Titanium dioxide nanoparticles were synthesized by using sol gel method and their physico-chemical properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer. The photocatalytic property of TiO2 nanoparticles was investigated by inactivation of Escherichia coli under irradiation of fluorescent lamp. The results showed that the size of TiO2 was in the range of 3 to 7 nm with high crystallinity of anatase phase. The sharp peaks in FTIR spectrum determined the purity of TiO2 nanoparticles and absorbance peak of UV-Vis spectrum showed the energy band gap of 3.2 eV. Optimum inactivation of E. coli was obtained at 1.0 g/L TiO2 nanoparticles, with 80% of E. coli population was inactivated. The light scattering effect and insufficient concentration are the factors that cause the less effective inactivation reaction for 2.5 g/L and 0.1 g/L TiO2 concentration.
The crab carapace is a waste which cannot be decomposed. This waste was used to
remove the Reactive Orange 16 (RO16) and Basic Blue 3 (BB3) from aqueous solution
at different operational parameters such as pH, mass load, the concentrations of dye and
the temperature. The crab collected was modified to obtain quaternized crab (QC) using
(3-chloro-2-hydroxypropyl) trimethylammonium chloride solution (C6H15Cl2NO, 65% w/w
in water). The pH of the dyes solution was varied from pH 4 to 10. The highest adsorption
percentage was achieved at pH 7 for both dyes. Increasing the QC mass for the adsorption
process had granted an increase of dyes removal percentage. The highest adsorption
percentage was achieved at 91.00% for RO16 and 29.40% for BB3 dyes with 7.5 g/L QC
used. However, the adsorption capacity of QC decreased with higher QC mass because the
dye molecules occupied on the surface and prevented other molecules to diffuse into the
QC. At higher concentration beyond 20 mg/L and 10 mg/L of RO16 and BB3, respectively,
the maximum adsorption was achieved at 2.5362 mg/g and 0.6812 mg/g. The adsorption of
both dyes by QC was best fitted using Langmuir isotherm model, explaining the adsorption
mainly occurred as a single layer on the surface of QC. Comparison to the results obtained
from the kinetic models, the adsorption was
chemisorption in nature. According to the
thermodynamic studies, the adsorption of
RO16 was an exothermic, while BB3 was
an endorthermic process.
Currently, heavy metals and dyes are some of the most critical pollutants in the aquatic environment. So, in this paper "waste-to-resource conversion", as a new application of modified mine silicate waste to remove Pb2+ ion and methylene blue (MB) dye, adsorption properties, mechanism of action and recycling were studied. Silicate wastes are located in the alteration zone and the margin of molybdenum ore, these wastes are under the influence of hydrothermal solutions which are impregnated with iron and manganese ions. Hence, acid and base modifications have been commonly used. So, in this study, a highly porous nanostructure of modified silicate waste was used to remove MB and Pb2+ ion, in subsequent to our previous study on the application of the raw material of the same in the removal of malachite green. Acid, base, and acid/base treatments were used to activate and modify the adsorbent. Results show a significantly higher potential of modified adsorbent in the removal of MB and Pb2+ compared to the raw material. According to the isotherm and kinetic studies for MB and Pb2+ the Langmuir and Temkin and pseudo-second-order models were investigated with experimental data. Modified nanomaterial was used for several adsorption and desorption processes, without a significant decrease in the capability of the adsorbent in the removal of MB and Pb2+ pollutants. Leached iron and manganese ions (as production of modification) are deposited in the form of sludge using a simple pH adjustment and precipitation process and can be used to recover iron and manganese metals in the long run. The comparison of monolayer adsorption capacity using for Pb2+ ion and MB dye are as ((untreated SW: 29.41, 1.05); (NaOH treated: 21.74, 100); (Nitric Acid treated: 16.67, 142.86); (Citric Acid treated: 40, 125); (Nitric/Citric Acids treated: 15.63, 111.11) and (Nitric/Citric Acids/NaOH treated: 15.15, 83.33)), respectively. Higher adsorption capacity and re-generable properties of this adsorbent suggest the usage of this natural and abundant mine waste to treat wastewater containing toxic elements and dyes.
Rhodamine B (RhB) is among the toxic dyes due to the carcinogenic, neurotoxic effects and ability to cause several diseases for humans. The adsorption with agricultural waste adsorbent recorded high performance for the RhB removal. The current review aimed to explore the efficiency of different adsorbents which have been used in the few last years for removing RhB dye from wastewater. The data of adsorption of RhB using agricultural wastes were collected from the Scopus database in the period between 2015 and 2021. The use of agricultural wastes and adsorbents as a replacement for the activated has received high attention among researchers. The RhB removal methods by microbial enzymes and biomass occurred between 76 and 90.1%. In comparison, the adsorption with agricultural wastes such as activated carbon white sugar reached 98% within 12 min. The adsorption process has a wide range of pH (3-10) due to the zwitterionic forms of RhB. Gmelina aborea leaf activated carbon is among the agriculture wastes absorbents that exhibited 1000 mg g-1 of the adsorption capacity. It appeared that the agricultural wastes adsorbents have a high potential for removing RhB from the wastewater.
Mesoporous activated carbon was prepared using a hydrochar derived from coconut shell waste through hydrothermal carbonization and NaOH chemical activation process (COSHTC). Three sets of activated carbons were obtained with different hydrochar:NaOH impregnation ratios (1:1, 1:2, and 1:3). Among these ratios, 1:3 (COSHTC3) exhibited the optimum adsorption for methylene blue (MB). COSHTC3 adsorbed MB with an initial concentration of 25-250 mg/L at pH 3-11 and 30 °C. The adsorption isotherm of MB on COSHTC3 demonstrated that Langmuir isotherm could be better applied at a maximum monolayer adsorption capacity of 200.01 mg/g at 30 °C. The data was well fitted to the pseudo-second-order (PSO) kinetic model. These results show that the COSHTC3 prepared from low-cost agricultural waste (coconut shell) with average pore diameter 28.6 Å and surface area 876.14 m(2)/g acts as a better adsorbent for removal of cationic dyes and could pave the way for more low-cost adsorbents for dye removal.
There are many factors influencing the stability and color variation of natural colorant anthocyanin and pH is among the most significant factor. This study aims to determine the stability of the anthocyanins in freeze-dried Hibiscus sabdariffa, Melastoma malabathricum and Ipomoea batatas in various acidic pH (pH 2.0, 2.5, 3.0, 3.5, 4.0 and 4.5). Total monomeric anthocyanin, degradation index, color density and percent polymeric color were analyzed to determine anthocyanins degradation and their color variations. Among the samples, H.sabdariffa contain the highest monomeric anthocyanins (163.3 mg/L) followed by M. malabathricum (49.9 mg/L) and the lowest is I.batatas (13.8 mg/L). Monomeric anthocyanins from I.batatas were found to be very stable and not affected by changes in pH than in H. sabdariffa and M. malabathricum. However, degradation index (DI) of H. sabdariffa was the lowest with value of 0.365 ± 0.049 at pH 3.5. The lowest percentage of polymeric color (4.94 ± 0.64) was also shown by H. sabdariffa at pH 2.5 and maintained a deep red color with increasing pH indicating higher color stability compared to M. malabathricum and I. batatas. Overall, natural pigment in H. sabdariffa was found to be the most stable in both monomeric anthocyanin content and chromaticity properties. These results provided information that will further proven the potential usage of H. sabdariffa, M. malabathricum and I. batatas as natural coloring agents to replace the synthetic colorant in food and beverage industries.
Monoazo and diazo dyes [New coccine (NC), Acid orange 7 (AO7), Reactive red 120 (RR120) and Reactive green 19 (RG19)] were employed as electron acceptors in the abiotic cathode of microbial fuel cell. The electrons and protons generated from microbial organic oxidation at the anode which were utilized for electrochemical azo dye reduction at the cathodic chamber was successfully demonstrated. When NC was employed as the electron acceptor, the chemical oxygen demand (COD) removal and dye decolourisation efficiencies obtained at the anodic and cathodic chamber were 73±3% and 95.1±1.1%, respectively. This study demonstrated that the decolourisation rates of monoazo dyes were ∼50% higher than diazo dyes. The maximum power density in relation to NC decolourisation was 20.64mW/m2, corresponding to current density of 120.24mA/m2. The decolourisation rate and power output of different azo dyes were in the order of NC>AO7>RR120>RG19. The findings revealed that the structure of dye influenced the decolourisation and power performance of MFC. Azo dye with electron-withdrawing group at para substituent to azo bond would draw electrons from azo bond; hence the azo dye became more electrophilic and more favourable for dye reduction.
Textile wastewater contains methylene blue (MB), a major coloring agent in textile industry. Activated carbon (AC) is the most widely used adsorbent in removing dyes from industrial wastewater. However, high production cost of AC is the major obstacle for its wide application in dye wastewater treatment. In this study, a sustainable approach in synthesizing graphenic adsorbent from palm oil mill effluent (POME), a potential carbonaceous source, has been explored. This new development in adsorption technique is considered as green synthesis as it does not require any binder during the synthesis process, and at the same time, it helps to solve the bottleneck of palm oil industry as POME is the main cause contributed to Malaysia's water pollution problem. The synthesized GSC was characterized through XRD, FESEM, and EDX. The adsorption performance of the synthesized GSC was evaluated by adsorption of MB. The effect of initial concentration of synthetic MB solution (1-20 mg/L) and weight of GSC (5-20 g) were investigated. A remarkable change in color of synthetic MB solution from blue to crystal clear was observed at the end of adsorption study. High efficiency of the synthesized GSC for dye-contaminated wastewater treatment is concluded.
The textile industry consumes a large volume of organic dyes and water. These organic dyes, which remained in the effluents, are usually persistent and difficult to degrade by conventional wastewater treatment techniques. If the wastewater is not treated properly and is discharged into water system, it will cause environmental pollution and risk to living organisms. To mitigate these impacts, the photo-driven catalysis process using semiconductor materials emerges as a promising approach. The semiconductor photocatalysts are able to remove the organic effluent through their mineralization and decolorization abilities. Besides the commonly used titanium dioxide (TiO2), manganese dioxide (MnO2) is a potential photocatalyst for wastewater treatment. MnO2 has a narrow bandgap energy of 1~2 eV. Thus, it possesses high possibility to be driven by visible light and infrared light for dye degradation. This paper reviews the MnO2-based photocatalysts in various aspects, including its fundamental and photocatalytic mechanisms, recent progress in the synthesis of MnO2 nanostructures in particle forms and on supporting systems, and regeneration of photocatalysts for repeated use. In addition, the effect of various factors that could affect the photocatalytic performance of MnO2 nanostructures are discussed, followed by the future prospects of the development of this semiconductor photocatalysts towards commercialization.
The treatment of single and binary azo dyes, as well as the effect of the circuit connection, aeration, and plant on the performance of UFCW-MFC, were explored in this study. The decolorization efficiency of Remazol Yellow FG (RY) (single dye: 98.2 %; binary dye: 92.3 %) was higher than Reactive Black 5 (RB5) (single: 92.3 %; binary: 86.7 %), which could be due to monoazo dye (RY) requiring fewer electrons to break the azo bond compared to the diazo dye (RB5). In contrast, the higher decolorization rate of RB5 in binary dye indicated the removal rate was affected by the electron-withdrawing groups in the dye structure. The closed circuit enhanced about 2% of color and 4% of COD removal. Aeration improved the COD removal by 6%, which could be contributed by the mineralization of intermediates. The toxicity of azo dyes was reduced by 11-26% and the degradation pathways were proposed. The dye removal by the plants was increased with a higher contact time. RB5 was more favorable to be uptook by the plant as RB5 holds a higher partial positive charge. 127.39 (RY), 125.82 (RB5), and 58.66 mW/m3 (binary) of maximum power density were generated. The lower power production in treating the binary dye could be due to more electrons being utilized for the degradation of higher dye concentration. Overall, the UFCW-MFC operated in a closed circuit, aerated, and planted conditions achieved the optimum performance in treating binary azo dyes containing wastewater (dye: 87-92%; COD: 91%) compared to the other conditions (dye: 83-92%; COD: 78-87%).
An effective hydrothermally prepared chitosan-benzaldehyde/SiO2 adsorbent (CTA-BZA/SiO2) employed functionalization of a CTA biopolymer with SiO2 nanoparticles and BZA. CTA-BZA/SiO2 is an adsorbent that was utilized for the adsorption of an acidic dye (acid red 88, AR88) from synthetic wastewater. The fundamental adsorption variables (A: CTA-BZA/SiO2 dosage (0.02-0.1 g); B: pH (4-10); and C: duration (10-60)) were optimized via the Box-Behnken design (BBD). The Langmuir and Freundlich isotherms (coefficients of determination R2 = 0.99) agreed well with empirical data of AR88 adsorption by CTA-BZA/SiO2. The pseudo-first-order model showed reasonable agreement with the kinetic data of AR88 adsorption by CTA-BZA/SiO2. The maximal AR88 adsorption capacity (qmax) for CTA-BZA/SiO2 was identified to be 252.4 mg/g. The electrostatic attractions between both the positively charged CTA-BZA/SiO2 adsorbent and the AR88 anions, plus the n-π, π-π, and H-bond interactions contribute to the favourable adsorption process. This study reveals that CTA-BZA/SiO2 has the capacity to be a suitable adsorbent for the removal of a wider range of organic dyes from industrial effluents.
Recently, the phyco-synthesis of nanoparticles has been applied as a reliable approach to modern research field, and it has yielded a wide spectrum of diverse uses in fields such as biological science and environmental science. This study used marine natural resource seaweed Sargassum myriocystum due to their unique phytochemicals and their significant attributes in giving effective response on various biomedical applications. The response is created by their stress-tolerant environmental adaptations. This inspired us to make an attempt using the above-mentioned charactersitics. Therfore, the current study performed phycosynthesis of titanium dioxide nanoparticles (TiO2-NPs) utilising aqueous extracts of S. myriocystum. The TiO2-NPs formation was confirmed in earlier UV-visible spectroscopy analysis. The crystalline structure, functional groups (phycomolecules), particle morphology (cubic, square, and spherical), size (∼50-90 nm), and surface charge (negative) of the TiO2-NPs were analysed and confirmed by various characterisation analyses. In addition, the seaweed-mediated TiO2-NPs was investigated, which showed potential impacts on antibacterial activity and anti-biofilm actions against pathogens (Staphylococcus aureus, S. epidermidis, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, and Klebsiella pneumoniae). Additionally, some evaluations were performed on larvicidal activities of TiO2-NPs in oppose to Aedes aegypti and Culex quinquefasciatus mosquitos and the environmental effects of photocatalytic activities against methylene blue and crystal violet under sunlight irradiation. The highest percent of methylene blue degradation was observed at 92.92% within 45 min. Overall, our findings suggested that S. myriocystum mediates TiO2-NPs to be a potent disruptive material for bacterial pathogens and mosquito larvae and also to enhance the photocatalytic dye degradation.
A thermal degradation pathway of the decolourisation of Reactive Cibacron Blue F3GA (RCB) in aqueous solution through catalytic thermolysis is established. Catalytic thermolysis is suitable for the removal of dyes from wastewater as it breaks down the complex dye molecules instead of only transferring them into another phase. RCB is a reactive dye that consists of three main groups, namely anthraquinone, benzene and triazine groups. Through catalytic thermolysis, the bonds that hold the three groups together were effectively broken and at the same time, the complex molecules degraded to form simple molecules of lower molecular weight. The degradation pathway and products were characterized and determined through UV-Vis, FT-IR and GCMS analysis. RCB dye molecule was successfully broken down into simpler molecules, namely, benzene derivatives, amines and triazine. The addition of copper sulphate, CuSO4, as a catalyst, hastens the thermal degradation of RCB by aiding in the breakdown of large, complex molecules. At pH 2 and catalyst mass loading of 5 g/L, an optimum colour removal of 66.14% was observed. The degradation rate of RCB is well explained by first order kinetics model.
Free laccase and fungal biomass from white-rot fungi were compared in the thermokinetics study of the laccase-catalyzed decolorization of an azo dye, i.e., Trypan Blue. The decolorization in both systems followed a first-order kinetics. The apparent first-order rate constant, k1', value increases with temperature. Apparent activation energy of decolorization was similar for both systems at ∼ 22 kJ mol(-1), while energy for laccase inactivation was 18 kJ mol(-1). Although both systems were endothermic, fungal biomass showed higher enthalpy, entropy, and Gibbs free energy changes for the decolorization compared to free laccase. On the other hand, free laccase showed reaction spontaneity over a wider range of temperature (ΔT = 40 K) as opposed to fungal biomass (ΔT = 15 K). Comparison of entropy change (ΔS) values indicated metabolism of the dye by the biomass.
The emergence of thermal modalities has promoted the use of heat-sensitive phantoms for calibration, measurement, and verification purposes. However, development of durable phantoms with high precision ability to represent the temperature distribution remains a challenge. This study aims to introduce a reusable phantom that provides an accurate assessment of the heated region in various thermal modalities.
Dyes are known to be a causative agent of occupational asthma exposed to them. We evaluate respiratory symptoms among textile. The study population comprised 106 exposed workers and control (unexposed) group. Data were collected by a questionnaire. Pulmonary Function Tests (PFTs) were performed. Among the exposed workers 36.8% defined phlegm. Respiratory symptoms were not significantly different between two groups. The employment duration of the exposed workers with phlegm was longer than those without phlegm (p = 0.027). The mean % predicted of forced expiratory flow (FEF) 25-75 of the exposed workers was found to be significantly lower than the control (unexposed) group (p = 0.01). Our study suggests that textile dyeing might cause respiratory symptoms at workers.
The potential of base treated Shorea dasyphylla (BTSD) sawdust for Acid Blue 25 (AB 25) adsorption was investigated in a batch adsorption process. Various physiochemical parameters such as pH, stirring rate, dosage, concentration, contact time and temperature were studied. The adsorbent was characterized with Fourier transform infrared spectrophotometer, scanning electron microscope and Brunauer, Emmett and Teller analysis. The optimum conditions for AB 25 adsorption were pH 2, stirring rate 500 r/min, adsorbent dosage 0.10 g and contact time 60 min. The pseudo second-order model showed the best conformity to the kinetic data. The equilibrium adsorption of AB 25 was described by Freundlich and Langmuir, with the latter found to agree well with the isotherm model. The maximum monolayer adsorption capacity of BTSD was 24.39 mg/g at 300 K, estimated from the Langmuir model. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined. It was found that AB 25 adsorption was spontaneous and exothermic.
A new heterogeneous catalyst for sonocatalytic degradation of amaranth dye in water was synthesized by introducing titania into the pores of zeolite (NaY) through ion exchange method while Fe (III) was immobilized on the encapsulated titanium via impregnation method. XRD results could not detect any peaks for titanium oxide or Fe(2)O(3) due to its low loading. The UV-vis analysis proved a blue shift toward shorter wavelength after the loading of Ti into NaY while a red shift was detected after the loading of Fe into the encapsulated titanium. Different reaction variables such as TiO(2) content, amount of Fe, pH values, amount of hydrogen peroxide, catalyst loading and the initial dye concentration were studied to estimate their effect on the decolorization efficiency of amaranth. The maximum decolorization efficiency achieved was 97.5% at a solution pH of 2.5, catalyst dosage of 2 g/L, 20 mmol/100 mL of H(2)O(2) and initial dye concentration of 10 mg/L. The new heterogeneous catalyst Fe/Ti-NaY was a promising catalyst for this reaction and showed minimum Fe leaching at the end of the reaction.
The extraction of Red 3BS reactive dye from aqueous solution was studied using emulsion liquid membrane (ELM). ELM is one of the processes that have very high potential in treating industrial wastewater consisting of dyes. In this research, Red 3BS reactive dye was extracted from simulated wastewater using tridodecylamine (TDA) as the carrier agent, salicyclic acid (SA) to protonate TDA, sodium chloride as the stripping agent, kerosene as the diluent and SPAN 80 as emulsifier. Experimental parameters investigated were salicyclic acid concentration, extraction time, SPAN 80 concentration, sodium chloride concentration, TDA concentration, agitation speed, homogenizer speed, emulsifying time and treat ratio. The results show almost 100% of Red 3BS was removed and stripped in the receiving phase at the optimum condition in this ELM system. High voltage coalesce was applied to break the emulsion hence, enables recovery of Red 3BS in the receiving phase.
A modified hydrophilic penta-bismuth hepta-oxide nitrate (Bi5O7NO3) surface was synthesized via a precipitation method using TiO2 and Ag as modified agents. The synthesized product was characterized by different analytical techniques. The removal efficiency was evaluated using mono- and di-sulphonated azo dyes as model pollutants. Different kinetic, isotherm and diffusion models were chosen to describe the adsorption process. X-ray photoelectron spectroscopy (XPS) results revealed no noticeable differences in the chemical states of modified adsorbent when compared to pure Bi5O7NO3; however, the presence of hydrophilic centres such as TiO2 and Ag developed positively charged surface groups and improved its adsorption performance to a wide range of azo dyes. Dyes removal was found to be a function of adsorbent dosage, initial dye concentration, solution pH and temperature. The reduction of Langmuir 1,2-mixed order kinetics to the second or first-order kinetics could be successfully used to describe the adsorption of dyes onto the modified adsorbent. Mass transfer can be described by intra-particle diffusion at a certain stage, but it was not the rate limiting step that controlled the adsorption process. Homogenous behavior of adsorbent surface can be explored by applying Langmuir isotherm to fit the adsorption data.