Increase In Initial Dye Concentration Research Articles

Decolorization of Acid Yellow 17 by ozonation and Peroxone (O3/H2O2) Process

In this study, the decolorization of Acid Yellow 17, a mono azo dye with a wide range of applications such as in food, textiles, personal care products, and household cleaning products, was investigated in aqueous solutions using ozonation and peroxone processes. The effects of ozone gas flow rate (150, 200, and 250 L/h), ozone gas concentration (5.5, 11, and 16.5 g/m3), initial dye concentration (100, 200, and 300 mg/L), and hydrogen peroxide concentration (25, 50 and 62.5 mg/L) on decolorization in the batch bubble reactor were investigated. When the ozone gas flow rate was increased from 150 L/h to 200 L/h in the ozonation process, the removal efficiency increased from 70% to 80.2%. At gas flow rates above 200 L/h, removal was negatively affected. The removal efficiency increased with increasing ozone gas concentration, and at the end of the 45-minute reaction time, a removal efficiency of 98% was achieved at an ozone gas concentration of 16 g/m3. The increase in initial dye concentrations decreases the removal efficiency due to the increase in the amount of pollutant per unit ozone molecule. In the peroxane process, the effect of hydrogen peroxide on color removal was limited. It was determined that the ozonation process was more effective for the removal of Acid Yellow 17 from aqueous solutions.

Eco-Friendly Green Approach to the Biosorption of Hazardous Dyes from Aqueous Solution on Ragweed (Ambrosia artemisiifolia) Biomass

The presented research includes the preparation, characterization, and implementation of magnetic biosorbent (Fe3O4/RWB), obtained from ragweed (Ambrosia artemisiifolia) biomass. Fe3O4/RWB was examined for the removal of a hazardous dye, malachite green (MG), from an aqueous solution in a batch system. The effects of the experimental parameters—initial dye concentration (10–300 mg/L), contact time (0–120 min), biosorbent dose (1–5 g/L), initial pH (2–10), ionic strength (0–1 mol/L), and temperature (298–318 K) on dye biosorption—were studied. The results showed that increases in biosorbent dose, contact time, and initial pH led to an increase in biosorption efficiency, while the increase in initial dye concentration, the ionic strength, and temperature had the opposite effect. The biosorption kinetics for MG on Fe3O4/RWB were analyzed with pseudo-first-order, pseudo-second-order, and Elovich kinetic models, while the Langmuir, Freundlich and Temkin isotherm models were used for equilibrium data analysis. It was observed that the MG biosorption followed the pseudo-second-order kinetic model, whereas the Langmuir model was the best fit for the equilibrium biosorption data of MG, with a Qmax of 34.1 mg/g. the desorption of MG from Fe3O4/RWB indicated reusability in five adsorption/desorption cycles, good performance, and potential in practical applications.

Photocatalytic degradation of methylene blue using a Cu2+-modified bimetallic titanium-based metal organic framework (MIL-125) photocatalyst with enhanced visible light activity.

Cu-modified TiO2 nanoparticles derived from MIL-125 were prepared by solvothermal method for the photocatalytic degradation of methylene blue under visible light illumination. For boosting the photocatalytic performance as well as the physicochemical properties of bare sample, 2 wt % Cu2+ ions were integrated into the nodes of the MIL-125 framework. The results showed that incorporation of 2 wt % Cu2+ ions into the MOF framework had significant effects on the crystallographic structure and morphological and optical properties of photocatalytic samples, as well as catalytic activity for the methylene blue degradation reaction. The high activity profile of Cu-modified TiO2 nanoparticles derived from MIL-125 might be attributed to the increased thermal stability, lower band gap energy, and smaller crystallite size of the sample. Activity tests were carried out at five varying MB initial concentrations and four different pH values. According to the findings, an increase in initial dye concentration resulted in a decrease in degradation efficiency. It was observed that increasing the pH value in the range of 3-11 initially led to higher degradation rates until pH 7, after which the degradation rate began to decline.

KINETIC, ISOTHERM AND THERMODYNAMIC STUDIES OF THE ADSORPTION OF CRESOL RED DYE USING AGRICULTURAL WASTES

Agricultural wastes and plant biomass are alternative low-cost adsorbents because they can be used without or with a minimum processing. In the present study, batch experiments were carried out to study the adsorption of cresol red (CR) unto mango leaf (ML) and orange peel (OP). Several parameters that affect adsorption process such as pH, adsorbent dosage, contact time, initial dye concentration and temperature were investigated. FTIR and SEM were used to determine the functional group responsible for adsorption. The results revealed that the highest adsorption efficiency was at pH 5 for the two adsorbents. It was also discovered that CR removal efficiency increased with the increase in contact time and adsorbent dosage while adsorption capacity was higher with increase in initial dye concentration but removal efficiency was lowered. The kinetics conform with the pseudofirst-order kinetic model for mango leaf but conform with the pseudo-second-order kinetic for orange mesocarp due to the value of the correlation coefficient (R2). Based on the value of correlation coefficient, the experimental results for the removal by mango leaf best fitted the Langmuir isotherm model with monolayer adsorption capacity of 70.64 mg. g-1, while Freundlich isotherm model was best fitted to the experimental results for the adsorption of CR by Orange peel. The thermodynamic results revealed that the process is spontaneous and endothermic.

Adsorptive decolorization of brilliant green dye in aqueous media using various modified MOF-5 adsorbents

Dye pollution in environmental water is a serious problem worldwide, posing significant environmental and health concerns. To effectively address this problem, this study investigates the adsorptive decolorization of brilliant green (BG) dye in aqueous media by using various metal-organic frameworks (MOF-5)-based adsorbents modified with industrial wastes (coal fly ash (CFA) and rice husk ash (RHA)). The adsorption experiments were conducted to evaluate their performance under varying conditions, and the synthesized and spent adsorbents (selected) were characterized. The results showed that the adsorbent samples possessed the characteristics of a good adsorbent. MOF-5 coated with thermally treated RHA at 900 °C (MOF-5@ RHA900 – with BET surface area = 91.6810 m2 g−1) has the highest observed BG dye adsorption efficiency (92%) and adsorption capacity (30.22 mg g−1) at adsorbent mass of 1.4 g, contact time of 2 h, and initial dye concentration of 20 mg L−1. BG dye removal increased with an increase in contact time and adsorbent amount and decreased with an increase in initial dye concentration. The adsorption kinetics and isotherm equilibrium studies revealed that the adsorption data were best fitted to the pseudo-second-order kinetic model (R2 = 0.9507) and Langmuir isotherm model (R2 = 0. 0.9929), respectively. These findings highlight the potential of mesoporous MOF-5@ RHA900 as an effective adsorbent for BG dye decolorization in aqueous media, with implications for water treatment and the utilization of industrial waste materials.

Enhanced photocatalytic activity of Cu and Ni-doped ZnO nanostructures: A comparative study of methyl orange dye degradation in aqueous solution

Heterogeneous photocatalysis has been considered one of the most effective and efficient techniques to remove organic contaminants from wastewater. The present work was designed to examine the photocatalytic performance of metal (Cu and Ni) doped ZnO nanocomposites in methyl orange (MO) dye degradation under UV light illumination. The wurtzite hexagonal structure was observed for both undoped/doped ZnO and a crystalline size ranging between 8.84 ± 0.71 to 12.91 ± 0.84 nm by X-ray diffraction (XRD) analysis. The scanning electron microscope (SEM) and energy dispersive X-ray (EDX) revealed the irregular spherical shape with particle diameter (34.43 ± 6.03 to 26.43 ± 4.14 nm) and ensured the purity of the individual elemental composition respectively. The chemical bonds (O–H group) and binding energy (1021.8 eV) were identified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results respectively. The bandgap energy was decreased from 3.44 to 3.16 eV when Ni dopant was added to the ZnO lattice. The comparative photocatalytic activity was observed in undoped and doped nanocomposites and found to be 76.31%, 81.95%, 89.30%, and 83.39% for ZnO, Cu/ZnO, Ni/ZnO, and Cu/Ni/ZnO photocatalysts, respectively, for a particular dose (0.210 g) and dye concentration (10 mg L−1) after 180 min illumination of UV light. The photocatalytic performance was increased up to 94.40% with the increase of pH (12.0) whereas reduced (35.12%) with an increase in initial dye concentration (40 mg L−1) using Ni/ZnO nanocomposite. The Ni/ZnO nanocomposite showed excellent reusability and was found 81% after four consecutive cycles. The best-fitted reaction kinetics was followed by pseudo-first-order and found reaction rate constant (0.0117 min−1) using Ni/ZnO nanocomposite. The enhanced photodegradation efficiency was observed due to decreases in bandgap energy and the crystalline size of the photocatalyst. Therefore, Ni/ZnO nanocomposite could be used as an emerging photocatalyst to degrade bio-persistent organic dye compounds from textile wastewater.

Preparation of hydrochar bio-based catalyst for fenton process in dye-containing wastewater treatment

The use of synthetic dyes in the textile industry pollutes a huge amount of water. Thus, wastewater discharged from many textile companies to the receiving environment without being treated causes serious environmental and human health problems. The development of new techniques has become imperative. In this study, it was aimed to remove anionic dye (RR180) and cationic dye (BR18) by Fenton-like and adsorption process with hydrochars obtained from laurel leaves and watermelon peels. In the comparison of the adsorption and Fenton-like processes used in the dye removal of the produced bio-based materials, the Fenton-like process was selected in order to enhance the highest removal efficiency. The effects of various operating factors such as solution pH, amount of catalysts, hydrogen peroxide (H2O2) concentration, and initial dye concentration were evaluated on both dyes removal. The experimental results demonstrated that 99.8% RR180 dye and 98.8% BR18 dye removal efficiency were observed for an initial dye concentration of 100 mg/L with an adsorbent concentration of 1 g/L, H2O2 concentration of 15 μL/L, and optimum pH at the end of 60 min of reaction time. It was observed that an increase in initial dye concentration caused to decrease the dye removal efficiency. The optimum pH for the highest RR180 and BR18 dye removal was 4 and 6, respectively. It was observed that the increase in H2O2 concentration in the solution also decreased the dye removal efficiency. It turned out that catalysts obtained from hydrochars are an effective process for the high removal performance of cationic and anionic dyes.

Fixed‐bed column adsorption of methyl orange by poly(vinyl pyrrolidone)‐functionalized manganese oxide

AbstractBACKGROUNDFixed‐bed column adsorption provides a practical approach for decontamination of wastewater from toxic azo dyes. A novel water‐stable poly(vinyl pyrrolidone)‐functionalized manganese oxide hydrothermally prepared for methyl orange azo dye adsorption is reported.RESULTSSurface studies of the composite were conducted using scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction and surface area analysis. The surface area of the composite (113 m2 g−1) was greater than that of plain metal oxide (108 m2 g−1). The point of zero charge was calculated using the salt addition method. A continuous flow of methyl orange was carried out in a 40 cm long glass column under different operating conditions determining the breakthrough curve and the breakthrough point time. Experiments were carried out as a function of initial dye concentration (10–30 mg L−1), bed height (0.6–1.5 cm) and rate of flow (5–20 mL min−1) from the column at constant temperature and pH.CONCLUSIONSThe saturation time increases from 700 to 3500 min with increase in bed length. The saturation time decreases from 2000 to 400 min with an increase in initial dye concentration. Similarly, when the flow rate is increased the saturation time and dye adsorption are reduced and the breakthrough curve becomes steeper. The adsorption data were evaluated using the Thomas model to calculate maximum adsorption at various flow rates and the Yoon–Nelson model to identify exactly the saturation point, confirming that the rate of reaction increases with increasing flow rate. © 2022 Society of Chemical Industry (SCI).

Synthesis, characterization, and photocatalytic performance of methyl orange in aqueous TiO2 suspension under UV and solar light irradiation

Nano-crystalline titanium dioxide (TiO2) photocatalyst has been extensively utilized in the last few decades because of its strong oxidizing power, redox selectivity, and higher photocatalytic performance. In this work, TiO2 nanoparticle (NPs) was synthesized, characterized, and applied for the degradation of methyl orange (MO) dye in an aqueous solution under UV and solar light irradiations. The XRD results showed dominated anatase phase (82%) with a smaller crystalline size (18.23 nm). A rough surface with a uniform spherical shape was observed by SEM analysis. FTIR and UV–Vis/DRS spectroscopy confirmed the stretching vibration of the hydroxyl groups and higher absorption edge towards longer wavelength with smaller bandgap energy (3.12 eV) of TiO2 lattice structure. The activity of TiO2 NPs was carried out from the degradation of MO dye as a model contaminant for textile effluent in presence of UV/solar irradiation. The photodegradation efficiency of MO dye (15 mg L−1) was observed at 85.90% and 96.38% for 0.150 g and 0.030 g of TiO2 NPs at natural pH (7.0), after 5 h of UV and solar light irradiation. The respective rate constants were determined to be 0.0063 min−1 and 0.01 min−1 for UV and simulated solar light irradiation respectively, and exhibited the best-fitted kinetic model of pseudo-first-order. The photodegradation efficiency was increased with the decrease of pH, while efficiency decreased with an increase in initial dye concentration. The obtained result from TiO2 NPs was compared with commercially available Degussa P25 catalyst. The photocatalyst reusability test and reaction mechanism were also evaluated. The study suggests that TiO2 NPs are a promising photocatalyst that can be used for the degradation of organic dye compounds from textile wastewater towards the sustainable management of environment.

Prednosti bojenja vunenih vlakana na 60 °C nakon predhodne modifikacije alkoholom

This research work describes the advantages of dyeing wool fibers at 60 °C after pre-treatment with alcohol. Wool is a natural fiber. This fiber can be dyed with acid, metal-complex and other dyes. Acid dyes should be soluble in water and most commonly used for dyeing wool, silk and nylon. Wool fibers with 100 % chemical composition were used in this study. The wool fiber was pre-treated in alcohol (npentanol) at a temperature of 60 °C for 30 minutes. Pre-treated wool fibers were dyed with Supramin Blau acid dye. The time for dyeing samples of wool fibers was 5, 10, 20, 30, 40, 50 and 60 minutes. The process of dyeing wool fibers with acid dye at 60 °C showed a higher degree of exhaustion and adsorption capacity when wool was pre-treated with n-pentanol compared to wool that was not pre-treated with n-pentanol. A constant increase in the degree of dye exhaustion on the pretreated wool fiber was observed during the increase in initial dye concentration. A longer dyeing time for pre-treated wool results in a higher degree of dye exhaustion. Models Weber-Morris and Elovich are applicable for describing the adsorption flow because there is very little scatter around the ideal curve, so functional straight lines cover most points very well.

Evaluation of using electric arc furnace slag as an adsorbent for dyes removal

ABSTRACT The adsorption of two common textile dyes – orange G and methyl violet – onto an electric arc furnace slag was studied. Batch study shows that adsorption of orange G and methyl violet were dependent highly on pH value. Removal of orange G decreased with the increase of initial pH with optimum pH observed at 3. Moreover, the total removal percentage was low and did not exceed 45% at optimum pH. However, the removal of methyl violet increased with initial pH, and maximum removal (about 94%) was observed at pH 11. Based on the obtained data, methyl violet dye was chosen to study the effect of agitation speed, initial dye concentration, adsorbent dosage and adsorbent particle size on adsorption capacity. For the adsorbent under investigation, equilibrium adsorption capacity qe (mg/g) for orange G and methyl violet dyes were 17.4 mg/g and 3.29 mg/g, respectively. Also, batch studies show that the adsorption rate for methyl violet was rapid at the beginning and slowed down till equilibrium.In contrast, the orange G adsorption rate was slow until it approached equilibrium. The Pseudo-Second order model well represented the kinetics studies data. The value of K2 increased with adsorbent dosage while the K2 value decreased with an increase in initial dye concentration and adsorbent particle size. Equilibrium data were evaluated using Langmuir and Freundlich isotherm models and it was found that the Langmuir isotherm model best fitted to the experiments data.

Fabrication of polyacrylonitrile/polypyrrole nanofibrous mat and its adsorption to the cationic yellow dye

Electrospun polyacrylonitrile membrance was treated with pyrrole and ferric chloride in situ polymerization method. A polyacrylonitrile/polypyrrole (PAN/PPY) nanofibrous mat was fabricated and used in the adsorption of cationic yellow dye. The nanofibrous mat was characterized by scanning electron microscope (SEM), Fourier infrared spectroscopy (FTIR) and thermal gravity (TG). The results showed that the polypyrrole was formed and deposited on the nano polyacrylonitrile fiber evenly. PAN/PPY mat was used as adsorbents for the removal of cationic yellow dye in aqueous solution. Adsorption results indicated that the adsorption capacity increased with the increase in initial dye concentration and adsorption time and temperature. Adsorption kinetics analysis showed the adsorption process can be described using the pseudo-second-order model. Isotherm data were in best agreement with the Nernst isotherm model. Thermodynamic analysis suggested that the adsorption process is endothermic and spontaneous in nature.

Kinetic and thermodynamic investigations of sewage sludge biochar in removal of Remazol Brilliant Blue R dye from aqueous solution and evaluation of residual dyes cytotoxicity

Biochar derived from sewage sludge has emerged as an alternative for sustainable utilization as a soil amendment. However, the use of sewage sludge biochar (SSB) has been less explored in the field of wastewater treatment. Therefore, the purpose of this study was to investigate the efficiency of biochar prepared from sewage sludge at 450 °C (SSB-450), as an adsorbent for the removal of Remazol Brilliant Blue R (RBBR) from an aqueous solution. Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize SSB-450, with maximum RBBR removal efficiency. The removal of RBBR from aqueous solution by SSB-450 was investigated in batch mode at varying adsorbent dose, contact time, initial RBBR dye concentration temperature and pH. The BET analysis showed the type IV isotherm that indicates the mesoporous structure of SSB-450. The total pore volume and BET specific surface area of SSB-450 particles were found to be 3.936 cm −3 /g and 12.447 m 2 /g, respectively. The RBBR dye adsorption ( q e ) at equilibrium by SSB-450 was found to increase from 8.56 to 80.6 mg g −1 with an increase in initial dye concentration from 10 to 100 mg L −1 . The maximum monolayer adsorption capacity (qmax) was 126.59 mg/g of SSB-450, determined by the Langmuir adsorption model. At various RBBR dye concentrations (10 to 100 mg/g), the range of the separation factor ( R L ) was 0.98–0.9, which indicates the favourable adsorption of RBBR dye onto the surface of SSB-450. Besides, Evans blue and triphenyl tetrazolium chloride (TTC) staining of Allium cepa L. roots germinated with dye solutions revealed that biochar treated residual RBBR was non-cytotoxic. • Sewage sludge biochar prepared at 450 °C (SSB-450) efficiently removed RBBR. • Type IV isotherm indicated the mesoporous structure of SSB-450. • Linear Langmuir model fitted well with equilibrium adsorption data. • Pseudo-second-order kinetics model best described adsorption of RBBR. • RBBR adsorption by SSB-450 was spontaneous and endothermic.

Factors Affecting the Simultaneous Removal of Nitrate and Reactive Black 5 Dye via Hydrogen-Based Denitrification

Textile wastewater (TW) contains toxic pollutants that pose both environmental and human health risks. Reportedly, some of these pollutants, including NO3−, NO2− and reactive black 5 (RB-5) dye, can be removed via hydrogen-based denitrification (HD); however, it is still unclear how different factors affect their simultaneous removal. This study aimed to investigate the effect of H2 flow rate, the sparging cycle of air and H2, and initial dye concentration on the TW treatment process. Thus, two reactors, an anaerobic HD reactor and a combined aerobic/anaerobic HD reactor, were used to investigate the treatment performance. The results obtained that increasing the H2 flow rate in the anaerobic HD reactor increased nitrogen removal and decolorization removal rates. Further, increasing the time for anaerobic treatment significantly enhanced the pollutant removal rate in the combined reactor. Furthermore, an increase in initial dye concentration resulted in lower nitrogen removal rates. Additionally, some of the dye was decolorized during the HD process via bacterial degradation, and increasing the initial dye concentration resulted in a decrease in the decolorization rate. Bacterial communities, including Xanthomonadaceae, Rhodocyclaceae, and Thauera spp., are presented as the microbial species that play a key role in the mechanisms related to nitrogen removal and RB-5 decolorization under both HD conditions. However, both reactors showed similar treatment efficiencies; hence, based on these results, the use of a combined aerobic/anaerobic HD system should be used to reduce organic/inorganic pollutant contents in real textile wastewater before discharging is recommended.

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.

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.

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.

Carbonized Lanthanum-Based Metal-Organic Framework with Parallel Arranged Channels for Azo-Dye Adsorption.

In this contribution, the synthesis of the metal−organic framework (MOF) based on lanthanum that exhibits trigonal prism shape is presented. The length of a single side of this structure ranges from 2 to 10 μm. The carbonized lanthanum-based organic framework (CMOF–La) maintained the original shape. However, the lanthanum oxide was reshaped in the form of rods during the carbonization. It resulted in the creation of parallel arranged channels. The unique structure of the carbonized structure motivated us to reveal its adsorption performance. Therefore, the adsorption kinetics of acid red 18 onto a carbonized metal−organic framework were conducted. Various physicochemical parameters such as initial dye concentration and pH of dye solution were investigated in an adsorption process. The adsorption was found to decrease with an increase in initial dye concentration. In addition, the increase in adsorption capacity was noticed when the solution was changed to basic. Optimal conditions were obtained at a low pH. Kinetic adsorption data were analyzed using the pseudo-first-order kinetic model, the pseudo-second-order kinetic model and the intraparticle diffusion model. The adsorption kinetics were well fitted using a pseudo-second-order kinetic model. It was found that the adsorption of anionic dye onto CMOF–La occurs by hydrophobic interactions between carbonized metal-organic framework and acid red 18.

Phytoremediation of azo dye methyl red by macroalgae Chara vulgaris L.: kinetic and equilibrium studies.

Phytoremediation is an innovative, eco-friendly, and solar-driven technique, which becomes a well-known alternative solution for remediation of hazardous dyes from wastewater. In present research work, potential of a submerged fresh water macroalgae Chara vulgaris L. (C. vulgaris) examined for removal of acidic azo dye methyl red (MR) in its solution form. A series of experiments were done with C. vulgaris to predict the effects of different parameters viz. contact time, initial dye concentration, amount of macroalgae, and pH. The increase in initial dye concentration directly impacts on the potential of macroalgae. The decolorization percentage declined with increase in initial dye concentration. The equilibrium condition was found to achieve after contact time of approximately 48h. The decolorization of MR dye was found to be favorable at pH5. The macroalgae was successfully utilized repeatedly with MR for eight cycles in batch experiments. The kinetics of phytoremediation of MR dye was studied with help of pseudo-first-order, pseudo-second-order, and Elovich kinetic models and the results were well suited to pseudo-second-order kinetic model with the correlation value R2 ≥ 0.99. In addition, the experimental data was also assessed by using Langmuir and Freundlich adsorption equilibrium isotherms. The results of phytoremediation data was found to be in favor of Freundlich equilibrium isotherm which having the correlation value R2 ≥ 0.977. The intraparticle diffusion model also studied to interpret the macroalgae phytoremediation mechanism for phytoremediation of MR. The surface interactions of C. vulgaris were investigated before and after the removal of dye with Fourier transform-infrared spectroscopy (FTIR) technique. On the basis of these studies, a hypothetical mechanism has also been proposed to depict the phytoremediation of acidic azo dye by C. vulgaris.

Equilibrium, Kinetics, and Thermodynamic Studies of Malachite Green Adsorption onto Fig (Ficus cartia) Leaves.

The release of dyes from dying industries such as leather, paper, and textiles is an important cause of environmental pollution. In the present study, the batch adsorption measurements were carried out using stimulated aqueous solutions and the effect of operating variables such as initial malachite green concentration, amount of adsorbent, solution pH, contact time, and solution temperature, were investigated. The experimental result showed that the percentage removal decreased with an increase in initial dye concentration but increased as pH of the solution, contact time, and adsorbent dose increased. The equilibrium data were analyzed using Langmuir adsorption isotherm, Freundlich adsorption isotherm, and Tempkin isotherm models, and it was observed that the Langmuir adsorption isotherm better described the adsorption process. The monolayer adsorption capacity of activated carbon prepared from fig leaves for malachite green adsorption was found to be 51.79 mg/g at 298 K. Furthermore, the adsorption kinetics of the dye was investigated, and the rate of adsorption was found to follow the pseudo-first-order kinetic model with intraparticle diffusion as one of the rate-determining steps. The negative value of ΔG0 and the positive values of ΔH0 indicate the spontaneous and endothermic nature of the adsorption process, respectively. The experimental result obtained in the present study and comparison with other reported adsorbents indicate that activated carbon prepared from fig leaves could be used as a low-cost alternative adsorbent for the removal of malachite green from aqueous solution.