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In the present study, the fine powder of the aerial part of the invasive weed Chenopodium album has been explored to effectively eliminate the organic dye Crystal violet from its water solution. The fine powder of the aerial part of the weed has been characterized by scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy techniques. Its impact on various parameters of dye elimination has been investigated. It is found that the magnitude of adsorption is greater at pH 8 and increases with temperature. Different adsorption isotherms and kinetic models were employed to match the adsorption methods data. The data successfully fit the Freundlich, Hill adsorption model and interparticle models with R² values of 0.99, 0.99 and 0.97, respectively. The adsorption capacity of C. album based biosorbent was greater in batch experiments in comparison to bulk-using column operations. The biosorbent made of C. album can be used as a robust material for removing the dye Crystal violet. The bio-adsorbent used in the present study has exhibited much better efficiency (Qe = 219.4 mg/g) in comparison to the ash of the C. album employed for the adsorption of Crystal violet dye. [ABSTRACT FROM AUTHOR]

The development of new efficient photocatalysts is critical for a variety of applications including water purification and water splitting. Unfortunately, because TiO2 has a wide band gap, the photocatalytic applications of TiO2 NTAs are restricted to light in the ultraviolet (UV) range. Nanosized barium carbonate nanoparticles were prepared by a precipitation method at relatively low temperatures. The prepared samples were characterized by X-ray diffraction, UV-Visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy techniques. The nanocomposite exhibited a strong photocatalytic activity for decomposition of Crystal violet (CV) under visible light irradiation. The influences of catalyst amount, initial Crystal violet concentrations, pH of the reaction solution and different anions on CV decolorization and degradation reaction kinetics were investigated. The dye could be decolorized more efficiently in acidic media than alkaline media. Furthermore, the photocatalyst indicated phenomenal strength after four response cycles. At last, the conceivable component for the action upgrade was examined in detail. [ABSTRACT FROM AUTHOR]

Herein, we reported graphene oxide, as a suitable adsorbent for wastewater treatment to remove crystal violet dye from an aqueous solution. Crystal violet is used for various purposes including colouring, textile, pharmaceuticals etc. It has many harmful effects as it is non-biodegradable, toxic and carcinogenic in nature. So, it is very important to eradicate it from the water. Graphene oxide has been prepared by the modified Hummer's method and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray diffraction. Graphene oxide's removal efficiency depends on various factors including temperature, pH, and substrate concentration. The experimental data from batch studies is well substantiated with pseudo-second-order kinetics with an R² value of 0.98 and Temkin adsorption isotherm (R²: 0.94) with a Temkin constant (bT) value of 328 kJ/mol. It also closely fits the intraparticle diffusion model (R²: 0.99). The Langmuir adsorption capacity of graphene oxide was calculated to be 15.87 mg/g. The thermodynamic parameter study suggested that the adsorption process is exothermic and spontaneous in nature. Furthermore, a fixed bed column study was also conducted with a constant flow rate of 2.5 mL/min and bed height of 1 cm with a high concentration of crystal violet in a continuous mode of operation to evaluate its practical applicability and the area under the curve is found to be 4,701 cm². [ABSTRACT FROM AUTHOR]

This work aims to optimize the ozonation/adsorption coupling system as an advanced technique for the removal of the dye crystal violet (CV) in the presence of new innovative material based on the Capparis spinosa L waste (CSLW). Data from operational parameters such as adsorbent dose (X1), CV concentration (X2), and oxygen flow rate (X3) were used to optimize the dye removal rate (Y) by the Box--Behnken design (BBD) response surface methodology. Under the ideal conditions of X1 (2 g·L-1), X2 (100 mg·L-1), and X3 (4 L·min-1), the rate Y exceeded 99.75%. The complete removal of the CV dye by the ozonation/adsorption coupling results from the selective interactions between the surface groups of the CSLW material, the ozone, and the various charges present in the solution. The coupling mechanism indicates that ozonation partially degrades the CV dye and the adsorption process significantly increases the percentage of removal due to the different adsorbent--adsorbate interactions. Due to the low power consumption of the oxygenator and ozonator and the lack of CSLW cost, the treatment of CV by the ozonation/adsorption coupling could cost about $1.8518 L-1. Thus, this process could be generalized through an industrial pilot-scale application. [ABSTRACT FROM AUTHOR]

The aim of this work was to synthesize a low-cost hydrochar via hydrothermal route using two residues from the sugar-energy industries: sugarcane bagasse and the high-pressure boiler water discharge. The applicability of the hydrochar in water treatment process was tested in the biosorption of chloroquine from water in a discontinuous process. The synthesized hydrochar exhibited a high specific surface area (~188 mg·g-1) with average pore diameter <2.0 nm. The biosorption results showed a fast biosorption kinetic in the initial 10 min and an equilibrium time of ~60 min. Acidic properties of both contaminant and HC-T resulted in repulsive forces, therefore, basic conditions would represent the optimum condition for the highest chloroquine biosorption, but that is not interesting for a water treatment plant due to chemicals consumption for pH correction, costs and salinity problems. The pseudo-second-order kinetic and Sips isotherm models were the best models fitted to experimental data. The thermodynamic parameters indicated an endothermic and spontaneous biosorption. The maximum experimental biosorption capacity was 73.34 mg·g-1 at 45°C. In conclusion, hydrothermal-activated carbon (HC-T) is a promising biosorbent, synthesized with an ecofriendly process, for the removal of chloroquine from contaminated waters due to the great availability, quantity and low-cost of sugarcane bagasse in the Brazilian territory, allied with the reusability of high-pressure boiler water. [ABSTRACT FROM AUTHOR]

Malachite green (MG), a cationic dye, is evaluated for removal using carboxylated activated carbon that was made using an organochlorine chemical and sodium hydroxide in a wet milling process (MCGT-AC). Utilizing research in Brunauer-Emmett-Teller (BET), X-ray diffraction, environmental scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fouriertransform infrared spectroscopy, and high-resolution transmission electron microscopy, adsorption processes were described. As per zeta potential and point of zero charge analysis a suitable and stable pH of 6.5 was considered for the modelled dye solution with increasing pH supporting the sorption process well. It just took 30 min for the MG dye to reach equilibrium with the MCGT-AC. The experimental findings agree well with the Langmuir isotherm, which has a maximum adsorption capacity of 251.6 mg/g, according to isotherm study and error analysis. The activation energy (Ea = 51.36 kJ/mol) indicated that chemisorption was responsible for controlling the process. BET study showed that the sorbent's post-process pore size dramatically decreased, supporting effective adsorption. Overall, adding functional groups (carboxyl, hydroxyl, etc.) to the modified adsorbent surface improved the sorption capacity of MCGT-AC with activated carbon that had been surface modified with carboxylic groups. The initial dye concentration, adsorbent dose, contact time, pH, and other operational parameters were examined. Regeneration research on utilized MCGT-AC revealed that during the sixth cycle, adsorption capacity dropped from 95.7% to 48.6%. According to the results, MCGT-AC may be used as a cost-effective and effective adsorbent for the treatment of industrial wastewater, including dyes. [ABSTRACT FROM AUTHOR]

This study presents the preparation of oil palm empty fruit bunch (OPEFB) activated char from gasification plant residues via phosphoric acid chemical treatment for adsorption of methylene blue (MB) in aqueous solution. The Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis were conducted to identify the characteristic of OPEFB. Adsorption experiments were carried out to determine the effects of initial dye concentration 100-300 mg/L, contact time, pH 2-10 and temperature 30°C-60°C. The optimum conditions were achieved at adsorbent dosage, pH, initial dye concentration and temperature of 0.2 g/200 mL, 6, 100 mg/L and 60°C, respectively with 91.44% of MB removal. From isotherm study, the Freundlich isotherm model fitted the adsorption data very well owing to its higher value of correlation factor (R2 = 0.9352), compared to Langmuir model (R2 = 0.8682). The Langmuir maximum monolayer capacity, qm was estimated at 167.2 mg/g. The results from the kinetic study showed that the MB adsorption followed a pseudo-second-order kinetic model (R2 = 0.9216-0.9581). The adsorption of the MB dye onto OPEFB activated char was an endothermic and spontaneous process with H°, G° and S° values of 58.379 kJ/mol, -0.70505 kJ/mol and 194.955 J/molK, respectively. The obtained results suggest that the OPEFB char could be a promising candidate as an adsorbent for MB removal. [ABSTRACT FROM AUTHOR]

The accumulation of different kinds of synthetic dyes in the environment poses a global ecological threat. White rot fungi play an important role in dye decolorization, but there is a scope for developing improvised dye decolorization methods and analysing its mechanism. In the present study, we used free and immobilized biomass (on two solid synthetic supports) of the Trametes versicolor (CB8) strain to decolorize five of the most utilized synthetic dyes belonging to three different classes, namely triphenylmethane (Brilliant Green, Crystal Violet), azo (Congo Red, Evans Blue), and anthraquinone (Remazol Brilliant Blue R) in a wide range of initial concentration (100, 200, 300 and 400 mg·L-1). The best removal (more than 90%) was observed for three dyes (Evans Blue, Remazol Brilliant Blue R, Crystal Violet) in case of free and immobilized biomass at all concentrations whereas immobilization did not prove beneficial for elimination of Congo Red. The UV-Vis spectrum analysis proved the dye decolorization was performed by biodegradation method. Through the desorption study, the individual participation of physical sorption in the decolorization of dye was investigated. It was concluded that biochemical decolorization played a major role in dye decolorization. Further research is indicated to optimize the degradation process by immobilized CB8 strain. [ABSTRACT FROM AUTHOR]

Investigations were carried out for the removal of Crystal violet (CV) dye from an aqueous solution using sewage sludge as adsorbent prepared after heating at 900°C. X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analysis were used for the characterization of sludge. The results of batch studies showed the values of optimum parameters such as contact time (180 min), adsorbent dose 10 g/L and temperature (30°C). The removal efficiency was found to be about 98.4% and the equilibrium adsorption capacity of Crystal violet dye was 9.508 mg/g. The Freundlich, Langmuir, Redlich–Peterson, and Dubinin–Radushkevich isotherms were employed to evaluate the equilibrium data from batch adsorption studies. Kinetic data were analyzed using kinetic models such as; pseudo-first-order, pseudo-second-order, intraparticle diffusion. Nonlinear regression method and error functions namely; R², sum of error squares, G², HYBRID, Marquardt’s percent standard deviation, root mean square error and mean square error were used to determine the best fitted model. Freundlich isotherm model best fitted the data showing multilayer adsorption of CV dye on activated sludge while kinetic studies of CV dye were well described by pseudo-second-order model. Thermodynamic characteristics for dye adsorbent system indicated that the adsorption process was spontaneous and endothermic in nature. Results show that activated sludge can be effectively used as low-cost adsorbent for the removal of cationic dyes from aqueous solution. [ABSTRACT FROM AUTHOR]

A novel nanocomposite adsorbent of nZVI/(Fe–Mn) binary oxide/bentonite (IFMB) was developed in our study. In this paper, the adsorption behaviour of Reactive Yellow 145 (RY-145) dye from aqueous solution of IFMB was presented. The batch experimental results indicated that contact time, initial dye concentration and especially the initial pH value of the solution play important roles in the adsorption process of RY-145 onto IFMB. The adsorption efficiency was high and relatively stable in the range of pH < 7.0, when increasing the pH from 7.0 to 10.0, the adsorption efficiency decreased rapidly and at pH 11.0 there is almost not adsorption. The pseudo-secondorder kinetics model was suitable for describing the adsorption kinetic data. The adsorption isotherm data was agreed well with the Langmuir model and the maximum adsorption capacity was as high as 338.9 mg·g–1 at 30°C. In addition, IFMB could be easily regenerated by alkaline elution, and the adsorption efficiency after the fifth adsorption–desorption cycle was 74.5% of the one after the first adsorption–desorption cycle. These results suggested that IFMB is a promising candidate for azo dye wastewater treatment. [ABSTRACT FROM AUTHOR]

This study investigated the potential of eggshell powder (EGP) on the removal of two important cationic dyes namely: Methylene Blue (MB) and Crystal Violet (CV), by batch adsorption experiments. Characterization of eggshell functional groups was investigated using Fouriertransform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and X-ray diffraction (XRD). The experiments were carried out by varying the adsorbent dosage, pH, contact time, temperature and initial dye concentrations. The study showed that all parameters affected the removal of the dyes by the adsorbent. Pseudo-second-order kinetics model best represented the experimental data for EGP-MB, while pseudo-first-order best explained EGP-CV system. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models were used to describe the adsorption process and of all these isotherm models, the Langmuir model best represented both adsorbate–adsorbent systems (EGP-MB and EGP-CV) giving maximum adsorption capacities (Qmax) of 122.510 and 118.610 mg g−1 respectively at 35°C. Thermodynamics studies showed that both adsorption systems are spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

In this study, natural and available biomass of a raw pinecone (P), cypress fruit (C), and oak cupule (O) powders were used as adsorbents for the removal of crystal violet (CV) from aqueous solution. Techniques of FT-IR, SEM, and XRD were employed for the characterization of biomass materials before (P, C, and O) and after adsorption (PCV, CCV, and OCV). Results show that the adsorption capacity of CV is influenced by parameters of dosage, particle size, initial concentration, contact time, pH, and temperature. The best uptake of CV ranged between 80.64 and 105.24 mg/g by P, C, and O under optimal conditions of: 0.07 g O, and 0.05 g P and C, 60 mg/L initial concentration of CV, 80 min. Contact time for O, and 100 min. for C and O, pH 7.0 for P, and pH 9.0 for C and O. The fit to the pseudo-second-order kinetics model suggests chemical adsorption onto P adsorbent. While the fit to pseudo-first-order kinetic model suggests physical adsorption onto C and O adsorbents. The Langmuir isotherm model fitted the experimental data with a maximum adsorption capacity of 80.84, 105.24, and 90.91 mg/g by P, C, and O, respectively. The study revealed that low-cost and eco-friendly biomasses of P, C, and O posed a very good potential as adsorbents for CV dye removal. [ABSTRACT FROM AUTHOR]

Our study aims to prepare a novel composite adsorbent via physical mixing process by using synthesized alumina from alum with acid activated clay (Alumina/H+ Clay) and estimate their efficiency for malachite green dye (MG) adsorption. The characterization of Alumina/H+ Clay composite was performed using various analyses techniques such as XRD, FT-IR, SEM, surface area analysis (BET), and pHpzc. Furthermore, the effects of pH dye solution, adsorbent mass, initial concentration, and contact time on the adsorption process were investigated. Our results demonstrated that the prepared Alumina/H+ Clay composite is a mesoporous material with a pore volume and specific surface area of 0.58 cm³ /g, 89.02 m2 /g respectively. The experimental data fit well with Langmuir isotherm with a maximum adsorption capacity of 243.06 mg/g. In addition, the kinetic parameters showed that the adsorption of MG dye followed the pseudo-second-order model. The obtained thermodynamic parameters indicated that the adsorption occurred spontaneously at different temperatures and the process was endothermic. Therefore, this study demonstrated that prepared Alumina/H+ Clay composite is an excellent adsorbent for MG dye and it could be used as an effective and promising adsorbent material for dyes. [ABSTRACT FROM AUTHOR]

Zn(II) ion-imprinted polymer [Zn(II) IIP] was prepared by following precipitation polymerization using acrylonitrile as functional monomer, N,N’-Methylenebis(acrylamide) as cross-linker and potassium persulfate as thermal initiator. Furthermore, 8-hydroxyquinoline was used as complexing agent for Zn(II) ions that was also employed for functionalizing the Zn(II) IIP. After the leaching of the Zn(II) ions, an ion-imprinted polymer [Zn(II) IIP] was obtained which showed high tendency of selective recombination with the Zn(II) ions. The equilibrium and kinetic adsorption studies of Zn(II) ions on both Zn(II) IIP and non-imprinted polymer (NIP) were carried out at different temperatures. Scanning electron microscopy and Fourier-transform infrared spectroscopy was carried out for evaluating the morphology and the various functional groups present in the molecular structure. The specific surface area was determined to be 337.30 m² g–1 for NIP whereas 439.54 m² g–1 for Zn(II) IIP by applying the Brunauer–Emmett–Teller model to the nitrogen adsorption isotherm. Similarly, the pore-size distribution was analyzed using the Barrett–Joyner–Halenda model and t-plot method confirming the surface texture of both adsorbent to be mesoporous in nature. The isotherm models of Langmuir, Freundlich, and Dubinin–Radushkevich were used to analyze the adsorption equilibrium data. It was revealed that the adsorbents surface has heterogeneous nature as Freundlich isotherm was more closely followed by the adsorbents. The maximum adsorption capacity was found to be 3.75 mg g–1 for NIP whereas 6.82 mg g–1 for Zn(II) IIP. The relative selectivity coefficient K’ for Zn(II)/Co(II), Zn(II)/Cu(II), Zn(II)/Ni(II) and Zn(II)/Pb(II) metal ion pairs is determined to be 24.827, 1.273, 3.931 and 2.437, respectively. The adsorption kinetic data followed pseudo-first-order model with respect to R² values suggesting physical nature of adsorption. Electrokinetic study was also performed for understanding the nature of interaction between adsorbate and adsorbent which was validated on the basis of Grahame and pK-1 model depicting the surface electrostatic potential nature of charges. Van’t Hoff plot was employed on the thermodynamic data of adsorption for attaining the change in entropy (ΔS) and enthalpy (ΔH), in addition to the Gibb’s free (ΔG) change as well. [ABSTRACT FROM AUTHOR]

The aim of current research was to remove methyl violet dye (MV) from wastewater by using eggshells. Batch experiments were performed to investigate the effect of different parameters, such as solution pH, adsorbent dose, contact time, dye concentration, and temperature, on adsorption of methyl violet dye. There was maximum, that is, 88% removal of methyl violet dye from wastewater at optimized conditions (i.e., pH 7, 0.6 g adsorbent dose, 10 min contact time, 40 ppm dye concentration, and 10°C temperature). Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to examine the adsorption process. Pseudo-second-order model was the best fit model for adsorption process with (R² = 0.9916). Adsorbent was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy techniques. Adsorption isotherms such as Langmuir and Freundlich were studied and investigated. Langmuir isotherm model was best followed by adsorption process (R² = 0.9938). Thermodynamic parameters (i.e., ΔH, ΔG, and ΔS) were also investigated and results showed that process was spontaneous and exothermic. Applicability of developed practice with tap water was 82%. [ABSTRACT FROM AUTHOR]

Current study focused on Coriandrum sativum seeds as a green low-cost biosorbent for crystal violet dye removal from wastewater. Adsorption parameters (such as pH, adsorbent dosage, contact time, adsorbate concentration, and temperature), isotherm models (i.e., Langmuir, Freundlich, and Dubinin--Radushkevich isotherm models), kinetic models (i.e., pseudo-first-order, pseudo-secondorder, and intraparticle diffusion models), and thermodynamics study has been studied and investigated. At optimized conditions, that is, pH 7, adsorbent dose of 0.3 g, contact time 50 min, dye concentration of 30 ppm, and 10°C temperature, the maximum dye removal was 75%. Experimental data fitted best to Freundlich isotherm and pseudo-second-order kinetic model. Computed ΔG and ΔH values adjusted adsorption process to be spontaneous and exothermic in nature. Maximum adsorption capacity in current process was found to be 1.8098 mg/g and applicability of established practice with tap water was 72% and regeneration study showed that nearly 71% of adsorbent (Coriandrum sativum seeds) was recovered which confirmed the effectiveness of Coriandrum sativum seeds for decontamination of crystal violet dye. [ABSTRACT FROM AUTHOR]

In this study, biochar (BC) was prepared from okara (BC-OA) and applied to the adsorption of methylene blue (MB), neutral red (NR) and malachite green (MG) in aqueous solutions. Different analytical techniques characterized the structure and surface chemical properties of the adsorbents. The results were used to analyze the adsorption interaction between BC-OA and contaminants, and a single factor test determined the optimal adsorption conditions. The results showed that the removal ratio increased with the solution pH value, indicating that the alkaline condition was more conducive to adsorption. In the adsorption--desorption regeneration experiment, the adsorption performance of BC-OA decreased slightly, reflecting the stability of BC performance. The Langmuir isothermal adsorption model could describe the adsorption process better, with correlation coefficient (R²) of 0.9565, 0.9870 and 0.9825, and qm of 294.04, 583.50 and 1,058.36 mg/g, respectively. The fitting results of the pseudo-first-order kinetic model show that chemisorption controls the whole adsorption process. In this work, the adsorbent (BC) was prepared by using okara biomass material. The experimental results show that the adsorption effect is good, the adsorption speed is fast, the preparation process is simple and environmentally friendly, and BC can be used as a new type of high-efficiency adsorbent, which can expand its application in dyes wastewater treatment. [ABSTRACT FROM AUTHOR]

The need for alternative wastewater treatment methods with wide scale applicability led to a new area of interest: the green technology, which dealt with technological interventions for environmental sustainability by focusing on minimizing pollution and use of non-renewable resources. Crystal violet is typical cationic dye which belongs to an important class of commercial dyes and it acts as a mitotic poison, potent carcinogen and a potent clastogene, promoting tumor growth in some species of fish. Therefore, there is an important need to develop eco-friendly and costeffective treatment methods, which can effectively remove this dye from industrial wastewaters. Modified clinoptilolite was used in this study as a low-cost adsorbent to evaluate its ability to remove crystal violet dye from effluents. The influence of initial dye concentration, sorbent dose, adsorption time and temperature has been analyzed in detail with crystal violet dye. Fit of the sorption experimental data was tested on Langmuir, Freundlich and Temkin isotherm models. It was found that the Langmuir and Temkin models fitted well. The present study demonstrated that modified clinoptilolite has the potential of application as an efficient sorbent for the removal of crystal violet dye from aqueous solutions. [ABSTRACT FROM AUTHOR]

Reactive Yellow 42 (RY 42) dye is a synthetic azo dye which is very important and also is widely used industries. Therefore, the aim of this study was to synthesize silica nanoparticles and to investigate the equilibrium, kinetics and thermodynamics of the removal of RY 42 dye by these nanoparticles from aqueous solutions. This study was performed on a laboratory scale. First, silica nanoparticles were fabricated with cationic surfactant and then field-emission scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy techniques were used to evaluate its properties. Also, the effect of various parameters such as pH (3-11), nanoparticle dose (0.1-0.6 g/L), contact times of 10-120 min and initial dye concentrations (50-10 mg/L) in adsorption reaction were investigated. Finally, the kinetics, isotherms and thermodynamics of the reaction were determined. According to the results of this study, as the RY 42 dye concentration increased, the removal rate decreased, resulting in lower efficiencies. Also, the highest removal percentage of RY 42 dye at pH = 3, initial concentration of 10 mg/L, adsorbent dosage of 0.1 g/L and contact time of 120 min was occurred and was equal to 94.1%. The isotherm and kinetics of the adsorption reaction followed the Langmuir model and the pseudo-second-order model, respectively. Free energy changes of Gibbs (ΔG), enthalpy changes (ΔH) and entropy changes (ΔS) were obtained in this study. Since (ΔG) is negative, (ΔH) is positive, and (ΔS) is positive, the process is endothermic and spontaneous. Therefore, the adsorption process by silica nanoparticles is a suitable option for removal of RY 42 dye from aqueous and wastewater solutions and can be used as an efficient and suitable adsorbent. [ABSTRACT FROM AUTHOR]

In this study, the synthesis of an easily synthesized, non-toxic and inexpensive material and its use in dye removal have been demonstrated. The synthesis of novel material, tin(IV) chelate compound, was carried out using simple and inexpensive Schiff base ligands. This novel material was used for the first time as an adsorbent to remove murexide dye from a model aqueous solution. 1H-NMR, 13C-NMR, Fourier-transform infrared spectroscopy, MS, and elemental analysis techniques were performed for the characterization of the new tin-based adsorbent and the open structure of the compound was proposed. Murexide dye removal from a model aqueous solution was performed by examining five important factors of adsorption. Batch adsorption is the easiest way to remove dyes at a low cost. The optimum parameter values to maximize the adsorption efficiency were obtained at pH 3, 100 mg/L dye concentration, 20 min of contact time, 40 mg adsorbent dose, and 25°C. The highest adsorption recovery value and the adsorption capacity found at optimum parameters were 99.00%, and 248.8 mg/g, respectively. Three adsorption isotherms were calculated at 25°C. The highest R2 value was found at 0.99 for the Langmuir isotherm model, the adsorption kinetic obeyed the pseudo-second-order kinetics, and the thermodynamic data suggested a spontaneous and exothermic process. [ABSTRACT FROM AUTHOR]

In this study, new biochar was produced from watermelon peel residues by dehydration process. The ability of the newly generated biochar-S to remove Cu2+ ions from aqueous solutions was examined. Watermelon peel was used to make biochar-S, which was made by dehydrating by boiling with 50% sulfuric acid. Scanning electron microscopy, Brunauer-Emmett-Teller, Fourier-transform infrared spectroscopy, Barrett-Joyner-Halenda, differential scanning calorimetry, thermal gravimetric analysis and energy-dispersive X-ray analysis studies were used to characterize the biochar-S. The ideal pH for Cu2+ ion adsorption was found to be 5.6. 1.0 g L-1 of biochar-S as an adsorbents dosage with Cu2+ ions beginning concentration of 200 mg L-1 had the maximum Cu2+ ions removal percentage of 78.33%. The maximal adsorption capacity (Qm) of biochar-S was 151.52 mg g-1. Isotherm models such as Dubinin-Radushkevich, Langmuir, Temkin, and Freundlich were used to analyze the experimental data. Furthermore, the data of these isotherm models were investigated using several error function equations (average percentage errors, hybrid error function, Chi-square error (χ2), sum of absolute errors, root mean square errors, and Marquardt's percentage standard deviation). The biochar-S experimental data was best suited by the Freundlich isotherm model. Pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were used to assess the kinetic data. The adsorption rate was predominantly influenced by a pseudo-second-order rate model that had a high correlation (R2 > 0.99). The primary mechanism of Cu2+ ion adsorption by biochar-S consists mostly of surface precipitation by the formation of insoluble copper compounds in an alkaline state and ion exchange with exchangeable cations in biochar such as aluminium, silicon, and calcium ions for copper ions. The findings suggest that biochar-S is a promising adsorbent for the adsorption of Cu2+ ions and that it can be employed repeatedly without losing adsorption efficiency. [ABSTRACT FROM AUTHOR]

New adsorbents of DSAC@ZIF-8 (0.05:0.6) and DSAC@ZIF-8 (0.05:0.6) were prepared using date seed activated carbon (DSAC) loaded at zeolitic imidazolate framework-8 (ZIF-8). The obtained adsorbents DSAC@ZIF-8 (0.05:0.6) and DSAC@ZIF-8 (0.1:0.6) were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, nitrogen adsorption/desorption tests at 77 K revealed the surface area to be 460.23 m²/g for DSAC@ZIF-8 (0.1:0.6). This material showed a high affinity for Gentian violet (GV) uptake from aqueous solutions: the maximum sorption capacity reached 638.99 mg/g at pH 9.0 and ambient temperature. Uptake kinetics and sorption isotherms were obtained and modelled using conventional and simple equations: the best results were respectively obtained with the pseudosecond-order rate equation and the Langmuir equation. The activation energy of absorption also was measured to be 15.87 kJ/mol, showing that the process of chemisorption is included. The distribution coefficient was obtained at different temperatures and the thermodynamic parameters have been calculated: the sorption is endothermic, spontaneous (especially at high relative temperature), and contributes to increasing the entropy (randomness) of the system. HCl (1.0 M) was used for GV desorption from DSAC@ZIF-8, and the sorbent could be efficiently recycled for a minimum of three sorption/desorption cycles. Therefore, sorbent could serve as a promising adsorbent for GV removal from industrial wastewater. [ABSTRACT FROM AUTHOR]

Water permeability and dye rejection were considerably enhanced when mesoporous silica nanosphere (MSN) was added to the membrane matrix. The dry/wet phase conversion approach was used to create all membranes. The effect of MSN concentration (0%–8% wt.%) on the behavior of the PSF-UF membrane in the presence of polyvinylpyrrolidone (PVP) as a producing-pore agent was examined. When the MSN level was increased to 6 wt.%, the rejection of Crystal violet dye rose continuously. Scanning electron microscopy was utilized to analyze the morphological characteristics of ultrafiltration (UF) membranes. Polysulfone (PS)/PVP/SiO2 (6%), for example, experienced high dye rejection (88.3%). The membrane permeability dropped from 415.9 L/ m² h for PS/PVP to 122.7 L/m² h for PS/PVP/SiO2 (6%) membrane when the MSN concentration increased to 6 wt.%. Only water could flow through the hydrophilic membrane on the feed side, resulting in a high-quality stream of water on the permeate portion, making the membrane suitable for the treatment of industrial effluent. The membrane’s performance was improved by the addition of polyvinylpyrrolidone. [ABSTRACT FROM AUTHOR]

Value was added to an agricultural waste of Moringa oleifera pod husk (MOPH) by modifying the biomass with maleic anhydride (MA) to produce a cellulose-based adsorbent (MA-MOPH) that could remove crystal violet (CV) and methylene blue (MB) in single and binary dye systems. The biosorbent was characterized by Fourier-transform infrared spectroscopy, X-ray diffractometry, and thermogravimetric analysis. In single dye systems, the adsorption capacities of MA-MOPH were 378.50 mg g–1 for CV and 545.36 mg g–1 for MB. These values were obtained at 25°C, in solution at pH 8, at 180 and 60 min for CV and MB, respectively. The adsorption capacity of MA-MOPH for CV and MB was lower in the binary system due to competition between the two dyes. However, its adsorption capacity was higher than other adsorbents used to extract CV and MB in single dye systems. Overall, the adsorption process was well explained by the pseudo-second-order kinetics model and Langmuir isotherm model. MA-MOPH retained a satisfactory adsorption capacity in a repetitive adsorption process using the acetic acid solution as the desorbing agent. Therefore, MA-MOPH could be used as an economical biosorbent for the simultaneous removal of cationic dyes in water. [ABSTRACT FROM AUTHOR]

In this study, new magnetic activated carbon (Fe3O4-AC) was synthesized from activated carbon which was obtained from the inner bark of acorn with the activation of H3PO4 and its effectiveness in Methyl violet (MV) removal from aqueous solutions was investigated. Characterization of the samples was done by scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. In MV adsorption on Fe3O4-AC, pH (2-10), initial MV concentration (25-150 mg/L), amount of adsorbent (0.1-1.0 g), adsorption time (5-180 min) and temperature (298-318 K) adsorption parameters were investigated. The compatibility of MV and Fe3O4-AC adsorption with Langmuir and Freundlich isotherm models was investigated, and it was determined that Langmuir isotherm which proposed single-layer adsorption, was the most compatible isotherm for adsorption at three different temperatures. The highest maximum adsorption capacity with Langmuir isotherm was obtained as 156.25 mg/g at 298 K. The pseudo-second-order kinetic model had a better fit with the best correlation to the kinetic data. Thermodynamic parameters (G°, H° and S°) were calculated from the Van't Hoff plot of lnKd. 1/T in order to discuss the removal mechanism of MV. Then, in MV removal process under different conditions, experimental results were compared with the artificial neural network model. [ABSTRACT FROM AUTHOR]

In this study, garlic straws (GS) from agricultural by-products were chemically modified by sodium hydroxide and citric acid to yield potential adsorbents for the removal of ionic dyes. Firstly, the physical and chemical properties of obtained adsorbents were characterized by component analysis, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. Then the cationic dye crystal violet (CV) and anionic dye Congo red (CR) were applied to evaluate the adsorption capacity of adsorbents under different conditions such as initial solution pH (2–12), adsorbent dose (0.5–10 g/L), initial dye concentration (0.1–6 g/L) and contact time (up to 120 min). Results showed that sodium hydroxide and citric acid treatments could enhance the adsorptions of CV and CR probably through increasing the hydroxyl groups and carboxyl groups on the surface of GS. The maximum adsorption capacities of CV and CR on modified GS at 308.15 K were 63.69 and 998.3 mg/g, respectively. Furthermore, a kinetics study revealed that the adsorption processes could be described by the pseudo-second-order kinetic model. Thermodynamic parameters indicated that the adsorption processes were spontaneous and endothermic. Generally, these results confirmed that sodium hydroxide and citric acid treatments were effective methods to improve the adsorption capacities of GS for ionic dyes. [ABSTRACT FROM AUTHOR]

The sodium functionalized ultrasonic-diatomite (U-D-Na) was used as an adsorbent to remove phosphorus from an aqueous solution. After simple ultrasonic purification, diatomite was functionalized by the cheap NaCl reagent to prepare U-D-Na. The microstructure and properties of U-D-Na were achieved by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, Fourier-transform infrared spectroscopy and thermogravimetry/differential scanning calorimetry. The effect on the contact time, the temperature, the dosage of adsorbent, pH and the initial concentration of phosphorus were investigated during the adsorption kinetics and equilibrium studies. The U-D-Na exhibited that the adsorption efficiency reached more than 90% at optimal conditions. Multiple cycles of adsorption and desorption tests showed that the adsorbent performed good renewability. The experimental values were coincidence with the pseudo-second-order kinetic model and the Langmuir isotherm model. Also, thermodynamic parameters such as the ΔG°, ΔH° and ΔS° illustrated that the adsorption process is essentially exothermic and spontaneous. The results indicated that a promising application prospect for water pollution management by U-D-Na [ABSTRACT FROM AUTHOR]

Methylene blue (MB), as a thiazine cationic dye, has been commonly used in dye houses and textile industries. Long exposure to MB can cause health problems such as shocks, hypertension, anemia, nausea, serotonin syndrome, red blood cell breakdown, tissue necrosis and jaundice. The aim of this study was to optimize methylene blue (MB) removal from aqueous solutions by Saccharomyces cerevisiae using the response surface methodology. The influence of various factors including initial dye concentration (10–100 mg/L), solution pH (4–10), reaction time (10–60 min), and S. cerevisiae dosage (0.2–1.5 g/L), was investigated on the process. According to the findings, the obtained levels of MB removal were varied in the range of 36% to 96%. The maximum removal of MB (99.16%) occurred at pH 9.35, the reaction time of 50.81 min, dye concentration of 14.37 mg/L, and S. cerevisiae dose of 1.32 g/L. The results showed that the code of A with the coefficient of –11.41 was the most important factor in the removal process. The AD and D2 with the coefficient of –11.30 and –7.76 had the maximum interaction impact, and the maximum square impacts on the process, respectively. The removal rate of MB was directly correlated with reaction time and S. cerevisiae dose. It can be concluded that S. cerevisiae can be considered as a low-cost adsorbent for the removal of MB in the aqueous media. [ABSTRACT FROM AUTHOR]

In this study, loofah was used to remove organic dyes (crystal violet, methylene blue, and basic fuchsine) from an aqueous solution by biosorption. The effects of operating parameters, such as contact time, initial pH, dyes concentration, size of biosorbent and temperature, on the discoloration yields were evaluated. The experimental results revealed that the highest removal efficiencies of crystal violet, methylene blue, and basic fuchsine were 99.5%, 98.66%, and 85%, respectively, at the optimum conditions (operating time of 60 min, initial pH (6.92 for the crystal violet, 6.60 for methylene blue and 8.53 for basic fuchsine), dyes concentration of 6 mg/L, size of loofah squares S = 16 cm2 and temperature of 60°C). The structural characterization of the loofah after biosorption of dyes using Fourier-transform infrared spectroscopy analysis showed an intensity reduction of the characteristic peaks of the hydroxyl groups and the apparition of novel characteristic peaks of amine groups indicating thus the fixation of dyes on loofah. Equilibrium isotherms models showed that the Langmuir isotherm model gives the best fit for the experimental data with the best regression coefficient R2 > 0.99. Adsorption kinetics showed that the biosorption followed a pseudo-secondorder reaction. Thermodynamic study indicates an endothermic process with physical nature. [ABSTRACT FROM AUTHOR]

Nowadays, industrial effluent containing textile dyes is considered a major environmental concern. Crystal violet (CV) is one of the vital textile dyes of the triphenylmethane group and it is known for its mutagenic and mitotic poisoning nature so it must be treated. This study aims to evaluate the adsorption potential of peanut husk (PH) towards CV dye removal. Adsorption studies are conducted to study the effects of different parameters on adsorption such as particle size of adsorbent (105, 210, and 500 mesh sizes), initial dye concentration (5-100 mg/L), contact time (5-120 min), pH (1-11), temperature (0-60°C), and adsorbent dosage (0.1-1.0 g). Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models are applied to experimental data for the determination of the nature of adsorption. The kinetic studies have been carried out using the pseudo-first-order, pseudo-second-order, and intra-particle diffusion model for adsorption of CV on PH. Thermodynamic parameters such as changes in Gibb's free energy (G), enthalpy (H), and entropy (S) are also determined. Optimum conditions for maximum removal of toxic CV dye from wastewater on PH includes 210 mesh size, 100 ppm initial dye concentration with 10 min contact time at temperature 30°C using 0.1 g of adsorbent. Alkaline medium favors adsorption of CV onto the surface of PH and its maximum removal is observed at a pH of 8. These optimum conditions result in 90% removal of CV dye from aqueous solution and the maximum adsorption capacity found out was 20.95 mg/g. Applicability of this developed procedure with tap water is 83.16% indicating that the PH is a promising adsorbent for the removal of cationic CV dye from the aqueous solution. [ABSTRACT FROM AUTHOR]

In this study, the modified 13X zeolite by copper nanoparticles (copper nanoparticles were coated on a bed of 13X), was used as an adsorbent for adsorption of fenitrothion from aqueous solutions in a batch process. The results indicated that the maximum adsorption rate was 97% (with values of 6, 0.2 g, 20 min, and 20°C for pH, adsorbent mass, contact time, and temperature respectively). Kinetic studies showed that the pesticide adsorption process could be well described using the pseudo-second-order (Type 1) kinetic model. Langmuir-Type 1 isotherm, as well, covers the equilibrium data with a maximum absorption capacity of 63.29 mg/g for modified 13X. The results of the tests showed that the temperature increase has a negative effect on the removal efficiency. The thermodynamic parameters showed that the adsorption of fenitrothion pesticide on modified 13X in the studied conditions was spontaneous and exothermic. [ABSTRACT FROM AUTHOR]

The goal of this research is to describe a promising dye elimination platform based on covalent coordination framework (CCF) nanoparticles. For this purpose trigonal prismatic molecular building block was prepared by employing 4-hydroxybenzoic acid and Cr(III) salt then the polymerization was performed based on the Mannich reaction using phenylenediamine as a linker. Prepared nanostructure was characterized using Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, and elemental mapping techniques. According to the BET results, the nanoparticles showed a surface area of 13.6 m² g–1. Moreover, based on the XRD and FE-SEM results the nanoparticles have low crystallinity with a diameter between 15–50 nm. The prepared CCF was employed for the removal of five carcinogenic dyes including; Crystal violet, Malachite green, Methylene blue, Nile blue, and Sunset Yellow. Experimental results showed that maximum removal was obtained at a pH of 9 with a shacking time of 20 min. Kinetic study showed that dye adsorption followed the pseudo-second-order model as well as the dye adsorption behavior followed the Langmuir isotherm model. A 95% desorption of adsorbed dyes was observed with a mixture of 1 mL ethanol and HNO3 solution with a concentration of 0.1 mol L–1. Moreover, the reusability experiment showed after 3 cycles of sorption and desorption the removal percentage decreased only 5%–10% that confirmed the nano-polymer is a good candidate to be used as a reusable adsorbent for water purification. [ABSTRACT FROM AUTHOR]

Bio-sorbents have arisen as prospective remediation substantial for the exclusion of colorants. Rice husk, a generally accessible agricultural waste material in Pakistan, was chosen as an adsorbent material for the elimination of synthetic CV tint from a watery solution. The adsorption revisions of mutagenic CV tint from watery solution have been conducted on untreated rice husk by adjusting diverse parameters like adsorbent particle size (105, 210, and 500 mesh sizes), initial dye concentrations (300–450 mg/L), contact interval (5–120 min), pH (1–11), temperature (0°C–50°C) and adsorbent dosage (0.1–1.0 g). Freundlich, Langmuir, and Dubinin–Radushkevich (D–R) adsorption lines were analyzed utilizing the experimental statistics. Freundlich and D–R isotherms fit best with experimental data having R² values 0.998 and 0.999, respectively. The pseudo-second-order shows excellent agreement out of all the adsorption kinetics because R2 = 1. Thermodynamic parameters (variation in Gibb’s free energy (ΔG°), variation in enthalpy (ΔH°), and variation in entropy (ΔS°)) were also debated and verified. The results indicate that the adsorption process shows feasibility, exothermic behavior, and a positive value of entropy (ΔS°) indicates that randomness prevails the adsorption process in this study. These optimum conditions results in 90.24% of crystal violet dye removal and the maximum adsorption capacity found out was 53.00 mg/g. Applicability of maximum conditions with tap water results in 80.6% removal of CV dye which indicates that rice husk might be able to recycle at a low price and proved effectual adsorbent material for the elimination of crystal violet tint from discarded water. [ABSTRACT FROM AUTHOR]

This study aims to investigate the potential of integrating water treatment sludge and rice husk (RH) as a low-cost adsorbent for Remazol red (RR) dye removal. In the first stage of the study, a comparison was made for thermally-treated conventional water treatment sludge and desalination water treatment sludge (DWTS) in terms of the characteristics and potential of the adsorbents in removing RR dye. DWTS seemed to be a better adsorbent and was selected to be integrated with RH for better properties and performance. The RH was treated with sodium hydroxide solution. The integrated adsorbent (RH-DWTS) was characterised using scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The performance of the adsorbents to remove RR dye was evaluated by carrying out batch adsorption experiments at different adsorbent dosages, initial dye concentrations, and pH. The highest removal rate of RR (81.2%) was achieved through adsorption using RH5%-DWTS at 1 g/L adsorbent dosage, 30 mg/L initial dye concentration, and pH 3. The adsorption study fitted well the Freundlich isotherm model, indicating heterogeneous adsorption. The results of this study can provide an essential pathway for developing sustainable and cost-effective dye wastewater treatment in the future. [ABSTRACT FROM AUTHOR]

This study centers on crystal violet removal from raw water on surface of Cedrus deodara sawdust. Main objectives of this study are to investigate the potential of Cedrus deodara sawdust for removal of toxic crystal violet dye and to stimulate the best experimental conditions. Adsorption parameters, isotherms, kinetic equations, and thermodynamics have been studied and discussed. Experiments were performed to investigate the effects of various parameters, that is, size of adsorbent, pH, adsorbent dose, contact time, dye concentration and temperature on dye exclusion. Isotherms, that is, Langmuir, Freundlich and Dubinin-Radushkevich isotherms and kinetic models, that is, pseudo-first-order, pseudo-second-order and intraparticle diffusion models have been applied and discussed. Thermodynamic parameters, that is, change in Gibbs free energy, enthalpy and entropy have also been determined. Maximum amount of dye (99.21%) has been removed at optimized conditions, that is, 210 mesh size, 50°C temperature, pH 12, 0.4 g adsorbent, 20 ppm adsorbate concentration with contact time of 30 min. Data fits best to Langmuir isotherm and process obeys pseudo-second-order kinetics. Calculated free energy and enthalpy indicates spontaneity and endothermicity of the process. Applicability of developed procedure with tap water is 92% indicating that Cedrus deodara is an auspicious adsorbent for crystal violet removal from water. [ABSTRACT FROM AUTHOR]

The present investigation reports the decolorization and subtraction of harmful Crystal violet (basic) dye from the aqueous solution by adsorption on wheat bran (WB). Experiments are performed by monitoring various factors, for instance, granular size of adsorbent (105, 210 and 500 mesh sizes), pH (1-11), duration of contact (5-120 min), amount of wheat bran (0.1-1.0 g), initial dye concentration (300-550 ppm) and temperature (0°C-60°C). The surface study of wheat bran was investigated by Fourier-transform infrared spectroscopy and scanning electron micrograph. The calculations reveal adsorption of Crystal violet (CV) at the surface of WB is directly proportional to exposure time, amount of WB, initial dye concentration and temperature. Three isotherm equations were applied, Freundlich, Langmuir and Dubinin-Radushkevich isotherms, to explore experimental data. The computations indicate that data fits efficiently with the Langmuir model. Optimum uptake capacity was calculated, that is, 116.6 mg g-1. Moreover, the adsorption data were used to calculate the rate constants of pseudo-first-order, pseudo-second-order, liquid film diffusion and intraparticle diffusion. The regression value (R² = 1) was obtained to confirm the good correlation with pseudo-second-order kinetic equation rather than others observed kinetic equations. To figure out the nature of adsorption, the free energy of adsorption of CV on WB (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined. The numerical results of ΔG, ΔH and ΔS show that adsorption of CV on WB was feasible, spontaneous and endothermic in nature. The maximum removal efficiency of wheat bran towards Crystal violet, that is, 86.57% is observed at optimum conditions, that is, pH 2, 0.6 g of WB, 30 min of contact time and 400 ppm of initial dye concentration. It can be concluded from the experimental results that WB could be effectively employed as a biosorbent for the removal of CV. [ABSTRACT FROM AUTHOR]

This study presents the consecutive modification of orange peel (OP) by NaOH and sodium dodecyl sulfate (SDS) for simultaneous elimination of basic dyes from the binary system and modeling the adsorption process using an intelligent tool. The natural and modified biosorbents were characterized by variety of analyses such as: field emission scanning electron microscopy with energy dispersive X-ray, N2 physisorption and Fourier transform infrared spectroscopy techniques. The influence of various variables on dye removal like pH, the quantity of biosorbents, dyes concentration, contact time, and temperature in the binary system were investigated and optimized by an artificial neural network (ANN) model as an intelligent tool. The optimum quantity of the sorbent was found to be 0.30 g for orange peel (OP) and 0.25 g for NaOH-treated OP (NOP) and SDS-decorated NOP (SNOP) at pH = 7. The kinetics and thermodynamics investigations showed that the removal of dyes obeyed the pseudo-second-order kinetic model and were spontaneous and exothermic in nature. Moreover, in order to describe the mechanism of sorption process, desorption studies of dyes were carried out. The desorption percentages of methylene blue (MB) in water and HCl were found to be in the range of 1.93%-4.76% and 18.87%-28.76%, respectively; in addition, the desorption percentages of crystal violet (CV) in water and HCl were obtained to be in the range of 4.11%-7.41% and 32.84%-43.00%, respectively; which could be a recommendation ion exchange or electrostatic attachment of dyes onto biosorbents. The ANN predictions matched with the experimental data very well (0.95308 < R² < 0.99191 and 0.98335 < R² < 0.99773 for MB and CV, respectively) which indicated high accuracy of the ANN model. In addition, the relative importance of each parameter was calculated by Garson's equation. [ABSTRACT FROM AUTHOR]

Activated carbon obtained from rhizomes of black turmeric is used for the removal of industrial pollutant crystal violet dye from aqueous solution. The ash was characterized by Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy. Powder XRD pattern of the adsorbent reveals the peaks at 2q angles 26.7°, 28.6°, 30.5°, 32.8°, 34.1°, 40.64°, 43.4°, and 45.1° and pattern was found to remain unchanged after every cycle (after desorption) till eighth cycles. The calculated column adsorption capacity lower than the batch adsorption capacity. IR peaks of black turmeric ash before adsorption were observed at 1,397.33 and 1,007.13 cm--1 and after adsorption it shifted to 1,012.62 cm-1. Studies on effect of various parameters viz. dye concentration, dose of adsorbent, contact time, pH, and temperature were carried out. The dye adsorption increases with increasing pH and temperature. In higher pH ranges the adsorbent surface carries negative charge which benefits the adsorption of cationic crystal violet dye through electrostatic interaction. 100% dye removal was achieved at 40°C and above. Mechanism and kinetics of the adsorption process have also been investigated. Temkin adsorption isotherm was found best fit for adsorption process indicating the presence the energetically non-equivalent adsorption sites present on the surface of adsorbent and the adsorption of CV takes place on the more energetic adsorption site at first. Pseudo-second-order kinetics with rate constant 1.85 x 10--4 g/mg min is best fit for the adsorption process. Adsorption was found to be endothermic and processed via chemisorption. [ABSTRACT FROM AUTHOR]

Momordica charantia, or more commonly known as bitter gourd, has shown numerous health benefits, mainly decreasing the risk of diabetes. Nevertheless, the use of its inedible parts as an adsorbent toward different pollutive dyes has not been greatly explored through optimization, kinetics, and adsorption equilibrium studies. In this study, the cellulose derived from bitter gourd waste of pith and seeds (CBGW) was extracted and its adsorption characteristics were investigated with Crystal violet (CV) dye. It was found that the adsorption of CV by CBGW favors the pseudo-secondorder kinetics. Changing the medium pH has little or no effect toward CV removal, indicating that the CBGW is resilient under various pH conditions. The presence of salts also generally did not very much affect the removal of CV. When compared to many reported adsorbents, CBGW exhibited superior adsorption capacity for CV dye, as seen by its high maximum adsorption capacity of 1,565 mg g–1 (Langmuir) and 2,407 mg g–1 (Sips). Spent CBGW was able to be regenerated and reused, further adding to its value as a possible candidate in wastewater application. [ABSTRACT FROM AUTHOR]

Dimorcarpus longan ssp. malesianus var. Malesianus (Mata Kuching) leaves (MKL) show a strong affinity toward crystal violet (CV), a commonly used industrial dye. Treatment of MKL with aqueous 1.0 M NaOH solution through stirring for 2.0 h, followed by washing and drying, enhances the adsorption of CV onto the modified adsorbent (NaOH-MKL), due to the conversion of acidic functional groups to the corresponding anionic forms leading to stronger Coulombic attractions. The performance of MKL and its modified NaOH-MKL toward CV dye adsorption indicates a strong attraction of both adsorbents. Strong adsorption of CV molecules to MKL and NaOH-MKL is evidenced by changes in the Fourier transform infrared spectroscopic peaks and scanning electron microscopic images upon interaction with the adsorbate. The Sips isotherm, among the five adsorption isotherm models used in this study, is suitable in explaining the interaction of both adsorbents with CV dye molecules. The maximum adsorption capacity (qmax) of NaOH-MKL adsorbent toward CV is 391.7 mg g-1 under optimum conditions according to the Sips adsorption isotherm, which is 88% enhancement over the unmodified MKL with qmax of 208.1 mg g-1. Approach of CV dye molecules onto MKL/NaOH-MKL for adsorption is explained by the pseudo-second-order kinetics with an apparent rate constant of 6.108 g mmol-1 min-1, which is 72% increase over MKL. The superior nature of NaOH-MKL would make it an excellent sorbent for the removal of CV dye, which would thus have the potential for extrapolation toward real applications in the treatment of wastewater. [ABSTRACT FROM AUTHOR]

In this study, the adsorption of Direct Red 243 dye on clay was investigated in aqueous solutions. In batch adsorption experiments, the effects of initial pH, adsorbent dose, initial concentration, contact time, and temperature were investigated. X-ray diffraction, Fourier transform infrared spectroscopy, and surface area (SBET) analysis were used to determine the properties of the clay. Scanning electron microscopy images of the clay were obtained before and after the adsorption of the dye. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms were applied to the adsorption equilibrium, and the results indicated that the Langmuir isotherm gave the best fit to the data. The maximum adsorption capacity was 156.25 mg g–1 for Direct Red 243. The pseudo-firstorder, pseudo-second-order, Elovich, and intra-particle diffusion models were applied to the data, and the kinetic data were best described by the pseudo-second-order model. [ABSTRACT FROM AUTHOR]

Pharmaceutical compounds with a toxic nature are released into the aquatic environment and can lead to adverse effects on ecological sustainability. Thus, enhancing the separation and treatment of the toxic compounds seem necessary. In this study, uptake and removal efficiency for the adsorption of two pharmaceutical compounds, ibuprofen (IBU) and penicillin G (PEN G), from aqueous solutions by Fe3O4@GO-IL were investigated. However, the effect of main effective variables including pH, concentrations, adsorbent dosage, and contact time were investigated. Isotherm and kinetic models also were studied. The maximum IBU removal rate was achieved about 97.58 (~5 mg/g) under optimal condition, pH 6.5, adsorbent dose 0.120 g/L, contact time 60 min, initial concentration 12.7 mg/L. At a condition of pH 4, adsorbent dose 0.3 g/L, contact time 97.5 min, initial concentration 32.43 mg/L, the maximum PEN G was 95% (9.14 mg/g). The Freundlich and Langmuir isotherms and pseudo-second-order models gave the best-fit to equilibrium experimental adsorption data. The findings of the study showed that new modified magnetic nanoparticles-graphene using ionic liquid (ILMNPs) can use as a high potential, simple, rapid separation, and re-generable material for adsorption pharmaceuticals. [ABSTRACT FROM AUTHOR]

A series of new organic-inorganic nanohybrid materials were prepared by intercalating dimethylsulfoxide (DMSO) into the interlamellar space of halloysite at different contact times and DMSO/clay ratios. The X-ray diffraction and thermogravimetry/differential thermal analysis studies confirmed the insertion of DMSO into the interlayer space. The increase of the basal spacing to 1.12 nm was thus highlighted for an intercalation rate of 95%. All materials were used to remove crystal violet (CV) from aqueous media. We focused particularly on the mechanism of CV interaction with halloysitic nanohybrids by means of an infrared spectroscopy study. Understanding such an interaction is a fundamental approach for the effective use of halloysitic nanohybrids in wastewater sanitation. pH influence, kinetic, isotherm, and thermodynamic data have been examined. The equilibrium and kinetic data were appropriately adjusted, respectively, by the Redlich- Peterson, and pseudo-second-order models. The amount adsorbed by each nanohybrid depends on the intercalation rate. The larger the intercalated fraction, the better the amount adsorbed, so DMSO is involved in the CV adsorption. The mechanism would involve mainly a hydrogen bond between the electron lone pairs of oxygen of the sulfoxide function and the hydrogen of methyl bound to the tertiary amine of the dye molecule. [ABSTRACT FROM AUTHOR]

As a common agriculture waste as well as available biomass resource from ginkgo tree, ginkgo leaves were used as adsorbent to remove two models of cationic dyes methyl violet (MV) and malachite green (MG) after adequate modification. As the result, hydroxylated magnetic ginkgo leaf powder and carboxylated magnetic ginkgo leaf powder were obtained and characterized, respectively, which had the potential to be an environmentally friendly and economically effective biosorbents for the adsorption of dyes. These new biosorbents exhibited high adsorption capacity for dyes, with the maximum adsorption capacity of 450 mg g-1 for MV and 231 mg g-1 for MG. Further investigation confirmed that these adsorption processes were fitted with pseudo- second-order and Langmuir isothermal model. Moreover, these adsorbents with remarkable magnetism could be easily and rapidly recovered by external magnet after their use. The study demonstrated that the promising and reliable modified biosorbents were very suitable for removal of cationic dyes with high concentration at lower cost. [ABSTRACT FROM AUTHOR]

Iron-benzene dicarboxylic acid (BDC) metal-organic framework (MOF) has been synthesized by solvothermal method at room temperature and tested for the adsorptive removal of the organic dye crystal violet from aqueous solution. Dye removal efficiency and adsorption characteristics were determined to investigate factors such as the effect of dye concentration, contact time, temperature, dose, and pH. Maximum dye removal efficiency was recorded to be 100% with an initial dye concentration of 5 mg/L. Langmuir, Freundlich, and Temkin adsorption isotherm models were used to investigate the adsorption process. The adsorption isotherm of crystal violet onto Fe-BDC-MOF can be described by Freundlich isotherm model and Langmuir isotherm model. Pseudo-second-order kinetic model with rate constant 1.22 × 10-2 g/mg.min is found to be the best fit for the adsorption. Thermodynamic parameters viz. free energy; enthalpy, and entropy have been calculated with the help of adsorption isotherm data. The values of enthalpy and entropy have been obtained as 0.0947 kJ/mol and 0.325 kJ/mol/K, respectively, indicating an endothermic process with an increase in randomness at the solid-solution interface during adsorption. Negative value of ?G illustrates the process to be spontaneous. Column adsorption capacity of Fe-BDC-MOF has been recorded 26.65 mg/g. [ABSTRACT FROM AUTHOR]

This work was aimed at evaluating cationic dyes adsorption properties of 3A-molecular sieve adsorbents. Two cationic dyes, namely malachite green and methyl violet were used to probe the adsorbent performance. The adsorbents were characterized for surface functional groups, thermal stability, and specific surface area. The unmodified 3A-molecular sieve showed a surface area of 0.195 m2/g, whereas the value decreased upon sodium hydroxide treatment. The kinetics data fitted well into the pseudo-first-order model, suggesting a physical adsorption process via diffusion-limited transport mechanism, whereby cation-exchange and electrostatic attraction are the possible removal mechanisms. The modified adsorbent revealed better removal capacities for both dyes at 136 and 186 mg/g for methyl violet and malachite green, respectively. The Langmuir model adequately described the equilibrium data, indicating a homogenous nature of monolayer adsorption. The 3A-molecular sieve adsorbents could be effectively used as adsorbent for cationic dyes removal. [ABSTRACT FROM AUTHOR]

Dye-based industries, particularly small and medium scale industries, release their effluents into waterways without treatment due to cost considerations. Murraya koenigii stem is an agricultural waste that is present in various vegetable markets. To produce a value-added product from this agricultural waste, it is proposed to convert this waste into activated carbon for the removal of crystal violet dye from the aqueous medium. Therefore, the biochar was prepared from the curry tree bark. Batch adsorption experiments were conducted as a function of variables such as adsorbent dosage, time, temperature and dye concentration and subsequently, the optimum conditions were determined. The optimum operational parameters such as adsorbent dosage were found to be 100 mg L-1, time (60 min), temperature (35°C) and dye concentration (50 mg L-1). The equilibrium adsorption of dye on the adsorbent (qe) was found to be 50 mg g-1 and the removal efficiency was about 70%. The structure and morphology of curry tree carbon (CTC) before and after adsorption were characterized by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy. FTIR analysis indicated a change in peak. The results were analyzed using Langmuir and Freundlich isotherm model and it best fitted with the Langmuir model. Kinetic studies were assessed and were found to follow the pseudo-second-order model. We investigated the use of biochar produced from agricultural waste and our results provide novel perception into the potential of biochar to remove crystal violet from textile effluents. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO), graphene oxide/chitosan (GOCS), and graphene oxide/poly(n-butyl methacrylate- co-methacrylic acid) (GOpBCM) composites were prepared as adsorbents for removal of carcinogenic dye Congo red (CR) from aqueous solutions. They were characterized by various techniques, including Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and X-ray diffraction spectroscopy. Adsorption equilibrium isotherms, adsorption kinetics and thermodynamic studies of the batch adsorption process were done to evaluate the fundamental adsorption properties of the dye CR. The results indicate that the adsorption of CR on the adsorbents was high pH and temperature-dependent. The maximum adsorption of 1,666 mg/g occurred at pH 3.0 for an initial dye concentration of 500.0 mg/L by GOCS, whereas, the maximum adsorption obtained from an initial dye concentration 300.0 mg/L was 1,000 mg/g for GO and GOpBCM at pH 3.0 and 7.0 respectively. The experimental equilibrium adsorption data were explored by three different two-parameter models Langmuir, Freundlich and Temkin isotherms. The Langmuir model was well agreed with experimental data for all adsorbents. The kinetic models, namely pseudo-first-order, pseudo-second-order, and intraparticle-diffusion are employed to understand the mechanism of the adsorption process, and it fitted very well the pseudo-second-order kinetic model for all adsorbents. The calculated thermodynamic parameters revealed that the adsorption is a spontaneous and endothermic process. [ABSTRACT FROM AUTHOR]

Activated carbons prepared from the pericarp of rubber fruit (PrAC) or from bagasse (BAC) were compared with a commercial activated carbon (CAC) in an adsorption and desorption study of crystal violet in aqueous solution. The adsorbents were characterized by scanning electron microscopy, as well as for specific surface and pore size distribution from Brunauer-Emmett-Teller, Fourier-transform infrared spectroscopy, and the point of zero charge (pHpzc). The effects of adsorbent dosage, contact time, initial concentration of crystal violet, pH, and temperature were studied. The Langmuir adsorption isotherm fit well, and the calculated maximum adsorption capacities (qm) were 896.7, 432.66, and 351.12 mg g-1 at 60°C and pH 5.0 for CAC, PrAC, and BAC, respectively. The desorption study confirmed that PrAC, BAC, and CAC can be regenerated. The adsorption of crystal violet by PrAC, BAC, or CAC was endothermic and spontaneous. The heats of adsorption (ΔH°/kJ mol-1 = 18.43 for PrAC, 16.49 for BAC, and 30.82 for CAC) confirmed physisorption as adsorption mechanism. The maximum desorption percentages of crystal violet solution were 67.08, 46.32, and 40.64 for CAC, PrAC, and BAC at pH 2.03, indicating that PrAC and BAC can be reused in an economic treatment process. [ABSTRACT FROM AUTHOR]

In this research, brilliant green dye (BG) has been removed from synthetic wastewater using activated carbon derived from guava seeds (AGSC) which was collected as a waste product from factories producing juice concentrates. A single-stage batch adsorber was designed for adsorption of BG by AGSC based on some experimental parameters such as contact time (5-40 min), adsorbent mass (0.01-0.08 g), temperature (25°C-95°C), pH (3-10), and initial dye concentration (10-100 ppm). The maximum adsorption capacity of AGSC was found to be 80.5 mg/g using the Langmuir isotherm model which is the best-fitted model for the process. The experimental data were fitted well with the pseudo-second-order kinetic model. The changes in functional groups, surface morphology, and chemical composition of AGSC before and after adsorption were identified by Fourier transform infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, respectively. The specific surface area of AGSC was measured to be 605.1 m²/g using Brunauer- Emmett-Teller analysis. Pore volume and pore diameter were found to be 0.57 cm³/g and 3.78 nm, respectively. The thermodynamic study proved that adsorption of BG on AGSC was physiosorptive (ΔG = -7.7 kJ/mol) and spontaneous at high temperature (ΔH = 13.4 kJ/mol, ΔS = 0.07 kJ/mol K). [ABSTRACT FROM AUTHOR]