title: Polypyrrole-grafted peanut shell biological carbon as a potential sorbent for fluoride removal: Sorption capability and mechanism.
abstract: In this study, an effective defluoridation adsorbent was developed by depositing polypyrrole (PPy) on granular peanut shell biological carbon (BC) via in situ chemical oxidative polymerization. The variables of defluoridation process (i.e., adsorbent dosage, fluoride solution pH, and anionic interference) were tested. The mechanism was determined by isotherm and kinetic studies, Brunauer-Emmett-Teller (BET) method, scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and automatic titration. The PPy-grafted BC (PPy/BC) composite performed commendably from pH 2.0 to 10.0, and exhibited high selectivity for fluoride in the presence of several co-existing anions. The experimental data were described well by a Langmuir isotherm curve, and the maximum adsorption capacity was 17.15 mg g(-1). Kinetic studies illustrated the adsorption process was accomplished via surface adsorption as well as by intraparticle diffusion. In addition, mesoporous diffusion was the rate-controlling step in intraparticle diffusion process. BET and SEM analysis revealed the sponge-like polymer adhered to the BC and plugged the pores. XPS, FTIR, and SEM confirmed that fluoride removal was accomplished via the replacement of doped ionizable chloride ions (Cl(-)) coupled with positively charged nitrogen (N(+)), computation of XPS data enabled the formulation of a three-layer-deep hypothesis for PPy.
authors: School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China.
authors: Chunlu
authors: C
authors: Li
authors: School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China; Key Laboratory of Groundwater Cycle and Environment Evolution (China University of Geosciences (Beijing)), Ministry of Education, Beijing, 100083, China. Electronic address: chennan@cugb.edu.cn.
authors: Nan
authors: N
authors: Chen
authors: School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China.
authors: Yanan
authors: Y
authors: Zhao
authors: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors: Rui
authors: R
authors: Li
authors: School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China; Key Laboratory of Groundwater Cycle and Environment Evolution (China University of Geosciences (Beijing)), Ministry of Education, Beijing, 100083, China.
authors: Chuanping
authors: C
authors: Feng
mesh_terms: D000327:Adsorption; D010367:Arachis / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D004058:Diffusion; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005459:Fluorides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D011108:Polymers / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D010710:Phosphates; D011108:Polymers; D011758:Pyrroles; D014874:Water Pollutants, Chemical; C012980:fluorophosphate; C067635:polypyrrole; D002244:Carbon; D005459:Fluorides
keywords: Active N(+); Adsorption; Biological carbon (BC); Defluoridation; Polypyrrole (PPy)