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Investigation of Hydronium Diffusion in Poly(vinyl alcohol) Hydrogels: A Critical First Step to Describe Acid Transport for Encapsulated BioremediationBioremediation of chlorinated aliphatic hydrocarbon-contaminated aquifers can be hindered by high contaminant concentrations and acids generated during remediation. Encapsulating microbes in hydrogels may provide a protective, tunable environment from inhibiting compounds; however, current approaches to formulate successful encapsulated systems rely on trial and error rather than engineering approaches because fundamental information on mass-transfer coefficients is lacking. To address this knowledge gap, hydronium ion mass-transfer rates through two commonly used hydrogel materials, poly(vinyl alcohol) and alginic acid, under two solidification methods (chemical and cryogenic) were measured. Variations in hydrogel crosslinking conditions, polymer composition, and solvent ionic strength were investigated to understand how each influenced hydronium ion diffusivity. A three-way ANOVA indicated that the ionic strength, membrane type, and crosslinking method significantly (p < 0.001) contributed to changes in hydronium ion mass transfer. Hydronium ion diffusion increased with ionic strength, counter to what is observed in aqueous-only (no polymer) solutions. Co-occurring mechanisms correlated to increased hydronium ion diffusion with ionic strength included an increased water fraction within hydrogel matrices and hydrogel contraction. Measured diffusion rates determined in this study provide first principal design information to further optimize encapsulating hydrogels for bioremediation.
Implementing the Elements of Course-Based Undergraduate Research Experiences (CUREs) in a First-Year Undergraduate Chemistry Laboratory with Bioremediation RelevanceGeneral chemistry laboratories are a core requirement for nearly all STEM (Science, Technology, Engineering, and Mathematics) majors and have the greatest breadth in disciplines and audience of any STEM course at a university. A bioremediation Course-based Undergraduate Research Experience (CURE) for first-year undergraduate students was developed to capture and engage student interest for this diverse group. In this multiweek laboratory exercise, students joined an NSF-funded research project designed to enhance the bioremediation of chlorinated aliphatic hydrocarbons. Students explored various biocompatible polymer blends and cross-linkers for encapsulation to create protection for bioremediation microbes. In this “guided research” model, students constructed the measurement apparatus, made hydrogel blends, and then monitored the diffusion of acid via pH measurements using a custom instrument. Herein, we describe how CURE elements were implemented within the bioremediation research experience culminating in student teams presenting posters at our university’s undergraduate research symposium. An open-laboratory format facilitated an active research group experience and recitation “group meeting” provided flexibility and needed time for reflection and discussion. Student survey data and course evaluations indicated that students saw value in this genuine research experience and enjoyed the freedom and time to practice and hone skills as both a scientist and teammate inmore »