Composite hydrogel based on chemically modified gelatin and PVA containing graphene oxide nanoparticles (CHGP-GOn)

Abstract

The increased consumption of medications such as Chloroquine (CQN) during the Covid-19 pandemic, the excretion of this drug leading to an overload of CQN and its metabolites in sewage treatment plants, increased the necessity to adequate treatment for their removal. Water treatment using advanced processes can be enhanced through the utilization of adsorbent and absorbent materials, facilitating the removal of hard-to-treat compounds and enabling material reusability. The use of nanoparticles offers desirable attributes responsible for the adsorption process, maximising the feature of water treatment materials. In this context, graphene oxide exhibits high surface area and significant adsorption capacity due to its abundance of desirable functional groups for adsorbing contaminant molecules. However, the lixiviation from these materials represents an environmental problem. The functionalization of adsorbent materials with nanoparticles has been used to minimise the loss of nano-compounds. In this way, composite hydrogels synthesized with graphene oxide have demonstrated adsorption and absorption properties for emerging contaminants, including pharmaceuticals. Therefore, a composite hydrogel based on chemically modified gelatin and PVA containing graphene nanoparticles, with resistant reticulation and non-toxic compounds, synthesized for the first time, was employed for the removal of CQN from aqueous media. This hydrogel superabsorbent with morphological rough shows 175% capacity of swelling, positive tendency of charge on natural pH due to diverse functional groups, as well as point of zero charges at pH 9.1, amorphous features. The batch removal tests demonstrated a superabsorbent material (175% swelling), showing the best removal in Qe of 13.20 mg g −1 of Chloroquine, as well as a superior performance at natural pH. The adsorption kinetics were best described by the Elovich model, indicating multi-step resistance with intraparticle diffusion as the rate-limiting step, equilibrium in 240 min and a maximum adsorption capacity of 13.31 mg g−1. Furthermore, the isotherm exhibited spontaneous and exothermic adsorption, with low reversibility and randomness in the adsorption system. Besides, the maximum experimental adsorption capacity was 52.98 mg L-1 in 288 K. The material demonstrated promising reusability, retaining its adsorption capacity over three adsorption cycles and values of 14.26 followed by 4.830 and 2.280 mg g- 1, respectively. In conclusion, the composite hydrogel based on graphene oxide shows great potential as an efficient and eco-friendly approach for removing emerging contaminants, particularly pharmaceuticals like CQN, from aqueous environments.