One Question per Day in Applied Chemistry (9-9)

1. Activated carbon aspect 2. Adsorbate aspect 3. Conditions aspect

I. Properties of activated carbon ； II. Properties of the adsorbate (solute or pollutant) ； III. Effect of solution pH ； IV. Effect of solution temperature ； V. Influence of the coexistence of multiple adsorbates ； VI. Adsorption operating conditions

Particle size, viscosity, temperature, pH value of the treatment liquid, molecular weight of the adsorbed substance, stirring conditions

There are three factors that affect adsorption: A. Regarding activated carbon, an ideal type should have an internal surface that can accommodate the maximum weight of adsorbate within its pores, as well as a high pore volume. Activated carbon with many micropores tends to adsorb small molecules, while activated carbon with many macropores tends to adsorb larger molecules. Therefore, the data on total surface area and pore volume cannot be used to evaluate the potential effectiveness of activated carbon. B. Regarding the adsorbate, the adsorption of organic substances generally increases as their molecular weight increases, until the molecules become too large to fit into the pores of the carbon. Non-polar organic compounds are more easily adsorbed from aqueous solutions than polar ones; the presence of other organic compounds can affect this adsorption process, while inorganic compounds are generally not easily adsorbed. Gases that are easy to liquefy or have high boiling points are more easily adsorbed. In a mixed gas, gases that are easily adsorbed in their pure state are adsorbed first. Regarding condition C, temperature affects the diffusion rate and adsorption equilibrium. The diffusion rate is related to viscosity; increasing the temperature raises the diffusion rate and accelerates reaching equilibrium, but the final amount of adsorption is also lower. As pressure increases, the amount of gas that can be adsorbed increases, especially for gases with low adsorption capacity at normal pressure; this is the principle behind pressure swing adsorption. The pH value affects the adsorption of colored substances in solution. Many colored compounds change their structure and color at different pH values; when the same solution is treated with the same activated carbon at various pH levels, better adsorption generally occurs at lower pH values.

①Properties of activated carbon adsorbents: the greater their surface area, the stronger their adsorption capacity； Activated carbon is a non-polar molecule that readily adsorbs non-polar or highly non-polar adsorbates ； The size of the activated carbon adsorbent particles, the structure and distribution of their pores, as well as their surface chemical properties, all have a significant impact on adsorption. ②The properties of the adsorbate depend on its solubility, surface free energy, polarity, the size and degree of unsaturation of the adsorbate molecules, as well as the concentration of the adsorbed substances. ③ pH value of wastewater: Activated carbon generally exhibits a higher adsorption capacity in acidic solutions compared to alkaline solutions. The pH value affects the state of the adsorbate in water as well as its solubility, thereby influencing the adsorption efficiency. ④Co-existing substances: When multiple adsorbates are present, the adsorption capacity of activated carbon for a particular adsorbate is lower than when that adsorbate is present alone. ⑤ Temperature: Temperature has little effect on the adsorption capacity of activated carbon. ⑥ Contact time: It is necessary to ensure that there is sufficient contact time between activated carbon and the adsorbate, so that adsorption equilibrium can be achieved and the adsorption capacity can be fully utilized.

1. Properties of activated carbon, such as specific surface area 2. Adsorbates, such as solubility and polarity 3. Solution pH

1. Structure and properties of activated carbon. . 2. Properties of the adsorbed organic matter: Concentration of organic matter in water, temperature and co-existing substances, contact time, pH value

The greater its surface area, the stronger its adsorption capacity； Activated carbon is a non-polar molecule that readily adsorbs non-polar or highly non-polar adsorbates ； The size of the activated carbon adsorbent particles, the structure and distribution of their pores, as well as their surface chemical properties, all have a significant impact on adsorption.

Properties of activated carbon; properties and concentration of the substances to be adsorbed; pH value of wastewater; suspended solid content and other characteristics; contact system and operation mode, etc.

1. Regarding activated carbon, an ideal type should possess an inner surface that can accommodate the maximum weight of adsorbate within its pores, as well as a high pore volume. Activated carbon with many micropores tends to adsorb small molecules, while activated carbon with many macropores tends to adsorb larger molecules. Therefore, the data on total surface area and pore volume cannot be used to evaluate the potential effectiveness of activated carbon. 2. Regarding the adsorbate, the adsorption of organic substances generally increases as their molecular weight increases, until the molecules become too large to fit into the pores of the carbon. Non-polar organic compounds are more easily adsorbed from aqueous solutions than polar ones; the presence of other organic compounds can affect this adsorption process, while inorganic compounds are generally not easily adsorbed. Gases that are easy to liquefy or have high boiling points are more easily adsorbed. In a mixed gas, gases that are easily adsorbed in their pure state are adsorbed first. 3. In terms of conditions, temperature affects the diffusion rate and adsorption equilibrium. The diffusion rate is related to viscosity; increasing the temperature raises the diffusion rate and accelerates reaching equilibrium, but the final amount of adsorption is also lower. As pressure increases, the amount of gas that can be adsorbed increases, especially for gases with low adsorption capacity at normal pressure; this is the principle behind pressure swing adsorption. The pH value affects the adsorption of colored substances in solution. Many colored compounds change their structure and color at different pH values; when the same solution is treated with the same activated carbon at various pH levels, better adsorption generally occurs at lower pH values. Due to the varying activation conditions used in the production of activated carbon, its pH value can differ; to suit various applications, the pH value of activated carbon can be adjusted during manufacturing.