A novel one-step method for preparation of sulfonate functionalized nanodiamonds and their utilization for ultrafast removal of organic dyes with high efficiency: kinetic and isotherm studies

Abstract In this work, a novel one-step method based on the aryl diazonium chemistry has been developed for the first time to synthesize benzenesulfonic-modified NDs (NDs-SO3H), which were used to remove methylene blue (MB) in dyestuff sewage. The particle morphology, structure, physicochemical characters of NDs and NDs-SO3H were examined through SEM, TEM, XPS, TGA and FT-IR. To further explore the adsorption application, the adsorption behavior of NDs and NDs-SO3H at different temperature, initial solution concentration, contact time and initial pH has been studied. The experimental data show that MB can be rapidly adsorbed by adsorbents within 3 min and reach the equilibrium in 15 min. The adsorption capacity of NDs-SO3H could reach to 385.27 mg/g with initial concentration was 250 mg/L, which is obvious above the adsorption capacity of pristine NDs. To evaluate the fitness of the isotherm equations, average relative error (ARE) was used. The adsorption kinetic data confirm that the adsorbent process was chemisorption process, which was followed the pseudo-second-order model. MB removal by NDs-SO3H followed Freundlich model with the process was multilayer adsorption process occurred on the heterogeneous surface. According to thermodynamic parameters, adsorption is a spontaneous, exothermic process of reduced entropy. Also, the prepared NDs-SO3H show excellent adsorption performance at different initial solution pH, indicating NDs-SO3H adapted to wide pH range. The surface modification of NDs was conducted by diazonium grafting technology and the NDs-SO3H was found to be promising adsorbents for removal of MB. Also, the unique modification method can be widely used in environmental engineering.