About reactions..?

Question

i work in a wastewater treatment plant, we treat lead in water. does lead sulfate, lead chloride and lead ions react with hydrochloric acid?

we treat it by adding caustic soda to form lead hydroxide, does does lead sulfate and lead chloride react with caustic soda to form lead hydroxide?

then we add ferric sulfate as a coagulant, does lead sulfate, lead chloride and lead hydroxide react with ferric sulfate?

lead compounds are insoluble to water right?

we also add an anionic polymer to make the flocs more heavy to settle, but it does not work, you can see suspended flocs in the clarifier, does too much polymer affect the formation of flocs?

too much ferric sulfate makes the water yellowish.

we maintain the pH from 6 to 9.

and lead from about 6ppm to 0.2 ppm.

and the rate is 150 gpm.

and i think the flow is too much.

Answer 1

The hydroxide is added to form lead hydroxide precipitate in the species that are subject to this (lead ions).  If the lead is in colloid or organic forms, it doesn't really help.  The ferric is added to get out the colloid and organic forms, then the polymer is added to floc all of it together for removal.  If it isn't working then your dosages and/or you are using the wrong polymer.  Only lab testing on a regular basis will give you this info.  The pH should be maintained between 8-8.5 for this system as an initial target.

Answer 2

well i m not sure but i''ll certainly give it a try.......lead chloride won't react wid HCl but da other two will.............................yes lead sulphate and lead chloride will yield lead hydroxide when reacted with caustic soda.................................lea... sulfate wont react wid ferric sulphate but da other 2 probably will