Persimmon tannin-modified graphitic carbon nitride as a bioadsorbent for methyl orange removal through CCD-RSM design

Graphitic carbon nitride (g-C 3 N 4 ) and persimmon tannin (PT) were used to prepare a novel bioadsorbent, which applying for the adsorption of methyl orange (MO) from aqueous solution. The preparation of persimmon tannin/graphitic carbon nitride (PT/g-C 3 N 4 ) as a polymer was confirmed by several techniques including Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), X-ray powder diffraction, and Brunauer–Emmett–Teller analysis. Several factors were influenced on the MO adsorption such as pH, MO concentration, bioadsorbent amount, time, and temperature. These parameters were studied by response surface methodology (RSM) method with Design-Expert software, and the results were shown good agreement between experimental and selected model data. Through CCD-RSM design, the interaction of effective parameters was determined by quadratic model, and the optimum conditions were obtained. According to data, the Freundlich isotherm was selected as a suitable isotherm for the mechanism description. Further, the results were agreed to the pseudo-second-order model to explain the MO adsorption on PT/g-C 3 N 4 . Based on the data, PT/g-C 3 N 4 polymer can be used as a good bioadsorbent after four times, which providing high efficiency for the pollutant removal compared to that of g-C 3 N 4 .