Sulfur dioxide Plasma Treatment of the Clay (Laponite) Particles

Low temperature plasma treatment of the inorganic clay (Laponite) using sulfur dioxide (SO₂) as a process gas was carried out in order to graft the functional groups containing sulfur and oxygen (sulfonic acid groups) onto the inert clay surface. Conditions for SO₂ plasma modification were optimized by the measurement of the sulfur content as a function of the plasma power, gas flow rate and treatment time. It was found that the sulfur content increased with the increasing of the plasma power as well as the treatment time. Optical emission spectroscopy was presented in order to control the plasma phase and to characterize the different excitation processes of atomic species in SO₂ plasma under different discharge conditions. X-ray diffraction spectrometry, X-ray photoelectron spectroscopy, FTIR and thermal analysis measurements of grafted Laponite powder completed the characterization.