Azo Dye Acid Research Articles

Adsorption of Azo Dye Acid Red 73 onto Rice Wine Lees: Adsorption Kinetics and Isotherms

The adsorption properties of rice wine lees for acid red 73 in aqueous solution were studied in order to explore the recyclability of rice wine lees and to solve the pollution of dye‐contaminated wastewater. Hence, the azo dye acid red 73 was selected as the model pollutant. Effects of parameters including pH, rice wine lees dosage, and initial concentration of acid red 73 on the adsorption activity were investigated to determine the optimal conditions for removal of acid red 73. The experimental results showed that acid red 73 removal by rice wine lees decreased with increasing pH and initial concentration of acid red 73 and increased with increasing rice wine lees dosage. The adsorption reaction was consistent with pseudo‐first‐order kinetic models, and the adsorption process was physisorption. The adsorption isotherm could be described well with the Freundlich equation, and the maximum adsorption capacity was 18.74 mg·g−1.

Auto combustion synthesis using grapefruit extract: photocatalyst and magnetic MgFe2O4-PbS nanocomposites

Magnesium ferrite (MgFe2O4) as a core magnetic nanostructure was synthesized via auto combustion method by using grapefruit extract as a biocompatible and cost-effective material. Then flower and star-like PbS were synthesized using thioglycolic acid as a sulfur source without using any chemical template. After that for preparation of magnetic and photocatalyst MgFe2O4-PbS nanocomposites, lead sulfide were coated on the magnetic core by hydrothermal procedure. Morphology of the prepared products was estimated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), also X-ray diffraction (XRD) pattern show purity and phase of the product. Fourier transforms infrared (FT-IR) spectroscopy show vibration modes of the bonds. Vibrating sample magnetometer (VSM) illustrated that magnesium ferrite nanoparticles have a soft magnetic behaviour with 18 emu/g magnetization and coercivity about 90Oe. The photocatalytic behaviour of MgFe2O4-PbS nanocomposites were examined using the degradation of two various azo dyes acid brown and acid violet under visible light irradiation. This magnetic photocatalyst can easily separate from water with an external magnetic field and can be used under solar irradiation.

Removal of Acid Yellow 36 and Rhodamine B from single and binary systems by reverse micelles

In the present study reverse micelles are employed to encapsulate ionic dyes such as, azo dye Acid Yellow 36 (AY36) also known as Metanil Yellow and cationic dye Rhodamine B (RhB). This method proved to be highly efficient in the removal of high concentrations of dyes as much as 40mg/100ml from aqueous solutions of single and binary systems. The effect of different parameters like initial dye concentration, surfactant concentration, pH and salt (KCl) concentration on the percentage removal of the dyes were studied. It was observed that the percentage removal for both anionic and cationic dye decreased with the increase in the initial dye concentration and increased with the increase in the surfactant concentration in case of both the dyes in single and binary systems. Further, it was noticed that for anionic dye the percentage removal increased with the increase of both pH and KCl concentration while the results were exactly the reverse in case of RhB dye which exists in both cationic and zwitterionic forms at pH above 4. In binary systems, it was found that the removal of RhB increased compared to its removal from single system, while the removal of AY36 decreased in binary system

Tratamiento fotocatalítico de una disolución acuosa de azocolorante Negro Ácido 52 utilizando como catalizador diferentes mezclas de óxidos semiconductores

In this study, the photocatalytic degradation of azo dye Acid Black 52 using different mixtures of semiconductor oxides as a catalyst is reported. The experimental system consisted of a Batch reactor in which the azo dye, the semiconductor oxides and the hydrogen peroxide were mixed, whose concentrations were 0.1 mM, 100 mg/L and 65.2 mM, respectively. The mixture was homogenized by a magnetic stirrer and the pH was adjusted to 3.0. The initial volume was 500 mL. A white light lamp (127 V, 60 Hz, 362 mA, 60 W, 60 lm/W) was placed coaxial to the reactor and turned on to activate the catalyst. Samples were taken every 30 minutes to measure the absorbance, for this purpose a HACH DR3900 spectrophotometer was used. After 180 minutes of treatment, the best result, 60% degradation of the azo dye, was obtained with the mixture manganese oxides-iron oxides. The purpose of this work was to completely transform the pollutant into carbon dioxide, to avoid its adverse effects on the environment and human health, using catalysts excited with visible radiation.

Oerskovia paurometabola can efficiently decolorize azo dye Acid Red 14 and remove its recalcitrant metabolite.

The biodegradation of dyes remains one of the biggest challenges of textile wastewater. Azo dyes are one of the most commonly employed dye classes, and biological treatment processes tend to generate recalcitrant aromatic amines, which are more toxic than the parent dye molecule. This study aimed to isolate bacterial strains with the capacity to degrade both the azo dye and the resulting aromatic amines towards the development of a simple and reliable treatment approach for dye-laden wastewaters. A mixed bacterial enrichment was first developed in an anaerobic-aerobic lab-scale sequencing batch reactor (SBR) fed with a synthetic textile wastewater containing the model textile azo dye Acid Red 14 (AR14). Eighteen bacterial strains were isolated from the SBR, including members of the Acinetobacter, Pseudomonas and Oerskovia genera, Oerskovia paurometabola presenting the highest decolorization capacity (91% after 24h in static anaerobic culture). Growth assays supported that this is a facultative bacterium, and decolorization batch tests with 20-100mg AR14 L-1 in a synthetic textile wastewater supplemented with yeast extract indicated that O. paurometabola has a high color removal capacity for a significant range of AR14 concentrations. In addition, a model typically used to describe biodegradation of xenobiotic compounds was adjusted to the results, to predict AR14 biodegradation time profiles at different initial concentrations. HPLC analysis confirmed that decolorization occurred through azo bond reduction under anaerobic conditions, the azo dye being completely reduced after 24h of anaerobic incubation for the range of concentrations tested. Interestingly, partial (up to 63%) removal of one of the resulting aromatic amines (4-amino-naphthalene-1-sulfonic acid) was observed when subsequently subjected to aerobic conditions. Overall, this work showed the azo dye biodegradation potential of specific bacterial strains isolated from mixed culture bioreactors, reporting for the first time the decolorization capacity of an Oerskovia sp. with further biodegradation of a recalcitrant sulfonated aromatic amine metabolite.

Decolorization of Acid Red 1 using natural zeolite via heterogeneous fenton-like oxidation

Fenton process can be regarded as powerful and effective method in decolorization and mineralization of dye pollutants. However, this method is restricted with the generation of iron waste sludge which require secondary treatment. This limitation can be overcome by utilizing heterogeneous Fenton process where iron ions are immobilized onto the catalyst support. In the present study, the heterogeneous Fenton-like oxidation using Fe-natural zeolite (Fe-NZ) was investigated in decolorization of azo dye Acid Red 1 (AR1). The effects of iron ions loading, catalyst dose and initial pH on the decolorization of AR1 were evaluated. The maximum decolorization efficiency of 99.60% was achieved at 0.80 wt% of iron ions loading, 5.0 g/L of catalyst dose, and at 2.5 initial pH. The Fe-NZ showed high catalytic performance for decolorization of AR1 and could be regarded as a suitable low-cost catalyst in heterogeneous Fenton-like reaction.

Removal of Azo Dye Acid Red 27 from Aqueous Solutions Using Classical and Modified Fenton Reagent with Zero-Valent Iron

The article compares the classic Fenton reagent (Fe2+/H2O2) with its modification with zero-valent iron (ZVI/H2O2) to remove azo dye Acid Red 27 from aqueous solutions at a concentration of 100 mg/L. For both methods, the most favorable parameter values ​​were determined at which visual discoloration of the solutions tested was obtained (for Fe2+/H2O2:pH 3.5, H2O2=60 mg/L, Fe2+/H2O2=0.3, t=15 min, and for ZVI/H2O2: pH 3, H2O2=40 mg/L, ZVI=80 mg/L, t=15 min). Under these conditions, the COD value was reduced by 71.5% and 69.2% for the classic Fenton and its modification, respectively. A reduction in toxicity was also obtained for Vibrio fischeri bacteria to below 25% by using the Microtox test. ZVI digestion at acidic pH for 10 minutes allowed to shorten the reaction time by about four times - from 15 to 4 minutes. BET analysis showed that the specific surface area increases with the digestion time, which significantly accelerates the reaction. The visual discoloration of aqueous solutions was obtained, and the final COD values ​​were very small, ranging from 49-53 mg O2/L. According to the Vibrio fischeri toxicity classification test for water samples, all solutions of dyes tested can be considered as non-toxic (toxicity value <25%). In the study presented, results of decreasing the COD value and concentration of the dye in the ZVI/H2O2 method obtained are slightly worse compared to the Fe2+/H2O2 method. However, taking the decolorisation time as a criterion, a four times faster decolorisation time was obtained in the ZVI/H2O2 method, compared to the Fe2+/H2O2 method.

Spectrophotometric Determination of Benzethonium Chloride Using Some Chromotropic Acid Azo Dyes

Five simple, sensitive, rapid and accurate spectrophotometric methods were developed for the determination of benzethonium chloride in its pharmaceutical formulation. The proposed methods are based on ion-pairs formation of the drug with some chromotropic acid azo dyes such as arsenazo (I) (ARZO (I)), arsenazo (III) (ARZO (III)), SPADNS, chromotrope 2R (C2R) and chromotrope 2B (C2B) and subsequent extraction into methylene chloride. The extracts have maximum absorbance at 520, 540, 520, 530, and 520 nm respectively. The method of solvent extraction showed good sensitivity and wide linearity over a concentration range of 8.96-89.62, 4.48-44.81, 4.48-44.81, 4.48-44.81 and 8.96-89.62 µg/mL. Limits of detection 0.52, 1.07, 0.14, 0.62, and 0.77 µg/mL for ARZO (I), ARZO (III), SPADNS, C2R, and C2B, respectively. They were also used for the analysis of the antibacterial spray Dermoplast® with excellent recovery (95.88-102.45%) and relative standard deviation values (0.49-2.68%). The statistical analysis of the obtaine data was performed.

Degradation of Azo Dye (Acid Orange 7) in a Microbial Fuel Cell: Comparison Between Anodic Microbial-Mediated Reduction and Cathodic Laccase-Mediated Oxidation

More than 80 per cent of wastewater from industries is discharged into receiving water bodies without any pollution control. Microbial fuel cells (MFCs) are a promising technology for the simultaneous treatment of wastewater and electricity production. With regard to azo-dye containing wastewater (e.g. from textile manufacturing), the dye may be fed via the anode chamber containing electrochemically active bacteria or via the cathode chamber containing laccase enzyme as catalyst for oxygen reduction. This study investigated which of the two approaches is the best with regard to rate of decolourization of the dye (Acid orange 7), COD reduction and electricity production. The power density was higher for the MFCDye cathode (50±4 mW m-2, COD reduction 80.4±1.2%) compared with 42.5±2.6 mW m-2 (COD reduction 69±2%) for MFCDye anode. The time required for decolourization was longer in the MFCDye anode (Shewanella oneidensis) where only 20% decolourization was obtained after 24 h compared to 80% for the MFCDye cathode. The anodic dye degradation products were unstable when exposed to air resulting in regaining of colour. In case of degradation by laccase in the cathode chamber, the decolourization products were stable and simpler in chemical structure as determined by GC-MS. This work suggests that feeding azo dyes in cathode chambers of MFCs containing laccase is a better way of treating the dyes compared to the commonly used approach of feeding the dye in the anode chamber provided enzyme activity can be sustained.

Desulfonation of the textile azo dye Acid Fast Yellow MR by newly isolated Aeromonas hydrophila SK16

Acid Fast Yellow MR (AFYMR), a sulphonated reactive textile azo dye, was effectively decolorized by a newly identified bacterial strain Aeromonas hydrophila SK16. Nineteen isolates were obtained from the textile effluent polluted soil in Perundurai region. Maximum decolorization of AFYMR was observed in Aeromonas hydrophila SK16. Enzyme activities present in A. hydrophila SK16 revealed the involvement of oxidoreductase and efficiently decolorized 91.25% of AFYMR (100 mg L-l) in static condition for 9 h. Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that A. hydrophila SK16 cells preferred N–H and Sulphur dioxide bonds in the breakdown of AFYMR. The final metabolite supports the degradation of AFYMR through desulfonation as revealed by Gas Chromatography-Mass Spectroscopy (GCMS) results. Phytotoxicity studies conducted in Oryza sativa and Zea mays illustrated significant decrease in toxicity of metabolite produced during decolorization of Acid Fast Yellow MR by Aeromonas hydrophila SK16.

Biodecolorization of azo dye Acid Black 24 by Bacillus pseudomycoides: Process optimization using Box Behnken design model and toxicity assessment

Bacterial strain Bacillus pseudomycoides, isolated from domestic wastewater was used to decolorize azo dye Acid Black 24. Response Surface Methodology based on Box- Behnken model was used to optimize the conditions for maximum dye decolorization. High regression coefficient values (adjusted R2=0.9317 and predicted R2=0.8343) confirmed that the predicted values are in compliance with the experimental values implying the appropriateness of the employed polynomial regression model. The adequacy of the model was validated by different descriptive statistics viz. lack of fit, adequate precision, F and p values. 96.79% of dye decolorization was achieved at pH7, temperature 37°C and 40mgL−1 dye concentration. The activities of oxido-reductive enzymes like lignin peroxidase, laccase and azoreductase were found to be induced during the dye decolorization process. The biodegradation of the dye was assessed by HPLC, FTIR and UV spectroscopy. Genotoxicity and phytotoxicity studies substantiated the nontoxic nature of the degraded dye.

Hydrodynamics of up-flow hybrid anaerobic digestion reactors with built-in bioelectrochemical system

Understanding the electrode configuration is vital for the successful application of bioelectrochemical system (BES) in recalcitrant wastewater treatment. Especially in those traditional anaerobic processes that integrate with BES to construct effective hybrid bioreactors. Hybrid bioreactors employed granular graphite as electrode material achieved 86.62 ± 1.83% decolorization efficiency of azo dye acid orange 7 (AO7) at influent AO7 loading rate of 800 g/(m3∙d) and it was about 6% higher than that with carbon fiber brush electrodes. Such electrodes were positioned above the anaerobic sludge layer and higher efficiency (8%) than the reactors with electrodes placed beneath the sludge layer was observed. Tracer experiments and modeling of residence time distribution indicated that the fluid pattern in hybrid bioreactors was modified to plug flow pattern and had a better consummate mixing ability compared to the conventional anaerobic reactor. Simulation using computational fluid dynamics technique showcased favorable mass transfer near electrode modules. The hydrodynamics of simulation and experimental results were connected by simplifying electrode module as a porous media model. This study thus proved that hybrid bioreactors can effectively enhance wastewater treatment comprehensively through the analysis of decolorization performance and hydrodynamics.

New acid dyes and their metal complexes: dyeing, thermal and antifungal behavior

The present investigation is concerned with the synthesis of acid azo dye based on 1-Amino-2-naphthol-6-nitronaphthalene-4-sulphonic acid and its chromium, iron, cobalt, nickel and copper complexces. The structure of these complexes were analyzed by UV-Visible, FTIR, NMR and elemental analysis. The synthesized dyes were applied on leather to assess its fastness properties. The thermal stability have been analyzed by thermal gravimetric analysis where the dyes were stable up to 250 ̊C. The antifungal activities of the azo ligands and its metal chelates were studied against Candida albicans.

Using of TiO2/Ag2O Nanocomposite in Degradation of Acid Red 18 Dye in Photoreactor by Taguchi Experimental Design

In this paper, the sol–gel method has been use to synthesized TiO2/Ag2O nanoparticles for photocatalytic degradation of azo dye Acid Red 18 (AR18) in aqueous solution. The TiO2/Ag2O nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and Brunauer–Emmett–Teller (BET) surface area analysis. A photoreactor with capacity 0.5 L, equipped with a low mercury pressure lamp UV-C (15 W) was used. The effective factors for the degradation of dye were determined and optimized using Taguchi fractional design method with four factors having four levels for each factor. Analysis the response of each experiment was based average standard deviation values was calculated. The Taguchi results showed that pH 3, catalyst amount 45 mg/L, H2O2 concentration 25 ppm and temperature 40°C was optimum conditions for this reaction. The most influenced of each factor on the process determined using Analysis of Variance (ANOVA) method. The most significant factor in this process was pH. The interaction between catalyst amount and temperature was the most influencing interaction. So first order reaction with k = 0.0289 min–1 was observed for the photocatalytic degradation reaction.

Enhanced degradation of toxic azo dye, amaranth, in water using Oxone catalyzed by MIL-101-NH2 under visible light irradiation

The acidic azo dye, amaranth (AMR), is frequently applied on fabrics, and also extensively employed as food colorants. However, AMR is validated to be carcinogenic, and thus it should be eliminated from wastewaters preferably by advanced oxidation processes (AOPs). While Fe-based catalysts are attractive for sulfate-radical-based AOPs, few studies have been conducted to employ Fe-based catalysts for activating Oxone to degrade AMR. As Metal Organic Frameworks (MOFs) can be designed to contain Fe species and exhibit high surface areas/porosities, Fe-based MOF, MIL-101, should be promising for activating Oxone to degrade AMR. More importantly, MIL-101 can be functionalized with amino groups to form MIL-101-NH2 (MIL-N), which can exhibit visible-light-responsive photo-catalytic activities, enhancing Oxone activation and AMR degradation. The catalytic transformation of Fe species mediated by the amine functional group also leads to the formation of hydroxyl radicals to contribute to AMR degradation. MIL-N also exhibits a much lower Ea value (38.8 kJ/mol) than other reported catalysts for AMR degradation using Oxone, and MIL-N remains quite stable at a wide range of pH values. MIL-N-activated Oxone could be still able to eliminate AMR completely even in the presence of typical charged surfactants, and recyclable for multiple cycles of AMR degradation. These features validate that MIL-N can be an advantageous heterogeneous catalyst for Oxone activation to degrade AMR. The results obtained here can be quite useful for treating AMR wastewaters by sulfate-radical-based AOPs and the findings in this study offers important mechanistic insights into catalytic characteristics of MIL-N.

Effective electrochemical decolorization of azo dye on titanium suboxide cathode in bioelectrochemical system

Azo dye presents severe pollution to water environment, which needs to be treated properly to minimize environmental impact. In this study, we developed a porous titanium suboxide electrode for electrochemical reduction of azo dye (Acid Red B) in dual-chamber bioelectrochemical system (BES). The decolorization efficiency could reach 91.9% on titanium suboxide, which followed the first-order reaction kinetics with apparent rate constant of kapp = 0.339 h−1, a value 89.4% higher than that (kapp = 0.179 h−1) for carbon cloth. The cyclic voltammogram and electrochemistry impedance spectroscopy (EIS) characterization indicated higher activity and lower charge-transfer resistance of titanium suboxide. The decolourization rate was positively related to cathode potential, reaching the maximum kinetic constant of 0.456 h−1 at − 1.15 V versus standard hydrogen electrode. Lower pH was favorable for decolorization because of requirement for excessive protons for the cleavage of azo bonds, indicated by 86.4% increase in kinetic constant when shifting pH from 9.0 (0.1643 h−1) to 5.0 (0.3064 h−1). The Tafel plot illustrated a higher corrosion resistance of titanium suboxide (the corrosion current of 1.28–1.84 mA/m2) than that of carbon cloth (6.19–11.43 mA/m2) in acidic condition, suggesting higher stability due to unique oxygen-deficiency crystalline structure. This study provides the first demonstration of titanium suboxide cathode to efficiently reduce azo dye via direct electron transfer in BES, which eliminates the need for time-consuming enrichment of electroactive biofilm and avoids the development of non-electroactive microorganisms.

Biodegradation of tannery dye effluent using Fenton's reagent and bacterial consortium: A biocalorimetric investigation

The impact caused by dye effluent discharge on the environment is well known. The study explores a hybrid method of combining Fenton oxidation with biological treatment by a defined bacterial consortium for the biodegradation of an effluent containing toxic azo dye (acid blue 113). In actual treatment process, the fluctuation in toxic load and presence of other dyeing chemical inhibits the activity of the bacterial consortium. An effective pre-treatment of effluent would ensure the optimal degradation irrespective of its initial load. The pre-treatment of dye effluent with Fenton (H2O2 & Fe2+), considerably reduced the dye concentration by 40% and a maximum dye degradation of 85% (i.e., 45% by biodegradation) was achieved in shake flask. The biodegradation process was investigated in a bioreaction calorimeter (BioRc1e), the heat profile, bioenergetics data along with CER (Carbon dioxide emission rate) and OUR (Oxygen uptake rate) provided vital information for the effective commercial scale up. Enhanced degradation of up to 97% was achieved in BioRc1, the CER and OUR profile follows the power-time profile alluding that the heat generated is the resultant effect of bacterial metabolic activity. In real dye bath effluent the Fenton pre-oxidized biodegradation reaction showed a degradation efficacy of 89.5% and considerable COD reduction of 93.7%. Fluorescence-activated cell sorting (FACS) analysis revealed a better bacterial cell proliferation in pre-treated experiment and gas chromatography and mass spectrum analysis were used for prediction of metabolites. The unique combination of Fenton and the microbial consortia is a competitive technology for industrial effluent treatment processes.

Synthesis, spectroscopic characteristics, dyeing performance and TD-DFT study of quinolone based red emitting acid azo dyes

Eight novel fluorescent heterocyclic acid dyes were prepared by diazotizing various sulphonic acid based amines and coupling with 4-hyrdoxyl-1-methyl-2(1H)-quinolone. Structures of synthesized dyes were well supported by 1H NMR, 13C NMR, Mass spectroscopy, FTIR and elemental analysis. The effect of high molecular weight and heterocyclic moiety were observed to have significant influence on photophysical properties, color values and fastness performances of the dyes. Substitutions on ortho to azo linkage played an important role in enhancing light and wash fastness properties of the dyes. Dyeing characteristics of all the dyes were evaluated on wool, nylon and silk substrates. Evaluation of UV-protection factor (UPF) of the dyed fabrics suggested that these dyes can be used to make UV-protective fabric. DFT calculations were employed to calculate the stability of tautomeric forms of the dyes and find out electrophilicity index of prepared dyes. TD-DFT used to study structural effect on photophysical properties.

Ultra-morphology of the scale as an indicator of the stress of Acid Black-1 (AB-1, CI: 20470) and zinc (Zn).

High contents of azo dyes and heavy metals enter surface waters with the wastewater from dying and dye-manufacturing industries and pose serious threat to fish. In the present study, changes in the ultra-morphological features of the scale have been evaluated as indicators of the stress of lethal and sublethal concentrations of an azo dye Acid Black-1 (AB-1, CI 20470), zinc (Zn), and their mixture AB-1 + Zn to Labeo rohita. Fish were exposed for 96h to lethal concentration (LC) causing 0-70% mortality, i.e., LC0, LC20, LC50, and LC70 of AB-1 (4, 6, 8, and 10mg/L respectively) and Zn (25, 50, 55, and 60mg/L respectively) and LC0, LC50, and LC70 of AB-1 + Zn (2 + 15, 2 + 20, and 2 + 25mg/L respectively). Subchronic exposures of 150days were given to 1/12, 1/6, and 1/3 of 96h LC50 values of AB-1, Zn, and AB-1 + Zn. After each exposure, the fish were kept for a recovery period of 90days. Breakage of circuli, erosion and breakage of lepidonts, uprooting of tubercles, and disappearance of intercircular teeth were observed in all the fish, after 96h exposure to AB-1, Zn, and AB-1 + Zn. However, damage to focus and holes were common on the scales of Zn-exposed fish. The mixture AB-1 + Zn was more toxic than either of the two as loss of circuli, lepidonts, and intercircular teeth, and sloughing of surface were observed in the scales after 96h exposure to 2 + 25mg/L. Damage at this concentration was more than the damage at 8/10mg/L AB-1 and 55/60mg/L Zn. After 150days of exposure, damage due to sublethal concentrations was more than the damage due to allthe concentrations of 96h exposure. Irregular and sloughed circuli were common at 2 + 1.79 and 2 + 3.59mg/L AB-1 + Zn. Cracks all over the surface (2 + 7.18mg/L), calcium projections (2 + 3.59 and 2 + 7.18mg/L), and holes (2 + 7.18mg/L) hint towards synergistic toxicity of the mixture. It seems that the present dye and metal formed complexes with collagen and osteoblastic cells of the scale that caused an increase in damage during the post-exposure period. Scales of 2 + 7.18mg/L AB-1 + Zn exposed fish were completely devoid of the normal architectural pattern on the 90th day of the recovery period. Changes in the ultra-morphology of scales at LC0 (0% mortality) and sublethal concentrations show that these are early indicators of the stress of minute quantities of dyes and metals in water. This is a first report on the cumulative toxicity of the two most abundant components of textile industry effluents.

Statistical evaluation of dye desorption – mixed two- and three-level design and kinetic modeling

Biosorption has been shown in the literature to be effective in the removal of dye from aqueous solution. To be fully useful, a desorption process is necessary, which has a direct impact on the process costs. The aim of this work was to evaluate the desorption of the azo dye Acid Yellow 23 adsorbed in a biosorbent obtained from Bombyx mori cocoons. Temperature and pH media were evaluated through a mixed two- and three-level design, using NaOH as desorbing agent. Kinetic desorption was also obtained at the optimized condition. The statistical evaluation of the experimental design showed that the pH has almost two times more influence on the dye desorption than the temperature, with only the linear parameters being statistically significant. Among four kinetic desorption models adjusted to the experimental data, the proposed n-order model was statistically determined as the best representation of the experimental data.