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Modified Natural Zeolite (Mnz) as a Selective Sorbent for Simultaneous Removal of Arsenites and ArsenatesEPA Grant Number: R831430
Title: Modified Natural Zeolite (Mnz) as a Selective Sorbent for Simultaneous Removal of Arsenites and Arsenates
Investigators: Sengupta, Arup K. , Munley, Vincent G.
Current Investigators: Sengupta, Arup K.
Institution: Lehigh University
EPA Project Officer: Richards, April
Project Period: October 1, 2003 through September 30, 2004
Project Amount: $50,000
RFA: New Technologies for the Environment (NTE) (2003) RFA Text | Recipients Lists
Research Category: Nanotechnology , Sustainability , Pollution Prevention/Sustainable Development
The newly promulgated arsenic maximum contaminant level (MCL) of 10 µg/L in drinking water would require corrective action for about four thousand (4,000) water supply systems in the USA serving small communities. In addition to being cost effective, the arsenic removal system for small communities should be operationally simple requiring minimal human intervention. The total dissolved arsenic concentration in groundwater may undergo changes over a period of time. Also, both As(III) and As(V), referred to as arsenites and arsenates, may be present simultaneously in groundwater. Arsenic concentration in the treated water should remain less than 10 µg/L independent of any fluctuations of arsenic concentrations and relative distribution of arsenites and arsenates in groundwater. A simple-to-operate fixed-bed sorption process can be very effective in satisfying these goals. The general objective of this project is to develop a Modified Natural Zeolite (MNZ) that is inexpensive, highly selective toward As(III) and As(V) and suitable for use in fixed-bed units requiring no pre- or post-treatment.
Recent studies at Lehigh University led to the development of a hybrid polymeric/inorganic sorbent with high sorption affinity toward As(III) and As(V) compounds. Each sorbent particle is essentially a cation exchanger bead within which agglomerates of nanoscale Hydrated Fe(III) Oxide (HFO) particles have been uniformly and irreversibly dispersed using a simple chemical-thermal technique. However, the parent cation exchanger bead is expensive ($2.00 per pound) and the sorbent needs to be regenerated and reused. The regeneration is feasible but the procedure is operationally complex for small communities with limited resources. Southwest and western regions of the USA are blessed with an abundant supply of inorganic natural zeolites which are essentially granular aluminosilicates. Of all the naturally occurring zeolites, clinoptilolite has high cation exchange capacity, is porous, inexpensive and readily available in North America. The cost of clinoptilolite varies from 10-15 cents/pound. We propose to utilize clinoptilolite's ion exchange capacity to irreversibly disperse Hydrated Fe(III) Oxide (HFO) particles within its porous structure using the chemical-thermal technique developed in our laboratory. Subsequently, the resulting material, referred to as Modified Natural Zeolite or MNZ, will be tested for its arsenic removal properties.
The development of MNZ provides a desirable synergy: while the zeolite provides favorable hydraulic properties in a fixed-bed column, HFO particles are the active ingredients for selective sorption of arsenites and arsenates. MNZ is inexpensive and, therefore, can be discarded after one-year cycle avoiding the need for regeneration. The results of the study are likely to validate that clinotilolite, an inexpensive natural zeolite, can be tailored into an arsenic-selective sorbentusing a simple chemical-thermal technique.