Magnetic Fe 3 O 4 nanoparticles for adsorptive removal of acid dye (new coccine) from aqueous solutions Chih-Huang Weng, Yao-Tung Lin, Chia-Ling Yeh and Y. C. Sharma ABSTRACT Chih-Huang Weng (corresponding author) Chia-Ling Yeh Department of Civil and Ecological Engineering, I-Shou University, Da-Hsu Township, Kaohsiung 84008, Chinese Taiwan E-mail: chweng@isu.edu.tw Yao-Tung Lin Department of Soil and Environmental Sciences, National Chung Hsing University, TaiChung 40227, Chinese Taiwan Y. C. Sharma Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi 221 005, India The ability of magnetic Fe 3 O 4 nanoparticles (MFN) to remove new coccine (NC), an acidic dye, from aqueous solutions was studied. Parameters including ionic strength, pH, and temperature were evaluated. MFN, prepared by precipitation method, exhibits an average particle size of 12.5 nm, specific surface area of 85.5 m 2 /g, and pH zpc of 5.9. Results of kinetic adsorption experiments indicated that the pseudo-second-order rate of adsorption increased with increasing initial NC concentration. Findings also revealed that the equilibrium data could be fitted into Langmuir adsorption isotherm. The adsorption is favored at low pH, high temperature, and low ionic strength, whereupon a maximum adsorption capacity of 1.11 £ 10 24 mol/g was determined for NC. Thermodynamic functions indicated that the adsorption process is spontaneous and exothermic in nature. Tests of regeneration showed that after 5 regeneration cycles the adsorption capacity of NC decreased to 35% to its original capacity. Key words | adsorption, dye, iron, magnetite, nanoparticles, new coccine INTRODUCTION Nanoparticles have drawn significant attention of scientific researchers due to their extremely small size, surface reactivity, and high specific surface area. Because of the advantages namely: production in large quantity via sol-gel method, easy separation by external magnetic field, fast contaminant removal, and recovery of metal from aqueous solution, extensive studies have been done on possible application of magnetic nanoparticles in adsorption process (Chen & Huang 2004; Hu et al. 2005; Uheida et al. 2006). Because the size of nanoparticles is too small to be worked on a packed column system, a stirred batch suspension system would be appropriate for the application of nanoparticles in the adsorption process. The objective of this study is to investigate the adsorption characteristics of an anionic azo dye, new coccine (NC) onto magnetic Fe 3 O 4 nanoparticles (MFN). NC was chosen as a surrogate in the anionic dyes as it is an azo dye which is commonly used in industries. Parameters that may affect the adsorp- tion, including concentration of NC, ionic strength, pH and temperature, were studied. Thermodynamic parameters for such systems were also evaluated. Regeneration of MFN was also performed. MATERIALS AND METHODS Dye and magnetic Fe 3 O 4 nanoparticles All reagents used in the experiments were of analytical grade chemicals. The azo dye used in this study, NC or acid red 18, was purchased from Koch-Light Laboratories Ltd., England. NC has a chemical formula of C 20 H 11 N 2 Na 3 O 10 S 3 (Figure 1). Solution NC concentration was determined using a spectrophotometer (HACH DR-2010, USA) at a wavelength of 505 nm. The synthesis of MFN was carried out by coprecipitating Fe 2 þ and Fe 3 þ ions by NH 4 OH solution and treating under hydrothermal conditions (Liao & Chen 2002). The chemical precipitation was achieved by adding NH 4 OH solution (29.6%) into a 100 mL solution of doi: 10.2166/wst.2010.310 844 Q IWA Publishing 2010 Water Science & Technology—WST | 62.4 | 2010 Downloaded from https://iwaponline.com/wst/article-pdf/62/4/844/446476/844.pdf by guest on 24 May 2020