title: Nitrate reduction using nanosized zero-valent iron supported by polystyrene resins: role of surface functional groups.
abstract: To probe the role of host chemistry in formation and properties of the inside nano-zero valent iron (nZVI), we encapsulated nZVI within porous polystyrene resins functionalized with -CH(2)Cl and -CH(2)N(+)(CH(3))(3) respectively and obtained two hybrid nZVIs denoted Cl-S-ZVI and N-S-ZVI. 14.5% (in Fe mass) of nZVI particles were distributed in N-S within a ring-like region (about 0.10 mm in thickness) of size around ∼ 5 nm, whereas only 4.0% of nZVI particles were entrapped near the outer surface of Cl-S of size > 20 nm. -CH(2)N(+)(CH(3))(3) is more favorable than -CH(2)Cl to inhibit nZVI dissolution into Fe(2+) ions under acidic pH (3.0-5.5). 97.2% of nitrate was converted into ammonium when introducing 0.12 g N-S-ZVI into 50 mL 50 mg N/L nitrate solution, while that for Cl-S-ZVI was 79.8% under identical Fe/N molar ratio. Under pH = 2 of the effectiveness of nZVI was 88.8% for nitrate reduction, whereas that for Cl-S-ZVI was only 14.6% under similar conditions. Nitrate reduction by N-S-ZVI exhibits relatively slower kinetics than Cl-S-ZVI, which may be related to different nZVI distribution of both composites. The coexisting chloride and sulfate co-ions are favorable for the reactivity enhancement of N-S-ZVI whereas slightly unfavorable for Cl-S-ZVI. The results demonstrated that support chemistry plays a significant role in formation and reactivity of the encapsulated nZVI, and may shed new light on design and fabrication of hybrid nZVIs for environmental remediation.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China.
authors.forename: Zhenmao
authors.initials: Z
authors.lastname: Jiang
authors.forename: Lu
authors.initials: L
authors.lastname: Lv
authors.forename: Weiming
authors.initials: W
authors.lastname: Zhang
authors.forename: Qiong
authors.initials: Q
authors.lastname: Du
authors.forename: Bingcai
authors.initials: B
authors.lastname: Pan
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Quanxing
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D055598:Chemical Phenomena; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D009566:Nitrates; D011137:Polystyrenes; D012117:Resins, Synthetic; D012996:Solutions; D007501:Iron