Study on the Constituents of Walnut Shell

The chemical constituents of walnut shell were systematically studied. The results showed that the main constituents of walnut shell were lignin, cellulose and hemicelluloses. Compared with some other plants, the contents of cold and hot water extractives, 1% NaOH solution extractives, acid-insoluble lignin in walnut shell were higher, while the cellulose content was lower, and the pentosan content was close to that of hardwood. The constituents of the walnut shells from different growing areas were somewhat different, but the major component was the same as acid-insoluble lignin. The main elements contained in the walnut shell included C, H, O, N, S, and walnut shell also contained some micro-scaled elements, such as Ca, Mg, Fe, Si, P, etc.. The lignin type in walnut shell belonged to GS (Guaiacyl-Syringyl) lignin, in which G type was the predominant. There was comparatively large amount of -OCH₃ base in the walnut shell lignin.