Preparation Of Hydroxamic Modified Calix[6]arene Cross-linked Chitosan And The Selection Extraction Performance Of U(Ⅵ)

Calixarenes is easy to synthesis, which is the third generation supramolecular compounds. The structural characteristics of easy modification, and modification of calixarenes and their derivatives is the research hotspot in recent years. Chitosan, the only naturally basic polysaccharide in the nature, which is non-toxic, readily biodegradable, and will not pollute the environment, so it can be used as a green, environmentally radionuclide decontamination materials.5,11,17,23,29,35-hexacarboxy-37,38,39,40,41,42-hexa-methoxyhydroxamic calix[6]arene(HHMHC) was synthesized by modifying p-hydroxybenzoic acid. Then HHMHC was used to synthesized 5,11,17,23,29,35-hexa-formyl-chloride-37,38,39,40,41,42-hexa-methoxy-hydroxamic calix[6]arene(HFCHMHC) by reacting with thionyl chloride. CHD-CTS was synthesized through chloride reacting with chitosan.HHMHC was used as extractant and CHD-CTS was used as absorbent to remove U(VI) from radioactive wastewater and Cu2+and Ni2+ from heavy metal wastewater after soaking in alkali liquor. The influences of different factors on the extraction and absorbtion of U(VI), Cu2+and Ni2+with HHMHC and CHD-CTS were investigated, and the complexing capacity of HHMHC with different kinds of cation were studied. Otherwise, The kinetic and thermodynamic of the extraction and adsorption process were analyzed respectively, and the adsorption mechanism was explored through SEM、FTIR、EDS. The experiment results are as follows:1) HHMHC has the high coordination ability with UO22+、Na+、Cu2+、Pb2+ and Ni2+. The coordination ratio between HHMHC with uranium is 3:2, while between Cu2+ and Ni2+ is 3:7, 3:2, respectively. which were determined by Job’s method.2) HHMHC could remove Ni2+, Cu2+, UO22+ effectly. When under the experiment conditions of 30℃, an extractant concentration of 2×10-4mol L-1, and an initial Ni2+ and Cu2+ concentration of 5mg/L, the optimal conditions were found to be 30 min of contact time, p H=6.0(Ni2+and U(VI)), 5.0(Cu2+). The percentage removal of Ni2+ and Cu2+ extracted by HHMHC was higher than 92% and 89% at the biginning of 15 min. When the react time is 30 min, the maximum extraction distribution ratio was over 10.3) The results showed that when the p H was 6.0, the effect adsorption of uranium can reach the best level. The rate of removal of uranium was improved as the time increased. And as the amount of adsorbent increased, the removal of U(VI) became higher. However, it was decreased by the increased initial concentration. The removal of uranium was less affected by cations of Ca2+ and Mn2+ ions, but C2O42-and CO32- ions had a bigger influence of the removal of U(VI).4) The kinetics of adsorption process could fit well with the pseudo-second-order model and Freundlich isotherm model. In the absorbtion process, the negative values of Gibbs free energy(ΔG0) revealed this absorbtion was spontaneous. Meanwhile, the value of enthalpy(ΔH0) was negative, indicating that the absorbtion reaction was exothermic progress.