Batch and continuous studies on adsorptive removal of hexavalent chromium [Cr(VI)] using reduced graphene oxide

In this study, the reduced form of graphene oxide (RGO) has been synthesized by using hydrazine hydrate as a reducing agent and used for Cr(VI) removal. The physicochemical properties of the as-synthesized material were studied by FESEM, XRD, RAMAN, and FTIR. The optimized adsorption parameters were time of 75 min, solution pH 3.0, temperature 35 degrees C, and dosage of 0.3 g/l. The isotherms were perfectly simulated by the Langmuir model, and the kinetic data followed the pseudo-second-order model. The maximum uptake capacity was 787.401 mg/g at 35 degrees C. Thermodynamic analysis indicated an endothermic and spontaneous process occurs. Competition from interfering ions (SO42-, NO3-, Cl-, HCO3-, Co2+, and Cu2+) proved insignificant. After five cycles of regeneration, the removal remains at 85.75%. From the column study, it was observed that the parameters like breakthrough time (t(b)), bed capacity (q(bed)), and exhaustion time (t(e)) increase with an increase in bed height and decrease with an increase in Cr(VI) flow rate. Adsorption performance for industrial effluents shows up to 55.32% removal. The above superior adsorption performance validated the application of the RGO as an efficient adsorbent for the remediation of Cr(VI) ions from wastewater.