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Preparation of Double Carboxylic Corn Stalk Gels and Their Adsorption Properties Towards Rare Earths (III)

Wang, Fuchun, Zhao, Junmei, Liu, Huizhou, Luo, Yuan, Wang, Wankun
Waste and biomass valorization 2018 v.9 no.10 pp. 1945-1954
adsorbents, adsorption, biosorbents, cation exchange, corn stover, equations, gels, metal ions, oxidation, rare earth elements, thermodynamics
A novel biosorbent, corn stalk gels with double carboxylic groups synthesized by two oxidation steps (the double carboxylic groups modified adsorbent is abbreviated as DCCS-2), was prepared, characterized, and applied for the recovery of rare earths (III) from the nitric media. For the whole lanthanides, it exhibits a distinct “tetrad effect” with the increase of atomic numbers. Taking Nd(III) as a representative element, the adsorption capacity, kinetics, selectivity and mechanism were investigated. Thermodynamics and kinetic fittings were found to abide by Langmuir and pseudo-second-order rate equations and the corresponding parameters were calculated. The maximum adsorption capacity was calculated to be 2.44 mol/kg at 298 K for DCCS-2. Results showed that the double carboxylic groups played an important role for improving the adsorption capacity, e.g. the adsorption capacity of Nd(III) by DCCS-2 increased to 53.5 times compared to the raw corn stalk. Furthermore, DCCS-2 also shows a good selectivity between Nd(III) and many non-rare earth metal ions. The cation exchange is proposed to be the possible adsorption mechanism.