Hierarchically porous silicon–carbon–nitrogen hybrid materials towards highly efficient and selective adsorption of organic dyes

Abstract

The hierarchically macro/micro-porous silicon–carbon–nitrogen (Si–C–N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp2-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg·g−1 and 1084.5 mg·g−1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si–C–N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants.

Malachite green “a cationic dye” and its removal from aqueous solution by adsorption

“…The adsorption of MG by HNTs obeyed pseudo-secondorder kinetics with activation energy 18.28 kJ/mol, 49. Hierarchically macro/microporous silicon-carbonnitrogen (Si-C-N) hybrid material ------- (Meng et al 2015) suggested that the process was physisorption. The best-fit adsorption isotherm was achieved with the Langmuir model, indicating that homogeneous adsorption occurred.…”

Fast removal of methylene blue from aqueous solution using coal-based activated carbon

“…The Langmuir isotherm model is based on the assumption that the adsorption process is a monolayer adsorption on a homogeneous adsorbent surface, there is no interaction between adsorbed molecules and the binding sites are nite and have the identical sorption energies. 40 The equation of Langmuir isotherm could be expressed as follows.…”

Super-adsorbent material based on functional polymer particles with a multilevel porous structure

“…Meanwhile, the presence of macropores and interconnected mesopores enables the fast diffusion of molecules into the internal pores (especially for large molecules), which greatly improves the adsorption rate. [33][34][35] However, the tedious preparation procedures for the hierarchically porous adsorbents greatly hinder their practical applications. Furthermore, there are still some inaccessible binding sites in such materials, leading to binding efficiencies far below 100% (relative to the molar amount of the functional groups).…”