We describe a 2 h general-chemistry experiment that introduces college students not only to the concepts, synthesis, and applications of nanomaterials at an early stage but also the use of a spectrophotometer for quantification and unknown determination based on Beer's Law. The procedure involves students (1) preparing a nanocomposite by chemically incorporating magnetite nanoparticles into activated carbon (AC), (2) using the as-prepared nanocomposite to treat an aspirin "metabolite" solution for 5 min, and (3) spectroscopically evaluating the nanocomposite's removal efficiency for this "pollutant". The spectroscopic measurement is based on a colored complex the pollutant forms with an acidified iron(III)-ion solution. The nanocomposite is magnetically recovered from treated water and is found to remove 90--130 mg of equivalent aspirin mass per gram of AC. The experiment, using commonly available chemicals and equipment, has been performed by 190 students in groups of two to three and is well-received and enjoyed by these students.