Ultrasonic-Thermal Regeneration of Spent Powdered Activated Carbon

This study investigated the ultrasonic-thermal regeneration of powdered activated carbon (PAC) spent using 4-chlorophenol (4-CP). Similarly, a thermal regeneration process was also studied and the reaction conditions (i.e., regeneration temperature, heating rate, regeneration time) were tested. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis were applied to characterize the regenerated PACs under different treatments (thermal, ultrasonic and ultrasonic-thermal) and also compare them with the fresh and exhausted PACs. According to our regeneration observations, the ideal regeneration parameters were determined to be a 40 kHz frequency, 0.18 W/mL sonication power, 0.1 M NaOH and 50% (v/v) ethyl alcohol as the regeneration solution, and 1 g/L of saturated PAC mass with thermal regeneration as the second stage at 500 ?, desorbed for 30 min with a heating rate of 20 ? min(-1). Under these conditions, the RE value achieved 90.99% and the ? value reached 5.6%. The results of FTIR, XPS and XRD revealed that the oxygen functional group content of ultrasonic-thermal regenerated PAC significantly increased. These oxygenous groups exerted a positive effect on the adsorption process of the regenerated PAC and the subsequent adsorption-regeneration process.