# Analysis of the Delamination Process with Nitric Acid in Multilayer Composite Food Packaging
## 2 Materials and Methods  
In this study, various delamination experiments were conducted using potato chip packages. Packaging materials were obtained from post-consumer waste, including a mixture of different types of packaging waste. However, due to the absence of a comparative analysis of results from the waste mixture, multilayer potato chip packaging featuring polymer, aluminum, and visually appealing print, was selected as the sample for subsequent experiments. Packaging from a single company was employed for all experiments to ensure the accuracy of the results. It is imperative to guarantee that the acid fully covers the packing strips during the process. The procedure involves the following steps:  
1. Place the packing strips in a flask. 2. Pour the desired concentration of nitric acid into the flask. 3. Immerse the flask in room-temperature water in an ultrasonic bath. 4. Insert a stirrer into the flask and activate it. 5. Initiate the ultrasound and gradually increase the temperature. 6. As the mixing speed does not significantly impact the process, set it to a minimum level. 7. Monitor the process as the polymer layers separate and the aluminum melts. 8. The process is deemed complete once the aluminum melts entirely. 9. As the separated polymer layers augment the sample's volume, choosing an appropriately sized container and leaving sufficient empty space is vital. Laboratory-scale reactor were used in the study. Figure 1 shows the reactor's main parts. Although the packages might not have been washed before delamination, we still recommend washing them. As demonstrated throughout the process, delaminating cleaner packages enables the preservation and reuse of cleaner reagents. The packages were cut into strips with three different widths: 0.5 cm, 1.0 cm, and 1.5 cm, to prepare the samples. The length of all samples remained consistent at 12.0 cm. The aqueous solution employed for the delamination of multilayer potato chip packaging waste consisted of nitric acid in three concentrations: 20%, 25%, and 30%. Nitric acid was diluted with distilled water. The use of non-concentrated nitric acid was deemed an intelligent solution, as it not only facilitated the delamination of the packaging layers but also dissolved the aluminum layer present in the packaging. The temperature was a critical controlled parameter considered in the experiments. Various polymers in the packaging, each with distinct melting points, necessitated conducting these experiments at low temperatures. Ensuring that the strip edges remained unaffected by temperature was crucial for delamination. Consequently, placing the packaging strips in the solution at room temperature was vital before gradually increasing the temperature. A thermoregulated ultrasonic bath facilitated the temperature increase, continuously monitoring the acid's temperature in the flask using a thermometer. A rate of 2-3 degrees per minute was maintained during the temperature increase. Experiment temperatures of 55 \({}^{\circ}\)C, 65 \({}^{\circ}\)C, and 75 \({}^{\circ}\)C were utilized. The boiling temperature of nitric acid is 83 \({}^{\circ}\)C [10]. Upon completion of the process and the separation of the polymers from the acid, the hot acid was allowed to cool, and the remaining acid was washed off the polymers. The polymers were subsequently dried in a Binder drying oven at 104 \({}^{\circ}\)C. A portion of the used nitric acid was stored for further study, and the remainder was disposed of according to university safety regulations. The experiment focused on studying the dissolution of aluminum in nitric acid. The primary objective was to dissolve aluminum in nitric acid using 1 g of packaging and 200 mL of nitric acid. It should be noted that the reagent proportions can be adjusted according to the experiment's requirements. Figure 1: A laboratory-scale reactor was utilized in the study. 1: Overhead mixer. 2: Flask containing MLPW strips and aqueous nitric acid solution. 3: Ultrasonic bath.