calculation for CN destruction and As precipitation

[MANIAM]

Please give me some information on how to calculate effluent concentration of cyanide and arsenic in wastewater treatment which relate the flow rate, detention time and dosage of reagents..For cyanide destruction we use hydrogen peroxide and for arsenic precipitation we use ferric chloride.

thank you.

 

[DeltaCascade]

Pretty wide-open question. You may want to break it down to smaller more specific question, to save us from having to "reinvent the wheel" or design an entire and imaginary system for you...which likely won't fit yor needs. What are process details? Good luck.

 

[MANIAM]

To DeltaCascade

Thank you for your response. Actually my project is to develop a tool/model for cyanide destruction using H2O2 and arsenic precipitation using FeCl3. The problem is I don’t have any formulas that can relate flow rate, reagent dosage, design parameters and influent and effluent concentrations.Please give me your e-mail address to send the schematic of the plant and all the information I have.

Thanks in advance

Sincerely
Maniam

 

[PBroad]

As DeltaCascade says this is a very wide subject. Not only do you need to destroy the cyanide but also any metal cyanide complexes. For full details see "Chemistry of Gold Extraction" by Marsden House ISBN 013 131517X this is close to being the bible.page 494 has all the appropiate equations. Talk to Degussa as a cyanide supplier or Dupont the addresses I have are Canadian Phipip Matthews 905 332 6633 or Jack Toof 403 278 8731, or your peroxide supplier. Recent unbiased reports suggest that the INCO SO2 process is cheaper than peroxide, especially in large amounts but Stefan Trapp at Tech, Univ of Denmark has calculated that a single willow will absorb 500kg CN/yr and convert it to amino-acid (aspartagine) so bio-filters are an even cheaper option for more info contact me at broadfam@ntl.sympatico.ca as a fellow gold recovery engineer or Stefan at sst@er.dtu.dk

 

[DeltaCascade]

Yes, looks like you need the tools to make the tool.

Hmmm ... i'd be tempted to consider bleach instead of H2O2 ... Looks like you need a system designed from scratch, yet you don't know what you are treating? But you have plant schematics? Maybe you also have plant manuals? Or is this a school homework assignment?

http://www.DeltaCascade.com

 

[nbucska]

I wonder if the ferric chloride won't form a complex with the cyanide which may not react with H2O2 ?
<nbucska@pcperipherals.com>

 

[PBroad]

To &quot;nbucska&quot;, As I am not realy sure what Maniam is trying to achieve I can't give you a full answer, but there is merit in your question. Arsenic is soluable if and when it exceeds the iron (Fe) chemically by 4:1, thus extra iron will precititate As. However, ferric iron is insoluable at any pH 4 - 12 thus any surplus will precipitate, and not be available to react with the cyanide, bi-valent iron would react. A further problem is that ferric chloride is very, very corrosive. Stainless Steel lasts mere minutes, only plastic, or titanium alloys are safe. Thus Ferric Chloride is only used if the treated water is not being recycled, with Ferric sulphate being prefered.

However, one needs a better insight of what Maniam aims to do. Even as engineers we need to stay within our experience. Though the only way to learn is by asking questions, so its a pleasure to answer those I can

Regards. broadfam@ntl.sympatico.ca