Characterization of Iron-Modified Natural Clay for Textile Dye Retention by Sono-Adsorption Technology

In the present study, iron-pillared clay was prepared using ferrous nitrate Fe(NO3)3. The removal of Reactive Blue (RB4) dye by ultrasound-assisted sorption onto the synthesized pillared Tunisian clay in aqueous solutions was studied. The natural and modified clay samples were characterized using XRD, FTIR TEM, and nitrogen adsorption measurement methods. Mineralogical data show that smectites are the main minerals of clay samples. FTIR spectra indicate that the stretching vibration bands of the structural hydroxyl groups are broad after treatments. A new band appears at 1570 cm−1, after the sorption of RB4 dye, attributed to aromatic C = C stretching vibration, which suggests the adsorption of RB4. A remarkable decrease was detected in the BET surface after sono-adsorption indicating that the sites of modified clay are almost occupied by the dye. The maximum Reactive Blue 4 quantity was removed at pH 8. Meanwhile, more active Fe–C surface sites were available for both adsorption and sono-adsorption with increasing RB4 concentration, thereby increasing the removal efficiency. Monolayer adsorption capacity via the sono-assisted method also showed a high removal amount of 46.51 mg/g. Langmuir’s model describes the experimental data better than Freundlich’s. A comparative study confirmed that RB4 sono-adsorption by a Tunisian clay sample was higher than others used in other relevant studies, highlighting that these clay deposits may be applied to the dyes’ elimination from wastewaters.