title: Transport and aggregation of rutile titanium dioxide nanoparticles in saturated porous media in the presence of ammonium.
abstract: The widely used artificial nanoparticles (NPs) and the excess of ammonium (NH4+) fertilizers are easily released into the natural environment. So, clarifying the mobility of NPs in the presence of NH4+is therefore of great urgency and high priority. Currently, few studies focus on the transport and deposition of nanoparticle titanium dioxide (nTiO2) in single and binary systems containing NH4+, especially describing this process by a mathematical model. In this work, the comparison between the transport and retention of rutile nTiO2in single and binary electrolyte solutions of NH4Cl and/or NaCl (0.5-50 mM) were conducted at pH 6.0 and 8.0 through running the column experiments. Experimental results show that the aggregation and retention of nTiO2in solution containing mono-valence cations obeys the order as follows: NH4+> Na+> Na++ NH4+at the same ion strength (IS). It is attributed to the lower critical coagulation concentration (CCC) of rutile nTiO2in NH4+than that in Na+solution. In particular, the simultaneous presence of NH4+and Na+favors the transportability of nTiO2due to the strong competitive adsorption on the surface of NPs. The two-site kinetic retention model provides the good simulation for their transport behavior. The likely mechanism is that the secondary energy minimum of nTiO2in NH4+system associated with the greater K2at surface Site 2 (from model) on sand can be explained for the more reversible deposition. Ammonium leachate associated with NPs can thus be considered a serious concern.
authors.affiliation: Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou 215009, China.
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Xu
authors.affiliation: Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou 215009, China. Electronic address: nanxu@mail.usts.edu.cn.
authors.forename: Nan
authors.initials: N
authors.lastname: Xu
authors.affiliation: Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou 215009, China.
authors.forename: Xueying
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou 215009, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Guo
authors.affiliation: Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou 215009, China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou 215009, China.
authors.forename: Dongtian
authors.initials: D
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D064751:Ammonium Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry*; D009994:Osmolar Concentration; D016062:Porosity; D012822:Silicon Dioxide; D012996:Solutions; D014025:Titanium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D007477:Ions; D012996:Solutions; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D012822:Silicon Dioxide; D014025:Titanium
keywords: Aggregation; Ammonium; Model; Nanoparticles; Titanium dioxide; Transport