Highly Efficient Adsorption of Bulky Dye Molecules in Wastewater on Ordered Mesoporous Carbons

Abstract

We demonstrate, for the first time, the application of ordered mesoporous carbons with large pore sizes prepared from the surfactant-templating approach in efficient disposal of wastewater containing bulky dye molecules. The adsorption amount for the bulky dye (methylthionine chloride, fuchsin basic, rhodamine B, brilliant yellow, methyl orange, or Sudan G) is almost twice that of the activated carbon in which mesopores contribute almost 100% to the total surface area and volume. The ordered mesoporous carbon adsorbent has a high adsorption rate (>99.9%) for low-concentration dyes, good performance in decoloration regardless of the dye nature, including basic, acidic, or azo dyes, and high stability after dye elution. To establish the relationship between the pore texture and adsorption properties, three kinds of ordered mesoporous carbons with different pore sizes, surface areas, and pore volumes have been synthesized by using phenolic resins as carbon sources and triblock copolymer as a structure-directing agent. The XRD, TEM, and N 2 sorption measurements reveal that all mesoporous carbonaceous materials have the highly ordered 2D hexagonal mesostructure, high surface areas (398−2580 m 2 /g), large pore volumes (0.51−2.16 cm 3 /g), and uniform pore sizes ranging from 4.5 to 6.4 nm. The adsorption capacities are compared and the pore occupation is estimated to understand the adsorption behaviors in the ordered mesopores with different diameters and models. The spatial effect of dye molecules is the determinative factor for the adsorption in ordered mesoporous carbons with various pore textural properties. The mesoporous carbon with an extremely high surface area (2580 m 2 /g), a large pore volume (2.16 cm 3 /g), and bimodal pores (6.4 and 1.7 nm) prepared from the silica−carbon composite shows the highest adsorption capacities for bulky basic dyes among the three ordered mesoporous carbons.