Synthesis, characterisation of polyaniline–Fe3O4 magnetic nanocomposite and its application for removal of an acid violet 19 dye
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The present work deals with the development of a new method for the removal of dyes from an aqueous solution using polyaniline (PANI)–Fe3O4 magnetic nanocomposite. It is synthesised in situ through self-polymerisation of monomer aniline. Photocatalytic degradation studies were carried out for cationic acid violet 19 (acid fuchsine) dye using PANI–Fe3O4 nanocomposite in aqueous solution. Different parameters like catalyst dose, contact time and pH have been studied to optimise reaction condition. The optimum conditions for the removal of the dye are initial concentration 20 mg/l, adsorbent dose 6 gm/l, pH 7. The EDS technique gives elemental composition of synthesised PANI–Fe3O4. The SEM and XRD studies were carried for morphological feature characteristics of PANI–Fe3O4 nanocomposite. The VSM (vibrating sample magnetometer) gives magnetic property of PANI–Fe3O4 nanocomposite; also FT-IR analysis gives characteristics frequency of synthesised PANI–Fe3O4. Besides the above studies kinetic study has also been carried out.
KeywordsPANI–Fe3O4 magnetic nanocomposites Photocatalytic degradation Acid violet 19 dye SEM XRD VSM
About 15 % of the total world production of dyes is lost during the dyeing process and is released in the textile effluents (Houas et al. 2001). To reduce the risk of environmental pollution from such textile effluent, it is necessary to treat them to before discharging in environment. (Shrivastava 2012). Photosensitized degradation of coloured contaminants in wastewater on semiconductor surface is crucial (Chatterji 2004; Zhang et al. 2008; Ameta et al. 2014). Among the new oxidation methods or advanced oxidation processes (AOP), heterogeneous photo-catalysis appears as an emerging destruction technology leading to the total mineralisation of most of the organic pollutants (Imanishi et al. 2010).
In present era, the use of semiconductor metal oxides as photo-catalysts for degradation of pollutants has attracted attention of researchers. Semiconductor metal oxide Nanoparticles have been studied due to their novel optical, electronic, magnetic, thermal and mechanical properties and potential application in catalyst, gas sensors and photo-electronics devices (Grätzel 2004; Senadeera et al. 2004). Dyes are not removed by traditional methods such as biological, physical and chemical methods. Nowadays the advanced oxidation process (AOP) is used for the detoxification of contaminated dyes solution (Sato et al. 2004; Patil et al. 2012; Meshram et al. 2011; Tang et al. 2003; Jang et al. 2009). AOP has many advantages as the complete mineralisation of the pollutants are non selective processes can be used low contaminant and can be combined with other methods (del Maria 2013). Advanced oxidation processes are based on generation of reactive species through illumination of UV or solar light of some active materials. This process used to oxidise organic and inorganic pollutants (Aplin and Waite 2003).
Nowadays, ferrite has attracted considerable attention due to its narrowing band gap energy of nearly 2.1 eV (Chen et al. 2007; Singhal et al. 2013). Magnetic nanocomposite has been found to be potential alternative in future for materials with low photocatalytic activity. Degradation of organic pollutants and toxic dyes has been important aspect to study the photocatalytic efficiency of magnetic composites (Wang et al. 2005; Soltani and Entezari 2013).
The present work report is a new and simple method for removal and recovery of Acid violet 19 dye by PANI–Fe3O4 Magnetic nanocomposites used as a catalyst. Photocatalytic degradation experiment was carried out and also studied the degradation kinetics of Acid violet 19 on PANI–Fe3O4 magnetic nanocomposites.
Materials and methods
Acid violet 19 dye, Fe (NO3)39H2O, FeSO4·6H2O, NH4OH, monomer aniline, distilled water, ammonium per-sulphate [(NH4)2S2O8]. The water soluble acid violet 19 dye which has M.F. C20H17N3O9S3Na2, M.W. 585.54 gm and PANI–Fe3O4 nanocomposite was used as catalyst. All chemicals and reagents were of analytical grade purity. The structure of dye is presented in the Fig. 1b. The stock solution 1000 mg/l of an acid violet 19 dye was prepared in double distilled water, from which desired conc. of dye solution was prepared. In 50 ml of dye solution of the desired concentration, of different adsorbent dose was added and stirred with magnetic stirrer. At specific time interval suitable aliquot of the sample was withdrawn and analysed after centrifugation. The changes in dye concentration were determined by UV–Visible double beam spectrophotometer (systronics model-2203) at λ max 545 nm in our laboratory.
The Photocatalytic degradation of acid violet 19 dye was carried out in a Photocatalytic reactor with a 400-W medium pressure Mercury lamp. The reactor consists of a cylindrical Pyrex glass rector, double-walled quartz cooling water jacket to maintain the temperature and prevent the reactor from excessive heating. The reaction solution was stirred with magnetic stirrer at a constant speed. The changes in dye concentration are measured using spectrophotometer (Systronics 2203). The pH metric measurement were made on equip-tronics digital pH meter (Model-E610) fitted with glass electrode which is previously standardized with buffers of known pH in Acidic and basic media.
Preparation of Fe3O4 Nanoparticles
Fe3O4 magnetic particles were prepared by co-precipitation method. A complete precipitation of Fe3O4 was achieved under basic condition, by maintaining molar ratio of Fe(NO3)39H2O:FeSO46H2O as 1:2. In this experiment Fe(NO3)39H2O and FeSO46H2O were dissolved in 80 ml distilled water with vigorous magnetic stirring. After stirring, this solution was heated up to 80 °C, then slowly added ammonium hydroxide solution up to pH 11. At this condition complete growth of Fe3O4 crystals was observed. The resulting nanoparticles were filtered and repeatedly washed with water and then with ethanol, finally dried at 80 °C in oven for 24 h.
Preparation of PANI–Fe3O4 nanocomposite
The solution of Fe3O4 Nanoparticle, monomer aniline, and ammonium per-sulphate ((NH4)2S2O8) was prepared in distilled water with vigorous stirring at R.T. The amount of Fe3O4 and monomer aniline was taken in 1:2 ratio. The pH value was controlled during the entire experiment up to pH 11. A black precipitate of PANI–Fe3O4 was observed after 10 h. The resulting polymer nanocomposite was poured into water and filtered. Each wash step was carried out until the filtrate becomes clear and colourless. Finally, the magnetic polymer nanocomposite was washed with distilled water, ethanol, and then finally dried in oven (El-Mahy et al. 2013).
Results and discussion
Characterisation and analysis
Electron dispersive X-ray spectroscopy (EDS) analysis
Effect of catalyst dose
The effect of catalyst dose on the degradation of acid violet is studied by varying different doses of PANI–Fe3O4 nanocomposite from 2 to 6 gm\l for 20 mg/l is as shown in Fig. 7. Photocatalytic degradation of acid violet is increased from 82.1 to 95.2 with an increasing amount of PANI–Fe3O4 from 2 to 6 gm/l for contact time 80 min. As the amount of catalyst increases, number of active sites of the catalyst increases, degradation of acid violet dye also increases is shown in the Fig. 7.
Effect of pH
The photocatalytic degradation of acid violet 19 dye is studied at different pH values as it is an important parameter for reaction taking place on the particular surface. The role of pH in photocatalytic degradation of dye is studied in the pH range 1–13 at dye concentration 20 mg/l and PANI–Fe3O4 amount 6 gm\l. It is observed that the rate of photocatalytic degradation enhanced with an increase in pH up to 7 and then decreased at higher pH as shown in the (Fig. 8). At higher pH, the amine sites of polyaniline chain were deprotonated and polyaniline did not prefer the adsorption of cationic acid violet 19 dye due to electrostatic repulsion, hence rate of photocatalytic degradation decreased. Similarly at lower pH, the amine group of acid violet 19 dye was protonated therefore it could not adsorbed on the surface of PANI with +ve charges. As the rate of adsorption decreases, therefore rate of photocatalytic degradation also decreases. As in this experiment dye is first adsorbed, and then photo catalytically degraded. This reveals that maximum rate of photocatalytic degradation was observed in neutral condition.
Effect of contact time
The effect of contact time for the photocatalytic degradation of acid violet 19 dye by PANI–Fe3O4 nanocomposite is shown in the (Fig. 9). The dye is rapidly degraded in 1st 20 min and then degradation rate increases slowly and reaches equilibrium in about 60 min. The rate of degradation of dye is initially fast because it has maximum number of active sites. As the maximum concentration of dye is degraded from aqueous solution the rate of degradation reaches at equilibrium in about 60 min. The degradation of dye at equilibrium decreases from 95.2 to 82.1 % as dye concentration is increased from 20 to 60 mg/l for 6 gm/l catalyst dose.
Pseudo 1st Order
Reaction rate constant of acid violet 19 photocatalytic degradation with different Initial concentration
Amount of catalyst
Conc. of dye in mg/l
Rate const. (K)
PANI–Fe3O4 nanocomposite is successfully synthesised in situ through self polymerisation of monomer aniline.
Photocatalytic degradation of acid violet 19 dye using catalyst PANI–Fe3O4 is successfully carried. The photocatalytic degradation rate increased significantly by increasing amount of catalyst dose, while with an increasing dye concentration photocatalytic degradation rate decreases. Neutral (pH 7) condition is found, which significantly affects the degradation efficiency of acid violet 19 dye. The maximum degradation of acid violet 19 dye at pH = 7 is 95.2 % and after elution the concentration of dye is 20 mg/l.
The present study shows that conducting PANI–NiFe2O4 can be used as photo catalyst for the degradation of acid violet 19 dye from aqueous solution.
The rate of photo-degradation is found to confirm the pseudo-first-order kinetics with good correlation with R 2 values.
Authors are gratefully acknowledged to the Director UDCT, Jalgaon (M.S) for SEM, EDS, FT-IR & XRD studies. Authors are also thankful to Director of IIT Madras for VSM studies. Authors are thankful to the Vice chancellor NMU Jalgaon for providing financial support under the VCRMS project and the Principal of G. T. Patil College, Nandurbar for providing necessary laboratory facilities.
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