Characterization and Application of Biochar from Spent Fermentation Sludge of Coir Wastes in Removing Malachite green from Effluent Water

Lignin rich solid residues after saccharification during the production of ethanol from lignocellulosic substrates are major concern during past times. These solid residues left after the saccharification of Coir pith and Bit fiber waste are pyrolysed at 350 oC to yield biochar, which has been characterized and its potential for removal of Malachite Green, a dye present in the effluents from coir product manufacturing units are studied. FTIR and XRD spectra revealed the diverse functional groups present on the surface of biochar. SEM images showed the porous structure of the biochar. A maximum dye removal efficiency of 99.5% was achieved using Coir Pith Biochar (1 %) within 24 hours of treatment at a dye concentration of 100 mg/l. The removal efficiency was 99.4 % using Bit Fiber Biochar (0.8 %) in the same treatment period. The efficiency of removal was enhanced on adjusting the pH to 4 at which the dye removal of 99.6 % and 99.7 % was achieved using Bit fiber biochar and Coir pith biochar respectively. The residence time was significantly reduced to 2 and 4 hours respectively for bit fiber and coir pith biochar at pH 4 and hence the produced biochars are cost effective adsorbents for removal of dyeing effluents in wastewater. The adsorption fits into pseudo-second order kinetics and is well described by langmuir isotherm model. This would also facilitate the sustainable use of spent solid substrates left after lignocellulosic ethanol production in a more economical way.