Study On Synthesis Of Magnetic Chitosan/Bentonite Composite Adsorbent And Its Application For Cu²⁺ Adsorption

In this research, a magnetic chitosan/bentonite composite with potential in rapid solid-liquid separation through a magnetic field was synthesized with bentonite, chitosan and Fe₃O₄. Characterization of the composite was assayed with SEM, XRD, FTIR, VSM and so on. The results showed that the optimum preparation of the composite were that the mass ratio of chitosan/bentonite at 1:10, the mass ratio of Fe₃O₄/bentonite at 1:10, the p H value of chitosan solution at 6.0, the reaction time at 6h, the reaction temperature at 50?, respectively. Surface area analysis showed that the special surface area of the composite was 32.51m2/g which was higher than 27.74m2/g of bentonite. The SEM analysis showed that the composite had more microporous structure. The XRD analysis showed that the crystal spacing of the composite was 1.60 nm which was larger than 1.46 nm of bentonite.It also showed that the chitosan had been intercalated into the layer of bentonite. The FTIR analysis showed that the chitosan and bentonite formed chemical bonds in the composite. The VSM analysis showed that the saturation magnetization of the composite reached to 87.30emu/g, which could make the composite achieve the rapid solid-liquid separation through a magnetic field.The adsorption of Cu²⁺ from aqueous solution onto the composite was investigated as a function of various factors with batch experiments. The results indicated that adsorption of Cu²⁺ on the compsite strongly depended on the p H value. The adsorption efficiency of Cu²⁺ on the composite increased with the increase of the p H and the dosage of the composite. It could reach to 98.51% which meeted the state wastewater discharge standards under the conditions of the initial concentration of Cu²⁺ at 30 mg/L, p H at 6.0 and adsorbent dosage at 7.2g/L. It could reach to 91.84% after five minutes adsorption and get the adsorption equilibrium after reacting for 6h. The coexisting ions had a great influence on the adsorption efficiency of Cu²⁺ and the order of their interference was: Mg2+>K+>Na+.The adsorption kinetics and isotherm of Cu²⁺ onto the composite followed the pseudo-second-order and Langmiur model, respectively. What`s more, the reaction activation energy Ea=26.02 k J/mol which could primarily prove that the adsorption of Cu²⁺ on the composite was chemical adsorption, ?S=50.38 k J/mol, ?H=11.61 k J/mol, ?G<0. And the thermodynamic parameters studies revealed that the adsorption process was spontaneous and endothermic.The mechanism of removal of Cu²⁺ using the composite relies mainly on it's ion exchange reaction, so as to achieve the purpose of adsorption of Cu²⁺.