Zinc removal in the effluent of a galvanizing plant

[ed666]

We got good results by controlling the pH to 9.5-10 (in a settling tank and taking the solids out to to a filter press) for removing the zinc from the effluent. we were able to achieve 0.1-0.5 mg/L which is quite good (reg is 1 mg/L). We plan to modify the plant and we will double the flow. there is also some talk to use passivisation additive containing phosphoric acid (10-20%) and dipropylamine (CAS 142-84-7) (1-5%).

my questions:

1) I would like to know what is the minimum retention time to achieve a good precipitation of heavy metals, zinc in particular.

2) would the additive with dipropylamine (CAS 142-84-7) and phos acid cause adverse effect on the metal precipitation.

thanks

Eric

 

[bimr]

30 miutes is probably the minimum time.

The additive probably will not help. Suggest you do a bench top test to evaluate.