نانومواد مغناطیسی اصلاح شده با پلی لیزین برای حذف کارآمد رنگ های آنیونی از آب A magnetic nanomaterial modified with poly-lysine for efficient removal of anionic dyes from water

۱٫ Introduction Dye is one of the most significant identified contaminant among the various pollutants of wastewater because of its high toxicity and possible accumulation in the environment. At the same time, organic dyes are extensively used in various branches such as textile, paper, printing, color photography, pharmaceutical, leather, cosmetics, plastic and other industries [1]. Many of these dyes are carcinogenic, mutagenic and teratogenic, so they are toxic to human, microorganisms and fish species. Removal of dyes from wastewater becomes environmentally important [2]. So far, several technologies, including adsorption, coagulation, flocculation, advanced oxidation processes, ozonation, membrane filtration and biological treatment, have been developed and implemented for the purpose of removing the dyes from wastewater [3,4]. Adsorption is an attractive method for the removal of organic dye because of its low cost [5]. Therefore, many adsorbents such as activated carbon [6], kaolin [7], montmorillonite clay [8], waste red mud [9], fullers earth and fired clay [10], were reported to decolorize wastewater. As adsorbent, magnetic nanomaterial possessing large surface areas, unique magnetic properties and low cost, has become an increasingly popular tool in various fields. Because Fe3O4 nanoparticles are biocompatible, low toxic, easily synthesized, particularly economic and environmental friendly [11], many adsorbents were synthesized through surface modification of Fe3O4 nanoparticles with diverse organic compounds. However, a few papers have reported on the adsorption of dyes by the magnetic particles cross-linked with amino acid until now. In our previous work, we reported four kinds of magnetic adsorbents for removing organic dyes [12–۱۵]. The magnetic adsorbent modified with lysine (Fe3O4@GPTMS@Lys) could remove cationic and anionic dyes. However, the maximum adsorption quantity (qm) for anionic dye is below 100 mg/g [15]. In this work, Fe3O4 nanoparticles modified with poly-lysine (Fe3O4@GPTMS@P-Lys) could enhance the maximum adsorption capacity for various anionic dyes including methyl blue (MB), orange I (OR-I), amaranth (AM) and acid red 18 (AR-18) (Fig. 1), because the number of amino group influences qm for anionic dyes and poly-lysine contains much more amino groups than lysine. We have studied the adsorption isotherms, kinetics, desorption and reuse of the MNPs. Furthermore, the Fe3O4@GPTMS@P-Lys MNPs possess high surface areas which lead to higher adsorption capacity and strong superparamagnetic properties that can be handled in an external magnetic field [16]. ۲٫ Experimental ۲٫۱٫ Apparatus and reagents All reagents were of analytical reagent-grade and were used as supplied. Ferric chloride (FeCl36H2O), ferrous sulfate (FeSO47H2O), poly-lysine, anhydrous sodium carbonate (Na2CO3) and four organic dyes acid red 18 (AR-18), orange I (OR-I), methyl blue (MB), amaranth (AM) were purchased from Sinopharm Chemical. Sodium hydroxide (NaOH) and toluene were from Tianjin Guangcheng Chemical. 3-Glycidoxypropyltrimethoxysilane (GPTMS) was from J&K Chemical. Aqueous solutions of organic dyes were prepared with deionized water. 2.2. Characterization The particle size and morphological characteristics of the MNPs were detected with a transmission electron microscope (TEM, JEM-1011). Infra-red (IR) spectra were recorded with an IR spectrophotometer Bruker VERTEX 70 FT-IR (Germany). The magnetic properties of the MNPs were analyzed by a vibrating sample magnetometer (VSM, JDM-13E). Thermo gravimetric analysis (TGA) involved use of an SDTQ600 thermo gravimetric analyzer (USA) at 10 C/min under nitrogen flow. A Bruker D8 Advance X-ray diffraction analyzer (Germany) with Cu Ka radiation was used for Xray diffraction (XRD) measurements. pH values were measured with a PHS-3C pH-meter (Tianyou, Shanghai). A UV-4100 spectro photometer (Hitachi) was used to determine organic dyes concentration in solution. Zeta potential of synthesized materials was measured with Zeta PALS (USA). The specific surface area and pore size distribution were performed with Surface Area and Porosity Analyzer (ASAP 2020 HD88). X-ray photoelectron spectroscopy (XPS) was recorded on ESCALAB 250 (ThermoFisher SCIENTIFIC).