Increase In Dye Concentration Research Articles

The Dyeing of Cotton Fabric with Natural Dye from Buddlejae Flos

ABSTRACT Buddlejae Flos is a promising natural dye for cotton fabric. Buddlejae Flos extraction and AlK(SO4)2.12H2O were dissolved in 70% ethanol and the cotton fabric was dyed with this solution. And its dyeing kinetics and isotherm were evaluated. The results showed that dye absorption increased with the increase in dye concentration and dyeing temperature. The absorption kinetics of Buddlejae Flos dye onto cotton fabric were best described by the pseudo-second-order kinetics model (R2 > 0.99) and absorption isotherm fitted the Freundlich model better. Optimal dyeing conditions were selected through orthogonal trial: 1:30 bath ratio, 80°C dyeing temperature, 100 min dyeing time, and 1.25 g/L mordant. The Buddlejae Flos dyed cotton fabric presented good antioxidant performance. The wash fastness and rubbing fastness of the dyed cotton fabric are both above 4 grades. It is concluded that Buddlejae Flos has a good potential to act as a source of natural colorant for cotton dyeing in the ethanol-water system.

Silver nanoparticles for enhanced dye degradation

Dye wastewater discharged after improper treatment is very harmful for environment and living creatures. As per mandate, the dye wastewater should be treated well in order to prevent any negative effects after discharge. Although there are various methods which are in use, however most of these methods have some or the other associated disadvantages i.e., high cost, generation of secondary pollutants, low efficiency, complexity etc. The objective of this study is to identify the dye degradation (orange and blue dye-individually/mixture) potential of chemically synthesized silver nanoparticles (CH-AgNPs) along with NaBH4. Literature studies highlighted the efficacy of AgNPs for individual dye degradation, however it is very important to study the degradation potential of nanoparticles in presence of dye mixture (to mimic the natural wastewater condition). In the present study, the rapid synthesis of silver nanoparticles (CH-AgNPs) was obtained by using trisodium citrate solution. The developed CH-AgNPs were examined for UV–vis Spectrophotometry (maxima-422 nm), Zeta Potential (−6.70 ​mV), and Transmission Electron Microscopy (spherical shape with size range of 8–40 ​nm), highlighting the nano-size and stability of synthesized CH-AgNPs. For catalytic activity, CH-AgNPs and NaBH4 were tested for dye degradation potential for Orange and Blue dyes individually and in mixture (orange ​+ ​blue dye). It was observed that with increase in dye concentration from 50 ​ppm to 200 ​ppm, NaBH4 showed 28% and 25% removal for blue and orange dyes, respectively. However, when CH-AgNPs ​+ ​NaBH4 was used, up to 100% degradation was obtained from blue dye, however the degradation of orange dye has shown 97.4% degradation. Further, as the wastewater contains multiple dyes, therefore in dye mixture studies (orange ​+ ​blue dye- 50 ​ppm), 100% degradation was achieved with NaBH4+CH-AgNPs in just 5 ​min, highlighting the efficient catalytic ability of NaBH4+AgNPs. The results clearly highlighted the potential of CH-AgNPs in enhancing the dye degradation of orange and blue dyes-individually and in mixture, therefore the present study is relevant for further research to identify the best dye degradation agents, especially in presence of dyes mixture.

Equilibrium and Kinetic Studies of Liquid Phase Adsorption of Methylene Blue Onto Phosphoric Acid Modified Bambaranut Shell

Abstract In view of the global need to curb the effect of contaminants in waste water on our environment, the adsorption potentials of modified carbon from bambaranut (Vigna subterranean) shell was investigated for its efficiency in the removal of methylene blue from waste water. The adsorbent morphology and surface chemistry were established by Brunauer-Emmett-Teller (BET) determination and Scanning Electron Microscopy (SEM), as well as other standard laboratory procedures. The prepared material was used for the uptake of MB from aqueous solution in a batch process, using UV spectrophotometer Model 752 at 620nm to analyze for the residual dye concentration. The effect of operational parameters such as contact time, adsorbent dosage, initial dye concentration and pH were analyzed to determine the factors controlling the rate of adsorption. Results from the study showed that the active carbon prepared was a porous material, with surface area of 193 m2/g, average pore size of about 10.98nm, and pore volume of 0.530cm3/g. With increase in initial dye concentration from 15mg/l to 75mg/l, a decrease in percent adsorption from 95.4% to 72.19% was observed. Increase in adsorbent dosage (from 0.1g to 0.5g), contact time (from 5 min to 40 min) and pH from 2 to 10 resulted in increase in percent adsorption from 84.03% to 98.83%, 54.24% to 84% and 48.17% to 84.03% respectively. About 98.83% removal of MB dye was achieved after 20 min, at pH of 6, temperature of 27±2oC, 0.5g weight of adsorbent and initial concentration of 60mg/l of 50ml MB dye solution. Langmuir isotherm best fits the equilibrium adsorption data with R2 = 0.996; the adsorption intensity obtained from Freundlich model (n>1) and the energy of adsorption obtained from the D-R model (< 8kJ/mol) suggested that physisorption dominates the adsorption of methylene blue onto the prepared activated carbon. Adsorption kinetic data was best described using Pseudo second order kinetic model (R2 = 0.996), giving equilibrium rate constant (k2) of 7690g mg-1 min-1. The characteristic results showed that bambaranut shell can be employed as an alternative to commercial adsorbents in the removal of methylene blue dye from aqueous solutions and waste water.

DYEING OF WOOLEN FIBERS WITH RHODODENDRON ARBOREUM FLOWERS USING SYMPLOCOS RACEMOSA LEAVES AS MORDANT UNDER OPTIMUM CONDITIONS

Out of the multiple applications of the diverse natural products of Uttarakhand dyeing of fabrics with the help of various plant parts has always stood out. In the present investigation, an attempt has been made to extract natural dye from Rhododendron arboretum flowers and to optimize conditions of concentration and time for dyeing woolen sample from the extracted dye. The results showed that the colour strength (% Absorbance) increases with the increase in concentration of dye up to 0.03 g/ml concentration. Also, dyeing procedure has been optimized by using Symplocos racemosa leaves as mordant. The best results were obtained using simultaneous mordanting method with Symplocos racemosa leaves at 0.03 g/ml concentration.

Development of Sunlight-Driven Reduced Graphene Oxide (rGO)/CeO₂-CuO Nanofibrous Photocatalyst for Efficient Removal of Organic Dyes.

A hybrid nanofibrous membrane photocatalysts was developed through electrospinningcarbonization method. In this work, the hybrid membrane with p-n hetero-structure consisting of CeO₂ and CuO metal-oxide nanoparticles was prepared by a hierarchical and facile approach through electrospun technique and stabilized by hydrothermal process. The obtained heterogeneous photocatalyst membrane was studied for its catalytic properties by performing several experiments using test solutions of anionic Congo red (CR) and cationic methylene blue (MB) dyes, respectively. The as-prepared Graphene-CeO₂/CuO intercalated polyacrylonitrile nanofibrous (GCPNs) membrane is characterized by using various analytical techniques and its photocatalytic degradation properties was studied by conducting batch studies and validated using the kinetics models. Furthermore, the functional group transformation, electronic transition state, binding energy values and chemical oxidation state of the GCPNs membrane before and after degradation was investigated by spectroscopic studies. The optical properties of the GCPNs membrane was further analysed by UV-VIS diffuse reflectance spectroscopy (DRS). Also, the enhanced photo-degradation behaviour of the p-n hetero-structure due to the suppression of the recombination rate of the photogenerated electron-hole pairs was confirmed by photoluminescence studies (PL). These investigations implied that the developed photocatalyst GCPN membrane follows the pseudo first-order kinetics having higher reaction rate constant. Comprehensively, the GCPN has varying dye removal capacity of 90-98% for Congo red and 30-90% for Methylene blue in which the photocatalytic degradation capacity increases with increase in dye concentration and time. The reusability studies supported the sustainability and durability of the photocatalytic membrane for longer lifetime and practical value. Henceforth, nanotechnology-based cutting-edge technology offers novel hybrid nanomaterials having excellent properties that are pre-requisite for the development of sunlight mediated nano-photocatalytic reactors in the commercial applications.

Study Interionic Attraction of anionic dyes by Electrolytic Conductivity Measurement

Measurements of conductivity in aqueous solution are recommended for studying the behavior of some dyes. The conductivity of two azo dyes C.I. Acid Red 151 (AR 151) and C.I. Mordant green 17 (MG17) have been studied. The ionization degree, α and Van,t Hoff’s factor ,i, were calculated; their values decrease with increasing dye concentration and increase with increasing temperature. The mobility, µ, the activation energy, E, were also calculated. The findings indicate that interionic attractions and connections are present. Dyes ions tend to self-associate. Since these textile dyes were applied from aqueous systems, it is important to understand the association of dyes. The molecular aggregation of two sulphonated dyes studied by measuring the electrolytic conductivity in aqueous solutions as a function of dye concentration and temperature. Aggregation number, aggregation constant and shape of aggregate were calculated. As expected the aggregation number decreases with increasing temperature, and that tends to J-aggregation which enhance the devices performance such as xerography, sensors in presence of different additives.

Acute toxicity of textile dye Methylene blue on growth and metabolism of selected freshwater microalgae

Microalgae are ecologically important species in aquatic ecosystems due to their role as primary producers. The inhibition of growth of microalgae due to dye pollution results in an upheaval in the trophic transfer of nutrients and energy in aquatic ecosystems. Therefore, this investigation aimed to evaluate the toxicity of a textile dye Methylene blue (MB) on two microalgae viz. Chlorella vulgaris and Spirulina platensis. An exposure of the unialgal populations of both the microalgae towards graded concentrations of the dye showed a concentration-dependent decrease in specific growth rate, pigment and protein content. In the toxicity study of 24 –96-h, following the OECD guidelines 201, the EC50 values of C. vulgaris and S. platensis ranged from 61.81 to 5.43 mg/L and 5.83 to 1.08 mg/L respectively revealing that S. platensis exhibited a higher level of susceptibility towards the dye as compared to C. vulgaris and the latter is more tolerant to the dye toxicity even at higher concentrations. The findings indicate that the response to dye is a species-specific phenomenon. Given the differences in the cell structure and enzymatic pathways in Spirulina platensis (a prokaryote) and Chlorella vulgaris (an eukaryote), the tolerance levels can differ. After 96-h exposure of C. vulgaris to MB (100 mg/L), the chlorophyll-a, b and carotenoid content were reduced 2.5, 5.96 and 3.57 times in comparison to control whereas in S. platensis exposure to MB (10 mg/L), the chlorophyll-a and carotenoid content were reduced 3.59 and 5.08 times in comparison to control. After 96-h exposure of C. vulgaris and S. platensis to the dye (20 mg/L), the protein content was found to be 4.34 and 2.75 times lower than the control. The protein content has decreased in accordance with the increase in dye concentration.

The study of direct dye sorption on flax fibers during dyeing

This article presents the study of direct dye sorption onto the flax fiber during the dyeing process in the presence of an inorganic electrolyte. The previously prepared linen fabric was subjected to dyeing by a standard process, varying in concentration and time of dyeing. The results are satisfactory considering that they reveal the character of the direct dye sorption for fibers, as well as the capacity and energy adsorption, on the basis of which the process of dyeing can be optimized. The increase of dye concentration in the solution during dyeing decreases, and longer time of dyeing increases the degree of exhaustion. The adsorbed amount of adsorbate on the adsorbent rises during the increase of initial concentration and dyeing time. Langmuir, Freundlich, Temkin and Flory?Huggins models can be used to describe adsorption of a direct dye onto the linen fiber, having in mind the advantage of Flory?Huggins model because of its characteristics in the description of the sorption and maximum values of the coefficient of determination as well.

Immobilization of laccase from Trametes hirsuta EDN 082 in light expanded clay aggregate for decolorization of Remazol Brilliant Blue R dye

Immobilization is a method to enhance the activity, the stability and the reusability of enzymes. This study aims to evaluate the capacity of laccase from Trametes hirsuta EDN 082 immobilized in the activated Light Expanded Clay Aggregate (LECA) for dye decolorization. The effects of enzyme loading, the dosage of immobilized laccase-LECA, and the enzyme reusability were investigated. The results showed that the immobilization yield laccase-LECA was 78.78%. One gram of immobilized laccase-LECA with 4.65 U/g of enzyme loading decolorized 99.29% Remazol Brilliant Blue R (RBBR) dye for 3 h. The immobilized laccase-LECA reusability was up to 6 number cycles with 79.67% of the remaining decolorization rate. Immobilized laccase also shifted wide pH and temperature values compare to free enzyme. The kinetic study showed that the specific decolorization rate increases with an increase in initial dye concentration up to 700 and 900 mg/L for laccase-LECA and free laccase, respectively.

Kinetic and thermodynamic studies for evaluation of adsorption capacity of fungal dead biomass for direct dye

Abstract This study focuses on evaluation of degradation aptitude of white rot fungus (Coriolus versicolor) against Indosol Turquoise FBL dye. The outcome of numerous parameters including pH, temperature, carbon sources, nitrogen sources, C/N ratio and effect of dye concentration were studied. Maximum decolorization (99.896%) of Indosol Turquoise FBL was obtained by C. versicolor under optimized conditions. After three days, the maximum dye degradation (98%) was observed at pH 4 and 30 °C. Six carbon sources fructose, glucose, maltose, sucrose, rice bran and wheat bran were used and 96.66% degradation was observed by maltose at its optimum growth concentration (0.1 g/100 mL). Various nitrogen sources were employed for decolorization but ammonium nitrate decolorized dye up to 98.05%. The activity of three different enzymes laccase, Lignin peroxidase (LiP) and Manganese peroxidase (MnP) were calculated. The dead biomass of White rot fungus (WRF) was used for biosorption experiments. Maximum q (36 mg/g) was obtained at pH 2, at 30 °C using 0.05 g biosorbent. An increase in the q value was observed with increase in dye concentration. Freundlich adsorption isotherm and pseudo second order kinetics were followed by the data. It can be concluded that C. versicolor could be an efficient source for degradation of dyes from industrial effluents.

Effect of Erioglaucine dye dopant on the structural, optical, mechanical, electrical and nonlinear properties of ammonium dihydrogen phosphate single crystal

Abstract The structural, optical, mechanical, electrical and nonlinear properties of standard Ammonium Dihydrogen Phosphate (NH4H2PO4, ADP) single crystals incorporating organic Erioglaucine dye dopant are presented. The effect of Erioglaucine dye dopant at varied concentration on these properties has been investigated through measurement of powder X-Ray Diffraction (XRD), UV–Vis and photoluminescence spectroscopy, Vickers microhardness, light dependent I–V measurements and Second Harmonic Generation studies. These measurements reveal that doping with increasing dye concentration of Erioglaucine leads to change in properties of the ADP single crystals, making them suitable for optoelectronic applications. The Erioglaucine doped ADP single crystals were grown using solvent evaporation technique at room temperature. Optical properties like absorbance and emission of these crystals are determined using UV–vis and photoluminescence spectroscopy, respectively. Optical bandgap and photoluminescence of the crystals are found to increase with dye doping, indicating their suitability in photonic applications. The mechanical properties of the crystals are determined using Vickers microhardness measurement technique. Light dependent I–V measurements exhibit negative photoconductivity behavior of the ADP crystals. However, the current through the crystals is observed to increase with increase in doping concentration of the Erioglaucine dye. Second Harmonic Generation studies show enhancement in nonlinearity for doped crystals. Our experiments indicate gradual variance in the crystallinity, emission, hardness, conductivity and nonlinearity of the sample with change in dye concentration.

Heat-activated potassium persulfate treatment of Sudan Black B dye: Degradation kinetic and thermodynamic studies

Water-soluble dyes are common persistent organic pollutants present in textile wastewater, which are associated with environmental pollution and health hazards. The conventional effluent treatment methods are not efficient to remove these dyes from textile wastewater. Heat activated persulfate based wastewater treatment is a promising advanced oxidation process (AOP) for the treatment of textile wastewater. Therefore, the main objective of the present work was to study the degradation of Sudan Black B (SBB) dye in aqueous solution by varying activation temperature (40–60 °C), KPS dosage (250–750 ppm), and initial dye concentration (20–50 ppm). The dye degradation was found in a range of 35%−100% for varied experimental conditions. Removal percentages were improved by the increase of temperature, time, and persulfate concentration but decreased with the increase of initial dye concentration. The kinetic study indicated that the degradation of SBB dye using KPS followed first order model with rate constants varied in a range of 0.15 × 10-2 − 40.5 × 10-2 min-1. Standard reaction enthalpies (ΔH˚), standard Gibbs free energies (ΔG˚), activation energies (Ea), standard entropies (ΔS˚) were found in a range of 190 − 505 kJ.mole-1, -33.0 − 0.6 kJ, 73 − 222 kJ.mole-1, 0.6–1.6 kJ/K for different sets of experimental conditions, respectively. Degradation reactions of SBB dye were endothermic (ΔH˚ +ve); non-spontaneous (ΔG˚ +ve) at 40 °C, but spontaneous (ΔG˚ −ve) at other temperatures (50 °C and 60 °C). Therefore, it can be predicted that heat-activated persulfate is an efficient method to achieve faster degradation of dye in the treatment of industrial wastewaters containing SBB dye.

Chemical stimulus-responsive tricyanopyrroline-based ICT chromophore as a potential environment-sensitive probe

Tricyanopyrroline (TCP)-based intermolecular charge transfer (ICT) dye 1 was synthesized by incorporating phenothiazine and diphenylamine groups, and it was shown to absorb near-infrared light at 734 nm with a molar extinction coefficient (εmax) of 1.67 × 104 M−1 cm−1 in toluene, resulting in a broad absorption band ranging from 600 to 900 nm. By combining the properties of the amide (–NHCO–) group of the TCP acceptor with its ICT character, the photophysical properties of 1 were found to be environment-sensitive. Moreover, its absorption profile was significantly dependent on the nature of the solvent; for instance, in CH2Cl2, a λmax value of 781 nm was observed with an optical absorption edge (λonset) of 1018 nm, whereas the use of DMSO instead of CH2Cl2 led to a significant hypsochromic shift to a λmax value of 532 nm. Nonetheless, an increase in dye concentration caused a significant bathochromic shift in the absorption band, which was ascribable to the self-dimerization of the dye (Kd = (1.26 ± 0.84) × 104 M−1) through intermolecular hydrogen bonding between the amide moieties. The amide unit also served as a binding site for anions to generate a selective colorimetric response in the presence of AcO− and F−. Notably, 1 offers the potential to detect F− quantitatively in commercially available toothpaste. The chemical stimuli-sensitivity of the absorption properties was elucidated through several analytical techniques and theoretical calculations.

Novel homogeneous catalyst assisted sonocatalytic degradation of dye Direct Blue 71

Industrial effluents, particularly from dye industry, is one of the major causes of serious concern as it contaminates the environmental water resources and affect human health. Treatment of such contaminants is a challenging area of interest to researchers. In this context, here, we have explored degradation and mineralization of Direct Blue (DB71) dye in aqueous solution by means of ultrasound irradiation at a frequency of 25 kHz and its combination with a novel homogenous sonocatalyst is investigated. The following experiments have been conducted to achieve complete degradation of the dye molecule. In-situ generation of the radicals under ultrasonic irradiation is measured by EPR technique. The effects of various operational parameters such as the effects of pH, dye concentration, catalyst dosage, electrolytes, energy input and kinetics of oxidation processes on the degradation efficiency are studied. COD measurements are also carried out in order to evaluate the mineralization efficiency of DB71. The effect of electrolytes on dye degradation is studied with different inorganic electrolytes. The rate constant decreases with increasing dye concentration. The degradation increases with increasing catalyst concentration and decreases with increasing dye concentration. Sonocatalytic degradation of the dye molecules are observed by UV-visible absorption and TOC measurements. The by-products formation of the sonocalytically degraded dye samples are analyzed by ESI-MS+ analysis. The catalyst is also tested for its efficiency in the degradation of real dye house effluents.

Comparison of Different Cathode Materials for Degradation of Reactive Red 120 and Electricity Generation in Photocatalytic Fuel Cell

In this study, a photocatalytic fuel cell (PFC) based on immobilized zinc oxide (ZnO) on carbon felt photoanode and activated carbon flakes as cathode was designed for the treatment of azo dye, reactive red 120 (RR120) containing wastewater and simultaneous electricity generation. Under light irradiation, generated electron-hole pairs at the photoanode travel via the external circuit to the cathode, thus generating electricity. This was the first attempt where activated carbon flakes were applied as cathode material in PFC. This study examined the influence of parameters such as light irradiation, cathode material, initial dye concentration, supporting electrolytes, pH and concentration of oxidizing agent and hydrogen peroxide (H2O2) on the efficiency of PFC to degrade azo dye of RR120 while generating electricity. Complete decolourization of up to 50 mg/L of RR120 dye was achieved but increased dye concentration significantly reduced the PFC efficiency. The PFC efficiency improved using an amalgamation of supporting electrolytes, pH and oxidizing agent at optimum levels, achieving total dye removal and producing a maximum power density of 18.58 mW/cm2.

Study on the factors influencing the dyeing performance of cotton fabric with vat dyes based on principal component analysis

Color performance on textiles is affected by many factors. In order to make the color presented more precisely, it is necessary to clarify the relationship between fabric structure and dyeing effect, so as to compensate the color displayed according to different fabrics in color matching. Pad dyeing of different cotton fabrics with vat dyes was carried out, and principal component analysis was used to analyze the comprehensive properties of fabrics. According to the factor weight, the main factors affecting the dyeing effect were obtained, and a mathematical regression model between the comprehensive values of fabric properties and the dyeing effect was established. The results showed that with the increase of dye concentration, the apparent shade depth of the fabric increased correspondingly. For different fabrics with the same dye concentration, their apparent shade depth varied with the fabric structure. There were five main factors affecting the dyeing effect of fabrics, which was glossiness, whiteness, weft density, roughness, gram weight. The comprehensive values of fabric properties were negatively correlated with the K/S values after dyeing. The smaller the comprehensive value of fabric, the deeper the apparent color after dyeing.

Modified wheat straw-derived graphene for the removal of Eriochrome Black T: characterization, isotherm, and kinetic studies.

A cost-effective and environment-benign adsorbent was prepared from an abundant agro-waste material. Wheat straw was reduced to graphene and then modified by crosslinking to epichlorohydrin. During the conversion process of wheat straw to graphene, the specific surface area increased more than 100 times (from 4 to 415 m2 g-1). The adsorption efficiency of raw wheat straw, graphene nanosheets, and modified graphene against Eriochrome Black T (EBT) were 8.0, 34.7, and 74.4%, respectively. The modified graphene was further investigated for the effect of environmental condition, i.e., pH (3 to 11), EBT concentration (25-100 mg L-1), adsorbent dosage (0.25-0.75 g L-1), contact time (5-60 min), and solution temperature (30-60 °C). The dye removal remained at a high level under a wide range of pH from 3 to 9. The EBT removal decreased from 87.3 to 54.5 by increasing dye concentration and increased from 38.2 to 85.4% by increasing adsorbent dose in the studied ranges. Dye removal also increased by mixing time from 5 to 30 min, whereas a slight drop was observed by continuing agitation up to 60 min. Conducting experiments at various temperatures revealed an endothermic process. Pseudo-first-order and pseudo-second-order models were adequate to represent the adsorption kinetics. Isotherm models suggest a multilayer adsorption of EBT molecules on heterogeneous modified graphene surface with a maximum adsorption capacity of 146.2 mg g-1. The present work demonstrated that the modified graphene obtained from available and low-cost agro-wastes could be used effectively as adsorbent against EBT from aqueous media.

Experimental and theoretical investigations of the concentration-dependent linear optical properties of Rhodamine 6G in the presence of Gold nanorods

In this research, linear optical properties of Rhodamine 6G dye were investigated at different concentrations in the absence and presence of gold nanorods. The colloidal gold nanorods were characterized by UV–vis spectrophotometer and Transmission Electron Microscope. Also, photoluminescence emissions of synthesized samples were measured. The dominant absorption peak is blue-shifted by the enhancement of Rhodamine 6G concentration, which implies that the dimerization has appeared. In contrast, the photoluminescence peak wavelength of the samples is red-shifted with an increase in dye concentration. Furthermore, the experimental results of photoluminescence are in good agreement with the theoretical model based on the Gaussian function.

Factors affecting the degradation of remazol turquoise blue (RTB) dye by titanium dioxide (TiO2) entrapped photocatalytic membrane

This study investigated the photocatalytic degradation of remazol turquoise blue (RTB) dye using titanium dioxide (TiO2) entrapped polyvinylidene fluoride (PVDF) membrane synthesized by non-solvent induced phase separation method. Numerous experiments were conducted to investigate the effects of catalyst loading in membranes, the concentration of dye, feed temperature, pH of the solution, and the addition of H2O2 to the dye solution on the removal of dye. Results were compared with the performance of virgin PVDF and modified PVDF/TiO2 membranes. The experimental results indicated that the optimum TiO2 loading in the membrane was 2 wt%, which enhanced the membrane morphology, permeability, and dye removal performance. The rate of photocatalytic degradation dropped with the increase in dye concentration. The photocatalytic efficiency of the membrane depends on the pH and the temperature of the solution.

Decolourization of Acid Orange 74 Aqueous Solutions in Presence of Multi-Walled Carbon Nanotubes under Ultrasound Irradiation

Few researches focused on the combination of ultrasound and multi-walled carbon nanotubes (MWCNT) in wastewater treatment. In this study, it was found that the combination of ultrasound and MWCNT was more effective in the removal of Acid orange 74 (AO 74) in comparison to single method. And there was a remarkable synergistic effect in the ultrasound/MWCNT combined system. The adsorption behaviour of AO 74 by the combination of ultrasound and multi-walled carbon nanotubes (MWCNT) was investigated under various experimental conditions. The adsorption performance was slightly inhibited with increasing temperature. This fact showed that the adsorption process was exothermic. The removal ratio was improved with increase in MWCNT dosage, which could be attributed to the increased adsorption sites and increased surface area. The dye removal decreasedfrom 96.0 to 41.5% with an increase in the initial concentration of dye from 15 to 100 mg/L. Lower removal ratios at higher dye concentrations were due to the saturation of adsorption, though the adsorption capacity increased from 14 to 41.5 mg/g. It may be due to the high concentration of dye which can provide a high driving force of concentration gradient to overcome all mass transfer resistance. With the increase in pH, removal ratios of AO 74 decreased gradually from pH 3 to 11. At low pH values, the surface of the adsorbent solids was positively charged and easily adsorbed the AO 74 ions having negative charges. But at high pH values, the surface charge of MWCNT got negatively charged, which did not favour the adsorption of negatively charged dye anions. Experimental isotherm data were represented with Langmuir and Freundlich adsorption models. Langmuir isotherm equation fitted better than Freundlich isotherm equation for this system, which meant adsorption of dye onto MWCNT was monolayer adsorption with a finite number of identical sites. The adsorption of AO 74 followed pseudo second-order kinetics. Kinetics analysis suggested lower temperature was favourable for AO 74 adsorption on MWCNT under ultrasound and justified the exothermic adsorption process.