▎ 摘　　要

A facile approach to synthesize reduced graphene oxide (rGO) was investigated using three different extract concentrations of Tecoma stans leaves as reducing/capping agents. The surface morphology of the rGOs was examined by scanning electron microscopy with energy dispersive X-ray. The optimum prepared rGOs were confirmed with characteristic peaks at similar to 280 nm using UV-Vis Spectroscopy. Fourier-transform infrared spectroscopy results indicated the capacity of plant extracts to reduce the oxygen functional groups on graphite oxides' surfaces. Furthermore, the organic constituents of the plant extract were determined to highlight the reduction mechanism of graphene oxide to rGO. The optimized rGO was subsequently utilized as an adsorbent for the removal of Ni (II) from simulated wastewater. Adsorption experiments were conducted using methods of one factor at a time as well as Box Behnken Design. The Ni (II) adsorption is fitted well to the non-linear isotherm models and the calculated maximum uptake capacity was 69 mg g(-1) . The optimum removal of Ni (II) was found 93% with pH of 6, initial Ni (II) concentration of 2 mg L-1, and rGO dose of 0.2 g L-1. The reliability of the developed model was 99.4% between experimental and predicted values. In addition, the average desorption efficiency of Ni (II) was 94%, which highlight the applicability of rGO reusability.