Initial Reactive Black 5 Concentration Research Articles

Accessible Eco-Friendly Method for Wastewater Removal of the Azo Dye Reactive Black 5 by Reusable Protonated Chitosan-Deep Eutectic Solvent Beads.

A novel approach to enhance the utilization of low-cost and sustainable chitosan for wastewater remediation is presented in this investigation. The study centers around the modification of chitosan beads using a deep eutectic solvent composed of choline chloride and urea at a molar ratio of 1:2, followed by treatment with sulfuric acid using an impregnation accessible methodology. The effectiveness of the modified chitosan beads as an adsorbent was evaluated by studying the removal of the azo dye Reactive Black 5 (RB5) from aqueous solutions. Remarkably, the modified chitosan beads demonstrated a substantial increase in adsorption efficiency, achieving excellent removal of RB5 within the concentration range of 25-250 mg/L, ultimately leading to complete elimination. Several key parameters influencing the adsorption process were investigated, including initial RB5 concentration, adsorbent dosage, contact time, temperature, and pH. Quantitative analysis revealed that the pseudo-second-order kinetic model provided the best fit for the experimental data at lower dye concentrations, while the intraparticle diffusion model showed superior performance at higher RB5 concentration ranges (150-250 mg/L). The experimental data were successfully explained by the Langmuir isotherm model, and the maximum adsorption capacities were found to be 116.78 mg/g at 298 K and 379.90 mg/g at 318 K. Desorption studies demonstrated that approximately 41.7% of the dye could be successfully desorbed in a single cycle. Moreover, the regenerated adsorbent exhibited highly efficient RB5 removal (80.0-87.6%) for at least five consecutive uses. The outstanding adsorption properties of the modified chitosan beads can be attributed to the increased porosity, surface area, and swelling behavior resulting from the acidic treatment in combination with the DES modification. These findings establish the modified chitosan beads as a stable, versatile, and reusable eco-friendly adsorbent with high potential for industrial implementation.

Removal of Reactive Black 5 by UV-C assisted peroxydisulfate process: Effect of parameters, kinetic study, and phytotoxicity assessment

ABSTRACT Photochemical removal of Reactive Black 5 (RB5) was investigated by the UV-C assisted peroxydisulfate (UV-C/PDS) process. Parameters affecting the removal of RB5 were examined. Activation of PDS by UV-C light significantly improved the removal efficiency compared to direct photolysis or PDS alone. The removal of RB5 by UV-C/PDS process fitted well with the pseudo first-order kinetic model under all tested conditions. Almost complete removal of RB5 was achieved at the end of 120 min within the pH range of 3–7, whereas 90.7 and 89.4% removal efficiency values were observed at pH = 9 and 11, respectively. An increase in PDS dosage in the range of 0.25–1 mM led to a rise in removal from 48.5 to 97.3% after 120 min, and a complete removal was observed with a dosage higher than 2 mM. Pseudo firstorder rate constant (kobs) increased linearly with PDS dosage from 0.0058 to 0.0518 min−1 in the 0.25 mM − 2.3 mM concentration range. The removal efficiency decreased with an increase in the initial concentration of RB5 from 20 to 50 mg L−1 and an exponential correlation was observed between kobs and initial concentration of RB5. Scavenging experiments conducted using t-butyl alcohol and ethyl alcohol implied that both sulphate and hydroxyl radicals were involved in the removal of RB5. Adding HCO3 − decreased the removal of RB5 within the range of 1–30 mM. The presence of CI− showed a negative impact on the removal at low concentrations (1–15 mM) and NO3 − slightly inhibited the removal of RB5. With corresponding stoichiometric PDS dosage, almost a complete mineralisation was achieved for RB5 solution and simulated dyebath effluent after 720 min of reaction time. EE/O values were determined to be 91.0, 76.8, and 41.1 kWh m−3 order−1 for UV-C/H2O2, UV-C/PMS, and UV-C/PDS processes, respectively. The phytotoxicity tests indicated that the intermediates could be more toxic than the parent compound.

Composite Activated Carbon Modified with AlCl3 for the Effective Removal of Reactive Black 5 Dye from Wastewaters

Many industries use huge amounts of synthetic dyes which may release into the wastewater in dyeing processes causing serious damage to aquatic life as they are recalcitrant, nonbiodegradable, stable to oxidizing agents, and toxic. Adsorption on activated carbon has been found to be a very efficient treatment method. In this work, a new adsorbent material composed of activated carbon and aluminum chloride (AC-Al) was prepared for the removal of a commercial anionic and anthraquinonic reactive dye, i.e., Reactive Black 5 (RB5) under various experimental conditions. Several parameters, such as the adsorbent’s dosage, initial RB5 concentration, pH, and contact time, were studied in order to determine the feasibility of AC-Al. According to the results, it was found that there was an increase in RB5 removal as the adsorbent’s dosage increased, especially, in pH 2 ± 0.1, where the removal rate increased, and reaching 100% by 1.0 g/L of AC-Al. Freundlich isotherm and pseudo-second-order kinetic models adequately fit the experimental data, indicating that favorable and heterogeneous adsorption occurred, closer to chemisorption. According to thermodynamics, it was found that the adsorption procedure was endothermic in nature (∆H0 = 62.621 kJ/mol) and spontaneous (∆G0 < 0), and according to the positive value of ∆S0 0.0293 (kJ/mol∙K), there is an increase in random interaction between solid and liquid interfaces. Finally, the AC-Al adsorbent was successfully regenerated and reused for four cycles.

Converting synthetic azo dye and real textile wastewater into clean energy by using synthesized CuO/C as photocathode in dual-photoelectrode photocatalytic fuel cell.

Cathode in photocatalytic fuel cell (PFC) plays a crucial role in degradation of organic contaminants. In this study, synthesized copper oxide (CuO) was loaded on carbon plate and used as photocathode in PFC for degradation of synthetic azo dye Reactive Black 5 (RB5) and real textile wastewater. Morphology and structural phase of the synthesized CuO were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Several operating parameters had been investigated such as light irradiation, initial dye concentration, and pH of azo dye solution within 6h of irradiation time. The lowest initial concentration of RB5 (10mg L-1) achieved 100% color removal compared to the highest initial concentration (40mg L-1) which only achieved 77.1% color removal within 6h of irradiation time. The influence of external resistance was significant in electricity generation but trivial in dye degradation efficiency. The external resistance of 6000 Ω yielded highest maximum power density, with Pmax of 0.2631μWcm-2, followed by 1000 Ω (0.2196μWcm-2) and 8000 Ω (0.1587μWcm-2), respectively. The real textile wastewater with dilution ratio (DR) 1:6 yielded the highest energy conversion efficiency, η (3.62%), followed by DR 1:4 (3.19%) and DR 1:2 (1.96%), respectively.

Synthesis of MMT−CuFe2O4 Composite as a Peroxymonosulfate Activator for the Degradation of Reactive Black 5

AbstractCopper ferrite nanoparticles loaded on montmorillonite (MMT−CuFe2O4) were prepared by co‐precipitation method and applied as catalyst for activation of peroxymonosulfate (PMS) in degradation of reactive black 5 (RB5). The maximum removal efficiency of RB5 completely depends on the operating parameters and the highest removal percentage was obtained at MMT−CuFe2O4 dosage of 250 mg/L, PMS concentration of 4 mM, initial RB5 concentration of 50 mg/L and time of 15 min. The presence of anions such as Cl−, NO3−, HCO3−, and SO42− showed a significant limitation in the degradation of RB5 in the MMT−CuFe2O4/PMS system. Trapping experiments showed that ⋅OH and SO4⋅− radicals were involved in the catalytic degradation of RB5, however ⋅OH is the major specie in the catalysis system. Consecutive cycles were considered for testing the reusability of MMT−CuFe2O4; its results showed the stability of five consecutive cycles. The toxicity test was evaluated using Daphnia magna and the results illustrated a substantial drop in the toxicity of the solution treated. The significant reduction of TOC during RB5 degradation and the production of SO42−, NH4+ and NO3− confirm the proper progress of pollutant mineralization. The high catalytic performance of the catalyst in a short time compared to other removal systems emphasizes that MMT−CuFe2O4 can be suggested as a promising catalyst for the degradation of RB5 from aqueous solutions.

Comparative Photocatalytic Activity and Total Organic Carbon Removal Efficiency of TiO2 And ZnO for Reactive Black 5 Photodegradation

AbstractThe photocatalytic performance of TiO2 and ZnO was comparatively studied for photocatalytic degradation of reactive black 5 (RB5) under artificial UVC irradiation. The effect of initial solution pH, catalyst concentration, initial RB5 concentration, purging oxygen rate, stirring rate, and process temperature on the degradation process by TiO2 and ZnO was investigated. In addition, total organic carbon (TOC) analysis has been employed for each parameter to detect the presence of organic intermediates and the photodegradation performance of catalysts simultaneously with the photocatalytic degradation process. The RB5 photodegradation was more rapid in the aqueous medium by TiO2 under UVC irradiation compared to the catalysis by ZnO. On the other hand, the slower photocatalysis by ZnO resulted in generating more organic intermediates. The structural and morphological analyses of photocatalysts TiO2 and ZnO were performed using XRD and FE‐SEM techniques. The UV‐vis spectroscopy measurements supported that the TiO2 demonstrated evidently better photocatalytic activity than ZnO for RB5 degradation.

Fabrication of metal-organic framework Universitetet i Oslo-66 (UiO-66) and brown-rot fungus Gloeophyllum trabeum biocomposite (UiO-66@GT) and its application for reactive black 5 decolorization

Many various industries use synthetic dyes as their raw materials. These dyes have triggered environmental problems because of the occurring effluents, and one of the environmentally safe solutions for this problem is biodegradation through microorganisms. Reactive Black 5 (RB5) dye degradation was performed by utilizing a metal-organic framework Universitetet i Oslo-66 (UiO-66) and Gloeophyllum trabeum (GT) fungus biocomposite. The UiO-66@GT composite was fabricated by inoculating the fungal culture in flasks with the PDB medium that contained UiO-66. This biocomposite was applied to decolorize and degrade RB5 dye, while pure GT culture can decolorize about 36.47% in five days. The percentage of RB5 decolorization was shown to be increased with the addition of UiO-66; the composite could decolorize RB5 up to 72.55% after five days incubation period. Moreover, the optimum conditions for the 100% targeted rate of RB5 decolorization found by the Response Surface Methodology (RSM) are: initial RB5 concentration (72.54 mg L -1 ), pH (6.53), and temperature (38.06 °C). Two novel metabolites from RB5 decolorization by the composite were detected based on LCMS-QTOF analysis and were used to propose a degradation pathway: 6-((1-amino-7,8-dihydroxy-6-sulfonaphthalen-2-yl) diazinyl) cyclohexa-2,4-dien-1-ide ( m / z = 360) and 3,4-diamino-5,6-dihydroxy-1,2,7,8-tetrahydronaphthalene-2,7-disulfonic acid ( m / z = 354).

Reactive Black 5 Removal with Ozone on Lab-scale and Modeling

ABSTRACT This study investigates modeling the ozone removal of the Reactive Black 5 (RB5) dye from an aqueous solution using a combination of nonlinear regression (NLR), multiple linear regression (MLR), and Intrinsically multiple linear regression (IMLR) models. Lack of use and evaluation of the IMLR method in estimating RB5 removal by ozonation attract attention. Experimental data were used in the R Core Team software for the development of the models and estimate of RB5 removal by ozone. The effects of variables such as pH, contact time, initial dye concentration, and applied ozone dosage on RB5 removal by ozone were investigated. Maximum 92% RB5 removal rate was obtained at pH 8, 60 min contact time, 100 mg/L initial RB5 concentration, and applied ozone dosage of 66 mgO3/L. Under these conditions, the amount of specific ozone consumption was 0.678 gO3/gRB5. In order to compare the models, coefficient of determination (R2) and mean square error (MSE) were utilized as reliability and precision criteria. The best R2 and MSE values for the IMLR model were calculated as 0.8940 and 0.098, respectively. To determine the appropriate model and coefficients, analysis of variance (ANOVA), and t-test were used, respectively. Whether the model is within the confidence interval was determined by the significance value (p) and the variation was <5% for the IMLR model. As a result, it was found that the best method for modeling RB5 removal from aqueous solution by ozone was the IMLR method. Detailed explanations on results were introduced in the study.

Adsorption of Reactive Black 5 Dye from Aqueous Solutions by Carbon Nanotubes and its Electrochemical Regeneration Process

: Removal of Reactive Black 5 (RB5) dye from aqueous solutions was investigated by adsorption onto Multi-walled Carbon Nanotubes (MWCNTs) and Single-walled Carbon Nanotubes (SWCNTs). A Taguchi orthogonal design including pH, initial RB5 concentration, contact time, and CNTs dose, was used in 16 experiments. The results showed that all four factors were statistically significant, and the optimum conditions for both adsorbents were as follows: pH of 3, adsorbent dose of 1000 mg/L, RB5 concentrations of 25 mg/L, and contact time of 60 min. An equilibrium study by Isotherm Fitting Tool (ISOFIT) software showed that Langmuir isotherm provided the best fit for RB5 adsorption by CNTs. The maximum predicted adsorption capacities for the dye were obtained as 231.84 and 829.20 mg/g by MWCNTs and SWCNTs, respectively. The results also indicated that the adsorption capacity of SWCNTs was about 1.21 folds higher than that of MWCNTs. Studies of electrochemical regeneration were conducted, and the results demonstrated that RB5-loaded MWCNTs and SWCNTs could be regenerated (86.5% and 77.3%, respectively) using the electrochemical process. Adsorbent regeneration was mostly due to the degradation of the dye by the attack of active species such as chlorate, H2O2, and, •OH, which were generated by the electrochemical oxidation process with Ti/RuO2-IrO2-TiO2 anodes. The results of Gas Chromatography-Mass Spectrometry (GC-MS) analysis showed that acetic acid, 3-chlorobenzenesulfonamide, and 1,2-benzenedicarboxylic acid were produced after adsorbent regeneration by the electrochemical process in the solution of regeneration. The adsorption and regeneration cycles showed that the electrochemical process with Ti/RuO2-IrO2-TiO2 and graphite is a good alternative method for the regeneration of CNTs and simultaneous degradation of the dye.

Utilisation of eco-friendly and low cost 3D graphene-based composite for treatment of aqueous Reactive Black 5 dye: Characterisation, adsorption mechanism and recyclability studies

The current research aimed to develop an eco-friendly three-dimensional (3D) graphene oxide/high molecular weight chitosan (GO/HCS) composite for the removal of Reactive Black 5 (RB5) dye. The adsorption performance of the 3D GO/HCS adsorbent was elucidated by varying the adsorbent dosage (1–50 mg), agitation speed (50–250 rpm), initial RB5 concentration (100–600 mg/L), pH (2–11), temperature (30–70 °C) and contact time (1–90 min). The equilibrium behaviour of the 3D GO/HCS adsorbent was best described by the Langmuir isotherm (SNE: 2.27 to 3.92), demonstrating a maximum adsorption capacity of 638.93 mg/g. The kinetic study showed a relatively fast RB5 dye adsorption by the as-synthesised 3D GO/HCS composite. The dye uptake by the composite was thermodynamically spontaneous (∆G: -39.15 to -17.90 kJ/mol) and endothermic (∆H: 5.60 to 31.64 kJ/mol). The adsorption mechanisms were assayed by pH test, Fourier transform infrared and X-ray photoelectron spectroscopy. The results substantiated that electrostatic attraction and π − π stacking were the prevailing uptake mechanisms. The 3D GO/HCS composite exhibited high structural stability and RB5 dye removal efficiencies within pH of 2–10. Furthermore, the exhausted 3D GO/HCS adsorbent was easily recovered from the liquid phase. The adsorbent was successfully applied in 5 cycles of adsorption-regeneration, preserving 90% of its adsorption capacity. The excellent adsorption and regeneration efficiencies inferred that the 3D GO/HCS macrostructure was highly efficient and recyclable for aqueous RB5 dye sequestration.

LDH of NiZnFe and its composites with carbon nanotubes and data-palm biochar with efficient adsorption capacity for RB5 dye from aqueous solutions: Isotherm, kinetic, and thermodynamics studies

In the study, the layered double hydroxide (LDH) of NiZnFe and its composites with date-palm biochar (LDH-DPb) and carbon nanotubes (LDH-cnt) were synthesized for adsorbing reactive black 5 (RB5) dye from aqueous solutions. In the first 5 min, rapid adsorption was followed by a gradual increase in both dye uptake and removal efficiency of up to 60 min of starting time. In the investigated pH range (3.0–8.0), the removal efficiency linearly decreased while the sorption capacity linearly increased for all three adsorbents as their doses increased to 0.3 or 0.4 g following a decreasing trend up to 0.6 g. By increasing the initial RB5 concentration from 10 to 100 mg L−1, the removal efficiency linearly decreased. A nearly perfect fitting of the pseudo-second-order kinetic model to the adsorption data was observed; however, the Elovich kinetic model showed the heterogeneous surface of adsorbents with chemisorption. At the solid–liquid interface, from a thermodynamics point of view, we obtained the nonspontaneous nature of the adsorption of RB5 dye of the studied adsorbents with an increased disorder, which supported the endothermic nature onto the studied adsorption process. Furthermore, a nearly perfect fitting of the Langmuir model was obtained to the adsorption data, thereby suggesting the monolayer adsorption of RB5 dye onto the studied adsorbents. In the Dubinin–Radushkevich model, a good agreement of the calculated adsorption capacities to the experimental values were observed and the chemical adsorption of RB5 dye on to the studied adsorbents was proposed based on E (8 – 16 kJ mol−1).

Homogeneous photocatalytic degradation of azo dye Reactive Black 5 using Fe(III) ions under visible light

ABSTRACT Efficient and cost-effective method to destroy complex dyes is warranted to combat increasing water pollution. In the present study, homogeneous photocatalytic oxidation (PCO) of Reactive Black 5 (RB5) dye was studied using ferric ions (Fe(III)) under visible light (VL) irradiation and sunlight (SL). In the presence of 5 mM ferric ions and at pH 2.6, more than 80% of initial 20 mg/L RB5 was decolourized in 60 min under artificial VL. Decolourization followed pseudo first-order kinetics with the reaction rate constant 0.0356 min−1. 79% of initial COD was removed at the end of 60 min, suggesting mineralization of RB5 as the main cause of decolourization. Using similar experimental conditions under SL, more than 90% RB5 was decolourized in 15 min with an almost 10-fold increase in the reaction rate constant (0.34 min−1). Rate and extent of RB5 destruction significantly decreased in the presence of •OH scavenger indicating photoreduction of Fe-hydroxo species and generation of •OH as the main mechanism of RB5 degradation. RB5 removal increased from ca. 30% to 84% with the increase in Fe(III) concentration from 0.5 to 5 mM. The corresponding 1st-order rate constants increased linearly from 0.006 to 0.036 min−1. RB5 degradation decreased linearly (R2 = 0.98) from 91.7% to 63.3% with the increase in initial RB5 concentration from 10 to 40 mg/L. Fe(III) induced homogenous PCO appears to be a reliable and low-cost method of advanced oxidation without the need for costly reagent such as H2O2.

Adsorptive removal of anionic dye (Reactive Black 5) from aqueous solution using chemically modified banana peel powder: kinetic, isotherm, thermodynamic, and reusability studies

The removal of Reactive Black 5 (RB5) using chemically modified banana peel powder (CMBPP) from aqueous solution was dealt with in the present investigation. Factors affecting the adsorption of RB5 (like pH solution, agitation speed, initial concentration of RB5, contact time and temperature) were investigated. FTIR, SEM-EDX, BET and Elemental analysis characterized the adsorbent material. Adsorption kinetic results evaluated by non-linear pseudo-second-order model was fitted well and showed good correlation with the experimental data than the pseudo-first-order model. The experimental equilibrium data evaluated by non-linear Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Temkin equations and the experimental data were well described by the Langmuir isotherm model. Langmuir monolayer sorption capacity of RB5 onto CMBPP was observed at pH 3.0 (211.8 mg/g). The values of thermodynamic parameters revealed that the sorption process was feasible, spontaneous, endothermic, and physisorption in nature, i.e. (ΔG° <0, ΔH° > 0, and ΔS° > 0). Desorption studies reveal that the maximum recovery of RB5 when 0.1 M NaOH solution used as a desorbent. The CMBPP also exhibited excellent regeneration efficiency for the five cycles of successive adsorption–desorption. The results exposed that CMBPP could use as a prospective adsorbent material for the removal of RB5 from aqueous media.

Simultaneous removal of chromium(VI) and Reactive Black 5 using zeolite supported nano-scale zero-valent iron composite

Pollution due to heavy metals and dyes has become a major global environmental issue. Simultaneous removal of heavy metals and dyes from wastewater remains a major challenge. In this study, a zeolite supported nano-scale zero-valent iron (Z-nZVI) composite was innovatively used for the simultaneous removal of Cr(VI) and Reactive Black 5 from aqueous solution. Experiments were carried out at different pH values (2–8) and adsorbent dosages (0.2–1 g L−1). The maximum removal was found to be 99% for both Cr(VI) and Reactive Black 5 (RB5) at pH 3 with initial RB5 concentration 85 mg L−1, Cr(VI) concentration 23 mg L−1 and adsorbent dosage 1 g L−1. A Freundlich model showed a satisfactory fit to the equilibrium adsorption data of a Z-nZVI composite with a correlation coefficient R 2 = 0.9790 for RB5 and R 2 = 0.9726 for Cr(VI). The kinetics of adsorption followed a pseudo-first-order model. The results of the study indicated that a Z-nZVI composite could potentially be used for the simultaneous removal of metals and dyes from wastewater.

Promoting effect of ammonia modification on activated carbon catalyzed peroxymonosulfate oxidation

Abstract Ammonia modified cotton-based activated carbon (AC-NH3) was prepared and utilized to investigate the effect of ammonia modification on the chemical properties of activated carbon in catalyzed peroxymonosulfate (PMS) oxidation of aqueous organic pollutant. Activated carbons with and without modification were characterized by N2 adsorption/desorption, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Boehm titration, Fourier Transform Infrared Reflection (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Results indicated that ammonia modification has a promoting effect on the catalytic ability of AC in our system. And as small amount as 0.04 g/L AC-NH3 can efficiently activate PMS and subsequently degrade a model contaminant, Reactive Black 5 (RB5). Considering RB5 was barely removed by sole-AC-NH3 or sole-PMS, adsorption and catalytic oxidation have a significant synergistic effect in the combined AC-NH3/PMS system. With the XPS spectra deconvolution, we inferred that the π–π and pyrrolic functional groups resulted in the promoting catalytic ability of AC-NH3. However, the pyridine seems to play a nonsignificant role in our process. In addition, the parameters in the AC-NH3/PMS system, including the mole ratio of PMS to RB5, the dosage of AC-NH3, the initial concentration of RB5, initial pH, and the feeding method of PMS, were also discussed.

Resin-supported Fe(III) as an efficient heterogeneous Fenton catalyst for degradation of Reactive Black 5

AbstractIn this study, a resin-supported Fe(III) catalyst (Fe/R) was developed for the degradation of Reactive Black 5 (RB5) by a heterogeneous Fenton-like reaction. The catalyst stability was evaluated by measuring color removal efficiency for five successive cycles. The Fe/R samples were characterized by XRD, TGA, SEM-EDS, and FTIR techniques as well as physical properties were determined using the BET method. The effect of major parameters including pH, H2O2 concentration, catalyst addition, initial dye concentration, reaction temperature, and amount of hydroxyl radical scavenger (tert-butyl alcohol) on the decolorization of RB5 was investigated. The results indicated that the RB5 decolorization rate increased with increasing H2O2 concentration, reaction temperature, and Fe/R addition, but decreased with increasing initial RB5 concentration, pH, and amount of hydroxyl radical scavenger. The total organic carbon (TOC) removal of RB5 was only 48.6%, and more H2O2 was required for TOC further removal.

New low-cost nanoporous carbonaceous adsorbent developed from carob (Ceratonia siliqua) processing industry waste for the adsorption of anionic textile dye: Characterization, equilibrium and kinetic modeling

Carob (Ceratonia siliqua) processing industry waste (CW) has been applied as an abundant, cheap and available precursor to produce a new nanoporous carbon (CWNC) for removal of an anionic textile dye, Reactive Black 5 (RB5), which is frequently used in the textile industry, from aqueous phase. CWNC was characterized by BET, FTIR, SEM, and XRD techniques, proximate and ultimate analyses, Boehm titration method, pHpzc measurement, iodine and Methylene blue numbers. Its surface area, total pore volume, average pore diameter was found as 921.07m2g−1, 0.571cm3g−1 and 2.482nm, respectively. The influences on RB5 adsorption of various experimental factors such as adsorbent dose, solution pH, initial RB5 concentration, temperature and ionic strength were investigated. Adsorption kinetics was found to be best represented by the pseudo-second order model. The isotherm analysis indicated that the adsorption data could be represented by the Langmuir model. The maximum adsorption capacity for RB5 was 36.90mgg−1 at 50°C. Thermodynamic parameters showed that the process was spontaneous and endothermic.

Photocatalytic Degradation of Reactive Black-5 Dye with Novel Graphene-Titanium Nanotube Composite

Graphene-titanium nanotube composites with different ratios of graphite oxide were prepared via the hydrothermal method using ascorbic acid as a reducing agent. Properties of materials were characterized by X-ray diffraction, Fourier Transform Infrared Spectroscopy, high resolution transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The average diameter of the titanium dioxide nanotubes was about 8 nm. The photoresponse of nanocomposites have been extended to visible-light regions. In addition, graphene-titanium nanotube composites showed higher photocatalytic degradation efficiency for reactive black 5 (RBK5) than pure titanium dioxide and the 15%graphene-titanium nanotube composites catalysts possessed the best photocatalytic activity. The degradation efficiency for RBK5 dyes increased with increased dosage of graphite oxide from 3%-15% and decreased with increasing initial RBK5 concentration. This paper not only reports the fabrication of highly active photocatalysts but also provides insight into the photocatalytic mechanism of graphene-titanium nanotube composites.

Evaluation of Titanium dioxide photocatalytic technology for the treatment of reactive Black 5 dye in synthetic and real greywater effluents

Reuse of alternative water sources is gaining impetus as an acceptable integrated water resources management practice due to the scarcity of freshwater resources, particularly in urban centres where population is dense and freshwater supply is limited. This study investigated on the practical application of titanium dioxide (TiO2) photocatalytic treatment technology as a standalone system for the removal of Reactive Black 5 (RB5) dye, which usually causes a serious aesthetic problem that depresses the wider social acceptance of greywater recycling and reuse schemes. An optimization study was conducted on the photocatalytic degradation of RB5 dye in synthetic greywater effluent (i.e. aqueous RB5 in distilled water), in order to understand the effects of different photoreactor parameters on the degradation kinetics. It was found that the optimum photoreactor operating conditions are at TiO2 loading of 0.1 g/L, pH 5, initial RB5 concentration of 1 ppm and without compressed air sparging. Results showed that a 97% removal of RB5 was evident after 150 min of photocatalytic reaction in synthetic greywater effluent. With the established optimum photoreactor conditions, the photocatalytic degradation kinetics of RB5 dye in real greywater effluent was subsequently investigated. Results showed that the photocatalytic degradation of RB5 in real greywater effluent has a lower removal efficiency of 76% even after 330 min of reaction. It was hypothesized that the presence of other water pollutants in real greywater effluent could compete for the surface binding sites owing to the non-specific nature of TiO2 photocatalytic reaction. Thus, other greywater quality parameters such as oil and grease (O&G), chemical oxygen demand (COD), biological oxygen demand (BOD5), total nitrogen (TN) and total number of Escherichia coli were also monitored. Monitoring results showed that the parallel removal efficiencies of 60% O&G, 54% COD, 69% BOD5, 41% TN and 100% E. coli were evident, which have proven the impact of water impurities in real greywater effluent that could lower the photocatalytic degradation efficiency of RB5.

Decolorization of Reactive Black 5 by persulfate oxidation activated by ferrous ion and its optimization

We determined the effectiveness of persulfate (PS) activated by Fe2+ to treat Reactive Black 5 (RB5) dye. The experimental variables of persulfate dosage, Fe2+ dosage, initial dye concentration, solution pH, activators, and NaCl were investigated. The complete decolorization of RB5 by 200 mM PS activated by 1 mM Fe2+ was 100% within 12 h but the TOC removal efficiency was only 70% within 24 h. When the PS dosage and Fe2+ dosage increased, the kobs of RB5 decolorization increased. On the other hand, when the initial RB5 concentration increased from 0.01 to 0.05 mM and concentration of PS was fixed at 400 mM, the number of sulfate radicals did not increase proportionally, so the kobs of the RB5 decolorization decreased. Lowering the pH from 11 to 5 increased the kinetic rates of destruction of RB5. At a higher pH, the concentration of Fe2+ could decrease due to the formation of iron oxides which hinder the further reaction of Fe2+ with PS. Five activators (Fe0, Fe2+, Fe3+, Ag0, and Ag+) were chosen to study their capability in activating PS oxidation. At the equivalent mole of activator, the kobs of the treatment of PS activated by Fe0 was the best (2.8609 h−1). Increasing the NaCl concentration from 17.24 mM (1g L−1) to 68.96 mM (4 g L−1) decreased the kinetic removal rates of RB5. The PS oxidation of RB5 was optimized using response surface methodology. The interactive effects of three factors namely, persulfate dosage (X1), Fe2+ dosage (X2), and pH (X3) were investigated. The results indicated the optimum condition to treat 0.01 mM RB5 to be 445 mM PS and 4.91 mM Fe2+ at pH 5.45.