Gum Arabic tree biomass derived activated carbon for fluoride sequestration in batch and fixed bed processes: kinetics, thermodynamics and column adsorption modeling

Abstract

The biomass obtained from the stem of Gum Arabic tree was used to prepare a thermally activated carbon through pyrolysis at 800 °C. The activated carbon tagged GAAC-800 was used as adsorbent for the fluoride sequestration in a batch and a fixed-bed reactor in a 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. Also, 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 from the fixed bed adsorption data were well modeled by Adams-Bohart, Yoon-Nelson and Clark model. The models were judged using Akaike Information Criteria (AIC) values after statistical evaluation. GAAC-800 removed fluoride from aqueous solution comparably higher than other adsorbent in its category in batch and continuous column systems.