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Individual and Co Transport Study of Titanium Dioxide NPs and Zinc Oxide NPs in Porous Media.

Kumari J, Mathur A, Rajeshwari A, Venkatesan A, S S, Pulimi M, Chandrasekaran N, Nagarajan R, Mukherjee A - PLoS ONE (2015)

Bottom Line: At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted.The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9).Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand.

View Article: PubMed Central - PubMed

Affiliation: Centre for Nanobiotechnology, VIT University, Vellore, Tamil Nadu, India.

ABSTRACT
The impact of pH and ionic strength on the mobility (individual and co-transport) and deposition kinetics of TiO2 and ZnO NPs in porous media was systematically investigated in this study. Packed column experiments were performed over a series of environmentally relevant ionic strengths with both NaCl (0.1-10 mM) and CaCl2 (0.01-0.1mM) solutions and at pH 5, 7, and 9. The transport of TiO2 NPs at pH 5 was not significantly affected by ZnO NPs in solution. At pH 7, a decrease in TiO2 NP transport was noted with co-existence of ZnO NPs, while at pH 9 an increase in the transport was observed. At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted. The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9). The retention profiles were the inverse of the plateaus of BTCs, as expected from mass balance considerations. Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand.

No MeSH data available.


Related in: MedlinePlus

Breakthrough curves of TiO2 NPs at pH 9 (with and without ZnO NPs).Breakthrough curves of TiO2 NPs in presence and absence of ZnO NPs in sand. In suspensions at 0.1, 1, and 10 mM ionic strengths in NaCl solutions and 0.01, 0.05, and 0.1 mM CaCl2 solutions at pH 9. Replicate experiments were performed under all conditions (n ≥ 2). At this pH there was increase in transport of TiO2 NPs in porous media in presence of ZnO NPs in suspension.
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pone.0134796.g003: Breakthrough curves of TiO2 NPs at pH 9 (with and without ZnO NPs).Breakthrough curves of TiO2 NPs in presence and absence of ZnO NPs in sand. In suspensions at 0.1, 1, and 10 mM ionic strengths in NaCl solutions and 0.01, 0.05, and 0.1 mM CaCl2 solutions at pH 9. Replicate experiments were performed under all conditions (n ≥ 2). At this pH there was increase in transport of TiO2 NPs in porous media in presence of ZnO NPs in suspension.

Mentions: The transport of TiO2 NPs in absence and presence of ZnO NPs in sand was examined under a series of ionic strengths in both NaCl (0.1, 1, and 10 mM) and CaCl2 (0.01, 0.05, and 0.1 mM) solutions at three different pH conditions, 5, 7, and 9. The breakthrough curves of TiO2 NPs without ZnO NPs are presented in Figs 1, 2 and 3. The zeta potential of TiO2 NPs was positive; however, the zeta potential of bare sand was negative in both the NaCl (0.1, 1, and 10 mM) and CaCl2 (0.01, 0.05, and 0.1 mM) solutions at pH 5 (S1 and S3 Tables). Therefore, an attractive electrostatic interaction was expected between TiO2 NPs and sand under the examined pH 5 for all ionic strengths. As a result, under all ionic strengths [NaCl (0.1, 1, and 10 mM); CaCl2 (0.01, 0.05, and 0.1 mM)] at pH 5, TiO2 NPs were retained in sand and very less amount of NPs had eluted out. This indicates that the delivery of TiO2 NPs without ZnO NPs was intensely dependent on pH. Previous reports by Chowdhary et al. and Solvitch et al. supported our findings as these studies also suggested that TiO2 NPs have different zeta potential values at different pH, and thus at disparate pH, the transport of TiO2 NPs varies [36, 37]. Though size and zeta potential for the TiO2 NPs were heterogeneous at different solution conditions, the BTC curves of TiO2 NPs were similar under all inspected ionic strengths (S1 Table). These results demonstrate that the impact of ionic strength on TiO2 transport was least at pH 5. A previous report on the cotransport of TiO2 NPs and C60 NPs by Cai, L et al. also validated that the impact of ionic strength on TiO2 NP transport was least at pH 5 [38]. Additionally, the BTCs of TiO2 NPs in presence of ZnO NPs at pH 5 were nearly equivalent to those without ZnO NPs, under all ionic strengths (NaCl/ CaCl2) (Fig 1). Therefore, these results clearly demonstrated that there were no significant (p> 0.05) changes in the transport of TiO2 NPs in presence of ZnO NPs at pH 5.


Individual and Co Transport Study of Titanium Dioxide NPs and Zinc Oxide NPs in Porous Media.

Kumari J, Mathur A, Rajeshwari A, Venkatesan A, S S, Pulimi M, Chandrasekaran N, Nagarajan R, Mukherjee A - PLoS ONE (2015)

Breakthrough curves of TiO2 NPs at pH 9 (with and without ZnO NPs).Breakthrough curves of TiO2 NPs in presence and absence of ZnO NPs in sand. In suspensions at 0.1, 1, and 10 mM ionic strengths in NaCl solutions and 0.01, 0.05, and 0.1 mM CaCl2 solutions at pH 9. Replicate experiments were performed under all conditions (n ≥ 2). At this pH there was increase in transport of TiO2 NPs in porous media in presence of ZnO NPs in suspension.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4529095&req=5

pone.0134796.g003: Breakthrough curves of TiO2 NPs at pH 9 (with and without ZnO NPs).Breakthrough curves of TiO2 NPs in presence and absence of ZnO NPs in sand. In suspensions at 0.1, 1, and 10 mM ionic strengths in NaCl solutions and 0.01, 0.05, and 0.1 mM CaCl2 solutions at pH 9. Replicate experiments were performed under all conditions (n ≥ 2). At this pH there was increase in transport of TiO2 NPs in porous media in presence of ZnO NPs in suspension.
Mentions: The transport of TiO2 NPs in absence and presence of ZnO NPs in sand was examined under a series of ionic strengths in both NaCl (0.1, 1, and 10 mM) and CaCl2 (0.01, 0.05, and 0.1 mM) solutions at three different pH conditions, 5, 7, and 9. The breakthrough curves of TiO2 NPs without ZnO NPs are presented in Figs 1, 2 and 3. The zeta potential of TiO2 NPs was positive; however, the zeta potential of bare sand was negative in both the NaCl (0.1, 1, and 10 mM) and CaCl2 (0.01, 0.05, and 0.1 mM) solutions at pH 5 (S1 and S3 Tables). Therefore, an attractive electrostatic interaction was expected between TiO2 NPs and sand under the examined pH 5 for all ionic strengths. As a result, under all ionic strengths [NaCl (0.1, 1, and 10 mM); CaCl2 (0.01, 0.05, and 0.1 mM)] at pH 5, TiO2 NPs were retained in sand and very less amount of NPs had eluted out. This indicates that the delivery of TiO2 NPs without ZnO NPs was intensely dependent on pH. Previous reports by Chowdhary et al. and Solvitch et al. supported our findings as these studies also suggested that TiO2 NPs have different zeta potential values at different pH, and thus at disparate pH, the transport of TiO2 NPs varies [36, 37]. Though size and zeta potential for the TiO2 NPs were heterogeneous at different solution conditions, the BTC curves of TiO2 NPs were similar under all inspected ionic strengths (S1 Table). These results demonstrate that the impact of ionic strength on TiO2 transport was least at pH 5. A previous report on the cotransport of TiO2 NPs and C60 NPs by Cai, L et al. also validated that the impact of ionic strength on TiO2 NP transport was least at pH 5 [38]. Additionally, the BTCs of TiO2 NPs in presence of ZnO NPs at pH 5 were nearly equivalent to those without ZnO NPs, under all ionic strengths (NaCl/ CaCl2) (Fig 1). Therefore, these results clearly demonstrated that there were no significant (p> 0.05) changes in the transport of TiO2 NPs in presence of ZnO NPs at pH 5.

Bottom Line: At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted.The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9).Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand.

View Article: PubMed Central - PubMed

Affiliation: Centre for Nanobiotechnology, VIT University, Vellore, Tamil Nadu, India.

ABSTRACT
The impact of pH and ionic strength on the mobility (individual and co-transport) and deposition kinetics of TiO2 and ZnO NPs in porous media was systematically investigated in this study. Packed column experiments were performed over a series of environmentally relevant ionic strengths with both NaCl (0.1-10 mM) and CaCl2 (0.01-0.1mM) solutions and at pH 5, 7, and 9. The transport of TiO2 NPs at pH 5 was not significantly affected by ZnO NPs in solution. At pH 7, a decrease in TiO2 NP transport was noted with co-existence of ZnO NPs, while at pH 9 an increase in the transport was observed. At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted. The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9). The retention profiles were the inverse of the plateaus of BTCs, as expected from mass balance considerations. Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand.

No MeSH data available.


Related in: MedlinePlus