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(4) Sulfuric acid roasting method
This method has the advantages of the roasting method, avoiding the slow conversion reaction speed of the acid leaching method.
The sulfuric acid is evenly mixed into the diatomaceous earth, roasted at a low temperature of 380°C for 1.
5 hours, and then immersed in water to remove iron and aluminum.
Water-soluble matter, the remaining is high-quality diatomaceous earth, after drying to obtain refined soil
.
The disadvantage of this method is that leaching produces acidic wastewater, which requires further treatment
(5) Spin-off selective flocculation method
This purification method is to remove coarse debris minerals by spinning, and then add a selective flocculant to flocculate the particulate clay minerals into coarser clumps, thereby separating the diatom frustules from the clay minerals
.
The process is simple, the equipment investment is small, and the cost is relatively low
(6) Dry gravity chromatography separation method
The essence of this method is to use the difference in the density of detrital minerals, clay minerals and diatom frustules in diatomaceous earth to separate the detrital minerals from clay minerals and diatom frustules through ultrasonic vibration and cyclone separation, so as to achieve the purpose of purification.
Therefore, the selected diatomite should have a water content of less than 5%, a particle size of less than 80 mesh, and an SiO 2 of not less than 70%
.
In the diatomite purified by this method, Al 2 O 3 and Fe 2 O 3 are reduced by the same extent as the acid leaching method
(7) Thermal flotation method
Diatom frustules, clay minerals, and organic carbon particles in diatomaceous earth have different water absorption and heat absorption properties due to their different structures.
Above 65°C, diatom frustules are very active and are easily separated from clay and carbon
.
After aging the original diatomaceous soil, it is broken, pulped, and steamed.
(8) Inorganic modification
Inorganic modification of diatomaceous earth means that by adding inorganic macromolecular modifiers, the dispersed mineral single crystals can form a columnar layered association structure, forming a larger space between the associated particles to accommodate organic macromolecules.
Thereby improving its adsorption capacity for organic matter
.
Method 1: Fe(Cu)/Diatomite
.
The metal Fe(Cu)/diatomite adsorbent was prepared by dipping method
Method 2: Manganese-based modified diatomaceous earth
.
Modified diatomite with sodium hydroxide and manganese chloride to prepare manganese-based modified diatomite (Mn-diatomite)