Modelling the batch and fixed bed adsorption of fluoride from aqueous solutions in using activated carbon from Acacia nilotica biochar

Abstract

Acacia nilotica biomass was used to prepare activated carbon (ANAC-800) through pyrolysis at 800oC. The ANAC-800 was used as adsorbent for the fluoride sequestration in a batch and continuous column systems. The surface morphology, elemental composition as well as particle size distribution of the adsorbent was investigated with Scanning Electron Microscopy (SEM), Elemental and Particle Size Analyzers. What’s more, the influence of initial fluoride concentrations, column packing height and the flow rate on the column efficiency were examine while the efficiency of batch process as a function of contact time and temperature was also investigated. It was found that the kinetic of the process was best fitted with second order model, while the mechanism was best explained by interparticle diffusion model. In addition, the Langmuir Isotherm model showed that the maximum monolayer adsorption capacity of fluoride removal was 71.93 mg/g. The breakthrough curve and column data were well modelled by Adams-Bohart, Yoon-Nelson and Clark model. The models were judged using Akaike Information Criteria (AIC) values after statistical evaluation. ANAC-800 removed fluoride from aqueous solution comparably higher than other adsorbent in its category in batch and continuous column systems.