Abstract: The optimum preparation craft of the different low-molecular weights chitosan was studied by H2O2-HAc control oxidation method. It synthesized three kind of chitosan with different low molecular weight(MW 780000、110000 and 10000 respectively) and obtained a series of their ferrous complexes by optimizing the coordinate conditions between low-molecular chitosan and ferrous complexes. The optimal adsorption conditions of urea with different molecular weight chitosan-Fe(II) complexs were studied. It resulted that the complexes exhibited high sorptive capacity and good selectivity for urea.The sorption capacity was affected by the metal content in the complexes,time of sorption, concentration of urea etc.The sorption capacity was found 60.90mg/g for urea by the chitosan metal complexes at pH 5.5 and the concentration of urea being l.5mg/ml. The adsorption capability of urea on chitosan-Fe(II) complexs was higher than other materials and slightly less than polyacrylic acid resin-Cu(II) complexes. Yet chitosan-Fe(II) complexs could still be regarded as a new kind of high efficiency urea adsorbent material in view of the excellent biological character and medical function of the chitosan and their complexes.

Key words: chtiosan, urea, Fe(II) complex