Metanil Yellow (MY), a highly toxic azo dye used in food products, was removed from aqueous solution using a metal- and halide-free ordered mesoporous carbon (OMC) adsorbent. MY exhibited a strong affinity towards OMC in batch as well as column operations, and OMC performed much better than previously reported adsorbents. The pH, dye concentration, adsorbent dosage, and contact time were optimised, and detailed adsorption experiments were performed under these conditions. Several isotherm models were fitted to the adsorption data, showing that the Langmuir and the Freundlich adsorption models were followed. Adsorption was spontaneous and endothermic at all measurement temperatures. On the basis of pH studies, enthalpy data, and adsorption isotherm analysis, adsorption was determined to be by physisorption. In kinetics studies, the adsorption process was found to be pseudo-second order with interparticle diffusion as the rate-limiting step. Column experiments using a fixed bed of OMC resulted in almost 100% column efficiency and a fractional column capacity of 0.999. During adsorption/desorption cycles of the exhausted column, 99.71% of the dye was recovered after the first cycle and 97.66% after the eleventh. These findings indicate that OMC is a promising and efficient material for the adsorptive removal of toxic MY dye.

A hazardous triphenylmethane dye, Crystal Violet, was effectively removed from its aqueous solution using a waste material-Hen Feather-as biosorbent. The Crystal Violet-Hen Feather adsorption system gives promising results and has not been studied previously. By removing a highly toxic dye, using a ubiquitous biowaste material this research provides dual advantages. The influence of contact time, adsorbent dosage, dye concentration, and solution pH on the uptake of Crystal Violet by Hen Feathers was systematically investigated. Six adsorption isotherm models, namely the Freundlich, Langmuir, Temkin, Dubinin-Radushkevich, Halsey, and Jovanovic models, were studied for the adsorption of Crystal Violet over Hen Feather and various physicochemical parameters were derived. Langmuir isotherm data were exploited to obtain thermodynamic variables. Negative values for ΔH° were recorded as -15.15 to -17.01 kJ·mol-1, and negative ΔG° values of -23.34 to 25.94 kJ·mol-1 confirmed the adsorption process was exothermic and spontaneous. It was determined that a pseudo-second-order kinetic model is applicable to the present adsorption system at all three tested temperatures. It was established that Hen Feather possesses a very strong affinity for Crystal Violet and works as an excellent scavenger through physisorption.

This study explores the detailed characterization of a biosorbent (Hen Feather) and its efficient use in eradicating the azo dye Metanil Yellow (MY) from its aqueous solutions. Effects of a range of experimental parameters, including pH, initial dye concentration, biosorbent dosage and contact time on the adsorption, were studied. A detailed physical and chemical characterization of the biosorbent was made using SEM, XRD, XPS and FTIR. During the optimization of adsorption parameters, the highest dye uptake of almost 99% was recorded at pH 2, dye concentration 2 × 10−5 M, 0.05 g of biosorbent and a contact period of 75 min. Various adsorption isotherm models were studied to gather different adsorption and thermodynamic parameters. The linearity of the Langmuir, Freundlich and D-R adsorption isotherms indicate homogeneous, multilayer chemisorption with high adsorption affinity between the dye and biosorbent. Values of the changes in the Gibbs free energy (ΔG°) and the enthalpy (ΔH°) of the adsorption process have been calculated, these values indicate that it is a spontaneous and endothermic process. Kinetics of the adsorption were also measured, and it was established that the adsorption of MY over Hen Feather follows a pseudo-second-order kinetic model at temperatures 30, 40 and 50 °C. The findings of this investigation clearly indicate that the studied biosorbent exhibits a high affinity towards the dye (MY), and it can be effectively, economically and efficiently used to sequestrate and eradicate MY from its aqueous solutions.

In this research we have successfully removed a highly toxic dye, "Aniline Blue", from its aqueous solution employing an adsorbent, Hen Feathers. The dye adsorption over Hen Feather was comprehensively studied over ranges of contact time, pH, concentration, and adsorbent dosage, and the optimum values were evaluated. In order to understand the behaviour of the adsorption system, various isotherm models were evaluated at temperatures of 30, 40 and 50 degrees C. The data obtained from contact time studies were used to test pseudo-first and pseudo-second order kinetic models and it was found that the adsorption follows pseudo-second-order kinetics. Using the Langmuir constant, b, thermodynamic parameters including Delta G degrees, Delta H degrees and Delta S degrees were calculated and it was ascertained that the process is endothermic (positive Delta H degrees), involves an increase in disorder (positive Delta S degrees) and is spontaneous (negative Delta G degrees). The values of the separation factor (r) also confirmed a favourable adsorption process at all three temperatures studied. Overall, it is affirmed that the adsorbent, Hen Feather, acts as highly potent scavenger to remove the dye Aniline Blue from its aqueous solutions.

A nanostructured material, ordered mesoporous carbon (OMC), was synthesised in metal- and halide-free form and its use for the sequestration of crystal violet, a hazardous triphenylmethane dye, is reported for the first time. The OMC material is characterised using scanning transmission electron microscopy with energy-dispersive spectroscopy for chemical analysis, by Fourier-transform infrared spectroscopy, and by nitrogen gas physisorption. The ideal conditions for the uptake of crystal violet dye were determined in batch experiments covering the standard parameters: pH, concentration, contact time, and adsorbent dosage. Experimental data are validated by applying Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherms. The thermodynamic parameters, ΔH°, ΔG°, and ΔS°, are calculated and it has been found that the adsorption process is spontaneous and endothermic with increasing disorder. An in-depth analysis of the kinetics of the adsorption process, order of the reaction and corresponding values of the rate constants was performed. The adsorption of crystal violet over OMC has been found to follow pseudo-second-order kinetics through a film diffusion process at all temperatures studied. Continuous flow column operations were performed using fixed bed adsorption. Parameters including percentage saturation of the OMC bed are evaluated. The exhausted column was regenerated through a desorption process and column efficiency was determined.

In today's era, "green" synthesis is an emerging research trend. It has gained widespread attention owing to its dynamic behavior, reliability, simplicity, sustainability, and environment friendly approach for fabricating various nanomaterials. Green fabrication of metal/metal oxides nanomaterials, hybrid materials, and other metal-based nanocomposite can be utilized to remove toxic colored aqueous pollutants. Nanomaterials synthesized by using green approach is considered to be the significant tool to minimize unwanted or harmful by-products otherwise released from traditional synthesis methods. Various kinds of biosynthesized nanomaterials, such as animal waste and plant-based, have been successfully applied and well documented in the literature. However, their application part, especially for the cure of colored organic polluted water, has not been reported as a single review article. Therefore, the current work aims to assemble reports on using novel biosynthesized green metal-based nanomaterials to exclude harmful dyes from polluted water.

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.

A hydrothermal methodology followed by calcinations employed for the formation of CeO2 -MnO2 /CNF composite to meet the requirement of superior electrochemical energy storage and sensing performance. The growth of agglomerated tiny CeO2 clusters grown with needle shaped MnO2 decorated over CNF surface gives rise to efficient hybrid sensing and electrode material. The surface structure and chemical features of as prepared nanocomposite was characterized by SEM (scanning electron microscopy), TEM (transmission electron microscopy), FTIR spectroscopy and UV-Visible spectroscopy. The crystalline phase of CeO2-MnO2 decorated over CNF substrate was analyzed by XRD (X-ray diffraction spectroscopy). The electrochemical studies of synthesized sample of CeO2-MnO2/CNF composite exhibited specific capacitance as 1453 Fg-1 at 10 mVs-1 scan rate in 1 M Na2SO4 electrolyte and provided appreciable 74% of capacitive retention after 2500 cycles. The electrode material exhibits superior energy density (ED) of 57 WhKg-1 and power density (PD) 1.8 KWKg-1. The fabricated composite CeO2- MnO2 /CNF also tested as sensing material for H2O2 and offered good sensitivity of 612 mu Acm-2mM-1 with correlation coefficient (R) 0.996 up to very low detection limit of 0.1 mu M.(c) 2022 Published by Elsevier B.V.

Incessant advancement of industry and agriculture has amplified organic pollutants contents in recent years causing grave threat to environmental well-being. With time, adsorption has established as an effective and financially advantageous process for the elimination of organic contaminants, like dyes, phenolics, pesticides, polynuclear aromatics and antibiotics. Biochar (BC), a carbon-rich material (70% approximate), prepared predominately by pyrolysis of waste materials such as biomass of agriculture and timber origin, is assumed by far the cleanest form of the charcoal. BC can have important physicochemical features like high carbon content as well as elevated surface chemistry heterogeneity, elevated textural features (specific surface area and pores volume), stable structure, cation exchange capacity, and recyclability. These features in combination with BCs low cost since they can be obtained from abundantly naturally available raw material, establish them as prosperous candidates for applications such as energy source (biofuel), as additives for soil amendment, to sequester carbon, pollution remediation and waste management by recycling agricultural by-products. Principal parameters on which BCs’ properties depend are the temperature and atmosphere of pyrolysis, heat transfer rate, feedstock, type and residence time. This article examines in detail the sources, production, characteristics and modification of BC, along with special emphasis on research published in recent 5 years particularly regarding the removal of a benchmark cationic organic dye, Methylene Blue.

2,4-Dinitrophenol (2,4-DNP) is a toxic compound that is widely used in many industrial and agricultural processes. This compound has low biodegradability in the environment due to its aromatic structure, and it is unsuccessfully eliminated by other chemical methods. Therefore, in this study, an integrated oxidation and reduction method was used to remove 2,4-DNP from the aqueous medium, in order to simultaneously use the benefits of oxidizing and reducing radicals in 2,4-DNP degradation. 2,4-DNP degradation was modeled by response surface methodology (RSM) and central composite design (CCD). According to the results obtained from RSM, the optimal values for the studied parameters were obtained at pH = 8.9, time = 25 min, ZnO dose = 0.78 g/L, SO3 = 1.89 mmolL−1 and 2,4-DNP concentration = 5 mg/L. Also, the removal efficiency with the integrated process was 3 to 4 times higher than the advanced oxidation or advanced reduction processes alone. Analysis of the data showed that at the time of the study, 2,4-DNP had been converted to linear hydrocarbons, and increased periods of time were required for complete mineralization. A decrease in the first-order model rate constant (kobs) and an increase in 2,4-DNP degradation rate (robs) were observed at higher DNP concentrations.

Herein, an ordered mesoporous carbon (OMC) material was prepared using a metal and halogen free method, and its adsorptive potential for the cationic dye, ‘Methylene Blue’ (MB), was investigated. Batch studies were carried out to determine the influence of pH, dye concentration, adsorbent quantity, and contact time on adsorption behaviour. Adsorption models based on Langmuir, Freundlich, Temkin and Dubinin-Radunkevich isotherms were validated and the thermodynamic variables governing the nature and feasibility of reaction were evaluated. Values of the adsorption uptake at equilibrium (qe) decreased as the temperature was increased, suggesting thereby that the adsorption process involved was exothermic. Kinetic studies indicated that adsorption obeyed pseudo-second order behaviour and operated via a ‘film-diffusion’ mechanism. When attempts were made to carry out bulk removal of MB using a fixed bed adsorption column, 99.5% saturation could be achieved. Desorption of MB from the used column was performed and dye recovery was almost 100% in the first cycle and on 5th cycle 99% of dye was obtained. This pattern clearly indicates that for the cationic dye MB, OMC acts as a highly efficient and robust adsorbent.

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 × 10–4 g/mg min is best fit for the adsorption process. Adsorption was found to be endothermic and processed via chemisorption.

The present study aims to explore the adsorption behavior of novel Kahwa tea (Camellia sinensis) carbon (KTC) towards its potential application as an adsorbent for the sequestration of Titan yellow (TY) dye from an aqueous solution. The maximum adsorption of TY from aqueous solution was observed at pH 5, contact time 180 min, initial concentration of dye 100 mg L-1 and temperature 318 K. The adsorption process follows a pseudo-second-order rate kinetic model and is in good agreement with the kinetic data. The equilibrium adsorption data fitted well with the Langmuir isotherm model with a maximum monolayer adsorption capacity of 55.55 mg g(-1), at 318 K. The thermodynamic parameters confirm the endothermic and spontaneous nature of the adsorption process with increased randomness. The desorption study predicts the excellent regenerative power of KTC.

The present report is an outcome of investigations to assess the adsorptive potential of a synthesized metal- and halide-free variant of ordered mesoporous carbon (OMC) towards an anionic azo dye, Methyl Orange. The results of preliminary studies, carried out in batch mode, helped in setting up the process variables to achieve optimum adsorption conditions. The experimental data were then fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevitch isotherm models. The equilibrium data fitted well to the Langmuir model at 303 K and the monolayer adsorption capacity was 0.33 mmol g(-1). The adsorption kinetics were explored by fitting the data to pseudo-first-order and pseudo-second-order kinetic models. The latter described the kinetics well, as indicated by higher regression coefficients. To elucidate the mechanism of mass transfer, various well-known mathematical models were employed. The adsorption of the dye was found to involve particle diffusion. Thermodynamic studies revealed that the adsorptive uptake of Methyl Orange by the OMC was spontaneous (Delta G(0) = -23.71 kJ mol(-1)) and exergonic (Delta H-0 = -123.15 kJ mol(-1)). Finally, the bulk removal of the anionic dye was investigated through column operations followed by column regeneration (desorption) studies. Column saturation of up to 96.55% could be realized. Values for dye recovery reached up to 93.26%. The column efficiency was then evaluated by carrying out three consecutive adsorption/desorption cycles. The results obtained indicated that the adsorbent has a good ability to eliminate Methyl Orange from wastewater, both in batch and column operations.

Herein, we report the synthesis of a novel bio-nanocomposite (Alg-Cst/Kal) for the effective removal of the dye "Crystal Violet" from its aqueous solutions. In order to observe the surface morphology and functional groups, the bio-nanocomposite was characterized using various techniques such as SEM, EDX, TEM, FTIR, XRD, and TGA. The effect of parameters like contact time, pH, concentration and temperature on the adsorption of the dye over adsorbent has been studied in detail. The dye - adsorbent system has been tested over various isotherm models and found to follow the Freundlich adsorption isotherm model at 303 K. The developed bio-nanocomposite material exhibits an excellent adsorption toward Crystal Violet with a maximum adsorption capacity of 169.49 mg.g(-1). The experimental data has been further validated by applying various kinetic models and the pseudo-second order kinetic model was the best suited model. The calculated rate constant values ranged from 0.0046 to 0.0204 g.mg(-1).min(-1) for different dye concentrations. The positive values of change in enthalpy, Delta H degrees (9.765 kJ.mol(-1)) and change in entropy, Delta S degrees (0.0565 kJ.mol(-1).K-1) obtained through thermodynamic studies demonstrate the endothermic nature and spontaneity of the adsorption process, respectively. The adsorption capacity of the adsorbent for the removal of the Crystal Violet dye was also compared with other adsorbents and found maximum. Novelty statement A novel bio-nanocomposite is synthesized by modifying the biopolymer alginate, cysteine and mixing the clay, kaolinite (Kal). The adsorption abilities of the material was tested the on the cationic hazardous dye, Crystal Violet. The material is novel and no attempt has so far been made to examine its batch adsorption abilities to remove hazardous dyes from the wastewater. The results are highly encouraging as out of all the adsorbents tested so far highest adsorption of the dye is observed in the present studies.

•Chemical modification of Egg shells (ES) and Egg shells with membrane (ESM) by ionic liquids firstly reported.•Structural, spectroscopic and thermal properties of these ES and ESM by XRD, FTIR and TG/DTA.•The chemical modification by both ionic liquids and protein contents increased the thermal stability of ES and ESM.•Potential application of modified ES as eco-friendly candidate for adsorption process.

In this study, papaya peel carbon (PPC) has been explored as a potential adsorbent for the removal of Pb(II), Cu(II) and Ni(II) from their aqueous phases. Optimum adsorption conditions such as contact time, pH, initial metal ion concentrations, adsorbent dosage and temperature were determined. Optimum pH for the removal of Pb(II) and Ni(II) was found to be 6, while for Cu(II) it was 5. Maximum monolayer adsorption capacity (qm) was found to be 40.98, 38.02 and 32.25 mg g–1 for Pb(II), Cu(II) and Ni(II) ions, respectively. To study the kinetic parameters and mechanism of adsorption process, pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich kinetic models were elucidated. D-R adsorption isotherm model best described adsorption of Pb(II) and Ni(II) ions onto PPC, whereas Freundlich adsorption isotherm described adsorption of Cu(II). To further predict the nature of adsorption, thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated and positive values of ΔH° indicated endothermic nature of the process. Thus overall results confirmed that PPC can be effectively used as an alternative and low-cost adsorbent for the removal of heavy metal ions Pb(II), Cu(II) and Ni(II).

In this paper, Ag doped MnO2-CNT nanocomposite was fabricated by using simple co-precipitation route. The synthesized nanocomposite was employed as adsorbent for elimination of Acridine Orange dye. The structural analysis of as synthesized Ag doped MnO2-CNT nanocomposite confirms the presence of (111) plane of Ag, (104) of carbon and (110) plane of MnO2. Processing of operational variable parameters such as, pH, adsorbent dose, and initial dye concentration with respect to contact time on adsorption of Acridine Orange was optimized and evaluated using Response Surface Methodology. The fit of the predictive model for the removal of dye was in good agreement with the experimental value. Isotherm data was modelled by means of Langmuir, Freundlich, Temkin and Dubinin- Radushkevich isotherm. Langmuir isotherm offered the best fit to experimental data proposing homogeneous dispersion of adsorption sites. Furthermore, the suitability of the adsorbent was also investigated by fitting the adsorption data with pseudo-second-order kinetic model. The recuperation and reusability of the adsorbent and adsorbate has made this process inexpensive and appropriate for large scale applications.

The fast growth in the anthropogenic activities, that involve a wide use of pharmaceuticals, has led to the appearance of new toxic and hazardous chemical compounds, called “emerging pollutants”, which could cause unpredictable consequences to the ecosystems. The current review is focused on emerging pollutants occurring in food or air and include caffeine and nicotine, as well as on pharmaceuticals, in particular amoxicillin, and the concerns caused by its wide usage for medical purposes. This review, for the first time, analyzes and discusses the potential risks and implications of caffeine, nicotine and amoxicillin as emerging environmental pollutants, a field that remains underrepresented to date. Both caffeine and nicotine belong to life style compounds, while pharmaceutical amoxicillin is one of the very popular β-lactam antibiotics used to take care of human and animal infections. The review covers the toxic effect caused by caffeine, nicotine and amoxicillin on humans and animals and describes some of the main adsorbents utilized for their removal (e.g., grape stalk, tea waste, wheat grains, bentonite, activated carbon, acid and base modified grape slurry wastes, graphene oxides, modified graphene oxides, zeolites, etc.). The isotherm and kinetic models for the analysis of caffeine, nicotine and amoxicillin adsorption by different adsorbents are presented. The impact of pH, temperature, adsorbent dosage and thermodynamic studies were deeply analyzed. The review also discusses the mechanism of adsorption for the above-mentioned emerging pollutants, which includes π–π interaction, cation-π bonding, electron-donor and electron-acceptor forces, van der Waals forces, electrostatic interactions, etc. The present review has a potential value for chemists, ecologists, toxicologists, environmental engineers, and other professionals that are involved in environmental protection.

Ash of Curcuma caesia has been explored as potential adsorbent for removal of hazardous dye malachite green from aqueous solution. Surface morphology of ash was studied using scanning electron microscopy. The adsorption mechanism and kinetics of the process have been investigated. Adsorption process is pH-dependent and favored at basic pH. Dubinin-Radushkevich (D-R) adsorption model has been found to be most appropriate for the adsorption. Physic-sorption has been found to control the adsorption mechanism. Intraparticle diffusion is best followed. Batch and column adsorption studies of malachite green onto C. caesia ash were carried out. Adsorption capacity for the column process is found to be 38.16 mg/g which is less than that of the batch process. Value for change in Gibbs free energy is negative over the entire temperature range, indicating the process to be spontaneous. The adsorption process is endothermic.