Evaluation of fluoride and cadmium adsorption modification of corn stalk by aluminum trichloride

Abstract The aluminum-modified corn stalk biochar (AlCl3-BC) were prepared to adsorb fluoride from single ion solution and from binary mixtures with cadmium. FTIR spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and zeta potentiometry revealed that surface functional groups, crystal and physical structure of biochar were significantly improved by AlCl3 modification. The fluoride adsorption process consisted with pseudo-first order kinetics model and both Langmuir and Freundlich models well. The AlCl3-BC exhibited greater adsorption capacities than the original biochar (BC) with adsorption capacity of 81.65 mg g−1 at 35 °C. Both BC and AlCl3-BC showed higher capacities than those reported for other biochar. The fluoride adsorption capacity Qe from a binary solution of fluoride and cadmium gradually decreased as the initial cadmium concentration increased at fixed initial fluoride concentrations, while adsorption of cadmium increased. As the initial fluoride concentrations increased from 5 to 20 mg L−1, the Qe of fluoride increased as the Qe of cadmium decreased, indicating that fluoride adsorption by BC and AlCl3-BC was clearly reduced in the presence of cadmium. This research suggested that AlCl3-BC is a promising candidate material for single ion fluoride removal and could also achieve synergetic removal of fluoride and cadmium from contaminated water bodies.