Green synthesis of graphene oxide–citric acid (GOCC) nanocomposite for Cd (II) and Pb (II) adsorption: adsorption studies and BBD-RSM modelling

Aquatic water systems that are contaminated with heavy metals have negative consequences. The environment was at risk because of these effects. Citric acid was used in this study as a renewable crosslinking agent between graphene oxide (GO) and cellulose to create a GOCC composite. The produced substance was tested as a successful adsorbent for extracting Cd and Pb ions from aqueous solutions.FTIR infra-red, SEM/EDS spectroscopy, XRD, and ICP plasma mass spectrometry were used to evaluate the surface/structural features. Adsorption investigations were carried out using a variety of experimental parameters, such as pH, contact time, and adsorbent mass. About 99% of Pb2+ and 98% of Cd2+ were removed under conditions that included 25°C, pH 6, 0.1 g of adsorbent mass, and concentrations of [Cd2+/Pb2+]i = 20 mg.L−1 at = 60 min. With R2 = 0.999, the pseudo second order was established by the adsorption kinetics, suggesting a chemisorption mechanism. The exothermic nature of adsorption was corroborated by thermodynamic parameters (ΔH = −129 and −71.13 kJ·mol−1) over the temperature range of 25–45 °C. In parallel, at equilibrium, data followed the Langmuir (monolayer) isotherm.Response surface methodology optimisation based on a Box–Behnken design (RSM-BBD) revealed the robustness of the GOCC composite and its high efficiency for Pb2+/Cd2+ removal.