Lignin Smart Nanoparticles for Effective and Eco-Friendly Resource Recovery from Wastewater: Status, Challenges, and Opportunities
Raisa Carmen Andeme Ela, Patricia A. Heiden
Abstract
High Resolution Image Download MS PowerPoint Slide The overexploitation of finite natural resources and anthropogenic pollution pose a threat to economic security and human health. One approach for tackling these challenges is the development of effective, accessible, low-cost, bioderived, and eco-friendly technologies for the recovery of resources from wastewater. Wastewater contains resources of appreciable market value, including metals, pesticides, inorganic nutrients, dyes, and per- and polyfluorinated substances (PFAS). Established technologies, such as low-pressure membranes, biological treatments, and oxidation, are ineffectual, while more intricate technologies such as customized granular activated carbon and anion exchange resins suffer predominantly from high fouling rates and operating costs, which eventually reduce the effectiveness of resource recovery; thus, these limitations motivate the development of experimental technologies. Green, biopolymeric, smart lignin nanoparticles are potential candidates growing in popularity for their effective recovery of resources from wastewater via adsorption, as lignin-based nanoparticles with metal adsorption capacities higher than 40 mg/g have been reported. In addition, employing lignin nanoparticles for this purpose will promote the circular economy of biorefineries and support the sustainable development of nations. Nonetheless, the valorization of lignin through nanotechnology is limited by the inhomogeneity of technical lignins and the resultant nanoparticles. For instance, the physical (e.g., surface area and electrostatic charge) and chemical (e.g., concentration of hydroxyl and carbonyl groups) properties of the lignin precursor will determine the affinity of the resultant nanoparticles to specific metal ions and their adsorption capacity. Hence, a profound understanding of the relationship between lignin derivation and nanoparticle synthetic methodology with resultant nanoparticle properties (e.g., hydrodynamic size) and performance (i.e., adsorption capacity) is needed to advance the adoption of lignin nanoparticles in sustainable industrial wastewater treatment. Alas, reviews of this nature are lacking. To fill this gap, this perspective reflects on the state-of-the art techniques for lignin nanoparticle synthesis and their application in the retrieval of various substances from aqueous environments, highlighting the properties–performance correlations, the specificity of the nanoparticles, and their comparative performance against established and laboratory-scale technologies. Ultimately, standardized strategies will be needed to control the functionality of lignin nanoparticles (e.g., hydrodynamic size and programmable morphology) to enhance the effective recovery of valuable resources from copious and diverse wastewater resources.