The Removal of Methylene Blue by Catalytic Ozonation Process Using Alumina


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Treatment of Textile effluent is a major environmental issue these days. The presence of large amount of dyes in textile effluents is making the treatment process more challenging. Removal of dyes from the large amount of textile effluents has been a challenge for the textile industries since dyes are by default designed to retard chemical and microbial attacks. There is a growing environmental concern due to toxic and carcinogenic nature of organic dyes. Moreover, Due to chemical stability of these dyes, most of biological waste water treatment does not give fruitful/desired results. Among the dyes, the reactive dyes are a serious threat to environment due to their non-biodegradable, carcinogenic and mutagenic nature. Moreover Reactive dyes can cause serious health issues to humans and specifically marine life because the dyeing process losts about unreacted 1-15 % dye during the process, promoting eutrophication and affecting adversely on region’s environmental health. The highly colored textile waste water having high values of chemical & biological oxygen demand with high concentrations of salt, demands the effluent to be treated prior to its disposal to environment. One such dye, the usually used dye for imparting blue color to wood, silk and cotton is Methylene blue (MB).

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Following are the objectives for research under the mentioned title:

To study the methylene blue degradation efficiencies by catalytic ozonation using alumina as a catalyst;

To study the effect of various parameters such as Color, COD, pH , Ozone dose and Catalyst dose on the degradation efficiency of methylene blue.

An increase amount of refractory, toxic, mutagenic and carcinogen waste have been observed in effluents generated from process and chemical industries, leading to adverse environmental issues and potential health hazards. [3] Water is usually consumed as reaction medium and or solvent or in effluent generating industries. The organic waste include pharmaceuticals & pesticides, personal care & housekeeping products, detergents & dyes, carboxylic acids and aromatic compounds. These toxic compounds due to their low conversion efficiency becomes part of effluent. Moreover, mostly these organic compounds are chemically stable and non-biodegradable. Thus obstructing light penetration and highly affecting photosynthesis process of water born plant, if disposed in water bodies. Disturbing the ecosystem food chain and affecting the aesthetic nature badly. Exposure to these toxic contaminants have serious health hazards like nervous systems damage and primary organs problems. Birth defects and similar disorders have also observed by exposure to some pharmaceutical compounds. It is therefore, necessary to eliminate these pollutants to acceptable/permissible limits by a reasonable treatment method before disposing into open environment. [4] At present, the methods to eliminate organic matter from wastewater can be characterized into three groups:

  1. Physical Methods (such as adsorption, steam stripping, ion exchange, and solvent extraction)
  2. Chemical Methods (such as oxidation and phase transfer catalysis)
  3. Biological treatments.

The Combo of these methods are also used. One of them being advanced oxidation processes (AOPs) which is a combo of physical-chemical technologies. [5] In this era modern technologies where each day a new technology is introduced, the conventional technologies have failed to do justice to process efficiency due to high energy consumption, sludge formation, toxic resistance, larger area requirements and long residence times.

One of the method discussed before, Advanced Oxidation Processes (AOPs) are suitable for treatment of water having high concentrations of non-biological organic pollutants whereas, ozonation process is mostly considered as one of the most efficient advanced oxidation .

There are two possible way Ozone (2.07 V) a powerful oxidant, degrade organic pollutants:

  • Molecular ozone direct electrophilic attack;
  • Hydroxyl radicals indirect attract, generated by ozone decomposition.

Single ozonation as an effective oxidation treatment process, have been limited due to its several disadvantages, like:

  • Selective reactions between O3 and pollutants, slow and incomplete process
  • Low solubility and stability of ozone in water hence, low utilization rate.

Catalytic ozonation , the modified form of convention ozonation have been affective in treatment of water and waste water. It is widely used for the reducing toxic organic pollutants. Catalytic ozonation as the name suggest make use of a catalysts that enhances the ozone decomposition giving more production of hydroxyl radicals. Therefore, selective reactions problem can be solved by using a catalyst in ozonation process.

Here addressing another problem of ozonation process i.e low efficeny can be overcome by using Heterogeneous catalytic ozonation process. Where solid catalysts are used for the treatment of water and waste water. It has also gained much importance as a treatment process owing to its higher removal efficiencies. In this context several materials have been used a catalyst for the catalytic ozonation process namely:

  • Reduced graphene oxide
  • Activated carbons
  • Alumina, zeolites, TiO2
  • Metal Catalysts – Pd, Pt
  • Oxides of Transition metals – Mn, Co, Ni and of the studied catalysts, Manganese (Mn) (transition metal) supported on alumina have been really effective for degrading numerous organic compounds. It has also been suggested that the effectiveness of ozononation process e in the presence of CuO/ Al2O3 at low pH.
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