Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations
The adsorption isotherms of M 2+ ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ‐MnO 2 , was converted to the K + form prior to adsorption and about 1.5 mol K + ions were released per mol of M 2+ ions adsorbed. The adsorption capacity at a given...
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| Veröffentlicht in: | Journal of chemical technology and biotechnology (1979) 1979, Vol.29 (3), p.127-134 |
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| container_title | Journal of chemical technology and biotechnology (1979) |
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| creator | Gray, Malcolm J. Malati, Mounir A. |
| description | The adsorption isotherms of M
2+
ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ‐MnO
2
, was converted to the K
+
form prior to adsorption and about 1.5 mol K
+
ions were released per mol of M
2+
ions adsorbed. The adsorption capacity at a given temperature increased in the series: Mg
2+
< Ca
2+
≦ Sr
2+
< Ba
2+
. This was explained by an ion exchange mechanism between hydrated ions: K
+
ions in the outer Helmholtz layer and M
2+
ions in the bulk of the solution. The radii of the hydrated ions decreased in the series: Mg
2+
> Ca
2+
> Sr
2+
> Ba
2+
. The adsorption of M
2+
ions at pH values below the point of zero charge (pH 3.3) was significant for Mg
2+
ions only. Although adsorption was not strictly reversible, the results fitted the Langmuir isotherm and ‘apparent heats of adsorption’,
Q
, were calculated. The endothermic heats (
Q
= 20,18, 11 and 5 kJ mol
−1
for Mg
2+
, Ca
2+
, Sr
2+
and Ba
2+
adsorption respectively) indicated positive entropy contributions which are expected for the adsorption mechanism suggested. The decrease in
Q
down the alkaline‐earth group was correlated to the entropy effects and to the hydration numbers of the cations. |
| doi_str_mv | 10.1002/jctb.503290302 |
| format | Article |
| fullrecord | <record><control><sourceid>istex_cross</sourceid><recordid>TN_cdi_crossref_primary_10_1002_jctb_503290302</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><sourcerecordid>ark_67375_WNG_C383FPR1_F</sourcerecordid><originalsourceid>FETCH-LOGICAL-c122F-39fd4b24a8a31c9333694ecf490cb9c375f59d2eab79b6997fdcb76cf8b97433</originalsourceid><addsrcrecordid>eNpNkN1KAzEQRoMoWKu3XucFsiaZ_ctlKW4tFBUp6F1IsonddrupyRba9_I5fCZbleLVwMyc74OD0C2jCaOU3y1Nr5OMAhcUKD9DAyYgI6xkb-doQFnKCYUsv0RXMS4phZTndIDqUR192PSN77ALfo3Vx9b6bcTRt9ufrd7jr0-yVt276my0uG78rqktnib4H-sd7hcWq3al2qazxKrQL7BRx2O8RhdOtdHe_M0hmlf38_EDmT1NpuPRjBjGeUVAuDrVPFWlAmYEAOQitcalghotDBSZy0TNrdKF0LkQhauNLnLjSi2KFGCIkt9YE3yMwTq5Cc1ahb1kVB4VyaMieVJ0AMgv0MTe7k7fKqxkXhzq5OvjRI6hhOr5hckKvgHTrGuf</addsrcrecordid><sourcetype>Aggregation Database</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype></control><display><type>article</type><title>Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations</title><source>Wiley Online Library Journals Frontfile Complete</source><creator>Gray, Malcolm J. ; Malati, Mounir A.</creator><creatorcontrib>Gray, Malcolm J. ; Malati, Mounir A.</creatorcontrib><description>The adsorption isotherms of M
2+
ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ‐MnO
2
, was converted to the K
+
form prior to adsorption and about 1.5 mol K
+
ions were released per mol of M
2+
ions adsorbed. The adsorption capacity at a given temperature increased in the series: Mg
2+
< Ca
2+
≦ Sr
2+
< Ba
2+
. This was explained by an ion exchange mechanism between hydrated ions: K
+
ions in the outer Helmholtz layer and M
2+
ions in the bulk of the solution. The radii of the hydrated ions decreased in the series: Mg
2+
> Ca
2+
> Sr
2+
> Ba
2+
. The adsorption of M
2+
ions at pH values below the point of zero charge (pH 3.3) was significant for Mg
2+
ions only. Although adsorption was not strictly reversible, the results fitted the Langmuir isotherm and ‘apparent heats of adsorption’,
Q
, were calculated. The endothermic heats (
Q
= 20,18, 11 and 5 kJ mol
−1
for Mg
2+
, Ca
2+
, Sr
2+
and Ba
2+
adsorption respectively) indicated positive entropy contributions which are expected for the adsorption mechanism suggested. The decrease in
Q
down the alkaline‐earth group was correlated to the entropy effects and to the hydration numbers of the cations.</description><identifier>ISSN: 0142-0356</identifier><identifier>EISSN: 1935-181X</identifier><identifier>DOI: 10.1002/jctb.503290302</identifier><language>eng</language><publisher>London: John Wiley & Sons, Ltd</publisher><ispartof>Journal of chemical technology and biotechnology (1979), 1979, Vol.29 (3), p.127-134</ispartof><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c122F-39fd4b24a8a31c9333694ecf490cb9c375f59d2eab79b6997fdcb76cf8b97433</citedby><cites>FETCH-LOGICAL-c122F-39fd4b24a8a31c9333694ecf490cb9c375f59d2eab79b6997fdcb76cf8b97433</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,776,780,4010,27900,27901,27902</link.rule.ids></links><search><creatorcontrib>Gray, Malcolm J.</creatorcontrib><creatorcontrib>Malati, Mounir A.</creatorcontrib><title>Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations</title><title>Journal of chemical technology and biotechnology (1979)</title><addtitle>J. Chem. Technol. Biotechnol</addtitle><description>The adsorption isotherms of M
2+
ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ‐MnO
2
, was converted to the K
+
form prior to adsorption and about 1.5 mol K
+
ions were released per mol of M
2+
ions adsorbed. The adsorption capacity at a given temperature increased in the series: Mg
2+
< Ca
2+
≦ Sr
2+
< Ba
2+
. This was explained by an ion exchange mechanism between hydrated ions: K
+
ions in the outer Helmholtz layer and M
2+
ions in the bulk of the solution. The radii of the hydrated ions decreased in the series: Mg
2+
> Ca
2+
> Sr
2+
> Ba
2+
. The adsorption of M
2+
ions at pH values below the point of zero charge (pH 3.3) was significant for Mg
2+
ions only. Although adsorption was not strictly reversible, the results fitted the Langmuir isotherm and ‘apparent heats of adsorption’,
Q
, were calculated. The endothermic heats (
Q
= 20,18, 11 and 5 kJ mol
−1
for Mg
2+
, Ca
2+
, Sr
2+
and Ba
2+
adsorption respectively) indicated positive entropy contributions which are expected for the adsorption mechanism suggested. The decrease in
Q
down the alkaline‐earth group was correlated to the entropy effects and to the hydration numbers of the cations.</description><issn>0142-0356</issn><issn>1935-181X</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1979</creationdate><recordtype>article</recordtype><recordid>eNpNkN1KAzEQRoMoWKu3XucFsiaZ_ctlKW4tFBUp6F1IsonddrupyRba9_I5fCZbleLVwMyc74OD0C2jCaOU3y1Nr5OMAhcUKD9DAyYgI6xkb-doQFnKCYUsv0RXMS4phZTndIDqUR192PSN77ALfo3Vx9b6bcTRt9ufrd7jr0-yVt276my0uG78rqktnib4H-sd7hcWq3al2qazxKrQL7BRx2O8RhdOtdHe_M0hmlf38_EDmT1NpuPRjBjGeUVAuDrVPFWlAmYEAOQitcalghotDBSZy0TNrdKF0LkQhauNLnLjSi2KFGCIkt9YE3yMwTq5Cc1ahb1kVB4VyaMieVJ0AMgv0MTe7k7fKqxkXhzq5OvjRI6hhOr5hckKvgHTrGuf</recordid><startdate>1979</startdate><enddate>1979</enddate><creator>Gray, Malcolm J.</creator><creator>Malati, Mounir A.</creator><general>John Wiley & Sons, Ltd</general><scope>BSCLL</scope><scope>AAYXX</scope><scope>CITATION</scope></search><sort><creationdate>1979</creationdate><title>Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations</title><author>Gray, Malcolm J. ; Malati, Mounir A.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c122F-39fd4b24a8a31c9333694ecf490cb9c375f59d2eab79b6997fdcb76cf8b97433</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1979</creationdate><toplevel>online_resources</toplevel><creatorcontrib>Gray, Malcolm J.</creatorcontrib><creatorcontrib>Malati, Mounir A.</creatorcontrib><collection>Istex</collection><collection>CrossRef</collection><jtitle>Journal of chemical technology and biotechnology (1979)</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Gray, Malcolm J.</au><au>Malati, Mounir A.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations</atitle><jtitle>Journal of chemical technology and biotechnology (1979)</jtitle><addtitle>J. Chem. Technol. Biotechnol</addtitle><date>1979</date><risdate>1979</risdate><volume>29</volume><issue>3</issue><spage>127</spage><epage>134</epage><pages>127-134</pages><issn>0142-0356</issn><eissn>1935-181X</eissn><abstract>The adsorption isotherms of M
2+
ions (M = Mg, Ca, Sr or Ba) were determined at pH 7.0 and at different temperatures. The adsorbent, δ‐MnO
2
, was converted to the K
+
form prior to adsorption and about 1.5 mol K
+
ions were released per mol of M
2+
ions adsorbed. The adsorption capacity at a given temperature increased in the series: Mg
2+
< Ca
2+
≦ Sr
2+
< Ba
2+
. This was explained by an ion exchange mechanism between hydrated ions: K
+
ions in the outer Helmholtz layer and M
2+
ions in the bulk of the solution. The radii of the hydrated ions decreased in the series: Mg
2+
> Ca
2+
> Sr
2+
> Ba
2+
. The adsorption of M
2+
ions at pH values below the point of zero charge (pH 3.3) was significant for Mg
2+
ions only. Although adsorption was not strictly reversible, the results fitted the Langmuir isotherm and ‘apparent heats of adsorption’,
Q
, were calculated. The endothermic heats (
Q
= 20,18, 11 and 5 kJ mol
−1
for Mg
2+
, Ca
2+
, Sr
2+
and Ba
2+
adsorption respectively) indicated positive entropy contributions which are expected for the adsorption mechanism suggested. The decrease in
Q
down the alkaline‐earth group was correlated to the entropy effects and to the hydration numbers of the cations.</abstract><cop>London</cop><pub>John Wiley & Sons, Ltd</pub><doi>10.1002/jctb.503290302</doi><tpages>8</tpages></addata></record> |
| fulltext | fulltext |
| identifier | ISSN: 0142-0356 |
| ispartof | Journal of chemical technology and biotechnology (1979), 1979, Vol.29 (3), p.127-134 |
| issn | 0142-0356 1935-181X |
| language | eng |
| recordid | cdi_crossref_primary_10_1002_jctb_503290302 |
| source | Wiley Online Library Journals Frontfile Complete |
| title | Adsorption from aqueous solution by δ-manganese dioxide I. Adsorption of the alkaline-earth cations |
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