Extraction of Mineral Oil Compounds and Other Harmful Substances from Paper for Recycling using Supercritical CO_2

摘要

Paper for recycling is the most important raw material in the German paper industry. Also in the food industry, many products are sold in packaging products which are completely or at least partially made from recycled fibers. These products may contain harmful substances like pentachlorophenol, benzophenone, phthalates or mineral oils from printing or paper converting processes. Because of their toxicological properties and their potential to migrate from the packaging into the wrapped food they need to be removed from the recycling loop. With the use of super fluid extraction an innovative and efficient method for removing several harmful substances from paper for recycling was investigated. More than 99% of the nonpolar mineral oils can be extracted from newspapers already at 10 MPa (1450 psi) and 313.15 Kelvin (104 °F) while using a relatively small amount of CO_2. For the extraction of pentachlorophenol, a pressure of 40 MPa (5800 psi) and a temperature of 363.15 Kelvin (194 °F) are advantageous. The extraction efficiency of polar substances will further be improved by raising the moisture content. Depending on pressure, temperature, amount of CO_2 and dry matter content, except for bisphenol A, all measured harmful substances can be extracted almost complete.