Removal of Aqueous Hg(II) by Polyaniline: Sorption Characteristics and Mechanisms

A polyaniline (PAN) prepared by chemical oxidation method was studied for Hg(II) removal from aqueous solutions. Batch adsorption results showed solution pH values had a major impact on mercury adsorption by this sorbent with optimal removal observed around pH 4−6. At both acidic and alkaline soluti...

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Bibliographic Details
Published in:Environmental science & technology 2009-07, Vol.43 (14), p.5223-5228
Main Authors: Wang, Jing, Deng, Baolin, Chen, Huan, Wang, Xiaorong, Zheng, Jianzhong
Format: Article
Language:English
Subjects:
Adsorption
Aniline Compounds - chemistry
Applied sciences
Aqueous solutions
Electrochemistry - methods
Environmental Processes
Exact sciences and technology
Humans
Hydrogen-Ion Concentration
Ions
Mercury
Mercury - chemistry
Molecular Structure
Nutrient removal
Oxidation
Oxidation-Reduction
Pollution
Sorption
Spectrum Analysis - methods
Water - chemistry
Water Pollutants, Chemical - chemistry
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Summary:A polyaniline (PAN) prepared by chemical oxidation method was studied for Hg(II) removal from aqueous solutions. Batch adsorption results showed solution pH values had a major impact on mercury adsorption by this sorbent with optimal removal observed around pH 4−6. At both acidic and alkaline solutions beyond this optimal pH window, sorption capacity of PAN was substantially lowered, with the impact less pronounced at pH above 6. Among the water constituents tested, only chloride and humic acid had significant inhibition on mercury removal due to competitive complexation. In the range of 0.02−0.2 M, ionic strength had less impact on Hg(II) removal by PAN while further increase in background electrolyte concentration to 1.0 M substantially decreased mercury removal. An adsorption mechanism was proposed by analyzing the XPS spectra of the key elements (N1s, Cl2p and Hg4f) on polyaniline surfaces and the change of its electrokinetic properties, both before and after Hg(II) adsorption. Specifically, at pH 5.5, it is likely that all the nitrogen-containing functional groups on the polymer matrix including imine, protonated imine and amine could be responsible for mercury adsorption, with imine having the highest affinity while the remaining two having similar strength to complex mercury.
ISSN:0013-936X
1520-5851
DOI:10.1021/es803710k