Efficient removal of water pollutants by hierarchical porous zeolite-activated carbon prepared from coal gangue and bamboo

The inorganic heavy metal ions (IHMIs) and organic macromolecular pollutants (OMPs) are the two most common pollutants in industrial, agricultural and municipal wastewater. They have greatly threatened the environmental security and human health because of their most notorious toxicity and carcinogenicity. In this study, a composite of zeolite-activated carbon is synthesized taking coal gangue as silicon and aluminum sources and adding bamboo as carbon source through a facile calcining process following a hydrothermal process. The obtained zeolite-activated carbon composite is a kind of hierarchical porous structure, which contains a large number of micro-pores, meso-pores and macro-pores simultaneously. The zeolite-activated carbon with high specific surface area of 879.1 m²/g is used to absorb IHMIs and OMPs. It shows high adsorption capacities for copper ions (Cu²⁺, 104.9 mg/g) and Rhodamine-B (Rh–B, 83.34 mg/g). The zeolite with a large number of micro-pores could chain a lot of IHMIs with small diameters, and the activated carbon could allow large size OMPs into its meso-pores and macro-pores. The thermodynamic and kinetic studies indicate that the adsorption of adsorbates onto the zeolite-activated carbon composite is assigned to a monolayer, spontaneous and physical adsorption. Thus the zeolite-activated carbon composite could adsorb the pollutants quickly and desorb them repeatedly. This research not only effectively deals with the IHMIs and OMPs in the waterbody, but also converts the coal gangue into high value-added product. Therefore, this study provides a facile method to synthesize zeolite-activated carbon composite from solid waste and biomass material. The prepared zeolite-activated carbon composite could be selected as a potential candidate for sewage treatment.