 |
 |
||||
| Home |
 |
| People |
|
| Partner Institutions and Programs |
|
| Research Projects |
|
| Educational Activities |
|
| Publications |
|
| News and Events |
|
| Fellowship Opportunities |
|
| Photo Gallery |
|
| Links |
Regenerable polymer-supported sorbent for aqueous mercury removal
Public concerns on mercury's toxic nature date back to several decades, with the first studies on mercury's human health effects conducted in the early 1950's . At present, mercury is a widespread and well known environmental pollutant. Coal-burning power plants account for over 40 % of all domestic human-caused mercury emissions, which makes them a major human-caused source of that element in the environment. Waste streams generated by metal processing plants and the medical industry are other major sources of mercury pollution. Once released, mercury may pose health risks per se or after biotransformation into an even more poisonous derivative, methylmercury, that can cause permanent brain damage. A number of methods for capturing mercury and its compounds have been developed to date. The major ones are microbial demercurization, mercury absorption on powdered activated carbon (which may be sulfur-impregnated for higher efficiency); precipitation of mercury sulfide or thiolates from aqueous solutions, absorption on thiol-modified mesoporous materials, capture with non-selective synthetic polymers (ion-exchange or non-specific complexing materials or shredded tire rubber) or natural polymers (animal wool). However, neither of these techniques allows for a highly selective binding of mercury by a regenerable material exhibiting high capacity for this metal. For example, the microbial demercurization leads to metal's reduction followed by precipitation or evaporation, but not removal from the environment in a concentrated form. Thiol-based sorbents oxidize in air, and none of the polymers has demonstrated high selectivity for mercury. The development of novel regenerable sorbents capable of an efficient and selective binding of mercury is thus a promising solution to this problem. We are currently working on the development of novel polymeric sorbents based on the cross-linking of a newly developed complexant,H 6 Aza222. By preparing polymeric materials in the form of nanoparticle suspensions with charge that depends on mercury complexation, we expect to achieve easy removal of the polymer sorbents by precipitation after their sorption capacity is saturated (Fig. 1).
Figure 1: SEM micrograph of Aza222 polymeric colloids We are as well studying polymer regeneration by different methods (e.g. acid washing), and plan to test the expected selectivity of the Aza222 materials for Hg 2+ cations (Fig.2). Specifically, the effects of potential interferences such as copper cations on the mercury removal efficiency will be assessed.
Synthesizing membranes using this novel material would allow for the flow-through removal of mercury in aqueous systems and for the continuous treatment of polluted streams with high efficiency and removal capacity. We are preparing Aza222-based membranes using several strategies: (a) from the sorbent material itself, (b) by casting films out of liquid Aza222 solutions and heating them to induce polymerization, (c) by coating wherein we polymerize Aza222 solution and then cast it on a porous support, (d) by preparing (polysulfone) membranes filled with Aza222 nanoparticles. Currently, the work is focusing on regeneration and competitive sorption studies and characterization of membranes' hydraulic resistance, molecular weight cutoff, surface charge, contact angle, and other relevant parameters. Publications: Redko , M. Y., Taurozzi, J. S., Manes, K., Jackson, J. E., V. V. Tarabara. Development of Aza222-based polymers, colloidal sorbents, and membranes for the removal of mercury from aqueous solutions ACS 2007 Spring Meeting, Chicago , IL (accepted)
|
||||||
 |
||||||
|
|
||||||
|
||||||
 |
 |
 |
 |
 |
 |
 |
 |
||||||
