Adsorption of Anionic Dyes by Polypyrrole-Grafted Mesoporous SBA-15 Composite: Isotherms, Kinetics, Thermodynamics, Interaction Mechanism and Recycling

SBA-15/polypyrrole composite was synthesized by polymerizing pyrrole in the presence of SBA-15. The samples were characterized using the following techniques: low-angle XRD, wide-angle XRD, FTIR, FESEM, TGA, HRTEM, and BET. From the low-angle XRD analysis, it confirms the formation of a mesoporous hexagonal structure (p6 mm). From the HRTEM image, an orderly arrangement of mesopores is evident. Using adsorption techniques, our objective is to remove sunset yellow, indigo carmine, titan yellow, and orange G dye from aqueous solutions with SBA-15/polypyrrole composite. The removal efficiency for all the dyes was greater than 90 %. The isotherm was verified to follow the Langmuir isotherm model. The maximum adsorption capacities for sunset yellow, indigo carmine, titan yellow, and Orange G were found to be 78.74 mg/g, 83.33 mg/g, 78.74 mg/g, and 106.38 mg/g, respectively. The adsorption kinetics followed a pseudo-second-order model, and the R2 value was greater than 0.99 for all the dyes. The thermodynamic parameters of Delta G degrees, Delta S degrees, and Delta H degrees showed negative values, indicating that the adsorption was spontaneous, decreased entropy, and was exothermic. The recycling of the SBA-15/polypyrrole composite resulted in a 90 % removal efficiency for three cycles. Therefore, the present adsorbent could be applied to treat industrial effluents that contain these dyes. A highly efficient and reusable composite of SBA-15/polypyrrole has been synthesized for the removal of anionic dyes, including sunset yellow, indigo carmine, titan yellow, and orange G from aqueous solutions. The study investigated the influence and mechanism of various factors, such as contact time, concentration, adsorbent dosage, pH, and temperature, on the adsorption process. The pH of the dye solution affects the electrostatic interactions by causing the protonation and deprotonation of functional groups on the adsorbent. The removal efficiency of all four dyes is 90 %. The SBA-15/polypyrrole composite can be recovered through a simple filtration process. Then, the treated water can be distilled to recover water for reuse. Therefore, this study may be applicable to the treatment of industrial effluents that contain dyes. Furthermore, this type of composite may be useful for the adsorption of commercial dyes in industrial effluents.image