Effect of using activated sludge, cationic starch and nano-chitosan on physical and strength properties of old newspaper recycled pulp

This study aimed to study the effect of using paper making activated sludge, cationic starch and nano-chitosan on physical and strength properties of old newspaper recycled pulp (ONP). For this purpose, the activated sludge was pre-treated for 30 min in 3% furfural and then treated with it in a water bath at 75 and 100 ° C for 45 and 90 min. Afterwards, it was mixed and refined with waste newsprint paper pulp at different mixing ratios. Finally, cationic starch 1.5% and nano-chitosan 2% were added. The test specimens were prepared from pulps with 120 gr/m2 basis weight according to TAPPI standard and the physical and strengths properties were measured and compared. The results showed that the strengths properties (tear, ring crush test, burst, folding strength) decreased and the physical properties (water absorption) increased with the increase of untreated sludge in ONP. Chemical treatment with furfural sludge showed a tangible increase in tear strength, ring crush test, burst strength and folding strength and a decrease in tensile strength and water absorption. Also, the addition of cationic starch and nano-chitosan significantly increased the strengths properties and decreased water absorption of the samples. FT-IR spectrum of the treated samples showed that treatment with furfural strengthen and activate the functional groups on the surface of sludge fibers.The most appropriate mixing ratio of sludge was at 5% level at 100° C, and 90 min.