Synthesis, characterization, and breakthrough modeling of low-cost graphene oxide-sand supported adsorbent filter for the separation of lead and chromium ions

The existence of lead and chromium ions in waterbodies severely affects the biological activities of aquatic creatures that directly affect human health. A graphene oxide-sand (GO-sand)-based composite filter has been successfully used as a Rapid Sand Filter (RSF) to remove Lead (II) and Chromium (III) ions in water. Boehm titration, FTIR, RAMAN, XRD, and SEM-EDX analyses confirmed GO-sand's active sites, semicrystalline, and irregular morphology. Moreover, lead and chromium adsorption using a GO-sand composite was established by XPS and SEM-EDX analyses. The results of the batch study showed significant adsorption (289.68 mg g(-1 )and 258.87 mg g(-1)) along with significant removal (96.4 % and 95.6 %) of Pb (II) and Cr (III), respectively. Among Langmuir, Freundlich, and Liu isotherms, the adsorption isotherm showed an excellent fit with Liu isotherm. The response surface methodology (RSM) study suggested adequate quadratic models and exceptional covenant between the predicted and actual figures with a significant coefficient determination (R-2 > 0.920). The kinetic study finding revealed the best fit for the Elovich kinetic model (R-2 = 0.995 (Pb), R-2 = 0.967 (Cr)), and the thermodynamics study confirmed endothermic adsorption. Pareto analysis confirmed that solution pH was the most significant parameter towards adsorption. Furthermore, the regenerated adsorbent demonstrated practical reusability up to four adsorption-desorption cycles, revealing the process's sustainability.