Photocurable “all-lignocellulose” derived hydrogel nanocomposites for adsorption of cationic contaminants

Removal of contaminants from wastewater is one key element for the development of sustainable society. Here, innovative “all-lignocellulose” derived photo-curable hydrogel nanocomposites based on methacrylated carboxymethyl cellulose (M-CMC) and lignosulfonate-derived carbonaceous products were successfully designed. The carbon products were synthesized by microwave-assisted hydrothermal carbonization (MAHC), followed by oxidation and methacrylation. This yielded nano-graphene oxide (nGO) and methacrylated nGO (M-nGO). The structure of the carbon products was confirmed by several spectroscopic techniques. The photo-curing process, mechanical properties, swelling degree, adsorption efficiency towards cationic contaminants and recycling efficiency of the produced hydrogel nanocomposites containing different amounts of nGO or M-nGO were evaluated. Rapid photo-curing was demonstrated for all studied compositions. However, the shielding effect caused by the addition of aromatic nGO increased the time required for reaching gel point (8.5–19.5 s, instead of 4.8 s for pure M-CMC). This was partially compensated by the addition of M-nGO, that could participate in the photo-curing process. The photo-cured nanocomposites, M-CMC/nGO and M-CMC/M-nGO, demonstrated good mechanical properties, extremely high swelling degrees, outstanding adsorption capacity (up to 350 and 145 mg/g for MB and Cu(II) adsorption, respectively) and very good recyclability for at least 3 cycles. The designed “all-lignocellulose” derived hydrogel nanocomposites are, thus, promising candidates for wastewater purification to ensure access to clean water.