Cation removal using cellulose chemically modified by a Schiff base procedure applying green principles

Pentane-2,4-dione (acetylacetone) molecules were covalently incorporated under several different conditions to ethylene-1,2-diamine (en)-modified cellulose, using polar solvents or without solvents. The quantitative amount of en incorporated was given from 0.37+/-0.01 to 3.03+/-0.01 mmol of nitrogen per gram of cellulose, depending on the synthetic routes and after Schiff base formation this percentage was reduced by 1.38-6.12%. The synthetic routes indicated that lower solvent volumes produced higher amounts of en incorporation. However, the highest degree of pendant groups on the polymeric cellulose structure was obtained from a solvent-free reaction route. This procedure was applied for synthesizing all Schiff bases, causing a decrease in the amount of nitrogen. The available basic centers on the best covalently bonded biopolymer were investigated for adsorption of divalent copper, cobalt, nickel, and zinc from aqueous solution, with a capacity order of Cu2+ > Co2+ > Ni2+ > Zn2+.