Adsorption of nickel ions from seawater by modified chitosan

Abstract

Chitosan (CS) was modified by using sodium chloride as the porogen agent to remove nickel ions in seawater. The modified CS was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and pH_pzc analysis. The influence of pH, background electrolyte concentrations on nickel ions adsorption by CS and modified CS was investigated. The results showed that nickel ions adsorption capacity by CS and modified CS are greatly improve when background electrolyte concentration increase from 0 to 0.8556 mol/L, indicating the modified CS could be an excellent adsorbent to remove nickel ions from seawater. Langmuir, Freundlich, Redlich–Peterson, and Langmuir–Freundlich models were used to illustrate the isotherms of the adsorption process. The mechanism of the adsorption was a combination of electrostatic interaction and chemical adsorption. The nickel species distribution was predicted by Visual MINTEQ program, and the total content of Ni²⁺, NiOH⁺, and NiCl⁺ cation species increased with the increase of ion strength in aqueous, which could demonstrate the adsorption mechanism is dominantly an electrostatic interaction as well. The modified CS could be a potential material to remove nickel ions in pretreatment of seawater for mariculture or industrial applications.

Keywords:

• Nickel ions
• Seawater
• Adsorption
• Modified chitosan
• Isotherm
• Kinetic

Acknowledgment

Financial supports from the National High Technology Research and Development Program (“863” program) of China (2012AA06A115) are gratefully acknowledged.