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2005 Progress Report: Adsorption and Release of Contaminants onto Engineered Nanoparticles
EPA Grant Number: R831718Title: Adsorption and Release of Contaminants onto Engineered Nanoparticles
Investigators: Tomson, Mason B.
Institution: Rice University
EPA Project Officer: Lasat, Mitch
Project Period: August 1, 2004 through July 31, 2007
Project Period Covered by this Report: August 1, 2004 through July 31, 2005
Project Amount: $333,797
RFA: Exploratory Research to Anticipate Future Environmental Issues: Impacts of Manufactured Nanomaterials on Human Health and the Environment (2003)
Research Category: Nanotechnology , Health Effects
Description:
Objective:Little is known about the environmental fate of manufactured nanomaterials. Sorption often is the most important fate mechanism for environmental contaminants. The objective of this research project is to test the following four hypotheses: (1) carbon nanostructures have a high capacity for sorption/desorption hysteresis with polynuclear aromatic hydrocarbons and other common organic contaminants; (2) the sorption capacity of inorganic nanomaterials for heavy metals is the same as the corresponding bulk crystals when corrected for surface area; (3) sorption of naturally occurring humic materials and surfactants to metal oxide and carbon nanomaterials will diminish the sorption capacity of heavy metals on oxides and increase the sorption of hydrocarbons on carbon nanomaterials; and (4) the transport of nanoparticles in soils, sediments, and porous medial will be vastly greater than the corresponding colloids or bulk materials.
Progress Summary:During Year 1 of this project, we have characterized successfully the sorption/desorption behavior of both organic and inorganic contaminants to nanomaterials and the fate and transport of naphthalene (an organic contaminant) and colloidal C60 particles in soil column.
Environmental Fate of Carbon Nanomaterials
Many soils or sediments contain various forms of carbonaceous materials such as coals, kerogens, and black carbons, which have been reported to have high affinity for hydrophobic organic contaminants. C60 might have similarly important environmental impact as to other forms of carbon (e.g., black carbons). Although C60 is virtually insoluble in water, “nano-C60 particles” (a term used to refer to underivatized C60 crystalline nanoparticles, stable in water for months, mean diameter approximately 100 nm in this study) can be formed in water simply by stirring or by dissolving C60 in nonpolar solvents, mixing into water, and removing the solvents. In this study, the adsorption and desorption of naphthalene and 1,2-dichlorobenzene with aqueous nano-C60 particles prepared by both methods was investigated. To compare the adsorptive properties of C60 with other carbons (e.g., naturally occurring organic carbon in soils) and activated carbon, adsorption and desorption of naphthalene with Anacostia River sediment (foc = 3.7%) and activated carbon particles (commercial and nanoactivated carbon particles prepared in our lab) also were conducted and compared with that of C60.
Results show that adsorption to nano-C60 particles is similar to that of nanoactivated carbon particles and is stronger that that of soil organic carbon. Desorption hysteresis was observed for naphthalene desorption from all three forms of carbon tested: C60, activated carbon, and organic carbon. A two-compartment sorption model in the form:
was used to describe naphthalene adsorption and desorption with these three forms of carbon, where Kd1st and Kd2nd are solid-water distribution coefficients for the first and the second compartment; q2nd max (µg/g) is defined as a maximum sorption capacity for the second compartment; and the factor f (0 ≤ f ≤ 1) denotes the fraction of the second compartment that is filled at the time of exposure. Data of naphthalene adsorption and desorption with C60 (Figure 1), activated carbon, and soil organic carbon were fitted with this two-compartment model very well, indicating that there may be a common pattern for the adsorption and desorption of naphthalene with these three forms of carbon. Therefore, it may be possible to predict the properties of nano-carbons, such as C60, from that of other carbon forms. This finding may have important environmental significance.
Figure 1. Adsorption and Desorption of Naphthalene With Nano-C60. •, adsorption of naphthalene to nano-C60; ◊, □, , ○, +, desorption of naphthalene from nano-C60. Straight line, a linear isotherm in the form of q (μg/g) = 103.75 Cw (μg/mL); upper curve, model fitting curve assuming two-compartment desorption model. Dotted lines, two compartment desorption model fitting curve with f = 0.3, 0.45, 0.55, and 0.7, respectively.
It has been reported that nano-C60 particles are toxic to fish cells and cultured human cells, thus people may be more concerned about the potential exposure to C60 if it is mobile in water. One might expect that C60 would not enter groundwater in great quantities because of the insolubility of C60 in water. Water-stable nano-C60 particles, however, can be formed in water by several simple methods, as discussed above, indicating that C60 might be mobile in groundwater. Besides, dissolved organic matter in groundwater has been reported to enhance significantly the partition of neutral organic contaminants into water and thus enhance the transport of those contaminants. It is unknown whether the release of C60 and other nanosized carbonaceous nanomaterials into aqueous environments will have the similar effect. Therefore, it is of central importance to investigate the C60 transport in water/sediment and its effect on contaminant transport.
In this work, the transport of nano-C60 particles through a sandy soil column (foc = 0.0027%) was investigated for the first time. Nano-C60 particles showed limited mobility at typical groundwater Darcy velocity. At the Darcy velocity of 3 ft/day, the maximum nano-C60 particles breakthrough was only 47 percent, and an unexpectedly high deposition of nano-C60 to the soil column was observed shortly after the peak value, probably indicating an irreversible sorption of nano-C60 particles on the soil column. It might be because the accumulation of nano-C60 on the collector surface served as favorable sites for subsequent nano-C60 deposition. Nano-C60 particles were more mobile in the soil column at higher flow velocities (e.g., 30 and 90 ft/day) (Figure 2). A model developed for the transport of colloids in porous media by Yao, et al., and O’Melia, et al., was used to describe nano-C60 particles transport in the soil column. The theoretical single collector efficiency, the particle attachment efficiency, and the maximum particle travel distance were calculated for nano-C60 particles transport at different flow velocities. Experimental results showed that at the flow velocity of 30 ft/day, nano-C60 particles could travel 68 cm through the soil column before 99.9 percent of the particles were immobilized; at the flow velocity of 90 ft/day, nano-C60 particles could travel 1.32 m through the soil column before 99.9 percent of the particles were immobilized. Spiked release of nano-C60 particles was observed repeatedly on flow resumption following a few days period of flow shut-in. Spiked release of nano-C60 particles also was observed during the change of flow velocities. This observed phenomenon may have broad environmental significance.
The transport of naphthalene through the same soil column with 0.18 percent of nano-C60 particles deposited was measured. The observed retardation factor for the naphthalene breakthrough curve with the Lula/0.18 percent-nano-C60 column was about 13, indicating that nano-C60 particles deposited in the soil column adsorbed naphthalene similarly to soil organic carbon.
Adsorption and Desorption of Heavy Metal and Arsenic to Metal Oxide Nanoparticles
The objectives of the current study are to investigate the effect of particle size on adsorption and desorption of typical environmental pollutants (i.e., arsenic and cadmium) onto metal oxide bulk crystals versus nanoparticles (anatase and magnetite) and to examine the competitive sorption between naturally occurring humic materials and heavy metals. In collaboration with Dr. Colvin’s group through the support of the Center of Biological and Environmental Nanotechnology (CBEN) at Rice University, laboratory-synthesized magnetite also was studied. On a surface-area basis, cadmium adsorptions to different sized anatase nanocrystals are similar. The maximum adsorption densities for arsenic to magnetite also are similar for commercially
Figure 2. Nano-C60 Breakthrough Curves at Different Flow Rates. X, flow rate is 1 mL/hour (v = 0.38 m/day); o, flow rate is 10 mL/hour (v = 3.8 m/day); ∆, flow rate is 30 mL/hour (v = 11.4 m/day). The interruption of flow between curve a and b, b and c, and c and d is 3 days each.
prepared large magnetite crystals (300 nm) and magnetite nanoparticles (20 nm). Surprisingly, the adsorption capacity for arsenic to laboratory-synthesized magnetite (11.72 nm) is significantly higher than the commercially available bulk and nanocrystals (Table 1). Laboratory-synthesized magnetite nanoparticles can remove approximately 100 times more arsenic than lager commercial materials. With respect to desorption, the cadmium desorption from both particle sizes appeared to be completely reversible; however, arsenic was not released readily from magnetite nanoparticles, presumably because the binding of the adsorbed arsenic results in the formation of highly stable iron-arsenic complexes. The presence of nanoparticle organic molecule (NOM) decreased adsorption of both arsenic species to magnetite nanoparticles. NOM in the solution probably competes with arsenite and arsenate for surface sites on magnetite nanoparticles. With joint support from CBEN, these results currently are applied to test the efficiency of magnetite nanoparticles in removing arsenic from drinking water. A U.S. patent application has been submitted.
Table 1. Weight-Based and Surface Area-Based Langmuir Adsorption Isotherm Parameters
| Arsenic | Magnetite |
pH |
b (L/μmol) |
qmax |
qmax |
qmax.b |
AS(III) |
300 nm |
8.0 |
0.05 |
20.8 |
5.62 |
0.28 |
AS(III) |
20 nm |
8.0 |
0.04 |
388.9 |
6.48 |
0.23 |
AS(III) |
11.72 nm |
8.0 |
0.02 |
1532 |
15.49 |
0.32 |
8.0 |
0.02** |
1800 |
18.22 |
0.38 |
The surface-to-volume ratios of engineered nanomaterials can be as large as 30 percent by number, and clearly, the surface chemistry of these species will be essential for understanding the fate of engineered nanoparticles in the environment. Specifically, research will continue to explore the surface chemistry and adsorption/desorption of environmental contaminants with nanoparticles. Nanomaterials used will include fullerenes, single-walled nanotubes, anatase, magnetite, silica, and alumina. Adsorbates will include humic materials, surfactants, naphthalene, phenanthrene, chlorinated aromatic compounds, heavy metals lead, cadmium, and arsenic. The interaction of uncoated nanoparticles and humic and surfactant coated nanoparticles in the presence of soil and sediments will be determined with batch and column experiments. The sorption and desorption of common hydrophobic organic compounds and of heavy metals to both coated and uncoated nanomaterials will be measured. Contaminant/particle interactions also will be characterized using specific surface probes. This research will provide explicit fate models that can be used in exposure assessment for nanoparticles. With bound adsorbates, a number of spectroscopic tools can be used to discern the coverage and bonding at nanocrystal surfaces.
Journal Articles on this Report: 9 Displayed | Download in RIS Format
| Other project views: | All 62 publications | 18 publications in selected types | All 17 journal articles |
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Chen W, Lakshmanan K, Kan AT, Tomson MB. A program for evaluating dual-equilibrium desorption effects on remediation. Ground Water 2004;42(4):620-624. |
R831718 (2005) R825513C023 (Final) R825513C024 (Final) R828773 (Final) |
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Cheng X, Kan AT, Tomson MB. Naphthalene adsorption and desorption from aqueous C60 fullerene. Journal of Chemical and Engineering Data 2004;49(3):675-683. |
R831718 (2005) R828773 (Final) R828773C004 (2003) |
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Cheng X, Kan AT, Tomson MB. Study of C60 transport in porous media and the effect of sorbed C60 on naphthalene transport. Journal of Materials Research 2005;20(12):3244-3254. |
R831718 (2005) R828773 (Final) |
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Cheng X, Kan AT, Tomson MB. Uptake and sequestration of naphthalene and 1,2-dichlorobenzene by C60. Journal of Nanoparticle Research 2005;7(4-5):555-567. |
R831718 (2005) R828773 (Final) |
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Gao Y, Wahi R, Kan AT, Falkner JC, Colvin VL, Tomson MB. Adsorption of cadmium on anatase nanoparticles-effect of crystal size and pH. Langmuir 2004;20(22):9585-9593. |
R831718 (2005) R828773 (Final) R828773C004 (2003) |
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Gao Y, Kan AT, Tomson MB. Response to comment on “critical evaluation of desorption phenomena of heavy metals from natural sediments”. Environmental Science & Technology 2004;38(17):4703. |
R831718 (2005) |
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Kan AT, Fu G, Tomson MB. Adsorption and precipitation of an aminoalkylphosphonate onto calcite. Journal of Colloid and Interface Science 2005;281(2):275-284. |
R831718 (2005) R828773 (Final) |
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Tomson MB, Kan AT, Fu G. Inhibition of barite scale in the presence of hydrate inhibitors. SPE Journal 2005;10(3):256-266. |
R831718 (2005) R828773 (Final) |
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Yean S, Cong L, Yavuz CT, Mayo JT, Yu WW, Kan AT, Colvin VL, Tomson MB. Effect of magnetite particle size on adsorption and desorption of arsenite and arsenate. Journal of Nanoparticle Research 2005;20(12):3255-3264. |
R831718 (2005) R828773 (Final) |
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fullerene, C60, arsenic, environmental impact, nanoparticles.
, POLLUTANTS/TOXICS, Water, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, Scientific Discipline, RFA, Arsenic, Technology for Sustainable Environment, Sustainable Environment, Technology, Ecological Risk Assessment, Chemicals Management, Environmental Engineering, Water Pollutants, Environmental Chemistry, risk assessment, nanotechnology, environmentally applicable nanoparticles, fate and transport, environmental hazard assessment, clean technologies, bioacummulation, single walled carbon nanotubes, polynuclear aromatic hydrocarbons, green chemistry, engineering, nanoparticles, chemical behavior, nanomaterials, alternative materialsRelevant Websites:
http://www.ruf.rice.edu/~ceedept/
Progress and Final Reports:
Original Abstract
Final Report