International Journal of Scientific Engineering and Science Volume 3, Issue 3, pp. 81-85, 2019. ISSN (Online): 2456-7361 81 http://ijses.com/ All rights reserved Synthesis of Ag/ZIF-67 as a Heterogeneous Catalyst for Methyl Orange Degradation in Presence of H 2 O 2 Pham Quoc Yen 1 , Le Thi Anh Thu 1 , Pham Van Toan 2 , Ho Ngoc Tri Tan 3 , Dang Huynh Giao 1,* 1 Department of Chemical Engineering, College of Engineering Technology, Can Tho University, Vietnam 2 Department of Environmental Engineering, College of Environment and Natural Resources, Can Tho University, Vietnam 3 Department of Civil Engineering, College of Engineering Technology, Can Tho University, Vietnam Abstract— A metal-organic framework Ag/ZIF-67 was successfully synthesized and characterized by several methods including X-ray powder diffraction (PXRD), Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), and Thermogravimetric analysis (TGA). The results showed that Ag/ZIF-67 had a polyhedron structure was similar with ZIF-67 and 5.1% of Ag nanoparticles was loaded into its structure. The catalytic activity of Ag/ZIF-67 was then investigated into methyl orange (MO) minerization process in presence of H 2 O 2 . High efficiency was obtained with over 99% when using H 2 O 2 concentration 0,08 mol.L -1 , methyl orange concentration 10 mg.L -1 , Ag/ZIF-67 concentration 200 mg.L -1 at 30 o C, pH 7 in 180 min. The solid and could be recycled and reused without a significant degradation in catalytic activity with the efficiency is over 90% after 3 times. Keywords— Synthesis, Ag/ZIF-67, methyl orange degradation, H 2 O 2 , catalyst, solution impregnation. I. INTRODUCTION Metal-organic frameworks (MOFs) are a class of porous coordination polymers (PCPs), promising crystalline solid- state materials [1]. Zeolitic imidazolate frameworks (ZIFs) is one group of MOFs, built by transition metal (such as Zn or Co) and imidazole compounds as lattice nodes and bridges, respectively [2]. Compared to other types of MOFs materials, ZIFs would be illustrated remarkable properties that are better thermal, hydrothermal and chemical stabilities [3, 4]. Recently, loading metal nanoparticles (NPs) techniques into ZIFs have been more and more interesting, seeing that ZIFs are shown to be suitable capability as matrices to encapsulate and support functional NPs [5]. This combination would be important development for catalyst manufacture owing to taking full the best characteristic of NPs and host matrix, maybe they can increase electrical and catalyst properties to prepare with single component material [6]. In recent years, several examples of incorporation of NPs into cavities of ZIFs systems have been reported by difference methods for preparation, such as doping Au, Pt, Ni, Pd into ZIF-8 and ZIF-90 [7-10], encapsulating Ag, Pd, Cu by ZIF-67 core-shell [6, 11-13]. NPs-ZIFs have demonstrated application potentials for catalyst and decontamination [14, 15]. For instance, Han-Qing Yu (2013) investigated to synthesize Pd@ZIF-67 that was used as heterogeneous catalyst for Cr(IV) reduction to Cr(III). In detail, the PdNPs were embedded into ZIF-67 via two periods: (i) firstly, palladium acetate (Pd(OAc) 2 ) impregnated with ZIF-67 through material’s channel; (ii) subsequently, Pd 2+ would reduce to Pd zero valent by HCOOH. This material showed high catalytic performance and could be reused for ten times [6]. Methyl orange (MO) is an azoic organic dye that is broadly consumed in industry. Like many other dyes of its class MO on inadvertently entering the body through ingestion, metabolizes into aromatic amines by intestinal microorganisms [16]. It is also demonstrated to have acute toxicity to humans and ecosystems. To date, many methods have been carried out to decontaminated the present of MO in wastewater such as Fenton processes [17, 18], H 2 O 2 /UV [19]. They would be shown effective solution but the oxidizing agent or catalyst of those methods is not able to recycle. In this paper, we propose the process to mineralize MO using Ag/ZIF-67 in presence of H 2 O 2 . This method is also based on the attack of hydroxyl radicals ( ° OH) on MO. Hydroxyl radicals work as extremely strong oxidizing agents with E 0 = 2.8 V/NHE at room temperature and atmospheric pressure [19], which is created by the catalysis of Ag NPs on ZIF-67 surface for H 2 O 2 decomposition. Here we report a new method to prepare Ag/ZIF-67, its catalytic capacity for MO degradation and affective factors on this process. II. MATERIALS AND METHODS A. Material Cobalt (II) nitrate hexahydrate (Co(NO 3 ) 2 .6H 2 O) 99.99%, 2-methylimidazole (C 4 H 6 N 2 ) 99%, methanol, silver nitrate (AgNO 3 ) >99%, formic acid (HCOOH), acetone (CH 3 COCH 3 ) were purchased from Sigma-Aldrich, methyl orange (C 14 H 14 N 3 NaO 3 S), hydrogen peroxide (H 2 O 2 ) were purchased from Xi long scientific Co., Ltd, China. B. Preparation of ZIF-67 ZIF-67 was synthesized according to previous report with the ratio of Co 2+ and 2-HMim is 1:4 [6, 20]. Briefly, 0.717 g cobalt nitrate hexahydrate (0.0025mol) and 0.821 g 2-methyl imidazole (0.01mol) were respectively dissolved in 25 mL methanol. Then 2-methyl imidazole solution was gradually added into cobalt salt solution. The mixture was stirred by magnetic stirring during 10 mins, and aged at ambient temperature over 24 h. After that, the purple precipitation was obtained by centrifugation at 6000 rpm within 8 mins. The