Preparatin and characterization of microwave assisted activated carbon from organic waste: Potential uses in sodium borohydride methanolysis and dye removal

In this study, pumpkin peel (BKK) was subjected to treatment with potassium carbonate (K2CO3) and then obtained by microwave carbonization for catalyst synthesis. Various experiments were performed with different chemical activators (ZnCl2, KOH, H2SO4, K2CO3), different ratios of chemical activators (1:0.025, 1:0.05, 1:1, 1:2 and 1:3), different impregnation times (12s, 24s, 36s and 48s), microwave powers (100W, 250W, 500W and 1000W) and microwave carbonization times (5min, 10min, 15min and 20min) were carried out to perform optimization studies for the synthesis of the catalyst with the highest catalytic performance. The catalyst that exhibited optimal catalytic activity was prepared with a ratio of BKK:CA (1:2), heating the sample in an oven at 80°C for 12 seconds and then carbonizing it in a microwave oven at 500 watts for 10 minutes. This catalyst was called "pumpkin catalyst" (BKK-CO3-cat). After determining the optimal conditions, performance experiments were performed, taking into account variables such as the amount of catalyst, the amount of NaBH4, the reaction temperature and the reusability. In the catalyzed %2,5 NaBH4 methanolysis reaction by BKK-CO3-cat, the maximum hydrogen generation rate (HGR) at 30°C was determined to be 18384 mL/min.gcat. In addition, the activation energy for BKK-CO3-cat was calculated to be 54.91 kJ/mol. Characterization of the most effective BKK-CO3-cat in terms of catalysis was performed using SEM-EDX, ICP-MS, XRD and FTIR analysis techniques. In the second phase of the study, the potential of the catalyst with carbon support for the adsorption of Methylene blue (MM) dyes was investigated. The adsorption efficiency was determined by optimizing the parameters of temperature, time and adsorbent amount. It was found that Langmuir's isothermal model fitted the experimental data best, indicating that the catalyst was suitable for adsorption. Furthermore, the adsorption kinetics followed the pseudo-second order model and the central composite design (MKT) model provided the highest R² value in the linear model, highlighting temperature as the most effective parameter in the adsorption process. The optimization program resulted in a maximum removal rate of 65,71% for the BKK-CO3-kat catalyst at an adsorbent amount of 44,11 mg, a temperature of 33,55 oC and a time of 164,34 min.