Adsorption of Cd2+ and Cu2+ by oxidized cellulose from TEMPO-mediated selective oxidation of alkaline natural cellulose pulp

In the present work, oxidized celluloses were prepared by the 2,2,6,6-Tetramethyl pipedine-1-oxyl radical (TEMPO)-mediated selective oxidation of the primary alcohol groups at C6 position from natural cellulose pulps treated with NaOH solution. Their adsorption properties for Cu2+ and Cd2+ in aqueous salt solutions were investigated. The results showed that the greater the carboxyl content and degree of substitution, the higher the value of the adsorption capacity. However, since the oxidized cellulose prepared from cellulose treated with 25% NaOH solution, having carboxyl content 14.98%, was partially soluble in aqueous solutions, the dissolution of this sample resulted in reduced metal-adsorption efficiency. The metal-adsorption of the oxidized celluloses followed the Langmuir adsorption isotherm. Compared with the oxidized cellulose having carboxyl content 5.12% from cellulose treated with 15% NaOH solution, the oxidized cellulose having carboxyl content 5.12% from cellulose treated with 25% NaOH solution has much stronger metal-adsorption capacity.