Biomass-based carbon beads with a tailored hierarchical structure and surface chemistry for efficient batch and column uptake of methylene blue

Abstract

There is interest in cultivating an economic and controllable method for preparing biomass-based adsorptive materials for efficient removal of dyes from water. Herein a new bead-like material, i.e. alginate-derived carbon beads with a tailored hierarchical structure and surface chemistry, was prepared by using CaCO3-encapsulated calcium alginate (CA) hydrogel beads as the starting material and subsequent controllable carbonization and oxidation treatment. The resultant samples were characterized by SEM, TEM, FTIR, N2 sorption and XRD, etc. Analyses showed that hierarchical carbon beads with a tailored density of oxygen-containing functional groups have been successfully prepared. Adsorption of methylene blue (MB) was studied systematically through batch and column adsorption analyses, and noting the effect of pH, contact time, initial dye concentrations and flow rates. The adsorption kinetics and isotherms fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively; and the maximum adsorption capacity for MB was 397.9 mg/g. The results indicated that CaCO3/CA-ox could not only significantly improve the adsorption capacity but also exhibited a higher adsorption rate for MB compared with CA. Furthermore, compared to traditional powdery materials, this bead-like porous adsorbent is convenient for column adsorption and scale-up for practical applications, due to the easy regeneration and reusability.