Purification of copper wire drawing emulsion by application of UF and RO

Abstract

The application of ultrafiltration (UF) and reverse osmosis (RO) membrane technology for the treatment of spent copper wire drawing emulsion to reduce fresh water consumption and environmental pollution has been investigated. The UF pretreatment process was tested on the effluents from copper wire drawing plant that enables further RO purification to process water standards. The tubular membranes used in UF pilot plant were made from polyvinylidene fluoride (PVDF), poly(vinyl chloride) (PVC) and polyacrylonitrile (PAN) with MWCO of 100 kDa, 70 kDa and 50 kDa, respectively. These membranes exhibit 100% rejection of suspended solids and produce the effluents with the content of oil and lubricant of less than 10 ppm. The UF pretreatment generates permeates with Silt Density Index (SDI) of <3 that renders them suitable for RO feed. However, the retention of copper ions and TOC by UF membranes was generally below 10%. The effluent from UF pilot plant was further purified by reverse osmosis using the spiral-wound membranes (BW3040 element, Filmtec). The retention of oil and lubricant in the RO process was 100% and the content of the copper ions in the permeate was generally less than 10 ppm (retention above 99.5%). A combined UF/RO pilot plant system used for the purification of spent copper wire drawing emulsion results in treated water with the conductivity of 40 μS/cm suitable for direct non-potable reuse for emulsion top up.