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Adsorption of anionic dyes onto natural, thermally and chemically modified smectite clays

Kyzioł-Komosińska J., Rosik-Dulewska Cz., Pająk M., Krzyżewska I., Dzieniszewska A.

Polish Journal of Chemical Technology

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2014

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Vol. 16, nr 4

33--40

EN

The aim of this study was to determine the adsorption capacity of the smectite clays (from the overburden of the lignite deposit in Belchatow) for two anionic dyes, i.e. Reactive Blue 81 (RB-81) and Direct Blue 74 (DB-74). Additionally, the infl uence of the thermal and chemical (acid and alkali) clay modifi cations on the amount of bonded dyes was investigated. The adsorption capacity of the clay (natural and modifi ed) was different for studiem dyes and depended on the initial concentration and modifi cation type. All the modifi ed clays adsorbed the dyes AT pH>pHPZC as the negatively charged surfaces of their particles (in accordance with the formula: AOH ↔ AO– +H+) prevented the formation of electrostatic bonds between the anionic dyes and the clay surface. The dyes were mainly bound with the hydrogen bonds forming between the donor groups in the dyes and the acceptor groups (–SiO and –Al2OH) in the clays. The coeffi cients in the adsorption isotherms were estimated with the linear and non-linear regression. The linear regression method was found that the Freundlich and Dubinin-Radushkevich isotherms described the dye sorption much better than the Langmuir model. On the other hand, all three models described well the experimental data in the non-linear regression method. Furthermore, the 1/n value (<1) obtained from the Freundlich equation for all the dye-sorbent systems indicated the favorable sorption.

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Photoelectrochemical Degradation of the Reactive Dye - Reactive Blue 81

Kusmierek E., Chrzescijanska E.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 7

1337-1351

EN

The results of photochemical, electrochemical and photoelectrochemical degradation of Reactive Blue 81 with the application of titanium electrodes covered with titanium and ruthenium oxides are presented in this paper. The influence of current density, process time and dye concentration on the photoelectrochemical degradation was investigated. The photochemical degradation of Reactive Blue 81 resulted only in a slight decolourization of the dye solution. The electrochemical oxidation improved the effective ness of the dye degradation but the complete mineralization was still not achieved. The combination of photochemical process with electrochemical oxidation at the titanium electrodes covered with titanium and ruthenium oxides, resulted in a significant mineralization of the dye solution. It did not require addition of any chemicals or difficult post-treatment processes the way it is necessary in the photodegradation with TiO2 used in the suspension mode.

3

Investigation of Reactive Blue 81 Electrooxidation at Various Electrode Materials - Kinetic Parameter

Chrzescijanska E., Kusmierek E., Nawrat G.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 6

1115-1126

EN

The electrochemical oxidation of Reactive Blue 81 proceeds easier at titanium electrodes covered with titanium and ruthenium oxides than at a platinum electrode. This process proceeds at both types of electrodes in at least one electrode step before potentials reach the value at which the oxygen evolution starts and is irreversible. Ruthenium oxide has electrocatalytic properties and titanium oxides has photocatalytic properties. An increase in the content of RuO2 at the surface of a titanium electrode causes electrooxidation of Reactive Blue 81 to proceed easier and quicker. The substrate is also reduced in at least two electrode steps at potentials higher than the potentials at which the hydrogen evolution starts. The reduction is also irreversible. An increase in pH of the dye solution facilitates the electrooxidation of Reactive Blue 81.