Preparation of a distillers’ grains derived lignin-chitosan adsorbent for enhanced distillery wastewater treatment

The distillers’ grains and wastewater produced by alcohol fermentation process pose a threat to the ecological environment. This study has designed a method of treating waste with waste, which uses the lignin from distillers’ grains as the base and combining with chitosan to prepare an efficient adsorbent for distillery wastewater treatment. The prepared lignin-chitosan adsorbent was characterized by various methods, its surface was rough and had abundant functional groups, which facilitated the adsorption of pollutants. The COD, TP, TN and NH4+-N were selected as the typical wastewater indicators to evaluate the treatment effect of the adsorbent on the distillery wastewater. The results showed that lignin-chitosan adsorbent reached adsorption equilibrium for the four pollutants at 140 min, and the removal rates of COD, TP, TN and NH4+-N were 90%, 92%, 86% and 85%, respectively. The adsorption process was confirmed to be spontaneous, endothermic monolayer chemical adsorption, with the involved adsorption mechanisms including electrostatic attraction and chemical complexation. Moreover, the adsorbent still maintained a pollutant removal efficiency of over 80% even after 5 consecutive adsorption-desorption cycles. These findings indicate its potential for large-scale applications and promise as a green alternative to activated carbon or synthetic adsorbents.