Removal of Dyes from Industrial Wastewater using N/S Co-doped TiO2 Nanostructures

Abstract

With the development of mankind, society, science and technology, our sphere is approaching to a new horizon, but to meet the emerging stress in the current situation the cost level is going to be too high. Among these penalties of rapid growth, pollution in our ecosystem has become the major delinquent. In addition to all other requirements, the request for pure water has increased exponentially with agricultural, industrial and domestic sectors utilizing 70, 22 and 8% of the prevailing freshwater, respectively, hence resulted in the liberation of a significant amount of wastewater taking a number of toxic ‘pollutants’. Wastewater treatment now has become a major attention-seeking issue to researchers. In different manufacturing industries, commercial dyes are used in plastic, textiles, paper, leather, foodstuffs and pharmaceuticals. Synthetic dyestuffs that are extensively used in various industries, responsible for contamination of wastewater due to which approximately 10,000 synthetic dyes (e.g. triphenylmethane, anthraquinone, dichlorobenzidin and azo dyes) are increasing year after year. It is more or less investigated that the loss of reactive dyes (more than 10%) in textile processing resulted in the liberation of a significant amount of dye wastes that have a damaging effect on human health and environment. Thus the removal of hazardous dyes from wastes demands utmost attention because most of the dyes are not biodegradable easily. Adsorption has been recognized as a promising dye treatment technique due to its simplicity, substantial productivity, low cost and fast adsorbent/adsorbate interaction time. The removal efficiency of the adsorption process may reach up to 99.9%. The United States Environmental Protection Agency (USEPA) categorized adsorption as one of the most efficient wastewater treatment approaches. Titanium dioxide (TiO2) or Titania is known as an excellent adsorbent for environmental applications. Titania films possess high adsorption capacity for a large variety of dyes such as basic red 46, basic blue 41. TiO2 based nanocomposite materials have drawn the attention of investigators, due to the wide possibilities of properties modification in the field of material sciences. TiO2 doping with other materials is considered an effective strategy, in order to improve its adsorbent character and enhancing the efficiency to separate the dyes. ix This study will demonstrate the combined efforts in order to address the environmental problem. Three steps are followed in this work. In the first step, co-doped titania (NS/TiO2) adsorbent is synthesized, secondly, the synthesized adsorbents are evaluated by several characterization techniques and in the last step adsorption performance is measured. A novel hydrothermal calcination method is used for the growth of co-doped titania nanostructures using mesoporous Titanium tetra isopropoxide (TTIP), Isopropyl Alcohol (IPA) and Thiourea. The as-synthesized adsorbents are then characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Raman Spectroscopy (RS) and Brunauer–Emmett–Teller (BET). SEM expresses morphology. BET provides information about pore size, volume and surface area and FTIR and RS provide information on functional group and structure identification. The adsorption activity of as-synthesized adsorbent is analyzed by UV Vis Spectroscopy for Methyl Blue (MB), Methyl Orange (MO) and Methyl Red (MR). The adsorption isotherm is analyzed by Langmuir and Freundlich adsorption isotherm models. The adsorption efficiency of co-doped Titania nanocomposite (NS/TiO2) is much better than that of conventional and as-synthesized TiO2. The large surface area, pore-volume, small particle size and more binding sites are responsible for adsorbing a comparatively large amount of dyes. Moreover, as-synthesized NS/TiO2 adsorbent can also be used for its industrial applications to decontaminate the wastewater