1. P SEUDO -Z ERO - O RDER K INETICS : D IFFUSION THROUGH A P OLYMER M EMBRANE U SING A S ATURATED S OLUTION R ESERVOIR S YSTEM Jan-alfred Aquino | Christopher Chen | Yanglu Chen | Zachariah DeGiulio | Katherine Dong | Christina Floristean | Michelle Guo| Alexandra Kapadia | Robert Kolchmeyer | Erik Massenzio | Adam Richardson | Jessica Xu Dr. David Cincotta | Alberto Rivera

2. Controlled Release Zero-order kinetics Rate independent of concentration Does not often occur in nature Applications: o Medicine o Agriculture o Cosmetics

3. Pseudo-Zero-Order Kinetics Fick's Law: A pseudo-zero-order system would achieve a constant rate of release, but would not be independent of concentration. This can be done by holding the concentration gradient constant.

4. Hypothesis IF: An apparatus is made that allows for diffusion of a saturated solution into a body of water across a membrane THEN: Pseudo-zero-order diffusion should be observed Maintain a constant concentration gradient

5. Polymer Membrane Repeating structural units of monomers Amorphous structures more easily allow diffusion than crystalline structures Ethylene-vinyl acetate o 10% EVA o 12% EVA

6. Choosing Citric Acid Solid at room temperature Chosen over maleic acid and sodium chloride Conductivity & pH probe Continuously measured over longer periods of time Most consistent results Citric acid Maleic acid

7. Experimental Design: Saturated Solution Reservoir System Saturated solution of citric acid added to petri dishes Solute passes through the membrane Additional solid citric acid added to continuously re- saturate the solution Pseudo-zero-order Polymer Membrane Saturated Solution Solid Citric Acid Petri Dish Water Basin

8. Final Setup

9. Experimental Design Design Features: Water-tight petri dishes Petri dish supports Maximize water and solution contact with the membrane Surface area optimization Uniform water level with respect to the petri dish

10. Results - The Diffusion of Citric Acid across a 10% EVA Membrane

11. Results – The Diffusion of Citric Acid Across 10% and 12% EVA Membranes With additional solute 10% EVA (top graph) 12% EVA (bottom graph) Suspected pH meter issue resulting in a few nonlinear curves 10% EVA Trials 12% EVA Trials

12. Results – The Diffusion of Citric Acid Solution Across 12% EVA 12% EVA with 2g solid Trials with 2g extra solid are zero order

13. Discussion Rate was faster in first few hours Tested with 10% EVA and 12% EVA Polarity accounts for permeation Reproducible rates remain elusive

14. Conclusion Achieved pseudo-zero-order kinetics with reservoir system Polar likes polar: Citric acid diffused through 12% EVA more effectively than 10% EVA Novel method for modeling a controlled-release system Data was supportive of hypothesis More needs to be done to conclusively accept or refute the hypothesis

15. Future Studies Explore alternate methods of measuring diffusion Solute embedded in polymer Biodegradable polymers Solute with lower solubility Mathematical models based on parameters of polymer membrane and solute Generalized curve fits

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17. Acknowledgements Dr. David Cincotta, Advisor Alberto Rivera, Assistant Dr. David Miyamoto, Director New Jersey Governor's School in the Sciences and its Sponsors