Evaluation and Optimization of Old Magzines Deinking Process of a Modified Lignin Sulfonates Deinking Agent

Deinking is an important process in waste paper recycling process, and this study mainly focuses on the properties of the deinking agent and process optimization. DIA-30 prepared in our laboratory, and FS and LD, were the three representative deinking agents studied herein. Brightness, effective residual ink concentration (ERIC), dirt, macro-stickies, fiber loss during repulping, flotation, and washing processes were measured to evaluate the performance of the deinking agents and optimize process conditions. Each of the deinking agents exhibited different advantages: DIA-30 was optimal for deinking efficiency, brightness enhancement, as well as dirt and macro-stickies removal, whereas LD was optimal for ink removal during flotation process but performed poorly in terms of brightness enhancement. FS showed a relatively balanced performance compared to those of DIA-30 and LD in the deinking process, but DIA-30 is the best option for deinking due to its outstanding comprehensive properties. The optimal repulping conditions for the deinking of 100% old magzines (OMG) using DIA-30 are as follows: repulping temperature, 60℃; pulp consistency, 13 wt%; repulping time, 20 min; H₂O₂ dosage, 0.5 wt% (oven-dried pulp); NaOH dosage, 1.2 wt% (oven-dried pulp); Na₂SiO₃ dosage, 0.3 wt% (oven-dried pulp); and optimum DIA-30 dosage, 0.1 wt%.