title: Removal of humic acid from aqueous solution by magnetically separable polyaniline: adsorption behavior and mechanism.
abstract: Magnetically separable polyaniline (Fe3O4@SiO2-PANI) was prepared by in situ chemical polymerization of aniline on the surface of silica-coated Fe3O4 nanoparticles, and characterized by FTIR spectroscopy, powder X-ray diffraction, elemental analysis, transmission electron microscopy, vibrating sample magnetometry and X-ray photoelectron spectroscopy. Characterization results showed that Fe3O4@SiO2-PANI with amino groups of 1.78 mmol/g and the average diameter of 21.6 nm are superparamagnetic. Adsorption behavior of Fe3O4@SiO2-PANI nanoparticles for humic acid (HA) was investigated by batch experiments and adsorption kinetic tests. HA adsorption amount on the adsorbent decreased with increasing solution pH and the presence of Ca(2+) resulted in the enhanced HA adsorption. HA adsorption on Fe3O4@SiO2-PANI could be well described by Langmuir model and the maximum adsorption amount of the adsorbent for HA at 25°C was 36.36 mg/g. HA adsorption process on the adsorbent obey pseudo-second-order kinetics and the adsorption rates decrease with increasing initial HA concentration. The XPS analysis verified that HA adsorption over the adsorbent could be attributed to the surface complexation between the disassociated HA molecules and the protonated nitrogen of polyaniline on the adsorbent. HA loaded adsorbent could be magnetically separated and easily desorbed in 0.01 mol/L NaOH solution. Regeneration tests indicated that Fe3O4@SiO2-PANI could be used repeatedly.
authors.affiliation: College of Resource and Environment, Shaanxi University of Science & Technology, Xi'an 710021, PR China; School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: wangjiahong@sust.edu.cn.
authors.forename: Jiahong
authors.initials: J
authors.lastname: Wang
authors.affiliation: College of Resource and Environment, Shaanxi University of Science & Technology, Xi'an 710021, PR China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Bi
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, and School of the Environment, Nanjing University, Nanjing 210093, PR China.
authors.forename: Yanfen
authors.initials: Y
authors.lastname: Ji
authors.affiliation: College of Resource and Environment, Shaanxi University of Science & Technology, Xi'an 710021, PR China.
authors.forename: Hongrui
authors.initials: H
authors.lastname: Ma
authors.affiliation: College of Resource and Environment, Shaanxi University of Science & Technology, Xi'an 710021, PR China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Yin
mesh_terms: D000327:Adsorption; D000814:Aniline Compounds / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D006812:Humic Substances; D060526:Magnetic Fields; D008956:Models, Chemical; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D005290:Ferric Compounds; D006812:Humic Substances; C416807:polyaniline; C000499:ferric oxide; D012822:Silicon Dioxide; D002118:Calcium
keywords: Adsorption; Humic acid; Magnetic separation; Magnetically separable polyaniline