Removal of Cd2+ from aqueous solution using hydrothermally modified circulating fluidized bed fly ash resulting from coal gangue power plant

Circulating fluidized bed (CFB) fly ash is an industrial waste produced from the burning of coal gangue by the CFB technology. We investigated the removal of Cd2+ from wastewater by a hydrothermally modified CFB fly ash (HM-CFB-FA) adsorbent material. The SEM and BET analyses of HM-CFB-FA indicated that the adsorbent was rich in porous structure and had a huge specific surface area. Also, the XRF, XRD, and FTIR characterization of the adsorbent material demonstrated that HM-CFB-FA was rich in zeolite content, which indicates that the adsorbent has excellent adsorption capability. The results of the conditional experiments showed that the adsorbent dosage, solution pH, initial Cd2+ concentration, temperature, and the contact time had a remarkable effect on the adsorption performance of HM-CFB-FA. Under the optimal conditions, the maximum adsorption capacity of Cd2+ by HM-CFB-FA reached 183.7 mg/g. The adsorption isotherm analysis revealed that the adsorption of Cd2+ by HM-CFB-FA was well fitted to the Langmuir model. The kinetic investigation showed that Cd(2+)adsorption by HM-CFB-FA was controlled by surface reaction and external diffusion processes. The mechanism analysis demonstrated that the adsorption of HM-CFB-FA and the formation of cadmium hydroxide may be responsible for the removal of Cd2+ from aqueous solution. Therefore, it was concluded that HM-CFB-FA is a promising low-cost adsorbent for the removal of Cd2+ from wastewater. (C) 2017 Elsevier Ltd. All rights reserved.