Deinking of laser printing with ultrasound of intensive action to obtain high purity cellulose

Abstract

A study on the deinking of office waste paper printed with laser is presented, applying ultrasound of intensive action, combined with stages of flotation and washing. The treated material was evaluated to determine its use as a basis for generating soluble grade cellulose. The waste paper was manually torn and disintegrated at 1.2 % consistency, for 10 min. The disintegrated fiber was treated with intensive-action ultrasound. At this stage, a 2^k multifactorial experimental design was applied, in which the parameters time (min), consistency (%), temperature (°C) and time of pause of application by ultrasound were used; while the number of ink particles m^-² of paper, was the response variable. Low consistency and commercial surfactant were used in the flotation and washing steps. The deinked pulp was evaluated by analyzing various quality parameters such as a-cellulose content, brightness, CIE color L *, a *, b * and the residual particle count m^-², using TAPPI standards. The obtained results indicate that the proposed deinking showed great efficiency in generating fragments of toner, of size between 25-50 and 50-100 mm. These particles were removed in flotation and washing. The best removal of ink m^-² of paper was obtained with 20 minutes of treatment, 0.5 % consistency, 25 °C and continuous ultrasound application. Finally, the properties of the pulp obtained under optimized conditions indicate that it can be reused in paper grade products and even to generate soluble grade cellulose by applying some subsequent bleaching.