Photocatalytic discoloration of Acid Red 14 aqueous solution using titania nanoparticles immobilized on graphene oxide fabricated plate.

Textile industry consumes remarkable amounts of water during various operations. A significant portion of the water discharge to environment is in the form of colored contaminant. The present research reports the photocatalytic degradation of anionic dye effluent using immobilized TiO2 nanoparticle on graphene oxide (GO) fabricated carbon electrodes. Acid Red 14 (AR 14) was used as model compound. Graphene oxide nanosheets were synthesized from graphite powder using modified Hummer's method. The nanosheets were characterized with field emission scanning electron microscope (FESEM) images, X-ray diffraction (XRD) and FTIR spectrum. The GO nanoparticles were deposited on carbon electrode (GO-CE) by electrochemical deposition (ECD) method and used as catalyst bed. TiO2 nanoparticles were fixed on the bed (GO-CE- TiO2) with thermal process. Photocatalytic processes were carried out using a 500 ml solution containing dye in batch mode. Each photocatalytic treatment were carried out for 120 min. Effect of dye concentration (mg/L), pH of solution, time (min) and TiO2 content (g/L) on the photocatalytic decolorization was investigated.

A novel Ag⁺ cation sensor based on polyamidoamine dendrimer modified with 1,8-naphthalimide derivatives.

In this study, 4-amino-1,8-naphthalimide-conjugated polyamidoamine dendrimer was synthesized and characterized and its potentiality as a cation sensor was investigated. 4-Amino-1,8-naphthalic anhydride reacted with polyamidoamine dendrimer and the product was characterized using FTIR, (1)H NMR, (13)C NMR and melting point analysis method. The synthesized compound was applied to detect various cations in water media and N,N-dimethylformamide (DMF) via monitoring the quenching of the fluorescence intensity. Furthermore, various metal cations including Cu(2+), Ni(2+), Zn(2+), Pb(2+),Ca(2+), Ba(2+), Cd(2+), Hg(2+), Fe(2+), Fe(3+) and Ag(+) were tested. The complexes formed between the synthesized compound and metal cations in solution and their effects on Photoinduced Electron Transfer (PET) process were investigated regarding the potential application of the newly-synthesized dendrimer as a colorimetric and fluorescent sensor for such cations. The results clearly confirmed that the 1,8-naphthalimide groups surrounding the central dendrimer core showed strong green fluorescence emission at 553 nm. This effect considerably decreased with the introduction of all cations, except Ag(+) where the fluorescence quenching effect was remarkable and more dominant. Therefore, it can be concluded that the synthesized dye has the potentiality of being a highly sensitive and selective fluorescence sensor for Ag(+) cation.

Ultrasonic mediated production of carboxymethyl cellulose: Optimization of conditions using response surface methodology.

In the present research the optimization of ultrasound-mediated production of carboxymethyl cellulose under microwave irradiation, towards achieving reduction of chemicals, time of reaction and energy was carried out. Cellulose was extracted and treated by environmentally friendly chlorine free bleaching method using hydrogen peroxide. Produced alpha-cellulose was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric/differential thermal analysis (TG/DTA). Response Surface Methodology (RSM) was used to optimize the preparation of carboxymethyl cellulose (CMC). Highest degree of substitution 0.74 was obtained at 240 W ultrasonic power for 37 min followed by etherification at 490 W microwave power for 12 min. Results show that the preparation of CMC from cotton linter using ultrasound and microwave energy can reduce the processing time, chemicals and energy consumption. Additionally, X-ray analysis shows that the ultrasonic energy is able to break cellulose crystals into smaller parts compared to other methods. SEM photographs showed that this treatment is able to remove impurities from raw material.

Removal of reactive blue 19 from aqueous solution by pomegranate residual-based activated carbon: optimization by response surface methodology.

BACKGROUND: In this research, response surface methodology (RSM) was applied to optimize Reactive Blue 19 removal by activated carbon from pomegranate residual. A 24 full factorial central composite design (CCD) was applied to evaluate the effects of initial pH, adsorbent dose, initial dye concentration, and contact time on the dye removal efficiency. METHODOLOGY: The activated carbon prepared by 50 wt.% phosphoric acid activation under air condition at 500°C. The range of pH and initial dye concentration were selected in a way that considered a wide range of those variables. Furthermore, the range of contact time and adsorbent dose were determined based on initial tests. Levels of selected variables and 31 experiments were determined. MiniTab (version 16.1) was used for the regression and graphical analyses of the data obtained. RESULTS: It was found that the decrease of initial dye concentration and the increase of initial pH, adsorbent dose, and contact time are beneficial for improving the dye removal efficiency. Analysis of variance (ANOVA) results presented high R2 value of 99.17% for Reactive Blue 19 dye removal, which indicates the accuracy of the polynomial model is acceptable. CONCLUSIONS: Initial pH of 11, adsorbent dose of 1.025 g/L, initial dye concentration of 100 mg/L, and contact time of 6.8 minutes found to be the optimum conditions. Dye removal efficiency of 98.7% was observed experimentally at optimum point which confirmed close to model predicted (98.1%) result.

Preparation and characterization of chitosan/feldspar biohybrid as an adsorbent: optimization of adsorption process via response surface modeling.

Chitosan/feldspar biobased beads were synthesized, characterized, and tested for the removal of Acid Black 1 dye from aquatic phases. A four-factor central composite design (CCD) accompanied by response surface modeling (RSM) and optimization was used to optimize the dye adsorption by the adsorbent (chitosan/feldspar composite) in 31 different batch experiments. Independent variables of temperature, pH, initial dye concentration, and adsorbent dose were used to change to coded values. To anticipate the responses, a quadratic model was applied. Analysis of variance (ANOVA) tested the significance of the process factors and their interactions. The adequacy of the model was investigated by the correlation between experimental and predicted data of the adsorption and the calculation of prediction errors. The results showed that the predicted maximum adsorption amount of 21.63 mg/g under the optimum conditions (pH 3, temperature 15°C, initial dye concentration 125 mg/L, and dose 0.2 g/50 mL) was close to the experimental value of 19.85 mg/g. In addition, the results of adsorption behaviors of the dye illustrated that the adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Langmuir sorption capacity was found to be 17.86 mg/g. Besides, thermodynamic parameters were evaluated and revealed that the adsorption process was exothermic and favourable.

Optimization of Acid Black 172 decolorization by electrocoagulation using response surface methodology.

This paper utilizes a statistical approach, the response surface optimization methodology, to determine the optimum conditions for the Acid Black 172 dye removal efficiency from aqueous solution by electrocoagulation. The experimental parameters investigated were initial pH: 4-10; initial dye concentration: 0-600 mg/L; applied current: 0.5-3.5 A and reaction time: 3-15 min. These parameters were changed at five levels according to the central composite design to evaluate their effects on decolorization through analysis of variance. High R2 value of 94.48% shows a high correlation between the experimental and predicted values and expresses that the second-order regression model is acceptable for Acid Black 172 dye removal efficiency. It was also found that some interactions and squares influenced the electrocoagulation performance as well as the selected parameters. Optimum dye removal efficiency of 90.4% was observed experimentally at initial pH of 7, initial dye concentration of 300 mg/L, applied current of 2 A and reaction time of 9.16 min, which is close to model predicted (90%) result.

Synthesis, characterization and dye removal ability of high capacity polymeric adsorbent: polyaminoimide homopolymer.

In this paper, polyaminoimide homopolymer (PAIHP) was synthesized and its dye removal ability was investigated. Physical characteristics of PAIHP were studied using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Direct Red 31 (DR31), Direct Red 23 (DR23), Direct Black 22 (DB22) and Acid Blue 25 (AB25) were used as model compounds. The kinetic and isotherm of dye adsorption were studied. The effect of operational parameter such as adsorbent dosage, pH and salt on dye removal was evaluated. Adsorption kinetic of dyes followed pseudo-second order kinetics. The maximum dye adsorption capacity (Q(0)) of PAIHP was 6667 mg/g, 5555 mg/g, 9090 mg/g and 5882 mg/g for DR31, DR23, DB22 and AB25, respectively. It was found that adsorption of DR31, DR23, DB22 and AB25 onto PAIHP followed with Langmuir isotherm. Dye desorption tests (adsorbent regeneration) showed that the maximum dye release of 90% for DR31, 86% for DR23, 87% for DB22 and 90% for AB25 were achieved in aqueous solution at pH 12. The results showed that the PAIHP as a polymeric adsorbent with high dye adsorption capacity might be a suitable alternative to remove dyes from colored wastewater.

Novel biocompatible composite (Chitosan-zinc oxide nanoparticle): preparation, characterization and dye adsorption properties.

In this paper, the preparation, characterization and dye adsorption properties of novel biocompatible composite (Chitosan-zinc oxide nanoparticle) (CS/n-ZnO) were investigated. Zinc oxide nanoparticles were immobilized onto Chitosan. Physical characteristics of CS/n-ZnO were studied using Fourier transform infra-red (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDX). Two textile dyes, Direct Blue 78 (DB78) and Acid Black 26 (AB26), were used as model compounds. The effect of CS/n-ZnO doses, initial dye concentration, salt and pH were elucidated at 20+/-1 degrees C. The isotherm and kinetics of dye adsorption were studied. The presence of functional groups such as hydroxyl, amino and carbonyl groups were detected. Results showed zinc oxide nanoparticles were immobilized onto Chitosan. The data were evaluated for compliance with the Langmuir, Freundlich and Tempkin isotherm models. It was found that AB26 and DB78 followed with Langmuir and Tempkin isotherms, respectively. In addition, adsorption kinetics of both dyes was found to conform to pseudo-second order kinetics. Based on the data of present investigation, one could conclude that the CS/n-ZnO being a biocompatible, eco-friendly and low-cost adsorbent might be a suitable alternative for elimination of dyes from colored aqueous solutions.

Grafting of chitosan as a biopolymer onto wool fabric using anhydride bridge and its antibacterial property.

Weak binding of chitosan on the wool constitutes the main problem in its application. In this paper, the surface modification of wool fabric using anhydrides to graft the chitosan was studied. Weight gain, antibacterial and antifelting properties of the chitosan grafted-acylated wool fabric were investigated. Wool fabrics were acylated with two anhydrides, succinic anhydride (SA) and phthalic anhydride (PA), using different solvents (dimethylsulfoxide (DMSO) and N,N-dimethyl formamide (DMF)). The effects of anhydrides, solvents, anhydride concentration, liquor ratio (L:R) and reaction time on acylation of wool were investigated. Chitosan was grafted to the acylated wool and the effects of pH, chitosan concentration, and reaction time on chitosan grafting of acylated wool were evaluated. Fourier transform infra-red (FTIR), scanning electron microscope (SEM), differential scanning colorimetry (DSC) and weight gain analyses provided evidence that chitosan was grafted on to the acylated wool through the formation of new covalent bonds. The grafted samples have antibacterial potential due to existence of the antibacterial property of chitosan. In addition, the chitosan grafted-acylated wool samples have antifelting property. The findings of this research support the potential production of new environmentally friendly textile fabrics.

Degradation and toxicity reduction of textile wastewater using immobilized titania nanophotocatalysis.

The feasibility and performance of photocatalytic degradation and toxicity reduction of textile dye (Acid Blue 25) have been studied at pilot scale in an immobilized titania nanoparticle photocatalytic reactor. UV-Vis, Ion Chromatography (IC) and chemical oxygen demand (COD) analyses were employed to obtain the details of the photocatalytic dye degradation. The effects of operational parameters such as H2O2, pH and dye concentration on the photocatalytic degradation of Acid Blue 25 were investigated. The aliphatic carboxylic acid intermediates and inorganic anions generated during the dye degradation process were analyzed. Daphnia magna bioassay has been used to test the progress of toxicity during the treatment process. Total disappearance of dye was attained. During the photocatalytic treatment process, the residual acute toxicity was reduced. The results showed that immobilized titania nanophotocatalysis capable to degradation and toxicity reduction of acid dye textile wastewater.

Photocatalytic degradation of agricultural N-heterocyclic organic pollutants using immobilized nanoparticles of titania.

Degradation and mineralization of two agricultural organic pollutants (Diazinon and Imidacloprid as N-heterocyclic aromatics) in aqueous solution by nanophotocatalysis using immobilized titania nanoparticles were investigated. Insecticides, Diazinon and Imidacloprid, are persistent pollutants in agricultural soil and watercourses. A simple and effective method was developed to immobilization of titania nanoparticles. UV-vis, ion chromatography (IC) and chemical oxygen demand (COD) analyses were employed. The effects of operational parameters such as H(2)O(2) and inorganic anions (NO(3)(-), Cl(-) and SO(4)(2-)) were investigated. The mineralization of Diazinon and Imidacloprid was evaluated by monitoring of the formed inorganic anions. The selected pollutants are effectively degraded following first order kinetics model. Results show that the nanophotocatalysis using immobilized titania nanoparticle is an effective method for treatment Diazinon and Imidacloprid from contaminated water.

Investigation on the adsorption capability of egg shell membrane towards model textile dyes.

Adsorption isotherms of Direct Red 80 (DR80) and Acid Blue 25 (AB25) on the egg shell membrane (ESM) were performed at 20+/-1 degrees C. Physical characteristics of ESM such as surface area and presence of functional groups were verified. The Fourier transform infra-red (FTIR) spectra proved the presence of functional groups such as hydroxyl, amine and carbonyl groups in ESM. The surface area of ESM was found to be 2.2098 m(2)/g. The effects of operational parameters such as initial dye concentration, pH(0), contact time, particle size and ESM doses were studied. The Langmuir, Freundlich, BET, Redlich-Peterson and Temkin adsorption models were applied to describe the equilibrium isotherms. The pseudo-first-order and pseudo-second-order kinetics models were examined to evaluate the kinetics data at different pH(0) values (2-12) and the rate constants were calculated. Maximum desorption of 81.8% was achieved for both dyes in aqueous solution at pH(0) 12. Also scanning electron micrographs (SEM) of the treated and untreated adsorbent were performed. Results indicate that ESM could be employed as a natural and Eco-Friendly adsorbent material for the removal of trace organics in solutions.

Equilibrium and kinetics studies for the adsorption of direct and acid dyes from aqueous solution by soy meal hull.

This paper deals with the application of Soy Meal Hull (SMH), an agricultural by-product, for the removal of direct and acid dyes from aqueous solutions. Four textile dyes, C.I. Direct red 80 (DR80), C.I. Direct red 81 (DR81), C.I. Acid blue 92 (AB92) and C.I. Acid red 14 (AR14) were used as model compounds. Physical characteristics of SMH such as surface area, Fourier transform infra-red (FTIR) and scanning electron microscopy (SEM) were obtained. The surface area of SMH was found to be 0.7623 m(2)/g and the presence of functional groups such as hydroxyl, amine and carbonyl groups were detected. The effect of initial dye concentration, pH, contact time and SMH doses were elucidated at 20+/-1 degrees C. Results show that the pH value of 2 is favorable for the adsorption of all four dyes. The data evaluated for compliance with the Langmuir, Freundlich and BET isotherm models. It was found that data for DR80 and DR81 fitted well with Langmuir isotherm, for AB92, BET isotherm is preferred, while for AR14, the Freundlich isotherm is the most applicable. The adsorption capacities of SMH for DR80, DR81, AB92 and AR14 were, 178.57, 120.48, 114.94 and 109.89 mg/g of adsorbent, respectively. Also, adsorption kinetics of dyes was studied and the rates of sorption were found to conform to pseudo-second order kinetics with good correlation (R(2)> or =0.9977). Maximum desorption of > or =99.8% was achieved for DR80, DR81 and AB92 and 86% for AR14 in aqueous solution at pH 10. Based on the data of present investigation, one could conclude that the SMH being a natural, eco-friendly and low-cost adsorbent with relatively large adsorption capacity might be a suitable local alternative for elimination of dyes from colored aqueous solutions.

Kinetics of heterogeneous photocatalytic degradation of reactive dyes in an immobilized TiO2 photocatalytic reactor.

The photocatalytic degradation of two reactive dyes has been investigated by UV/TiO2/H2O2 using an immobilized TiO2 photocatalytic reactor. Reactive Blue 8 (RB 8) and Reactive Blue 220 (RB 220) textile dyes were used as model compounds. Photocatalytic degradation processes were performed using a 5-L solution containing dyes. The initial concentrations of dyes were 50 mg/L. The radiation source was two 15 W UV-C lamps. A batch mode immersion photocatalytic reactor was utilized. UV-vis and ion chromatography (IC) analyses were employed to obtain the details of the photodegradation of the selected dyes. Colored synthetic waters were completely decolorized in relatively short time after UV irradiation in the presence of various concentrations of hydrogen peroxide. Formate, acetate, oxalate, and glyoxylate anions were detected as dominant aliphatic intermediates where they were further oxidized slowly to CO2. The UV/TiO2/H2O2 process was able to oxidize the dyes with partial mineralization of carbon, nitrogen, and sulfur heteroatoms into CO2, NO3-, and SO4(2-), respectively. Kinetics analysis indicates that the photocatalytic decolorization rates of the dye can be approximated by a pseudo-first-order model. The UV/TiO2/H2O2 process proved to be capable of decolorization and mineralization of the reactive dyes (RB 8 and RB 220).

Photocatalytic degradation of triazinic ring-containing azo dye (Reactive Red 198) by using immobilized TiO2 photoreactor: bench scale study.

The decolorization and degradation of triazinic ring-containing azo dye by using TiO(2)-immobilized photoreactor is reported. A simple and easy method was used for the immobilization of photocatalyst. Reactive Red 198 (RR 198) was used as model compound. Photocatalytic degradation processes were performed using a 5 L (bench scale) solution containing dye. Batch mode immersion type method was used for the treatment of dye solution. UV-vis, ion chromatography (IC) and chemical oxygen demand (COD) analyses were employed to evaluate the results of the photocatalytic degradation of RR 198. Dye solution was completely decolorized in relatively short time (35 min) after UV irradiation in combination with hydrogen peroxide. The results verified that all of the dye molecules were destructed. Kinetics analysis indicates that the dye photocatalytic decolorization rates followed first order model (R(2) = 0.99). Ion chromatography analysis was used to investigate the formation and destruction of aliphatic carboxylic acids and formation of inorganic anions during the process. Formate and oxalate anions were detected as main aliphatic carboxylic intermediates, which were further oxidized slowly to CO(2). UV/TiO(2)/H(2)O(2) process proved to be capable of successful decolorization and degradation of the RR 198.

Removal of dyes from colored textile wastewater by orange peel adsorbent: equilibrium and kinetic studies.

The use of low-cost and ecofriendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. Orange peel was collected from the fields of orange trees in the north of Iran and converted into a low-cost adsorbent. This paper deals with the removal of textile dyes from aqueous solutions by orange peel. Direct Red 23 (DR23) and Direct Red 80 (DR80) were used as model compounds. The adsorption capacity Q0 was 10.72 and 21.05 mg/g at initial pH 2. The effects of initial dye concentration (50, 75, 100, 125 mg/l), pH, mixing rate, contact time, and quantity of orange peel have been studied at 25 degrees C. The Langmuir and Freundlich models were used for this study. It was found that the experimental results show that the Langmuir equation fit better than the Freundlich equation. The results indicate that acidic pH supported the adsorption of both dyes on the adsorbent. Orange peel with concentrations of 8 and 4 g/l has shown adsorption efficiencies of about 92 and 91% for DR23 and DR80, respectively. Furthermore, adsorption kinetics of both dyes was studied and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R > or = 0.998). Maximum desorption of 97.7% for DR23 and 93% for DR80 were achieved in aqueous solution at pH 2. Finally, the effect of adsorbent surface was analyzed by scanning electron microscope (SEM). SEM images showed reasonable agreement with adsorption measurements.