Microwave Assisted Synthesis of High Surface Area Nanoporous Materials for Adsorptive Removal of Organic Dyes

Abstract

A series of nanoporous polymeric adsorbents has been synthesized using phenanthrene and dibenzothiophene as precursors, by varying chemical composition of precursors. All the polymeric adsorbents have been synthesized using a quick and facile microwave assisted method within a short duration of 60 min. High surface area microporous polymeric adsorbents were obtained with specific surface area (SABET) in the range of 269-1207 m2 g-1. Maximum specific surface area of 1207 m2 g-1 with controlled pore size distribution (1.18 and 1.78 nm) and pore volume (0.55 cm3 g-1) has been estimated for one of the polymeric adsorbents (poly-PD-1.5) synthesized using equimolar ratio (1:1) of phenanthrene and dibenzothiophene. All the synthesized polymeric adsorbents have been explored for adsorptive removal of both anionic (alizarin red S, ARS) and cationic (crystal violet, CV) dyes from aqueous solution. It is observed that poly-PD-1.5 showed better performance for adsorptive removal of both alizarin red S and crystal violet. The adsorption process was studied by varying choice of adsorbent, adsorbent dosage, contact time, dye concentration and temperature for poly-PD-1.5. Adsorption capacity for ARS and CV reaches up to of 55.67 and 77.05 mg g-1, respectively when the initial dye concentration was of 50 ppm for 120 min at RT with 8 mg and 6 mg of adsorbent, respectively. Textural properties along with π-π stacking plays a major role in the adsorption process. Both dyes follow pseudo 2nd order kinetics. ARS and CV dye adsorption is spontaneous; △H for ARS was 55.17 KJ mol-1 and for CV it was -21.91 KJ mol-1 which indicates that ARS dye adsorption was endothermic process and CV dye adsorption was exothermic process.