Removal And Recovery Of Copper From Electroplating Rinse Water Via A Galvanic Cementation System
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Date
2003-02
Authors
YEAN PHIN, HOR
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Abstract
A galvanic system for the removal of copper from aqueous solutions using a
divided flow-through cell is proposed. The present study looks into the feasibility of
removing copper from dilute electroplating rinse water and recovering it in metallic
form by a galvanic cementation process. This process does not require an external
supply of energy due to the spontaneous chemical reaction between the copper/iron
couple. Therefore, this operation is attractive in reducing operating costs, especially
when dealing with low ion concentrations and serves as an alternative to current
wastewater treatments available. Two types of operating modes (single-pass and batchrecycle)
have been investigated. Initially, the performance of the proposed single-pass
system was evaluated as a function of cathode potential, catholyte flow rates, initial
copper (II) concentration and types of electrode materials used. Results have shown that
the galvanic flow system can remove copper effectively below the maximum
permissible level from simulated copper (II) solutions. However, an outlet copper
concentration below 1.0 mg L-I was not achieved with any condition when treating
industrial wastewater. Therefore, another mode of operation of electrochemical reactor
has been attempted to achieve higher efficiency of copper removal.
The second part of this work describes a batch-recycle galvanic reactor that
operates at flow rates ranging from 3.8 mL min-I to 500 mL min-I. A three-dimensional
cathode, 80 ppi reticulated vitreous carbon, was used for this purpose. Mass transfer
studies show that the average mass transfer coefficient was proportional to the Reynolds
number, RJ, where f = 0.68. A comparison of the performance between a single-pass
and a batch-recycle reactor was also conducted with an initial copper concentration of
10 mg L-I, 100 mg L-I and 500 mg L-I. A 500 mL feed of 74.2 mg L-I of copper in
electroplating rinse water with a low conductivity of 1.2 mS cm-I was reduced to less
than 1.0 mg L-I in 150 minutes with a batch-recycle reactor operating at a flow rate of
500 mL min-I.
Additional work on the treatment of other copper plating baths showed
satisfactory results especially with copper (II) fluoborate and copper (II) sulphate
solutions. The capacity of the batch-recycle galvanic reactor was also detennined.
Parametric studies of the copper deposition on reticulated vitreous carbon were made
using the optical microscope. A Scanning Electron Microscopy (SEM) investigation
was perfonned to study the microscopic features of the copper deposits and X-ray
energy dispersive spectrometry (ED AX) analysis was executed to confinn the presence
of copper recovered on the electrode.
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Keywords
Removal And Recovery Of Copper From Electroplating Rinse Water , Via A Galvanic Cementation System