1. Organophilic bentonite for Telon derivatives removal from aqueous media
Mohamed Amine Didi1 , Benamar Makhoukhi1, Didier Villemin2
1LTSP, Département de chimie, université de Tlemcen, B. P. 119, Tlemcen 13000, Algérie.
2LCMT, UMR CNRS 6507, Université de Caen-ENSICAEN, 6 Boulevard du Maréchal Juin, Caen
Introduction
Clay ion-exchange using diphosphonium salts could provide organophilic clays materials that allow effective retention of polluting dyes. Phosphonium salts [1-4.] have already been used successfully for this purpose. Due this hydrophobicity, organoclays will be expected to behave as effective sorbent for organic pollutants, more particularly those having low solubility. For this purpose, the present investigations deal with bentonite modification using ortho, meta, and para diphosphonium salts and attempts to retain harmful organic dyes having highly farmful character, such as Red Telon, Blue Telon and Orange Telon. Kinetical and equilibrium aspects of the interactions occurring between the as-obtained orgaoclays and the dispersed to be retained also tackled herein, with insights in the effects temperature and pH.
Results & Discussion
Dyes solutions preparation
Dye waste-waters were simulated by aqueous solutions of Telon-series organic dyes industrially used for coloring polyamide fibers, namely: Red (C22H16N3NaO6S2), Blue (C22H14N6Na2O9S2) and Orange (C22H14N6Na2O9S2) (Scheme 1). Once prepared, each solution containing 100 mg/l of the respective dye, was kept in dark vessel for futher experimental purposes.
Red
Orange
Blue
Fig. 1. XRD patterns of the clay materials in the vicinity of the 001 reflection
1. Crude bentonite; 2. NaMt; 3. o-TPhPMB-Mt; 4. m-TPhPMB-Mt; 5. p-TPhPMB-Mt.
Fig. 2. Dye adsorption capacity on Na-Mt versus temperature a. Telon-red; b. Telon-blue; c. Telon-orange °C; °C; °C; °C.
Scheme 1. Chemical structures of Telon dyes
Table 1. Calculations of the global rate constants
Telon dye
1st Order
2nd Order
k1 (min-1) R2
k2 ( min.g-1.mg-1).
Red
0.037
0.998
0.0058
0.94
Blue
0.038
0.997
0.0047
0.97
Orange
0.074
0.970
0.71
Fig. 5. pH of the dye solution in the presence of organo-Mt
a. Telon-red; b. Telon-blue; c. Telon-orange.
Fig. 3. pH of the dye solution in the presence of NaMt 1. Telon-orange; 2. Telon-red; 3. Telon-blue.
Fig. 4. Log (Q max – Qads) on NaMt 1. Telon-blue; 2. Telon-orange; 3. Telon-red.
Table 2
Langmuir parameters for dye adsorption on various organo-Mts.
Fig. 6. Evolution in time of the pH of the dye solution.
a. Telon-red; b. Telon-blue; c. Telon-orange
Fig. 7. Langmuir dye adsorption on organo-Mt a: p-TPhPMB-Mt;
b: o-TPhPMB-Mt; c: m-TPhPMB-Mt 1. Telon-blue; 2. Telon-red; 3. Telon-orange.
Fig. 6. Amount of dye adsorbed on organo-Mt versus dye equilibrium concentration
1. p-TPhPMB-Mt; 2. m-TPhPMB-Mt; 3. o-TPhPMB-Mt; 4. NaMt. a. Telon-blue; b. Telon-red; c. Telon-orange.
Table 3
Freundlich parameters for dye adsorption on various organo-Mts.
Organoclay
p-TPhPMB-Mt
o-TPhPMB-Mt
m-TPhPMB-Mt
Telon dye n K R2
Red
0.908
1.049
0.991
0.820
1.096
0.989
0.878
1.02
0.98
Blue
0.672
1.471
0.979
0.6005
1.449
0.96
0.777
1.102
Orange
0.804
1.043
0.990
0.773
0.86
0.769
0.973
Fig. 8. Freundlich dye adsorption on organo-Mt 1. Telon-orange; 2. Telon-red;
3.Telon-blue a: p-TPhPMB-Mt; b: o-TPhPMB-Mt; c: m-TPhPMB-Mt.
Fig. 9. Ln (KC) versus 1/T for dye adsorption on Na-Mt
Telon-blue; 2. Telon-red; 3. Telon-orange
Table 4. Thermodynamical parameters for dye sorption on various organoclays
*(Kcal/mol) ; **(cal.mol-1/K)
Organoclay
Na-Mt
p-TPhPMB-Mt
Telon dye
ΔH*
ΔS** R2
Red
-1,99
-7,42
0,949
-14.34
-47.41
0.998
Blue
-1,42
-6,01
0,98
-12.0
-42.18
0.999
Orange
-1,03
-3,33
0,99
-5.40
-18.21
0.997
Fig. 10. Ln (KC)versus 1/T for dye adsorption on p-TPhPMB-Mt
Telon-blue; 2. Telon-red; 3. Telon-orange
Fig. 11. Amount of adsorbed dye on p-TPhPMB-Mt at different pH values
a: Telon-red; b: Telon-blue; c: Telon-orange
1. pH=1.0; 2: pH=1.5; 3. pH=2.0; 4. pH=7.0.
Conclusion
The results obtained herein allow to conclude that montmorillonite intercalation with disphosphonium salts provide valuable organoclays with improved affinity towards organic dyes in major textile waste-waters This affinity improvement was demonstrated by an increase of the amount of dye adsorbed as compared to the starting NaMt, and was explained in terms of enhanced organophilic character and acidity of the resulting organoclays. The dye adsorption affinity decreases in the following sequence: Orange, Red and blue. The steric effect of the dye molecule appears to exert a significant influence on the dye adsorption.
The amount of p-TPhPMB inserted in the clay interlayer space was higher than those of m-TPhPMB and o-TPhPMB. The p-TPhPMB induced the higher effectiveness in the dye adsorption process, as compared to the two other diphosphonium salts.
The dye sorption seems to obey a first pseudo-order kinetics, while the adsorption isotherms fit to Freundlich’s model. Temperature and pH also play predominant roles, as compared to that of the counter ion of the pH-adjusting acid. Increasing temperature appears to be detrimental, because adsorption is an exothermal process, and acidic pH improves significantly the adsorption process. The low values of the adsorption heat suggest that the dye adsorption involves only physical interactions between the organoclay surface and dye molecules.
Fig. 12. Effect of the acid species upon the amount of adsorbed dye on p-TPhPMB-Mt at pH 1 a: Telon-blue; b: Telon-red; c: Orange –Telon 1. HCl; 2. H2SO4; 3. HNO3.
References
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