Adsorption and catalytic degradation of Tartrazine in aqueous medium by a Fe-modified zeolite

Abstract

Azo dyes, as Tartrazine (T), are one of the rawest materials in food, pharmaceutical and textile industries. Many dyes are difficult to degrade due to their complex structure and xenobiotic properties. Although adsorption is considered an effective, efficient, and economic method for water purification, degradation of organic pollutant like synthetic dyes by using advanced oxidation processes (AOPs), as Fenton process, has become increasingly significant during last decades. However, as Fenton process requires ferrous salt for the oxidation reaction to take place, the iron sludge formed after the reaction, has to be removed before discharging. A novel composite material, which is referred to as iron-loaded natural zeolite (NZ-A-Fe), was used for the removal of Tartrazine (T) from water through the combined adsorption and heterogeneous catalysis. Since the adsorption step determines the rate in heterogeneous catalytic processes, its study becomes necessary for understanding the degradation mechanism. The suitability of Langmuir and Freundlich isotherms to the equilibrium data was investigated in the solid-liquid system. The equilibrium adsorption capacity (qe) increases with the increase of the initial concentration of T. The pseudo-second-order model can well describe the adsorption process of T on NZ-A-Fe, where k2 = 0.246 g(mg.min)−1is the rate constant for adsorption process. Degradation kinetics can be described using the classical pseudo-first order. Tartrazine degradation was high between 90 and 95% for [H2O2] /[T] = 37 for [T] = 10 mg/L. The novelty of this work is the simultaneous adsorption and Fenton degradation using a supported catalyst NZ-A-Fe that facilitates the design of filters for wastewater treatment.