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In this paper, silica nanoparticle (SN) and amine-functionalized silica nanoparticle (AFSN) were prepared and their dye removal abilities were investigated. Physical characteristics of adsorbents were studied using the point of zero charge, surface area, Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Three textile dyes, Acid Red 14 (AR14), Acid Black 1 (AB1) and Acid Blue 25 (AB25), were used as model compounds. The effect of operational parameter such as adsorbent dosage, pH, dye concentration and salt were evaluated. The isotherm and kinetic of dye adsorption were studied. The maximum dye adsorption capacity (Q 0 ) of SN for AR14, AB1 and AB25 was 0.031mg/g, 0.034mg/g and 0.170mg/g, respectively. But the maximum dye adsorption capacity of AFSN for AR14, AB1 and AB25 was 434mg/g, 250mg/g and 167mg/g, respectively. It was found that dye adsorption onto SN and AFSN followed with Freundlich and Langmuir isotherms, respectively. Adsorption kinetic of dyes was found to conform to pseudo-second order kinetics. Based on the data of present investigation, one could conclude that the AFSN being an eco-friendly adsorbent with high dye adsorption capacity might be a suitable alternative to remove dyes from colored aqueous solutions.
Herein, the ternary nanostructure of titania (TiO2) decorated with graphene quantum dot (GQD)/zeolitic imidazolate framework-8 (ZIF-8) (T/G/Z: TiO2/GQD/ZIF-8) was synthesized by a hierarchical approach, and its photocatalytic activity was investigated for the degradation of the doxycycline (DOX) as a pharmaceutical and dyes under visible light irradiation. Increasing the doping content of the graphene quantum dot from 0.002 g to 0.02 g was accompanied by an increase in photocatalytic activity. A further increase to 0.2 g, the thickening or aggregation of the GQD layer on the TiO2 surface, or the thorough coverage of the TiO2 surface with the GQD occurred and effective light irradiation to TiO2 nanoparticles has not been done well. Thus the reduction of the catalytic activity happened. The photocatalytic degradation rate has increased outstandingly over this period of time for ternary composite in this concentration at intervals of the sampling period. The increase in pollutant concentration was associated with decreased photocatalytic degradation. Increasing the dose of photocatalysts improved the rate of pollutant degradation. The degradation efficiency of doxycycline in the presence of l-ascorbic acid scavenger had a notable decrease, while the presence of formic acid and isopropyl alcohol was less effective in the DOX degradation. It can be explained that the superoxide anion radical has the greatest effect on the degradation process of doxycycline. The DOX degradation kinetics followed the first-order kinetics with high correlation coefficients. This work has provided profound insight based on heterogeneous structures for efficient photocatalysts in the degradation of wastewater pollutants (pharmaceutical and dyes).
Immobilized titanium(IV) oxide nanoparticles were used for the photocatalytic degradation of Acid Red 14 (AR 14). A simple and effective method was used for immobilization of titanium(IV) oxide nanoparticles. Photocatalytic degradation processes were performed using pilot scale (7L) colored dye solutions. UV–vis and ion chromatography (IC) analyses were employed to obtain the details of the photocatalytic degradation of AR 14. It has been found that adsorption has a negligible effect on the aqueous dye concentration and the photocatalytic process occurred at solution bulk. The effects of operational parameters such as H2O2, dye concentration, anions (NO3 −, Cl−, SO4 2−, HCO3 − and CO3 2−) and pH were investigated. Reaction rate was drastically inhibited by carbonate. Produced aromatic intermediates were not studied. Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO2. Nitrate and sulfate anions were detected as the photocatalytic mineralization of AR 14. Kinetics analysis indicates that the photocatalytic decolorization rates can usually be approximated first-order model for AR 14. Results show that the employment of optimal operational parameters may lead to complete decolorization and mineralization of dye solutions.
In this paper, the corrosion inhibition of cationic gemini surfactant 1,4-butan-bis- (dimethyl dodecyl ammonium bromide), in the absence and presence of halide salts (NaCl, NaBr and NaI) on steel in HCl was investigated at 20±1 °. The effects of pH, immersion time and salt concentration on the corrosion inhibition of steel were studied using weight loss, open circuit potential and electrochemical impedance spectroscopy. Inhibition efficiency increases by increasing surfactant concentration. Synergistic effect between surfactant and salts was studied. The inhibition efficiency increases by increasing salt concentration. This composite inhibitor containing gemini surfactant and halide was efficient and low-cost for steel corrosion inhibition in HCl.
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Herein, nanozeolite - carbon nanotube composites with the covalently immobilized enzyme (Laccase) as novel bionanocomposites were synthesized and used for pollutant (Direct Red 23) bio-degradation. Different amounts of carbon nanotube (30, 50, and 70 mg) were used to synthesize carbon nanotube -zeolite nanocomposites. The synthesized nanomaterials were silanized and cross-linked by glutaraldehyde. Finally, the enzyme was immobilized on them to prepare Laccase immobilized nanomaterials. The biocatalysts were characterized using Scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), and Transmission Electron Microscopy (TEM). The effect of operational parameters on bio-degradation was investigated and optimized. The synthesized biocatalyst nanocomposite retained more than 95% of its initial activity over the first 5 cycles and its efficiency is still intact. After 10 cycles relative activity decreased gradually to 69%. Results revealed much higher stability for Laccase after the immobilization and 84% of the maximum activity of nanocomposite was preserved at 80 °C. The activity of free Laccase lost over 60% of its activity after 8 days of incubation while the nanocomposite retained about 80% of its maximal activity. They had high storage stability over 8 incubation days and good performance at thermal stability experiments (45–80 °C for 1 h).
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This paper investigates the ability of activated carbon (AC) to adsorb two anionic dyes from colored wastewater in single and binary systems. Direct Blue 78 (DB78) and Direct Red 31 (DR31) were used as anionic dye models. The surface characteristics of AC were investigated using fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The effects of AC dosage, initial dye concentration and salt on dye removal were investigated at 25°C. The kinetic and isotherm of dye adsorption were studied. Adsorption kinetic of dyes was studied in single and binary systems and rate sorption was found to conform to pseudo — second order kinetic model. The isotherm data of dyes in single and binary systems followed Langmuir isotherm. The maximum adsorption capacity (Q0) of DB78 and DR31 was 76.92mg/g and 111mg/g for single system and 76.92mg/g and 125mg/g for binary system, respectively. Results indicated that AC could be used as an adsorbent to remove the anionic dyes from single and binary pollutants systems.
Nowadays, the overuse of dyes and their presence in wastewater can be considered as an environmental concern.In this study, zeolitic imidazole framework-8 (ZIF-8), zinc oxide (ZnO), and their composite (ZnO-ZIF-8) were synthesized and characterized by scanning electron microscopy, Fourier transform infrared, X-ray diffraction, and zeta potential techniques.The synthesized materials were used for the removal of Malachite green (MG) from aqueous media via a batch adsorption process.The adsorption isotherm, and the effects of operational parameters, including adsorbent dosage, initial dye concentration, time, and pH on dye removal, were comprehensively studied.The adsorption capacity of the composite was 3,654 mg/g.The results showed that the experimental data were fitted by the Freundlich isotherm model with a high correlation coefficient (0.9676).Moreover, the ability of the prepared adsorbents (ZIF-8, ZnO, and ZnO-ZIF-8) for the removal of dyes from binary systems containing MG and Rhodamine-B (Rh-B) was evaluated.
An amazing combination of zero-dimensional graphene quantum dots (GQDs) with three-dimensional metal-organic frameworks (MOFs) improves the resulting nanocomposite properties. Herein, The GQD was incorporated in the ZIF-8 surface, to emphasize another application of GQD that has been less considered before. The characteristics of synthesized nanomaterials were confirmed by FTIR, XRD, TGA, BET, Raman, SEM, and HRTEM. The removal of malachite green (MG) was investigated to compare the adsorption properties of nanocomposite with pristine GQD and ZIF-8. The effects of GQD loading dose in composite (2–20%), adsorbents dosage (0.7–2.5 mg), initial dye concentration (20–50 mg/L), and the pH of MG solution (4−7) as the influential parameters on pollutant removal were investigated. The dye adsorption capacity of hybrid nanocomposite (2500 mg/g) was reasonably better than pure GQD (294 mg/g) and MOF (1111 mg/g). Besides, this process was in good agreement with the pseudo-second-order kinetics and the Langmuir isotherm model
Corrosion inhibition efficiency of Gemini surfactant 1,4-butan-bis-dimethyl dodecyl ammonium bromide (designed as 12-4-12), 1,4-butan-bis-dimethyl tetradecyl ammonium bromide (designed as 14-4-14), conventional surfactants dodecyl thrimethyl ammonium bromide (DTAB) and tetradecyl thrimethyl ammonium bromide (TTAB) on low carbon steel is investigated using three common methods namely, weight loss, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The influence of chain length and temperature of the media is verified. Data indicate that, the corrosion inhibition efficiency is improved by increasing the concentration and chain length of the surfactants. Corrosion rate of steel increases by increasing the temperature of the medium containing surfactant. Adsorption isotherm of used surfactants and kinetic parameters are studied.
In this paper, the oxidation of dyes from colored textile wastewater by activated carbon (AC)/hydrogen peroxide (H2O2) was discussed. Acid Red 18 (AR18), Direct Red 80 (DR80) and Reactive Red 194 (RR194) were used as model dyes. The surface characteristics of AC were investigated using Fourier transform infrared (FTIR). Dye oxidation by AC/H2O2 was studied by UV–Vis spectrophotometer and Ion chromatography (IC). The effects of AC dosage, initial dye concentration, pH and salt on dye oxidation were evaluated. Kinetics analysis indicated that the dye oxidation rates could be approximated at pseudo-second order model. Formate anion was detected as dominant aliphatic intermediate. Results indicated that the AC/H2O2 could be used as an eco-friendly material to degrade dyes from colored wastewater.
In this study, alginate as a low-cost and eco-friendly adsorbent was modified to remove dyes from wastewater. Modification of alginate was done using ethylenediamine. Fourier transform infrared was used to study the characteristic of alginate and modified alginate. The presence of functional groups such as hydroxyl, carboxylate, and amine groups was detected. Modified alginate was used to remove Direct Red 23 (DR 23), Direct Red 31 (DR 31), and Direct Red 80 (DR 80) from aqueous solution. The effect of three parameters such as adsorbent dosage, pH, and inorganic salts on dye removal was investigated at room temperature (26°C). During the dye removal study, the dye adsorption isotherm and kinetic were studied. It was found that DR 23 and DR 80 followed with Tempkin isotherm and DR 31 followed with Langmuir isotherm. In addition, the adsorption kinetic of dyes was found to fit into pseudo-second-order kinetics. Based on the obtained data from the current investigation, it could be concluded that the modified alginate as a biocompatible green material and low-cost adsorbent might be an appropriate alternative to remove anionic dyes from colored wastewater.
Herein, composites with different morphologies (diamond-like, rod-like, and spindle-like) were successfully synthesized using MIL88A (Fe) and graphene quantum dots (GQDs) to remove Acid Blue 92 (AB92), pharmaceuticals (doxycycline, and tetracycline). Despite the similarity in content, chemical structure, and functional groups of the composites, interesting differences were observed in some of their physicochemical properties (BET, RAMAN, TEM, and SEM) and adsorption performance, which was the turning point of this research. Spindle-like GQDMIL88A composite with the adsorption capacity of 617 mg/g indicated the highest adsorption capacity for Acid Blue 92 (AB92) compared to 335 mg/g for rod-like composites and 114 mg/g for diamond-like composites. Also, for doxycycline removal, the spindle-like composite with the adsorption capacity of 796 mg/g, was still in the first rank, compared to 588 mg/g for rod-like and 469 mg/g for diamond-like GQDMIL88A. The tetracycline adsorption capacity for spindle-like, rod-like, and diamond-like GQDMIL88A composites was 672 mg/g, 398 mg/g, and 300 mg/g, respectively. According to the findings of this study, despite the different adsorption capacities of different GQDMIL88A composite morphologies, all three types are well compatible with the Langmuir isotherm and pseudo-second-order kinetics.
