This study is carried out to investigate the possibility of using Iraqi clay; Duekhla kaolin as filler in the paper industry by reducing the percentage of iron oxide, titanium dioxide, and free silica. Duekhla Kaolin containe about 1.7% iron oxide, 1.2% titanium dioxide, 51.16% silicon dioxide, and 12% free silica. The existence of these oxides in kaolin is undesired in paper-making. The process started by washing Duekhla kaolin with (4N) HCl to remove all the soluble oxides which are not required in paper making. The washed kaolin then separated using filter papers and under a sequence of operations of dilution and filtering until the pH - value become 5. The separated materials then dried at temperature range 40-60 °C for 3 hours, and the dried powders then milled using ball mill of porcelain body, with different sizes of spheres, for 5 hours. Finally the powders of Duekhla Kaolin sieved with a sieve of 65 μm.The sedimentation method is used for the separation of the above mentioned oxides from clay by using sodium phosphate as dispersant agent. The viscosity parameter of the mixture was studied under the effect of the dispersant agent, and it was found that with the increasing of added dispersant agent the viscosity decreased to a minimum value which is equal to 0.31dyne.cm2/sec, after that the viscosity increased with the increasing of adding sodium phosphate. The study performed; depending on the minimum viscosity value corresponds to the dispersant amount added. The zinc hydrosulfite was used as a bleaching agent in a second step for removing the undesired impurities which implies to raise the brightness degree of kaolin Duekhla as a result. As a result of these treatment, the undesired oxides are reduced from sample G7 by the following percentages; (73% of iron oxide, 91% of titanium dioxide, 15% of silicon dioxide, and 50% of free silica removed), the results of this study reveals that the oxides percentages decreased from (1.71% to 0.3% in iron oxide, 1.2% to 0.09% in titanium dioxide, and 51.16% to 39.7% in silicon dioxide). The crystal structure of kaolin did not change after these treatments to decrease the percents of impurities in this clay to be used as filler in the paper industry.
