caa a22 4500 47576448X CHVBK 20180406123601.0 cr unu---uuuuu 170329e20000401xx s 000 0 eng 10.1007/s003960050522 doi (NATIONALLICENCE)springer-10.1007/s003960050522 Effect of pH and ionic strength on the interaction of humic acid with aluminium oxide [Elektronische Daten] [E. Tombácz, Á. Dobos, M. Szekeres, H. D. Narres, E. Klumpp, I. Dékány] The effect of pH and neutral electrolyte on the interaction between humic acid/humate and γ-AlOOH (boehmite) was investigated. The quantitative characterization of surface charging for both partners was performed by means of potentiometric acid-base titration. The intrinsic equilibrium constants for surface charge formation were logK a,1 int=6.7±0.2 and logK a,2 int = 10.6±0.2 and the point of zero charge was 8.7±0.1 for aluminium oxide. The pH-dependent solubility and the speciation of dissolved aluminium was calculated (MINTEQA2). The fitted (FITEQL) pK values for dissociation of acidic groups of humic acid were pK 1 = 3.7±0.1 and pK 2 = 6.6±0.1 and the total acidity was 4.56 mmol g−1. The pH range for the adsorption study was limited to between pH 5 and 10, where the amount of the aluminium species in the aqueous phase is negligible (less than 10−5 mol dm−3) and the complicating side equilibria can be neglected. Adsorption isotherms were determined at pH ∼ 5.5, ∼8.5 and ∼9.5, where the surface of adsorbent is positive, neutral and negative, respectively, and at 0.001, 0.1, 0.25 and 0.50 mol dm−3 NaNO3. The isotherms are of the Langmuir type, except that measured at pH ∼ 5.5 in the presence of 0.25 and 0.5 mol dm−3 salt. The interaction between humic acid/humate and aluminium oxide is mainly a ligand-exchange reaction with humic macroions with changing conformation under the influence of the charged interface. With increasing ionic strength the surface complexation takes place with more and more compressed humic macroions. The contribution of Coulombic interaction of oppositely charged partners is significant at acidic pH. We suppose heterocoagulation of humic acid and aluminium oxide particles at pH ∼ 5.5 and higher salt content to explain the unusual increase in the apparent amount of humic acid adsorbed. Springer-Verlag Berlin Heidelberg, 2000 Key words Humic acid nationallicence Aluminium oxide nationallicence Adsorption nationallicence Heterocoagulation nationallicence Surface complexation nationallicence Tombácz E. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut Dobos Á. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut Szekeres M. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut Narres H. D. Department of Applied Physical Chemistry Research Center Jülich, D-52425 Jülich, Germany, DE aut Klumpp E. Department of Applied Physical Chemistry Research Center Jülich, D-52425 Jülich, Germany, DE aut Dékány I. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut https://doi.org/10.1007/s003960050522 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s003960050522 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Tombácz E. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut NATIONALLICENCE 700 1- Dobos Á. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut NATIONALLICENCE 700 1- Szekeres M. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut NATIONALLICENCE 700 1- Narres H. D. Department of Applied Physical Chemistry Research Center Jülich, D-52425 Jülich, Germany, DE aut NATIONALLICENCE 700 1- Klumpp E. Department of Applied Physical Chemistry Research Center Jülich, D-52425 Jülich, Germany, DE aut NATIONALLICENCE 700 1- Dékány I. Department of Colloid Chemistry Attila József University Aradi Vt. 1., H-6720 Szeged Hungary e-mail: tombacz@chem.u-szeged.hu Tel.: +36-62-544212 Fax: +36-62-426221, HU aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer