 Ra, were measured in Brazilian igneous phosphate rock, phosphoric acid, phosphogypsum and phosphate fertilizer samples, using high-resolution gamma-spectrometry. Neutron activation analysis was used for the determination of U and Th in the same samples. The fertilizers samples which are derived directly from phosphoric acid, MAP and DAP, presented activity concentrations around the detection limits of the counting system for 226 Ra (<5.0 Bq . kg –1 ), for 228 Ra (<3.0 Bq . kg –1 ) and for 210 Pb (<19 Bq . kg –1 ). As for U and Th, the concentrations found in MAP and DAP are more significant, up to 374 and 250 Bq . kg –1 , respectively. SSP, TSP and NPK, which are obtained by mixing phosphoric acid with different amounts of phosphate rock and NH3, presented higher concentrations of radionuclides, up to 871 Bq . kg –1 for 226 Ra, 283 Bq . kg –1 for 228 Ra, 1255 Bq . kg –1 for 210 Pb, 413 Bq . kg –1 for U and 538 Bq . kg –1 for Th.

Reagents in igneous phosphate ores flotation

The role of reagents utilised in igneous phosphate ores flotation is reviewed. Fatty acids soaps derived from different vegetable species are utilised as collectors. Less expensive species, such as rice and soybean bran oils replaced successfully the more expensive tall oil as the source for the apatite collector. Synthetic collectors such as sarcosinate and sulphosuccinate are also employed. The collector species plays also the frother role. Corn starch is the gangue depressant. Less pure starches, with oil contents equal to or higher than 3%, may be utilised without the risk of suppressing the froth. Actually they may act as a froth controller due to the fact that the fatty acid soap that plays the frother role is an ionic species, generating thus a voluminous froth. Non ionic ethoxylated surfactants may also be used to control the surface tension of the system. Barite, when present, may be either pre-floated with cetyl-stearyl sodium sulphate or depressed, in the fine apatite flotation circuit, at pH 12.

Accounting for particle movement when assessing the dissolution of slow release fertilizers in field soils

When fine particulate, slow-release fertilizers are applied to pastures, earthworm activity can physically move the particles both horizontally and vertically in the soil. This physical movement needs to be accounted for when researchers attempt to determine the rate of fertilizer dissolution by measuring the quantity of undissolved fertilizer residue remaining in the soil. A hard igneous phosphate rock (Phalaborwa PR) and an inert chromite ore were used as tracers to follow the physical movement of the reactive PR (RPR), NCPR applied to grazed pasture on a Pallic Soil (Aeric Fragiaqualf) isolated in galvanised steel cylindrical cores (150 mm diameter and 100 mm height) with or without nylon mesh sleeve (63 µm) at the bottom. The soil cores were sampled after 113, 270 and 559 days and analysed for PR and chromite residues. Results from both tracers showed that there was a significant movement of particles laterally out of the cores and vertically below 40 mm soil depth. Phalaborwa PR particle movement to 40–60 mm soil depth was 8% in 112 days and 24% in 270 days. Between 270 and 559 days no significant movement of particles was observed. Particle movement appeared to occur in discrete non-continuous events that were associated with the major end-of-autumn peaks in earthworm activity. When corrected for particle movement, the measured rate of NCPR dissolution satisfactorily fitted the rate of dissolution predicted by two models of PR dissolution.

Ion microprobe measurements of 18O/ 16O ratios of phosphate minerals in the Martian meteorites ALH84001 and Los Angeles

Oxygen isotope ratios of merrillite and chlorapatite in the Martian meteorites ALH84001 and Los Angeles have been measured by ion microprobe in multicollector mode. δ 18O values of phosphate minerals measured in situ range from ∼3 to 6‰, and are similar to Martian meteorite whole-rock values, as well as the δ 18O of igneous phosphate on Earth. These results suggest that the primary, abiotic, igneous phosphate reservoir on Mars is similar in oxygen isotopic composition to the basaltic phosphate reservoir on Earth. This is an important first step in the characterization of Martian phosphate reservoirs for the use of δ 18O of phosphate minerals as a biomarker for life on Mars. Cumulative textural, major-element, and isotopic evidence presented here suggest a primary, igneous origin for the phosphates in Los Angeles and ALH84001; textural and chemical evidence suggests that phosphates in ALH84001 were subsequently shock-melted in a later event.

IDENTIFICATION OF COMPOUNDS PRESENT IN SINGLE SUPERPHOSPHATES PRODUCED FROM BRAZILIAN PHOSPHATE ROCKS USING SEM, EDX, AND X-RAY TECHNIQUES

Scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray techniques were used to obtain data about the mineralogical composition of single superphosphates (SSP) produced from apatite concentrates originating from Araxa, Jacupiranga, Catalao, and Tapira igneous phosphate rock deposits. The SSP samples were investigated both in their original form and after leaching with water to remove water-soluble compounds. Results of chemical analysis and instrumental techniques showed that P compounds were still present in the water-leached material. Anhydrite (CaSO 4 with no hydration water) was the main Ca-S component in the SSP samples. Monocalcium phosphate monohydrate [Ca(H 2 PO 4 ) 2 .H 2 O] was identified in the original but not in the water-leached samples. Results of SEM, EDX, and X-ray confirmed the presence of crystals of triiron (III) potassium octahydrogen hexaphosphate hexahydrate [Fe 3 KH 8 (PO 4 ) 6 .6H 2 O] in the SSP. The results of SEM and EDX analyses suggested that the compounds triiron (III) nonahydrogen hexaphosphate hexahydrate [Fe 3 H 9 (PO 4 ) 6 .6H 2 O], triiron (III) 15-hydrogen octaphosphate tetrahydrate [Fe 3 H 15 (PO 4 ) 8 .4H 2 O], triiron (III) potassium 14-hydrogen octaphosphate tetrahydrate [Fe 3 KH 14 (PO 4 ) 8 .4H 2 O], and barium sulfate (BaSO 4 ) were present in some of the SSP samples. Use of SEM, EDX, and X-ray techniques was shown to be adequate for precise characterization of compounds present in the SSP studied, which will help to understand further the plant availability of the phosphorus contained (especially) in the water-insoluble P fraction of this fertilizer.

Soil fertility studies with compost and igneous phosphate rock amendments in Malawi

Soil fertility studies with compost and igneous phosphate rock amendments in Malawi

The economic geology and development of igneous phosphate deposits in Europe and the USSR

Phosphate deposits of igneous origin contributed some 19 million metric tons to the total world marketable output of phosphate rock of nearly 116 million metric tons in 1977. Most of this was produced in the USSR from the Khibiny Complex, Kola Peninsula. There was production at the neighboring Kovdor Complex and, in northern Europe, at Graengesberg in central Sweden. In Europe and the USSR, four other igneous complexes are known to be at various stages of development as commercial sources of phosphate.Most of the igneous complexes reviewed are characterized by assemblages of alkali-rich intermediate and ultrabasic rocks and carbonatite, the intrusions being generally of Siluro-Devonian or Carbo-Permian age, with the notable exception of the Precambrian Siilinjaervi carbonatite in central Finland. The complexes are also invariably located close to or within regional linear fracture zones.Associated with the igneous complexes in Europe and the USSR is an interesting variety of apatite-bearing rocks. In addition to the remarkable nepheline-apatite orebodies of the Khibiny Complex, there are other deposits, including apatite-forsterite and apatite-forsterite-magnetite rocks, as well as apatite-bearing carbonatites and, particularly, their weathering derivatives, which have their commercially important counterparts in other parts of the world. The phosphate mineral is invariably fluorapatite, with francolite occurring prominently in weathered zones. Other minerals of value or potential economic importance include magnetite, vermiculite, baddeleyite, bastnaesite, pyrochlore, chalcopyrite, fluorite, and barite.