Preparation Of Naturnal Magnetic Chitosan Composite Materials For The Adsorption Of Molybdenum And Rhenium

In this thesis, Eriocheir sinesis crab shells were used as raw materials to preraredifferent characteristics of adsorbents. The adsorption behaviors of the adsorbentstowards rhenium and molybdenum were investigated systematically, such as theadsorption properties of kinetics and thermodynamics、the adsorption mechanisms.The specified studies were as follows:First of all, the crab shell chitin gel (CSC) was prepared from Eriocheir sinesiscrab shells, which was treated with HCl to remove minerals. The CSC gel wascharacterized by FTIR、SEM, which was confirmed as α-chitin. The CSC gel showeda high affinity for Mo(VI) comparing with other adsorbents, and the maximumadsorption capacity was evaluated as252.27mg/g in case of pH1. The experimentalresults fitted satisfactory to the Langmuir isotherm. Biosorption kinetics data weresuccessfully modeled using nonlinear pseudo-second-order model. Moreover, itsexcellent adsorption properties and applicability for Mo(VI) were demonstrated bythe recovery and separation of Mo(VI) from Cu or/and Fe binary and ternarymixtures.Secondly, the naturnal magnetic chitosan composite material (FCS) wereprepared using Fe3O4as cores and chitosan as a polymeric shell prepared fromEriocheir sinesis crab shells. Compared with chitosan, the FCS gel showed a highaffinity for Mo(VI) and Re(VII), and the maximum adsorption capacity of Mo(VI)and Re(VII) was evaluated as261.04and57.79mg/g in case of pH4. Theadsorption behavior obeys the Langmuir model. The recovery rate of Mo(VI) andRe(VII) was100%eluting by20%ammonium and10%ammonium thiocyanaterespectively.Thirdly, the naturnal magnetic chitosan composite material were modified witheight different kinds of amino. Compared with FCS, the amino adsorbents showedhigher affinity for Re(VII). Magnetic chitosan modified with di-2-ethylhexylamine(FCS-DIOA) exhibited a greater sorption capacity and a marked preference forRe(VII) in case of pH10. Its excellent adsorption properties and applicability for Re(VII) were demonstrated by the recovery and separation of Re(VII) from Mo(VI)and Re(VII) binary mixtures. FCS-DIOA gel can be used repeatedly at least fivetimes without significantly losing the adsorption capacity for rhenium.