Hi all,,
What is the best acid to neutralize caustic soda waste from boiler cleaning in term of efficiency, safety handling and cost??
1. I consider HCl, but it might need huge amount of HCl to neutralize since industrial grade HCl only available 32% solution.
2. 2nd option is H3PO4, with reaction : 3NaOH + H3PO4 = Na3PO4 + H2O. but I wonder if I have enough H3PO4 to complately neutralize NaOH. the reaction result, trisodium phosphate, as far as I know is an alkali salt, which still have alkali pH. Is that correct? does that mean I need more acid?
3. H2SO4, cheap and available in 98% concentration. but I worry Na2SO4 salt will precipitate at boiler tube since it have lower solubility in water than other salt.
Please give me some advice.