Effects of mechanical activation parameters on the rheological behavior of acid-treated sepiolite

This study investigated the effects of mechanical activation parameters on the rheological behaviour of acid-treated sepiolite. Raw sepiolite samples obtained from the Türktaciri region of Sivrihisar were subjected to mechanical activation using a rotor-stator homogenizer with different rotor speeds (12000-24000 rpm) and activation times (30-1320 seconds) to disperse the fibre bundles. The samples were then treated with nitric acid at various molar ratios to remove dolomite impurities. Optimal acid treatment conditions showed that the sepiolite content could be increased from 84.4% to 91.9% using a nitric acid molar ratio sufficient to dissolve 80% of the dolomite present. Flow curve measurements revealed that increasing rotor peripheral speed (7.98–15.95 m/s) and activation time significantly affected the rheological properties. At 24000 rpm and 15.95 m/s peripheral speed, a significant increase in shear stress was observed in the shear rate range of 10°-10³ s⁻¹. The study demonstrated that mechanical activation parameters and acid treatment significantly affect the rheological behaviour of sepiolite suspensions, with the most stable network formation observed at higher peripheral speeds and longer activation times.