Grantee Research Project Results
Final Report: A Microengineered Adsorbent for Arsenic Removal for Small Drinking Water Treatment Facilities
EPA Contract Number: 68D02031Title: A Microengineered Adsorbent for Arsenic Removal for Small Drinking Water Treatment Facilities
Investigators: Liu, Paul K.T.
Small Business: Media and Process Technology Inc.
EPA Contact: Richards, April
Phase: I
Project Period: April 1, 2002 through September 1, 2002
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text | Recipients Lists
Research Category: Watersheds , SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
Summary/Accomplishments (Outputs/Outcomes):
The adsorption capacities for As [V] by the proposed adsorbent are extremely high. Under standards condition (i.e., distilled water at pH = 7), the adsorbent delivers 7-12 mg As[V]/g adsorbent at 10 ppb As[V], and 12-37 mg As[V]/g at 100 ppb As[V], depending on the composition of the adsorbent. These capacities are much higher than the capacities exhibited by the leading commercial product, ferric hydroxide, under the same conditions. The proposed adsorbent strongly favors As[V] over other ions such as silicate, phosphate, sulfate, chloride, etc. The only major ion known to have an effect is the carbonate ion. However, a maximum capacity reduction of only 33 percent was observed, which is relatively modest and does not significantly impact the economics due to its extremely high capacity. In comparison, ferric hydroxide is highly susceptible to competition from silicate ions, according to the literature. Virtually no pH effect on the adsorption of As[V] with Media and Process Technology, Inc.'s adsorbent was observed. The existing leading commercial product, ferric hydroxide, with its point of zero charge value of 8.6, as expected, loses most of its capacity for As[V] at pH greater than 7. This is a critical Achilles' heel of ferric hydroxide.
For the adsorption of As[III], 5 and 1 mg As[III]/g adsorbent were obtained at 100 and 10 ppb As[III], respectively, with Media and Process Technology, Inc.'s adsorbent. These capacities are comparable to (or better than) those obtained from the leading commercial product, ferric hydroxide. However, the adsorbent is not susceptible to the competition by sulfate, phosphate, chloride, and silicate ions. Carbonate is the only ion known that shows a significant effect; the maximum reduction is estimated to be approximately 35 percent. In comparison, As[III] adsorption on ferric hydroxide is highly susceptible to silicate and carbonate ion competition. The maximum reduction by silicate can reach 60 percent. An adsorption column study was performed that validates the advantage of this adsorbent with regard to the competition effect by ions present in a synthetic water (NSF STD 53) spiked with 50 ppb As[III].
However, these types of adsorbents are rarely used commercially for aqueous-phase applications due primarily to its availability in the powder form (plate, ~2-5 µm range) only. This powered adsorbent causes significant operation inconvenience or difficulties for the proposed use. During the Phase I study, a unique forming technique was developed that can avoid the technical challenges associated with the forming of the powder. Media and Process Technology, Inc., experimentally demonstrated that adsorbent forming is best achieved through this technique.
Conclusions:
During Phase I, Media and Process Technology, Inc., demonstrated the technical feasibility of this proposed product based on a side-by-side comparison of their proposed adsorbent versus an existing commercial product. In addition, the powder adsorbent was developed into a formed product via an innovative, simple, and low-cost approach. The cost of the formed adsorbent is within the competitive range of existing commercial products, and has superior performance.
Supplemental Keywords:
arsenic, adsorption, drinking water treatment, ferric hydroxide, silicate, phosphate, sulfate, chloride, carbonate, powder, SBIR., RFA, Scientific Discipline, Water, Health Risk Assessment, Environmental Chemistry, Chemistry, Arsenic, Drinking Water, Engineering, Chemistry, & Physics, Safe Drinking Water, microengineered adsopbent, human health effects, drinking water treatment facilities, detection, exposure and effects, adsorbents, microengineered adsorbent, exposure, risk management, arsenic removal, community water system, treatment, arsenic exposure, drinking water contaminants, water treatment, drinking water systemThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.