Microwave Catalytic Degradation of Antibiotic Molecules by 2D Sheets of Spinel Nickel Ferrite Sandhya Mishra, Prashant Kumar,* and Sujoy Kumar Samanta* Cite This: Ind. Eng. Chem. Res. 2020, 59, 15839-15847 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: Pharmaceutical wastes such as antibiotics in the industrially polluted water are hazardous for the aquatic ecosystem and the environment and, hence, need to be adequately treated. Prompt and efficient degradation makes the microwave (MW) technique a cutting edge technology. Apart from promptness and efficiency, the ideal MW catalysts need to be thermally robust, recyclable, and economic. The coprecipitation synthesized highly crystalline spinel nickel ferrite (SNFO, E g ∼1.76 eV, M s ∼20 emu/g) and zinc ferrite (SZFO, E g ∼2.47 eV, M s ∼4 emu/g) atomic sheets are good MW absorbers and result in ∼90% and ∼86% MW degradation efficiency, respectively, for the tetracycline hydrochloride (TCH) antibiotic. The whole reaction is completed within 15 min, and it demonstrates the recyclability with the catalyst being unaltered. The ferrites are not only of low cost but also thermally robust and magnetically retrievable. The microwave degradation exhibits the pseudo-second-order kinetics. The quality of water after the degradation, especially the carbon content, has been quantified, and the degradation pathways have also been determined. 1. INTRODUCTION Tetracycline hydrochloride is an effective and safe generic antibiotic recommended by World Health Organization (WHO) to fight the bacterial infections including plague, acne, brucellosis, cholera, malaria, and syphilis. 1−5 The harmful pharmaceutical antibiotic residues are primarily dumped into the water bodies causing serious damage to the ecosystem which has become one of the major global concerns. Therefore, the wastewater containing these antibiotics needs to be adequately treated. 6−16 The conventional wastewater treatments such as the electrochemical method, reverse osmosis (RO), ultrasonication, and advanced oxidation processes (AOPs) exhibit lower efficiencies. Hence, these are time-consuming processes. 17−22 In order to improve the ecosystem including human health conditions, the surrounding environment needs to be purified, and to accomplish this objective, it is very important to develop novel technological solutions to degrade the pharmaceutically polluted wastewater at a fast pace and in a scalable manner. Hence, the microwave treatment is proposed as one of the viable solutions for the antibiotic polluted water. A few important advantages of the microwave-based energy are (a) an excellent source of electrical energy with high power ratings, (b) ease of working with it, (c) ease of generating it economically, (d) energy delivery in a tunable manner, and (e) portability of the whole unit, etc. When a microwave oven containing microwave absorbing solid or fluid material is ON, the central region of the waveguide attains an extreme local temperature, and that can be smartly employed for the environmental remediation. As the literature on the microwave degradation of the antibiotic polluted water is very scarce, there is an urgent need to conduct a thorough study along this direction. 22−27 In order to achieve the aforementioned advantages of the microwave catalysis, an ideal catalyst is extensively being hunted that could satisfy the following criteria: (a) has minimal reaction steps for its synthesis, (b) is economical, (c) interacts with the target molecule, (d) has high microwave absorption, and (e) is unaltered under the extreme microwave operating conditions. The ferrites exhibit excellent structural crystallinity, high thermal stability (high melting points), and good microwave absorption. In particular, spinel zinc ferrite has already been employed for the microwave degradation purposes. 28 Moreover, the ferrites being excellent MW absorbing materials would accelerate the process and, there- fore, can be used as a catalyst in the MW degradation. 28−32 Therefore, the potential of the coprecipitation synthesized spinel nickel ferrite (SNFO) atomic sheets as a microwave catalyst was explored, and its performance was compared with that of spinel zinc ferrite (SZFO). While the morphological investigation was carried out in atomic force (AFM) as well as Received: May 9, 2020 Revised: August 12, 2020 Accepted: August 13, 2020 Published: August 28, 2020 Article pubs.acs.org/IECR © 2020 American Chemical Society 15839 https://dx.doi.org/10.1021/acs.iecr.0c02352 Ind. Eng. Chem. Res. 2020, 59, 15839−15847 Downloaded via INDIAN INST OF TECH PATNA on December 30, 2020 at 10:32:53 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.