Abstract :
This study demonstrated an integrated waste minimization approach for the printed circuit board manufacturing shop of Lawrence Berkeley Laboratory (LBL). It included process waste assessment, process optimization and treatability analysis of the treatment system, and source reduction assessment. The results of a process waste assessment indicated that over 99.5% of the waste stream was rinsewater and less than 0.5% was characterized as hazardous waste. This finding led to a thorough source reduction assessment. From the process and treatability analysis, it was found that an organic chelating ligand in the wastewater was causing a copper precipitation problem. The results of a series of bench and process experiments indicated that optimization of pH, chemical dosage, and addition of ferrous sulfate were needed to destabilize the complexed copper. The destabilization mechanism of Cu-EDTA with ferrous sulfate at pH 6–9 was discussed. Different separation/recycling technologies were also evaluated through the source reduction assessment. A closed-loop process was simulated and designed. Through the source reduction and treatment process optimization efforts, at least 90% reduction of total acid wastes and wastewater and more than 99% metal removal were achieved. A material lifecycle analysis was also performed. The results indicated that a total quality control strategy is crucial to minimize wastes and reduce product rejection rate.
