(628f) Reclamation of Copper From Polishing Wastewater by Electrodialysis

Since the development of copper interconnect technology for advanced microelectronics device manufacturing, the environmental impact of copper contamination and higher water consumption are serious challenges facing for the IC and Semiconductor industries nowadays. Traditional wastewater treatments processes typically require high chemical consumption and generate heavy metal sludge volume. With the rising environmental awareness and high raw material cost, the reclamation processes have come into public attention.

This research focuses on the efficiency of an integrated water reclaim system with Ultrafiltration (UF) and Electrodialysis (ED) for treatment and reclamation of copper wastewater. In this work, the permeate flux for the ultrafiltration membrane are investigated using artificial solutions containing nano-scale silica particles and Cu ions. Using different operating parameters we studied the separation efficiency, produced water quality and the optimal conditions applied to SiO₂ and Cu raw material recovery. Experiments are conducted using commercial polyvinylidenefluoride (PVDF) membrane, ion exchange membranes (SKS-CGSKS-A), and graphite electrodes in both batch and continuous operations with three parameters: concentration (SiO₂: 500, 1000 mgL^-1; Cu 10, 25, 50, 120 mgL^-1), pH (3, 4, 5) and voltage gradient (1, 1.5, 2.5 Vcm^-1). The UF membrane system could effectively separate the particles from the solution with a rejection rate over 99.7%, then the ED process would reclaim Cu ions from permeate solution. The removal efficiency of copper can reach above 95.6%, when the operating conditions in the well-stirred batch reaction process are constant voltage 50V and reaction time 2hr. Results from the desorption experiment presented the release amount of 93.5% of copper from ion-exchanger membrane.

The improvement of adsorption efficiency by the modified ED system is an emerging technique for recycling heavy metal from Chemical Mechanical Polishing (CMP) wastewater because it is capable to attenuate problems such as membrane fouling, block of ion exchange resin, and microbial activities in a batch reactor. The combination of membrane systems could treat the copper wastewater to the level that easily meets the Taiwan EPA’s effluent regulations (3 mgL^-1). With efficient desorbing solution, from this study presents the feasibility for removal and recovery of copper from wastewater.