Development and Optimization of Chemical Deinking of Laser-Printed Paper

Abstract

For the recycling paper process, the main problem is a high residual ink left on the paper, affecting the recycled paper's quality. Especially for laser-printed paper, ink strongly interacts with the paper fiber. A conventional chemical deinking has been used to remove laser ink with a high deinking efficiency but a low yield of recycled paper pulp. Recently, enzymatic deinking has gained attention due to its friendly environment. However, a complex procedure is required, and ink removal efficiency is lower than the conventional method. This research aims to simplify a chemical deinking process by decreasing reaction time, optimizing chemical components, and reducing experimental steps. Without pulping step, the laser-printed paper sheet was immersed in the chemical solution for a specific time, and the ink was removed by water spray. Results revealed that the chemical solution containing 1.5% sodium hydroxide, 2% sodium silicate, 1% hydrogen peroxide, and 0.3% tween-80 with a reaction time of 5 min at 60°C gave the highest paper yield of 97.3% and the lowest dirt count of 89.0 mm2/m2. The final product was still in the form of a paper sheet.