title: Highly efficient fluoride adsorption from aqueous solution by nepheline prepared from kaolinite through alkali-hydrothermal process.
abstract: A direct alkali-hydrothermal induced transformation process was adopted to prepare nepheline from raw kaolinite (shortened form RK in this paper) and NaOH solution in this paper. Structure and morphology characterizations of the synthetic product showed that the nepheline possessed high degree of crystallinity and uniform surface morphology. Specific surface area of nepheline is 18 m2/g, with a point of zero charge at around pH 5.0-5.5. The fluoride (F-ions) adsorption by the synthetic nepheline (shortened form SN in this paper) from aqueous solution was also investigated under different experimental conditions. The adsorption process well matched the Langmuir isotherm model with an amazing maximum adsorption capacity of 183 mg/g at 323 K. The thermodynamic parameters (ΔG0, ΔH0, and ΔS0) for adsorption on SN were also determined from the temperature dependence. The adsorption capacities of fluoride on SN increased with increasing of temperature and initial concentration. Initial pH value also had influence on adsorption process. Adsorption of fluoride was rapidly increased in 5-60 min and thereafter increased slowly to reach the equilibrium in about 90-180 min under all conditions. The adsorption followed a pseudo-second order rate law.
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, PR China; The School of Earth Science and Resources, Chang'an University, Xi'an 710064, PR China.
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, PR China; Key Laboratory for Mineral Materials and Application of Hunan Province, Central South University, Changsha 410083, PR China.
authors.forename: Qiming
authors.initials: Q
authors.lastname: Feng
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, PR China; Key Laboratory for Mineral Materials and Application of Hunan Province, Central South University, Changsha 410083, PR China. Electronic address: kliu@csu.edu.cn.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, PR China; Key Laboratory for Mineral Materials and Application of Hunan Province, Central South University, Changsha 410083, PR China.
authors.forename: Zishun
authors.initials: Z
authors.lastname: Li
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, PR China; Key Laboratory for Mineral Materials and Application of Hunan Province, Central South University, Changsha 410083, PR China.
authors.forename: Xuekun
authors.initials: X
authors.lastname: Tang
authors.affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, PR China.
authors.forename: Guangze
authors.initials: G
authors.lastname: Li
mesh_terms: D000327:Adsorption; D000468:Alkalies; D017607:Aluminum Compounds; D005459:Fluorides; D006863:Hydrogen-Ion Concentration; D007616:Kaolin; D007700:Kinetics; D017640:Silicates; D017670:Sodium Compounds; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics; D014874:Water Pollutants, Chemical; D018508:Water Purification
chemical_list: D000468:Alkalies; D017607:Aluminum Compounds; D017640:Silicates; D017670:Sodium Compounds; D012996:Solutions; D014874:Water Pollutants, Chemical; C024205:nepheline; D007616:Kaolin; D005459:Fluorides
keywords: Adsorption; Fluoride; Hydrothermal synthesis; Kaolinite; Nepheline