Functionalization of graphene oxide with cinnamic acid and lignin for enhanced pesticides adsorption for water purification.

Pest control in modern agronomy leads to systematic pesticide usage that influences the water ecosystem and can lead to mutagenic and chronic diseases of diversity, emphasizing the growing demand for the creation of efficient adsorbents with the possibility of regeneration. That's why we herein report the application of the obtained graphene oxide-cinnamic acid and graphene oxide-lignin hybrid systems for water purification from pesticides. For this purpose, biodegradable polymer lignin (by-product of the pulp industry) and its phenolic structural precursor - cinnamic acid have been functionalized with graphene oxide nanolayers for improved adsorption properties. Modification of graphene oxide with lignin and cinnamic acid was performed through covalent functionalization using epichlorohydrin and acyl chloride moieties as crosslinking units, respectively. The structural changes and morphology of the synthesized hybrid nanocomposite systems were investigated by XRD, TEM, FTIR, ssNMR and XPS. BET surface area and pore size analyses were also conducted. Formation of several topologies in the obtained molecules was observed by TEM, whereas XRD determined restructuring of both modifications, likewise the introduction of the guest molecule in the host system. The highest removal efficiencies were achieved at pH 6, and performance remained close to optimal under near-neutral conditions. Regeneration studies showed that the adsorbents retained more than 90% of their initial removal efficiency after three adsorption-desorption cycles. Further, adsorption analyses on the mentioned pesticides were performed by the batch method, which revealed promising results in the case of both hybrid materials, with good performance in the case of the graphene oxide-lignin hybrid system.