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Development of Iron-Oxide-Coated Fiberglass for Arsenic (V) removal Arun Kumar, Graduate Research Assistant, Department of Civil, Architectural and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, U.S.A.;
[email protected] Patrick L. Gurian, Assistant Professor, Department of Civil, Architectural and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, U.S.A.;
[email protected] Robin H. Bucciarelli-Tieger, Undergraduate Research Assistant, Department of Civil, Architectural and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, U.S.A.;
[email protected]
ABSTRACT Iron-oxide-coated fiberglass (IOCFG hereafter) was developed and evaluated for arsenate removal effectiveness. Different fiberglass types (cloth, mat and fibers) were coated with iron oxide using different combinations of temperature (250C and 1100C), pH (1.3, 7 and 8.5) and initial iron concentrations (0.25M and 2.5M) following the adsorption method. Iron loadings of 11-34 mg Fe g-1 was obtained on fiberglass at room temperature, which could be attributed to its surface properties (surface area and silanol functional groups). Fiberglass insulation fibers were selected based on their higher iron retention ability as compared to other fiberglass types. An iron loading of 231 mg g-1 was obtained on fiberglass insulation fibers (pH 1.3, 1100C), which is ~ 5 times higher than maximum reported iron loading on sand. Comparison of iron loading on fiberglass fibers and sand indicated that ~ 13 times lower initial iron concentration was required to achieve 45 mg g-1 iron loading on fiberglass fibers as compared to sand. 10g L-1 iron-oxidecoated fiberglass insulation fibers (IOCFGI) with an iron loading of 231 mg Fe g-1, developed at coating conditions (pH 1.3, 0.25M Feinitial, 1100C), were contacted with synthetic ground water (Well # 303, El Paso) containing 100 μg L-1 arsenate. Experiments were conducted for 12h, 24h and 48h at pH 7.6 and 250C. More than 90 % arsenate removal was achieved within 12 h of the sorption experiment by IOCFGI (0.01 mg arsenate g-1 IOCFGI), which could be attributed to the iron oxide loading on fiberglass. This is the first study illustrating the application of fiberglass for the development of iron-oxide based fibrous sorbents and its applicability in removing metals like arsenic for treating drinking water and wastewater. Keywords: Arsenic, Iron oxide coating, Adsorption, Fiberglass, Fibers
INTRODUCTION Iron-oxide-coated-sorbents (IOCS) have been demonstrated to remove oxyanions, such as arsenate [1-3], and cations, such as copper and lead [3, 4], and natural organic matter [4] from both drinking water and industrial wastewater. Different raw materials such as sand [1], zeolites [5], activated carbon [5], resin [6], ion exchangers [7], and cellulose [8-9] have been used as substrates for the iron-oxide coating. Higher iron loadings can be achieved with materials that have a high specific surface area and surface functional groups such as silanol, hydroxyl,
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carboxyl, ammonium, etc. capable of binding iron. Besides material properties, coating pH, temperature, and initial iron concentration governs the extent and phase of the iron oxide coating [10]. Fibers may be promising materials for use as a matrix for iron oxide coating because they provide very high specific surface area (m2/m3) compared to typical granular materials, such as sand, due to their small diameters ranging from micrometer to nanometer range. Gurian et al. [11] reported the possibility of iron oxide loading on fibers. Fiberglass (FG hereafter) provides ~30 times higher specific surface area and possesses silanol surface functional groups [12], known for retaining iron oxide coatings [13-14]. While silica is a primary component of FG, it has not been explored for its ability to retain iron oxide coating. In addition, FG is a relatively inexpensive raw material, which makes it a promising material for developing IOCS for single use applications. In summary, FG appears to be a low-cost material with desired characteristics for a raw material for developing IOCS. The objective of the present research was to evaluate the feasibility of iron oxide coating on FG. To test this, FG was coated with iron oxide and the effectiveness of alternative coating processes was evaluated based on iron retention capacity (mg Fe g-1 media). Further, iron-oxide coated fiberglass (IOCFG hereafter) was tested for its capacity for arsenate removal.
MATERIALS AND METHODS Materials All chemicals used were of analytical reagent grade and milli-Q water was used in the preparation of standard and diluted solutions. All glassware and polyethylene bottles were soaked with 10% nitric acid for 12 hr and rinsed with milli-Q water. Fiberglass mat (FG mat) was purchased from Jamestown Distributors (http://www.jamestowndistributors.com). Fiberglass insulation (FGI) and Fiberglass cloth (FGC) 1 were purchased from Ace Hardware. Iron chloride solution was prepared using iron chloride (FeCl3, 98%, VWR International). Arsenate stock solution was prepared using sodium arsenate (Na2HAsO4.7H2O, Sigma-Aldrich) and diluted appropriately to prepare solutions with lower arsenate concentrations. 10% HCl and 10M NaOH were used for pH adjustment. Synthetic groundwater containing 100 μg L-1 arsenate concentration was prepared by simulating the water quality characteristics of the El Paso Water Utilities’ Well # 303 (pH:7.6, Fe
