Highly Efficient Removal of Diclofenac Sodium from Medical Wastewater by Mg/Al Layered Double Hydroxide-Poly(m-phenylenediamine) Composite

The emerging pollutant non-steroidal diclofenac sodium (DCF) has aroused increasing concerns, and the efficient removal of DCF from wastewater is becoming an urgent problem. In this study, the Mg/Al layered double hydroxide-Poly(m-Phenylenediamine) (LDH-PmPD) composite was synthesized, characterized and used for DCF adsorptive removal. The adsorption kinetics, isotherms as well as various influence factors, e.g., pH, humic acid, ions species and strength on the DCF removal were systematically investigated. The results showed that the presence of LDH weakened the accumulating density of PmPD and increased the specific surface area, which favored DCF adsorption on LDH-PmPD surface. LDH-PmPD exhibited a maximum adsorption capacity of 588 mg/g, which was superior to those of the conventional adsorbents. The artificial aging (100 d) experiment indicates a good stability of LDH-PmPD. Furthermore, due to the presence of electrostatic attraction, π-π electron-donor-acceptor interaction and N···HO hydrogen bonding between DCF and LDH-PmPD, the adsorption process was very effective in medical wastewater. The DCF removal efficiency reached nearly 100% within only 2 min in real medical wastewater using 0.125 g/L adsorbent. All these suggested that the prepared LDH-PmPD has great potential for DCF-contaminated water treatment.