Adsorption Of Dye Molecules Research Articles

Effective utilization of Moringa seeds waste as a new green environmental adsorbent for removal of industrial toxic dyes

The Moringa seeds waste (MSW), which resulted from the oil extraction industry, contains many varieties of natural organic components such as flavonoid, tannins, phenolic and hydrolyzable carbohydrates. The MSW could be considered a promising and an efficient green adsorbent for wastewater treatment as it reduces the environmental impact of hazardous chemicals existing in the industrial wastewater. The present work is designated to clarify the possibility of using MSW for the removal of industrial dispersed red 60 (DR60) and Congo Red (CR) dyes from aqueous solutions. The factors affecting the adsorption process such as initial dye concentration, catalyst weight, pH value, and solution temperature were investigated. It was found that the adsorption rate for both dyes was very high at the initial stages of the process and then decreases until reaches the equilibrium. The adsorption rate of the DR60 dye was not affected by catalyst weight, pH or the solution temperature. Whereas the percentage of the CR dye removal is found to be 100% for all dyes concentrations except for the CR dye with high initial concentration (100mg/L), which reached only 85.3%. It was observed that the adsorption % of CR dye increases by increasing the temperature from 25 to 40°C. With more increases in the reaction temperature from 40 to 80°C, the CR removal decreases from 88.7 to 57.7%, respectively. This behavior can be attributed to the desorption behavior of the adsorbed dye molecules at a higher temperature. Accordingly, the optimum temperature for the CR dye adsorption is found at 40°C. A detailed study of the dye adsorption isotherms and kinetics was carried out and the results show that the dyes adsorption isotherms and kinetics are followed by Freundlich and pseudo-second-order models. Maximum amounts of dyes adsorbed were found to be 170.7 and 196.8mg/g for both CR and DR60 dyes, respectively, at 100mg/L concentration, 25°C and pH 7. The overall rate of adsorption process seems to be controlled by a chemical process mechanism involving valence forces through exchange or sharing of electrons between dyes and MSW adsorbent.

Macro-scale transport of the excitation energy along a metal nanotrack: exciton-plasmon energy transfer mechanism

Presently we report (i) excited state (exciton) propagation in a metal nanotrack over macroscopic distances, along with (ii) energy transfer from the nanotrack to adsorbed dye molecules. We measured the rates of both of these processes. We concluded that the effective speed of exciton propagation along the nanotrack is about 8 × 107 cm/s, much lower than the surface plasmon propagation speed of 1.4 × 1010 cm/s. We report that the transmitted energy yield depends on the nanotrack length, with the energy emitted from the surface much lower than the transmitted energy, i.e. the excited nanotrack mainly emits in its end zone. Our model thus assumes that the limiting step in the exciton propagation is the energy transfer between the originally prepared excitons and surface plasmons, with the rate constant of about 5.7 × 107 s−1. We also conclude that the energy transfer between the nanotrack and the adsorbed dye is limited by the excited-state lifetime in the nanotrack. Indeed, the measured characteristic buildup time of the dye emission is much longer than the characteristic energy transfer time to the dye of 81 ns, and thus must be determined by the excited state lifetime in the nanotrack. Indeed, the latter is very close to the characteristic buildup time of the dye emission. The data obtained are novel and very promising for a broad range of future applications.

Fabrication and Electrochemical Impedance Analysis of Dye-Sensitized Solar Cells With Titanium Dioxide Compact Layer and Graphene Oxide Dye Absorption Layer

Two different structures of titanium dioxide (TiO2) photoelectrode were fabricated to test for possible improvements in the photovoltaic properties of dye-sensitized solar cells (DSSCs). In the first layer, a TiO2 compact layer was deposited by radio frequency sputtering. It was able to transmit abundantly and showed excellent electron transport. The second layer of TiO2 photoelectrode was the dye absorption layer, which was composed of TiO2+graphene oxide (GO). The high specific surface area of GO increased the adsorption of dye molecules. The photovoltaic conversion efficiency (η), charge transport properties of the DSSC with a compact layer and a dye absorption layer were measured using electrochemical impedance spectroscopy. Experiment results showed η of the DSSC with a compact layer and a dye absorption layer achieved 3.15% because the electron transportation of DSSC had been enhanced by a compact layer and a dye absorption layer.

Engineering of rich nitrogen-doped and magnetic mesoporous carbon nanospheres with predictable size uniformity for acid dye molecules adsorption

Abstract The fabrication of monodispersed N-doped mesoporous carbon nanospheres (NMCNs) with a high N content remains a formidable challenge due to the decomposition of N-containing frameworks during the pyrolysis and the weak self-assembly ability between carbon precursors and templates. Herein, we demonstrated a strong hydrogen-bonding interaction driving self-assembly method to fabricate uniform NMCNs with rich N content. In this route, phloroglucinol-formaldehyde (PF) not only acted as a rigid phenolic resin framework to prevent N-containing framework from decompose during carbonization, but also provided greater driving force for the self-assembly interaction with F127 through enhanced hydrogen-bonding interaction. The nitrogen doping level, particle size and uniformity of the formed NMCNs could be facilely tuned by adjusting the concentrations of ethylenediamine (EDA). Interestingly, the NMCNs possess high N content (up to ∼ 13.2 wt%), high surface area (556 m2g−1) and large pore volumes (∼0.50 cm3/g). By engineering the compositional diversity inside the single nanoparticles, Fe3O4 nanoparticles can be introduced into the NMCNs. The resultant Fe-NMCNs showed efficient adsorption (283 mg g−1) and magnetic separation property for acid red 57. The feasibility of the fabrication strategy may provide a new insight into the understanding of preparing functionalized carbon nanomaterials with mesoporous structure.

Investigation of the effect of acid and base treatment of the photoanode on the photovoltaic parameters of Zn2SnO4-based DSSCs

We have investigated the influence of acid and base treatment of the Zn2SnO4-based photoanode on the photovoltaic performance of dye-sensitized solar cells (DSSCs). The results clearly showed that the acid treatment not only could not improve the photovoltaic performance of the fabricated DSSCs but also remarkably decreased their open circuit voltage and short current density which may be attributed to the increase in the number of the surface traps. Conversely, NaOH-treatment of the photoanodes increased the power conversion efficiency of DSSCs by about 93% relative to the untreated photoanode. Electrochemical impedance spectroscopy confirmed that the base treatment reduces the charge recombination centers on the surface of the photoanode and then facilitates charge transport. Furthermore, the significant increase in the optical absorption of the NaOH-treated photoanode indicates that the base treatment apparently increases the amount of adsorbed dye molecules on the surface of the photoanodes which can be attributed to the increase in the basicity of the photoanode surface.

N3, N749 dyes effect on the TiO2 for optoelectronic applications

The present work aimed to study effect of (N749 & N3) dyes on TiO2 optical and electrical properties for optoelectronic application. The TiO2 paste prepared by using a doctor blade method. The samples were UV-VIS specterophometricall analyzes of TiO2 before and after immersed in dyes (N749 & N3). The results showed absorption spectra shift toward the visible region due to the adsorption of dye molecules on the surface of oxide nanoparticles. It is seen that the Eg determined to give a value of 3.3eV for TiO2 before immersing in dyes, and immersing in dyes (N749 & N3) are (1.4 &1.6 eV) respectively. The structural properties (XRD), (FTIR) and (SEM) for the sample prepared were investigated and (J-V) characteristics was studied, it was seen efficiency 3.8 % and 2.09 % for TiO2/N749, TiO2/N3, respectively.

Intensification of Rhodamine-B dye removal using hydrodynamic cavitation coupled with hydrogel adsorption

In this work, decolorization of rhodamine-B (Rh-B) dye was investigated by using a hybrid treatment technique involving hydrodynamic cavitation (HC) and hydrogel adsorption. Halloysite nanoclay embedded poly-acrylic acid (PAA) nanocomposite hydrogel was prepared by using the ultrasound polymerization technique. Halloysite nanoclay and the synthesized hydrogels were further characterized by using TEM analysis were carried out in order to confirm the structure and morphology of the respective materials. Decolorization of Rh-B dye was carried out by HC followed by adsorption of dye molecules on the hydrogel nanocomposite. Effect of different operating parameters such as inlet pressure to the cavitation device, effect of clay content in the hydrogel, effect of hydrogel loading in adsorption column, the effect of pH on Rh-B dye removal was tested. The individual effects of HC and hydrogel adsorption on Rh-B dye removal were also studied. It was found that the HC assisted hydrogel nanocomposite adsorption shows the decolorization of 65% at the optimized operating conditions such as, pH 7.62, 0.5 g clay loaded nanocomposite hydrogel, and 25 g of hydrogels loading in adsorption column. Addition of H2O2 into the hybrid system further enhances the decolourization of Rh-B dye to 72.85% with 45% of total organic carbon removal at the optimum conditions.

Hydrothermal preparation of Ag-TiO2-reduced graphene oxide ternary microspheres structure composite for enhancing photocatalytic activity

Photocatalysis technology is considered to be the most industrially feasible way to degrade industrial pollutants due to its low energy consumption and high efficiency. Graphene is considered to be the most potential carrier. Therefore, introducing it into TiO2 has great significance. In this study, We report Ag nanoparticles - modified TiO2 microspheres deposited on reduced graphene oxide (rGO) sheets material was prepared by two-step hydrothermal method. X-ray diffraction (XRD) analysis confirmed that the TiO2 microspheres are typical anatase phases and has the presence of Ag nanoparticles. The characterization of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that the graphene oxide was well reduced to rGO, which binds well to Ag-TiO2 microspheres. The prepared 2% Ag-TiO2-rGO microspheres composite showed the best degradation efficiency when degrading Rhodamine B, which caused RhB to degrade 96% in 100 min. At the same time, The modification of Ag nanoparticles on TiO2 microspheres facilitates the separation of photogenerated electron-hole pairs of TiO2, and electrons are further transferred to rGO to participate in photocatalytic reactions. In addition, the composite of rGO also increases the specific surface area of the sample, which is more favorable for the adsorption of dye molecules, so that 2% Ag-TiO2-rGO microspheres composite showed the highest efficiency for photodegradation of RhB.

Enhancing ferrate(VI) oxidation process to remove blue 203 from wastewater utilizing MgO nanoparticles

The aim of this study is to investigate the beneficial effect of utilizing MgO nanoparticles on the performance of ferrate(VI) oxidation process to remove blue-203 dye from wastewater. It was also made an attempt to assess the effects of pH, temperature, and MgO nanoparticle dosage on this oxidation process performance. Several sets of batch experiment were conducted to find out the effects of temperature ranging from 25 to 65 °C, pH ranging from 1.5 to 13, ferrate(VI) concentration ranging from 0.5 to 5.9 mg/L and MgO nanoparticles dosage ranging from 0.01 to 0.05 g in 150 mL solution on the removal efficiency. The results showed that adding MgO nanoparticles can improve the performance of ferrate(VI) oxidation removal method significantly, spec. at basic conditions. This synergistic effect can be attributed to the simultaneous adsorption of ferrate(VI) and dye molecules on the surface of nanoparticles. The results also revealed that the reaction between blue-203 dye and ferrate(VI) takes place rapidly at high mixing rate. It means that the required time to complete the removal process is controlled by mixing rate. It was finally concluded that adding MgO nanoparticles was an efficient means to enhance the performance of ferrate(VI) to oxidize blue-203 dye, esp. under basic conditions.

Methylene blue and crystal violet dyes removal (as a binary system) from aqueous solution using local soil clay: kinetics study and equilibrium isotherms

IN THIS PAPER, local soil clay as a low cost and affordable adsorbent was employed for the successful removal of methylene blue (MB) and crystal violet (CV) dyes from an aqueous binary system. The effect of various experimental conditions like adsorbate concentrations, time, temperature, and pH has been investigated. To know the adsorption performance of the dye molecules upon soil clay, the kinetics of the adsorption data were analyzed using various models such as pseudo-first-order and pseudo-second-order. This kind of study shows that the maximum adsorption reached at 2 min and uses the pseudo- second-order kinetics. The adsorption Kinetics have been investigated in the pH range of 2, 3.7, 7, and 8.7 at 25˚C and analyzed with two different models namely Langmuir and Freundlich. The interaction of dye molecules with soil clay has been investigated by SEM, EDS, FTIR, and XRD. Maximum removal of MB and CV up to 47.82 and 35.71 mg g-1, respectively was achieved by dye molecules adsorption onto soil clay. This effective removal method may provide a promising solution for eliminating of CV and MB dyes from wastewater.

Experimental and Atomic Modeling of the Adsorption of Acid Azo Dye 57 to Sepiolite

AbstractSepiolite is a hydrated magnesium silicate with a microporous and mesoporous structure. The fibrous morphology and the alternating blocks and tunnels along the fiber direction of sepiolite make it an ideal material to sequester a variety of organic and inorganic contaminants. The adsorption of various surfactants by organo sepiolites have been experimentally investigated. How this hydrophobic material adsorbs dye molecules at the atomic level, however, is a great mystery. For this reason, the present study focused on the adsorption of acid azo 57 dye molecules to modified sepiolite. For this purpose, the amenability of sepiolite to remove the anionic textile dye (acid azo red dye 57) was first studied in detail. Additionally, a typical cationic surfactant, hexadecyltrimethylammonium Br (HTAB), was used to modify sepiolite to increase the adsorption capacity. Zeta potential measurements on the sepiolite and the HTAB modified sepiolite were also carried out. Moreover, Density Functional Theory (DFT) studies were performed to understand the mechanism of the adsorption of dye molecules to natural and modified sepiolite surfaces. On the basis of the experimental studies, three general systems were theoretically examined: (i) HTAB molecules on sepiolite basal surfaces to represent four Si tetrahedra, (ii) neutral or charged acid azo red dye 57 molecules on sepiolite basal surfaces to represent four Si tetrahedra, and (iii) HTAB on the surface of neutral or charged acid azo red dye 57 molecules as a substrate. The results clearly indicated good agreement between the experimental studies and the theoretical computational DFT studies. For example, the double layer structure found in experimental studies was also demonstrated in DFT studies and confirmed increased adsorption in the presence of acid azo dye 57.

Graphene-Enhanced Raman Spectroscopy Reveals the Controlled Photoreduction of Nitroaromatic Compound on Oxidized Graphene Surface.

Although graphene-enhanced Raman spectroscopy has been investigated for several years, there have been no studies that have applied it to real-time observations of chemical catalytic reactions. Here, we report that UV/ozone-treated oxidized graphene was used to both control and monitor the photoreduction of an adsorbed nitroaromatic dye compound. Graphene-enhanced Raman spectroscopy studies show that more oxidized graphene surface leads to faster photoreduction. This is due to the lowering of the Fermi level in the oxidized graphene, which is in agreement with the highest occupied molecular orbital level of the adsorbed dye molecule, leading to a rapid electron transfer from graphene to the dye. Our findings will be useful in understanding and exploiting the photocatalytic properties of oxidized graphene on adsorbed molecular species.

Assembly of ZnO Nanoparticles on SiO2@α-Fe2O3 Nanocomposites for an Efficient Photo-Fenton Reaction

The SiO2@α-Fe2O3/ZnO metal oxide nanocomposites employed in this study were obtained using the sol-gel method. Their photocatalytic activities were enhanced by photo-Fenton reactions. The metal oxide composite of ZnO and α-Fe2O3 nanoparticles were deposited on the SiO2 nanospheres intended for visible light photocatalysis. Further, the as-synthesized SiO2@α-Fe2O3/ZnO nanocomposites exhibited a robust crystallinity and a high adsorption of dye molecules when compared to SiO2@ZnO and SiO2@α-Fe2O3 nanocomposites, respectively. The experimental results demonstrated a rapid Methylene Blue (MB) degradation among these catalysts within short intervals of time with the addition of α-Fe2O3/ZnO mixed metal oxide catalysts on the SiO2 nanospheres. Finally, a photo-Fenton reaction was implemented to confirm the presence of the hydroxyl (OH) radicals, which are powerful agents used for the degradation of organic pollutants.

Hydrothermal Synthesis of Ultra-Light Coal-Based Graphene Oxide Aerogel for Efficient Removal of Dyes from Aqueous Solutions.

A novel carboxymethyl cellulose (CMC)-supported graphene oxide aerogel (CGOA) was fabricated from a cost-effective and abundant bituminous coal by a mild hydrothermal process and freeze-drying treatment. Such an aerogel has cross-linked graphene oxide layers supported by CMC, and therefore, displays high mechanical strength while having ultra-low density (8.257 mg·cm−3). The CGOA has a 3D interconnected porous structure, beneficial graphene framework defects and abundant oxygen-containing functional groups, which offer favorable diffusion channels and effective adsorption sites for the transport and adsorption of dye molecules. The adsorption performance of rhodamine B by an optimized CGOA shows a maximum monolayer adsorption capacity of 312.50 mg·g−1, as determined by Langmuir isotherm parameters. This CGOA exhibited a better adsorption efficiency (99.99%) in alkaline solution, and satisfactory stability (90.60%) after three cycles. In addition, adsorption experiments on various dyes have revealed that CGOA have better adsorption capacities for cationic dyes than anionic dyes.

Mesoporous Hexanuclear Copper Cluster-Based Metal-Organic Framework with Highly Selective Adsorption of Gas and Organic Dye Molecules.

Despite many advances in the design and assembly of mesoporous metal-organic frameworks (meso-MOFs), it is still a challenge to obtain the desired structure. Here, we utilized an effective cluster cooperative assembly strategy by introducing SO42- ions as chelating binding sites to construct a novel mesoporous MOF, [Cu8(SO4)(TBA)6(OH)2( N,N-dimethylacetamide (DMA))4]·12DMA·12CH3OH [JLU-MOF51, H2TBA = 4-(1 H-tetrazol-5-yl)-benzoic acid]. Remarkably, the cooperative assembly of the infrequent hexanuclear [Cu6SO4(OH)2] cluster and the classical paddlewheel [Cu2(CO2)4] via linear hetero-N, O donor ligand results in an open three-dimensional framework, which possesses one-dimensional nanometer tube channels with the diameter of 24 and 28 Å. Fascinatingly, JLU-MOF51 displays an exceptionally large Langmuir surface area (5443 m2 g-1) and exhibits a high capacity for selective adsorption of C3H8 (C3H8: 348 cm3 g-1 at 273 K; C3H8/CH4 = 220 at 298 K). In addition, JLU-MOF51 can selectively adsorb fluorescein disodium salt dye among numerous organic dyes. An extremely high surface area and unique structural characteristics make JLU-MOF51 a promising meso-MOF material for the adsorption and separation of hydrocarbon gases and organic dyes. Moreover, this strategy will provide an effective means for constructing meso-MOFs via one-step synthesis.

Study of organic pollutant removal capacity for magnetite@ graphene oxide nanocomposites

In the present work, magnetite (Fe3O4) nanoparticles decorated graphene oxide (GO) sheets were synthesized using the chemical method. Graphene based nanocomposites show an effective adsorbent property, and therefore can be used as an organic pollutant remover from the aqueous medium. The X-ray diffraction analysis was done to investigate the crystallinity and particle size of Fe3O4 decorated GO sheets and the particle size was found to be 28 nm. Surface morphology of Fe3O4@GO nanocomposites was studied using transmission electron microscopy and the obtained inter planer spacing in Fe3O4@GO nanocomposites was 0.246 nm. For the applications point of view, these nanocomposites have been used for the removal of Rhodamine 6G dye molecules from the aqueous medium. The removal capacity was found to increase as the concentration of the nanocomposite increases. In Fe3O4@GO nanocomposites the GO sheets provide large surface area due to different functional groups like epoxide (C-O-C), carboxylic acid (-COOH), hydroxyl (-OH) to adsorb dye molecules. This study provides a new platform for the use of Fe3O4@GO nanocomposites in a water clean-up process.

Inertial impaction and surface diffusion-assisted rapid dye molecule adsorption on TiO2 thin films for highly efficient dye-sensitized solar cells

An effective and versatile single-stage aerosol impactor was specially designed to rapidly coat the surface of TiO2 thin films with a controlled amount of dye molecules via inertial impaction and surface diffusion to speed-up the manufacturing process and enhance the photovoltaic performance of dye-sensitized solar cells (DSSCs). By theoretically determining the specific dimensions of the aerosol accelerating nozzle and experimentally controlling the mixing ratio between the sheath gas and dye aerosol flow rates in the single-stage aerosol impactor, the speed and quality of dye adsorption on the TiO2 thin films of the photoelectrodes could be systematically assessed in terms of the photovoltaic performance of the DSSCs, including open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency (PCE). It was found that the aerosol impactor-assisted dye coating method developed in this study significantly reduced the duration of dye adsorption (aerosol coating duration = 20–60 min) and increased the PCE of the DSSCs to 7.28%. Using this methodology, dye-coating was ∼20 times faster and the fabricated device has 23% higher PCE compared to the DSSC fabricated by the conventional dip coating method (dip-coating duration = 1200 min, PCE = 5.92%). These results proved that the single-stage aerosol impactor designed in this study is a very effective and versatile device for rapidly coating the surface of TiO2 thin films with dye molecules using sufficient inertial impaction, which enables the introduced dye molecules to infiltrate and quickly adsorb on the surface of TiO2 nanoparticles accumulated in the DSSC photoelectrodes.

Single Crystalline-like and Nanostructured TiO2 Photoanodes for Dye Sensitized Solar Cells Synthesized by Reactive Magnetron Sputtering at Glancing Angle

The control of the surface area enhancement and the ordering of the mesoporous photoanode is one of the key parameters to overcome the current limits of performance of dye sensitized solar cells (DSSCs). These parameters are expected to improve both the concentration of adsorbed dye molecules on the photoanode and the charge collection. In this paper, reactive magnetron sputtering at glancing angle is employed to synthesize nanostructured TiO2 thin films. A post-annealing treatment under an ambient atmosphere at 773 K allows recrystallization of the films to form individual single crystal-like anatase nanocolumns, as shown on a reference structure constituted by well-separated slanted nanocolumns. Even if the best cells provide an open circuit voltage of 0.8 V, a fill factor of 77%, and a short circuit current density of 4.6 mA/cm2 (JSC) and permit to reach an overall efficiency up to 2.6%, it does not yet reach the performances of the reference TiO2 nanoparticle (NP)-based cell. This is explained by a po...

Statistical physics modeling of synthetic dyes adsorption onto Spirulina platensis nanoparticles.

Experimental adsorption of synthetic dyes, FD&C red no. 40 and Tartrazine, onto Spirulina platensis has been analyzed using a statistical physics treatment at different temperatures (298, 308, 318, and 328K) and at different values of pH (4, 6, and 8). The statistical physics formalism was used to develop the analytical expressions of models. The interpretation of the adsorption of these dyes on Spirulina platensis was achieved by choosing the adequate model and by presenting the evolution of the parameters involved in the analytical expression of this model such as the number of adsorbed dye molecules per site (nd), the receptor sites density (Dr), the adsorbed quantity at saturation (qs), and the molar adsorption energy (ΔE). Thus, several interpretations and results describing the adsorption of dyes on Spirulina platensis are extracted regarding the behaviors of these parameters at different temperatures and different values of pH. Thermodynamic functions such as the Gibbs free energy, the internal energy, and the entropy are studied at different values of pH.

Use of banana trunk waste as activated carbon in scavenging methylene blue dye: Kinetic, thermodynamic, and isotherm studies

Activated carbon (BTAC) derived from the banana trunk was utilized in this experiment to scavenge the methylene blue (MB) dye from synthetic dye solution. The optimized large surface area (1173.16 m2/g) BTAC was prepared with phosphoric acid (6.96 mol/L) chemical activation. The maximum adsorption capacity (qmax) of BTAC was experimentally observed to be 166.51 mg/g at 25 °C, and adsorbent dose of 1.5 g/L for 250 ppm dye concentration. The MB dye adsorption onto BTAC reached equilibrium within 20 min of contact time. The kinetic data shown equilibrium achieved quickly (20 min) and followed a linear equation of the pseudo-second-order kinetic model. The adsorption of dye molecules stacking in three layers on the surface of the BTAC, after each layer formation the rate of adsorption slow down, as evident from the intraparticle diffusion study. The thermodynamic study shown that adsorption was spontaneous and exothermic.