Optimized adsorption of xylenol orange dye in water systems employing CTAB-treated montmorillonite composite

This study describes the removal of methyl orange (MO) and methyl red (MR) dyes from water samples using morpholinomethylcalix[4]arene immobilised silica (MIS) resin. The silica surface has been modified by p-morpholinomethylcalix[4]arene moiety and was characterised by FT-IR spectroscopy and SEM techniques. The adsorption capacity of MIS-resin was checked through batch adsorption experiments under the optimised conditions of pH, MIS-resin dose, time, and temperature. Results show that adsorption of MO and MR dyes are highly affected by the change in pH; thus, the higher adsorption percentages were achieved at pH 5.3 and 6.6 respectively. The adsorbent dosage has been optimised and it was noticed that the maximum adsorption was achieved by using 40 mg.L−1 of MIS-resin dose. The adsorption rate of dyes was investigated by applying the pseudo-first and second-order kinetic models and it has been observed that the experimental data shows a better correlation coefficient with the pseudo-second-order kinetic model. The feasibility of adsorption was analysed by thermodynamic parameters such as ∆H°, ∆G°, and ∆S° values indicate that the adsorption of dyes is exothermic and spontaneous. The equilibrium data have been validated using Langmuir and Freundlich models and the Langmuir model has a good correlation coefficient (R2 0.99). The MIS-resin was applied onto industrial effluents and it has been observed that the prepared resin is a very efficient adsorbent for the treatment of dyes contaminated wastewater. The adsorption of MO and MR dyes onto MIS-resin was well defined by computational chemical modelling at the B3LYP/LANL2DZ/6-311++G (d,p) level using G09W software.

Dyes, which have mutagenic, embryotoxic, and carcinogenic effects on terrestrial animals and resistance to degradation in the presence of air and light, have emerged as a potent pollutant of water today. Out of all developed methods to treat contaminated water, adsorption remains propitious due to its advantages such as simple process, low cost, ease, eco-friendliness, and reusability. Herein, the adsorbent epichlorohydrin-grafted nanopolyaniline (PANI-g-EC) was synthesized by the ring-opening reaction of epichlorohydrin by nanopolyaniline, where the nanopolyaniline acted as a nucleophile. The grafting of nanopolyaniline was confirmed by Fourier transform infrared (FTIR). The morphology and particle size of PANI-g-EC were examined by field emission-scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), showing a sponge-like structure with an average particle size of 42 nm. The adsorption parameters such as dosage of the adsorbent, initial dye concentration, pH, temperature, and thermodynamic parameters (ΔGo, ΔHo, ΔSo) of the adsorption process were extensively studied for potential application. The maximum adsorption of dyes occurs at 35 °C in the presence of 0.16 g·L-1 adsorbent for 120 min at their respective pH. PANI-g-EC shows pH-selective adsorption of both cationic and anionic dyes with a maximum adsorption capacity of 588.55 mg.g-1 for methylene blue at pH 8 and 317.89 mg.g-1 for methyl orange dye at pH 2. The adsorption process follows the pseudo-second-order reaction kinetics and Langmuir adsorption isotherm. The electrostatic force of attraction is found to be responsible for the adsorption of dyes.

Ferromagnetic γ-Fe2O3 was modified with stearic and oleic acids. Diffuse reflection spectra show that modification occurs both via the interaction with free surface hydroxyl groups and by forming bidentate carboxylates with iron atoms. Surface modification enhances adsorption of water-soluble organic dyes (orange acid and methylene blue dyes, cytochrome C enzyme) due to contribution of hydrophobic interaction to adsorption. Differences in adsorption of dyes onto the modified γ-Fe2O3 caused by different structures of hydrocarbon chains in stearic and oleic acids were revealed. The effect of electrolyte concentration and pH of a solution on adsorption of cytochrome C was studied. The activated iron(III) oxide can be used as a magnetic carrier for immobilized enzymes in bioreactors and for targeted drug delivery.

AI-based modeling studies for dye removal using mixed biomass composites from algae and plant seeds: Isotherm, kinetics, and mechanistic insights

Roasted and ground coffee residue was investigated as an adsorbent lignocellulosic material capable of removing methyl orange dye from aqueous solutions by means of batch adsorption experiments. The effects of experimental parameters on the adsorption behavior, such as initial dye concentration, adsorbent dosage, initial pH and temperature were studied. A better adsorption of the dye was observed at acid pH, low temperature and with an adsorbent dosage of 6 g/L. A Pseudo-second order kinetics was found according to the Lagergren kinetic model. A maximum adsorption capacity of 1.3 mg methyl orange per gram of adsorbent was calculated by fitting the Langmuir model. The adsorption of methyl orange on the adsorbent analyzed was found to be exothermic in nature. The roasted and ground coffee residue was found to be viable for the primary treatment of wastewater contaminated with azoic-type compounds.

Background: Dye-containing wastewater causes irreparable damage to the ecological water system. Although adsorbents are widely used for treating wastewater containing dyes, the comparative investigation on these materials is still insufficient for their wide applications in the industries. Objective: With the aim of comparing efficient and fast adsorbent materials for cationic dyes, we analyzed and evaluated the adsorbents of the MCM-41 molecular sieve and activated carbons. Methods: The adsorption performance was studied on the common colored organics, such as cationic dyes of rhodamine B (RhB) and methylene blue (MB) dyes. The present work examined the impact of experimental variables, including initial dye concentration, adsorption time, and pH, on the adsorption process and performance, as well as the adsorption kinetics of the diverse adsorbents towards two cationic dyes. Results: MCM-41 molecular sieves showed relatively high adsorption capacity for RhB and AC-2, which made their adsorption capacity for MB much higher than that of MCM- 41 molecular sieves. A comprehensive analysis was conducted using pseudo-first-order and pseudo-second-order to decipher the mechanism of dye adsorption. The heterogeneous adsorption mechanism could explain the dye adsorption behavior of MCM-41 molecular sieve and activated carbons. Conclusion: The results demonstrated the influence of the pore structure and surface properties of the adsorbents on the adsorption capacity of dye molecules in an aqueous solution. For the initial concentration of cationic dye solutions of 20 mg/L, the MCM-41 molecular sieve had a MB adsorption capacity of 130.8 mg/g under alkaline conditions at pH=10, while the activated carbon adsorbents showed a stable MB adsorption capacity of 266.6 mg/g under different pH conditions, proving their applicability in treating wastewater containing dyes under different acid/base environments.

In order to ascertain the relation between the change in the fibrous fine structure and the dyeability of nylon 6 fiber caused by its heat-setting, the ζ-potential, the surface dye adsorption, and the total dye adsorption of the heat-set nylon 6 fiber in an acidic solution (pH 3.0) of acid dye—Orange II were determined. The crystallinity and the birefringence of the fiber increase in the order of the untreated, the wet-heat-treated, and the dry-heat-treated fiber. The isoelectric points of the untreated, the wet-heat-treated, and the dry-heat-treated fiber are pH 5.4, pH 4.6, and pH 2.8 respectively. With the increase in the dye concentration, the sign of the ζ-potential of the untreated and the wet-heat-treated fiber in a dye solution change from positive to negative because of the electrostatic bonds between the NH3+ of the fiber and the dye anion, RSO3−, while the ζ-potential of the dry-heat-treated fiber increases its negative value because of the van der Waals’ forces between the fiber and the dye. The surface dye adsorption, as calculated from the difference between the surface charge density, Δσ, of the system with dye and that without dye, increases in any case as the dye concentration increases. The total dye adsorption increases as the dye concentration increases and attained the plateau regions at higher dye concentrations. The surface dye adsorptions become smaller in the order of the untreated, the dry-heat-treated, and the wet-heat-treated fiber. The total dye adsorptions become smaller in the order of the wet-heat-treated, the untreated, and the dry-heat-treated fiber. The differences in behavior among the fibers may be attributed to the adsorption of the dye to the loosely-packed portions in the amorphous region of the wet-heat-treated fiber, in addition to the differences in crystallinity and birefringence among the fibers. Moreover, the surface areas covered by adsorbed dye molecules, which were calculated from the reciprocal of the slope of the surface dye adsorption vs. the total dye adsorption curve of each fiber, were 1.8, 4.0, and 0.6×106cm2/g fiber in the order of the untreated, the wet-heat-treated, and the dry-heattreated fiber.

In order to ascertain the relation between the change in the fine structure and the dyeability of the nylon 6 fiber with its drawing, the ζ-potential, the surface dye adsorption, and the total dye adsorption of the drawn nylon 6 fiber in an acidic solution (pH 3.0) of acid dye—Orange II and Orange I were determined. The crystallinity and the birefringence of the fiber increase as the draw ratio increases. The isoelectric points of the fibers with the draw ratios of 1 (undrawn), 3, and 4 are pH 5.2, pH 5.4, and pH 5.4 respectively. The increase in the dye concentration changed the sign of the ζ-potential of these fibers in a dye solution from positive to negative and increased the absolute values of the ζ-potential. Moreover, it was suggested that these fibers combine with dye by electrostatic bonds. The surface dye adsorption as calculated from the difference between the surface charge density, Δσ, of the system with dye and that without dye increased in any case as the dye concentration increased. These values became smaller in the order of draw ratios: 1 (undrawn), 3, and 4. The total dye adsorption as well as the surface dye adsorption increased with the increase in the dye concentration and decreased with the drawing. Moreover, the surface areas covered by adsorbed dye molecules, which were calculated from the slope of the graph between the surface dye adsorption and the total dye adsorption, were 4.4, 2.9, and 1.8×106cm2/g fiber in the order of draw ratios: 1 (undrawn), 3, and 4. Also, the effect of the molecular structure of the dye on the ζ-potential, the surface dye adsorption, and the total dye adsorption was discussed.

The removal of dyes from industrial effluents is one of the most important industrial processes that is currently on academic demand. In this project, for the first time, Trachycarpus fortunei seeds are used as biosources for the synthesis of activated carbon (AC) using physical as well as acid–base chemical methods. The synthesized AC was initially characterized by different instrumental techniques, such as FTIR, BET isotherm, SEM, EDX and XRD. Then, the prepared activated carbon was used as an economical adsorbent for the removal of xylenol orange and thymol blue from an aqueous solution. Furthermore, the effect of different parameters, i.e., concentration of dye, contact time, pH, adsorbent amount, temperature, adsorbent size and agitation speed, were investigated in batch experiments at room temperature. The analysis of different techniques concluded that the pyrolysis method created a significant change in the chemical composition of the prepared AC and the acid-treated AC offered a high carbon/oxygen composite, which is graphitic in nature. The removal of both dyes (xylenol orange and thymol blue) was increased with the increase in the dye’s initial concentration. Isothermal data suggested that the adsorption of both dyes follows the Langmuir model compared to the Freundlich model. The equilibrium time for AC biomass to achieve the removal of xylenol orange and thymol blue dyes was determined to be 60 min, and the kinetic data suggested that the adsorption of both dyes obeyed the pseudo-second order model. The optimal pH for thymol blue adsorption was pH 6, while it was pH 2 for xylenol orange. The adsorption of both dyes increased with the increase in the temperature. The influence of the adsorbent amount indicated that the adsorption capacity (mg/g) of both dyes reduced with the rise in the adsorbent amount. Thus, the current study suggests that AC prepared by an acid treatment from Trachycarpus fortunei seeds is a good, alternative, cost effective, and eco-friendly adsorbent for the effective removal of dyes from polluted water.

The interest in pH-sensitive textile sensors is growing in the global market. Due to their low-cost production, mechanical stability, flexibility, air-permeability, washability, and reusability, they are more suitable than electronic sensor systems. The research tailored the pH-sensitive textile by applying the pH indicator methyl orange to the cotton fabric during conventional dyeing. Adsorption of methyl orange dye to cotton fabric is hindered due to electrostatic repulsive forces between dye anions and negatively charged cotton fibre. To overcome this problem, chemical modification of cotton fabric using a commercial product was performed. The pH sensitivity of the dyed fabric was spectrophotometrically evaluated. In addition, the colour fastness of dyed cotton fabric to washing, light, hot pressing and rubbing was investigated according to valid SIST EN ISO standards. The research results show that the pH-responsive cotton fabric was successfully developed. The chemical modification of cotton fabric is crucial for the increased adsorption of methyl orange dye. The halochromic effect was not only perceived spectrophotometrically but also with the naked eye. The developed halochromic cotton fabric showed poor colour fastness to light and good colour fastness to hot pressing and rubbing, while no significant improvement in colour fastness to washing was observed, even though the fabric was after-treated with a cationic fixing agent. Higher adsorption of the methyl orange dye to the cotton fabric during the dyeing process leads to less wastewater pollution after dyeing with unfixed dye and, thus, a reduction in wastewater treatment costs.

Artificial neural network optimization for methyl orange adsorption onto polyaniline nano-adsorbent: Kinetic, isotherm and thermodynamic studies

In current experimental study, waste crab shells were used for the synthesis of chitosan nanoparticles and characterized. Preparation of chitosan nanoparticles were done through series of processes involving demineralization, deproteinization, decolouration, deacetylation, and ball milling. Chitosan nanoparticles thus obtained were characterized using X-ray diffraction (XRD) analysis, FTIR (Fourier transform infrared) spectroscopy, and Transmission Electron Microscopy (TEM). The methylene blue and methyl orange dye adsorption was conducted with the aid of UV-vis Spectroscopy. The antibacterial ability of chitosan nanoparticles were also assessed for four different bacterial strains. X-ray diffraction results support the chitosan production and the crystalline nature of the synthesized chitosan. The presence of amine and amide functional groups was verified through FTIR analysis. The degree of de-acetylation was found to be 70.24%, as calculated from FTIR analysis. Transmission Electron Microscopy images of chitosan nanoparticles revealed a fibrous and crystalline structure with molecules aligned in an antiparallel fashion. The dye adsorption test revealed the methylene dye adsorption capacity of 187.7 mg/g whereas for methyl orange it was found to be 296.40 mg/g. The chitosan nanoparticles showed good antibacterial ability against four different bacterial strain.

Reuse of sustainable materials for xylenol orange dye and copper (II) ion ammoniacal removal

Hydrothermal conversion of urban food waste to chars for removal of textile dyes from contaminated waters.

Facile synthesis of polyamidoamine dendrimer gel with multiple amine groups as a super adsorbent for highly efficient and selective removal of anionic dyes