title: Transport of carboxyl-functionalized carbon black nanoparticles in saturated porous media: Column experiments and model analyses.
abstract: The aim of this study was to investigate the transport behavior of carboxyl-functionalized carbon black nanoparticles (CBNPs) in porous media including quartz sand, iron oxide-coated sand (IOCS), and aluminum oxide-coated sand (AOCS). Two sets of column experiments were performed under saturated flow conditions for potassium chloride (KCl), a conservative tracer, and CBNPs. Breakthrough curves were analyzed to obtain mass recovery and one-dimensional transport model parameters. The first set of experiments was conducted to examine the effects of metal (Fe, Al) oxides and flow rate (0.25 and 0.5 mL min(-1)) on the transport of CBNPs suspended in deionized water. The results showed that the mass recovery of CBNPs in quartz sand (flow rate=0.5 mL min(-1)) was 83.1%, whereas no breakthrough of CBNPs (mass recovery=0%) was observed in IOCS and AOCS at the same flow rate, indicating that metal (Fe, Al) oxides can play a significant role in the attachment of CBNPs to porous media. In addition, the mass recovery of CBNPs in quartz sand decreased to 76.1% as the flow rate decreased to 0.25 mL min(-1). Interaction energy profiles for CBNP-porous media were calculated using DLVO theory for sphere-plate geometry, demonstrating that the interaction energy for CBNP-quartz sand was repulsive, whereas the interaction energies for CBNP-IOCS and CBNP-AOCS were attractive with no energy barriers. The second set of experiments was conducted in quartz sand to observe the effect of ionic strength (NaCl=0.1 and 1.0mM; CaCl2=0.01 and 0.1mM) and pH (pH=4.5 and 5.4) on the transport of CBNPs suspended in electrolyte. The results showed that the mass recoveries of CBNPs in NaCl=0.1 and 1.0mM were 65.3 and 6.4%, respectively. The mass recoveries of CBNPs in CaCl2=0.01 and 0.1mM were 81.6 and 6.3%, respectively. These results demonstrated that CBNP attachment to quartz sand can be enhanced by increasing the electrolyte concentration. Interaction energy profiles demonstrated that the interaction energy profile for CBNP-quartz sand was compressed and that the energy barrier decreased as the electrolyte concentration increased. Furthermore, the mass recovery of CBNPs in the presence of divalent ions (CaCl2=0.1 mM) was far lower than that in the presence of monovalent ions (NaCl=0.1 mM), demonstrating a much stronger effect of Ca(2+) than Na(+) on CBNP transport. Mass recovery of CBNPs at pH 4.5 was 55.6%, which was lower than that (83.1%) at pH 5.4, indicating that CBNP attachment to quartz sand can be enhanced by decreasing the pH. The sticking efficiencies (α) calculated from the mass recovery by colloid filtration theory were in the range from 2.1×10(-2) to 4.5×10(-1), which were far greater than the values (2.56×10(-6)-3.33×10(-2)) of theoretical sticking efficiencies (αtheory) calculated from the DLVO energy by the Maxwell model.
authors.affiliation: Environmental Functional Materials & Biocolloids Laboratory, Seoul National University, Republic of Korea.
authors.forename: Jin-Kyu
authors.initials: JK
authors.lastname: Kang
authors.affiliation: Environmental Functional Materials & Biocolloids Laboratory, Seoul National University, Republic of Korea.
authors.forename: In-Geol
authors.initials: IG
authors.lastname: Yi
authors.affiliation: Environmental Functional Materials & Biocolloids Laboratory, Seoul National University, Republic of Korea.
authors.forename: Jeong-Ann
authors.initials: JA
authors.lastname: Park
authors.affiliation: Environmental Functional Materials & Biocolloids Laboratory, Seoul National University, Republic of Korea; Department of Rural Systems Engineering and Research Institute of Agriculture and Life Sciences, Seoul National University, Republic of Korea. Electronic address: songbkim@snu.ac.kr.
authors.forename: Song-Bae
authors.initials: SB
authors.lastname: Kim
authors.affiliation: Department of Mineral Resources and Energy Engineering, Chonbuk National University, Republic of Korea.
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Mineral Resources and Energy Engineering, Chonbuk National University, Republic of Korea.
authors.forename: Yosep
authors.initials: Y
authors.lastname: Han
authors.affiliation: Division of Risk Assessment, National Institute of Environmental Research, Republic of Korea.
authors.forename: Pil-Je
authors.initials: PJ
authors.lastname: Kim
authors.affiliation: Division of Risk Assessment, National Institute of Environmental Research, Republic of Korea.
authors.forename: Ig-Chun
authors.initials: IC
authors.lastname: Eom
authors.affiliation: Division of Risk Assessment, National Institute of Environmental Research, Republic of Korea.
authors.forename: Eunhye
authors.initials: E
authors.lastname: Jo
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D003102:Colloids; D005290:Ferric Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D062070:Hydrology / Q000379:methods; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry; D009994:Osmolar Concentration; D016062:Porosity; D011791:Quartz; D012822:Silicon Dioxide; D012989:Soil Pollutants / Q000737:chemistry; D053260:Soot / Q000737:chemistry; D014867:Water; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D012989:Soil Pollutants; D053260:Soot; D014874:Water Pollutants, Chemical; D014867:Water; D011791:Quartz; C000499:ferric oxide; D012822:Silicon Dioxide; D000537:Aluminum Oxide
keywords: Carbon black nanoparticles; Column experiment; Metal oxide-coated sand; Quartz sand; Saturated porous media