Bryan E. Kepnerâ , John Spotsâ , Eric A. Mintzâ¡, Jeffrey, E. Cortopassiâ¡, ... Chemistry, Clark Atlanta University, 223 James P. Brawley Dr. S. W., Atlanta, GA 30314 ...
REMOVAL OF ARSENIC FROM DRINKING WATER WITH ENHANCED HYBRID ALUMINAS AND COMPOSITE METAL OXIDE PARTICLES Bryan E. Kepner†, John Spots†, Eric A. Mintz‡, Jeffrey, E. Cortopassi‡, Paul Abrahams‡, Carlton E. Gray‡, Santosh Matur* †
Apyron Technologies, Inc., 4030-F Pleasantdale Rd., Atlanta Georgia, 30340, U.S.A.; Department of Chemistry, Clark Atlanta University, 223 James P. Brawley Dr. S. W., Atlanta, GA 30314, U.S.A.; *RPM Marketing Pvt. Ltd., C-23 Friends Colony, New Delhi 110065 India. INTRODUCTION Arsenic contamination of drinking water is a world-wide problem which has hit the West Bengal region of India particularly hard.1 Long term exposure to arsenic via drinking water leads to a wide range of health problems including: skin cancer, gangrene of the limbs, vascular diseases, conjunctivitis, central nervous system damage and hyperkeratosis.2 Methods such as coagulation3 and reverse osmosis4 have been shown to be effective for the removal of arsenic from water. However, these methods require considerable infrastructure and are expensive to operate, thus making them impractical for small community scale water treatment systems. As a large number of people in West Bengal obtain their water from small wells, as opposed to from large municipal water plants, it is necessary to develop technology that can be implemented on a small scale to remove arsenic from drinking water as it is extracted from the well. Several investigators have reported adsorption methods for the removal of arsenic from drinking water5, however there is still a need to develop effective field deployable adsorbents and delivery systems. We have developed enhanced hybrid aluminas and alumina-metal oxide composite particles that have proven effective for the removal of arsenic from water.
METHODOLOGY Enhanced hybrid aluminas (EHAs) were prepared by heating beohmite to 400o C for 1 hr followed by treatment with 0.5 % acetic acid for 15 min (PBHK). [need data on AQA]. The alumina samples were then dried but not calcined.6 Alumina-metal oxide composite particles (Al-MOC) were prepared by binding EHAs and metal oxides utilizing a proprietary colloidal alumina binder system.7 Head to head comparison of the different media for the removal of arsenic from water was carried out. Approximately one gram samples of enhanced hybrid alumina or alumina-metal oxide composite particle were tumbled with 495 mL of 50 ppm arsenic solutions (a large excess of arsenic) for 24 hours. The solutions were filtered and subjected to inductively coupled plasma/mass spectroscopy (ICP/MS) to determine the arsenic concentration. The arsenic solutions were prepared by dissolving AsO3 in 1-4 % nitric acid. The results of these experiments are given in Table 1. The removal of arsenic as a function of pH was examined for an enhanced hybrid alumina (PBHK), an alumina-alumina composite particle (82AHC), an alumina-manganese oxide composite particle (1F97SLIN), and an alumina-iron oxide composite particles 2F97SLIN. In a manner similar to that above approximately one gram samples of EHA or alumina-metal oxide particle were tumbled with 495 mL of 50 ppm arsenic solutions (a large excess of arsenic) which had been adjusted to approximately pH 4.2, 7, 9, 11 or 13.3, to allow head to head comparison of the different media for the removal of arsenic from water as a function of pH. The arsenic solutions were prepared by dissolving AsO3 in 1-4 % nitric acid followed by pH adjustment with NaOH. The results are shown in Figure 1. At very low pH 1F97SLIN partially dissolves, and reacts with the arsenic, leading to an anomalous high adsorption result. At very high pH the alumina partially dissolves, and reacts with the arsenic, leading to an anomalous high adsorption result. In the drinking water pH range all four of these adsorbents exhibit good arsenic removal when no other contaminants are present. 1
Table 1: Head-to-Head Comparisons of Selected Enhanced Hybrid Aluminas and Alumina-Metal Oxide Composite Particles For the Adsorption of Arsenic Sample AQA
g’s sorbent 1.026
[As]i (ppm) 50
[As]f (ppm) 38
Volume As absorbed % absorbed (mL) (g/kg) 495 5.79 24.0
Particle Enhanced Hybrid Alumina (see text) Base washed AQA Enhanced Hybrid Alumina (see text) Alumina/Alumina Alumina/Manganese Oxide Alumina/Iron Oxide Alumina/Iron Oxide/Manganese Oxide Alumina/Manganese Oxide Alumina/Manganese Oxide
[As]i = initial arsenic concentration ppm (mg/L). [As]f = final arsenic concentration ppm (mg/L).
Figure 1: Removal of Arsenic (Grams Arsenic/Kg Media) as Vs. pH 25
As the alumina manganese oxide composite particle proved most effective for arsenic removal at pH 7 we further examined the effect of varying the manganese content of the composite on the arsenic removal capacity. Figure II indicates that increasing the manganese oxide composition above 10 % in the alumina-manganese oxide composite particle does not increase the arsenic removal capacity of the composite particle. 2
Effect Of Manganese Oxide Composition On The Arsenic Uptake Capacity Of Alumina/Manganese Oxide Composite Particles. Grams Arsenic/Kg Media
25 20 15 10 5 0 0
% Maganese Oxide
Water samples were obtained from the Santipur Water Supply (Zone II) at Phatakapra in the Nadira District in West Bengal and analyzed by ICP-MS to determine the contaminants in the water. Column 1 in Table II lists the concentrations of ions found with a concentration of greater than 1 ppb. Based upon the composition of the water obtained from the Santipur water supply, water samples were prepared that were spiked with Na+, Mg++, Ca++, Fe++, Cu++, Zn++, Cd++ and Pb++ in addition to arsenic and the pH adjusted to 8.0. An enhanced hybrid alumina (PBHK) and an alumina-manganese oxide composite particle (1F97SLIN) were tested against these “synthetic” water samples. The PBHK was found to be less effective than 1F97SLIN in the presence of high concentrations of Na+, Mg++, and Ca++ for the removal of arsenic. Further experiments have established that the alumina-manganese oxide composites are “self protecting” from the high concentration of Mg++, and Ca++ ions. Many adsorbents that remove arsenic from otherwise pure water in the laboratory have not fared well in the field because of the competition of Mg++ and Ca++ and other naturally occurring ions for adsorbent sites that would otherwise be available for arsenic. A water sample from the Santipur water supply was then treated in a small column test with 1F97SLIN. The concentration of contaminants in the 15Th bed volume of this test are give columns 2 of Table II. This and other tests indicate that 1F97SLIN is effective for the removal of arsenic in typical well water which is high in Mg++ and Ca++ and other naturally occurring ions. Column 2 in Table II also indicates that the 1F97SLIN is effective for the removal of other harmful metals, such as cadmium, antimony, lead and uranium, from the well water. A prototype unit for the removal of arsenic from well water is shown in figure II. Figure III gives the internal details of this unit. A field test is currently in progress in Phatakapra in the Nadira District in West Bengal to further test the efficacy of alumina-manganese oxide composites for the removal of arsenic from well water on site. Table III gives the initial results of this field test.
Table II: Well Water Before and After Treatment With 1F97SLIN. Column
Element Li B Na Mg Ca Fe Cu Zn Ga Ge As Cd Sb Ba Pb U pH
1 2 Untreated Well Water 1F97SLIN Treated Well Water ppb ppb 7.01 2.48 22.16 3.88 18650 >1513 48440 8817 7981000 522700 1495 11.62 177 0.00 50.48 0.00 0.02 0.02 33.29 0.02 176.5 0.00 1.27 0.13 47.56 0.26 7.93 0.01 2.18 0.00 1.13 0.01 7.7 7.70
Figure II: Prototype Unit For The Removal Of Arsenic From Well Water
Hand Pump Clamp
Blue Flex Hose
Apyron Arsenic Removal System
System engineered for a maximum flow rate of 2 gal/min. (7.6 L/min)
Figure III: Internal Details Of Prototype Field Unit.
FLEX LINE (Attach to hand pump)
DISTRIBUTION DISK DIFFUSER SCREEN
Arrows Indicate Flow
OUTER CONTAINER 5
ACKNOWLEDGMENT The Georgia Research Alliance for the acquisition of the Perkin-Elmer Elan 5000 ICP-MS System used for the arsenic analysis for this project.
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