Adsorptive removal of methylene blue from aqueous solutions using lignocellulosic waste materials and biological treatment of dye-adsorbed biosorbent

In this study different lignocellulosic waste materials (brewers’ spent grain and poplar sawdust) were tested as biosorbents for the removal of cationic dye methylene blue from aqueous solutions. The effects of initial dye concentration (5, 15, 25 and 50 mg L-1), adsorbent concentration (5, 10, 15 and 20 g L-1), temperature (25 and 35 °C) and solution pH (3.5, 5.5 and 7.5) on dye removal were investigated. For both tested biosorbents dye removal was rapid within the first 60 min of contact time. The percentage dye removal increased with increase in adsorbent concentration and decrease in the initial dye concentration. The percentage of methylene blue adsorptive removal from 15 mg L-1 aqueous solution concentration (V = 100 mL, adsorbent = 10 g L-1, t =25 °C, contact time 300 min) was over 90% for both tested biosorbents. The temperature had no significant effect on the percentage removal while the decrease in pH caused reduction of percentage removal of methylene blue when brewers’ spent grain was used as biosorbent. Solid-state fermentation of dye-adsorbed brewers’ spent grain was carried out for 30 days using white-rot fungus T. versicolor CCBAS AG613. The visible decolourisation of samples was observed, i.e. a continuous increase of total colour change and colour intensity change of fermented samples compared to their abiotic controls was determined.