Opportunities and challenges of using ultrafiltration for the concentration of diluted coating materials

The use of cross-flow ultrafiltration for the recovery of coating material from aqueous streams started about 30 years with electro deposition paint in the automotive industry. This early success can be related to both environmental and economical ad-vantages of using ultrafiltration. Ultrafiltration recovers and concentrate electro deposition paint on the retentate side and produces purified water on the permeate side. Based on this success, more recently, the focus moved to other coating materials, such as paper coatings, latex and flexographic ink. Similar to electro deposition paint, the concept is to recover the diluted coat-ing materials with ultrafiltration to obtain solid free permeate stream, which can be either recycled or easily treated, and a re-tentate stream, which contains the coating materials preferably at concentrations suitable for recycling or disposal. The advantages can be directly translated into very short pay-back times for ultrafiltration systems of typically less than two years. Applica-tion studies focusing on the coating recovery in a paper mill, the concentration of latex from the tank wash at a latex producer and the recovery of flexographic ink at a producer of printed cartons will highlight these benefits.