Textile dye removal by natural clay--case study of Fouchana Tunisian clay

A significant amount of unused dyes remain in textile industry wastewater, the treatment of which presents a great challenge, particularly in semi-arid countries where water resources are of great concern. Liquid-phase adsorption is highly efficient for the removal of dyes and adsorbents, for example, activated carbons are used to treat wastewater, but are expensive. Clays are cheaper and several works have showed their high pollutant adsorption capacity in cases of environmental problems. The aim of this work is to present the use of clay as a means of textile wastewater treatment and colour adsorption. The adsorbent used in this study is natural clay from the Fouchana region (Tunisia), which contains 60% smectites, 30% kaolinite and 10% illite, in which the cation-exchange capacity is about 50 meq/ 100 g of clay. Two types of waters were treated: one from a leaching textile industry and another from a dyeing industry. Moreover the treatment by clay was compared to the treatment by a coagulation flocculation standard method. The experimental results show that the treatment by natural clay is more efficient than the conventional treatment by coagulation flocculation. It allowed decolorization of the dye effluent and a decrease down to 97% for biochemical demand for oxygen, 93% for suspended matter, 95% for chemical demand for oxygen and 76% for the spectral absorption coefficient. Thus, the quality of dye wastewater has reached the Tunisian standards of releases (NT 106.02 and 106.03, 1989), and as such it makes it possible to test wastewater at the industrial scale.