Adsorption process of naproxen onto peanut shell‐derived biosorbent: important role of <i>n</i>–<i>π</i> interaction and van der Waals force

Abstract

Abstract BACKGROUND Low‐cost biosorbent (derived from peanut shells) with abundant oxygen‐containing functional groups can effectively adsorb the naproxen drug in solution. This study aimed to explore the main interactions responsible for adsorbing naproxen and develop several conventional methods for identifying primary adsorption mechanism. Some important operation parameters strongly effecting the adsorption process and mechanism were investigated and discussed. RESULTS A fast adsorption equilibrium can be reached at approximately 120 min. The Langmuir maximum adsorption capacity of biosorbent towards naproxen ( Q o max ; mg g −1 ) was 55.1 mg g −1 . The study of adsorption thermodynamics indicated that the adsorption process was spontaneous (∆ G ° ≈ −21 kJ mol −1 ) and exothermic (∆ H ° = −14.9 kJ mol −1 ), and van der Waals force played an important role in the adsorption mechanism. Another important contribution of n – π interaction between the carbonyl groups on the biosorbent's surface and the aromatic rings in naproxen molecules was confirmed by Fourier‐transform infrared spectroscopy and a traditional method. Such n – π interaction cannot be well performed when carbonyl groups were oxidized into carboxylic groups under H 2 O 2 treatment. Peanut shells exhibited an excellent adsorption capacity to various pollutants such as lead ( Q o max = 167 mg g −1 ), cadmium (103 mg g −1 ), cobalt (88.8 mg g −1 ), diclofenac (56.1 mg g −1 ), and bisphenol A (24.5 mg g −1 ). CONCLUSIONS Simple methods were developed to identify the important role of van der Waals force and n – π interaction in the adsorption process of naproxen. Such methods might be applied to identify the similar adsorption mechanisms of other aromatic adsorbates onto other materials with similar properties. Peanut shells can serve as a promising biosorbent for eliminating naproxen and other pollutants from water environment. © 2020 Society of Chemical Industry

Topics & Concepts