(MOGFC) for Heavy Metal Removal from Highway

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KEYWORDS: Highway runoff, Adsorption, Heavy metal, Bentonite, Zeolite, Copper, Zinc,. OGFC, MOGFC. ... Pollutant Discharge Elimination System (NPDES) enforced by the U.S. Environmental. Protection ..... 80. 90. 100. 0.00. 0.25. 0.40. 0.55. 0.70. C u R em oval E fficiency (%. ) ... D7064, West Conshohocken, PA. Baker, H.
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WEFTEC 2015

Development and Evaluation of Multi-Functional Open Graded Friction Course (MOGFC) for Heavy Metal Removal from Highway Runoff as an in Situ Treatment Imtiaz U Ahmed1, Daniel D Gang1*, Mohammad J Khattak1, Hashim R Rizvi1 1

Department of Civil Engineering, University of Louisiana at Lafayette, P.O. Box 42291, Lafayette, LA 70504, USA. *Corresponding author. Tel.:+1-304-545-6748; E-mail: [email protected] ABSTRACT: The primary objective of this study was to develop and evaluate multifunctional open graded friction course (MOGFC) for using as an in situ treatment technique to remove Cu and Zn from highway runoff. MOGFC was prepared by adding different adsorbents into the void of OGFC. Two different types of adsorbents were selected based on cost, applicability, and availability. A series of laboratory tests were conducted to evaluate the adsorption capacity of the adsorbents and metal removal performance of MOGFC. Bentonite and zeolite respectively showed maximum adsorpton capcity of 1.44 and 10.63 mg/g for copper and 1.18 and 1.96 mg/g for zinc. MOGFC metal removal efficiency was significantly improved after introducing adsorbents into OGFC. The maximum removal efficiency of bentonite and zeolite were found 76.3% and 73.7% for copper and 41.8% and 43.7% for zinc respectively. The lower removal efficiency of zinc compared to copper agrees the result observed in adsorption capacity of adsorbents. Therefore, this in situ technique has a potential for field application due to its environmental and economic benefits. KEYWORDS: Highway runoff, Adsorption, Heavy metal, Bentonite, Zeolite, Copper, Zinc, OGFC, MOGFC. INTRODUCTION Highways have been recognized as a common source of various pollutants such as heavy metals, suspended solids, and organic compounds for the environment (Shaheen 1975; Falahi-Ardakani 1984). Such pollutants can be attributed to the abrasion of asphalt and tires, corrosion of crash barriers, deposition of exhaust products, and leakage from vehicles. Highway runoff conveys a large portion of these contaminants to adjacent water bodies, resulting in an accumulation of pollutants, especially under high traffic volumes. Studies have shown that highway runoff, though it may not demonstrate acute toxicity, can have chronic toxicity resulting from bioaccumulation of pollutants (Barrett et al. 1995a). Highway runoff is a non-point pollution source (Hoffman et al. 1985; Wu et al. 1998) and it is a significant contributor to water quality degradation when combined with other sources such as urban runoff (Barrett et al. 1995b). Non-point sources of urban runoff have a serious detrimental effect on water quality (EPA, 1993) and an estimated 50% to 70% of heavy metal pollutants from non-point sources are attributed to roadways (Barrett et al. 1995a).

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Copper (Cu) and zinc (Zn) are the two predominant heavy metal found in highway runoff. Cu contribution to the highway runoff is mainly from brake lining wear, metal plating, moving engine parts, and bearing and bushing wear. Zn originates from tire wear, motor oil, and grease (EPA 1993). Table 1 lists typical metals found in highway runoff as reported in the literature (Barrett et al. 1995a). Heavy metals can impact the receiving catchment, groundwater quality, and surrounding ecosystem (Barrett et al. 1995b; Warren and Birch 1986). Therefore, significant environmental benefits can be realized by reducing all such heavy metals in highway runoff. Table 1. Range of Highway Runoff Metal Concentrations (Barrett et al. 1995a) Constituents Concentration (mg/L) Load (kg/ha/yr) Load (kg/ha/event) Zn 0.06-0.93 0.22-10.40 0.004-0.025 Cd 0.04 0.007-0.037 0.002 Ni 0.05 0.07 Cu 0.02-7.03 0.03-4.7 0.0063 Fe 2.40-10.30 4.40-28.80 0.56 Pb 0.07-1.78 0.08-21.20 0.008-0.22 Cr 0.04 0.012-0.10 0.0031 Several regulatory requirements have been enforced to protect the environment from the impacts of urban and highway runoff. Highway construction and other development cannot be undertaken in urban areas until regulatory agencies approve. On the national level, the National Pollutant Discharge Elimination System (NPDES) enforced by the U.S. Environmental Protection Agency (EPA) requires a storm water discharge permit for highways in urban areas. In addition to this national requirement, state or municipal rules may also apply. Therefore, both environmental response and regulatory mandates prompt the need for highway runoff treatments. Highway runoff collection and treatment systems include a variety of structural practices such as sand filters, retention and detention structures and nonstructural practices including but not limited to vegetated buffer strips and grassy swales (Barrett et al. 1995b). Though useful in many aspects, these methods often require high resources like high investment and costly maintenance. Some methods require substantial land area for the treatment setup, and are not able to function properly nearby a bridge or deck with long spans, because it is not possible to use a pond, vegetative strip, or other external treatment methods adjacent to those structures. Open graded friction course (OGFC), also known as permeable friction courses (PFC) is an approximately 50 mm thick porous asphalt concrete layer (Cooley et al. 2009), laid on top of a conventional concrete or asphalt surface to provide an alternative to the aforementioned methods for treating highway runoff. The porous OGFC is produced by eliminating the fine aggregate from conventional hot mix asphalt (HMA). Generally, an OGFC overlay consists of 18% to 22% air voids (Barrett 2008). Highway runoff soaks into the porous OGFC layer and is held in the pore spaces until it is drained out laterally through under drains or percolates through the subbase (Kandhal 2002; Maestri and Lord 1987).

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A significant amount of research related to OGFC has been conducted in the United States over the past 50 years (Huber 2000). OGFC provides benefit to the transportation agencies by collecting water in the voids and eliminating surface water flows that reduces splash, spray and hydroplaning; improves visibility and traction; and decreases noise (NCHRP 2009; Huber 2000; Rungruangvirojn and Kanitpong 2010). All the advantages cumulatively improve the safety of the roadway. In addition, OGFC surface decreases sunlight reflections, headlight glare from the pavement, which enables road signs and markings more visible to the drivers (Tappeiner 1993). The installation of OGFC overlay can produce noticeable improvement of the highway runoff water quality, which is attributed to the pollutant retention by pores. Several studies have demonstrated that runoff treated by OGFC overlay is less polluted due to particulate retention in the pore spaces. Pagotto et al. (2000) found that runoff water quality from porous HMA was improved in comparing with non-porous HMA in France. In an early study of OGFC overlay, 60% reduction of solids was reported by Stotz and Krauth (1994) comparing with conventional pavement. Barrett (2008) also conducted a similar research and reported significant decrease in concentrations of particulates related to highway pollutant, specifically suspended solids, which exhibited about 92%, decrease. In another study, Wang et al. (2011) found that OGFC overlay has improved runoff water quality due to retention of particulate matters such as total suspended solids (TSS) into its pore spaces. Considering potential benefits towards highway runoff water quality and highway wearing courses management, many state departments of transportations (DOT) are increasingly adopting the use of OGFC overlay (Asphalt Pavement Alliance, 2003). However, a shortcoming of traditional OGFC is that it has little to no ability to remove dissolved/non particulate (as opposed to particulate) related pollutants such as heavy metals from highway runoff. It is hypothesized that the pore size in the OGFC layer is too large to retain colloidal and dissolved constituents, especially heavy metal ions (Cu2+ and Zn2+). Unfortunately, about 20% to 70% of heavy metals are in dissolved form in highway runoff (Barrett et al. 1995a), depending on the environmental conditions (pH of storm water) and the amount and activities of microorganisms that contribute to the water solubility of metals. OBJECTIVES OF STUDY Overall goal of this study is to develop and evaluate a novel multi-functional open graded friction course (MOGFC) having high adsorption capacity which will overcome the shortcoming of OGFC and remove heavy metals from highway storm water runoff. The specific objectives are: • To evaluate the possible additives which will have high adsorption capacity, low cost and applicable for OGFC; • To explore a new methodology for the addition of the additives to the OGFC mixtures to produce an MOGFC that is effective for removal of heavy metals; • To characterize OGFC and MOGFC by determining the important parameters including the permeability, air voids, and adsorption capacity of the MOGFC mixtures for heavy metals (primary focus in Cu and Zn) in highway runoff.

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The long term goal of this research is to develop a new generation of multifunctional materials for highway pavement design practice. This unique treatment technique will have both environmental and economic benefits, as it eliminates the need for external treatment facilities for highway runoff. Thus, it has the potential to save on land usage and costs over traditional methods such as wetlands and detention ponds. Also, the in situ technique would be easy to apply on long spans bridges, where it is not possible to use a pond, vegetative strip, or other external treatment methods. METAL REMOVAL MECHANISM A novel in situ storm water management technique is proposed in this study, which will create a new type of material by adding technically selected additives into the voids of the OGFC mixtures. The resulting new material called MOGFC, will have an adsorption capability for heavy metals, and would form an in situ treatment for highway runoff. The additives in MOGFC stay in the pore spaces/voids and adsorb heavy metals when water soaks into the voids vertically and drains out laterally. Figure 1 illustrates the concept of pollutants (heavy metals) removal mechanism. A typical cross section of OGFC sample is presented in the upper part of the figure where interconnected and not connected air voids are shown. Through the interconnected air voids water can drain out laterally from the sides. In the bottom part of the figure a typical cross section of MOGFC sample is shown. Here adsorbents (in particulate form) can be seen at the edge of interconnected air voids. Polluted storm water percolates vertically into the MOGFC, travel through interconnected air voids where adsorbents stay and adsorb heavy metals from the polluted water. Subsequently, the treated water percolating further and drains out through the horizontal channel of interconnected air voids.

Fig. 1. MOGFC concept and metal removal mechanism

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MATERIALS AND METHODS OGFC Preparation Various OGFC samples were prepared with different air voids on the basis of same aggregate composition (Figure 2). The air voids were varied by keeping the sample thickness constant and changing the mass and compaction level (the number of gyrations) using Superpave Gyratory Compactor. Limestone aggregates and viscosity graded polymer modified asphalt binder (PAC40) were used to construct OGFC samples. Both materials were obtained from the local contractors. The mix design yielded 5.5% asphalt content and 22% total air voids in the mixture at 50 numbers of gyrations. All samples used in the study were 150 mm (5.9 inch) in diameter and 76 mm (3 inch) thick. The aggregate gradation used in the study is shown in Table 2.

Fig. 2. Typical OGFC samples Table 2. Aggregate gradation data for OGFC mixtures US

Sieve Size

¾”

½”

3/8”

No. 4

No. 8

No. 16

No. 200

Metric

mm

19

12.5

9.5

4.75

2.36

1.18

0.075

Gradation

% Passing

100

89

58

15

5.5

3.5

3.0

MOGFC Preparation At first required amount of adsorbent was determined based on the mass of OGFC sample. Then a portion of the selected amount of adsorbent was evenly distributed on the surface of the sample. After that OGFC sample was gently transferred to a mechanical sieve shaker. The sample was secured firmly and locked with two sided clamp of the sieve shaker. The sample was shaken until adsorbent particles were entered into the interconnected air voids of OGFC. This

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procedure was repeated for several times with remaining amount of adsorbents. Total shaking time for the sample was 30 minutes. Adsorbents and Chemicals In this research two different adsorbents were tested to determine their adsorption capacity for Cu and Zn removal. The adsorbents were: 1) Bentonite and 2) Zeolite. Bentonite was obtained from Texas Sodium bentonite Inc. (Texas) in a 50 lb bag. It has light tan to grey solid color with specific gravity of 2.5 and particle size ranging from 0.35 mm to 0.65 mm. Zeolite was obtained from IDA-ORE Inc. (Idaho) in a 25 lb bag. It has light brown color with 2.47 specific gravity and particle size of about 14 to 40 mesh which is equivalent to 0.42 mm to 1.2 mm. Chemical solutions were prepared using de-ionized water and analytical grade chemicals. Copper standard solution of 1 mg/ml Cu in 2% HNO 3 and zinc standard solution of 1 mg/ml Zn in 2% HCl for using with Atomic Absorption Spectrometer (AAS) were obtained from ACROS organics (Geel, Belgium). These two solutions were referred as stock solution. Intermediate and standard solutions were prepared before the experiment by diluting the stock solution with deionized water, obtained from the environmental engineering laboratory in university of Louisiana at Lafayette. Each time, all glassware and plasticware were washed with soap and water, followed by a tap water rinse and three final rinses with deionized water. Metal Adsorption Experiment The adsorption of Cu and Zn on different adsorbents were carried out using the batch method at room temperature (25°C). A desired amount of adsorbent was placed in several 250 ml conical flasks. 100 ml of Cu and Zn solution of 5 mg/L concentration was prepared and mixed with the adsorbent. One sample of the same concentration without adsorbent (blank) was also prepared and treated under the same condition. This solution was used as a reference to establish the initial concentration for the flasks containing adsorbent. All conical flasks were capped and placed on an Excella incubator shaker (Model E24, New Brunswick Scientific Co.) for 24 h. The flasks were then removed and solutions were filtered using a filter paper (Whatman Q5 dia 47 mm). The metal concentration (Cu and Zn) of the filtered aqueous phase was determined by a Perkin Elmer Atomic Absorption Spectrometer (AAS) (Model PinAAcle 900T). Table 3 lists the operational parameters of the AAS. The solid phase concentration was calculated by subtracting the final concentration from initial one using Eq. (1). (𝐶𝐶˳−𝐶𝐶𝑒𝑒 )𝑉𝑉 q꞊ (1) 𝑚𝑚

Where q ꞊ equilibrium solid-phase concentration (mass adsorbate/mass adsorbent), (mg/g); m ꞊ mass of adsorbent, (g); Ce ꞊ equilibrium concentration of the metal in the liquid phase, (mg/L); C 0 ꞊ initial concentration of solute in the untreated solution, (mg/L); V ꞊ volume of solution, (L).

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Table 3. Operational Parameters of AAS for Copper (Cu) and Zinc (Zn) Analysis Metal

Type of Lamp

Amperage (mA)

Wavelength (nm)

Energy

Flame gases

15

Slit width (nm) 0.7

Copper

HCL

324.75

91

Airacetylene

Zinc

HCL

15

0.7

213.86

54

Airacetylene

Acetylene flow rate (L/min) 2.50 3.20

Isotherm Models Freundlich model (Eq. 2) and Langmuir model (Eq. 3) were used in this study. A non-linear curve fitting technique was used to fit experimental data with these two models. The Freundlich isotherm is most frequently used to describe the adsorption of inorganic and organic components in solution (Namasyvayam et al. 2003). This fairly satisfactory empirical isotherm can be used for a non-ideal sorption that involves heterogeneous sorption and expressed as: n q e = K F𝐶𝐶𝑒𝑒 1/ (2) P

Where, q e (mg/g) is the amount of metal adsorbed, 𝐶𝐶𝑒𝑒 (mg/L) is the concentration of metal in solution, K F and 1/n are parameters of the Freundlich isotherm denoting a distribution coefficient (L/g) and intensity of adsorption, respectively. The Langmuir isotherm is the best known of all isotherms describing sorption and it has been successfully applied to many sorption processes. It describes reversible chemical equilibrium between identical surface adsorption sites and liquid-phase adsorbate concentration, which allows a monolayer of adsorbate at saturation (Hui et al. 2005). It has the advantage of providing a maximum adsorption capacity q max (mg/g) that can be correlated to adsorption properties. The model can be represented as: 𝐾𝐾𝐿𝐿 𝐶𝐶𝐶𝐶 q e = q max (3) 1+ 𝐾𝐾𝐿𝐿 𝐶𝐶𝐶𝐶 Where, q max (mg/g) and K L (L/g) are Langmuir constants representing maximum adsorption capacity and binding energy, respectively.

Permeability Test The permeability of OGFC and MOGFC specimen was determined according to Florida DOT Falling Head Laboratory Permeability Test Method (Kandal and Mallick 1999). An asphalt permeameter (150 mm) manufactured by Global Gilson with corresponding membranes (illustrated in Figure 3) were used in this study. Each specimen was wrapped securely with a thin

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plastic membrane to seal outsides of the specimen and only allow water to exit through the bottom surface when the specimen was fit snugly into the stand pipe. Petroleum jelly was applied onto the plastic wrapped specimen for lubrication before the specimen was inserted into the stand pipe. Asphalt binder coating was then applied around the top of each specimen to ensure that no water would drain around the outer edges of the specimen. The unit is then pressurized by the built-in hand pump to 100 kPa. Once the apparatus was secured, then the permeameter was filled with water to a height of 60 mm above the top of the specimen. The valve was opened and the time (t) required for the water to drop from the initial head, h 1 ꞊ 60 mm above the specimen to the final head, h 2 ꞊ 5 mm above the specimen was recorded and used to calculate the permeability using Eq. (4). The permeability (k) was measured three times on each specimen.

k꞊

𝑎𝑎𝑎𝑎 ℎ1 ln 𝐴𝐴𝐴𝐴 ℎ2

(4)

Where k ꞊ (m/day), Permeability a ꞊ Cross area of the stand pipe (m2), L ꞊ -sectional Thickness of the specimen (m), A ꞊ -sectional Cross area of the specimen (m2), t ,꞊and Time h 1, h 2 ꞊ water level in the stand pipe.

Fig. 3. Asphalt permeameter Metal Removal Experiment by MOGFC This test was conducted using the Florida DOT Falling Head Laboratory Permeability Test equipment (Figure 3). MOGFC specimen was placed inside the metal cylinder following the same procedures described in permeability test. The permeameter valve was adjusted to the appropriate level to allow 1000-mL metal solution pass through the MOGFC sample at a relatively constant rate while being timed. Approximately 1.5 hours were used for the whole filtration. The metal concentration of the filtrate was analyzed by AAS. Finally, the percentage metal removal was calculated by subtracting final concentration from the initial concentration using Eq. 5. % Metal Removal Efficiency =

(𝐶𝐶˳−𝐶𝐶𝑓𝑓 ) 𝐶𝐶˳

× 100

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(5)

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Air Void Measurement The bulk and maximum theoretical densities of test samples was determined in accordance to AASHTO T331 (Vacuum Sealing method) and AASHTO T209, respectively. These two tests were used to determine the total air void contents (AVt) in OGFC and MOGFC samples. Additionally, AASHTO T166 was conducted to determine the bulk specific gravity of OGFC samples, and meanwhile to determine the air voids that are not connected (AVnc). The approximate value of interconnected air voids (AVc) was then calculated by subtracting the AVnc from AVt. RESULTS AND DISCUSSIONS Adsorption Isotherm Adsorption of Cu by bentonite data were fitted to both Langmuir and Freundlich adsorption isotherm models as shown in Figure 4. The fitting parameters are listed in Table 4. The Langmuir (R2 ꞊ 0.96) isotherm exhibited a better fit compared to the Freundlich (R2 ꞊ 0.83) adsorption isotherm (Kubilay et al. 2007). The fact that Langmuir isotherm fits the experimental data very well indicates that almost complete monolayer coverage of the adsorbent particles (Eren and Afsin 2008). Value of “n” of Freundlich isotherm between 2 and 10 represents good adsorption (Erdem et al. 2004). The “n” value become 4.34 for Cu in Table 4 is an indication of good adsorption of Cu by bentonite. The Langmuir isotherm constants K L ꞊ 3.87 L/mg represent affinity of Cu to the binding sites on the bentonite and q max ꞊ 1.44 mg/g represent maximum adsorption capacity corresponding to complete the monolayer coverage.

Fig. 4. Cu (II) sorption data on bentonite fitted to Freundlich and Langmuir isotherm model (C 0 ꞊ 5 mg/L, Temperature 25°C)

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Zeolite adsorption capacity for Cu was determined using Langmuir and Freundich adsorption isotherm model (Figure 5). The calculated Langmuir and Freundlich constants are shown in Table 4. Both models showed good fit to the experimental data; however Langmuir (R2 ꞊ 0.96) model followed slightly better trend of the experimental data than Freundlich (R2 ꞊ 0.94) model (Motsi et al. 2009). The Langmuir constants q max ꞊ 10.63 mg/g and K L ꞊ 0.16 L/mg were obtained. The higher value of q max (10.63 mg/g) indicates higher adsorption capacity of zeolite for Cu than that of bentonite (1.44 mg/g). Hui et al. (2005) has also reported that, Cu adsorption by zeolite was well described by Langmuir model with q max ꞊ 53.45 mg/g. This numerical value of q max was higher than the results obtained by this study. The reason of high q max could be attributed to the use of high initial concentration (50 mg/L) in their study. The Freundlich ꞊ 1.23 isotherm constants K F ꞊ 1.39 L/mg represent Cu adsorption capacity of zeolite and n represent intensity of the adsorption on the bentonite surface. Table 4 Langmuir and freundlich isotherm parameters of Cu (II) adsorption by bentonite and zeolite Adsorbents Bentonite Zeolite

Langmuir Isotherm Constants q max (mg/g) K L (L/g) R2 1.44 3.87 0.96 10.63 0.16 0.96

Freundlich Isotherm Constants K F (L/mg) n R2 1.06 4.34 0.83 1.39 1.23 0.94

Fig. 5. Cu (II) sorption data on zeolite fitted to Freundlich and Langmuir isotherm model (C 0 ꞊ 5 mg/L, Temperature 25°C)

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The experimental data of Zn adsorption onto bentonite were regressively analyzed with Langmuir and Freundlich isotherm model (Figure 6). The relative constant values with regression coefficients calculated from the two models are listed in Table 5. It can be concluded from the constants that Freundlich (R2 ꞊ 0.98) model simulates the experimental data better than Langmuir (R2 ꞊ 0.91) model (Bereket et al. 1997). Zn adsorption onto bentonite gives “n” value of 2.78 (Table 5) indicated that this adsorption is a favored one (Baker and Khalili 2004). The other Freundlich constant K F indicates the adsorption capacity of the adsorbent. The Langmuir isotherm constants q max ꞊ 1.18 mg/g represent maximum adsorption capacity and K L ꞊ 1.63 L/mg represent affinity of Zn to the binding sites on the bentonite.

Fig. 6. Zn (II) sorption data on bentonite fitted to freundlich and langmuir isotherm model (C 0 ꞊ 5 mg/L, Temperature 25°C) Table 5 Langmuir and freundlich isotherm parameters for Zn (II) adsorption by bentonite and zeolite Adsorbents Bentonite Zeolite

Langmuir Isotherm Constants q max (mg/g) K L (L/g) R2 1.18 1.63 0.91 1.96 0.44 0.99

Freundlich Isotherm Constants K F (L/mg) N R2 0.66 2.78 0.98 0.58 1.75 0.99

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The Langmuir and Freundlich parameters for the adsorption of Zn onto zeolite are being listed in Table 5. R2 value, which is a measure of goodness-of-fit, exhibited that both the Langmuir (R2 ꞊ 0.99) and Freundlich (R2 ꞊ 0.99) models can adequately describe the adsorption data (Baker et al. 2009). The parameter, q max ꞊ 1.96 mg/g, which is related to the adsorption capacity, indicates that Zn adsorption capacity of zeolite is higher than that of bentonite (1.18 mg/g). On the other hand, in terms of favorability of adsorption, zeolite (n ꞊ 0.58) is less favorable than that of bentonite (n ꞊ 0.66) for Zn adsorption (Sheta et al. 2003).

Fig. 7. Zn (II) sorption data on zeolite fitted to freundlich and langmuir isotherm model (C 0 ꞊ 5 mg/L, Temperature 25°C) Cu and Zn adsorption capacities for each of the adsorbent are compared in Table 6. Bentonite and zeolite provided moderate to high adsorption capacities for both Cu and Zn. Therefore these two adsorbents were further tested for metal removal test of MOGFC. Table 6 Maximum Adsorption Capacities (q max ) of different adsorbents (C 0 ꞊ 5 mg/L and T ꞊ 25° C) Sl No

Adsorbent

Metal

q max (mg/g)

1

Bentonite

Zn

1.18

2

Bentonite

Cu

1.44

3

Zeolite

Zn

1.96

4

Zeolite

Cu

10.63

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Total Air Voids, Interconnected Air Voids, and Permeability of OGFC The total air voids and interconnected air voids were plotted in Figure 8. Normal trend of the plot showed that interconnected air voids increasing as total air void increased with a correlation coefficient of R2 ꞊ 0.89. However the range of interconnected air voids was smaller than total air voids, which was expected because interconnected air voids are a portion of total air voids and do not include the air voids that are not accessible by water. Similar trend has also been observed by other researchers (Alvarez et al. 2008; Kline and Putman 2011).

30

Interconnected Air Void (%)

27

y = 0.9481x - 7.2878 R² = 0.89

24 21 18 15 12 9 6 3 0 0

3

6

9

12 15 18 21 Total Air Void (%)

24

27

30

Fig. 8. Relationship of interconnected and total air voids of OGFC Permeability of each OGFC sample was measured and plotted as a function of total air voids and interconnected air voids in Figure 9. The data in the figure show that permeability increases as the interconnected and total air voids increase. Corresponding correlation coefficient of permeability, R2 were 0.86 and 0.82 respectively. The R2 value with interconnected air voids was slightly higher than the total air voids, which was because interconnected air voids are accessible by water. Mansour and Putman (2013) found similar increasing trend of permeability and air voids with higher value of R2 corresponds to interconnected air voids. In addition, for the same permeability value, the total air voids were 6 to 9 percent higher than the interconnected air voids, which was also similar to results reported by Wang et al. (2011).

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500 y = -2.1573x2 + 83.74x - 419.91 y = -1.544x2 + 92.433x - 969.76 R² = 0.82 R² = 0.86

Permeability (m/day)

450 400 350 300

Interconnected Air Voids

250

Total Air Voids

200 150 100 50 0

0

3

6

9 12 15 18 21 24 Total/Interconnected Air Voids (%)

27

30

Fig. 9. Correlation of permeability to interconnected and total air voids of OGFC Total Air Voids, Interconnected Air Voids, and Permeability of MOGFC MOGFC sample was prepared by adding different adsorbent dosage into the voids of OGFC samples. The total air voids, interconnected air voids, and permeability were measured following the procedure used for OGFC. The reason of this is to evaluate air void contents and permeability changes in MOGFC after adding different amount of adsorbents into it. The total air voids and interconnected air voids were plotted in Figure 10. Interconnected air voids increases as total air voids increase with a correlation coefficient of R2 ꞊ 0.41. Also, the range of interconnected air voids was smaller than total air voids. Comparing with interconnected and total air voids of OGFC plotted in Figure 8, interconnected and total air voids of MOGFC was reduced. This is because adding particles of adsorbent has decreased a substantial amount of air voids space in MOGFC. Wang et al. (2011) also reported similar result. It was observed that the correlation coefficient, R2 of MOGFC was slightly smaller than that of OGFC. One possible explanation is that, different dosages of adsorbent were introduced into MOGFC samples, therefore uniform reduction of air voids could not be observed.

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30

Interconnected Air Voids (%)

27

y = 0.575x - 3.9554 R² = 0.41

24 21 18 15 12 9 6 3 0

0

3

6

9

12 15 18 21 Total Air Voids (%)

24

27

30

Fig. 10. Relationship of interconnected and total air voids of MOGFC

Permeability of MOGFC sample was measured and plotted as a function of total air voids and interconnected air voids in Figure 11. Permeability increases as interconnected and total air voids increase. Corresponding correlation coefficient of permeability, R2 was 0.25 and 0.22 respectively. These two R2 values with MOGFC were much lower than that of OGFC. For the same permeability value of MOGFC, total air void differs by 10 to 12 percent from interconnected air void, which was higher than OGFC and coefficient of permeability with interconnected air voids was still somewhat higher than total air voids.

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500 450 y = 163.07ln(x) - 96.854 R² = 0.25

Permeability (m/day)

400

y = 367.59ln(x) - 861.54 R² = 0.22

350 300 250 200 150

Interconnected Air Voids

100

Total Air Voids Acceptable Level (100 m/day)

50 0

0

3

6

9

12

15

18

21

24

27

30

Total/Interconnected Air Voids (%)

Fig. 11. Correlation of permeability to interconnected and total air voids of MOGFC The average rate of permeability of MOGFC was calculated as 214 m/day from Figure 11, which was smaller than OGFC (248 m/day) from Figure 9. The lower rate of permeability value was expected as the water flows are interrupted by the adsorbent particles in the voids of MOGFC. However the lower rate of permeability in MOGFC is still above the minimum permissible value, 100 m/day (Mallick et al. 2000). This indicates that, despite having a reduced air void content, the MOGFC still has good water removal capacity to avoid accumulation of highway runoff on the road surface.

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Metal Removal Efficiency of MOGFC Cu and Zn removal efficiencies of MOGFC with different bentonite dosages were plotted in Figures 12 and 13, respectively. MOGFC included maximum 0.70% bentonite in the sample. It is clear from both the figures that, conventional OGFC, without any bentonite dosage, did not show any significant removal either for Cu or Zn. However after introducing bentonite, Cu and Zn removal efficiencies were significantly improved. The maximum removal efficiency of bentonite for Cu is 76.3% which is greater than the removal efficiency for Zn at 41.8%. This suggested that MOGFC with bentonite could adsorb more Cu than Zn. These findings agreed well with the batch adsorption study results. 100 90 80 70 60 50 40 30 20 10 0

Zn Removal Efficiency (%)

Cu Removal Efficiency (%)

100 90 80 70 60 50 40 30 20 10 0

0.00

0.25

0.40

0.55

0.70

Bentonite Dosage (%)

Fig. 12. Cu removal efficiency of the MOGFC with bentonite added (C0 ꞊ 1 mg/L, V ꞊ 1 L)

0.00

0.25

0.40

0.55

Bentonite Dosage (%)

0.70

Fig. 13 Zn removal efficiency of the MOGFC with bentonite added (C0 ꞊ 1 mg/L, V ꞊ 1 L)

MOGFC with different zeolite dosages was tested for Cu and Zn removal efficiency and data were plotted in Figures 14 and 15, respectively. MOGFC permitted maximum 0.30% zeolite inclusion into its voids. This value was lower than that of bentonite. The reason for this was because of the larger particle size of zeolite than bentonite, which preventing from adding more zeolite into the voids. The maximum removal efficiency of zeolite for Cu is 73.7% which is greater than the removal efficiency of zeolite for Zn at 43.7%. This specified that MOGFC with zeolite could adsorb more Cu than Zn. These findings agreed well with the batch adsorption study results.

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Zn Removal Efficiency (%)

Cu Removal Efficiency (%)

100 90 80 70 60 50 40 30 20 10 0

0.00

0.08

0.15

0.20

Zeolite Dosage (%)

0.30

100 90 80 70 60 50 40 30 20 10 0

0.00

0.08

0.15

0.20

Zeolite Dosage (%)

Fig. 14. Cu removal efficiency of the MOGFC with zeolite added (C0 ꞊ 1 mg/L, V ꞊ 1 L)

0.30

Fig. 15. Zn removal efficiency of the MOGFC with zeolite added (C0 ꞊ 1 mg/L, V ꞊ 1 L)

Two different adsorbents (bentonite and zeolite) were added separately with MOGFC to get competitive removal efficiency for Cu and Zn. Maximum removal efficiencies were listed in Table 7. Bentonite, and Zeolite showed the removal efficiency of 76.3%, and 73.7% for Cu and 41.8% and 43.7% for Zn respectively. It is clear that, each adsorbent has its higher removal efficiency with Cu in comparing with Zn which agreed well with the batch adsorption capacity data. According to batch adsorption study, more Cu was adsorbed by zeolite but during MOGFC metal removal study bentonite has high removal efficiency for Cu. This might be caused by the lower dosage of zeolite in MOGFC and greater contact time during batch adsorption study. Table 7 Metal Removal Efficiency Parameters for MOGFC Adsorbent

Metal

Initial Concentration (C 0 )

Maximum Dosage (%)

Maximum Efficiency (%)

Adsorption Capacity (mg/g)

Bentonite

Cu

1.0

0.70

76.3

0.04

Zeolite

Cu

1.0

0.30

73.7

0.03

Zeolite

Zn

1.0

0.30

43.7

0.02

Bentonite

Zn

1.0

0.70

41.8

0.02

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CONCLUSIONS In this study, low cost and high adsorption capacity adsorbents were identified. Open Graded Friction Course (OGFC) was produced with PAC-40 and lime stone aggregate. Adsorbents were added into OGFC to develop MOGFC. Both OGFC and MOGFC samples were characterized and differentiated by permeability and air void measurement tests. After that, application of MOGFC to heavy metal removal was investigated. Based on the analysis of test results following conclusions are summarized: • • • •

Air void and permeability test confirmed that MOGFC has good water removal capacity to avoid accumulation of highway runoff on the road surface. Bentonite and zeolite possessed significant metal adsorption capacity for Cu and Zn. MOGFC metal removal efficiency test showed evidence that with the increase of adsorbent dosage metal removal efficiency was increased. Bentonite and zeolite had their highest MOGFC metal removal efficiencies and highest adsorption capacities with Cu. Therefore MOGFC developed using such adsorbents hold great potential of Cu removal from the highway storm water runoff.

The developed MOGFC can remove the heavy metals from the highway storm water runoff. The proposed in situ treatment technique based on MOGFC will have both environmental and economic benefits, as it is inexpensive and eliminates the need for external treatment facilities for highway runoff. Thus it has the potential to save on land usage and costs over traditional treatment methods such as wetlands and detention ponds. REFERENCES Alvarez, A. E.; Epps Martin, A.; Estakhri, C.; Izzo, R. (2008). Determination of volumetric properties for permeable friction course mixtures. J. Test. Eval., 37(1), 1–10. ASTM. (2004). Standard practice for open-graded friction course (OGFC) mix design. ASTM D7064, West Conshohocken, PA. Baker, H. and Khalili, F. (2004). Analysis of the removal of lead (II) from aqueous solutions by adsorption onto insolubilized humic acid: temperature and pH dependence. Analytica Chimica. Acta., 516 (1), 179-186. Baker, H. M.; Massadeh, A. M.; Younes, H. A. (2009). Natural jordanian zeolite: removal of heavy metal ions from water samples using column and batch methods. Environ. Monit. Assess., 157, 319–330. Barrett, M. E. (2008). Effects of a permeable friction course on highway runoff. J. Irrig. Drain. Eng., 134(5), 646–651. Barrett, M. E.; Irish, L. B.; Lesso, W. G.; Malina, J. F.; Charbeneau, R. J.; Ward, G. H. (1995b). An evaluation of the factors affecting the quality of highway runoff in the austin, texas area. Technical Report, CRWR 264, Center for research in water resources. Austin, Texas 78712. Barrett, M. E.; Zuber, R. D.; Collins, E. R.; Malina, J. F. Jr.; Charbeneau, R. J.; Ward, G. H. (1995a). A review and evaluation of literature pertaining to the quantity and control of

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pollution from highway runoff and construction. Center for Research in Water Resources CRWR 239, Bureau of Engineering Research, Austin, TX. Bereket, G.; Aroguz, A. Z.; Ozel, M. Z. (1997). Removal of Pb (II), Cd (II), Cu (II) and Zn (II) from aqueous solutions by adsorption on bentonite. J. Colloid. Interf. Sci. 187, 338–343. Cooley Allen, L. Jr.; Brumfield, J. W.; Mallick, R. B.; Mogawer, W. S.; Partl, M., Poulikakos, L.; Hicks, G. (2009). Construction and maintenance practices for permeable friction courses. NCHRP Rep. No. 640, TRB, National Research Council, Washington, DC. EPA. (1993). Guidance specifying management measures for sources of nonpoint pollution in coastal waters. EPA 840-B-92-002. Office of Water, Washington, DC: US Environmental Protection Agency. EPA. (2006). Roadway and bridge maintenance fact sheet. National Pollutant Discharge Elimination System (NPDES). Erdem, E.; Karapinar, N.; Donat, R. (2004). The removal of heavy metal cations by natural zeolites. J. Colloid Interf. Sci., 280, 309–314. Eren, E.; Afsin, B. (2008). An investigation of Cu (II) adsorption by raw and acid-activated bentonite: A combined potentiometric, thermodynamic, XRD, IR, DTA study. J. Hazard Mater., 151, 682–691. Falahi-Ardakani, A. (1984). Contamination of environment with heavy metals emitted from automotives. Ecotox. Environ. Safe., 8, 152–161. Hoffman, E. J.; Latimer, J. S.; Hunt, C. D.; Mills, G. L.; Quinn, J. G. (1985). Stormwater runoff from highways. Water Air Soil Poll., 25, 349–364. Huber, G. (2000). Performance survey on open-graded friction course mixes. NCHRP Synthesis of Highway Practice 284, TRB, National Research Council, Washington, DC. Hui, K. S.; Chao, C. Y. H.; Kot, S. C. (2005). Removal of mixed heavy metal ions in wastewater by zeolite 4A and residual products from recycled coal fly ash. J. Hazard Mater., 127(1–3), 89–101. Kandhal, P. S.; Mallick, R. B. (1999). Design of new-generation open-graded friction course. NCAT Report, 99–03. Kandhal, P. (2002). Design, construction, and maintenance of open-graded asphalt friction courses. Information Series 115, National Asphalt Pavement Association, Lanham, MD. Kline, L. C.; Putman, B. J. (2011). Comparison of open graded friction course (OGFC) mix design procedures in the united states. 90th Annual Meeting of the Transportation Research Board, Transportation Research Board of the National Academies, Washington, DC. Kubilay, S.; Gurkan, R.; Savran, A.; Sahan, T. (2007). Removal of Cu (II), Zn (II) and Co (II) ions from aqueous solutions by adsorption onto natural bentonite. Adsorption, 13, 41– 51. Maestri, B.; Lord, B. N. (1987). Guide for mitigation of highway stormwater runoff pollution. Sci. Total Environ., 59, 467–476. Mallick, R. B.; Kandhal, P. S.; Cooley, L. A.; Watson, D. E. (2000). Design, construction, and performance of new-generation open-graded friction courses. J. Assoc. Asphalt Paving Technol., 69, 391–423. Mansour. T. N.; Putman, B. J. (2013). Influence of aggregate gradation on the Performance properties of porous asphalt mixtures. J. Mater. Civ. Eng., 25(2), 281–288.

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Motsi, T.; Rowson, N. A.; Simmons, M. J. H. (2009). Adsorption of heavy metals from acid mine drainage by natural zeolite. Int. J. Miner. Process. 92, 42–48. NCHRP. (2009). Construction and maintenance practices for permeable friction courses. Rep. 640, Transportation Research Board, Washington, DC. Pagotto, C.; Legret, M.; Le Cloirec, P. (2000). Comparison of the hydraulic behavior and the quality of highway runoff water according to the type of pavement. Water Environ. Res., 34(18), 4446–4454. Rungruangvirojn, P.; Kanitpong, K. (2010). Measurement of visibility loss due to splash and spray: porous, SMA and conventional asphalt pavements. Int. J. Pavement Eng., 11(6), 499–510. Shaheen, D. G. (1975). Contributions of urban roadway usage to water pollution. Environmental Protection Agency Report, EPA, 600/2–75–004. Sheta, A. S.; Falatah, A. M.; Al-Sewailem, M. S.; Khaled, E. M.; Sallam A. S. H. (2003). Sorption characteristics of zinc and iron by natural zeolite and bentonite. Micropor. Mesopor. Mat., 61, 127–136. Stotz, G.; Krauth, K. (1994). The pollution of effluents from pervious pavements of an experimental highway section. Sci. Total Environ., 146–147, 465–470. Tappeiner, W. (1993). Open-graded asphalt friction course. Information series 115, National Asphalt Pavement Association, Lanham, MD. United States Environmental Protection Agency (1993). Urban runoff pollution prevention and control planning. EPA/625/R-93/004, Office of Research and Development, Cincinnati, OH. Wang, L.; Rizvi, H.; Khattak, M.; Gang, D. (2011). Development and evaluation of functional open graded friction courses (FOGFC) mixtures for in situ highway runoff treatment. Proceedings on Geo-Frontiers 2011, 4573–4583, Dallas, TX. Warren, R.; Birch, P. (1987). Heavy metal levels in atmospheric particulates, roadside dust and soil along a major urban highway. Sci. Total Environ., 59, 253–256. Wu, J.; Allan, C.; Saunders, W.; Evett, J. (1998). Characterization and pollutant loading estimation for highway runoff. J. Env. Eng., 124 (7), 584–592.

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