Sunlight Breakdown of Acetaminophen in Water

ISEF Category: Chemistry

Subcategory: Environmental Chemistry  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Pain relievers do not just vanish after you swallow them. Traces can enter wastewater and stay active in the environment. You can test a simple cleanup idea, sunlight plus TiO2-coated glass, and measure how fast the signal drops. This project mixes environmental chemistry with real-world water treatment.

What Is It?

Photocatalysis means using light to speed up a chemical change. In this project, TiO2, or titanium dioxide, acts like a light-activated helper. When sunlight hits it, the surface can help break acetaminophen molecules apart in water.

Think of TiO2 as a tiny solar-powered workbench. The drug molecules land on the surface, light turns the surface on, and the molecules start breaking down. You are not just asking whether the drug disappears. You are asking how fast it disappears and which conditions make the process work better.

Smartphone colorimetry gives you a way to track the change with photos. If the acetaminophen concentration changes the color of a test solution, your phone can measure that color change and turn it into numbers. Then you can fit the data to a kinetics model, which is just a math description of reaction speed.

Why This Is a Good Topic

This is a strong science fair topic because you can test one clear variable at a time, like coating amount, glass surface type, or light exposure. It connects to water pollution and drug removal, which are real environmental problems. You can build a project with basic lab access, collect real data, and learn how to turn photos into concentration curves and reaction rates.

Research Questions

• How does TiO2 coating density on recycled glass affect the rate of acetaminophen degradation under sunlight?
• What is the effect of glass surface texture on photocatalytic activity for acetaminophen removal?
• Does sunlight exposure time change the apparent Langmuir-Hinshelwood rate constant for acetaminophen breakdown?
• To what extent does pH change the photocatalytic degradation rate of acetaminophen in water?
• Which recycled glass type gives the strongest smartphone colorimetric signal during acetaminophen degradation studies?
• How does repeated reuse of the same TiO2-coated glass change the degradation rate over multiple trials?

Basic Materials

• Commercial TiO2 sunscreen or cosmetic ingredient labeled as titanium dioxide, preferably non-nano if available.
• Recycled clear glass slides, jars, or tiles with similar size and thickness.
• Acetaminophen tablets or a standard acetaminophen solution for comparison.
• Distilled water.
• Smartphone with a manual camera app.
• White background box or simple light box for photo consistency.
• Printed color reference card or a homemade white balance reference.
• Transparent cups, beakers, or small glass containers.
• Pipettes, droppers, or plastic transfer pipettes.
• Digital kitchen scale with 0.1 g accuracy.
• Masking tape and permanent marker for labeling.
• Safety goggles and nitrile gloves.
• Timer or stopwatch.

Advanced Materials

• UV-Vis spectrophotometer for validating smartphone colorimetry.
• Quartz cuvettes or clear sample cells matched in path length.
• Magnetic stir plate and stir bars for controlled mixing.
• pH meter with calibration buffers.
• Analytical balance with milligram precision.
• BET or surface characterization data for the TiO2 material, if available through a lab.
• Scanning electron microscopy or optical profilometry access for coating uniformity checks.
• HPLC or LC-MS access for confirming acetaminophen loss versus byproduct formation.
• Solar simulator or controlled light source for repeatable irradiation conditions.
• Standard laboratory glassware for preparing calibration and control samples.

Software & Tools

• ImageJ: Measures color intensity from photos and helps convert image data into numerical signals.
• Python: Organizes trial data, fits calibration curves, and estimates kinetic constants.
• Google Sheets: Tracks sample labels, exposure times, and basic plots for quick checks.
• RStudio: Runs statistics, confidence intervals, and model comparisons for your kinetics data.
• NIH ImageJ Color Deconvolution plugin: Separates color channels when your assay depends on subtle color changes.

Experiment Steps

1. Define the single question you want to answer first, such as coating amount, light exposure, or pH.
2. Choose one detection method and prove it can turn acetaminophen change into a repeatable number.
3. Design controls that separate photocatalysis from sunlight alone, glass alone, and TiO2 alone.
4. Plan a calibration approach so you can convert smartphone color readings into concentration estimates.
5. Decide how you will compare your data to a Langmuir-Hinshelwood model and what fit quality will count as strong evidence.
6. Build a replication plan that includes enough repeats to compare treatments with confidence.

Common Pitfalls

• Using room lights or mixed sunlight during photo capture, which makes the smartphone signal drift between trials.
• Assuming TiO2 loss means acetaminophen loss, which can confuse adsorption with true degradation.
• Skipping a no-catalyst control, which makes it impossible to tell whether sunlight alone did the work.
• Coating recycled glass unevenly, which creates patchy activity and noisy rate data.
• Fitting kinetics to only one trial, which hides random variation and weakens the model test.

What Makes This Competitive

A stronger project will compare several well-chosen controls and show that your signal really tracks chemical change, not just color shifts. You can raise the level by testing multiple surface types, building a careful calibration curve, and comparing different kinetic models, not just one line fit. Clean replication and a clear error analysis matter a lot. If you also check whether the drug disappears without forming a misleading byproduct signal, your project looks much more like real environmental chemistry.

Project Variations

• Swap acetaminophen for another common pharmaceutical, such as caffeine or ibuprofen, and compare how fast each degrades under the same coated-glass setup.
• Test indoor LED light versus direct sunlight to see whether light quality changes photocatalytic performance.
• Compare plain glass, roughened glass, and recycled bottle glass to see how surface properties affect TiO2 adhesion and reaction rate.

Learn More

• PubMed: Search review articles on photocatalytic degradation of pharmaceuticals and acetaminophen in water.
• NIH PubChem: Look up acetaminophen properties, structure, and related chemical safety information.
• USGS Water Science School: Read about emerging contaminants and how they move through water systems.
• NOAA Education: Find background on sunlight, UV radiation, and how light conditions change by location.
• NASA Earth Observatory: Explore solar radiation concepts and how sunlight intensity varies with weather and season.
• MIT OpenCourseWare: Search environmental chemistry and reaction kinetics materials for free lecture notes and problem sets.