2. Experimental
2.1. Materials and catalyst preparation Water scale was obtained from home kitchens in Lianyungang city, eastern China. All chemicals were of analytical grade and used as received. Refined soybean oil was procured from local market. Water waste scale was washed thoroughly with distilled water several times to remove the impurities and followed by drying in hot air oven at 105 C for about 24 h. The dried water scales were
subsequently ground to fine powder and calcined in a muffle furnace at different temperatures ranging from 200 C to 1000 C for 2.5 h to prepare the novel catalysts.