Image Analysis to Demonstrate Adsorption and Absorption Processes Through Image Brightness Using Copper(II) Ions and Fish Scales in Teabags: A Colorimetric-Based Analysis

We present a smartphone colorimetry activity designed to enhance students' understanding of adsorption and absorption processes through practical, hands-on experience. This activity utilized fish scale waste from Macolor niger as biosorbents for Cu(II) ions. Raw dried fish scales were enclosed in teabags and immersed in a known-amount copper(II) sulfate solution to observe their adsorption capabilities, with deionized water serving as a control. Students used their smartphones to capture images of the dried fish scales before and after adsorption and analyzed the R-values of the remaining solutions. They learned how to produce and use a calibration curve, determine average particle sizes, absorbance, and percentage Cu(II) ion removal through image analysis using ImageJ software. Statistical comparisons were conducted using the Mann-Whitney U Test via Jamovi software. The students tested their own hypotheses, reflected on their findings, and suggested improvements to the experiments. The overall activity not only demonstrates key chemical concepts but also integrates environmental science by showcasing the potential of using biosorbents for heavy metal ion removal. It is particularly suitable for high school and introductory chemistry courses, combining traditional laboratory skills with modern image analysis and statistical techniques.