A sustainable technique for producing bio-based hydrogel composites with application for wastewater decontamination has been developed by researchers from KTH Royal Institute of Technology (Sweden) and Politecnico di Torino (Italy). The plant cellulose gel material spiked with carbon dots produced in a microwave can be deployed to extract heavy metals, dyes and other pollutants from water.

The hydrogel composites are derived from lignocellulose, including cellulose gum as a thickener and emulsion sourced from wood pulp or cotton processing byproducts. Graphene oxide-like carbon dots synthesized from biomass with the help of microwave heat are embedded in the hydrogel composites, which are then cured with ultraviolet light.

The harsh chemical and thermal conditions commonly used to produce graphene oxide adsorbents were replaced with lower temperature regimes to carbonize biomass. Sodium lignosulfate byproducts were reduced into carbon flakes by heating the material in water in a microwave oven at 240° C. The process yields carbon dots of about 10 nm to 80 nm in diameter, which are then mixed with the cellulose gum to form the hydrogel.

Lignocellulose hydrogel before (left) and after it adsorbed methylene blue from aqueous solution. Source: Giuseppe Melilli/KTH Royal Institute of Technology

The composites demonstrated a good affinity for adsorption of methylene blue dye and copper from water and could be regenerated and reused for several treatment cycles.

The research results are published in Sustainable Materials and Technologies.