Removal of toxic nitrate ions from drinking water using conducting polymer/MWCNTs nanocomposites
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ORIGINAL PAPER
Removal of toxic nitrate ions from drinking water using conducting polymer/MWCNTs nanocomposites Mohammad Reza Nabid • Roya Sedghi • Roghayeh Sharifi • Hossein Abdi Oskooie Majid M. Heravi
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Received: 6 September 2012 / Accepted: 18 November 2012 / Published online: 29 November 2012 Ó Iran Polymer and Petrochemical Institute 2012
Abstract New application of conducting polymers as stable nanocomposites for nitrate ion exchange materials in water and wastewater treatment and for environmental protection is introduced in this work. The nanocomposites of multi-walled carbon nanotubes (MWCNTs) with different polymers such as: polyaniline (PANI), polypyrrole (PPY), poly(1,8-diaminonaphthalene) [P(1,8-DAN)] and poly(2-vinylpyridine) (P2VP) were synthesized with different dopants as effective and reusable nanocomposites for nitrate removal from drinking water. Nitrate anions at toxic concentrations were removed from water using ion exchange mechanism without any toxic byproducts. The obtained results demonstrate that effective ion exchange occurs between NO3- and Cl-. There are some protonated heteroatoms in polymer chains that are bonded with anions of dopants and their counter ions in nanocomposites. These dopant anions on the =NH?– groups of polymers can be exchanged with NO3- in water. Adsorption of NO3- on polymer/MWCNTs nanocomposites showed dependency to some parameters. Different experimental parameters such as pH and temperature of the sample, polymers dopant, and the ratio of polymer to MWCNTs in nanocomposites affect the amount of nitrate removal. The highest removal efficiency was achieved at 1.20 g L-1 of PANI/ MWCNTs (3:1) nanocomposite, pH = 6.5 and ambient temperature. After five successive cycles of nitrate
M. R. Nabid (&) R. Sedghi R. Sharifi Department of Chemistry, Shahid Beheshti University, 19839/63113 Tehran, Iran e-mail: [email protected] R. Sedghi H. A. Oskooie M. M. Heravi Department of Chemistry, School of Science, Azzahra University, Vanak, Tehran, Iran
removal, this parameter was still up to 70 % compared to the first run (up to 80 %). Keywords Nitrate removal Conducting polymer/ MWCNTs nanocomposites PANI/MWCNTs nanocomposite Ion-exchange Drinking water
Introduction The nitrate ion in groundwater is becoming an environmental crisis of major concern became its high toxicity causes cancer and methemoglobinemia [1, 2]. Man-made nitrate release into environment includes inorganic fertilization and animal manures on cropland. The other important sources of nitrate are industrial and sanitary waste water, vegetable residues and compost, as well as rainfall and spontaneous nitrification of atmospheric nitrogen by the nitrification bacteria. The dissolved nitrates are filtrated through the ground by rainfall or irrigation contaminating phreatic waters. Nitrates consumed with drinking water can be converted into nitrites in human body thus causing health problems. The increasing rigorous nature of the drinking water quality standard, 50 mg/L in the European Union or
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