Evaluation of different powdered activated carbons in the control of chlorite ion

Twelve different powdered activated carbons (PACs) were screened under laboratory conditions to determine their performance in the removal of chlorite ions (ClO₂⁻) and in the production of chloride ions (Cl⁻) and chlorate ions (ClO₃⁻) during that removal. All screenings were conducted in reagent water, at pH 7.0 ± 0.2 pH units, with a standard concentration of 20 mg/liter of powdered activated carbon (PAC) added in each case, and with the process and samples protected from light. One set of screening experiments was conducted with both ClO₂⁻ and chlorine added with the PAC, while the other set contained only ClO₂⁻, and PAC. The chlorine and ClO₂⁻ were added to concentration levels which might be expected in disinfection practice in water treatment plants. Periodic samples were drawn as the mixtures were stirred over a 24 hour period. Each sample was analyzed for Cl⁻, ClO₂⁻, and ClO₃⁻ concentrations utilizing ion chromatography. All PACs were found to reduce ClO₂⁻ to Cl, and ClO₃⁻ was never detected when chlorine was absent. The data provided no consistent significant evidence of ClO₃⁻ formation even when chlorine was present. The rate of ClO₂⁻ removal was most rapid in the first two hours of contact, but slowed to rates below 6 percent per hour after 4 hours of contact. Rates of ClO₂⁻ removal varied with PAC type. The overall rate of ClO₂⁻ removal was also slower, with the total percentage of ClO₂⁻ removal less, when chlorine was present in the mixture.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Environmental Planning

Department dc:contributor.department

Environmental Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1993

Author dc:creator

• Mitchell, Robert M.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-07112009-040246

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43659