Combination mechanism and dimethyl ether removal performance of organic-bound water in kitchen waste

Dewatering plays an important role in kitchen waste reduction and resource utilization; however, the mechanism of water combination and removal remains unclear. In this study, dimethyl ether solvent was used to investigate the water occurrence state and dewatering pattern in kitchen waste, and the key organic components, hydrophilic functional groups, and water removal mechanism were clarified. The results showed that all the water existed in the state of organic-bound water, in which proteins were the key organic matters affecting dewatering and the hydrophilic functional groups CO/CN, CO, and amine-N.

combined with water through hydrogen bonding were the key mechanisms. Through competition with hydrophilic functional groups, dimethyl ether released 54.83–87.85% of the water to the liquid phase, while the hydrophilic components and hydrophilic functional groups were retained in the solid phase. Simultaneously, the addition of additives verified that enhanced disruption of hydrogen bonding between water and hydrophilic functional groups could improve the dewatering efficiency. It was concluded that more attention should be paid to reducing or disrupting the hydrogen bonding of hydrophilic functional groups on the surface of the solid phase with water to improve the kitchen waste dewatering performance.