Corporate Office:4461 Cox Road

Glen Allen, VA 23060

Bruce BowenChemTreat, Inc.Sales Manager

Plainwell, MI

Chemical Precipitation

of Metal Hydroxides

INDUSTRIES IMPACTED:

• Metal Finishing

• Foundry and Casting

• Mining

• Microchip/semiconductor Production

• Automotive

• Printing

HEAVY METALS IN QUESTION:

-Zinc -Nickel

-Chromium -Copper

-Tin -Mercury

-Iron -Cobalt

-Silver -Aluminum

-Cadmium -Arsenic

Precipitation of Heavy Metals as Hydroxides

Precipitating Agents

• Calcium Hydroxide - Ca(OH)2

• Magnesium Hydroxide - Mg(OH)2

• Sodium Hydroxide - Na(OH)

• Soda Ash – Na2CO3

Zn2+ (aq) + CO32- (aq) = Zn(CO3) (ppt)

Zn2+ (aq) + 2OH- (aq) = Zn(OH)2 (ppt)

Precipitation Reaction

Typical Concentrations Obtainable Through Conventional Chemical Precipitation

Achievable

Concentration Precipitating

Heavy Metal (mg/liter) Agent

Cadmium 0.3 Soda Ash

Trivalent Chromium 0.5 Caustic, Lime

Copper 0.5 Caustic, Lime

Iron 1.0 Caustic, Lime

Nickel 0.5 Soda Ash

Zinc 0.5 Caustic, Lime

Typical Treatment Plant

Post Treatment Polishing

Anti-Chelation Chemicals:

• Dithiocarbamate

• Sulfide (Na2S)

Post Treatment Polishing