Year Established: 2013 Start Date: 2013-03-01 End Date: 2015-02-28
Total Federal Funds: $19,216 Total Non-Federal Funds: $60,035
Principal Investigators: Huichun Zhang
Abstract: 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 and the country. 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 using resins (both neutral polymeric sorbents and ion exchange resins) to remove ECs seems promising. For the grant we received from the PA-WRRC between March 2012 and February 2013, we are examining the behavior of anion exchange resins in the removal of a group of anionic carboxylates as analogues for NOM and anionic ECs. Given the complexity of ECs and the common occurrence of cationic functional groups such as positively charged amines in ECs, it has become very important to understand how different cations are removed by cation exchange resins (CERs). It is only after we have a systematic understanding of how variably charged ECs can be removed by resins of different structures that we can design efficient and robust EC removal processes for drinking water and wastewater treatment purposes. For this reason, a group of structurally diverse quaternary ammonium ions will be examined as representative cationic ECs, and this proposed project will: (1) Separate solvent-associated interactions (i.e. water-solute, water-resin and water-water interactions) from solute-resin interactions; (2) Obtain polyparameter-linear free energy relationships (pp-LFERs) between the overall adsorption Gibbs free energy G and the dominant interaction forces; (3) Elucidate the relative contributions of non-electrostatic interactions (London, Debye, dipole-dipole, -, and H-bonding) and electrostatic interactions to the overall selectivity and removal of quaternary ammonium ions by CERs; and (4) Develop quantitative models that can be used to estimate removal of other structurally related cations by CERs. To the best of our knowledge, this study will be the first to systematically examine the fundamental mechanisms of cationic ECs removal by CERs. The contributions of solute-resin and solvent-associated interactions to the overall adsorption energy will be separately quantified, which offers deeper insights into adsorption mechanisms. Models for the first time will be developed to predict the adsorption capacities of cationic ECs by various CERs. In the end, a large variety of CERs being offered by a number of chemical companies can be categorized based on their structural properties and fractional contributions of the involved interaction forces. In addition, the developed models and approaches will lead to a mechanistic understanding of the adsorption processes of other commonly used sorbents/ion exchangers. A fundamental understanding of the adsorption mechanisms and development of predictive models will contribute to a major advance in the development of resins as a new water treatment technology targeting ECs removal. Application of the developed models and approaches to other sorbents will also take the understanding of adsorption processes in general to a new level that is not accessible using current approaches. Education and outreach activities, geared towards an increased diversity in environmental engineering, will provide our society with more women and underrepresented minority engineers equipped with the knowledge, training, and social consciousness needed to realize sustainable water treatment technologies. Outreach to communities with diverse backgrounds will increase awareness of ECs and practices to reduce the EC burden in wastewater.