Year Established: 2012 Start Date: 2012-03-01 End Date: 2014-02-28
Total Federal Funds: $40,000 Total Non-Federal Funds: $105,212
Principal Investigators: Huichun Zhang
Abstract: The projected rapid growth in electricity and water demands in the next a few decades in the commonwealth of Pennsylvania requires the thermoelectric power industry to explore low-quality water as sources for make-up water. As such, technologies are greatly needed to effectively remove natural organic matter (NOM) from various water sources, particularly within the existing ion exchange systems without changing the present plant design. In addition, the occurrence of emerging contaminants (ECs) in our water systems and in the environment is among the greatest environmental challenges facing the commonwealth of Pennsylvania. Meeting this challenge with conventional technologies alone is difficult and costly. Armed with a wealth of information concerning water treatment technologies using activated carbon, the development of a new technology to remove ECs using ion exchange resins seems promising. Given the complexity of NOM and ECs of different origins and the common occurrence of benzoic acid moiety in NOM and ECs, it is very important to understand how different benzoic acids are removed by anion exchange resins (AERs) before we can design more efficient and robust NOM and EC removal processes. For this purpose, this proposal will (1) elucidate the relative contribution of each interaction force (London, Debye, dipole-dipole, H-bonding, and electrostatic interaction) to the overall selectivity and removal of 5 benzoic acids by 5 commercially available AERs; (2) quantitatively elucidate the fractional contribution of each interaction force to the overall adsorption Gibbs free energy; and (3) regenerate the spend resins to achieve sustainable treatment of Power Plant make-up water, drinking water and wastewater effluents. These research objectives will be achieved through multi-pronged approaches as described in the five major research tasks below: (1) characterization of the selected commercial AERs; (2) adsorption of 13 non-ionic aromatic compounds by two non-ionic resins to illustrate the relative contribution of each non-electrostatic interaction force; (3) ion exchange of 5 benzoic acids by 5 AERs to correlate selectivity coefficient to interaction forces; (4) development of quantitative relationships between the removal behavior of AERs as a function of their physicochemical and structural properties; and (5) regeneration of the spend resins using a combination of NaOH, NaCl and organic solvents. Adsorption isotherms of the target compounds will be obtained by varying solute concentration from 10-3 V 10-5 of the water solubility (Cs) up to Cs. All isotherms will be fitted with the Polanyi theory V both the original Dubinin V Ashtakhov model and a modified version based on normalizing the adsorption affinity according to the n-hexadecane-water distribution coefficient V to obtain the adsorption capacity (Q0) and the adsorption energy (E). Polyparameter linear free energy relationships will be established between Q0/E/selectivity and properties of both benzoic acids and AERs. Overall, this project will yield a fundamental understanding of the removal mechanism of benzoic acids as NOM and EC analogues by AERs. The developed predictive tools will be critical for the advancement of adsorption/ion exchange based water treatment technologies. The understanding of the removal mechanism of NOM analogues by ion exchange resins will significantly facilitate the development of optimal treatment approaches for individual power plants depending on the usage of the water and the availability of the source water. This research will also provide a mechanistic understanding of the adsorption mechanisms of EC analogues by various resins, establish quantitative relationships that can be used to guide the selection of the type and quantity of resins needed for a given treatment scenario, and develop strategies to regenerate resins for full-scale application of the technology. We anticipate that the ionic exchange/adsorption mechanisms will extend to other sorbents and organic contaminants. In addition, results from this project will not only develop novel water treatment technologies, but also facilitate the application of resins to other processes where separation and purification of materials are needed (e.g., separation and purification of bioproducts from renewable sources).