Canadian Finishing and Coatings Manufacturing: Nov/Dec 2022 - 35

PLATING AND ANODIZING: FILTER SYSTEMS
Carbon Treatment Methods
C
EFFICIENC Y , MAINTENANCE AND DISPOSAL
arbon treatment options for purifying and balancing
electroplating processes have expanded considerably.
Refinements on activated carbon grades boost
efficiencies and filtration method options. Applying
appropriate grades and filter apparatus will ensure optimal
results for maximizing productions yields and the bottom line.
Producing
finished
electroplated
components
requires
a myriad of costly steps including purifying process water,
chemistry make-up, lab diagnostics and fabricated parts to
be plated. POP plating (Plating-On-Plastic) is comparable to
PCB (Printed Circuit Board) Acid Cu plating, where rejected
components are a total loss. Alternatively, metallic plated parts
can be stripped for incremental recovery. Disruption on the
finished plate from insidious particles can impede appearance,
corrosion resistance (e.g. vehicle bumpers) and functionality
(e.g. flowing electrons in printed circuit boards).
Carbon Specifications
Carbon Grades
* Extruded
* Granular Activated Carbon (GAC)
* Powder Activated Carbon (PAC)
Raw Materials
* Any Carbonaceous Material- typically coal, coconut and
wood based
* Raw Material Selection Dictates Performance and Product
Possibilities - Ash impurities, density, hardness, transport
pore structure and adsorption kinetics
*
Single unique family of products from a raw material source
Application
* Coal based carbon is highly effective in managing organic
break-down compounds in chemical processes.
* Coconut shell (sulfur free) carbon is used for water
treatment, chlorine removal, R.O. pre-filtration to protect
membranes, and effluent processes.
Manufacturing Processes
* Many Combinations and Permutations Possible
* Most utilize a thermal process
Other Factors
* Dust extraction of finished raw carbon
*
Carbon Specifications
Data
Iodine/butane no.
Hardness/abrasion no.
Screen or mesh size
Moisture
Apparent density
Ash
Increased hardness to resist powder formation during
shipments
Description
Indicator of total surface area or pore volume
Mechanical strength or attrition resistance
Size distribution of media
Water content
Mass carbon per unit volume (g/cc)
Inorganic matter/non-adsorptive
Factors that Effect Adsorption
Liquid Phase:
* Solubility: The higher the solubility, the more difficult to
adsorb
* Concentration: Wt. percentage loading on carbon increases
as inlet species concentration increases
* Molecular Weight: The higher the MW, the better adsorbed
* Structural Complexity: More complex structures adsorb
more readily
Disc Pack - Activated Powder Carbon
Higher volume process tanks often use horizontal disc filters
equipped with slurry mixing tanks to form a " disc pack " of
diatomaceous earth (D.E.), as the pre-coat layer, followed by
activated powder carbon (APC). Powder carbon may provide
more surface area than granular but powder will instantly blind
filter media. Accordingly, a 2:1 ratio of D.E. to carbon for necessary
depth diminishes carbon volume by two thirds.
Disc filter assemblies must have positive sealing applied to
disc media for withstanding the force of pressure generated by
the pump, while the media must resist corrosive process streams.
Sealing of disc assemblies can be compromised with elevated
November/December 2022
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Canadian Finishing and Coatings Manufacturing: Nov/Dec 2022

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