Enhanced adsorption of diclofenac onto activated carbon derived from PET plastic by one-step pyrolysis with KOH

Plastic pollution is a severe threat to the health of ecosystems, and recycling plastics is recognized as a key control strategy. This study used the one-step pyrolysis assisted with KOH activation to recycle the widely used polyethylene terephthalate (PET) plastic as activated carbon (PET-AC) which was subsequently applied to adsorb diclofenac (DCF), a frequently detected emerging contaminant in water, for the first time. It was found that both the pyrolysis temperature and the addition of KOH can effectively regulate the pore sizes and volumes of PET-AC. PET-AC obtained at 700 °C demonstrated a high adsorption capacity of DCF up to 179.42 mg g^-1 at 45 °C. The adsorption kinetics was conducted with both static jar and dynamic column tests and analyzed with various models. Thermodynamic results demonstrated that the adsorption of DCF was spontaneous and endothermic. The material also presented an excellent potential to adsorb other pharmaceuticals and personal care products in water. XPS and FTIR analysis indicated that the adsorption might be mainly driven by the physical forces, especially π-π interaction and hydrogen bonding. This study provided a reference for recycling waste plastic as an efficient adsorbent to eliminate organic contaminants from water.