Abstract:

Fly ash, a kind of industrial solid waste material produced during the combustion of coal in the electricity generation, was utilized to prepare a novel carbon/fly ash composite adsorbent with core-shell structures by a partial carbonization and sulfonation process. The prepared composite adsorbent was characterized with XPS, FT-IR, SEM, XRD and gas adsorption experiments. The results showed that fly ash was coated by graphite-like carbon nanoparticles. The carbon, oxygen, silica and sulfur are the main elements on the surface of the prepared composite adsorbent. Among them, the carbon and oxygen elements are the dominant superficial elements. An abundant of mesopores existed on the surface of the composite adsorbent. The Brunauer Emmett Teller(BET) surface area SBET is 5.4 m2/g. Meanwhile, an abundant of oxygen functional groups, such as carboxyl, hydroxyl and sulfonic groups, which were very effective in capturing cationic organic dyes and heavy metal ions and acted as the main adsorption sites of the composite adsorbent, were successfully introduced on the composite adsorbent surface. The adsorption capacity of the prepared composite for typical cationic dye methylene blue and heavy metal ions was also investigated and compared with activated carbon and fly ash under the same experimental condition. The results show that the composite adsorbent exhibits excellent adsorption performance. The adsorption capacity for methylene blue can reach about 83.7% of activated carbon adsorption capacity, and the adsorption capacity for heavy metal ions Cd2+, Ni2+, Pb2+ and Cu2+ can reach about 104.3%, 131.1%, 170.5% and 127.3% of the capacity of activated carbon, respectively. The adsorption capacity for methylene blue and heavy metal ions is far more than that of fly ash. The prepared carbon/fly ash composite adsorbent can be used as a potential substitute of activated carbon for heavy metal ions or organic dyes adsorption in waste water.

Key words: fly ash, carbon, composite adsorbent, sucrose, adsorption