CS243367B1 - Method of phosphorus removal from zirkonium dioxide - Google Patents

Abstract

A method for removing phosphorus with zirconium oxide in the preparation of zirconia starting with zirconium sesame and silica. The invention is based on a common crossing zirconia and silica, containing 10 to 95% silica and 5 and zirconia of zirconia together with at least 25 coal fires when the tap | speed is over 800 ° C displaced, volatilized in steam and carbon vyhoří. The invention is \ t ayala to remove undesirable phosphorus content in bound zirconia, chi the reactivity of the oxides is removed and also removed adverse effect of phosphorus on product quality with them.

Description

(54) A method for removing phosphorus from zirconia

A process for the removal of phosphorus with zirconium dioxide in the preparation of zirconium compounds starting from a zirconium-silica silica.

The invention consists in the co-annealing of a zirconium-silica mixture containing 10 to 95% by weight of silica and 5 to 90% by weight of zirconia together with at least 25% by weight of carbon, at a tapping rate above 800 ° C. vapors in vapors and carbon burns out.

The invention is ductile in a ceramic duct to remove the unsuspecting phosphorus content of the zirconium oxide constraints, thereby increasing the reactivity of the oxides and also eliminating the adverse effect of phosphorus on the quality of the products prepared therewith.

The invention relates to a process for removing phosphorus and sulfur dioxide in the preparation of sulfonic compounds, starting from a mixture of zirconia and silica.

Zirconium oxide is the most prominent raw material for the preparation of zirconium compounds.

Frequent pilgrims find it in cereal, when they are usually prepared with mixtures of sulfur dioxide and silica by reaction with elevated temperatures.

Examples * are zirconium ceramic pigments. Their quality is largely influenced by the reactivity of the starting sulfur dioxide. If the oxide is poorly reactive, the necessary temperatures and firing times of the products increase.

also a defect in the cost of their preparation and in most cases a decrease in the quality of the product. The reactivity of sulfur dioxide is strongly reduced by phosphorus ions, even if only low concentrations (hundredths of a% by weight) are present.

In the preparation of the sirkon pigments, the reaction of the starting sulfur dioxide, in turn, decreases the reactive color of the product. Zejaána je toau in the case of pltfiant dyed on the principle of disturbances in their sircon structure. E.g. for aurora and yellow sircon pigaents, the colors are partially shifted to red * shades *.

If phosphorus ions are added in larger amounts in the starting zirconia, the saturation of the shade of the malfunction-colored sircon pigaents is significantly reduced, since phosphorus ions are trapped in the pigaent structure as substitute non-staining disorders.

Due to their very small ionic radius, they both preferentially capture, as opposed to larger * staining * ions * (eg vanadium, praseodyau), and these * reduce the possibility of their effective capture.

The presence of phosphorus in sulfur dioxide also does not allow to achieve as high a degree of conversion of zirconium silicate pigaents as when using phosphorus-free oxide. Phosphorus compounds accompany almost all the zirconium minerals used, whether they are zirconium dioxide (beddelyiti mineral or zirconium silicate for the preparation of zirconium products is obtained synthetically from zirconium mineral, part of the phosphorus from the raw material).

Removing phosphorus from sulfur dioxide is a difficult and costly process. Some sulfur dioxide producers use leaching to reduce the phosphorus content of baddelyite mineral.

Acidic solutions containing chloride, nitrate, sulfate, fluoride and ammonium ions reduce the phosphorus content below 1.0% by weight. However, this is a lengthy and material and energy intensive process.

In the case of the preparation of the sircon pigments, there is also a process for partially eliminating the effect of the phosphorus additive in the starting zirconium oxide on the pigment quality, by adding calcium ions to the starting mixture.

Although this procedure is simple and inexpensive to implement, it has a number of disadvantages. This is because other ions are introduced into the system, which then influence the course of the pigment formation reaction and its quality.

The addition of calcium ions in itself reduces the reactivity of the sulfur dioxide.

When used in a necessary excess over the phosphorus present, the increase in the reactivity of the oxide due to the binding of phosphorus ions by calcium ions is at least eliminated.

2 * 3367

Therefore, the amount of their addition should be bound to the exact phosphorus content of the oxide. This is often very volatile and due to the difficulty of its determination is difficult to meet this condition.

In addition, prime calcium ions are trapped in the synthesis of the pigaent. Their presence in the zircon structure then affects the color of the pigment, especially in the case of failure-colored species.

Because of the variation in the phosphorus content of the starting zirconia and of the free calcium ions in the mixture, this effect on the pigment shade is difficult to predict. This reduces the possibility of providing a pigment with a constant color quality.

In the preparation of zirconium compounds, starting from a mixture of zirconia and silica, the method of removing phosphorus from the zirconia according to the invention does not have these drawbacks, characterized in that a mixture of oxides containing 10 to 95% by weight of silica and 5 to 90% by weight % of zirconium, at least 2% by weight, preferably 3 to 7% by weight of carbon is added and the mixture is ironed at a temperature of 800 to 1359 ° C, preferably at a temperature of 850 to 900 ° C.

Indeed, at high temperatures, silica is able to act as a relatively strong acid and displaces phosphorus ions from zirconia in the form of phosphorus pentoxide. However, the temperature of the onset of this process is above 1150 ° C.

However, by the addition of carbon and thus in the firing-forming environment which is a strongly reducing medium, this temperature is lowered and the phosphorus pentoxide is displaced already at 800 to 850 ° C. This is already the temperature commonly used in the synthesis of most zirconium compounds for ceramic purposes.

The phosphorus pentoxide released by the present carbon is immediately reduced to phosphorus, which volatilizes from the mixture and is burnt in the furnace space. The use of higher temperatures for the oxidation of the carbon-oxide mixture is possible, however, it entails higher energy demands.

However, at temperatures above 1350 ° C, the sintering of the mixture, the swelling of the siliceous component, or the reaction of the starting oxides may partly occur. Thus, by burning the mixture of zirconia, silica and carbon, the carbon burns out, the phosphorus is removed from the zirconia and only the mixture of oxides remains.

After cooling, this is only supplemented with the other components necessary for the synthesis of the respective zirconium compound, i.e., mineralizers and chromophores in the case of the synthesis of zircon pigments, and the actual firing is performed for the synthesis of the compound.

An advantage of the process according to the invention is that the method is fast, simple, raw material-free and utilizes temperatures commonly used in the ceramic industry in the synthesis of zirconium compounds. Cross-linking of the oxide mixture can thus be easily realized.

No other compounds were added to the mixture which would adversely affect product quality. The carbon used, which burns on ignition, can be taken in any excess, and the effective removal of phosphorus is thus achieved even with only a very approximate, not exact knowledge of its initial content in zirconium dioxide.

Example 1

Of the mixture containing 55 g zirconium dioxide (containing 1.49% phosphorus by weight), g silica, 5 g ammonium vanadate chromophore and 13 g mineralizer consisting of * g sodium fluoride and 9 g sodium chloride, was fired at 850 ° C. for 3 h

2 * 3367 * prepared blue zircon pigment. It exhibited a mauve odaline and its alupene «reacting to silicon dioxide« iricon dioxide was 83.4%.

In the process according to the invention, the basic starting oxides, in an amount of 55 g of zirconia (containing 1.49% phosphorus by weight) and 27 g of silica, were mixed with 5 g of carbon and the mixture was annealed at 850 ° C for 30 min.

After cooling, the phosphorus content was determined to be 0.006% by weight, which, when converted to the zirconia present in the mixture, represented a phosphorus content of 0.009% by weight.

The mixture was then mixed with 5 g of ammonium vanadate chromophore and 13 g of mineral salt, consisting of 4 g of sodium fluoride and 9 g of sodium chloride, and the resulting mixture was fired at 850 ° C for 3 h to give a blue sircon pigment.

The pigment was deep blue beside the undesirable blue-violet hue and its degree of conversion to zirconium silicate was 93.2%,

Example 1 a d 2

Of the mixture containing 60 g of zirconia (containing 0.98% phosphorus by weight), g of silica, 3 g of praseodymium oxide chromophore and 7 g of mineralizer consisting of 3 g of sodium fluoride and 4 g of sodium chloride, was fired at 900 ° C. For 3 h a yellow sirkon pigment was produced which showed a reddish shade.

Then, according to the process of the invention, the basic starting oxides, in an amount of 60 g of zirconia (containing 0.98% phosphorus by weight) and 10 g of silica, were mixed with 3 g of carbon and the mixture was annealed at 900 ° C for 20 min.

After cooling, the phosphorus content was determined to be 0.004% by weight, which, when converted to the zirconia present in the mixture, represented a phosphorus content of 0.006% by weight in the oxide.

3 g of praseodymium oxide chromophore and 7 g of mineralizer consisting of 3 g of sodium fluoride and 4 g of sodium chloride were then added to the mixture, and the resulting mixture was fired at 900 ° C for 3 h.

Example 3

From a mixture containing 47 g of zirconium (containing 1,49% by weight of phosphorus), 25 g of silicon dioxide, 8 g of ferric oxide-hydroxide (FeO (OH)) and 20 g of mineralizer consisting of 11 g of sodium fluoride, 6 g of chloride sodium nitrate and 3 g of potassium nitrate, a pink sycon pigment was prepared by firing at 850 ° C for 2 h. The degree of pigment conversion to zirconium silicate was <78.3%.

Then, according to the process of the invention, the starting oxides, 47 g of zirconia (containing 1.49% phosphorus, and 25 g of silica), were mixed with 5 g of carbon and the mixture was annealed at 900 ° C for 30 min.

After cooling, the phosphorus content was determined to be 0.005% by weight, which, when converted to the zirconia present in the mixture, represents 0.008% by weight of the phosphorus in the oxide. 8 g of ferric oxide-hydroxide (Pe0 (0d)) and 20 g of mineralizer consisting of 11 g of sodium fluoride, 6 g of sodium chloride and 3 g of potassium nitrate were then added to the mixture and the resulting mixture was baked at 850 ° C for The degree of reaction of the pigment to zirconium silicate was 85.4%.

Claims (2)

SUBJECT OF THE INVENTION Process for removing phosphorus from zirconia in the preparation of zirconium compounds from the emission of zirconia and silicon dioxide, characterized in that for each oxide mixture containing 0 to 95% by weight of silica and 5 to 90% by weight of zirconia, at least 2% by weight, preferably 3 to 7% by weight, of carbon and the mixture are yellowed at a temperature of 800 to 350 ° C, preferably at a temperature of 850 to 900 ° C.