Investigation on the Effect of Metal Ions of Medium Elements on the Whiteness Property of Chemimechanical Papers Produced in the Wood and Paper Factories of Mazandaran

This research was conducted to study and determine the negative effect of metal ions on whiteness of the chemimechanical pulp samples which are produced in Mazandaran Wood and Paper Mill. The chemimechanical pulp samples were prepared from the mill in unbleached from. EDTA chelating agent was used with concentrations of 0، 0. 25، 0. 5، 0. 75 and 1% in order to neutralize the metal ions which cause further aging and yellowing of the CMP samples. Then، each sample was wetted with solutions containing metal elements of Fe2+، Fe3+، Cu2+، Al3+ and Mn2+ after drying. The obtained results revealed that the maximum effect in whiteness reduction belongs to the Fe2+ ion while the minimum effect is related to Al3+ ion. Moreover، it can be inferred from the results that wetting of the samples at different concentrations of the chelating agent (EDTA) has an optimal value in improvement of the whiteness characteristics of the paper. More than this optimal value، further increasing the EDTA concentration does not improve whiteness and brightness durability of the samples. Whiteness of the CMP degrades significantly by increasing the aging time.