water Article Adsorption-Membrane Hybrid Approach for the Removal of Azithromycin from Water: An Attempt to Minimize Drug Resistance Problem Muhammad Wahab 1 , Muhammad Zahoor 2, * , Syed Muhammad Salman 1 , Abdul Waheed Kamran 3 , Sumaira Naz 2 , Juris Burlakovs 4 , Anna Kallistova 5 , Nikolai Pimenov 5 and Ivar Zekker 6, *   Citation: Wahab, M.; Zahoor, M.; Muhammad Salman, S.; Kamran, A.W.; Naz, S.; Burlakovs, J.; Kallistova, A.; Pimenov, N.; Zekker, I. Adsorption-Membrane Hybrid Approach for the Removal of Azithromycin from Water: An Attempt to Minimize Drug Resistance Problem. Water 2021, 13, 1969. https://doi.org/10.3390/w13141969 Academic Editor: Margaritis Kostoglou Received: 1 June 2021 Accepted: 15 July 2021 Published: 18 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Chemistry, Islamia College University, Peshawar 25120, Pakistan; mwahabbajaur@gmail.com (M.W.); salman@icp.edu.pk (S.M.S.) 2 Department of Biochemistry, University of Malakand, Chakdara 18800, Pakistan; sumaira.biochem@gmail.com 3 Department of Chemistry, University of Malakand, Chakdara 18800, Pakistan; waheedkamran1989@gmail.com 4 Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, 5 Kreutzwaldi St., 51014 Tartu, Estonia; Juris.burlakovs@emu.ee 5 Winogradsky Institute of Microbiology, Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospect, 33, Build. 2, 119071 Moscow, Russia; kallistoanna@mail.ru (A.K.); npimenov@mail.ru (N.P.) 6 Institute of Chemistry, Faculty of Science, University of Tartu, 14 Ravila st, 50411 Tartu, Estonia * Correspondence: mohammadzahoorus@yahoo.com (M.Z.); ivar.zekker@ut.ee (I.Z.) Abstract: In this study, activated carbon (AC) and magnetic activated carbon (MAC) were prepared from Dalbergia sissoo sawdust for the removal of antibiotic Azithromycin (AZM) from aqueous solution. The effect of initial concentration, contact time, pH, adsorbent dosage, and the temperature were investigated for both the adsorbents. The optimum AZM concentration, contact time, pH and adsorbents dosages were found to be 80 mg/L, 120 min, 6 and 7 (pH, respectively, for AC and MAC), and 0.1 g (for both AC and MAC), respectively. The isothermal data of both sets of experiments correlated well with the Langmuir isotherm model, while the kinetic data with the pseudo-second-order model. The adsorption of AZM on both adsorbents was found to be favorable, which is evident in the values of the thermodynamic parameters (ΔH= −26.506 and −24.149 KJ/mol, ΔS = 91.812 and 81.991 J/mol K, respectively, for AC and MAC). To evaluate the effect of AC and MAC on the membrane parameters, a continuous stirred reactor was connected with ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes. High % retention and improved permeate flux (around 90%) were obtained for AC/UF, AC/NF AC/RO, MAC/UF, MAC/NF, and MAC/RO treatments. The percent retention of AZM observed for AC/UF, AC/NF AC/RO was higher than MAC/UF, MAC/NF, and for MAC/RO hybrid processes due to greater surface area of AC than MAC. Keywords: activated carbon; magnetic activated carbon; azithromycin; percent retention; perme- ate flux 1. Introduction Pharmaceutical products have been frequently found in the environment and water bodies, treated wastewater, and in potable water [1]. Azithromycin is a broad-spectrum antibiotic with bacteriostatic activity against many Gram-positive and Gram-negative bacteria. The half-life of the antibiotic is 2–4 days and it is predominantly eliminated from the body through fecal and urinary excretion [2]. The excreted antibiotics enter into the environment through wastewater [3]. The occurrence of these antibiotics in the environment may cause negative impacts on aquatic and terrestrial ecosystems [4,5]. Water 2021, 13, 1969. https://doi.org/10.3390/w13141969 https://www.mdpi.com/journal/water