Efficient fluoride removal by preparation, characterization of pyrolysis bone: Mixed level design experiment and Taguchi L8 orthogonal array optimization

Mixed level design experiment and Taguchi orthogonal array design L8 (4<^>1, 2<^>2) was applied to optimize pyrolysis process for preparing bone char in order to remove fluoride from real groundwater. Taguchi analysis is through selecting high signal-to-noise ratio as a better response. Estimated effects index based on the least squares approach indicated that the pyrolysis temperature had a main effect on bone char preparation using pyrolysis process. The bone char obtained at pyrolysis temperature = 550 C had the highest adsorption capacity with maximum saturation experimental adsorption capacity of 12.05 mg/g. Specific surface area and Barrett-Joyner-Halenda area of the bone char obtained from pyrolysis of animal bones were 118 m(2)/g and 120 m(2)/g, respectively. The experimental adsorption results were better fitted to the Langmuir isotherm and the pseudo second-order kinetic model. Thermodynamic information indicated that fluoride adsorption process onto pyrolysis bone char followed spontaneously (Delta G&DEG: = -4.9724.296 kJ/mol), an endothermic (Delta H&DEG: = 5.59 kJ/mol) and nature randomness (Delta S&DEG: = 0.033 kJ/mol.K). Accordingly, the bone char obtained using pyrolysis process under optimum conditions demonstrated higher adsorption capacity compared to commercial bone chars applied for fluoride removal from groundwater. (C) 2018 Elsevier B.V. All rights reserved.