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Discipline: Chemistry and Chemical Sciences
Subcategory: Environmental Engineering
Krisiam Ortiz-Martínez - University of Puerto Rico - Mayaguez Campus
Co-Author(s): Arturo J. Hernández-Maldonado, University of Puerto Rico-Mayaguez Campus, PR
Access to clean and safe water is essential for life. However, this has been threatened by the presence of what are known as contaminants of emerging concern (CECs). These consist of mixtures of parent compounds and/or metabolites of many everyday use products or compounds generated by chemical degradation processes. Because of the complex chemical nature of CECs and their ubiquitous presence in the environment at trace levels, their removal from water bodies using conventional technologies present great challenges. With the intention of providing treatment alternatives, this work focuses on the development of robust mesoporous silica material (SBA-15) based adsorbents with a flexible and tunable surface targeted to the removal of a particular set of CECs (salicylic acid, naproxen, clofibric acid, caffeine and carbamazepine) both in single and multi-component fashion. SBA-15 was functionalized with amino-organic groups (3-APTES) and a transition metal (Cu2+) via grafting techniques in an effort to introduce complexation type interactions with the aromatic rings and/or functional groups of the CECs through electron donation and backdonation at ambient conditions. All the adsorbent materials were characterized using X-ray diffraction, thermal gravimetric analysis, inductively couple plasma mass spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and zeta potential to determine structural, chemical, and textural properties. The un-modified and modified adsorbents were also evaluated for dynamic adsorption of CECs using fixed-beds with the intention of elucidating the effect of non-equilibrium conditions on selectivity as well as competitiveness between adsorbates. To ensure accurate measurements, CEC concentrations were measured using a triple quadrupole high performance liquid chromatography MS/MS system. In general, it was demonstrated that the interactions and affinities between the SBA-15 variants and the prescribed CECs were significantly influenced by both the adsorbate functional groups and, when present, the transition metal. The inclusion of Cu2+ produced larger adsorption capacities and better affinity toward the acidic and hydrophobic CECs, whereas for the unmodified variant the best affinity was toward the neutral and hydrophilic CECs. Future research will focus on conducting extended dynamic adsorption tests for processing multi-component mixtures of CECs and their related metabolites at sub ppm level concentrations. This will shed light into the understanding of the governing adsorption driving forces as well as kinetic mass transfer and selectivity mechanisms under more realistic scenarios.
References: Hernández-Maldonado, A.J.; Blaney, L. Advances in Analysis, Treatment Technologies, and Environmental Fate of Emerging Contaminants. J. Hazard. Mater. 2015, 282, 1.
Funder Acknowledgement(s): This material is based upon work supported by the National Science Foundation (NSF) under Award No. HRD-1345156 (CREST Phase 2 Program). The authors also wish to acknowledge support from Puerto Rico NASA Space Grant Graduate Fellowships Program.
Faculty Advisor: Arturo J. Hernández -Maldonado, arturoj.hernandez@upr.edu
Role: For this work, I synthesized and characterized all mesoporous silica materials. I also performed the adsorption tests and analyzed the SBA-15 adsorbents performance.
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