The Effect of Pulp Suspension pH on the Performance of Chitosan - Nanobentoniteas a Dry Strength Additive in Hardwood CMP Pulp

In this research، the effect of pH onthe performance of nanobentonite -chitosan system (as dry strength additives) in hardwood chemi-mechanicalpulp (CMP) was studied. For this purpose، 3 levels of pH (5. 5، 7، 8. 5) and 3 levels of chitosan (0. 75، 1. 25 and 2% - based on oven dried pulp) in constant level of 0. 3 nanobentonite (based on oven dried pulp) were applied. The Atomic Force Microscopy (AFM) imageconfirmed the nano structure of bentonite in thickness dimension at the range of 1-22. 3 nm. The results indicated that nano bentonite – chitosan in all levels of pH caused numerical improvement in tensile،burst and tear indicesand also apparent density in comparison with control sample. Although theeffect of studiedvariables (chitosan dosages and pH levels) on considered properties was statistically significant،but most of treatments were in the same groups according to Duncan grouping. In this research، treatment consisting of 1. 25 chitosan in fixed level of 0. 3 nano bentonite at alkaline pH showed the best results in mentioned properties and statistically had significant difference comparing other treatments. Therefore،it wasintroduced as theselected treatment in this research. It seems that the ratioof chitosanandbentonite nano anion had a great effect on performance ofnanoparticle system. Also the results showed that the performance of system depend on the pH of furnish and the best results was achievedin alkaline condition (pH=8. 5).