Preparation,Characterization And Adsorption Properties Of Magnetic Alginate/Rare Earth Biomacromolecule Gel Spheres Composites

The printing and dyeing industry is not only a big water consumer,but also ranks second and fourth in the total amount of industrial waste water and pollutants in China,which is one of the key polluting industries in China.Therefore,the development of environmental-friendly and efficient dye wastewater treatment technology has become the focus of the current environmental protection industry.Sodium alginate?SA?is a kind of rich marine biological resource,which has good hydrophilicity,gelation,non-toxic side effect,biocompatibility and biodegradability,and contains a large number of active groups in the molecular chain,making it can interact with various dye molecules.Hence SA can be used as adsorption material in dye wastewater treatment.In this study,two new magnetic sodium alginate-rare earth polymer gel spheres,Fe₃O₄@SA/Ce and Fe₃O₄@SA/Y,were prepared by crosslinking rare earth?RE?ions with SA and magnetic Fe₃O₄ using SA as the raw material.XRD,SEM-EDS,FT-IR,VSM and XPS were used to characterize the morphology,element content,specific surface area and magnetic properties of Fe₃O₄@SA/RE.Five direct dyes such as Direct Red12B?DR 12B?,Direct Orange S?DO S?,Direct Dark Brown M?DDB M?,Direct Fast-Turquoise Blue GL?DFB GL?and Direct Dark Green NB?DG NB?were used as adsorption objects,the preparation and adsorption conditions of two Fe₃O₄@SA/RE were optimized and the adsorption kinetics,adsorption thermodynamics and related adsorption mechanism were investigated.The results in detail were stated as follows:?1?The optimum conditions for the preparation of Fe₃O₄@SA/Ce adsorbent were that Fe₃O₄ with mass concentration of 3g/L was addied into SA solution at 35g/L,stirred uniformly and then dispersed by ultrasound for 30 min,the mixture was uniformly dropped into Ce?NO₃?₃solution with mass concentration of 35g/L through a syringe.After crosslinking for 180 min at 25?,the gel balls were removed,washed to neutral and then dried,and Fe₃O₄@SA/Ce gel balls adsorbent were obtained.The optimum preparation conditions of Fe₃O₄@SA/Y adsorption material are:3g/L Fe₃O₄ solution was addied into 30g/L SA solution,the mixture was uniformly mixed and then dispersed by ultrasound for 30 min.Then the mixture was dripped into Y?NO₃?₃ solution with a mass concentration of 35g/L by a syringe.After crosslinking for 180 min at 25?,the gel spheres were removed and rinsed to be neutral.After dried,the Fe₃O₄@SA/Y adsorption material was obtained.?2?Fe₃O₄@SA/Ce is suitable for the adsorption of DR 12B and DO S and the optimal adsorption conditions are that the dosage of Fe₃O₄@SA/Ce dosage was 0.1g,the natural pH and initial concentration of DR 12B and DO S were 8.90,9.08,2000 and 3000 mg/L respectively,the adsorption reaction time was 120 min and 90 min at25?the adsorption capacities and removal rates of DR 12B and DO S by Fe₃O₄@SA/Ce could reach 464 mg/g,735mg/g,92.7%and 97.9%,respectively.The suitable conditions of DFB GL,DG NB and DDB M adsotpyion onto Fe₃O₄@SA/Y were that Fe₃O₄@SA/Y dosage were 0.1g,0.1g and0.08g,respectively,the Natural pH value and initial concentration of DFB GL,DG NB and DDB M were 9.79,8.20 and 7.90 mg/L,1200 mg/L and 2000mg/L respectively.The adsorption reaction time and temperature were 120min and 25?,respectively.The adsorption capacities and removal rates of Fe₃O₄@SA/Y for DFB GL,DG NB and DDB M could reach 282,282,563mg/g,94.1,94.4and 90.2%,respectively.By SEM?XRD?EDS?FT-IR?VSM?XPS characterization the results show that:SA is composed of various rod-shaped and block-shaped irregular debris particles,two Fe₃O₄@SA/RE adsorbents prepared by cross-linking reaction of with rare earth ions Ce?III?and Y?III?after added Fe₃O₄,respectively,are meso-porous gel composites with a"cauliflower"-like ridge structure on the surface,the banded furrows are closely connected,but the surface morphology of the two kinds of gel spheres is different Fe₃O₄@SA/RE gel spheres have good magnetic response and can realize the rapid separation from the water bodyAfter adsorption of pollutants,Which will not cause secondary pollution to the environment.?4?Kinetic results show that the adsorption processes of DR 12B,Do S,DFB GL,DG NB and DDB M by two Fe₃O₄@SA/RE adsorbents at different temperatures?298K,313K,328K?are in accordance with the pseudo-second-order kinetic rate model,the adsorption equilibrium of DO S and other four direct dyes can be reached within 90 min and 120 min,respectively.The adsorption rate is primarily affected by intraparticle diffusion,Fe₃O₄@SA/Ce apparent adsorption activation energy E_a values for DR 12B and DO S was 32 and 124 kJ/mol,respectively.The apparent adsorption activation energy E_a values of Fe₃O₄@SA/Y adsorption DFB GL?DG NB and DDB M are 32,44 and 36 kJ/mol,respectively.?5?The results of isothermal adsorption showed that the adsorption behavior of five direct dyes onto two Fe₃O₄@SA/RE adsorbents namely,DR12B,DO S,DFB GL,DG NB and DDB M,were in accordance with Freundlich model,and 1/n was less than 1,the adsorption process was easy to carry out.?6?The Adsorption thermodynamics results show that:At different temperatures?298K,313K,328K?,the negative values of the free energy change?G,negative values of enthalpy change?H and positive values of enthalpy change?S for DR 12B and DO S on Fe₃O₄@SA/Ce,indicating that the adsorption is a spontaneous exothermic reaction with increased confusion.The?G<0,?H>0,?S>0 of Fe₃O₄@SA/Y adsorption DFB GL,DG NB and DDB M,which indicate that the adsorption of Fe₃O₄@SA/Y gel spheres to three direct dyes was endothermic and spontaneous reaction with increased confusion.The analysis of FT-IR and XPS patterns before and after adsorption of five direct dyes by binding Fe₃O₄@SA/RE show that:The main adsorption were electrostatic adsorption and hydrogen bond adsorption.In this study,the prepared Fe₃O₄@SA/Ce and Fe₃O₄@SA/Y composite adsorbents have the advantages of high efficiency and environmental protection,simple preparation,low cost and excellent adsorption performance.The results provide a theoretical reference for the high value application of SA and rare earth ions in wastewater treatment,and hope to provide a new way for the treatment of direct dye wastewater.