Anionic Azo Dye Research Articles

Aluminum carboxylate-based metal organic frameworks for effective adsorption of anionic azo dyes from aqueous media

High quantities of synthetic dyes are prevalent in wastewater, which are disposed into the environment without proper treatment. In this work, two types of aluminum based metal-organic frameworks, Al-FA (fumaric acid) and Al-SA (succinic acid), were synthesized using water as the solvent and employed for the adsorption of mono and di-azo dyes. Al-SA exhibited superior affinities towards both substrates compared to those of Al-FA, with maximum adsorption capacities of 559.28 and 332.48mg/g for mono and di-azo dyes, respectively. Overall findings insinuate that Al-SA can be considered as a promising candidate for efficient azo dye removing agent.

A Cationic Coordination Polymer and Its Orange II Anion-Exchanged Products: Isolation, Structural Characterization, Photocurrent Responses, and Dielectric Properties.

Solvothermal reactions of AgNO3 with N1,N4-bis(5-fluoropyridin-3-yl)succinamide (bfps) in MeCN afforded the one-dimensional cationic coordination polymer {[Ag(bfps)]NO3}n (1). Upon treatment of 1 with the anionic azo dye orange II (NaOII) in aqueous solution, the NO3- anions of 1 could be gradually exchanged by the OII- anions via an anion-exchange process. The resulting OII anion-exchanged products {[Ag(bfps)](NO3)0.85(OII)0.15}n (2) and {[Ag(bfps)](NO3)0.1(OII)0.9}n (3) were formed by different molar ratios of 1 and the newly formed phase "{[Ag(bfps)](OII)}n" (4), confirmed by PXRD patterns. Relative to those of the precursors 1 and NaOII, complexes 2 and 3 demonstrated enlarged photocurrent responses and reduced dielectric constants and dielectric losses, which could be correlated with the OII- contents in their structures. Complex 3 acquired a stable anodic photocurrent of 12.06 μA, which was 4.9 times higher than that of 1. The dielectric constant (εr = 4.2) and dielectric loss (0.002) of 3 were nearly frequency independent in the range from 1 to 106 Hz. The results provide an interesting insight into the rational assembly of CP-dye complexes and their tunable optoelectronic applications.

Single, simultaneous and consecutive biosorption of Cr(VI) and Orange II onto chemically modified masau stones

Novel and low cost chemically modified masau stone (CMMS) was investigated for its biosorption of an anionic azo dye, Orange II (OII), and toxic hexavalent chromium (Cr(VI)) from aqueous systems: individually, simultaneously and consecutively. XPS and FTIR analyses indicated the introduction of quaternary-Nitrogen to the CMMS surface after activation with epichlorohydrin (etherifying agent) and diethylenetriamine (crosslinking agent). The effects of pH, contact time and initial concentration (Co), and loading order on mechanisms of biosorption/reduction of OII and Cr(VI) onto CMMS were examined in detail. Several analytical techniques were employed to characterise the physio-chemical properties of the CMMS and determine the biosorption mechanisms. The pseudo second order and redox models were able to adequately predict the kinetics of biosorption. The Langmuir maximum OII biosorption capacity (qmax) was calculated as 136.8 mg/g for the dye onto the Cr(VI)-loaded CMMS consecutive system at Co = 100 mg/dm3. The qmax for the Cr(VI) system was found to be 87.32 mg/g at the same Co max. This reveals that the biosorption of OII and Cr(VI) mainly takes place via two different mechanisms i.e. hydrogen bonding and electrostatic attraction for the dye, and biosorption-coupled reduction for Cr(VI).

Adsorptive removal of anionic azo dye from aqueous solution using activated carbon derived from extracted coffee residues

This study reports the synthesis of activated carbon derived from extracted coffee residues (AC-ECRs) via wet impregnation using different ratios of potassium hydroxide as an activating agent. The influence of the impregnation ratio on physicochemical properties such as surface characteristics, structural properties, and energetic heterogeneity were evaluated using nitrogen adsorption isotherms and adsorption energy distributions (AEDs). The overall porosity and energetic heterogeneity were improved with increasing impregnation ratio, resulting in a positive impact towards the adsorption capacity of substrate. Particularly, the correlation between AEDs and adsorption capacity clearly indicated that mesopore distribution plays an essential role on the adsorption capacity of acid orange 7 as a wider pore size offers more favorable conditions for adsorbing the substrate. This is the first report documenting the effect of impregnation ratio on surface heterogeneity and the correlation between AEDs and adsorption capacity of an azo dye. Adsorption kinetics and equilibrium isotherm studies insinuate that the overall process follows the pseudo-second-order and Sips isotherm models, respectively. Thermodynamic and isosteric heat of adsorption analyses revealed that the adsorption process was exothermic and is primarily governed via physisorption.

Synthesis of hexagonal mesoporous MgAl LDH nanoplatelets adsorbent for the effective adsorption of Brilliant Yellow

Hexagonal mesoporous MgAl layered double hydroxide (LDH) was synthesized through a simple hydrothermal method and was employed without calcination as adsorbent in the removal of the direct anionic azo dye, Brilliant Yellow (BY). The adsorbent was characterized by XRD, FT-IR, SEM and BET surface area. Hexagonal platelets of MgAl LDH were fabricated with nanometric building blocks. Batch experiments were carried out for study effects of contact time, amount of adsorbent, solution pH and solution temperature on the removal efficiency of BY. The adsorption of BY onto the MgAl LDH was pH dependent and the highest value of adsorption capacity was observed at pH=6. The equilibrium adsorption data were obtained using the Langmuir, Freundlich and Temkin isotherms. The results indicated that the experimental adsorption data were fitted to Langmuir and Freundlich models. The maximum adsorption capacity of BY onto the MgAl LDH was found to be 115mg/g. The kinetic data of adsorption were evaluated by pseudo-first order and pseudo-second order, which described well by pseudo-second order model. The negative values of ΔG° at all temperature indicated that the adsorption process was spontaneous. The values of ΔH° and ΔS° were calculated 19.3kJ/mol and 80.5J/mol·K, respectively. The positive value of ΔH° shows that the adsorption was endothermic, while positive ΔS° value reflects increased disorder at the solid–solution interface during the adsorption.

Transport of anionic azo dyes from aqueous solution to gemini surfactant-modified wheat bran: Synchrotron infrared, molecular interaction and adsorption studies

From the view of economic efficiency and technology sustainability, biomass adsorbent has a high potential for pollution control. In the present study, the performance of gemini 12-2-12 surfactant-modified wheat bran (MWB) for the removal of anionic azo dyes from aqueous solution was investigated. A new insight was gained into the modification mechanism through synchrotron-assisted infrared analysis and molecular interaction simulation. The equilibrium and kinetic studies for the adsorption of Acid Red 18 (AR-18), Acid Orange 7 (AO-7) and Acid Black 1 (AB-1) on MWB were conducted. The Langmuir model well fit the adsorption isotherm data. The adsorption kinetics could be described by the pseudo-second-order and intra-particle diffusion models. The results of thermodynamic studies indicated the adsorption of AR-18 and AB-1 onto MWB was endothermic and spontaneous, while the adsorption of AO-7 was exothermic. The optimum pH for the adsorption of anionic azo dyes on MWB was 3. The adsorbed amount of anionic azo dyes onto MWB decreased when NaCl concentration increased from 0 to 0.4molL−1. The potential of modified wheat bran as a suitable adsorbent for the removal of dyes from wastewater was presented in this study. The results can help understand the migration patterns of organic pollutants at wheat bran-water interface.

New Activated Carbon from Persian Mesquite Grain as an Excellent Adsorbent

This paper presents a systematic study of the surface chemistry, porous texture and adsorptive characteristics of prepared new activated carbon using Persian mesquite grain. Several techniques and methodologies such as, proximate analysis, N2 adsorption–desorption isotherms, scanning electron microscope (SEM), Fourier transform infrared spectroscopy(FT-IR), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy(XPS), temperature programmed desorption (TPD), Thermo gravimetric analysis TGA/DTA, elemental analysis(CHNS), Boehm titration, and point of zero charge (pHpzc) have been used to determine physicochemical properties of raw material and activated carbon respectively. The prepared activated carbon has been also used to remove methyl orange (MO) and methylene blue(MB) as anionic and cationic azo dyes.

Adsorption of anionic azo-dyes from aqueous solutions onto graphene oxide: Equilibrium, kinetic and thermodynamic studies

In the present study, graphene oxide (GO) was used for the adsorption of anionic azo-dyes such as Acid Orange 8 (AO8) and Direct Red 23 (DR23) from aqueous solutions. GO was characterized by Fourier Transform-Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and zeta potential measurements. The influence of dye initial concentration, temperature and pH on AO8 and DR23 adsorption onto GO was investigated. Equilibrium data were analyzed by model equations such as Langmuir Freundlich, Temkin, Dubinin-Radushkevich and Redlich-Peterson isotherms and were best represented by Langmuir and Redlich-Peterson isotherm model. Kinetic adsorption data were analyzed using the pseudo-first-order kinetic model, the pseudo-second-order kinetic model and the intraparticle diffusion model. The adsorption kinetics well fitted using a pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, were calculated, indicating that the adsorption of AO8 and DR23 onto GO was spontaneous process. The adsorption process of AO8 onto GO was exothermic, while the adsorption of DR23 onto GO was endothermic in nature.

Transport behaviors of anionic azo dyes at interface between surfactant-modified flax shives and aqueous solution: Synchrotron infrared and adsorption studies

From the viewpoint of sustainability, biomass adsorbent has a high potential in pollution control and there is an emerging interest to investigate the behaviors of pollutants at the interface between biomass adsorbent and solution. This study investigated the performance of cetyltrimethylammonium bromide surfactant-modified flax shives (MFS) for removal of anionic azo dyes from aqueous solution. The equilibrium and kinetic analysis for the adsorption of Acid Orange 7 (AO-7), Acid Red 18 (AR-18) and Acid Black 1 (AB-1) on MFS were conducted. The surface of MFS was characterized by synchrotron infrared and SEM analysis. The absorbed amount of three anionic azo dyes varied with the change of adsorbent dosage, pH and ionic strength. The adsorption isotherm data well fit to the Langmuir model. The adsorption process followed the pseudo-second-order kinetics and the liquid film diffusion models. Thermodynamic studies indicated that the adsorption of three anionic azo dyes was spontaneous. The adsorption of AR-18 and AB-1 onto MFS was endothermic while the adsorption of AO-7 was exothermic. The results can help better understand the behaviors of organic pollutants at biomass adsorbent-water interface. They also present the potential of using MFS as a suitable adsorbent for the removal of anionic azo dyes from wastewater.

Adsorption of anionic azo dye Congo Red from aqueous solution onto NaOH-modified jute fibre

Adsorption of anionic azo dye Congo Red from aqueous solution onto NaOH-modified jute fibre

ZnO-Layered Double Hydroxide@Graphitic Carbon Nitride Composite for Consecutive Adsorption and Photodegradation of Dyes under UV and Visible Lights.

In this work, a ZnO-layered double hydroxide@graphitic carbon nitride composite (ZnO-LDH@C3N4) was synthesized via co-precipitation method with solvothermal treatment. The structure and morphology of ZnO-LDH@C3N4 composite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopes/transmission electron microscopes (SEM/TEM), N2 adsorption/desorption, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis-DRS), photoluminescence spectrometer (PL) and electrochemical impedance spectroscopy (EIS). The adsorption and photocatalytic properties of ZnO-LDH@C3N4 composite towards the organic dyes: Orange II sodium salt (OrgII, an anionic azo dye) and methylene blue (MB, a cationic azo dye) were investigated. Compared to ZnO-LDH and g-C3N4, the ZnO-LDH@C3N4 composite displayed an excellent performance in both adsorption and photocatalytic degradation of the organic dyes. Moreover, a combination of ZnO-LDH and g-C3N4 significantly improved the photocatalytic performance of ZnO-LDH and g-C3N4 under visible-light irradiation. The adsorption and photocatalytic mechanism were also investigated.

Ionic liquid and surfactant functionalized ZnO nanoadsorbent for Recyclable Proficient Adsorption of toxic dyes from waste water

Herein, we report the synthesis, characterization and nanoadsorbent application of surfactant and ionic liquid functionalized ZnO nanoparticles prepared by microwave based synthetic method. The synthesized material was characterized in detail which revealed that the nanoparticles are well-crystalline, exhibiting superior optical properties with good adsorption tendency. The surface modified nanoparticles were used as nanoadsorbent for the removal of harmful dyes from waste water. Interestingly, it was observed that after functionalizing with ionic liquid and surfactants, the prepared nanoparticles exhibited better control over the size and shape and possesses improved adsorption ability towards anionic azo dye (BBR-250) as compared to bare ZnO nanoparticles. The kinetics as well as adsorption isotherm was also employed for getting essential information regarding the absorption efficiencies of the ZnO nanoparticles towards BBR-250. The absorption ability of ZnO nanoparticles has further checked in spiked water samples from different sources. The recovery, utility in real samples and reusability of the adsorbent and adsorbate has made the treatment more economical and applicable for industrial applications.

A novel green synthesis and characterization of silver nanoparticles using gum tragacanth and evaluation of their potential catalytic reduction activities with methylene blue and Congo red dyes

A facile and eco-friendly method for green synthesis of silver nanoparticles (AgNPs) has been developed using gum tragacanth (GT) (Astragalus gummifer), an abundantly available natural phyto-exudate in India, employing a novel method of ultrasonication process. Silver nanoparticles were prepared by the reduction of silver nitrate solution by the aqueous extract of gum tragacanth by ultrasonication method at 45 °C for about 45 min. The aqueous extract of the gum acts as a reducing as well as stabilizing agent. The resultant AgNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The influence of gum concentration and silver precursor concentration on the synthesis of AgNPs was studied. The role and effectiveness of nanoparticles in the catalytic reduction of a cationic dye methylene blue (MB), and an anionic azo dye Congo red (CR), were also studied. FTIR analysis revealed that –OH groups present in the gum matrix might be responsible for the reduction of Ag+ into AgNPs. The X-ray diffraction studies indicated that the resulting AgNPs were highly crystalline with face-centered cubic geometry. TEM studies showed that the average particle size of the synthesized AgNPs was 18 ± 2 nm. The study highlights the green synthesis of GT-capped AgNPs and the rapid reduction of carcinogenic and toxic contaminants such as MB and CR with the help of GT-capped AgNPs in an eco-friendly manner.

Chitosan-based microparticles for immobilization of TiO2 nanoparticles and their application for photodegradation of textile dyes

The present paper deals with removal and photocatalytic degradation of the textile dyes by TiO2 nanoparticles immobilized onto chitosan-based microparticles. The microparticles composed of chitosan (Ch) and poly(methacrylic acid) (PMA) were fabricated for the first time by inverse suspension polymerization. They were utilized for colloidal TiO2 nanoparticles immobilization, synthetized by acidic hydrolysis of TiCl4. To evaluate the potential application of Ch/PMA/TiO2 microparticles for treatment of textile wastwaters, their photocatalytic activity was examined by degradation assessment of three different groups of anionic azo dyes in aqueous solutions under solar light simulating source. FTIR analysis revealed that Ch and PMA were incorporated in the polymer network. SEM and optical microscopy confirmed their spherical shape. Under illumination, Ch/PMA/TiO2 microparticles completely removed dyes C.I. Acid Orange 7, C.I. Acid Red 18, C.I. Acid Blue 113, C.I. Reactive Black 5, C.I. Direct Blue 78, while removal degree of C.I. Reactive Yellow 17 was 75%. It was found that pH had significant influence on the photocatalytic activity of Ch/PMA/TiO2 microparticles. Increase of solution pH from acidic to alkaline, lead to decrease in photodegradation rate of C.I. Acid Orange 7 during the first hours of illumination. After three illumination cycles, removal degree of C.I. Acid Orange 7 was maintained at remarkably high level (95% at pH 5.60 and 100% at pH 2.00 and 8.00), indicating that microparticles could be reused without significant loss of photocatalytic efficiency.

Adsorptive amputation of hazardous azo dye Congo red from wastewater: a critical review.

Increasing amount of dyes in an ecosystem has propelled the search of various methods for dye removal. Amongst all the methods, adsorption occupies a prominent place in dye removal. Keeping this in mind, many adsorbents used for the removal of hazardous anionic azo dye Congo red (CR) from aqueous medium were reviewed by the authors. The main objectives behind this review article are to assemble the information on scattered adsorbents and enlighten the wide range of potentially effective adsorbents for CR removal. Thus, CR sorption by various adsorbents such as activated carbon, non-conventional low-cost materials, nanomaterials, composites and nanocomposites are surveyed and critically reviewed as well as their sorption capacities are also compared. This review also explores the grey areas of the adsorption performance of various adsorbents with reference to the effects of pH, contact time, initial dye concentration and adsorbent dosage. The equilibrium adsorption isotherm, kinetic and thermodynamic data of different adsorbents used for CR removal were also analysed. It is evident from a literature survey of more than 290 published papers that nanoparticle and nanocomposite adsorbents have demonstrated outstanding adsorption capabilities for CR. Graphical abstract ᅟ.

Adsorption of anionic azo dye Congo Red from aqueous solution by Cationic Modified Orange Peel Powder

This study investigated the adsorption of Congo Red (CR), an anionic azo dye, from aqueous solution by using Cationic Modified Orange Peel Powder (CMOPP). The optimum conditions were determined by investigating the effects of pH, contact time, initial dye concentration and temperature. The adsorbent was characterized by FTIR analysis. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models. The maximum adsorption capacity of CR on CMOPP was estimated as 107, 144, and 163mg/g, respectively, at different temperatures (298, 308 and 318K). Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The kinetic results demonstrated that the adsorption of CR onto CMOPP was well described by pseudo-second-order kinetic model. The activation energy of adsorption (Ea) was found to be 30kJ/mol by using the Arrhenius equation. The calculated thermodynamic parameters (ΔGo, ΔHo and ΔSo) showed that the adsorption of CR onto CMOPP was feasible, spontaneous and endothermic. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CMOPP was desorbed using 0.1M NaOH. The results indicated that CMOPP can be considered as a potential adsorbent for the removal of CR from aqueous media.

A magnetic mesoporous chitosan based core‐shells biopolymer for anionic dye adsorption: Kinetic and isothermal study and application of ANN

ABSTRACTIn this study, Chitosan/Al2O3/Fe3O4 core‐shell composite microsphere (CAMF) was used as an effective sorbent with high adsorption capacity for the removal of anionic azo dye model from aqueous solution. The obtained composite was characterized by XRD, SEM, EDX, and BET analysis. The results showed the high methyl orange (MO) adsorption in a wide pH range of 4–10 and the optimum adsorbent dosage was obtained 0.6 g L−1. It is indicated that the equilibrium data followed the Langmuir isotherm model and the adsorption kinetic was well fitted with pseudo‐second‐order kinetic model. Also, the adsorption kinetic was controlled by the film diffusion and intra‐particle diffusion, simultaneously. It is revealed that by increasing the particle size from <0.1 μm to ∼0.4 μm, the adsorption capacity did not change, significantly. The adsorption capacity of MO on CAMF was predicted by multilayer perceptron (MLP) neural network at different initial MO concentration, in which the predictions of MLP model had very good agreement with experimental data. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43466.

Adsorption of cationic and anionic azo dyes on sepiolite clay: Equilibrium and kinetic studies in batch mode

In the present work, sepiolite clay adsorptive properties were investigated for textile azo dyes in aqueous solution. The clay (78wt.% sepiolite) was characterized in terms of physical, textural, chemical and mineralogical properties. Basic Red 46 and Direct Blue 85 azo dyes were selected as adsorbates. Adsorption equilibrium data were successfully fitted to Freundlich and Langmuir equations. For Basic Red, the maximum adsorption capacities, predicted by the Langmuir model, were 110mg/g (at 25°C) and 310mg/g (at 35°C). The value obtained at 25°C, matched perfectly the cation exchange capacity of the clay. For Direct Blue, the adsorption capacity was 332mg/g. Adsorption equilibrium was also evaluated for Direct Blue dye in a synthetic effluent, containing salt and auxiliary dyeing chemicals. In this mixture, the amount of dye adsorbed by sepiolite decreased, but very considerable values were still reached (106mg/g). Adsorption kinetics was studied and modeled. Homogeneous solid diffusion coefficient and effective pore diffusivities were calculated for both dyes. Sepiolite clay showed to be an advantageous adsorbent in terms of price and versatility, being effective under a wide pH range, for both anionic and cationic dyes. Its use as adsorbent does not require further purification or chemical modifications, which is beneficial for the environment and for the economy of the treatment.

Characterization and adsorption performance of chitosan/diatomite membranes for Orange G removal

AbstractNovel chitosan/diatomite (CS/DM) membranes were prepared by phase inversion technique to remove anionic azo dyes from wastewater. The fabricated composite membranes exhibited the combined advantages of inorganic substances, diatomites, and polysaccharides. These composite membranes were characterized through Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. The mechanical properties of the membranes were also evaluated. Adsorption experiments were conducted under varied initial dye concentration, solution pH values, contact time, and adsorbent dosage. The results indicate that pH 3 is the optimal pH value for Orange G adsorption. The CS/DM membranes exhibit the highest adsorption capacity of 588 mg g-1 and removal rate of 94% under an initial dye concentration of 200 mg l-1, contact time of 6 h, and membrane dosage of 8 mg. Langmuir, Freundlich and Redlich-Peterson adsorption models were applied to describe the equilibrium isotherms at different dye concentrations. The equilibrium data was found to be fitted well to the Redlich-Peterson isotherm. Pseudo-first-order and pseudo-second-order kinetics models were used to describe the adsorption of membranes. The adsorption data were well explained by pseudo-second-order models, and also followed by the Elovich model. In addition, these membranes display high adsorption capacity and mechanical performance even after reused for seven times.

Thermodynamic study of interaction between a cationic surfactant and an anionic azo dye in aqueous solution

Thermodynamic study of interaction between a cationic surfactant and an anionic azo dye in aqueous solution