Arsenic Removal Technologies
Amended Silicates, LLC are a new class of sorbents being developed by ADA Technologies for capture of metals. In their arsenic-binding form, the Amended Silicates™ feature a low-cost substrate impregnated with proprietary iron oxide active species. ADA and partners Texas A&M University, CH2M Hill, and Kinetico Incorporated are developing and testing granular forms of the sorbent that are suited for use in drinking water. These sorbents remove both As(III) and As(V) compounds. Isotherm tests demonstrated the sorbents could remove arsenic from 1000 ppb to below 10 ppb.
The Amended Silicates™ are projected to be comparable in price to iron-amended activated alumina sorbents, but with higher capacity and less sensitivity to pH. The new sorbent is expected to cost less than other iron-based arsenic sorbents such as Granular Ferric Hydroxide (GFH) and Bayoxide E33™. Isotherm testing indicates that the Amended Silicates have higher capacity at typical arsenic concentrations versus GFH. In summary, the new class of sorbents developed by ADA offers several advantages, namely:
- Low cost: the ADA sorbents are expected to cost $1-$2 per pound.
- High arsenic-removal rate: ADA sorbents have the capability of reducing arsenic levels in water below 10 ppb with a concomitantly high capacity for arsenic.
- Excellent performance over a wide pH range (tested from 6.5 to 8.5)
- Excellent performance in the presence of common anions and cations, e.g. sulfate
- Ability to capture As(III) and As(V) species
- Strengthened granular forms provide excellent flowability and hydrodynamic properties
- Low-density forms available for fluidized systems
- Ability to chemically bind arsenic: the ADA sorbents react with the arsenic to produce a leach-resistant waste sorbent material, providing an opportunity for direct disposal as an alternative to regeneration.
ADA has also teamed with staff at Virginia Tech University and Old Dominion University to study the fundamentals of the interaction between arsenic species and the iron oxide-based media.
Online Arsenate Sensor. ADA and partnering subcontractors are developing low-cost approaches for quantifying the concentration of arsenic in drinking water. In one approach, ADA uses proprietary chemicals to convert arsenic species into a form which creates a colored indicator. Encapsulated reagents make this test kit simpler than other methods. The user need only add a water sample, seal the vial, and compare the colored cap to a standard color chart.
ADA and its team members are also investigating methods suitable for use as online arsenic sensors. The goal is to produce an affordable, reliable means of determining the status of arsenic sorbent media so that the sorbents can be utilized to their full extent, without relying on simple calendar-based exchange schedules.
Field Testing. Under funding from the EPA and US Air Force, the ADA team is demonstrating the effectiveness of iron-based media in small-scale field tests. The EPA-funded work has focused on point-of-use systems, with testing at two sites in southern Colorado.
ADA and team member Kinetico Incorporated will run a packed column test of the Amended Silicate™ and two other sorbent media in southern California during 2005. This work, funded by the US Air Force, is designed to demonstrate the greater effectiveness of the newer iron-based adsorbent media versus other arsenic adsorbents.
For more information contact: Craig S. Turchi, PhD, Sr. Research Engineer
303-874-8285
Or
Nick Knowlton
303-874-7377
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