Biosorption of Aspirin, Salicylic Acid, Ketoprofen, and Naproxen in Aqueous Solution by Walnut Shell Biochar: Characterization, Equilibrium, and Kinetic Studies.

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as salicylic acid (SAL), aspirin (ASP), ketoprofen (KET), and naproxen (NAP), are widely used to relieve pain, fever, and inflammation. For this reason, they are frequently detected in aquatic environments and have a negative impact on many aquatic organisms. In this study, walnut shell biochar (WSB) was used as an adsorbent for the removal of NSAIDs from water. The removal efficiency of pharmaceuticals was highly dependent on various parameters such as pH, contact time, sorbent dosage, and drug concentration. The studies conducted showed that WSB was able to remove as much as about 98% of pharmaceuticals. The maximum adsorption capacities of ASP, SAL, KET, and NAP were 20.92, 33.55, 39.84, and 172.41 mg/g, respectively. The equilibrium data for the investigated drugs showed a better fit to the Freundlich model than the Langmuir model. The pseudo-second-order kinetic model provided the best fit to the kinetic data. The results of the present study show that WSB could be applied as an eco-friendly and cost-effective biosorbent for the removal of drugs from the NSAID group from aqueous solutions.