Synchronous role of coupled adsorption-photocatalytic degradation of Direct Red 80 with nanocrystalline TiO2-coated non-woven fibres materials in a static batch photoreactor

The aim of this research is the application of the industrially produced TiO2-coated non-woven fibres for coupled adsorption-photocatalytic degradation of synthetic textile dye Direct Red 80. The adsorption efficiency of DR80 samples has been studied in the dark. The tested TiO2 catalyst, that exhibited significant adsorption capacities due to its high specific surface area, proven to be effective photocatalyst for photodegradation of the studied dye. The effect of the experimental parameters, such as initial dye concentration, pH and temperature on the photodegradation, were investigated. The effect of inorganic ions (Na2SO4, NaCl, NaNO3, CH3COONa, NaHCO3 et Na2HPO4) was also studied. A pseudo-first-order kinetic reaction was illustrated using the Langmuir-Hinshelwood model and rate constant and adsorption equilibrium constant were calculated (k = 1.1873 mg/L.min and K-LH = 0.0660 L/mg, respectively). The highest photodegradation efficiency is obtained at pH = 3. The presence of HPO42-, HCO3-, CH3COO ions decreased the photodegradation rate, however, Cl-, NO3- increased the reaction rate. The degradation of pollutant has been monitored by spectrophotometry. To evaluate the extent of mineralization of the studied dye, Chemical Oxygen Demand (COD) measurements during the experiment were conducted, where the important abatement of 88.64% was reached after 7 h of the treatment. The identification of the reactive intermediates products by using high performance liquid chromatography (HPLC), allowed suggesting the oxidative degradation mechanism for Direct Red 80 dye.