KINETIC AND OPTIMIZATION STUDIES ON THE ADSORPTION OF DYES ONTO ACTIVATED CLAYS

AUTHOR: OBIEJESI CALISTA CHIMELOGO

DEPARTMENT: CHEMICAL ENGINEERING

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

In this study, the adsorption of Vat yellow and Orange G dyes onto activated clays was investigated. The activated clays were prepared from Uli and Akwuke clays using H2SO4 and NaOH as activating agents leading to the production of four adsorbents. The surface characterization of the clays was performed using FTIR, AAS, XRD, XRF and SEM analyses. Some physico-chemical properties, such as surface area, bulk density, pH and moisture content, of the activated clays were also determined. The effect of particle size, dosage, pH, contact time, temperature and initial dye concentration was studied. It was observed that decrease in adsorbent particle size, increase in adsorbent dosage, decrease in pH, initial dye concentration, temperature and increase in contact time increased the adsorption capacity. Equilibrium modelling of the processes reveals that both Langmuir and Freundlich Isotherms fitted the adsorption data properly. The maximum adsorption capacity (44.64mg/g) of orange G was obtained with the Akwuke clay activated with NaOH(AkwukeNaOH) at 303K, while that of vat yellow (11.47mg/g) was obtained with Akwuke clay activated with H2SO4(Akwuke H2SO4) at 303K. Seven kinetic models were also tested to investigate the adsorption mechanism. It was shown that the adsorption of both vat yellow and orange G dyes on the adsorbents could be best described by the pseudo-second order kinetic model. The percentage of the dyes removed was successfully optimized using response surface methodology (RSM). The result shows that the optimum condition for the adsorption of vat yellow onto the four adsorbents and orange G onto AkwukeH2SO4 and AkwukeNaOH was temperature of 308K, contact time of 45minutes, dosage of 1.0g and pH of 1.38, while optimum condition of orange G adsorption onto UliH2SO4 and UliNaOH was temperature of 308K, contact time of 45minutes, dosage of 1.0g and pH of 10.82. This resulted to76.53% adsorption of Orange G onto AkwukeNaOH, 77.22% adsorption of Orange G onto AkwukeH2SO4, 80.29% adsorption of orange G onto UliH2SO4, 83.55% adsorption of Orange G onto UliNaOH, 76.76% adsorption of vat yellow onto Akwuke H2SO4, 73.21% adsorption of vat yellow onto AkwukeNaOH, 76.27% adsorption of vat yellow onto UliNaOH and 78.69% adsorption of vat yellow onto UliH2SO4. The proposed quadratic model of central composite design (CCD) fitted very well to the experimental data that it could be used to navigate the design space according to ANOVA results.

TO VIEW THE FULL CONTENT OF THIS DOCUMENT, PLEASE VISIT THE UNIZIK LIBRARY WEBSITE USING THIS LINK, http://naulibrary.org/dglibrary/admin/book_directory/Thesis/11662.pdf

Advertisements

Tags: , , , , , , , , , , ,

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: