Amination of wood sawdust for removing anionic dyes from aqueous solutions

Inexpensive and efficient cellulose-based adsorbents were prepared by the reaction of cross-linked polyethylenimine (CPEI) with an agricultural waste (i.e., wood sawdust). Factors affecting the extent of amination, such a CPEI concentration, pH, time, and temperature of reaction as well as sawdust particle size range, were studied. The obtained adsorbents were found to be highly effective for removal of anionic dyestuffs (i.e., direct, reactive, and acid dyes) from aqueous solutions. The presence of CPEI on and/or within the purified sawdust provides cationic active sites (i.e., amino groups) and enhances the substantivity of wood cellulose for anionic dyes, thereby improving the percent color removal.