Phosphorylated chitosan (P-CS) was successfully synthesized using a facile experimental setup of hydrothermal method that was applied to the adsorption of anionic Acid Red 88 (AR88) from aqueous media. The adsorption process obeyed the pseudo-second-order (PSO) kinetic model. In contrast, the adsorption isotherm conformed to the Langmuir model, with the maximum adsorption capacity (qm = 230 mg g-1) at 303 K. Both external and intraparticle diffusion strongly influenced the rate of adsorption. The insights from this study reveal that P-CS could be easily prepared and regenerated for reusability applications. The adsorption mechanism and intermolecular interaction between P-CS and AR 88 were investigated using Fourier transform infrared (FTIR) spectroscopy and calculations via Density Functional Theory (DFT). The key modes of adsorption for the P-CS/AR 88 system are driven by electrostatic attractions, H-bonding, and n-π interactions. The findings herein reveal that P-CS is a promising adsorbent for the removal of anionic dyes such as AR88 or similar pollutants from water.
Trichoderma asperellum (Ta) was first cultured in synthetic medium (Potato Dextrose Broth, PDB) of various concentrations (100, 75, 50, 25%). The biomass was harvested and inoculated into dye solutions (crystal violet, CV; methyl violet, MV; malachite green, MG; and cotton blue, CB). Reduced concentrations (20, 50, 75%) affected growth rate but their decolourization efficacies remained unaffected. This was attributed to similar numbers and types of functional groups (hydroxyl, amine, ester-lipid, alkane groups) found on the surface of fungal biomass, as revealed by the Fourier transformed infrared spectroscopy (FTIR) analysis. Their production of NADH-reductase for degradation, and their biosorption activities were also unaffected. In general, Ta cultured in reduced concentrations (20, 50, 75%) retained the ability to perform biosorption and biodegradation, similar to cultures from control (100% PDB). This suggested that reduced nutrient levels (as a cost-feasible strategy) could be used to cultivate biomass of Ta for dye removal activities.
Bioremediation of heavy metals and dyes is one of the emerging techniques globally as it is evident from the numerous publications made by various research groups. Biofilm-assisted bioremediation is one of the trending approaches as it facilitates negatively charged extracellular polymeric substances which makes the bacteria resistant to the toxic chemicals. Genetic engineering of microbes will make them unique in the bioremediation process. This mini-review concentrates on source and toxic effects of heavy metals and dyes on aqueous and living beings. Further, the genetic improvement strategies for effective bioremediation are described. However, the gap between practicability and real-time applicability needs to test with real-time wastewater in the industrial scale.
We demonstrate a green chemistry approach to synthesize narrow-sized zerovalent iron (nZVI) nanoparticles using Artocarpus heterophyllus Lam. leaf extract as reducing and capping agent. The produced nZVI was characterized by various instrumental methods including ultraviolet-visible spectra, transmission electron microscopy, vibrating sample magnetometer (VSM), X-ray diffraction, and Fourier transform infrared spectroscopy. Based on the electron microscopy observations, the particle size was estimated to be ∼30 nm. In VSM, the saturation point of magnetization was observed to be 0.6 emu g-1 under a magnetic field of 0 ± 30 kOe. The synthesized nZVI was amorphous in nature as per the XRD results. The catalytic activity of the nZVI was employed for the catalytic reduction of 4-nitrophenol (4-NP) and decoloration of textile dyes such as methylene blue, methyl orange, and malachite green, respectively. The proposed nZVI synthesis method exhibited better catalytic performance toward reduction of 4-NP and degradation of dyes within 4 min for 0.1 mg of catalyst. Moreover, the synthesized catalyst nZVI can be recoverable and reutilized in many cycles without loss of its significant catalytic activity. The synthesized nZVI could be a promising material to treat industrial wastewater via profitable, sustainable, and ecofriendly approaches.
Semiconductor metal oxide with TiO2 nanoparticles removes hazardous compounds from environmental samples. TiO2 nanoparticles have shown potential as an efficient photocatalyst by being employed as a nano-catalyst for the breakdown of organic contaminants in wastewater samples. To separate substances from contaminated samples, combined UV and visible light irradiation has been used. Sol-gel synthesis was used to produce a copper chromite-titanium nanocomposite, which was then evaluated using analytical methods, such as XRD, BET, DRS-UV, and FT-IR. Using visible light, the photocatalytic activity of a nanocomposite made of CuCr2O4 and TiO2 was investigated for its role in the breakdown of malachite green. The effects of several parameters, including pH change, anions presence, contact time, catalyst amount, concentration variation, and the kinetics of photocatalytic degradation were investigated. The magnitude of transition energy calculated using UV-DRS spectra was found to be 3.1 eV for CuCr2O4-TiO2 nanocomposite. Maximum degradation was observed at pH 7.0. The surface area and pore volume of the co-doped samples of Cr2O4 - TiO2 obtained from BET were found to be 6.1213 m2/g and 0.045063 cm3/g respectively. The average particle size of the catalyst of the nano-catalysts calculated from XRD was found to be 8 nm for TiO2 and 66 nm for TiO2-CuCrO4. The peaks obtained in FTIR between the range of 900-500 cm-1 were due to the presence of an aromatic compound. The binding mechanism of a dye molecule to the surface of CuCr2O4-TiO2 nanocomposite was analysed using quantum chemical calculations with the self-consistent reaction field technique employing integral equation formalism for the polarized continuum method and the UFF atomic radii set.
Azo dyes are the most varied class of synthetic chemicals with non-degradable characteristics. They are complex compounds made up of many different parts. It was primarily utilized for various application procedures in the dyeing industry. Therefore, it's crucial to develop an economical and environmentally friendly approach to treating azo dyes. Our present investigation is an integrated approach to the electrooxidation (EO) process of azo dyes using RuO2-IrO2-TiO2 (anode) and titanium mesh (cathode) electrodes, followed by the biodegradation process (BD) of the treated EO dyes. Chemical oxygen demand (COD) removal efficiency as follows MB (55%) ≥ MR (45%) ≥ TB (38%) ≥ CR (37%) correspondingly. The fragment generated during the degradation process which was identified with high-resolution mass spectrometry (HRMS) and its degradation mechanism pathway was proposed as demethylation reaction and N-N and C-N/C-S cleavage reaction occurs during EO. In biodegradation studies by Aeromonas hydrophila AR1, the EO treated dyes were completely mineralized aerobically which was evident by the COD removal efficiency as MB (98%) ≥ MR (92.9%) ≥ TB (88%) ≥ CR (87%) respectively. The EO process of dyes produced intermediate components with lower molecular weights, which was effectively utilized by the Aeromonas hydrophila AR1 and resulted in higher degradation efficiency 98%. We reported the significance of the enhanced approach of electrochemical oxidation with biodegradation studies in the effective removal of the pollutants in dye industrial effluent contaminated water environment.
In this study, a magnetic chitosan grafted-benzaldehyde (CS-BD/Fe3O4) was hydrothermally prepared using benzaldehyde as a grafting agent to produce a promising adsorbent for the removal of acid red 88 (AR88) dye. The CS-BD/Fe3O4 was characterized by infrared spectroscopy, surface area analysis, scanning electron microscopy-energy dispersive X-ray, vibrating sample magnetometry, powder X-ray diffraction, CHN elemental analysis, and point of zero charge (pHPZC). The Box-Behnken design (BBD) was adopted to study the role of variables that influence AR88 dye adsorption (A: CS-BD/Fe3O4 dose (0.02-0.1 g), B: pH (4-10), and time C: (10-90 min)). The ANOVA results of the BBD model indicated that the F-value for the AR88 removal was 22.19 %, with the corresponding p-value of 0.0002. The adsorption profiles at equilibrium and dynamic conditions reveal that the Temkin model and the pseudo-first-order kinetics model provide an adequate description of the isotherm results, where the maximum adsorption capacity (qmax) with the AR88 dye was 154.1 mg/g. Several mechanisms, including electrostatic attraction, n-π interaction, π-π interaction, and hydrogen bonding, regulate the adsorption of AR88 dyes onto the CS-BD/Fe3O4 surface. As a result, this research indicates that CS-BD/Fe3O4 can be utilized as an effective and promising bio-adsorbent for azo dye removal from contaminated wastewater.
Several water and wastewater technologies have been implored for the removal of dyes during wastewater treatments; however; different types have been reportedly found in surface and groundwater systems. Hence, there is a need to investigate other water treatment technologies for the complete remediation of dyes in aquatic environments. In this study, novel chitosan-based polymer inclusion membranes (PIMs) were synthesized for the removal of malachite green dye (MG) which is a recalcitrant of great concern in water. Two types of PIMs were synthesized in this study, the first PIM (PIMs-A) was composed of chitosan, bis-(2-ethylhexyl) phosphate (B2EHP), and dioctyl phthalate (DOP). While, the second PIMs (PIMs-B) were composed of chitosan, Aliquat 336, and DOP. The physico-thermal stability of the PIMs was investigated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), both PIMs demonstrated good stability with a weak intermolecular force of attraction amongst the various components of the membranes. The effects of the initial concentration of MG, pH of the MG solution, stripping solution, and time were investigated. At optimum conditions, both membranes (PIM-A and B) recorded the highest efficiencies of 96 % and 98 % at pH 4 and initial contaminants concentration of 50 mg/L, respectively. Finally, both PIMs were used for the removal of MG in different environmental samples (river water, seawater, and tap water) with an average removal efficiency of 90 %. Thus, the investigated PIMs can be considered a potential suitable technique for the removal of dyes and other contaminants from aquatic matrices.
This study investigates the effects of stirring duration on the synthesis of graphene oxide (GO) using an improved Hummers' method. Various samples are examined under different stirring durations (20, 40, 60, 72, and 80 h). The synthesized GO samples are evaluated through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The GO sample with 72 h stirring duration (GO72) has the highest d-spacing in the XRD results, highest atomic percentage of oxygen in EDX (49.57%), highest intensity of oxygen functional group in FTIR spectra, and highest intensity ratio in Raman analysis (ID/IG = 0.756). Results show that GO72 with continuous stirring has the highest degree of oxidation among other samples. Electrochemical impedance spectroscopy analysis shows that GO72-titanium dioxide (TiO2) exhibits smaller charge transfer resistance and higher electron lifetime compared with the TiO2-based photoanode. The GO72 sample incorporating TiO2 nanocomposites achieves 6.25% photoconversion efficiency, indicating an increase of more than twice than that of the mesoporous TiO2 sample. This condition is fully attributed to the efficient absorption rate of nanocomposites and the reduction of the recombination rate of TiO2 by GO in dye-sensitized solar cells.
In recent years, loop-mediated isothermal amplification (LAMP) has gained popularity for detecting various pathogen-specific genes due to its superior sensitivity and specificity compared to conventional polymerase chain reaction (PCR). The simplicity and flexibility of naked-eye detection of the amplicon make LAMP an ideal rapid and straightforward diagnostic tool, especially in resource-limited laboratories. Colorimetric detection is one of the simplest and most straightforward among all detection methods. This review will explore various colorimetric dyes used in LAMP techniques, examining their reaction mechanisms, advantages, limitations and latest applications.
Correction for 'Functionalized fluorescent terephthalate monomers and their attempted polyester formation' by Yvonne S. L. Choo et al., Org. Biomol. Chem., 2020, 18, 8735-8745, DOI: 10.1039/D0OB01533D.
In this work, the photocatalytic property of p-type CuO was tailored by creating a heterojunction with n-type CdS. The CuO/CdS nanocomposite photocatalyst was synthesized by the ultrasound-assisted-wet-impregnation method and the physicochemical and optical properties of the catalysts were evaluated by using N2 physisorption, X-Ray Diffraction (XRD),X-Ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, Transmission electron microscopy (TEM), Energy dispersive X-Ray (EDX) mapping, Field Emission Scanning Electron Microscope (FE-SEM), UV-Vis and photoluminescence spectroscopy experiments. Detailed characterization revealed the formation of a nanocomposite with a remarkable improvement in the charge carrier (electron/hole) separation. The photocatalytic degradation efficiencies of CuO and CuO/CdS were investigated for different dyes, for instance, rhodamine B (RhB), methylene blue (MLB), methyl blue (MB) and methyl orange (MO) under visible light irradiation. The obtained dye degradation efficiencies were ~93%, ~75%, ~83% and ~80%, respectively. The quantum yield for RhB degradation under visible light was 6.5 × 10-5. Reusability tests revealed that the CuO/CdS photocatalyst was recyclable up to four times. The possible mechanisms for the photocatalytic dye degradation over CuO/CdS nanocomposite were elucidated by utilizing various scavengers. Through these studies, it can be confirmed that the conduction band edges of CuO and CdS play a significant role in producing O2-. The produced O2- degraded the dye molecules in the bulk solution whereas the valence band position of CuO acted as the water oxidation site. In conclusion, the incorporation of CuO with CdS was demonstrated to be a viable strategy for the efficient photocatalytic degradation of dyes in aqueous solutions.
3-Nitro-2-phenoxypyridine and 3-nitro-2-(4-methyl)phenoxypyridine were obtained when 2-chloro-3-nitropyridine was treated with phenol and p-cresol, respectively. Fluorescence studies were carried out in various solvents, in capped and uncapped conditions and for differing concentrations. Both 3-nitro-2-phenoxypyridine and 3-nitro-2-(4-methyl)phenoxypyridine were fluorescent compounds but 3-Nitro-2-(4-methyl)phenoxypyridine was more fluorescent than 3-nitro-2-phenoxypyridine in all the solvents used. The fluorescence intensity decreased with concentration and time.
The development of Transparent Solar Cells (TSC) has become the main focus of solar energy research in recent years. The TSC has a number of applications and make use of unexploited space such as skyscraper windows. In this paper, TSC is fabricated using commercially available titanium dioxide (TiO2) P25 to make a paste, which is deposited on FTO glass using screen printing and spin coating methods. The effects of the thickness of the TiO2 film on transparency are examined. The paste is synthesised in the Cleanroom and used in both methods of deposition. The final cell fabrication is a Dye sensitised solar cell (DSSC). The obtained transparency of the FTO glass is 83%, and after the deposition of TiO2 it is reduced to less than 80%. The overall transparency of the DSSC, which was made using the spin coating method, is 70% with an Isc of 9.5 mA and Voc 853mV.
In the present work, two-dimensional bismuth oxybromide (BiOBr) was synthesized and coupled with co-catalyst molybdenum disulphide (MoS2) via a simple hydrothermal process. The photoactivity of the resulting hybrid photocatalyst (MoS2/BiOBr) was evaluated under the irradiation of 15 W energy-saving light bulb at ambient condition using Reactive Black 5 (RB5) as model dye solution. The photo-degradation of RB5 by BiOBr loaded with 0.2 wt% MoS2 (MoBi-2) exhibited more than 1.4 and 5.0 folds of enhancement over pristine BiOBr and titanium dioxide (Degussa, P25), respectively. The increased photocatalytic performance was a result of an efficient migration of excited electrons from BiOBr to MoS2, prolonging the electron-hole pairs recombination rate. A possible charge transfer diagram of this hybrid composite photocatalyst, and the reaction mechanism for the photodegradation of RB5 were proposed.
The decolorization of reactive orange 16 dye (RO16) from aqueous solution by CuO/H2O2 was investigated. The amount of dye removed was determined by measuring the concentration of the dye at its characteristic wavelengths by UV-Vis spectrophotometer. The effects of CuO dose, H2O2 concentration and UV light on the decolorization of the dye were investigated. It was found that the removal rate increased with increasing mass of CuO and increasing concentration of H2O2. The combination of CuO, H2O2 and UV light was the best system with dye removal of 100% after 6 h. The removal efficiency observed was in the order: CuO/UV/H2O2 > CuO/H2O2 > CuO/UV = CuO > UV/H2O2 > H2O2 > UV.
The water sources contaminated by toxic dyes would pose a serious problem for public health. In view of this, the development of a simple yet effective method for removing dyes from industrial effluent has attracted interest from researchers. In the present work, flat sheet mixed matrix membranes (MMMs) with different physiochemical properties were fabricated by blending P84 polyimide with different concentrations of cadmium-based metal organic frameworks (MOF-2(Cd)). The resultant membranes were then used for simultaneous removal of eosin y (EY), sunset yellow (SY) and methylene blue (MB) under various process conditions. The findings indicated that the membranes could achieve high water permeability (117.8-171.4 L/m2.h.bar) and promising rejection for simultaneous dyes removal, recording value of 99.9%, 81.2% and 68.4% for MB, EY and SY, respectively. When 0.2 wt% MOF-2(Cd) was incorporated into the membrane matrix, the membrane separation efficiency was improved by 110.2% and 213.3% for EY and SY removal, respectively when compared with the pristine membrane. In addition, the optimization and modeling of membrane permeate flux and dye rejection was explored using response surface methodology. The actual and model results are in good agreement with R2 of at least 0.9983 for dye rejection and permeate flux. The high flux of the developed MMMs coupled with effective separation of dyes suggests a promising prospect of using P84 polyimide MMMs incorporated with MOF-2(Cd) for water purification.
Dye-Sensitized Solar Cells (DSSCs) have attracted great attention due to environmentally friendly low-cost processing, excellent working ability in diffuse light, and potential to meet the power demands of future buildings due the true class of building integrated photovoltaics (BIPV). Nevertheless, DSSCs have relatively low photoconversion efficiency (PCE) due to multiple issues. Several strategies have been employed to enhance its PCE. For instance, bi-layered structure of photoelectrode i.e., mesoporous TiO2 transparent layer with top scattering layer was introduced which scatter light inside on large angles improves the harvesting ability of photoelectrode thus enhanced PCE. However, scattering layer is composed of aggregated small particles which offer sluggish electron transport due to multiple grain boundaries, consequently, unwanted recombination reaction which leads to poor PCE. This issue has been addressed for transparent layer immensely but ignored for scattering layer. Mostly for scattering layer in previous studies novel structures have been proposed to enhance scattering properties and dye adsorption only. Therefore, in this study for the first time presenting dual functional graphene/TiO2 scattering layer in which solvent exfoliated graphene is incorporated in TiO2 submicron spheres which enhanced electron transport properties, while submicron spheres scatter light effectively. Scattering and electron transport characteristics of DSSCs are thoroughly investigated with the function of graphene loading. Electrochemical impedance spectroscopy (EIS) has revealed that diffusion coefficient length and coefficient and conductivity attained maximum value at 0.01 wt%. while other important parameters such as electron lifetime and electron density in conduction band have been improved till 0.020 wt% graphene loading. However, results indicated that with 0.01 w% graphene 33% higher PCE was achieved than without scattering layer and 13% higher than scattering layer without graphene. The depraving in PCE at >0.01 wt% graphene despite of excellent electron transport improvement is attributed to the loss of diffuse reflectance and higher optical absorption by graphene.
The feasibility and performance of Jicama peroxidase (JP) immobilized Buckypaper/polyvinyl alcohol (BP/PVA) membrane for methylene blue (MB) dye removal was investigated in a customized multi-stage filtration column under batch recycle mode. The effect of independent variables, such as influent flow rate, ratio of H2O2/MB dye concentration, and contact time on the dye removal efficiency, were investigated using response surface methodology (RSM). To capture the inherent characteristics and better predict the removal efficiency, a data-driven adaptive neuro-fuzzy inference system (ANFIS) is implemented. Results indicated that the optimum dye removal efficiency of 99.7% was achieved at a flow rate of 2 mL/min, 75:1 ratio of H2O2/dye concentration with contact time of 183 min. The model predictions of ANFIS are significantly good compared with RSM, thus resulting in R2 values of 0.9912 and 0.9775, respectively. The enzymatic kinetic parameters, Km and Vmax, were evaluated, which are 1.98 mg/L and 0.0219 mg/L/min, respectively. Results showed that JP-immobilized BP/PVA nanocomposite membrane can be promising and cost-effective biotechnology for the practical application in the treatment of industrial dye effluents.
A novel titanium dioxide/activated carbon (TiO2/AC) composite where AC derived from oil palm empty fruit bunch (EFB) was synthesised by using sol-gel method. All the samples were characterised by using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), Fourier transformed infrared (FTIR), thermogravimetric analysis (TGA) and surface analyser. SEM analysis showed that TiO2 particles were successfully embedded and well distributed on the AC surface. The elemental composition analysis found that the TiO2/AC composite contained titanium (Ti), oxygen (O) and carbon (C) atoms. Meanwhile, the appearance of new band at about 960 cm-1 which assigned to the Ti-O stretching was observed in the FTIR spectra when the AC was incorporated into TiO2. TGA analysis showed that the weight loss of 32 wt.% from 150 to 550 °C was due to the decomposition of amorphous carbon layers and loss of hydroxyl groups on TiO2. It was found that the TiO2/AC composite had better performance in the sonocatalytic degradation of malachite green as compared to the individual AC and TiO2 because the TiO2/AC composite had dual functionality and huge number of active sites which could promote the mass transfer of dye molecules towards catalyst surface. By using 1.5 g/L of TiO2/AC composite which calcined at 700 °C on 100 mL of 200 mg/L of malachite green at solution pH of 7, a degradation efficiency of 87.11% had been achieved after 30 min of ultrasonic irradiation. A lower chemical oxygen demand (COD) removal (81.75%) was observed because the structured dye molecules underwent mineralisation process during the sonocatalytic degradation to generate intermediate compounds. The TiO2/AC composite was able to be recycled and still achieved a high degradation efficiency of 76.78% after second catalytic cycle as compared to the fresh TiO2/AC composite with degradation efficiency of 87.11%. In conclusion, the TiO2/AC composite had high reusability and promising for practical applications in textile industry.