Cationic Dye Treatment Using Local Tunisian Iron Tailings for Synthetic and Textile Wastewater

In this study, local iron tailing mining waste (MW) from northern Tunisia, composed of hematite, goethite, kaolinite, illite, quartz and calcium sulphate, was used as a natural by-product for wastewater treatment. A synthetic solution of Methylene Blue (MB) and a textile wastewater sample (TW) were both studied using dual procedures: adsorption and Fenton processes in order to remove MB as a cationic dye. Experimental parameters (pH, initial concentration, MW dosage, thermal activation of MW, H2O2 dosage and contact time) were varied in order to achieve the ultimate discolouration results. By using 0.1 g of raw MW or MW thermally activated at 400 ºC/3 h (MW400), (removal efficiency of MB solution was 90% and 83%, respectively, after 120 min of contact time, through an adsorption process. By reducing the MB solution pH from 7 to 3, the discolouration efficiency reached 20% using 0.02 g MW400, compared to pH 7 and pH 9, 33 and 37%, respectively. When 20 ml of H2O2 was added, after 420 min of contact time through a Fenton process, the discolouration value was 85% using 0.4 g of MW400. TW treatment results provided 30% discolouration efficiency using MW400 in adsorption process, and 79% using 20 ml of H2O2. There was a good fit with a pseudo-second-order (K2) kinetic model; values for MB (R2 = 0.997) and TW (R2 = 0.998) show that MW could be used in both raw and calcined form, in both adsorption and Fenton process, for dye removal from aqueous solutions. This natural iron-rich waste by-product shows great potential for chemical adsorbent and catalyst applications and good results were achieved compared to other research studies.