Dye removal from simulated and real textile effluent using laccase immobilized on pine needle biochar

Abstract

Textile industries generate huge amount of water containing harmful azo dyes that have known carcinogenic and mutagenic toxicities. Removal of these azo dyes is an important step in the treatment of wastewater. This work evaluates the potential application of enzyme immobilized biochar for the removal of azo dyes from real and simulated textile effluents. The simulated textile effluent was prepared using azo dyes Congo red, Malachite green and their mixture. Dye removal studies were conducted in batch studies using laccase immobilized biochar and optimization of immobilization was achieved through response surface methodology. In the case of simulated effluent, higher dye removal efficiencies were obtained when added separately (73.8 % for Malachite green dye and 88.1 % for Congo red) in comparison to when mixed together (59.3 % for Malachite green dye and 78.7 % for Congo red). In the case of real textile effluent, the dye removal through an enzyme immobilized system with 100 % removal efficiency was obtained for one of the dye peaks while it was 35.7 % for the other dye present in the effluent along with 33.3 % COD removal. The real textile effluent was analyzed by GC–MS and the presence of one of the metabolite phenol,2,4-bis (1,1-dimethyl ethyl) in the GC–MS spectra indicated degradation of dye Mordant Black. Thus, an enzyme immobilized biochar system can be used for simultaneous dye adsorption and degradation of toxic azo dyes from real effluents.