Hydrolysis and recycling of urea formaldehyde resin residues

Urea formaldehyde (UF) resin residues generate many poisonous chemicals during traditional disposal technologies for organic hazardous wastes. In this study, hydrothermal hydrolysis was developed to decompose, remove, and recycle cured UF resin. Under 140 °C and 2 h of hydrothermal process, 20 mL of either 2 M HCl or 30 w.t. % of formaldehyde solutions can decompose as much as 1.7 g of cured UF resin. In addition, from the attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), gas chromatography-mass spectroscopy (GCMS), X-ray diffraction (XRD), and ¹H nuclear magnetic resonance (NMR) analyses, it confirmed that the hydrothermal hydrolysis could hydrolyze cured UF resin. With 2 M HCl, the hydrolysis of cured UF resin can form NH₄Cl as the final product. Moreover, formaldehyde solution hydrolysis can fully recycle the decomposed UF resin. The hydrolyzed formaldehyde solution can be directly used as a normal formaldehyde solution for UF resin synthesis. The synthesized resin, which contains about 6 w.t. % of decomposed cured UF resin, has similar chemical structures and bonding performance as normal UF resin. These hydrolysis methods generate no harmful gases and pollutants, nor any pre- or post-treatments, which proves its feasibility in UF resin residues safe removal or disposal and recycle.