Hi Olusegun,

Here is a schematic of the cadmium reduction column I am using: 

http://www.norweco.com/html/lab/test_methods/Fig%204500-NO3-1.jpg

I cannot precisely set the flow rate value because the flow is enabled and disabled using a stopcock. As for the cadmium granules, I used Sigma-Aldrich's 30-80 mesh cadmium granules and I filled the column to 18.5 cm using these granules. The shaded region of the column represents these granules.

I think you have to check whether there are bubbles of gases in the column.

@Fikrat,

I already checked for bubbles. I made sure there were none. I added the water into the column first. I then coated the cadmium granules with copper sulfate solution. Afterwards, I introduced the granules into the water-filled column. No bubbles were formed after that step either.

Hi paul,

  I think to increase the flow of water from the column must be increased permeability.you can increase the grain size and that  increases channel space and thus increasing the amount of water flowing.

@Olusegun

How do I check for the pressure drop in the column? 

Also, would the reduction efficiency of the process decrease if I decreased the amount of granules I add into the column? Would decreasing the amount of granules increase flow rate?