Production of nanocrystalline cellulose from medium density fiberboard (MDF) dust

In this study, the production of nanocrystalline cellulose, a high value-added product, from MDF dust, which is a significant amount of fine-grained waste in the furniture industry, was investigated. After the MDF dust was subjected to a simple phosphoric acid boiling pretreatment, the hemicellulose and lignin in the structure were partially removed by organosolv treatment applied at high temperature and pressure in a reactor with ethyl alcohol. Then, it was subjected to a bleaching process with sodium hypochlorite to remove advanced lignin, and a product with high cellulose content was obtained, and then nanocrystalline cellulose was obtained by the applied oxalic acid hydrolysis process. The MDF dust used in the experiments contained 37.43% cellulose as well as extractive material, hemicellulose and lignin. MDF dust in the -75+100 mesh fraction, which was subjected to acidic pretreatment with 0.5% H3PO4 solution, was subjected to organosolv process in the reactor with 0.1 M NaOH catalyst in the optimized conditions at 120°C temperature with a solid/liquid ratio of 1:10 for 60 min, and the cellulose content was increased up to 58.4%. In the meantime, studies were carried out to recover lignin passing into the solution, and it was determined that it was possible to recover lignin from the organosolv liquid by precipitation to a large extent. In order to increase the cellulose content of the organosolv product biomass, a bleaching process was applied by boiling with sodium hypochlorite containing 4% active chlorine for 3.5 hours, and a product containing 89.32% cellulose, 6.68% hemicellulose and 4.0% lignin was obtained. This product with high cellulose content obtained as a result of pretreatments was subjected to an oxalic acid hydrolysis process. The most suitable process conditions for the oxalic acid hydrolysis process were determined by experiments designed with the Central Composite Design technique, one of the experimental design techniques with the Surface Response Method. In the optimization study carried out to maximize product yield and cellulose crystallinity and minimize average particle size, the most suitable experimental conditions were determined as 98.2 °C temperature, 6 M oxalic acid concentration, 78.8 min time and 1.14% H2SO4 catalyst concentration. As a result of the hydrolysis process carried out under optimum conditions, the average particle size of the product obtained was found to be 237 nm, its crystallinity was 69.40% and its cellulose yield was 30.95%. As a result, it was determined that the MDF dust used in the study is a raw material with the potential to be used for nanocrystalline cellulose production.