Abstract
Results of investigation on adsorption of Mn2+ from aqueous solution by manganese oxide-coated hollow polymethylmethacrylate microspheres (MHPM) are reported here. This is the first report on Mn-coated hollow polymer as a substitute for widely used materials like green sand or MN-coated sand. Hollow polymethylmethacrylate (HPM) was prepared by using a literature procedure. Manganese oxide (MnO) was coated on the surface of HPM (MHPM) by using the electroless plating technique. The HPM and MHPM were characterized by using optical microscopy (OM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Optical and scanning micrographs were used to monitor the surface properties of the coated layer which revealed the presence of MnO on the surface of HPM. TGA showed the presence of 4-5% of MnO in MHPM. Adsorption isotherm studies were carried out as a function of pH, initial ion concentration, and contact time, to determine the adsorption efficiency for removal of Mn2+ from contaminated water by the synthesized MHPM. The isotherm results showed that the maximum adsorption capacity of MnO-coated HPM to remove manganese contaminants from water is 8.373 mg/g. The obtained [Formula: see text] values of Langmuir isotherm and Freundlich isotherm models were 1 and 0.87, respectively. Therefore, [Formula: see text] magnitude confirmed that the Langmuir model is best suited for Mn2+ adsorption by a monolayer of MHPM adsorbent. The material developed shows higher adsorption capacity even at a higher concentration of solute ions, which is not usually observed with similar materials of this kind. Overall findings indicate that MHPM is a very potential lightweight adsorbent for removal of Mn2+ from the aqueous solution because of its low density and high surface area.
Highlights
Heavy metal contamination of water bodies from improperly disposed industrial wastes is a serious environmental problem across the world
The Hollow polymethylmethacrylate (HPM) and manganese oxide-coated hollow polymethylmethacrylate microspheres (MHPM) were characterized by using optical microscopy (OM), scanning electron microscopy (SEM), Fouriertransform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA)
The isotherm results showed that the maximum adsorption capacity of Manganese oxide (MnO)-coated HPM to remove manganese contaminants from water is 8.373 mg/g
Summary
Heavy metal contamination of water bodies from improperly disposed industrial wastes is a serious environmental problem across the world. Some manganese compounds are used in fertilizers, varnish, and fungicides and as livestock feeding supplements. All these activities lead to anthropogenic causes for Mn contamination of water sources. “Mn” is present in different oxidation states such as Mn2+, Mn4+, or Mn7+ (USEPA, 1994) [4]. It is generally present in groundwater as Mn2+ and is considered a pollutant beyond a certain limit, because of its organoleptic properties. According to the World Health Organization, the maximum acceptable “Mn” concentration in drinking water is 0.05 mg/l [WHO, 2011] [5, 6].
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