Effect of using cellulose nanofibers and cellulosic papermaking fines simultaneously on the properties of de-inked recycled pulp

The aim of this study was to enhance the physical and mechanical properties of deinked recycled paper by using the cellulose nanofibers (CNFs) and obtained fine fibers from pulp refining. The process was conducted in the presence of a cationic additive including cationic starch (group A), poly aluminum chloride (group B), or cationic polyacrylamide (group C). The Design Expert software was used to prepare the experimental design and analyzed the results. The results showed that by using fine fraction up to 16 wt% and cellulose nanofibers up to 7 wt%) with cationic starch (group A) the tensile strength was increased almost 44%, burst strength 53%, and water retention value of pulp (WRV) 35%. These values for treated pulp with group B were 41%, 48%, and 22% while, , for treated pulp with group C were 40%, 42% and 27%, respectively. However, those treatments increased the dewatering time from pulp and the highest increase in dewatering time was 47% when 16 wt% fine and 7 wt% cellulose nanofibers were used along with cationic starch. In addition, increasing of dewatering time for treated pulp with group B and group C were 41% and 30%, respectively. The evaluation and comparison between different treatments indicated that the treatment of deinked recycled pulp with group C would be a suitable treatment, due to minimum adverse effect on pulp drainage time and considerable improvement of dry strengths.