Grantee Research Project Results
Final Report: Development and Characterization of a New Heavy-Metal Selective Inorganic Ion Exchanger
EPA Grant Number: R825422Title: Development and Characterization of a New Heavy-Metal Selective Inorganic Ion Exchanger
Investigators: Sengupta, Arup K. , Kney, Arthur D. , Leun, David , Greenleaf, John , DeMarco, Matthew
Institution: Lehigh University
EPA Project Officer: Aja, Hayley
Project Period: November 1, 1996 through October 31, 1998 (Extended to December 31, 2000)
Project Amount: $218,643
RFA: Exploratory Research - Water Engineering (1996) RFA Text | Recipients Lists
Research Category: Water , Safer Chemicals , Land and Waste Management
Objective:
The need for a selective yet cost-effective heavy-metal sorbent is well recognized in view of the nation's diverse heavy-metal-contamination problems pertaining to groundwater, landfill leachates, acid mine drainage and industrial wastewaters. During the last three decades, a tremendous growth took place in the area of syntheses and applications of polymeric chelating exchangers leading to their commercialization for removals of heavy metals and other contaminants. These chelating exchangers are, however, quite expensive and generally cost over $20.00 per pound in the United States and other industrialized nations such as Germany and Japan. Chelating exchangers have been found viable in many specialty applications, but their high cost has been a major obstacle to more frequent usage in environmental pollution control and pollution prevention.It is generally agreed amongst scientists and engineers that an inorganic ion exchanger is likely to be a viable alternative to polymeric chelating exchangers provided its durability, morphology and heavy metal selectivity can be improved through innovative process modifications. It is even better if such a selective inorganic exchanger can be synthesized using raw materials that are abundantly available and environmentally benign. To this effect, both amorphous and crystalline forms of iron oxyhydroxides, commonly referred to as ferrihydrites, have long been known to exhibit high sorption affinities toward heavy metal cations and toxic metalloids like dissolved arsenic species. The current process of ferrihydrite syntheses, although straightforward, produces only very fine particles (in microns), which are not usable in fixed-bed systems because of excessive pressure drop in the columns.
The general objective of the project was to prepare, characterize, and evaluate the performances of a new class of inorganic and hybrid (polymeric/inorganic) sorbent materials pertaining to dissolved heavy metals removal.
The specific objectives of the project were to: (1) synthesize granular inorganic ion exchanger particles which can be used in fixed-bed columns to remove dissolved heavy metals; (2) benchmark the performance of this new ion exchanger in comparison with other commercially available chelating exchangers; (3) elucidate the underlying sorption mechanism responsible for high heavy-metal-ion affinity; (4) prepare/synthesize hybrid (polymeric/inorganic) particles for arsenic removal in a fixed-bed column; (5) explore the possibility of imparting magnetic activity onto polymeric or hybrid sorbent particles; and (6) investigate intraparticle diffusion of solutes for particles of varying porosity.
While the first three goals were explicit in our original proposal, the latter three evolved during the course of our investigation.
Summary/Accomplishments (Outputs/Outcomes):
Inorganic Heavy-Metal-Selective Sorbent. Heavy-Metal-Selective inorganic granular particles were synthesized in this project using oxides of iron, silicon, calcium and magnesium. An operationally simple high temperature thermal process was developed for synthesis of hybrid particles which were found compatible with fixed-bed column operation. Calcium magnesium silicates formed during the thermal treatment slowly hydrolyze producing hydroxyl ions, which in turn neutralize hydrogen ions and raise pH. Because calcium magnesium silicates are present in the vicinity of metals sorption sites of hydrated Fe oxides, competing effects of hydrogen ions were greatly reduced and heavy metals could be removed even under acidic conditions. Selective sorption and not precipitation was confirmed to be the underlying mechanism for metals removal. Once the metals removal capacity was exhausted, the new inorganic sorbent could be regenerated with ammonia and reused. The performance of the synthesized inorganic sorbent was comparable to that of commercially available weak-acid polymeric exchangers.Hybrid Ion Exchanger (HIX) for Arsenic Removal. A new polymeric/inorganic material was prepared by dispersing hydrated Fe(III) oxides in cation exchanger polymer beads using a simple chemical-thermal treatment. The new material, referred to as HIX, showed excellent As(V) and As(III) removal capacity and was compatible with fixed-bed column operation. No preoxidation or pH adjustment was necessary for HIX material. HIX could be regenerated with sodium hydroxide and reused without any loss in capacity.
Magnetically Active Polymeric Particles (MAPPs). Polymeric sorbent particles are diamagnetic (i.e., they do not possess any magnetic activity). We successfully developed an experimental protocol to impart magnetic activity into various commercial polymeric ion exchangers through in situ formation of crystalline magnetite microparticles within the pores of the polymer particles. Once magnetically active, the polymeric sorbent particles retained their magnetic activity upon exposure to atmosphere and repeated usage through sorption-desorption cycles. Because MAPPs can be easily separated from slurry, sludge, biomass etc., they offer new opportunities for environmental monitoring and separation for complex systems.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 15 publications | 4 publications in selected types | All 2 journal articles |
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Li P, SenGupta AK. Intraparticle diffusion during selective sorption of trace contaminants: the effect of gel versus macroporous morphology. Environmental Science & Technology 2000;34(24):5193-5200. |
R825422 (Final) |
not available |
Supplemental Keywords:
heavy metals, toxic ions, inorganic ion exchanger, metals removal., RFA, Scientific Discipline, Water, POLLUTANTS/TOXICS, Engineering, Chemistry, Environmental Chemistry, Engineering, Chemistry, & Physics, Arsenic, Chemicals, Drinking Water, Water Pollutants, heavy metals, ion exchange, metal removal, chelating exchanger, treatment, chemical composition, chemical detection techniques, metal speciation, drinking water contaminants, physicochemical, metal-chelate complexesProgress and Final Reports:
Original AbstractThe 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.