The present study aims to establish NaOCl as a potential oxidant in the COD removal of Acid Orange 8 using UVC light (λ = 254 nm) and Fe2+ as catalysts. The different systems used in this study are NaOCl, Fe2+/NaOCl, UV/NaOCl, and Fe2+/NaOCl/UV. All these process were found to be operative in acidic, neutral and basic medium. The initial decolorisation and COD removal efficiency (CODeff) for different systems follow the order: Fe2+/NaOCl/UV > UV/NaOCl > Fe2+/NaOCl > NaOCl. Nevertheless, NaOCl can alone be used in the treatment process considering its CODeff to the extent of 95% in 90 min. The change in pH of the solutions after treatment is an important observation - for non-UV systems it remained around 11.0 and 7.0 in other systems. Thus, UV systems are environmental benign. The effect of various anions on CODeff was tested in Fe2+ systems. Presence of F- ions were found to accelerate CODeff in both the systems. However, the effect is more pronounced in Fe2+/ NaOCl/UV, where complete CODeff was observed in the presence of 9.0 gl-1 of F-. The COD removal kinetics for all systems was studied using zero-order, first-order, second-order, and BMG kinetic models. BMG model was found to be more suitable among all and is in good agreement with CODeff of all systems. It is, therefore, established that NaOCl can serve as a powerful oxidant in the advanced oxidation process.
Azo Compounds , Iron , Oxidants , Sodium Hypochlorite , Ultraviolet Rays , Water Pollutants, Chemical , Water Pollutants, Chemical/chemistry , Catalysis , Oxidants/chemistry , Sodium Hypochlorite/chemistry , Iron/chemistry , Azo Compounds/chemistry , Kinetics , Biological Oxygen Demand Analysis , Benzenesulfonates/chemistry , Hydrogen-Ion Concentration , Waste Disposal, Fluid/methods , Oxidation-Reduction
The removal of mixture of two azo dyes, Acid blue 29 and Ponceau xylidine, was studied by heterogeneous Fenton and Fenton-type processes using hydrogen peroxide and sodium persulphate as oxidants in the presence of and nano and micro- particles as catalysts. The synthesised nano- particles were characterised using analytical techniques viz. FT-IR, TEM, EDX, powder XRD and VSM. We have examined the effects of particle size on the COD removal efficiency and the reusability of the catalyst after optimising pH, and concentrations of catalyst and oxidant. Combination of nano- and hydrogen peroxide possessed higher COD removal efficiency, which was accelerated in acidic pH and inhibited at pH > 6. Total consumption of hydrogen peroxide confirmed the efficiency of the optimised parameters. The mechanism of the formation of intermediate ions and products are proposed. COD removal and consumption of hydrogen peroxide follow pseudo-first-order kinetics. The toxicity of the solutions was assessed using Aliivibrio fischeri light loss and Escherichia coli growth inhibition assays. Both the assays showed different toxicity levels for the same solution.
Coloring Agents/chemistry , Hydrogen Peroxide/chemistry , Iron/chemistry , Aliivibrio fischeri/drug effects , Azo Compounds/chemistry , Azo Compounds/isolation & purification , Azo Compounds/pharmacology , Catalysis , Coloring Agents/isolation & purification , Coloring Agents/pharmacology , Escherichia coli/drug effects , Ferric Compounds/chemistry , Hydrogen-Ion Concentration , Kinetics , Metal Nanoparticles/chemistry , Naphthalenes/chemistry , Naphthalenes/isolation & purification , Naphthalenes/pharmacology , Oxidation-Reduction , Particle Size , Sodium Compounds/chemistry , Sulfates/chemistry
