Amino-carboxyl cellulose for adsorption of Cd²⁺ and Pb²

An amino-carboxyl cellulose was synthesized using the grafting of glycine on the aldehyde cellulose through a Schiff base reaction for the adsorption of heavy metals with Cd²⁺ and Pb²⁺ as the representative. Higher affinity of the amino-carboxyl cellulose was found at pH 4.5-5.0 for Cd²⁺ and 4.0-5.5 for Pb²⁺. The equilibrium was achieved within 30 min. The adsorption capacities of amino-carboxyl cellulose (Cd^2+: 85.7 mg g^-1, Pb²⁺: 115.1 mg g^-1, Cu²⁺: 68.2 mg g^-1, Co²⁺: 60.1 mg g^-1, Ni²⁺ 48.5 mg g^-1 and Zn²⁺: 52.8 mg g^-1) at 30 °C were observed. A mild increase in the adsorption capacities of Cd²⁺ and Pb²⁺ from 15 to 45 °C was observed. Adsorption data correlated well with the Langmuir and pseudo-second order equations, illustrating chemisorption of Cd²⁺ and Pb²⁺ by the amino-carboxyl cellulose. The adsorption of the amino-carboxyl cellulose for Cd²⁺ and Pb²⁺ was a spontaneous and endothermic. The amino-carboxyl cellulose owned a high reusability after 4 cycles.