Adsorbents derived from hydrotalcites for the removal of diclofenac in wastewater

Emerging compounds have received increasing attention because of their potential environmental hazards. The drug diclofenac has acute toxicity and has been detected in surface water and wastewater. Conventional treatment processes are not able to totally remove this compound. Adsorption has been widely used to remove pollutants and standing out as an unspecific and versatile operation. In this context, the present study investigated the application of mixed oxides of Mg, Ni, or Zn with Al, derived from hydrotalcite-type compounds, as adsorbents in the removal of sodium diclofenac from synthetic aqueous solutions. The solids were synthesized by the continuous coprecipitation method and characterized by the S-BET, XRD, TGA, FTIR, and SEM techniques. The influence of adsorbent dosage and contact time parameters were evaluated. Adsorbent regeneration by thermal treatment was also evaluated. The results showed that sodium diclofenac highest removal rates were found applying the best experimental conditions: residence time and adsorbent dosage of 30 min and 2 g L-1 for C-Zn with maximum adsorption removal of 76.5%. The thermal treatment after the adsorption confirmed the regeneration of the solids, allowing reuse in the adsorption for up to 8 cycles. The application of mixed oxides as sorbent solids was technically feasible for the removal of diclofenac sodium in wastewater treatment.