Study On Preparation And Adsorption Properties Of Gellan Gum-Based Novel Adsorbents

A large number of wastewater containing uranium will be produced in the uranium purification and processing process.If not handled,the waste water will do great harm to environment and organisms.Therefore,it must get effective treatment before discharging.Compared with other methods,biosorption has been widely concerned owing to it has simple process and high removal efficiency.Also,the raw materials is low cast and accessible.However,there are some disadvantages of the existing adsorbent such as low adsorption capacity,poor mechanical properties.Therefore,it is necessary to develop a kind of new adsorbent with high adsorption capacity and high strength.Two kinds of adsorbents are prepared in this study,one is gellan gum loaded with calcium microsphere?GG-Ca?,and the other is carboxymethyl konjac glucomannan/gellan gum loaded with aluminum?CMKGM/GG-Al?.The adsorption properties and adsorption mechanism are studied,main contents are as follows:1.With gellan gum as the raw materials,anhydrous calcium chloride as cross linking agent,GG-Ca microsphere was prepared via electronic injection device.Effects of three factors on gel strength of the microsphere were investigated,and the adsorption capacities of GG-Ca microsphere were also investigated by batch experiments.3%of GG and 5%Ca Cl₂ and 5 m L ethyl acetate were prepared GG-Ca microsphere due to it has the largest gel strength.The maximum adsorption capacity of GG-Ca microsphere for uranium was 202.84 mg/g at p H 4,initial uranium concentration of 310 mg/g.The adsorption equilibrium was achieved at 12 h.The experimental data were well followed linear pseudo-second-order model and Freundlich model,and the adsorption process is spontaneous and endothermic.The regeneration rate was 83%after 5 cycles.The adsoption of uranium on GG-Ca adsorbent was realized through ion exchange.2.With gellan gum and carboxymethyl konjac glucomannan as the raw materials,aluminum Chloride Hexahydrate as cross linking agent,CMKGM/GG-Al microsphere was prepared via electronic injection device.Effect of mass ratio of CMKGM and GG,mass concentration of aluminum Chloride Hexahydrate on gel strength were investigated,and the adsorption capacities of CMKGM/GG-Al microsphere were also investigated.Results showed that the maximum gel strength of CMKGM/GG-Al microsphere was achieved in the condition that 5%of Al³⁺concentration and 4:1 of GG/CMKGM mass ratio.Besides,the effect of removal uranium is also best under this condition.The maximum adsorption capacity of CMKGM/GG-Al microsphere for uranium was98.10 mg/g at p H 6,initial uranium concentration of 100 mg/g.The adsorption process is in line with the Langmuir model and linear pseudo-second-order quation.The investigation of thermodynamics showed that adsorption process is spontaneous and endothermic.The regeneration rate was 95.91%after 5 cycles.The adsoption of uranium on CMKGM-GG-Al adsorbent was realized through ion exchange.3.The dynamic adsorption properties were studied with CMKGM/GG-Al microsphere.The effects of bed depths,initial uranium concentration and flow rates on breakthrough curve were investigated.Results showed that breakthrough point and depletion point is in advance with the increase of flow rates and the initial uranium concentration.And the reakthrough point and depletion point was delay with the increase of bed depths.