TY - JOUR
T1 - Selective adsorption of inorganic anions on unwashed and washed hexadecyl pyridinium-modified montmorillonite
AU - Luo, Wuhui
AU - Hirajima, Tsuyoshi
AU - Sasaki, Keiko
N1 - Funding Information:
Financial support was provided to KS by the Japan Society for the Promotion of Science (JSPS research fund (A) No. 16H02435). The authors appreciate it to Prof. Kwadwo Osseo-Asare at Pennsylvania State University for discussion on hydration energy of ions through the funding program “Progress 100” (World Premier International Researcher Invitation Program) in Kyushu University through operating expense grants of the Ministry of Education, Culture, Sports, Science, and Technology.
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2017/4/4
Y1 - 2017/4/4
N2 - Fourteen anions were selected to investigate their adsorption capacities and affinities to unwashed and washed hexadecyl pyridinium (HDPy)-modified montmorillonite (HDPy/Mt). Correlations between adsorption characteristics and anionic properties including radius and hydration energy were determined. With the exception of IO3−, H2AsO4−, and CrO42−, monovalent anions showed higher adsorption capacities and affinities to unwashed or washed HDPy/Mt than divalent anions, because the latter possess higher hydration energies. Unwashed HDPy/Mt demonstrated higher selectivity toward poorly hydrated monovalent anions because it presented a more hydrophobic environment, whereas strongly hydrated divalent anions more readily intercalate into the less hydrophobic washed HDPy/Mt. Hydration of the counter ion (Cl−) is the driving force for anion adsorption on HDPy/Mt. Higher energy consumption required to dehydrate divalent anions accounts for their lower affinity. Selectivity of HDPy/Mt to anions depends not only on anion size in different phases (from r1 in aqueous solution to r2 in the organic solvent-like HDPy/Mt), but also the dielectric constant of HDPy/Mt (ε2) after HDPy release.
AB - Fourteen anions were selected to investigate their adsorption capacities and affinities to unwashed and washed hexadecyl pyridinium (HDPy)-modified montmorillonite (HDPy/Mt). Correlations between adsorption characteristics and anionic properties including radius and hydration energy were determined. With the exception of IO3−, H2AsO4−, and CrO42−, monovalent anions showed higher adsorption capacities and affinities to unwashed or washed HDPy/Mt than divalent anions, because the latter possess higher hydration energies. Unwashed HDPy/Mt demonstrated higher selectivity toward poorly hydrated monovalent anions because it presented a more hydrophobic environment, whereas strongly hydrated divalent anions more readily intercalate into the less hydrophobic washed HDPy/Mt. Hydration of the counter ion (Cl−) is the driving force for anion adsorption on HDPy/Mt. Higher energy consumption required to dehydrate divalent anions accounts for their lower affinity. Selectivity of HDPy/Mt to anions depends not only on anion size in different phases (from r1 in aqueous solution to r2 in the organic solvent-like HDPy/Mt), but also the dielectric constant of HDPy/Mt (ε2) after HDPy release.
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U2 - 10.1016/j.seppur.2016.12.004
DO - 10.1016/j.seppur.2016.12.004
M3 - Article
AN - SCOPUS:85006355783
SN - 1383-5866
VL - 176
SP - 120
EP - 125
JO - Separation and Purification Technology
JF - Separation and Purification Technology
ER -
