Browsing by Author "Chmielarz, Lucjan"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Acid-base treated vermiculite as high performance adsorbent: Insights into the mechanism of cationic dyes adsorption, regeneration, recyclability and stability studiesPublication . Stawiński, Wojciech; Węgrzyn, Agnieszka; Dańko, Tomasz; Freitas, Olga; Figueiredo, Sónia; Chmielarz, LucjanAdditional treatment with NaOH of acid activated vermiculite results in even higher increase in the adsorption capacity in comparison to samples modified only in acidic solution (first step of activation) with respect to raw material. Optimization of treatment conditions and adsorption capacity for two cationic dyes (methylene blue (MB) and astrazon red (AR)), also as binary mixture, was evaluated. The capacity, based on column studies, increased from 48 ± 2 to 203 ± 4 mg g-1 in the case of methylene blue and from 51 ± 1 to 127 ± 2 mg g-1 in the case of astrazon red on starting and acid-base treated material, respectively. It was shown that adsorption mechanism changes for both cationic dyes after NaOH treatment and it results in decrease of adsorption rate. In binary mixtures methylene blue is bound stronger by adsorbent and astrazon red may be removed in initial stage of adsorption. Extensive studies on desorption/regeneration process proved high efficiency in recyclable use of all materials. Although cation exchange capacity decreases due to acid treatment, after base treatment exchange properties are used more efficiently. On the other hand, increased specific surface area has less significant contribution into the adsorption potential of studied materials. Obtained adsorbents worked efficiently in 7 adsorption-regeneration cycles and loss of adsorption capacity was observed only in two first cycles.
- Dual-function hydrotalcite-derived adsorbents with sulfur storage properties: Dyes and hydrotalcite fate in adsorption-regeneration cyclesPublication . Stawiński, Wojciech; Węgrzyn, Agnieszka; Freitas, Olga; Chmielarz, Lucjan; Figueiredo, SóniaThermal treatment of hydrotalcite at increasing temperatures resulted in formation of mixed oxides that exhibited different adsorption behavior toward anionic and cationic industrial dyes. The material annealed at 450 °C was characterized by the highest maximum adsorption capacity for both types of dyes. The adsorption was strongly pH dependent and for the anionic dye abatement low pH was favored whilst higher pH was more preferable for removal of the cationic dye. According to the equilibrium experiments, the maximum adsorption capacity increased from 179 ± 5 to 291 ± 8 mg g−1 in case of the anionic dye at pH 3.5 and from 6 ± 2 to 48 ± 2 mg g−1 in case of the cationic dye at pH 8.0, on starting and thermally treated material at 450 °C, respectively. Detailed characteristics of spent adsorbent and its reconstructed form revealed that after each cycle of adsorption and thermal regeneration the maximum adsorption capacity of the material decreased due to changes in the structure and accumulation of sulfur compounds. Evolution of specific surface area and porosity was correlated with annealing temperatures and behavior of dye's residues.
- Simultaneous removal of dyes and metal cations using an acid, acid-base and base modified vermiculite as a sustainable and recyclable adsorbentPublication . Stawiński, Wojciech; Węgrzyn, Agnieszka; Freitas, Olga; Chmielarz, Lucjan; Mordarski, Grzegorz; Figueiredo, SóniaThe aimof thiswork was the modification of vermiculite in order to produce a lowcost, efficient and sustainable adsorbent for dyes and metals. Three activation methods consisting of acid, base and combined acid/base treatment were applied to improve the of vermiculite's adsorption properties. Adsorbents were tested in single, biand tricomponent solutions containing cationic dyes and Cu2+ cations. The rawmaterial showed lowadsorption capacity for dyes and metal. The acid/base treated vermiculite had very good adsorption capacity toward dyes while the maximumadsorption capacity for Cu2+ did not change comparing to the startingmaterial. The alkaline treated vermiculite was a good adsorbent for metals,while still being able to remove dyes on the level of the not treated material. Moreover, it was shown that the materials may be regenerated and used in several adsorptiondesorption cycles. Furthermore, itwas possible to separate adsorbed dyes from metals thatwere desorbed, using as eluents ethanol/NaCl and 0.05MHNO3, respectively. This opens a possibility for sustainable disposal and neutralization of both of the pollutants or for their further applications in other processes.
- The influence of acid treatments over vermiculite based material as adsorbent for cationic textile dyestuffsPublication . Stawiński, Wojciech; Freitas, Olga; Chmielarz, Lucjan; Węgrzyn, Agnieszka; Komędera, Kamila; Błachowski, Artur; Figueiredo, SóniaThe influence of different acid treatments over vermiculite was evaluated. Equilibrium, kinetic and column studies have been conducted. The results showed that vermiculite first treated with nitric acid and then with citric acid has higher adsorption capacity, presenting maximum adsorption capacities in column experiments: for Astrazon Red (AR), 100.8 ± 0.8 mg g−1 and 54 ± 1 mg g−1 for modified and raw material, respectively; for Methylene Blue (MB) 150 ± 4 mg g−1 and 55 ± 2 mg g−1 for modified and raw material, respectively. Materials characterization by X-ray diffraction, UV–vis-diffuse reflectance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, X-ray fluorescence, N2 adsorption and CEC determination, has been performed. The results suggest the existence of exchange of interlayer cations, leaching of metals from vermiculite's sheets and formation of an amorphous phase in the material. Adsorption follows pseudo 2nd order model kinetics for both dyestuffs and equilibrium occurs accordingly to Langmuir's model for AR and Freundlich's model for MB. In column systems Yan's model is the best fit. The enhanced properties of acid treated vermiculite offer new perspectives for the use of this adsorbent in wastewater treatment.