Removal of tetracycline from aqueous solution using Fe-doped zeolite

International Journal of Industrial Chemistry https://doi.org/10.1007/s40090-019-0191-6 RESEARCH Removal of tetracycline from aqueous solution using Fe‑doped zeolite M. H. Jannat Abadi1 · S. M. M. Nouri2 · R. Zhiani3,4 · H. D. Heydarzadeh2 · A. Motavalizadehkakhky5 Received: 1 October 2018 / Accepted: 27 June 2019 © The Author(s) 2019 Abstract Tetracycline is one of the most widely used antibiotics that causes contamination of aqueous environments and has raised serious concern during the past few years. In this work, adsorption of tetracycline on a modified zeolite was studied through a batch system. Synthetic zeolite 13X was modified using Fe(III). The results show that the removal efficiency of tetracycline by modified zeolite has considerably increased. Different experiments were carried out in order to analyze the effect of parameters such as pH, initial concentration of tetracycline, time, etc. The results indicate that tetracycline adsorption on the zeolite strongly depends on the pH of the solution due to amphoteric functional groups of tetracycline and maximum adsorption capacity of tetracycline by modified zeolite with a pH of approximately 6. The Langmuir isotherm shows good agreement with the experimental data suggesting monolayer adsorption. Maximum adsorption capacity of the modified zeolite reached at the experiments is almost 200 mg/g. XRD, XRF and FTIR results confirm the existence of the Fe phase in the zeolite texture. Amide groups of TC were responsible for the complexation with Fe3+. Also, tetracycline removal was studied in a continuous column to simulate an industrial waste water process. Keywords Tetracycline removal · Adsorption · Modified zeolite · Fe-doped sorbent Introduction Tetracyclines (TC) are a broad spectrum class of antibiotics and are widely used for veterinary and human health purposes [1]. A large portion of antibiotics is transmitted from the body to excretion without modification. Excessive use of antibiotics, improper disposal, and lack of policy regulations pose a serious environmental and health concern [2]. Constant exposure to antibiotics in the environment not only disturbs natural ecological processes but can also be * S. M. M. Nouri 1 Chemical Engineering Department, Islamic Azad University, Neyshabur Branch, Neyshabur, Iran 2 Chemical Engineering Department, Hakim Sabzevari University, Sabzevar 9617976487, Iran 3 Young Researchers and Elite Club, Islamic Azad University, Neyshabur Branch, Neyshabur, Iran 4 Chemistry Department, New Materials Technology and Processing Research Center, Islamic Azad University, Neyshabur Branch, Neyshabur, Iran 5 Chemistry Department, Islamic Azad University, Neyshabur Branch, Neyshabur, Iran fatal to humans in the form of multi-antibiotic resistant bacteria. These bacteria are present in environmental sources (e.g., water, soil, and sediments) and can readily transfer their resistance to pathogenic bacteria via horizontal gene transfer, resulting in a global antibiotic resistance problem [3]. In the last two decades, progress has been made to address the antibiotic contamination problems in many environmental sources using various remediation technologies. Several physical and chemical degradation methods such as chemical oxidation, adsorption, membrane filtration, ozonation, photo-fenton, and bio-degradation methods such as activated sludge, membrane reactor, and fixed bed reactor treatment have been applied to many antibiotics including TC with the purpose of degrading them in environmental sources. However, these remediation technologies are highly condition-based (e.g., pH, and molar ratio) and potentially expensive based on the concentration of the contaminant present in the environmental source (antibiotic) that needs to be degraded [4–9]. Removal of antibiotics by adsorption is one of the inexpensive methods with small technical difficulties. Many adsorbents have been widely used to remove tetracycline from wastewater such as carbon nanotubes [10], graphene 13 Vol.:(0123456789) International Journal of Industrial Chemistry oxide [11], activated carbon [12, 13], zeolites [14–16] and metal oxides [17]. Synthetic zeolite 13X is a common adsorbent which is composed of silicon-oxygen and aluminumoxygen tetrahedron connected by oxygen atoms. The uniform pore structure and high surface area make it an ideal sorbent. The cation exchange capacity is relatively high, which enhances the effect of surface modification on the adsorbent capacity of the sorbent [18, 19]. Fe oxides are widely spread in ecosystems, and iron modified zeolites have been used for organic and heavy metal removal from wastewaters [20–23]. They show high affinity to TC compounds due to the surface complexation process [24, 25]. Iron ion could form a bridge between the zeolite and tetracycline molecule and enhance the adsorption process [26, 27]. The purpose of this work is to remove tetracycline using synthetic zeolite 13X. The synthetic zeolite has been modified with trivalent iron. The effect of different operating parameters such as pH, time, adsorbent dosage, etc. has been investigated. Materials and methods The zeolite used in this work is Na-13X which was purchased from IranZeolite. Tetracycline hydrochloride was purchased from Aldrich, F eCl3·6H2O and NaOH from Merck Inc. In order to prepare the treated zeolite, 3 g of zeolite was impregnated in 50 cc solution of 40 mmol F eCl3. The solution was stirred at room temperature for 24 h, separated and washed several times with deionized water and dried at 105 °C overnight. The obtained samples were powdered and used for the adsorption experiments. For the adsorption experiments, 50 ml of tetracycline solution with different concentrations and specified amounts of sorbent were mixed using a shaker for 24 h to make sure it reaches the equilibrium state. After separation by centrifuge, the supernatant solution was collected for concentration measurement using UV–Vis spectroscopy at 357 nm wavelength. The pH of the solutions was adjusted using 0.1 M NaOH and HCl. To investigate the effect of pH, experiments were carried out in the pH range of 2–9. For all the experiments, temperature was set to 30 °C. For the kinetic experiments, 75 mg of modified zeolite was added to 50 ml of tetracycline solution (200 ppm). Each 15 min, 1 ml of the solution was separated using a 0.22 μm membrane filter and the tetracycline concentration was measured. Table 1  XRF results for raw and modified zeolites 13 FESEM (TESCAN MIRA III), XRD (Philips PW 1730), XRF (Philips PW 1410), BET (BELSORP MINI II) and FTIR (Thermo AVATAR) analyses were performed for characterization of the sorbents. The XRD analysis was performed using the Philips PW 1730 instrument at an angle between 10 and 80 degrees. A glass tube with 20 mm diameter and 130 mm height was used for removal of tetracycline at continuous conditions. The tetracycline solution (200 ppm) was delivered using a perist (...truncated)