Effect of ultrasound-assisted method to enhance rice husk ash adsorption characteristics for paracetamol removal

The objective of this work was to evaluate the effect of modifying the rice husk ash particle surface using the ultrasonic technique. For this, a comparative analysis was performed on the paracetamol adsorption capacity using rice husk ash particles as adsorbents modified and non-modified by ultrasound-assisted method. Sorbent modification was carried out by exposing the rice husk ash to the ultrasound technique for a specified time (5, 15, 30 and 60 min). Also, it was characterized by surface area, pore diameter and volume, X-ray diffraction (XRD) and Fourier transform in infrared (FTIR). The adsorption parameters evaluated in batch-scale experiments were the contact time (0 to 60 min) and adsorbent concentration in solution (0 to 25 g.L^-1). The results obtained showed that the ultrasound modification made the particle less reactive, requiring a higher concentration of adsorbent (when compared to the unmodified solid) to obtain the same amount of model pollutant removal. The maximum paracetamol removal obtained in the tests with the original rice husk ash was 90 % after 30 min of contact and solid concentration of 13 g.L^-1. In the same contact time, for the rice husk ash modified in ultrasound, 20 g.L^-1 were needed, reaching 100 % removal of the pharmaceutical. This result demonstrates the functionalization of the technique and a good performance and application of the solid as an adsorbent for the removal of pharmaceutical compounds.