Modified bentonite as adsorbent and catalyst for purification of wastewaters containing dyes

• Published in: Hemijska industrija Vol. 64; no. 3; p. 193
• Main Author: Žunić, Marija J
• Format: Journal Article
• Language: English; Serbian
• Published: Belgrade Hemijska Industrija 01.01.2010
• Subjects: Adsorption; Adsorptivity; Affinity; Bentonite; Catalysts; Catalytic purification; Clay; Dyes; Exchanging; Granulation; Iron; Oxidation; Pillars; Surface chemistry; Wastewater
• ISSN: 0367-598X; 2217-7426
• DOI: 10.2298/HEMIND091221023Z

Modification and characterization of bentonite from location Bogovina, Serbia was performed in order to obtain material applicable in wastewater purification. The <75μm bentonite fraction was used in organobentonite synthesis while the <2μm bentonite fraction, obtained by hydroseparation was used in pillaring procedure. Organo-modification of bentonite was performed with (1-hexadecyl)trimethylammonium bromide (HDTMA-Br). Pillared bentonite was obtained using standard procedure. Al3+ and Fe3+ ions were incorporated in pillars in 4:1 ratio and applied as catalyst in catalytic wet peroxide oxidation. Differences in structure of starting and modified bentonites were established by XRD analysis and nitrogen physisorption on -196 °C. The (001) smectite peak around 2θ = 6° shifts during the modification process. The Na-exchange process lowered d001 from 1.53 nm (2θ = 5.78°) for starting clay to 1.28 nm (2θ = 6.92°), but the clay retained its swelling properties. The pillaring process increased and fixed the basal spacing to 1.74 nm. Intercalation of HDTMA ions into smectite structure increased d001 to 2.00 nm for organobentonite. Specific surface area, SBET, was affected by particle size and type of modification. The samples with finer bentonite fraction had higher SBET due to increased smectite content. Na-exchanged bentonite samples had higher SBET value than starting clay samples of same granulation. Organomodification caused dramatic decrease in SBET value, while the pillaring process lead to an increase of SBET value. Adsorptive and catalytic purification of wastewaters containing dyes was tested using Acid Yellow 99 as a model dye. Na-exchanged bentonite had greater adsorption affinity for dye adsorption than raw bentonite owing to higher SBET. By organomodification this affinity was enhanced more than 70 times due to transition of bentonite surface from hydrophilic to organophilic. Al,Fe pillared bentonite was proven to be efficient in catalytic wet peroxide oxidation of Acid Yellow 99 dye at room temperature.