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Yuan Lei tells you | 10 ways to whiten clay minerals

Release time:

2024-01-29 09:37

 

Yuan Lei tells you | 10 ways to whiten clay minerals

 

Whiteness is one of the most important indicators to measure the economic value of clay minerals and product quality.There are three main factors:

 

  • The first type is caused by organic matter, which is deposited in clay minerals in the form of organic carbon and dyes them black or gray;

  • The second type is caused by Fe, Ti, V, Cr, Cu, Mn and other color-causing elements;

  • The third category is dark minerals caused by clay mineral dyeing, such as biotite, chlorite, etc., usually they have little effect on the whiteness of clay minerals.

 

At present, clay mineral whitening mainly has the following methods:

 

1. Mechanical crushing method

 

Mechanical crushing method is the basis of flotation method and magnetic separation method, by grinding the material to increase the specific surface area of clay minerals, and then use flotation method and magnetic separation method to whiten clay minerals, so as to improve the whiteness of clay minerals.

 

2. Flotation method

 

Flotation method uses the different physical and chemical properties of mineral surface and the difference of mineral floatability to separate impurities, and the commonly used methods are adsorption flotation and double liquid layer flotation. Adsorptive flotation separates impurities from clay minerals by using target chemical reagents to achieve the purpose of whitening.

 

3. Magnetic separation method

 

Magnetic separation is the use of different magnetic field strength to separate magnetic and non-magnetic substances in clay minerals. Because the magnetic properties of ferrous minerals and silicoaluminous minerals are different, the magnetic separation method can separate the iron impurities in the slurry from the clay minerals, reduce the iron content of the clay minerals, and increase the whiteness of the clay minerals.

 

4. Oxidation bleaching method

 

The oxidative bleaching method is a method in which iron impurities in a reduced state are oxidized to water-soluble ferrous ions in an aqueous medium using a strong oxidizing agent (hydrogen peroxide, sodium hypochlorite, potassium permanganate, etc.), and then removed by washing with water. The dark organic matter in clay minerals can also be oxidized to colorless oxides by strong oxidants.

 

The oxidation bleaching method requires high experimental conditions, and the oxidation process is controlled by pH, clay mineral characteristics, temperature, reagent dosage, pulp concentration and bleaching time. Sodium hypochlorite (NaOCl) is often used as a strong oxidant in industrial production to oxidize pyrite in a weak acidic medium.

 

5. Reduction bleaching method

 

Reductive bleaching is usually used to remove insoluble ferric iron from clay minerals, and the most commonly used reducing agent is Na2S2O4(insurance powder).

 

Usually, Na2S2O4When used alone, the bleaching effect of clay minerals is not obvious, which not only causes a lot of waste of chemicals, but also due to Na2S2O4In the acidic environment decomposition of harmful substances caused by environmental pollution. If the bleached clay minerals are not rinsed in time, the bleached product will turn yellow and affect product quality.

 

To solve the Na2S2O4Bleached clay mineral products are prone to yellowing, and an appropriate amount of complexing agent (oxalic acid, etc.) is generally added during the reaction to prevent Fe2 It is oxidized again and then removed by washing with water.

 

6. Acid-soluble bleaching method

 

Acid-soluble bleaching method refers to the use of acid solution (sulfuric acid, hydrochloric acid, oxalic acid, etc.) as a leaching agent to treat clay minerals. The conversion of insoluble compounds to soluble compounds allows the raw minerals to be bleached in a warmed environment.

 

According to the kind of acid solution used, it can be divided into inorganic acid bleaching method and organic acid bleaching method. The effect of acid-soluble bleaching is related to the type of acid solution, pulp concentration, acid concentration, reaction temperature and other factors.

 

7. Acid-soluble hydrogen reduction method

 

Acid-soluble hydrogen reduction method is a new method to improve the whiteness of clay minerals based on acid-soluble method. It is the use of acid and reducing agent to water-insoluble iron oxide into water-soluble ferrous compounds, and then filtered to remove.

 

8. Oxidation-reduction bleaching

 

When iron occurs in a complex state in clay ore, it also contains Fe.3 , Fe2 In the case of coloring substances such as organic matter, it is difficult to whiten clay minerals by oxidation or reduction alone. Different coloring substances in clay minerals can be removed separately by using the oxidation-reduction method.

 

The oxidation-reduction method has a good effect on removing a small amount of star-like and disseminated impurities in clay minerals, and the whiteness increases obviously, but for clay minerals containing a large amount of organic matter, the effect of the oxidation-reduction method on whitening clay minerals is not satisfactory.

 

9. Chlorination roasting method

 

High-temperature chlorine-containing air can convert iron and titanium oxides in clay minerals into gaseous iron chloride salts and titanium chloride salts in a special container. This is due to FeCl3The boiling point of TiCl is 315 ℃.4The boiling point of 136 ℃, with high volatility, can efficiently remove iron, titanium oxide. C is oxidized to CO, CO2So that C and organic matter are separated from clay minerals in the form of gas, and the whiteness of clay minerals is improved.

 

Chlorination roasting can provide an atmosphere for chlorination for the reaction in two ways, using chlorine gas and adding a solid chlorinating agent to metathesis it to produce chlorine gas.

 

10, Microbiological Method

 

Microbial method is a new method to remove iron impurities in clay minerals so as to improve the whiteness, it can make iron oxide (goethite, limonite, etc.) in the iron dissolved by microorganisms, and then the iron impurities contained in clay minerals are removed by rinsing.

 

At present, there are two main microbial treatment technologies: biological oxidation leaching method and biological reduction leaching method:
  • Microbial oxidation leaching method is the use of microbial iron oxide mineral impurities, and then through the method of rinsing and filtering to remove the impurities, Thiobacillus ferrooxidans is the most commonly used bacteria.

  • Microbial reduction leaching method mostly uses Fe3 In the form of insoluble oxides in the environment at pH 7, organic matter is used as the electron donor of microorganisms, and the only electron acceptor is Fe3 When oxidized organic matter continues to provide the energy needed to cultivate microorganisms, the iron reduction reaction will continue.

 

In short, each whitening treatment technology has its own advantages and disadvantages, therefore, the whitening treatment of clay minerals need to choose the best whitening method for different color causes, so as to improve the whiteness of clay minerals comprehensive performance, so that it has a high use value and economic value.

The future development trend should be to combine the characteristics of chemical method, physical method and microbiological method, and combine them organically, not only to play their respective advantages, but also to suppress their respective disadvantages and shortcomings, so as to achieve more excellent whitening effect.

Tell, mineral, clay, bleaching, oxidation, microorganism, whitening, remove, impurity, use

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