We know that the distribution of macropores, transition pores and micropores of activated carbon affects the adsorption capacity of activated carbon for specific adsorbed substances. Different adsorption materials should choose activated carbon products with corresponding pore size distribution.
There are many methods to measure the pore size distribution of activated carbon. Before we introduced the mercury intrusion method to measure the pore size distribution of activated carbon. powdered activated carbon wastewater treatment Today we will introduce another commonly used method to measure the pore size distribution of activated carbon—capillary agglomeration method.
At a certain temperature, a certain gas is adsorbed in the cylindrical pores of the solid-phase porous material to form an adsorption layer. As the pressure of the adsorbate gas increases and reaches the critical pressure corresponding to the pore size of a certain size, the adsorption gas undergoes capillary condensation.
The smaller the pore size, the earlier agglomeration occurs; when the relative pressure is 1, all pores are filled with the agglomerated adsorption value. During desorption, the condensed liquid is evaporated in order of pore size from large to small.
The pore of activated carbon is the corresponding cylindrical capillary in the test. The relationship between the pore radius of activated carbon and the vapor pressure, saturated vapor pressure and surface tension of the liquid can be expressed by formulas. bulk activated carbon Converting the adsorption capacity into the liquid volume at the adsorption temperature, the total volume of pores with a radius less than R in the activated carbon can be calculated.
The capillary agglomeration method often uses nitrogen as the adsorbent to determine the pore volume of activated carbon at the temperature of liquid nitrogen. In this case, the capillary agglomeration method can measure the pore size of activated carbon between 2-3mm.