Fabrication and application of hierarchical porous carbon for the adsorption of bulky dyes

Abstract To enhance the removal efficiency of bulky dyes from water and wastewater, a hierarchical porous carbon (HPC) is developed and evaluated as a superior adsorbent in this study. Characterization of the prepared HPC demonstrates that it adopts an interconnected hierarchical porous structure. Macropores with 800–1000 nm diameters interconnect each other via inner windows, and mesopores with an average diameter of 8.1 nm locate in the interwalls of the macropores. The Brunauer-Emmett-Teller (BET) surface area and the pore volume of the HPC reach 1058 m2/g and 2.16 cm3/g, respectively. The adsorption kinetics and isotherms of HPC towards selected dyes are investigated and analyzed by theoretical models. Compared to the commercial activated carbon (AC) and mesoporous carbon (MC), HPC exhibits superior adsorption rate and capacity towards bulky dyes. For the adsorption of all the selected dyes in this study, the intraparticle diffusion rates of HPC keep 2–4 times as high as those of AC and 1.5–2 times as high as those of MC. The interconnected hierarchical porous framework of HPC strongly improves the diffusion rate of guest molecules through the porous network, and consequently accelerates the adsorption rate. A maximum adsorbed amount of 584.32 mg/g of brilliant yellow is achieved by HPC, which is nearly 6 times the capacity of AC. The opened macro/meso porous structure of HPC is assumed to enhance the accessibility of the inner surface to bulky molecules.