Polyaniline/basic oxygen furnace slag nanocomposite as a viable adsorbent for the sorption of fluoride from aqueous medium: equilibrium, thermodynamic and kinetic study

摘要

The objective of the present research was to synthesize and characterize polyaniline/BOF slag nanocomposite and to evaluate its fluoride removal efficiency. The surface structure of the nanocomposite was investigated by means of XRD, TGA/DSC, SEM, and BET surface area analysis. In addition, adsorption mechanisms were investigated by conducting batch and making a comparative XRD analysis of fresh and exhausted nanocomposite. SEM micrographs were obtained to study the morphology of the nanocomposite. Batch experiments were performed to investigate effects of various experimental parameters such as contact time, initial fluoride concentration, temperature, pH, and the presence of competing anions. The adsorption data better fitted Langmuir adsorption isotherm. The maximum adsorption capacity calculated from Langmuir isotherm model was up to 9.143 mg/g (at 45 degrees C). Thermodynamic study indicated an endothermic nature of adsorption and a spontaneous and favorable process. The optimum pH for fluoride removal was between 6 and 10. The fluoride adsorption was impeded by the presence of phosphate, followed by bicarbonate, carbonate, sulfate, chloride, and nitrate. The fluoride removal was probably due to chemisorption, precipitation, and surface chemical reaction with CaO present in the basic oxygen furnace slag and through the replacement of doped ionizable chloride ions present in polyaniline.