Determination of the surface charge of lignocellulosic fiber by a derived spectroscopic technique

This paper proposed a derived spectroscopic technique for determining the surface charge of lignocellulosic fiber. In this method, chitosan quaternary ammonium iodide with higher molecule weight was selected to minimize its interaction with the negative charge inside of fiber pores. It was based on spectroscopically measuring the UV absorbance of I − (the counter ion) in the filtrates from a set of solutions that containing the fixed amount of fibers and the different amount of cationic polymer (from under- to over-saturation). By plotting the derived absorbance at 245 nm versus the volume of chitosan addition, a transition point is determined, from which the fiber surface charge can be calculated. The results showed that the present method has a good measurement precision (RSD < 3.24%) and accuracy (relative differences < 3.11%, when compared with the conductivity titration method). It is suitable to be used for determining the surface charge of lignocellulosic fibers.