Lignin utilization for the removal of microplastic particles from water

The focus of the research was to evaluate the use of lignin from different sources as an agent for the removal of diverse types of microplastics when present in wastewater. Organosolv lignin was obtained from three different sources (Miscanthus sp., pine bark and solid anaerobic digestates from Organic Fraction of Municipal Solid Wastes) by an ethanol-based organosolv treatment carried out in a pressurized stirred-tank reactor. The lignins obtained were evaluated as an adsorbent for diverse types of microplastics: High-density polyethylene (HDPE), Polystyrene (PS), Expanded Polystyrene (EPS), and Polypropylene (PP). All lignins used had the capacity to capture plastic particles from all plastic types, but a differential absorbance potential was found both for plastic types and lignin samples. EPS was the least adsorb type for all lignin sources, with the remaining plastics presenting equivalent results. Pine bark lignin was the best adsorbent among the tested feedstocks, always presenting the best performance for all plastic types. The direct utilization of organosolv hydrolysates, avoiding lignin recovery presented a similar behaviour. These results open the possibility to develop new natural, plant-based, adsorbents for microplastic removal from contaminated wastewater.