Editing Isoelectric point (section)

== Ceramic materials ==
The isoelectric points (IEP) of metal oxide ceramics are used extensively in material science in various aqueous processing steps (synthesis, modification, etc.).  In the absence of chemisorbed or physisorbed species particle surfaces in aqueous suspension are generally assumed to be covered with surface hydroxyl species, M-OH (where M is a metal such as Al, Si, etc.).<ref name="ref2pineapple">
{{cite journal
| last1=Hanaor
| first1=D.A.H.
| last2=Michelazzi
| first2=M.
| last3=Leonelli
| first3=C.
| last4=Sorrell
| first4=C.C.
| title= The effects of carboxylic acids on the aqueous dispersion and electrophoretic deposition of ZrO<sub>2</sub>
| journal= Journal of the European Ceramic Society
| year=2012
| volume=32
| issue=1
| pages=235–244
| doi=10.1016/j.jeurceramsoc.2011.08.015| arxiv=1303.2754
| s2cid=98812224
}}</ref> At pH values above the IEP, the predominant surface species is M-O<sup>−</sup>, while at pH values below the IEP, M-OH<sub>2</sub><sup>+</sup> species predominate. Some approximate values of common ceramics are listed below:<ref>{{cite journal | last1 = Haruta | first1 = M | year = 2004 | title = Nanoparticulate Gold Catalysts for Low-Temperature CO Oxidation | journal = Journal of New Materials for Electrochemical Systems | volume = 7 | pages = 163–172 }}</ref><ref>[http://www.iupac.org/publications/pac/1978/pdf/5009x1211.pdf Brunelle JP (1978). 'Preparation of Catalysts by Metallic Complex Adsorption on Mineral Oxides'. ''Pure and Applied Chemistry'' vol. 50, pp. 1211–1229.]</ref>
{| class="wikitable sortable"
|-
! Material
! IEP
|-
| [[tungsten(VI) oxide|WO<sub>3</sub>]]<ref name="Kosmulski"/>
| 0.2–0.5
|-
| [[antimony(V) oxide|Sb<sub>2</sub>O<sub>5</sub>]]<ref name="Kosmulski"/>
| <0.4–1.9
|-
| [[vanadium(V) oxide|V<sub>2</sub>O<sub>5</sub>]]<ref name="Kosmulski"/><ref name="Jolivet"/>
| 1–2 (3)
|-
| [[manganese(IV) oxide|δ-MnO<sub>2</sub>]]
| 1.5
|-
| [[silicon dioxide|SiO<sub>2</sub>]]<ref name="Kosmulski"/>
| 1.7–3.5
|-
| [[silicon carbide|SiC]]<ref>U.S. Patent 5,165,996</ref>
| 2–3.5
|-
| [[tantalum(V) oxide|Ta<sub>2</sub>O<sub>5</sub>]]<ref name="Kosmulski"/>
| 2.7–3.0
|-
| [[titanium(IV) oxide|TiO<sub>2</sub>]]<ref name=epd>[https://arxiv.org/ftp/arxiv/papers/1303/1303.2742.pdf Anodic Aqueous Electrophoretic Deposition of Titanium Dioxide Using Carboxylic Acids as Dispersing Agents] Journal of the European Ceramic Society, 31(6), 1041-1047, 2011</ref>
| 2.8–3.8
|-
| γ-[[Iron (III) oxide|Fe<sub>2</sub>O<sub>3</sub>]]<ref name="Kosmulski"/>
| 3.3–6.7
|-
| [[tin(IV) oxide|SnO<sub>2</sub>]]<ref name="Lewis">{{cite journal | last1 = Lewis | first1 = JA | year = 2000 | title = Colloidal Processing of Ceramics | doi = 10.1111/j.1151-2916.2000.tb01560.x | journal = Journal of the American Ceramic Society | volume = 83 | issue = 10| pages = 2341–2359 | citeseerx = 10.1.1.514.1543 | s2cid = 9513223 }}</ref>
|  4–5.5 (7.3)
|-
| [[zirconium(IV) oxide|ZrO<sub>2</sub>]]<ref name="Kosmulski"/>
| 4–11
|-
| [[indium tin oxide|ITO]]<ref>{{cite journal | last1 = Daido | first1 = T | last2 = Akaike | first2 = T | year = 1993 | title = Electrochemistry of cytochrome c: influence of coulombic attraction with indium tin oxide electrode | journal = Journal of Electroanalytical Chemistry | volume = 344 | issue = 1–2| pages = 91–106 | doi=10.1016/0022-0728(93)80048-m}}</ref>
| 6
|-
| [[chromium(III) oxide|Cr<sub>2</sub>O<sub>3</sub>]]<ref name="Kosmulski"/><ref name="Jolivet"/> 
| 6.2–8.1 (7)
|-
| [[magnetite|Fe<sub>3</sub>O<sub>4</sub>]]<ref name="Kosmulski"/>
| 6.5–6.8
|-
| [[cerium(IV) oxide|CeO<sub>2</sub>]]<ref name="Kosmulski"/>
| 6.7–8.6
|-
| [[yttrium(III) oxide|Y<sub>2</sub>O<sub>3</sub>]]<ref name="Kosmulski"/>
| 7.15–8.95
|-
| γ-[[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]] 
| 7–8
|-
| β-MnO<sub>2</sub><ref name="Jolivet"/>
| 7.3
|-
| [[thallium(I) oxide|Tl<sub>2</sub>O]]<ref>{{cite journal | last1 = Kosmulski | first1 = M | last2 = Saneluta | first2 = C | year = 2004 | title = Point of zero charge/isoelectric point of exotic oxides: Tl2O3 | journal = Journal of Colloid and Interface Science | volume = 280 | issue = 2| pages = 544–545 | doi=10.1016/j.jcis.2004.08.079| pmid = 15533430 | bibcode = 2004JCIS..280..544K }}</ref>
| 8
|-
| α-[[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]]
| 8–9
|-
| α-Fe<sub>2</sub>O<sub>3</sub><ref name="Kosmulski"/>
| 8.4–8.5
|-
| [[zinc oxide|ZnO]]<ref name="Kosmulski"/>
| 8.7–10.3
|-
| [[silicon nitride|Si<sub>3</sub>N<sub>4</sub>]]<ref name="Lewis"/>
| 9
|-
| [[copper(II) oxide|CuO]]<ref name="Lewis"/>
| 9.5
|-
| [[lanthanum(III) oxide|La<sub>2</sub>O<sub>3</sub>]]
| 10
|-
| [[nickel(II) oxide|NiO]]<ref name="Lewis"/>
| 10–11
|-
| [[lead(II) oxide|PbO]]<ref name="Kosmulski">Marek Kosmulski, "Chemical Properties of Material Surfaces", Marcel Dekker, 2001.</ref>
| 10.7–11.6
|-
| [[magnesium oxide|MgO]]<ref name="Kosmulski"/>
| 12–13 (9.8·12.7)
|-
|}
''Note: The following list gives the isoelectric point at 25&nbsp;°C for selected materials in water. The exact value can vary widely, depending on material factors such as purity and phase as well as physical parameters such as temperature. Moreover, the precise measurement of isoelectric points can be difficult, thus many sources often cite differing values for isoelectric points of these materials.''

Mixed oxides may exhibit isoelectric point values that are intermediate to those of the corresponding pure oxides. For example, a synthetically prepared amorphous [[aluminosilicate]] (Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub>) was initially measured as having IEP of 4.5 (the electrokinetic behavior of the surface was dominated by surface Si-OH species, thus explaining the relatively low IEP value).<ref>{{cite journal | last1 = Jara | first1 = A.A. | last2 = Goldberg | first2 = S. | last3 = Mora | first3 = M.L. | year = 2005 | title = Studies of the surface charge of amorphous aluminosilicates using surface complexation models | journal = Journal of Colloid and Interface Science | volume = 292 | issue = 1| pages = 160–170 | doi=10.1016/j.jcis.2005.05.083| pmid = 16051258 | bibcode = 2005JCIS..292..160J | hdl = 10533/176403 | hdl-access = free }}</ref> Significantly higher IEP values (pH 6 to 8) have been reported for 3Al<sub>2</sub>O<sub>3</sub>-2SiO<sub>2</sub> by others.<ref name="Lewis"/> Similarly, also IEP of [[barium titanate]], BaTiO<sub>3</sub> was reported in the range 5–6<ref name="Lewis"/> while others got a value of 3.<ref name="VamvakakiBillingham2001">{{cite journal|last1=Vamvakaki|first1=Maria|last2=Billingham|first2=Norman C.|last3=Armes|first3=Steven P.|last4=Watts|first4=John F.|last5=Greaves|first5=Stephen J.|title=Controlled structure copolymers for the dispersion of high-performance ceramics in aqueous media|journal=Journal of Materials Chemistry|volume=11|issue=10|year=2001|pages=2437–2444|issn=0959-9428|doi=10.1039/b101728o}}</ref> Mixtures of [[Titanium dioxide|titania]] (TiO<sub>2</sub>) and [[zirconia]] (ZrO<sub>2</sub>) were studied and found to have an isoelectric point between 5.3–6.9, varying non-linearly with %(ZrO<sub>2</sub>).<ref name="GlennaLDrisko2009">{{cite journal|last1=Drisko|first1=Glenna L|last2=Luca|first2=Vittorio|last3=Sizgek|first3=Erden|last4=Scales|first4=Nicolas F.|last5=Caruso|first5=Rachel A.|title=Template Synthesis and Adsorption Properties of Hierarchically Porous Zirconium Titanium Oxides|journal=Langmuir|volume=25|issue=9|year=2009|pages=5286–5293|issn=0743-7463|doi=10.1021/la804030h|pmid=19397363}}</ref> The surface charge of the mixed oxides was correlated with acidity. Greater titania content led to increased Lewis acidity, whereas zirconia-rich oxides displayed Br::onsted acidity. The different types of acidities produced differences in ion adsorption rates and capacities.