Removal of Textile Dyes from Aqueous Solutions Using Graphene Based Adsorbents

Abstract

This thesis is composed of five parts: Introduction (Chapter 1), Literature Review Chapter 2), Materials and Methods (Chapter 3), Results and Discussion (Chapter 4) and Conclusions (Chapter 5). Background and objectives of the study has been discussed in Chapter 1 and the literature reviews related to the research are elaborated in Chapter 2. Chapter 3 represents information about the materials used in this research. Here the methods and different equations and models used for the research are also stated. Chapter 4 deals with main research work and it is divided into three parts. Part 1 describes the synthesis, characterization of graphene oxide (GO) and its application for the removal of industrially used two synthetic anionic dyes such as FD-R H/C, TURQUOISE GN and one cationic dye, Maxilon Blue (GRL) from aqueous solutions. Here, GO was prepared from graphite powder by modified Hummer’s method. Characterization of prepared GO was carried out by FTIR spectroscope, Raman spectroscope, ESEM, AFM, XRD and elemental analysis. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dyes on GO surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir isotherm the adsorption capacity was found 151.29 mg/g for FD-R H/C at pH of 2. For TURQUOISE GN the adsorption capacities were 565.61 mg/g and 294.12 mg/g at pH of 2 and 7, respectively. For Maxilon Blue (GRL) the adsorption capacity was 1253.13 mg/g at pH of 7.The experimental data were analyzed using pseudofirst-order and pseudo-second-order models. Analyzing the kinetic parameters it was found that the pseudo-second order kinetic model showed better correlation compared to the pseudo-first-order model. The thermodynamic analyses are also carried out. From thermodynamic analyses Gibb’s free energy ∆Go values were found -1.69, -1.17 and -0.86 KJ mol-1 for dye FD-R H/C at 303K, 313K and 323K, respectively. While for TURQUOISE GN, ∆Go values were -3.66, -2.92, -2.39 KJ mol-1 and for Maxilon Blue (GRL) ∆Go values were -4.11, -3.80, -2.77 KJ mol-1 at 303K, 313K and 323K, respectively. These results confirm that the adsorption of the dyes on GO are more spontaneous at lower temperature and were physical adsorption.The used GO was regenerated using 2 % HCl and used for adsorption study. For dye TGN, fresh GO showed the adsorption capacity of 102.39 mg/g for 200 ppm dye solution while the regenerated GO of 1st, 2nd, 3rd and 4th recycle showed the adsorption capacities of 75.91 mg/g, 65.73 mg/g, 44.32 mg/g and 41.25 mg/g. For dye MBG, fresh GO showed the adsorption capacity of 1421.10 mg/g for 1000 ppm dye solution while the regenerated GO of 1st, 2nd and 3rd recycle showed the adsorption capacities of 1066.06 mg/g, 792.50 mg/g and 713.18 mg/g. Part 2 describes the synthesis, characterization of reduced graphene oxide (RGO) and its application for the removal of dye TURQUOISE GN from aqueous solutions. RGO was prepared by reduction of GO using hydrazine hydrate. Characterization of prepared RGO was carried out by ESEM, Raman spectroscope, XRD and elemental analysis. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dye on RGO surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir model the adsorption capacity was found 588.24 mg/g for TURQUOISE GN at pH of 7. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models. Analyzing the kinetic parameters it was found that the pseudo-second order kinetic model showed better correlation compared to the pseudo-firstorder model. The used RGO was regenerated using 2 % HCl and used for adsorption study. For TGN, fresh RGO showed the adsorption capacity of 414.80 mg/g for 700 ppm dye solution while the regenerated RGO of 1st, 2nd, 3rd and 4th recycle showed the adsorption capacities of 143.03 mg/g, 135.23 mg/g, 111.28 mg/g and 82.53 mg/g. Part 3 describes the preparation of sodium-alginate (SA) and GO composite (SA-GO), characterization and its application for the removal of dye Maxilon Blue (GRL) from aqueous solutions. Porous composite SA-GO was prepared by adding the mixture of sodiumalginate, CaCO3 and GO dropwise into 2% HCl. Sodium alginate and GO ratio was maintained as 10:1. Characterization of prepared composite was carried out by FTIR spectroscope, SEM and XRD. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dye on SA-GO composite surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir isotherm the adsorption capacity was found 1111.11 mg/g for Maxilon Blue (GRL) at pH of 7. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models. Analyzing the kinetic parametersit was seen that the pseudo-second order kinetic model showed better correlation compared to the pseudo-first-order model. The thermodynamic analyses are also carried out. From thermodynamic analyses Gibb’s free energy ∆Go values were found -5.27, -3.75 and -2.55 KJ mol-1 for dye Maxilon Blue (GRL) at 303K, 313K and 323K, respectively. These results confirm that the adsorption of the dye Maxilon blue on the composite is more spontaneous at lower temperature and was physical adsorption. The used SA-GO composite was regenerated using 2 % HCl and used for adsorption study. For MBG, fresh SA-GO composite showed the adsorption capacity of 874.26 mg/g for 900 ppm dye solution while the regenerated SA-GO of 1st, 2nd , 3rd , 4thand 5th recycle showed the adsorption capacities of 683.27 mg/g, 667.84 mg/g, 664.31 mg/g, 653.43 mg/g and 657.38 mg/g. Finally, the conclusions and scope of further works are Chapter 2), Materials and Methods (Chapter 3), Results and Discussion (Chapter 4) and Conclusions (Chapter 5). Background and objectives of the study has been discussed in Chapter 1 and the literature reviews related to the research are elaborated in Chapter 2. Chapter 3 represents information about the materials used in this research. Here the methods and different equations and models used for the research are also stated. Chapter 4 deals with main research work and it is divided into three parts. Part 1 describes the synthesis, characterization of graphene oxide (GO) and its application for the removal of industrially used two synthetic anionic dyes such as FD-R H/C, TURQUOISE GN and one cationic dye, Maxilon Blue (GRL) from aqueous solutions. Here, GO was prepared from graphite powder by modified Hummer’s method. Characterization of prepared GO was carried out by FTIR spectroscope, Raman spectroscope, ESEM, AFM, XRD and elemental analysis. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dyes on GO surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir isotherm the adsorption capacity was found 151.29 mg/g for FD-R H/C at pH of 2. For TURQUOISE GN the adsorption capacities were 565.61 mg/g and 294.12 mg/g at pH of 2 and 7, respectively. For Maxilon Blue (GRL) the adsorption capacity was 1253.13 mg/g at pH of 7.The experimental data were analyzed using pseudofirst-order and pseudo-second-order models. Analyzing the kinetic parameters it was found that the pseudo-second order kinetic model showed better correlation compared to the pseudo-first-order model. The thermodynamic analyses are also carried out. From thermodynamic analyses Gibb’s free energy ∆Go values were found -1.69, -1.17 and -0.86 KJ mol-1 for dye FD-R H/C at 303K, 313K and 323K, respectively. While for TURQUOISE GN, ∆Go values were -3.66, -2.92, -2.39 KJ mol-1 and for Maxilon Blue (GRL) ∆Go values were -4.11, -3.80, -2.77 KJ mol-1 at 303K, 313K and 323K, respectively. These results confirm that the adsorption of the dyes on GO are more spontaneous at lower temperature and were physical adsorption.The used GO was regenerated using 2 % HCl and used for adsorption study. For dye TGN, fresh GO showed the adsorption capacity of 102.39 mg/g for 200 ppm dye solution while the regenerated GO of 1st, 2nd, 3rd and 4th recycle showed the adsorption capacities of 75.91 mg/g, 65.73 mg/g, 44.32 mg/g and 41.25 mg/g. For dye MBG, fresh GO showed the adsorption capacity of 1421.10 mg/g for 1000 ppm dye solution while the regenerated GO of 1st, 2nd and 3rd recycle showed the adsorption capacities of 1066.06 mg/g, 792.50 mg/g and 713.18 mg/g. Part 2 describes the synthesis, characterization of reduced graphene oxide (RGO) and its application for the removal of dye TURQUOISE GN from aqueous solutions. RGO was prepared by reduction of GO using hydrazine hydrate. Characterization of prepared RGO was carried out by ESEM, Raman spectroscope, XRD and elemental analysis. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dye on RGO surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir model the adsorption capacity was found 588.24 mg/g for TURQUOISE GN at pH of 7. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models. Analyzing the kinetic parameters it was found that the pseudo-second order kinetic model showed better correlation compared to the pseudo-firstorder model. The used RGO was regenerated using 2 % HCl and used for adsorption study. For TGN, fresh RGO showed the adsorption capacity of 414.80 mg/g for 700 ppm dye solution while the regenerated RGO of 1st, 2nd, 3rd and 4th recycle showed the adsorption capacities of 143.03 mg/g, 135.23 mg/g, 111.28 mg/g and 82.53 mg/g. Part 3 describes the preparation of sodium-alginate (SA) and GO composite (SA-GO), characterization and its application for the removal of dye Maxilon Blue (GRL) from aqueous solutions. Porous composite SA-GO was prepared by adding the mixture of sodiumalginate, CaCO3 and GO dropwise into 2% HCl. Sodium alginate and GO ratio was maintained as 10:1. Characterization of prepared composite was carried out by FTIR spectroscope, SEM and XRD. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dye on SA-GO composite surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir isotherm the adsorption capacity was found 1111.11 mg/g for Maxilon Blue (GRL) at pH of 7. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models. Analyzing the kinetic parametersit was seen that the pseudo-second order kinetic model showed better correlation compared to the pseudo-first-order model. The thermodynamic analyses are also carried out. From thermodynamic analyses Gibb’s free energy ∆Go values were found -5.27, -3.75 and -2.55 KJ mol-1 for dye Maxilon Blue (GRL) at 303K, 313K and 323K, respectively. These results confirm that the adsorption of the dye Maxilon blue on the composite is more spontaneous at lower temperature and was physical adsorption. The used SA-GO composite was regenerated using 2 % HCl and used for adsorption study. For MBG, fresh SA-GO composite showed the adsorption capacity of 874.26 mg/g for 900 ppm dye solution while the regenerated SA-GO of 1st, 2nd , 3rd , 4thand 5th recycle showed the adsorption capacities of 683.27 mg/g, 667.84 mg/g, 664.31 mg/g, 653.43 mg/g and 657.38 mg/g. Finally, the conclusions and scope of further works are Chapter 2), Materials and Methods (Chapter 3), Results and Discussion (Chapter 4) and Conclusions (Chapter 5). Background and objectives of the study has been discussed in Chapter 1 and the literature reviews related to the research are elaborated in Chapter 2. Chapter 3 represents information about the materials used in this research. Here the methods and different equations and models used for the research are also stated. Chapter 4 deals with main research work and it is divided into three parts. Part 1 describes the synthesis, characterization of graphene oxide (GO) and its application for the removal of industrially used two synthetic anionic dyes such as FD-R H/C, TURQUOISE GN and one cationic dye, Maxilon Blue (GRL) from aqueous solutions. Here, GO was prepared from graphite powder by modified Hummer’s method. Characterization of prepared GO was carried out by FTIR spectroscope, Raman spectroscope, ESEM, AFM, XRD and elemental analysis. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dyes on GO surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir isotherm the adsorption capacity was found 151.29 mg/g for FD-R H/C at pH of 2. For TURQUOISE GN the adsorption capacities were 565.61 mg/g and 294.12 mg/g at pH of 2 and 7, respectively. For Maxilon Blue (GRL) the adsorption capacity was 1253.13 mg/g at pH of 7.The experimental data were analyzed using pseudofirst-order and pseudo-second-order models. Analyzing the kinetic parameters it was found that the pseudo-second order kinetic model showed better correlation compared to the pseudo-first-order model. The thermodynamic analyses are also carried out. From thermodynamic analyses Gibb’s free energy ∆Go values were found -1.69, -1.17 and -0.86 KJ mol-1 for dye FD-R H/C at 303K, 313K and 323K, respectively. While for TURQUOISE GN, ∆Go values were -3.66, -2.92, -2.39 KJ mol-1 and for Maxilon Blue (GRL) ∆Go values were -4.11, -3.80, -2.77 KJ mol-1 at 303K, 313K and 323K, respectively. These results confirm that the adsorption of the dyes on GO are more spontaneous at lower temperature and were physical adsorption.The used GO was regenerated using 2 % HCl and used for adsorption study. For dye TGN, fresh GO showed the adsorption capacity of 102.39 mg/g for 200 ppm dye solution while the regenerated GO of 1st, 2nd, 3rd and 4th recycle showed the adsorption capacities of 75.91 mg/g, 65.73 mg/g, 44.32 mg/g and 41.25 mg/g. For dye MBG, fresh GO showed the adsorption capacity of 1421.10 mg/g for 1000 ppm dye solution while the regenerated GO of 1st, 2nd and 3rd recycle showed the adsorption capacities of 1066.06 mg/g, 792.50 mg/g and 713.18 mg/g. Part 2 describes the synthesis, characterization of reduced graphene oxide (RGO) and its application for the removal of dye TURQUOISE GN from aqueous solutions. RGO was prepared by reduction of GO using hydrazine hydrate. Characterization of prepared RGO was carried out by ESEM, Raman spectroscope, XRD and elemental analysis. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dye on RGO surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir model the adsorption capacity was found 588.24 mg/g for TURQUOISE GN at pH of 7. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models. Analyzing the kinetic parameters it was found that the pseudo-second order kinetic model showed better correlation compared to the pseudo-firstorder model. The used RGO was regenerated using 2 % HCl and used for adsorption study. For TGN, fresh RGO showed the adsorption capacity of 414.80 mg/g for 700 ppm dye solution while the regenerated RGO of 1st, 2nd, 3rd and 4th recycle showed the adsorption capacities of 143.03 mg/g, 135.23 mg/g, 111.28 mg/g and 82.53 mg/g. Part 3 describes the preparation of sodium-alginate (SA) and GO composite (SA-GO), characterization and its application for the removal of dye Maxilon Blue (GRL) from aqueous solutions. Porous composite SA-GO was prepared by adding the mixture of sodiumalginate, CaCO3 and GO dropwise into 2% HCl. Sodium alginate and GO ratio was maintained as 10:1. Characterization of prepared composite was carried out by FTIR spectroscope, SEM and XRD. The Langmuir and Freundlich isotherm models have been applied to explain the distribution of Dye on SA-GO composite surface. The results showed that the adsorption preferably followed the Langmuir model. From Langmuir isotherm the adsorption capacity was found 1111.11 mg/g for Maxilon Blue (GRL) at pH of 7. The experimental data were analyzed using pseudo-first-order and pseudo-second-order models. Analyzing the kinetic parametersit was seen that the pseudo-second order kinetic model showed better correlation compared to the pseudo-first-order model. The thermodynamic analyses are also carried out. From thermodynamic analyses Gibb’s free energy ∆Go values were found -5.27, -3.75 and -2.55 KJ mol-1 for dye Maxilon Blue (GRL) at 303K, 313K and 323K, respectively. These results confirm that the adsorption of the dye Maxilon blue on the composite is more spontaneous at lower temperature and was physical adsorption. The used SA-GO composite was regenerated using 2 % HCl and used for adsorption study. For MBG, fresh SA-GO composite showed the adsorption capacity of 874.26 mg/g for 900 ppm dye solution while the regenerated SA-GO of 1st, 2nd , 3rd , 4thand 5th recycle showed the adsorption capacities of 683.27 mg/g, 667.84 mg/g, 664.31 mg/g, 653.43 mg/g and 657.38 mg/g. Finally, the conclusions and scope of further works are outlined in chapter 5