Increase In Initial Dye Concentration Research Articles

Improved biodegradation of Congored by using Bacillus sp.

The biodegradation of Congored, a toxic azo dye, was studied by using a hybrid technique involving sonolysis as pretreatment followed by biological treatment. The experiments were carried out with and without pretreatment using dye solution as a sole source of nutrition with an isolated and acclimatized strain of Bacillus sp. obtained from tannery industry effluent. The pretreatment time was varied as 30, 60, 90, 120, 150 and 180min and then the pretreated dye solution was subjected to biological treatment. The effectiveness of pretreatment was compared with the results of biological degradation of non pretreated Congored and the results showed that the pretreatment improved the efficiency of the biodegradation of Congored. During the biological degradation, the increase in initial dye concentration decreased the decolorization rate and at high concentrations (1500 and 2000mg/l), the inhibition was observed. The optimum pH and temperature were determined to be 7.0 and 37°C, respectively. The data obtained through biodegradation experiments were fitted with five different kinetic models and the results were analyzed.

Removal of Reactive Orange 4 from Aqueous Solution by Waste Eichhornia crassipes Biomass

Biosorption of Reactive Orange 4 dye, from an aqueous solution was evaluated by Eichhornia crassipes in a batch system. The influence of pH (1-6), temperature (20-30°C) and initial dye concentration (20 to 120 mg/L) on the biosorption process was studied. Maximum biosorption was observed at initial pH of 2.0, temperature of 30°C and at the initial dye concentration of 120 mg/L. Batch biosorption kinetics was studied with different initial dye concentrations and rate of biosorption was determined using the pseudo first and pseudo second order rate equations. From the result it was observed that pseudo second order rate expression fit the experimental data well for Reactive Orange 4 when compared to pseudo first order kinetic model. The intra particle diffusion coefficient (Ki) and effective diffusion coefficient (Di) values obtained for the sorption of Reactive Orange 4 using E. crassipes was found to be increased with increase in initial dye concentrations.

Chitosan intercalated montmorillonite: Preparation, characterization and cationic dye adsorption

Chitosan intercalated montmorillonite (Chi-MMT) was prepared by dispersing sodium montmorillonite (Na +-MMT) into chitosan solution at 60 °C for 24 h. The Chi-MMT was characterized by XRD, XRF and FT-IR. The intercalation was accomplished via the ion-exchange of Na + ions with –NH 3 + of chitosan, resulting in the expansion of d 001 from 1.42 nm of Na +-MMT to 2.21 nm of Chi-MMT. The chitosan content in the Chi-MMT measured by TGA was about 17 mass%. The adsorption capacity of Chi-MMT was investigated in comparison with the starting Na +-MMT and chitosan using three different cationic dyes, i.e. basic blue 9 (BB9), basic blue 66 (BB66) and basic yellow 1 (BY1). The Chi-MMT showed the highest adsorption capacity in the range of 46–49 mg/g when the initial dye concentration was 500 mg/L, being equivalent to 92–99 wt.% of dye removal. The adsorption capacities of Chi-MMT for all basic dyes increased with an increase of initial dye concentration. An increase of adsorption capability of Chi-MMT was attributed to the existence of intercalate-chitosan. It could enlarge the pore structure of Chi-MMT, facilitating the penetration of macromolecular dyes, and also electrostatically interact with the applied dyes. These results indicated the competency of Chi-MMT adsorbent for basic dye adsorption.

REMOVAL OF ACID RED 398 DYE FROM AQUEOUS SOLUTIONS BY COAGULATION/FLOCCULATION PROCESS

The removal of Acid Red 398 (AR398) dye from dye-containing solution using coagulation/flocculation process with polyaluminum chloride (PAC) and Alum was investigated. The effect of different parameters involving pH, dosage of coagulant, initial dye concentration, and bentonite as a natural coagulant aid was examined. According to the obtained results, the optimum pH, at which the maximum removal occurred, was about 4 and 5 for PAC and Alum, respectively. However, PAC performed efficient in a broader pH range. In the case of PAC, the best removal efficiency was about 80% for the dosage of 100-120 mg/l, while, it was about 60% for 140-160 mg/l of Alum. With the increase of initial dye concentration in the range of 25-250 mg/l, the removal efficiency for both coagulants increased at first (from 25-100 mg/L) and then declined. Bentonite, as a coagulant aid, slightly enhanced the removal efficiency. By adding 20 mg/l of bentonite, the efficiency increased by 15% and 9% for Alum and PAC, respectively.

Decolorization of C.I. Reactive Yellow 84 in Aqueous Solution by Electrocoagulation Enhanced with Ozone: Influence of Operating Conditions

We studied the use of a combination of electrocoagulation (EC) and ozonation for the decolorization of the azo dye, C.I. Reactive Yellow 84 (RY84). The effects of initial dye concentration, initial pH, current density, salt concentration, ozone flow rate, temperature and interelectrode distance on the decolorization of RY84 were investigated. The results showed that a synergistic effect was achieved by combining EC with ozone for the decolorization of RY84. Under the experimental conditions, the decolorization rate increased with an increase in current density. However, the decolorization rate decreased with an increase in initial dye concentration and salt concentration. The interelectrode distance did not substantially affect the decolorization rate. Other operating parameters such as initial pH, ozone flow rate and temperature had both positive and negative effects. Over 97% of the color decay was achieved within 10 min reaction time under reasonable experimental conditions. When the decolorization of RY84 was complete, the efficiency of removal of total organic carbon (TOC) was more than 85%.

Catalytic ozonation with non-polar bonded alumina phases for treatment of aqueous dye solutions in a semi-batch reactor

Abstract Semi-batch experiments were conducted to investigate the effects of catalyst type, pH, initial dye concentration and production rate of ozone on the catalytic ozonation of the dyes, namely Acid Red-151 (AR-151) and Remazol Brilliant Blue R (RBBR). The used catalysts were alumina, 25% (w/w) perfluorooctyl alumina (PFOA), 50% (w/w) PFOA and 100% (w/w) PFOA. The results showed that the overall percent dye removal after 30 min of the reaction was not affected significantly by the catalyst type. However, highest COD reduction was achieved by ozonation with alumina for AR-151, and 100% PFOA for RBBR at pH 13. The behavior of COD reduction with the increasing amount of perfluorooctanoic (PFO) acid amount can be explained by the enhancement of catalytic activity of PFOA with alkyl chains. For both of the dyes, the highest dye and COD removals were reached at pH 13. The overall dye reduction after 30 min of ozonation was almost independent of the initial dye concentration at relatively low values while at the higher concentrations, it changed with the initial dye concentration for both of the dyes. Similarly, COD reduction changed on a limited scale with the increasing initial dye concentration from 100 mg/L to 200 mg/L; however, an increase of initial dye concentration to 400 mg/L decreased the COD reduction significantly. All the studied production rates of ozone were sufficient to provide almost 100% dye removal in 30 min, whereas the COD removal percentage was increased gradually by the increasing ozone input to the reactor. The reaction kinetics for the ozonation of each dye with and without catalyst was investigated and discussed in the paper.

Case study of the sonochemical decolouration of textile azo dye Reactive Black 5

The decolouration and mineralization of reactive dye C.I. Reactive Black 5, a well-known representative of non-biodegradable azo dyes, by means of ultrasonic irradiation at 20, 279 and 817 kHz has been investigated with emphasis on the effect of various parameters on decolouration and degradation efficiency. Characterization of the used ultrasound systems was performed using calorimetric measurements and oxidative species monitoring using Fricke and iodine dosimeter. Experiments were carried out with low frequency probe type, and a high-frequency plate type transducer at 50, 100 and 150 W of acoustic power and within the 5–300 mg/L initial dye concentration range. Decolouration, as well as radical production, increased with increasing frequency, acoustic power, and irradiation time. Any increase in initial dye concentration results in decreased decolouration rates. Sonochemical decolouration was substantially depressed by the addition of 2-methyl-2-propanol as a radical scavenger, which suggests radical-induced reactions in the solution. Acute toxicity to marine bacteria Vibrio fischeri was tested before and after ultrasound irradiation. Under the conditions employed in this study, no toxic compounds were detected after 6 h of irradiation. Mineralization of the dye was followed by TOC measurements. Relatively low degradation efficiency (50% after 6 h of treatment) indicates that ultrasound is rather inefficient in overall degradation, when used alone.

Combined effects of molasses sucrose and reactive dye on the growth and dye bioaccumulation properties of Candida tropicalis

The combined effects of molasses sucrose and Remazol Blue or Remazol Black B reactive dye on the growth and dye bioaccumulation properties of adapted Candida tropicalis yeast was investigated in a batch system as a function of initial dye and sucrose concentrations. At a constant sucrose concentration, although the increase in initial dye concentration up to approximately 1000 mg l −1 increased the dye bioaccumulation capacity of yeast for both the dyes, all dye concentrations tested inhibited the growth of C. tropicalis. The cell and bioaccumulated dye concentrations and uptake yields increased with increasing sucrose concentration up to 15 g l −1 at a constant dye concentration for each of the dyes. In 10 g l −1 sucrose and about 1000 mg l −1 dye containing medium the dye adapted yeast was capable of accumulating of Remazol Black B and Remazol Blue dyes with a maximum uptake capacity of 167.5 and 163.3 mg dye per g of dry cells, respectively. The inhibition effect of dye anions on the specific growth rate of yeast was expressed by the non-competitive inhibition model (assuming the dye anions as the toxic inhibitory component) and model parameters were determined by graphical method.

Decolourisation of Reactive Orange 4 by Fenton and photo-Fenton oxidation technology

The photochemical decolourisation of chlorotriazine reactive azo dye Reactive Orange 4 (RO4) has been carried out by Fenton and photo-Fenton processes. The effects of solution pH, applied H 2O 2, Fe 2+ dose, UV light intensity have been studied. The increase of initial dye concentration decrease the removal rate. Under optimum conditions the photo-Fenton process is found to be more efficient than Fenton process. About 2% of colour resurgens was observed at the end of the reaction.

Photochemical oxidation of reactive azo dye with UV–H 2O 2 process

The photooxidation of a chlorotriazine reactive azo dye Reactive Orange 4 has been carried out in the presence of H 2O 2 using UV-A light. The effects of reaction pH, applied H 2O 2 dose, UV light power have been studied. These parameters strongly influence the decolourisation and degradation. The increase of initial dye concentration decreases the removal rate. The kinetics of decolourisation and degradation follow pseudo-first order. The solar–H 2O 2 process is also able to oxidise the dye and its efficiency is comparable with UV–H 2O 2. The influence of dye assisting chemicals such as NaOH, NaCl and Na 2CO 3 on photodecolourisation has been investigated. Addition of these chemicals inhibit the removal rate. The optimum operating conditions of the method are reported.

Solar Light Induced Degradation of Reactive Dye Using Photocatalysis

Outdoors experiment with natural solar light instead of using artificial UV light was also conducted to investigate alternative energy source applicability on organics degradation. The results of this study were as follows. Degradation of the reactive dye, Red 120, with TiO2/solar light was enhanced by augmentation in TiO2 loading, and UV light intensity but was inhibited by increase in initial dye concentration. With both solar light illumination and TiO2 present, reactive dye was more effectively eliminated than with either solar light or TiO2 alone. Photocatalytic removal efficiency of reactive dye increased with increasing TiO2 dosage. However, over 1.5 gL−1 of TiO2 dosage, the efficiency reached a plateau. The degradation rate of reactive dye, Red 120, was strongly dependent on initial dye concentration, and all the experimental data were fit to the first-order rate equation. Photocatalytic degradation of reactive dye increased linearly with increasing UV light intensity. It is found that the presence of thick clouds in the sky markedly increased the time required for degradation of reactive dye. On the basis of these experimental observations, the photo-oxidation degradation of reactive dye using TiO2 under solar light irradiation can be feasible application of the advanced oxidation process.

Removal of Reactive Dye from Wastewater by Adsorption Using ECH Cross-Linked Chitosan Beads as Medium

The feasibility of the removal of reactive dye from wastewater using a novel adsorbent, ECH cross-linked chitosan beads, as medium was examined. The effect of the pH and the initial concentration of the dye (RR222) solution on the adsorption capacity of the ECH cross-linked chitosan beads were also investigated. It was found that the initial dye concentration and the pH of the solution significantly affected the adsorption capacity. An increase in initial dye concentration results in the increase of adsorption capacity while an acidic pH was found to be favorable for the adsorption of dye. It was also found that the equilibrium adsorption of RR222 could be adequately described by using the Langmuir model (r 2 ≥ 0.999). Moreover, results showed that the adsorption rate of RR222 onto ECH cross-linked chitosan beads could be described by using the second-order kinetic model, suggesting that chemical sorption instead of mass transfer was the rate-limiting step for the adsorption process. The maximum monolayer adsorption capacity obtained from the Langmuir model was extremely high as compared to the data reported in literature; 2252 g/kg at 30°C with a pH of 3.0. Therefore, ECH cross-linked chitosan beads could be a feasible medium for the removal of reactive dye from wastewater and potentially an alternative for the decolorization of wastewater.

Equilibrium and kinetic modeling of adsorption of reactive dye on cross-linked chitosan beads

The adsorption of reactive dye (Reactive Red 189) from aqueous solutions on cross-linked chitosan beads was studied in a batch system. The equilibrium isotherms at different particle sizes (2.3–2.5, 2.5–2.7 and 3.5–3.8 mm) and the kinetics of adsorption with respect to the initial dye concentration (4320, 5760 and 7286 g/m 3), temperature (30, 40 and 50 °C), pH (1.0, 3.0, 6.0 and 9.0), and cross-linking ratio (cross-linking agent/chitosan weight ratio: 0.2, 0.5, 0.7 and 1.0) were investigated. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherm constants. Equilibrium data fitted very well to the Langmuir model in the entire saturation concentration range (0–1800 g/m 3). The maximum monolayer adsorption capacities obtained from the Langmuir model are very large, which are 1936, 1686and 1642 g/kg for small, mediumand large particle sizes, respectively, at pH 3.0, 30 °C, and the cross-linking ratio of 0.2. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicates that the chemical sorption is the rate-limiting step, instead of mass transfer. The initial dye concentration and the solution pH both significantly affect the adsorption capacity, but the temperature and the cross-linking ratio are relatively minor factors. An increase in initial dye concentration results in the increase of adsorption capacity, which also increases with decreasing pH. The activation energy is 43.0 kJ/mol for the adsorption of the dye on the cross-linked chitosan beads at pH 3.0 and initial dye concentration 3768 g/m 3.

Degradation of azo dye Procion Red MX-5B by photocatalytic oxidation

The photocatalytic oxidation (PCO) of a monoazo dye Procion Red MX-5B under various physico-chemical conditions was investigated. Degradation of the dye by PCO was enhanced by augmentation in UV intensity, titanium dioxide and hydrogen peroxide concentrations but was inhibited by increase in initial dye concentration. The PCO process was affected by pH in a peculiar way. In the presence of 100 mg/l of TiO 2 and the absence of H 2O 2, the highest reaction rate was observed when the initial pH was 10. With 500 mg/l of TiO 2 and 10 mM of H 2O 2, the reaction was the fastest at initial pH of 3–5. The optimal conditions for the degradation of the dye, at an UV intensity of 17 mW/ cm 2 , were determined to be: TiO 2 concentration, 500 mg/l; initial H 2O 2 concentration, 10 mM; initial pH, 5.0. Monitoring of TOC loss showed that the dye was mineralized by 90% within 80 min under these conditions. Nevertheless, the persistence of a low level of TOC indicated that mineralization was not complete and dead-end product(s) which was (were) resistant to PCO might have accumulated.