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Results of the Study

Physicochemical Properties of Sorbents on the Basis of Rice Husk and Apricot Stones Prepared at Different Carbonization Temperatures

Basis of Rice Husk and Apricot Stones Prepared at Different Carbonization Temperature

The properties of the prepared CC depend on the characteristics of the corresponding raw material, method of activation, and changes in its conditions. So, if in the process of chemical activation of non-carbonized raw material coal is prepared with high activity and relatively wide micropores, but contaminated with inorganic additives that are used in the manufacturing process, then the same raw material, first subjected to pyrolysis and further activated by steam, provides the product without foreign impurities, containing mainly pores [37]. Structure of the material, morphology of the elements, shape and dimensions of pores determine the specific surface area and permeability. Analysis of literature data shows that by modifying or changing the active sites due to carbonization, it is possible to purposefully modify the surface of hydrophilic adsorbents by carbon, imparting to them hydrophilic- hydrophobic and hydrophilic properties and retaining the porous structure of the raw material.

Effect of High-Temperature Carbonization of Rice Husk and Apricot Stones on the Change in the Mass of Raw Material and Its Carbon Content

The change in the mass of RH and AS in the process of carbonization, which was carried out in a rotating steel reactor (2 rpm) under argon flow, was studied. The process time was 60 min at temperatures between 100 and 900°C. After heat treatment, the reactor was cooled to room temperature, purging with argon.

The results are shown in Fig. 2.2.

Dynamics of change in the mass of RH and AS in the carbonization process at various temperatures

Figure 2.2 Dynamics of change in the mass of RH and AS in the carbonization process at various temperatures.

Beginning at 100°C, when the mass loss for RH is 3% and 5.7% for AS, this parameter increases, and at carbonization temperature of 200°C it reaches 17% for RH, 7.3% for AS. As can be seen from the figure, the main mass loss occurs in the temperature range of 200 to 700°C. When the temperature is raised up to 300°C, the mass of the materials (RH, AS) decreases by 21% and 26%, respectively. This value is 23-43% for RH and 43-66% for AS in the temperature range of 400 to 700°C. At 800°C the mass loss for RH is 48%, and for AS it is 67%, i.e., there is a tendency to stabilize the mass of CC.

A similar character of the carbonization process flow was described in [38], where the authors have established that with the temperature rise, the obtained activated carbon is increasingly enriched with carbon, while the evolution of volatile products is also visually observed.

We have carried out an elemental analysis of RH and AS, carbonized at different temperatures. According to the results shown in Fig. 2.3, the carbon content in RH-based sorbents at 700-750°C is 61.2-61.9%, for AS these values are of 61.2-63.3%. Carbonization increases the carbon content, and at carbonization temperature of 800°C it is 62.3% for RH and 64.5% for AS.

Structural diagram of functional groups formed on the surface of carbonized materials

Figure 2.3 Structural diagram of functional groups formed on the surface of carbonized materials. (1) Phenolic (hydroxyl) group, (2) carbonyl (quinoid) group, (3) carboxyl group, (4) ether group, (5) enol group, (6-8) different types of lactone groups

 
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