A comparative study on selective adsorption of metal ions using aminated adsorbents

It is well-known that chitosan consists of amino groups for the chelation of metal ions while NH2-MCM-41 has excellent adsorption selectivities for metals. This work compares both adsorption capacities and selectivities of chitosan and NH2-MCM-41. It has been found that chitosan has adsorption capacities of 1.76 mmol/g, 1.03 mmol/g and 1.30 mmol/g for Cu2+, Ni2+ and Zn2+ respectively whereas NH2-MCM-41 has adsorption capacity of 1.52 mmol/g, 0.8 mmol/g and 0.83 mmol/g for Cu2+, Ni2+ and Zn2+. The higher adsorption capacity in chitosan is attributed to its higher loading of amine groups. The single component adsorption isotherms were well-fitted using Freundlich model. The binary adsorptions of Cu2+–Zn2+ and Ni2+–Zn2+ systems showed similar adsorption selectivities for both adsorbents. However, chitosan has no preferential adsorption for Ni2+–Zn2+ system while NH2-MCM-41 has a good selectivity towards Zn2+. It is believed that the difference can be attributed to the heterogeneous surface of chitosan due to its organic nature. The multi-component adsorptions were best described by a multicomponent extended Freundlich model. Despite the surface functional group, this work indicates the importance of the adsorbent support on selective adsorption.

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► Aminated adsorbents are compared in multicomponent adsorptions of metal ions.
► NH2-MCM-41 shows superior adsorption selectivity performance.
► Chitosan shows selectivity for Cu2+ in multicomponent systems but not Ni–Zn system.