Abstract: Alkaline lignin-poly (vinyl alcohol)-urea (AL-PVA-U) film was prepared by crosslinking with formaldehyd (F). The effects of alkaline lignin and formaldehyde on nitrogen release,as well as the release mechanism,were investigated. The films were characterized by XRD and FT-IR-ATR.The result showed that the addition of alkaline lignin limited the release of nitrogen in the film and resulted in an increase of the release balance time.The fastest release rate was observed as alkaline lignin and polyvinyl alcohol as blended with 5:5 ratio,and the maximum release balance time as well as the highest accumulative release rate achieved under this condition represented 192 h and 77.73%, respectively.Proper amount of formaldehyde facilitated the crosslinking among alkaline lignin,polyvinyl alcohol and urea. The formation of linear and reticular structures restricted the release of the nitrogen in the films. Compared with the blend film,the crystallinity of the crossed alkaline lignin-polyvinyl alcohol-urea film decreased.The curve of nitrogen cumulative release rate displayed a S pattern.The correlation coefficients of Ritger-Peppas model and Quadratic polynomial model were 0.950 9 and 0.976 3,respectively.The release index (n) of Ritger-Peppas model was 0.816 7,which indicated that the release mechanism of nitrogen was the comprehensive effects of diffusion and erosion.

Key words: alkaline lignin, poly (vinyl alcohol), nitrogen, crosslinking, slow-release