Bisulphite vs Thiosulphate ?
Bisulphite vs Thiosulphate ?
(OP)
Hello,
I'm looking at a very small scale de-chlorination project, we'll be using one of the above but as I've no great experience with either of them I'm fishing for any pro's or cons.
cheers........Chris
I'm looking at a very small scale de-chlorination project, we'll be using one of the above but as I've no great experience with either of them I'm fishing for any pro's or cons.
cheers........Chris





RE: Bisulphite vs Thiosulphate ?
RE: Bisulphite vs Thiosulphate ?
A correction to Barrie66's post.....neither sodium thiosulfate or sodium bisulfite give off SO2, and both offer substantially lower dechlorination treating costs, without the possible handling issues, of H2O2.
Depending on your delivered material costs, sodium bisulfite will probably give the best economics of treatment, although either of your choices will dechlorinate suitably.
Orenda
Orenda
RE: Bisulphite vs Thiosulphate ?
Sodium thiosulfate is a colorless, transparent crystal widely used by municipalities for dechlorination. It undergoes multiple reactions with free and combined chlorine, depending on solution pH. Reaction with chlorine yields the following:
Na2S2O3 + 4HOCl + H2O > 2NaHSO4 + 4HCl
Na2S2O3 + HOCl > Na2SO4 + S + HCl
2Na2S2O3 + HOCl > Na2S4O6 + NaCl + NaOH
On a weight-to-weight basis, approximately 2.25 parts of sodium thiosulfate are required to remove one part of chlorine. It should be noted that the thiosulfate reduction depends quite strongly on pH. Sodium thiosulfate is a reducing agent. However, it scavenges less oxygen than sodium sulfite.
Sodium thiosulfate is a skin, eye, nose and throat irritant. It has a NFPA Rating of 1,0, 0 for health, fire and reactivity, respectively. An EPA toxicity study indicated that sodium thiosulfate is not very toxic to aquatic species. Sodium thiosulfate may react slowly with chlorine under some conditions, and requires more time for dechlorination than most dechlorination chemicals.
Sodium sulfite is another dechlorinating agent that is widely used. Sodium sulfite is a skin, eye, nose and throat irritant. It has a NFPA Rating of 2,0, 0 for health, fire and reactivity, respectively.
Sodium sulfite is available in powder/crystalline and tablet form. It undergoes the following reaction with free chlorine:
Na2SO3 + HOCl > Na2SO4 + HCl
On a weight-to-weight basis, approximately 1.775 parts of sodium sulfite are required to remove one part of chlorine. Sodium sulfite is a reducing agent and is reported to scavenge more oxygen than sodium thiosulfate.
RE: Bisulphite vs Thiosulphate ?
Hydrae
RE: Bisulphite vs Thiosulphate ?
This means that depending on the application and the use of other sulfate containg compounds, it could be interesting to choose the treatment which produces the least sulfate.
Edwin Muller
KW2 Burau Veritas
www.kw2.nl