Removal of arsenic and iron from mine-tailing leachate using chitosan hydrogels synthesized by gamma radiation |
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| Authors: | Juan Carlos Burillo Javier Castro-Larragoitia Guillermina Burillo Alejandra Ortega Nahum Medellin-Castillo |
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| Institution: | 1.Facultad de Ingeniería,Universidad Autónoma de San Luis Potosí,San Luis Potosí,Mexico;2.Instituto de Ciencias Nucleares,Universidad Nacional Autónoma de México, Ciudad Universitaria,Mexico City,Mexico;3.Facultad de Ingeniería, Centro de Investigación y Estudios de Posgrado,Universidad Autónoma de San Luis Potosi,San Luis Potosí,Mexico |
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| Abstract: | Mine residue and leachate were sampled from an acid mine drainage site near Arroyo San Pedro, which is one of the oldest abandoned mine districts in San Luis Potosi, Mexico, and characterized by X-ray diffraction and inductively coupled plasma-optical emission spectroscopy, confirming the presence of Fe, As, and SO4 2?. To address this problem, chitosan network (net-CS) and chitosan network-N-vinylcaprolactam/N–N-dimethylacrylamide (net-CS)-g-NVCL/DMAAm hydrogels were synthesized and used as adsorbents of the different ions present in the aforementioned leachate by batch equilibrium procedure. Kinetics, isotherms, and ions dissolved in leachate were evaluated. The gels showed the highest adsorption capacity for As and Fe ions. The adsorption capacity of the net-CS hydrogels for As (V) and Fe(III) was 0.786 and 76.85 mg/g, respectively, attained after 50 h. The surface of the hydrogels was investigated by scanning electron microscopy and Fourier transform infrared spectroscopy, before and after the adsorption process, where the presence of a bond between the hydrogels and heavy metals ions, which is commonly observed in organic groups, was observed. In addition, Freundlich and Langmuir adsorption isotherms constants were determined for the As and Fe ions, and it was found that the Freundlich isotherm, with a first-order pseudo model, better fitted the adsorption process, indicating heterogeneous sorption, and the retention process occurred by chemisorption. The results from the Geochemist´s Workbench (GWB) software program revealed that arsenates, such as H3AsO4, H2AsO4 ?, as well as Fe++, FeSO4(aq) and FeOH+ were the common aqueous species found in the leachate at pH = 2.9. |
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