Simulated Dyebath Effluent Research Articles

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.

β-AgVO3 nanowires/TiO2 nanoparticles heterojunction assembly with improved visible light driven photocatalytic decomposition of hazardous pollutants and mechanism insight

In this report, novel β-AgVO3 nanowires/TiO2 nanoparticles heterojunction was synthesized first time using hydrothermal technique and employed for the photocatalytic decomposition of Rhodamine (RhB) dye, simulated dye-bath effluent and colourless compound i.e. ciprofloxacin (at natural pH) under visible light illumination. The prepared composite composed of β-AgVO3 nanowires over which the nanoparticles of TiO2 were distributed. The photocatalytic outcomes demonstrated that prepared β-AgVO3 nanowires/TiO2 nanoparticles heterojunction showed enhanced (93% degradation) catalytic properties for the decomposition of RhB dye under visible illumination in contrast to bare TiO2 (43%). Moreover, β-AgVO3/TiO2 exhibited 82% decomposition of simulated dye-bath effluent, signifying enough potential for treating industrial wastewater as well. Reactive species trapping experiments exhibited that OH and e− played pivotal role in the decomposition of RhB dye in aqueous phase. About 58% TOC drop in RhB solution (10 mg/L) was accomplished after 120 min of photocatalytic reaction. Further, the detailed mechanism for the decomposition of RhB dye was discussed.

Fabrication of novel carbon quantum dots modified bismuth oxide (α-Bi2O3/C-dots): Material properties and catalytic applications

The present work reports the facile and the template free sonochemical synthesis of a novel catalyst, α-Bi2O3/C-dots, for the degradation of indigo carmine (IC) dye, its simulated dyebath effluent and levofloxacin under visible light catalysis. The compositional, structural, optical and morphological analysis of α-Bi2O3/C-dots was studied using analytical, spectroscopic and microscopic techniques. X-ray diffraction (XRD) results confirmed the presence of a monoclinic phase of α-Bi2O3 in the nanocomposite and crystallite size of 28.75 nm. Photoluminescence (PL) and UV–vis diffuse reflectance spectra (UV-DRS) studies showed good optical properties and a band gap of 2.49 eV. The synthesized photocatalyst showed superior visible-light driven photocatalytic activity for the degradation of indigo carmine dye (86% dye degradation in 120 min) compared to pure α-Bi2O3 (57%). α-Bi2O3/C-dots also exhibited 79% degradation of antibiotic drug levofloxacin within 120 min, under optimized conditions of pH, catalyst dose and initial dye concentration. Scavenger studies revealed that hydroxyl radicals and electrons played predominant roles in the photocatalytic degradation of IC dye. With respect to total organic carbon (TOC) analysis, 68.8% total organic carbon reduction of the IC dye (10 mg/L) was observed under the same experimental conditions. The catalytic efficiency of C-dots in the photocatalytic process is explained by proposing a degradation mechanism.

Optimization of treatment efficiency of UV/H2O2 process on simulated textile industry wastewater

The present study involves optimization of UV/H2O2 process on a simulated dye bath effluent by varying initial H2O2 concentration, pollution load, and pH. The process was optimized by four factors and three levels of Box–Behnken design coupled with response surface methodology. During the experiment, color removal and degradation studies were also performed to ensure the treatment efficiency. The results obtained show that the color removal efficiency can be achieved within a short time due to the degradation of the structure which is more susceptible to oxidation. Then slower and gradual degradation of the simple and conjugated aromatic compounds takes place. In the first 5 min of the irradiation of the dyes, the pH value decreased from 11 to 9.5 and for another pH value decreased from 9 to 7.01. The drop in the pH value is mainly due to the formation of organic as well as inorganic acid as a degradation product. Under the optimum operating conditions such as pollution load of 64%, initial concentration of H2O2 0.6 M, initial pH 8, and treatment time of 81 min the predicted removal efficiencies are 98.77 and 86.11% for Color removal and COD removal, respectively.

Visible-light-driven photocatalytic properties of self assembled cauliflower-like AgCl/ZnO hierarchical nanostructures

Self assembled cauliflower-like AgCl/ZnO hierarchical nanostructures were successfully synthesized using template-free chemical method. The as-synthesized materials were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL). The characterization results revealed the formation of hierarchical AgCl/ZnO nanostructures with cauliflower-like morphology from the self assembly of 1D-nanorods. The photocatalytic activity of these hierarchical nanostructures was evaluated by the degradation of malachite green (MG) dye under visible light. As compared to other AgCl/ZnO nanostructures and bare ZnO, cauliflower like AgCl/ZnO hierarchical nanostructures (i.e., 30% AgCl/ZnO) exhibited higher photocatalytic activity upto 85% in 150min for the degradation of MG dye under visible light. Furthermore, the efficiency of 30% AgCl/ZnO was also investigated for the degradation of simulated dyebath effluent under solar light. A terephthalic acid-photoluminescence technique was used to detect OH radicals present in the photocatalytic process. LC–MS technique was also employed to identify the major intermediates in the photodegradation process of MG dye and the reaction pathway based on them was proposed.

α-Bi2O3 nanorods: An efficient sunlight active photocatalyst for degradation of Rhodamine B and 2,4,6-trichlorophenol

This paper reports the synthesis and characterization of an efficient sunlight active photocatalyst, i.e. α-Bi2O3 nanorods for the photocatalytic degradation of Rhodamine B and 2,4,6-trichlorophenol. The α-Bi2O3 nanorods were synthesized by a simple surfactant free sono-chemical route at ambient conditions and characterized in detail in terms of their morphological, structural, compositional and optical properties. The detailed characterizations revealed that the prepared nanorods exhibited high purity, well-crystalline monoclinic α-Bi2O3 structure and excellent optical properties. The catalytic behaviour of α-Bi2O3 was investigated for the degradation of a cationic dye (Rhodamine B), its simulated dye bath effluent and 2,4,6-trichlorophenol under solar light irradiation. The as-synthesized α-Bi2O3 nanorods catalyst exhibited excellent solar-light driven photocatalysis towards Rhodamine B (97% dye degradation in 45min) and 2,4,6-trichlorophenol (88% dye degradation in 180min). The presented results demonstrate that α-Bi2O3 nanorods are excellent solar-light driven photocatalyst for the photocatalyst degradation of organic dyes and pollutants.

CeO2[sbnd]ZnO hexagonal nanodisks: Efficient material for the degradation of direct blue 15 dye and its simulated dye bath effluent under solar light

Well-crystalline CeO2ZnO hexagonal nanodisks were synthesized by simple and facile chemical reaction process at low-temperature and characterized in detail by using several techniques such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) emission spectroscopy and X-ray photoelectron spectroscopy (XPS). The detailed characterizations results revealed that the prepared samples are well-crystalline with good optical and structural properties and possessing hexagonal morphologies. Further, the prepared material was used as efficient photocatalyst for the photocatalytic degradation of highly hazardous direct blue (DB)-15 dye under solar light irradiation. The CeO2ZnO hexagonal nanodisks exhibited superior photocatalytic performance towards the degradation of DB 15 dye and its simulated dye bath effluent under solar light. The enhanced photocatalytic activity of CeO2ZnO hexagonal nanodisks could be attributed to the suppression of photo-induced e−/h+ pair recombination. Moreover, various scavengers have been used to study the role of reactive species in the photo-degradation process.

Preparation, Characterization and Photocatalytic Activity of Nanosized ZnO for the Degradation of Rhodamine B Dye and Simulated Dyebath Effluent

Preparation, Characterization and Photocatalytic Activity of Nanosized ZnO for the Degradation of Rhodamine B Dye and Simulated Dyebath Effluent

Preparation of char from lotus seed biomass and the exploration of its dye removal capacity through batch and column adsorption studies

Char was obtained from lotus seed biomass by a simple single-step acid treatment process. It was used as an adsorbent for the removal of malachite green dye (MG) from simulated dye bath effluent. The adsorbent was characterized for its surface morphology, surface functionalities, and zero point charge. Batch studies were carried out by varying the parameters such as initial aqueous pH, adsorbent dosage, adsorbent particle size, and initial adsorbate concentration. Langmuir and Freundlich isotherms were used to test the isotherm data and the Freundlich isotherm best fitted the data. Thermodynamic studies were carried out and the thermodynamic parameters such as ∆G, ∆H, and ∆S were evaluated. Adsorption kinetics was carried out and the data were tested with pseudofirst-order model, pseudosecond-order model, and intraparticle diffusion model. Adsorption of MG was not solely by intraparticle diffusion but film diffusion also played a major role. Continuous column experiments were also conducted using microcolumn and the spent adsorbent was regenerated using ethanol and was repeatedly used for three cycles in the column to determine the reusability of the regenerated adsorbent. The column data were modeled with the modeling equations such as Adam-Bohart model, Bed Depth Service Time (BDST) model, and Yoon-Nelson model for all the three cycles.

Synthesis of flower like zinc oxide nanostructure and its application as a photocatalyst

In the present study a flower like ZnO nanostructure has been synthesized by using simple hydrothermal route without any catalysts, templates or substrates. The phase structure and morphology of the synthesized ZnO has been characterized by XRD, SEM and TEM. The room temperature photoluminescence (PL), diffuse reflectance spectra (DRS), FT-IR spectra and BET surface area have also been examined. Furthermore the application of the prepared ZnO as a photocatalyst was investigated for the decolorization of pararosaniline chloride dye and its simulated dyebath effluent. Finally the comparison of photocatalytic activity of commercial and synthesized ZnO has been made. Experiments were also performed to investigate the reusability and stability of the synthesized ZnO.

Studies on the photocatalytic decolorization of pararosanilne chloride dye and its simulated dyebath effluent

In the present study the photocatalytic decolorization of pararosaniline chloride dye (unhydrolysed and hydrolysed forms) and its simulated dyebath effluent has been investigated by employing heterogeneous photocatalysis process. The photocatalytic activity of different semiconductors viz. TiO2, ZnO, CdS and ZnS has been compared in order to select the most active catalyst for the decolorization of this dye. It was observed that ZnO exhibits better photocatalytic activity than the others. Thereafter different operational parameters which affect the decolorization process like catalyst dose, pH, initial dye concentration have been optimized. The maximum decolorization of the dye solutions was noticed in alkaline conditions and the optimum value of catalyst dose was found to be 1 g L–1. Further the study has been extended to explore the applicability of this system for the decolorization of the dye in its hydrolysed form and simulated dyebath effluent. The decolorization rate as well as chemical oxygen dema...

Degradation of Remazol Black B dye and its simulated dyebath wastewater by advanced oxidation processes in heterogeneous and homogeneous media

This study focused on the degradation of hydrolysed Remazol Black B (CI Reactive Black 5), a common diazo reactive dye, in aqueous solution. In the presence of various dye auxiliary chemicals a typical Remazol Black exhausted dyebath liquor simulated, which was then treated with homogeneous [ozonation with hydroxy ions, and Fe(II) or Fe(III) with hydrogen peroxide] and heterogeneous (titanium dioxide with UV‐A irradiation) advanced oxidation processes. Treatment performance of the investigated advanced oxidation systems was comparatively assessed in terms of the environmental sum parameters total organic carbon, biochemical oxygen demand and spectrophotometric measurements. The results obtained clearly reveal that the investigated advanced oxidation processes are capable of completely decolourising and partially mineralising the dye solution and its simulated dyebath effluent under predetermined reaction conditions. During the application of alkaline ozonation at an ozone dose of 2340 mg/ml, a three‐fold biodegradability enhancement was observed.