Adsorption of Methylene Blue and Acid Blue 40 on Titania from Aqueous Solution

Abstract

Langmuir type adsorption was observed for two systems: methylene blue (MB) on TX titania and acid blue 40 (AB40) on P25 titania at an ambient temperature of (23 ± 2) °C and ambient pH initially at 4.6 ± 0.2 for P25 titania and 7.8 ± 0.2 for TX titania. Based on a Langmuir analysis, values for maximum surface coverage, N max, and adsorption intensity, b, are 1.6 × 10-5 mol MB·g-1 and 3.6 × 104 L·mol-1, respectively, for TX titania. An N max value of 5.0 × 10-5 mol AB40·g-1 was determined for P25 titania. The TX titania adsorption surface area is estimated to be 12 m2·g-1 based on maximum adsorption of methylene blue. Results of gel electrophoresis on both dyes at pH values of 4 and 9 indicate that methylene blue remains cationic and acid blue 40 remains anionic in this pH range. Single-point adsorption experiments at selected pH values other than ambient were performed. Experimental evidence clearly indicates that electrostatic attraction is a reasonable explanation for the observed adsorption process in the MB/TX system. Although the evidence is less conclusive, electrostatic attraction may also influence the adsorption process of the AB40/P25 system.

Photocatalytic degradation of methylene blue and phenol on Fe-doped sulfated titania

“…The pH of solution is one of the most important controlling parameters in the photocatalytic degradation of the organic pollutants on semiconductor metal oxides since it determines the surface characteristics (such as surface charge) of particulates introduced into those solutions [14]. The point of zero net charge, pH pznc , is a unique pH value that balances the number of protonated and deprotonated surface sites, resulting in a net-neutral surface charge.…”

“…5 that the degradation of methylene blue increases with increasing pH up to 8.0, and thereafter nearly maintains constant, while the degradation of phenol increases with decreasing pH until to 4.0, and thereafter also nearly maintains constant. The pH effects can be explained on the basis of the pH pznc of the FST samples, which are typically in the range of 4.5-5.5 as reported in the literature [14,15]. When the pH values of the solution are greater than 5.5, the surface of the FST sample becomes negatively charged, which is favorable for the adsorption of the cationic methylene blue dye and consequently improving the photocatalytic degradation of methylene blue up to pH of 8.0.…”

Selective Adsorption and Photocatalytic Degradation of Dyes Using Polyoxometalate Hybrid Supported on Magnetic Activated Carbon Nanoparticles under Sunlight, Visible, and UV Irradiation

“…Consequently, treatment of dye-contaminated wastewaters with decontamination processes is necessary before their discharge. Adsorption of dyes on inexpensive and efficient solid supports especially on activated carbon (AC) and AC composites is one of the simplest and most economical methods for removing dyes from wastewater [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]; however, the disposal of residues is still a problem. Advanced oxidation processes (AOPs) are widely accepted as an efficient method for dye-contaminated wastewater due to complete degradation of organics into carbon dioxide and water.…”

Adsorption of Organic Dyes on Lignophenol under Heterogeneous Conditions

“…It has been pointed out dilute solutions of these dyes were one of the serious sources of water pollution of rivers, lakes and marshes [1][2] especially in China, USA and the countries in South America and Asia. Therefore a lot of attempts to remove these dyes from dilute solution spread in environments using activated carbons [3], photocatalysts [4][5][6] and conductive polymers [7] have been tried already. Although both activated carbon and catalysis demonstrated relatively large adsorption of dyes, there remained several problems such as poor desorption properties or high costs.…”