Hydrodynamics and adsorption performance of liquid–solid fluidized bed with granular activated carbon for removal of copper ions from wastewater

The removal of copper ions from wastewater is of great significance for reducing pollution of surrounding environments and ensuring the quality of drinking water. In this study, a liquid–solid fluidized bed with nutshell activated carbon was used to adsorb copper ions from wastewater. The fluidization characteristics and adsorption performance of the liquid–solid fluidized bed were investigated through batch, cyclic, and continuous adsorption experiments. The results showed that nutshell activated carbon had a strong adsorption capacity for copper ions in wastewater by the electrostatic adsorption function of its oxygen-containing groups, and the adsorption isotherm was fitted by the Langmuir isotherm model (R2 reached 0.98), which indicated a positive single-layer adsorption. The pseudo-second-order model described the adsorption process well, and the adsorption process was controlled by a continuous migration step with internal and external diffusion. The high-frequency contact between adsorbent and adsorbate in the fluidized bed layer increased its external diffusion rate, thereby promoting improved adsorption efficiency of 96% compared with 76% of the packed bed. The weight of the particle bed was the factor influencing adsorption performance the most, followed by fluidization number, and then initial concentration, indicating that the fluidization characteristics determined the adsorption efficiency. The breakthrough curve showed that the adsorption saturations of the fluidized and packed bed were 0.694 and 0.660 g/g, respectively, which demonstrated the superiority of the fluidized bed in the adsorption process.