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The adsorption of chromium (VI) ions from aqueous solution by ethylenediamine-modified cross-linked magnetic chitosan resin (EMCMCR) was studied in a batch adsorption system. Chromium (VI) removal is pH dependent and the optimum adsorption was observed at pH 2.0. The adsorption rate was extremely fast and the equilibrium was established within 6-10min. The adsorption data could be well interpreted by the Langmuir and Temkin model. The maximum adsorption capacities obtained from the Langmuir model are 51.813mgg(-1), 48.780mgg(-1) and 45.872mgg(-1) at 293, 303 and 313K, respectively. The adsorption process could be described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved in the present case. Thermodynamic parameters revealed the feasibility, spontaneity and exothermic nature of adsorption. The sorbents were successfully regenerated using 0.1N NaOH solutions.

This work focused on U(VI) biosorption using suspended Rhizopus arrihizus . To understand the biosorption process, the tolerance of the strain to U(VI) and the effects of solution pH, initial U(VI) concentration, temperature, and contact time on U(VI) removal were investigated in batch systems. The results demonstrated that R. arrihizus can grow normally in 200 mg L −1 uranium-contained medium. Optimum biosorption was observed at solution pH 4.0 and the maximum biosorption capacity (112.2 mg g −1 ) was obtained at initial U(VI) concentration of 200 mg L −1 . The biosorption process appeared to be temperature independent. Biosorption equilibrium was established within 90 min and the pseudo second-order model was found to fit accurately with the experimental data. FT-IR analysis and SEM morphology indicated that the structure of the strain remained integral after biosorption. Amino group plays an important role in the biosorption process, hydroxyl and carboxyl groups are also involved in U binding.

This study focuses on developing a new method to remove uranium from aqueous solution. Chitosan and ferrous ions were used together to remove uranium ions from aqueous solution. Through two-step pH adjustment, the uptake behavior of chitosan and ferrous ions toward uranium in aqueous solution using batch systems was studied in different experimental conditions. The experimental results indicated that the removal of uranium by the synergetic effect of chitosan and ferrous ions was more effective than the way of adsorbing uranium ions by chitosan alone. Under the given experimental conditions, the concentration of the residual uranium in the effluent after the chitosan and ferrous ion treatment could meet the discharge standard (

In this paper, we have presented a new method to remove Cr (VI) ions from aqueous solution. Chitosan and ferrous ions were added together to the chromium-contained solution, through two-step pH adjust, 0.5 g•l-1 chitosan and 2.0 g•l-1 FeSO4•7H2O could reduce Cr (VI) ions from 100 mg•l-1 to 0.01 mg•l-1. As compared with chitosan and ferrous alone used to remove Cr (VI), for 100 mg•l-1 Cr (VI) solution, the maximum of percentage removal of Cr (VI) by chitosan reached 94.08% when the dosage was up to 3.0 g•l-1 , ferrous ions can remove 99.96% Cr (VI) ions when the dosage was up to 3.0 g•l-1. The experimental results showed that the method of removal Cr (VI) by chitosan cooperated with ferrous ions was of great application prospect due to its high removal rate, quick removal velocity and less sludge volume.

Biosorption of uranium (VI) ions by immobilized Aspergillus fumigatus beads was investigated in a batch system. The influences of solution pH, biosorbent dose, U (VI) concentration, and contact time on U (VI) biosorption were studied. The results indicated that the adsorption capacity was strongly affected by the solution pH, the biosorbent dose and initial U (VI) concentration. Optimum biosorption was observed at pH 5.0, biosrobent dose (w/v) 2.5%, initial U (VI) concentration 60 mg L −1 . Biosorption equilibrium was established in 120 min. The adsorption process conformed to the Freunlich and Temkin isothermal adsorption models. The dynamic adsorption model conformed to pseudo-second order model.