Alkaline pH neutralization
Alkaline pH neutralization
(OP)
Has anyone any experience with neutralizing alkaline wastewaters of 11 - 12 pH for low flows with carbon dioxide or other acidifying techniques?
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Alkaline pH neutralization
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RE: Alkaline pH neutralization
Be careful what you use to neutralize. Remember heat of mixing. Avoid strong acids; consider weak acids.
RE: Alkaline pH neutralization
Hope this helps.
saxon
RE: Alkaline pH neutralization
RE: Alkaline pH neutralization
RE: Alkaline pH neutralization
HX (acid)+BOH (base)>>>BX (salt)+H2O
CO2 may be an effective reactant in your case. Although the amount required for 50,000 gpd flow may be a little high. You'll need to run a titration on the waste water/co2 reactant to see what the curve looks like and the required quantities. In fact, if you check with Carbonic at the following site they will work up the curves for you, do a feasibility study, and design a system for you. That site is:
www.carbonic.com/page%206%20carb%20web.htm
BTW, you'll need to somehow separate the salt that is generated from the neutralization reaction.
Hope this helps.
saxon
RE: Alkaline pH neutralization
RE: Alkaline pH neutralization
RE: Alkaline pH neutralization
Could you help me remember to estimate quantitties of HCl needed to neutralize? The concern we have with HCl is hazardous gas.
RE: Alkaline pH neutralization
For pH 12, [OH-] = 10-2 = 0.01 moles/L
Hence, neutralization will require [H+] = 10-2 = 0.01 moles/L:
OH- + H+ = H2O
As the source for H+, can use technical grade hydrochloric acid (37 wt%, SG 1.19).
Since HCl has FW of 36.46, the hydrochloric acid contains [HCl] = [H+] = 12 moles/L.
Hence, to supply 0.01 mole H+ requires 0.01/12 = 0.000833 L of hydrochloric acid.
To neutralize 1 m3 of alkaline solution would require 0.833 L of hydrochloric acid of this concentration. In order to greatly reduce the HCl(g) pressure, I would use hydrochloric acid of lower concentration, e.g., 30 wt%, if available. For 30 wt% HCl, 1.03 L would be required for neutralization of 1 m3 of alkaline solution.
RE: Alkaline pH neutralization
Perry’s Chemical Engineers’ Handbook gives vapor pressures for aqueous solutions of HCl. At 25oC, the HCl partial pressure varies with solution concentration as follows:
Wt, % PHCl, Torr
28 7.05
30 15.1
32 32.5
34 68.5
36 277
38 515
1 Torr = 1/760 atm = 133.3 Pa
RE: Alkaline pH neutralization
RE: Alkaline pH neutralization
http://www.digital-analysis.com/NeutralizationChemicals.htm
BTW, it is suggested that you retain someone with experience in this area as there are various hazards that can be remediated somewhat through proper design.
While CO2 seems to be somewhat non-hazardous, you should note that
1. It is a toxic gas being handled at a hazardous pressure.
2. As you add CO2, it will be generating solid waste (sludge). The CO2 reacts with the calcium in the water to form CaCO3.
3. You will need equipment for CO2 dilution and mixing. Probably more expensive than using acid.
The most commonly used acid used for neutralizing for this application is H2SO4.
A few questions for you? Why are you running this through a limestone filter? I don't believe that a limestone filter is capable of putting out a pH of 11-12. Limestone filters are usually called neutralizing filters for a reason.