title: Immobilization of mercury by carboxymethyl cellulose stabilized iron sulfide nanoparticles: reaction mechanisms and effects of stabilizer and water chemistry.
abstract: Iron sulfide (FeS) nanoparticles were prepared with sodium carboxymethyl cellulose (CMC) as a stabilizer, and tested for enhanced removal of aqueous mercury (Hg(2+)). CMC at ≥0.03 wt % fully stabilized 0.5 g/L of FeS (i.e., CMC-to-FeS molar ratio ≥0.0006). FTIR spectra suggested that CMC molecules were attached to the nanoparticles through bidentate bridging and hydrogen bonding. Increasing the CMC-to-FeS molar ratio from 0 to 0.0006 enhanced mercury sorption capacity by 20%; yet, increasing the ratio from 0.0010 to 0.0025 diminished the sorption by 14%. FTIR and XRD analyses suggested that precipitation (formation of cinnabar and metacinnabar), ion exchange (formation of Hg0.89Fe0.11S), and surface complexation were important mechanisms for mercury removal. A pseudo-second-order kinetic model was able to interpret the sorption kinetics, whereas a dual-mode isotherm model was proposed to simulate the isotherms, which considers precipitation and adsorption. High mercury uptake was observed over the pH range of 6.5-10.5, whereas significant capacity loss was observed at pH < 6. High concentrations of Cl(-) (>106 mg/L) and organic matter (5 mg/L as TOC) modestly inhibited mercury uptake. The immobilized mercury remained stable when preserved for 2.5 years at pH above neutral.
authors.affiliation: Environmental Engineering Program, Department of Civil Engineering, Auburn University , Auburn, Alabama 36849, United States.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Gong
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Liu
authors.forename: Zhong
authors.initials: Z
authors.lastname: Xiong
authors.forename: Dongye
authors.initials: D
authors.lastname: Zhao
mesh_terms: D000327:Adsorption; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008628:Mercury / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D011208:Powders; D017550:Spectroscopy, Fourier Transform Infrared; D013440:Sulfides / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D002712:Chlorides; D006812:Humic Substances; D011208:Powders; D013440:Sulfides; D014867:Water; D007501:Iron; D008628:Mercury; D002266:Carboxymethylcellulose Sodium