Evaluation of Deinking Chemicals Based on Ink Removal and Water Quality Using Lock Cycle Testin, 1997 Recycling Symposium Proceedings

The trend toward closure of internal water loops and the erratic availability of preferred raw furnish have newsprint recycling mills in North America rethinking the exclusive use of traditional non-ionic surfactants. The ‘wetting power of a synthetic surfactant coupled with its weak ink collective power leads to large ink removal at the wash or thickening stage. Unless the water is clarified, the system will build up a dead load of ink particles that impairs deinking performance and requires frequent purges. A set of bench top flotation tests was conducted to compare performance of non-ionic surfactants alone, fatty acids alone, and the combination of non-ionic surfactants with fatty acids to understand the effect of ink accumulation in the dilution water. The lock-cycle test method, commonly used in mineral processing, was used to model the closure of the water loop for five flotation tests in series. Each test consisted of pulping, floating, and washing of the furnish. The wash filtrate was used as the dilution water for the next flotation. The results show that a combination of fatty acids and non-ionic surfactants gives the best performance in a closed loop system.