Copper Wastewater Reclaim System for a Printed Circuit Board Facility

Background

In the PCB industry, there are several steps that may produce copper waste: copper precipitation, pattern plating of copper, etching and other pretreatment processes (chemical treatment, the brush plate before processing volcano ash grinding plate processing, etc). Wastewater from the above steps can be divided into two categories: chelate type and non-chelate type. Below is a simple description of these two kinds of wastewater:

A. Chelated copper wastewater comes from the following processes:

1. Electro-less copper precipitation which uses EDTA and sodium tartrate.

2. Alkaline etching and micro etching which use ammonia and ammonium.

3. Other steps such as acid degreasing and alkaline degreasing.

It is very difficult for copper to be precipitated due to complexants’ existence. It can be oxidized before precipitation or, a stronger precipitant can be used such as sulfide or a special heavy metal chelating agent. Sometimes resin adsorption or Ca displacement are other options.

B. Non-chelated copper wastewater comes from pattern plating copper, acid etching and rinse water from other steps. Normally precipitation, especially an alkali precipitation method, is effective on non-chelate copper wastewater treatment.

Wastewater Information

The wastewater in this facility comes from the rinse stream of the pattern plating copper process. Total system capacity is designed as 150m3/hr.

Traditionally this kind of wastewater has been treated by a simple alkali precipitation (with caustic soda, ferric chloride and polymer dosing) followed with a clarifier. However, the treated water quality is not good enough for water reuse. That is why the manufacturer decided to select the Porex TMF system as an alternative to a traditional clarifier (or sedimentation tank).