Efficient removal of malachite green from wastewater by using boron-doped mesoporous carbon nitride

In this study the adsorption performance of boron doped mesoporous carbon nitride (BMCN) was studied for the elimination of malachite green (MG) dye from wastewater. BMCN with various weight ratios of boron doping was prepared in two steps including using a hard template to synthesize MCN, and then addition of boric acid as the boron source to produce BMCN. 1 wt% boron doping displayed the highest removal efficiency and adsorption capacity. The new adsorbent was analyzed using XRD, N-2 adsorption-desorption, TEM, SEM-EDX and its elemental mapping, and FT-IR. Four critical parameters optimized by response surface methodology (RSM) method were temperature, initial dye concentration, pH and sorbent weight for MG adsorption. The maximum removal (100%) predicted from RSM was reported for 18 mg of the sorbent at pH 5 and MG concentration of 20 mg L-1 at room temperature. The boron doped mesoporous carbon nitride showed a high maximum adsorption capacity about 310 mg g(-1) and reached at the equilibrium within 30 min followed the pseudo-second-order kinetic model with 99.8% MG removal while the rate-limiting step is the intraparticle diffusion stage. The adsorption phenomena matched well to the heterojunction surface Freundlich, Koble-Corrigan, and Sips isotherm models. The BMCN1 showed excellent reusability and was applied for six cycles of regeneration effectively, while its removal efficiency remained at a high value.