(326e) Removal of Toxic Chlorine-Containing Chemicals by Zirconium Hydroxide-Based Sorbent Media

Toxic chemical removal is of particular interest in many areas, including air purification, separations, and scrubbing processes.  In many cases, highly microporous materials containing treatments such as impregnants are used to remove high volatility toxic chemicals.  In particular, air purification devices are typically over-designed for physical adsorption of low volatility chemicals so as to provide enough removal capacity for high volatility chemicals.  To reduce the volume, and therefore cost and encumbrance, necessary for high volatility chemical removal, new substrates must be developed focusing on the incorporation of a high density of functional, reactive moieties. 

Zirconium hydroxide, Zr(OH)₄, has been identified as a highly efficient sorbent for removal of acid-forming gases, examples of which include cyanogen chloride and sulfur dioxide.  Due to its high density of hydroxyl groups, Zr(OH)₄ provides enormous capacity for acid gases in a lower-porosity pore structure.  In this study, novel microporous sorbents comprised of zirconium hydroxide were investigated for the ability to remove chlorine gases, examples of which include Cl₂, COCl₂ and HCl.  Chlorine compounds represent toxic industrial chemicals (TICs) which pose inherent risks for personnel associated with their transportation, storage and use, as well as first responders. 

Removal capabilities of Zr(OH)₄-based filtration media were determined by recording breakthrough curves for chlorine gases.  Zr(OH)₄ impregnated with triethylenediamine (TEDA) was able to effectively remove all chlorine gases evaluated in this study, yielding breakthrough times significantly greater than impregnated carbon media.  The addition of TEDA to the formulation promoted the hydrolysis of Cl₂ and COCl₂, yielding prolonged breakthrough times.  Zr(OH)₄ is comprised of bridging and terminal hydroxyl groups, and XPS analysis revealed that only the terminal hydroxyl groups contributed to the removal of chlorine gases.  Results from the study demonstrate the feasibility of a reactive substrate for the removal of high volatility reactive gases.