title: Effect of anions and humic acid on the performance of nanoscale zero-valent iron particles coated with polyacrylic acid.
abstract: Effects of anions (NO3(-), HCO3(-), Cl(-), SO4(2-)) and humic acid on the reactivity and core/shell chemistries of polyacrylic acid-coated nanoscale zero-valent iron (PAA-NZVI) and inorganically modified NZVI (INORG-NZVI) particles were investigated. The reactivity tests under various ion concentrations (0.2-30mN) revealed the existence of a favorable molar ratio of anion/NZVI that increased the reactivity of NZVI particles. The presence of a relatively small amount of humic acid (0.5mgL(-1)) substantially decreased the INORG-NZVI reactivity by 76%, whereas the reactivity of PAA-NZVI decreased only by 12%. The XRD and TEM results supported the role of the PAA coating of PAA-NZVI in impeding the oxidation of the Fe(0) core by groundwater solutes. This protective role provided by the organic coating also resulted in a 2.3-fold increase in the trichloroethylene (TCE) reduction capacity of PAA-NZVI compared to that of INORG-NZVI in the presence of anions/humic acid. Ethylene and ethane were simultaneously produced as the major reduction products of TCE in both NZVI systems, suggesting that a hydrodechlorination occurred without the aid of metallic catalysts. The PAA coating, originally designed to improve the mobility of NZVI, enhanced TCE degradation performances of NZVI in the presence of anions and humic acid.
authors: Research & Development Division, Hyundai Engineering & Construction Co., Ltd., 17-5, Mabukno 240-gil, Giheung-gu, Yongin-si, Gyeonggi-do 446-912, Republic of Korea.
authors: Hong-Seok
authors: HS
authors: Kim
authors: School of Civil and Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea.
authors: Jun-Young
authors: JY
authors: Ahn
authors: School of Civil and Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea.
authors: Cheolyong
authors: C
authors: Kim
authors: Center for Water Resource Cycle, Korea Institute of Science and Technology, Hwarangdo 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors: Seockheon
authors: S
authors: Lee
authors: School of Civil and Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea. Electronic address: ihwang@pusan.ac.kr.
authors: Inseong
authors: I
authors: Hwang
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D014241:Trichloroethylene; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; D000838:Anions; D006812:Humic Substances; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; C006903:carbopol 940; D007501:Iron
keywords: Anion; Groundwater; Humic acid; Nanoscale zero-valent iron; Polyacrylic acid coating