Document Detail


Acid/Base Properties and Phenylphosphonic Acid Complexation at the Boehmite/Water Interface
MedLine Citation:
PMID:  8954688     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Acid/base properties and phenylphosphonic acid (H2L) complexation at the boehmite (gamma-AlOOH)/water interface have been studied by means of potentiometric titrations and batch experiments. All measurements have been performed in 0.100 M Na(Cl) ionic medium at 25degreesC. The experimental data have been evaluated on the basis of the surface complexation concept with the use of the constant capacitance model to account for electrostatic contributions. It was found that the boehmite surface possesses 65% higher proton exchange capacity per surface area unit than previously recorded for an aged gamma-Al2O3 surface. This high surface concentration (0.51 mol/kg gamma-AlOOH; site density = 1.71 sites/nm2) was reflected in the acid/base model as a large contribution from electrostatic forces, and accordingly as a low specific capacitance value. The model describing the acid/base reactions at the boehmite surface is given by the following reactions, intrinsic constants, and specific capacitance: $\displaylines{ \hfill\equiv\!\!\equiv \hbox{AlOH} + \hbox{H}^+ {\enspace}^{\rightarrow}_{\leftarrow}{\enspace} \equiv\!\!\equiv \hbox{AlOH}^+_2;\ \log\beta_{\rm(int)} = 7.47 \pm 0.06\hfill\cr \hfill\equiv\!\!\equiv \hbox{AlOH} {\enspace}^{\rightarrow}_{\leftarrow}{\enspace} \equiv\!\!\equiv \hbox{AlO}^- + \hbox{H}^+;\ \log\beta_{\rm(int)} = -9.81 \pm 0.18\hfill\cr \hfill C = 0.92 \hbox{F/m}^2\hfill\cr } $ The maximum adsorption of phenylphosphonic acid was observed at -log [H+] < 7 and it was found to equal 50% of the proton exchange capacity. Within the approximate range of 7.7 < -log[H+] < 9.5, a strong decrease in adsorption affinity occurs. Data for the three-component system H+-gamma-AlOOH surface-phenylphosphonic acid can be explained with a model assuming a formation of two 1:2 $ (\hbox{H}_2L/\equiv\!\!\equiv\hbox{AlOH}) $ complexes according to the reactions $ \displaylines{ \matrix{\equiv\!\!\equiv\hbox{AlOH}\cr \vert\cr \equiv\!\!\equiv\hbox{AlOH}\cr} + \hbox{ H}_2L{\enspace}^{\rightarrow}_{\leftarrow}{\enspace} \left(\matrix{\equiv\!\!\equiv \hbox{Al}\cr \hphantom{\equiv\!\!\equiv\qquad}\vert\hbox{ OH}&\cr \equiv\!\!\equiv\hbox{Al} &\cr}\right)L\hbox{H} + \hbox{H}_2\hbox{O};\hfill\cr \hfill\log\beta_{\rm(int)} = 9.53 \pm 0.07\cr \matrix{\equiv\!\!\equiv\hbox{AlOH}\cr \vert\cr \equiv\!\!\equiv\hbox{AlOH}\cr} + \hbox{ H}_2L{\enspace}^{\rightarrow}_{\leftarrow}{\enspace} \left(\matrix{\equiv\!\!\equiv \hbox{Al}\cr \hphantom{\equiv\!\!\equiv\qquad}\vert\hbox{ OH}&\cr \equiv\!\!\equiv\hbox{Al} &\cr}\right)L^- + \hbox{H}^+ + \hbox{H}_2\hbox{O};\hfill\cr \hfill\log\beta_{\rm(int)} = 2.56 \pm 0.04\cr } $ No attempts were made to further adjust the acid/base model during the evaluation of the three-component model. The acid/base and phenylphosphonic acid complexation features of the boehmite surface have been compared to those of the aged gamma-Al2O3.
Authors:
Laiti; ohman
Related Documents :
21556928 - Expression of the h+-atpase aha10 proton pump is associated with citric acid accumulati...
12672478 - Peroxidation stimulated by lipid hydroperoxides on bovine retinal pigment epithelium mi...
21307938 - Asymmetric additions to dienes catalysed by a dithiophosphoric acid.
9367728 - In vitro effects of secondary plant compounds on germination of blastospores of the ent...
68028 - The effect of sodium chloride on the extraction of dna fragments during feulgen acid hy...
21047568 - Fluvastatin does not prevent the acute-phase response to intravenous zoledronic acid in...
Publication Detail:
Type:  JOURNAL ARTICLE    
Journal Detail:
Title:  Journal of colloid and interface science     Volume:  183     ISSN:  1095-7103     ISO Abbreviation:  J Colloid Interface Sci     Publication Date:  1996 Nov 
Date Detail:
Created Date:  1996-12-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0043125     Medline TA:  J Colloid Interface Sci     Country:  -    
Other Details:
Languages:  ENG     Pagination:  441-52     Citation Subset:  -    
Affiliation:
Department of Inorganic Chemistry, Umea University, Umea, S-901 87, Sweden
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  The Effect of Humidity on the Physical and Chemical Stability of Spray-Dried Aluminum Hydroxycarbona...
Next Document:  Study of the Adsorption of Some Amino Acids by Silica Chemically Modified with Aminobenzenesulfonic ...