Sorption equilibrium, thermodynamics and pH-indicator properties of cresyl violet dye/bentonite composite system

Abstract

The aim of the present study was to develop cresyl violet (CV)/bentonite composite system, to investigate the equilibrium sorption of the fluorescent dye on bentonite, to determine the characteristic equilibrium and thermodynamic parameters of the system by appropriate empirical isotherm models and to assess its pH-indicator properties. The absorption characteristics of CV solutions were investigated by UV/VIS spectrophotometer. Equilibrium experiments were conducted and the experimental data were modelled by six mathematical isotherm models. The analyses of the experimental data showed that bentonite exhibited significantly high capacity - 169.92 mg/g, towards CV. The encapsulation efficiency was 85%. The Langmuir, Flory-Huggins and El-Awady models best represented the experimental results. The free Gibbs energy of adsorption (ΔG) was calculated on the basis of the values of the equilibrium coefficients determined by the proposed models. The values of ΔG determined by the Langmuir, Temkin and Flory-Huggins models are within the range -20 to -40 kJ/mol, which indicates that the adsorption process is spontaneous and chemisorption takes place due to charge sharing or transfer from the dye molecules to the sorbent surface as a coordinate type of bond. The investigations of the obtained CV/bentonite hybrid systems for application as pH-markers showed satisfactory results.

A Comparative Study on the Adsorption of Two Remazol Dyes on Green Adsorbent

“…Adsorption as a water cleaning method has been found to be more favorable than other treatments due to its low cost, simplicity of design, ease of operation, and insensitivity of toxic substance [6]. Recently, many researchers have focused on finding low cost and available adsorbents from agricultural, industrial, household wastes: green tea [7], sandpaper waste [8], corn cob [9], sawdust [10][11][12], microcline particles [13], bentonite [14][15][16], agricultural waste [17][18][19], brown alga [20], soy bean and mustard husk [21], wheat bran [22], wood fiber [23]. Eggshell was also used as a possible adsorbent for cyanide, heavy metal, phenol, phosphate, pharmaceutical antibiotics and dye removal [24][25][26][27][28][29][30][31][31][32][33][34].…”

Adsorptive Removal of Remazol Brilliant Violet-5R Dye from Aqueous Solutions using Calcined Eggshell as Biosorbent

“…The adsorption processes have been widely researched in the context of water pollution and several alternative biosorbents have been tested for efficacy. These biosorbents can be household or industrial wastes: orangeand banana peel 10 tea/coffee filter 11,12 grape-, potato-and apple peel 13 dead and dried mushrooms 14,15 sawdust, 16 bentonite [17][18][19] clay. 20 Eggshells from household waste can also be used as an adsorbent.…”