title: Effects of pH and ionic composition on sorption/desorption of natural organic matter on zero-valent iron and magnetite nanoparticles.
abstract: Understanding the interactions between natural organic matter (NOM) and zero-valent iron nanoparticles (nano-Fe0) and magnetite nanoparticles (nano-Fe3O4) is essential for evaluating their performance in pollutant remediation, as well as determining their fate and transport in the environment. Batch experiments were performed to investigate the sorption/desorption behaviors of humic acid (HA) on commercially available nano-Fe0 and nano-Fe3O4. The sorption/desorption of HA on nano-Fe0 and nano-Fe3O4 were well described by both the Langmuir model and the modified Langmuir model. The adsorption capacities of HA were 8.77±0.31 mg C/g and 10.05±0.95 mg C/g for nano-Fe0 and nano-Fe3O4, respectively. The interactions of HA with nano-Fe0 and nano-Fe3O4 were highly pH-dependent. On one hand, nano-Fe0 had its maximum adsorption of 11.0 mg C/g HA at pH=3, which decreased to 0.6 mg C/g when pH increased to 11.9; on the other hand, alkaline condition enhanced HA desorption greatly. At pH=10.1, after 24 h desorption experiments, nearly 80% of initially adsorbed HA desorbed from the nanoparticles. The interactions of HA with nano-Fe0 and nano-Fe3O4 were also influenced by different ion compositions in solution. Divalent cations (e.g. Ca2+, Mg2+) enhanced HA adsorption significantly, while phosphate nearly eliminated HA adsorption and promoted significantly HA desorption.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China E-mail: chenjiawei@cugb.edu.cn; Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing 100083, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Fan
authors.affiliation: Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing 100083, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77204-4003, USA.
authors.forename: Yandi
authors.initials: Y
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China E-mail: chenjiawei@cugb.edu.cn.
authors.forename: Jiawei
authors.initials: J
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D009994:Osmolar Concentration
chemical_list: D006812:Humic Substances; D058185:Magnetite Nanoparticles; D007501:Iron