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In this study, biochar derived from Jackfruit peel (JA) via the pyrolysis at 500 °C for 2 h was used as an adsorbent to remove Methylene Blue (MB) from aqueous solution. Effects of pH, contact time, and initial MB concentration were investigated. Isotherm models, such as Langmuir, Freundlich, Sips, and Dubinin-Radushkevich, were applied to estimate the adsorption in nature. The results indicated that the Sips and Freundlich models gave the best fit with experimental datas. The maximum adsorption capacity of MB calculated from Langmuir was 39.87 mg/g at 306K, pH = 11, and time = 60 min. The E value evaluated from Dubinin-Radushkevich smaller than 8 kJ/mol indicated that the MB adsorption of JA followed a physical process.

The uptake of Methyl Orange (MO) and Methylene Blue (MB) from aqueous solutions onto Pine leaves (Pinus kesiya) was investigated in this work. The pine leaves was dried, grinded and thermally treated at 300 o C. Factors including pH solution, contact time, initial dye concentration were discovered to be relevant in the removal of dyes. Among four isotherm models (Langmuir, Sips, Freundlich, and Temkin), the experimental data was fitted the Langmuir model better than others. For MO and MB, the maximum Langmuir adsorption capacities were 136.99 mg.g − 1 and 140.85 mg.g − 1 , respectively. The kinetic studies demonstrated that the biosorption of MO and MB onto pine leaves was compatible with Elovich, pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The thermodynamic studies showed that the uptake of the two dyes was regulated by physisorption, spontaneous, and endothermic in nature. Electrostatic interactions, as well as other non-covalent forces such as π–π interactions and hydrogen bonds, are mechanisms of dyes adsorption on heat treated pine leaves biomass. The current study found that pine leaves (Pinus kesiya) might be a potential biosorbent for the wastewater treatment due to their high availability and production, resulting in various environmental advantages.

The uptake of Methyl Orange (MO) and Methylene Blue (MB) from aqueous solutions onto Pine leaves (Pinus kesiya) was investigated in this work. Factors including pH solution, contact time, initial dye concentration were discovered to be relevant in the removal of dyes. Among four isotherm models (Langmuir, Sips, Freundlich, and Temkin), the experimental data was fitted the Langmuir model better than others. For MO and MB, the maximum Langmuir adsorption capacities were 136.99 mg.g − 1 and 140.85 mg.g − 1 , respectively. The kinetic studies demonstrated that the biosorption of MO and MB onto biomass of pine leaves was compatible with Elovich, pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The thermodynamic studies showed that the uptake of the two dyes was regulated by physisorption, spontaneous, and endothermic in nature. Electrostatic interactions, as well as other non-covalent forces such as π–π interactions and hydrogen bonds, are mechanisms of dyes adsorption on pine leaf biomass. The current study found that pine leaves (Pinus kesiya) might be a potential biosorbent for the wastewater treatment due to their high availability and production, resulting in various environmental advantages.

Pomelo fruit peel, an organic waste, was utilised as a biosorbent to remove Ni(II) from aqueous solutions. Some major factors influencing Ni(II) uptake such as pH, adsorption time, and initial Ni(II) concentration were examined. Several isotherm and kinetic models including the Langmuir, Freundlich, Sips, pseudo-first-order, pseudo-second-order, and intra-diffusion models were fit to the experimental data. Results showed that the Ni(II) uptake obtained an equilibrium at pH=6 after 80 min at 303 K. The Sips isotherm model described the Ni(II) adsorption better than other models and the monoadsorption capacity calculated from the Langmuir model was 9.67 mg/g. The adsorption of Ni(II) followed pseudo-second-order kinetic models with three stages.

Nanomaterials, especially metal oxide nanomaterials with unique properties, with large specific surface area, affinity, capacity, and selectivity for heavy metals and other contaminants, have attracted scientists in the treatment of wastewater. The use of some nanomaterials as adsorbents for imbibing heavy metals and toxic organic compounds is discussed. Furthermore, the investigation of adsorptive mechanisms based on the combination of isotherm models (Langmuir, Freundlich, and Sips), kinetic models (pseudo-first-order, pseudo-second-order, and intra-diffusion models), and spectroscopies (Fourier transform infrared [FT-IR] and thermogravimetry and differential scanning calorimetry [TG-DSC]) will be encompassed in this chapter.

A facile and simple chemical precipitation method was utilized to synthesize FeFe2O4 magnetic nanomaterial for removing methylene blue (MB) from aqueous solution. Characterizations of this material were examined by using XRD, SEM, FT-IR, TGA-DTG and BET methods. Factors affecting the uptake of methylene blue, including pH, adsorption time, and MB initial concentration were also studied. The measured data were fitted by using four isotherm models including Langmuir, Freundlich, Sips and Temkin. Results showed that the Sips model offers the best fit to the data. In addition, the monolayer MB adsorption capacity obtained from the Langmuir model was 42.35 mg g−1 under the optimal conditions of pH = 10 and adsorption time = 80 min. In particular, the uptake of MB onto FeFe2O4 magnetic nanomaterial obtained from the kinetic and mechanism studies of the adsorption was in good agreement with prediction of the pseudo-first-order model, whereas the electrostatic interaction was found to play a primary mechanism. Keywords: FeFe2O4 magnetic nanomaterial, Adsorption, Methylene blue, Adsorption mechanism

To remove Ni(II) ions from an aqueous solution, researchers used red mud modified by chitosan (RM/CS) material as a new adsorbent. According to the findings, the surface area of red mud is nearly doubled after being treated with chitosan, from 68.6 m2/g to 105.7 m2/g. The effects of pH solution, contact time, and material dosage on the Ni(II) uptake were examined. In comparison with the pseudo-first-order and pseudo-second-order models, the intra-diffusion model was the most suitable kinetic model for the Ni(II) removal. Besides, the three-parameter Sips model was used to predict the Ni(II) adsorption of RM/CS from aqueous solution. Furthermore, the Langmuir maximum Ni(II) uptake capacity of this material was 31.66 mg/g at 323K, which was higher than red mud and several other natural materials. Notably, thermodynamic investigations demonstrated that Ni(II) adsorption on RM/CS is both exothermic and physic.

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Red mud modified by chitosan (RM/CS) was utilized as an adsorbent to effectively remove Pb(II) from aqueous solution. The surface area of RM/CS was found to significantly increase by more than 50% compared to that of original red mud. Different factors that affected the Pb(II) removal on this material, such as initial Pb(II) concentration, pH, and contact time, were investigated. The pseudo-first-order, pseudo-second-order, and intra-diffusion models were used to fit the experimental data to investigate the Pb(II)'s removal kinetics. The Pb(II) removal followed the intra-diffusion model. Additionally, the non-zero C value obtained from this model indicates that the removal was controlled by many different mechanisms. We also found that the interaction of Pb(II) and carbonate group on the material's surface played a primary role once the adsorption equilibrium was reached. Finally, the maximum adsorptive capacity was found to be about 209 mg/g. This obtained value is higher than those obtained for some other materials. Therefore, the present RM/CS should be a potential material for removing Pb(II) from aqueous solution.

In this study, the biosorption mechanisms of methylene blue (MB) and Cr(III) onto pomelo peel collected from our local fruits are investigated by combining experimental analysis with ab initio simulations. Factors that affect the adsorption such as pH, adsorption time, adsorbent dosage and initial adsorbate concentration, are fully considered. Five isotherm models—Langmuir, Freundlich, Sips, Temkin, and Dubinin–Radushkevich—are employed to estimate the capacity of pomelo peel adsorption, whereas four kinetic models—pseudo-first-order, pseudo-second-order, Elovich and intra-diffusion models—are also used to investigate the mechanisms of the uptake of MB and Cr(III) onto the pomelo fruit peel. The maximum biosorption capacities calculated from the Langmuir models for MB and Cr(III) at 303 K are, 218.5 mg g−1 and 11.3 mg g−1, respectively. In particular, by combining, for the first time, the experimental FT-IR spectra with those obtained from ab initio calculations, we are able to demonstrate that the primary adsorption mechanisms of the uptake of MB onto pomelo fruit peel are electrostatic attraction and hydrogen-bond formations, whereas the adsorption mechanisms for Cr(III) are electrostatic attraction and n–d interactions.

The present paper reports the fabrication of inverse opal photonic crystals (IOPCs) by using SiO2 spherical particles with a diameter of 300 nm as an opal photonic crystal template and poly(ethylene glycol) diacrylate (PEGDA) as an inverse opal material. Characteristics and fluorescence properties of the fabricated IOPCs were investigated by using the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), reflection spectroscopy, and fluorescence microscopy. The results clearly showed that the IOPCs were formed comprising of air spheres with a diameter of ∼270 nm. The decrease in size led to a decrease in the average refractive indexes from 1.40 to 1.12, and a remarkable stopband blue shift for the IOPCs was thus achieved. In addition, the obtained results also showed a fluorescence enhancement over 7.7-fold for the Fluor® 488 dye infiltrated onto the IOPCs sample in comparison with onto the control sample.

Manganese dioxide, in particular α-MnO2, is one of the advanced inorganic nanomaterials having wide applications in many areas. Hence, understanding the crystallization pathways, morphologies, and formation mechanism of defects in its structure is of particular importance, not only for fundamental science but also for practical applications. Herein, different physically and chemically based methods, such as Neutron Diffraction (ND), XRD, SEM, TPR- H2, TGA-DSC, FT-IR, Positron Annihilation Lifetime (PAL), Doppler Broadening (DB) of positron annihilation radiation, and Electron-Momentum Distribution (EMD) measurements combined with theoretical calculations, were utilized to systematically investigate the composition, structure, and morphology of α-MnO2 nanomaterial under different annealed temperatures. The investigated material was synthesized at room temperature using a facile chemical method with potassium permanganate (KMnO4) and ethanol (C2H5OH), prior to being treated by temperatures of 100 oC – 800 oC. Results demonstrated, for the first time, that the α-MnO2 nucleation can be formed even at room temperature and gradually developed to α-MnO2 nanorods at 600 oC. This novel finding, which cannot be explored by conventional XRD, was confirmed by ND analysis. In addition, PAL analysis combined with theoretical ab initio calculations indicated the existence of H+ ions in the tunnel [1x1] of α-MnO2. At the same time, DB and EMD measurements explored the presence of Mn and O vacancies in α-MnO2 crystals at low temperatures. Finally, the present study reported a remarkable finding that organic molecules may act as reactants as well as templates, which are entirely decomposed and disappeared at highly annealed temperatures.

The present work investigates the primary adsorption mechanisms of lead (II) and cadmium (II) cations onto pomelo fruit peel (PFP) from aqueous solution. pH, adsorption time, ion strength, and initial metal cation concentrations, which are factors affecting the uptake of these cations, are investigated. Results show that pH and ion strengths strongly affect the removal of these cations from aqueous solution. Different isotherm adsorption models, such as Langmuir, Freundlich, and Sips, are utilized to fit the experimental data in order to determine the adsorption in nature. The Langmuir monolayer adsorption capacities are found to be 47.18 mg/g for lead (II) and 13.35 mg/g for cadmium (II). Kinetic and thermodynamic studies based on a combination of FT-IR and TG-DSC spectroscopies demonstrate that electrostatic attraction plays a primary adsorption mechanism of lead (II) and cadmium (II) cations onto pomelo fruit peel.

In this report, the adsorption of Cr(VI) onto MnO

This work studies the Pb(II) removal onto bentonite clay modified by hexadecyl trimethyl ammonium bromide (HDTMA). Characterizations of the unmodified and modified materials were performed by using XRD, SEM, TG-DSC, FT-IR, and BET surface area analyses. Factors influencing the uptake of Pb(II) from aqueous solution, such as pHsolution, ion strength, uptake time, adsorbent dosage, and initial Pb(II) concentration, were examined. The obtained results showed that bentonite clay was successfully modified by HDTMA, resulting in an increase in its surface area by about 70 %. The Pb(II) adsorption onto modified bentonite clay reached equilibrium at pH = 5.0 after 120 min. Studies within the isotherm and kinetic models demonstrated that the adsorption followed the Sips isotherm and pseudo-second-order kinetic models. The maximum monolayer adsorption capacity calculated from the Langmuir model at 30 °C was 25.8 mg/g, which is much higher than that obtained for the unmodified sample (18.9 mg/g). The FT-IR and TG-DSC analyses indicated that the formation of inner-sphere complexes plays a fundamental role in the mechanism of Pb(II) uptake onto HDTMA-bentonite clay. This mechanism of Pb(II) adsorption was further investigated, for the first time, by using the positron annihilation lifetime (PAL) and electron momentum (EMD) measurements. The PAL and EMD analyses indicated that the existence of Al and Si mono-vacancies in the HDTMA-bentonite should have essential contributions to the adsorption mechanism. In particular, we found a very interesting mechanism that the Pb(II) adsorption should occur inside the interlayer spaces of the HDTMA-bentonite.

Manganese dioxide nanoparticles are loaded onto the surface of chitosan (CS) in order to enhance their adsorption properties. Various theoretical models and spectroscopic analytical methods are used to investigate the equilibrium isotherm, kinetics, and mechanisms of the removal of lead(II) from the aqueous solution. The kinetic studies based on a pseudo-second-order model show that the uptake of lead(II) occurs via three stages depending on the reaction time. The experimental data are fitted using four nonlinear isotherm models, namely the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The results obtained within the Langmuir model gave the highest R2, the smallest root-mean-squared error (RMSE), and the best nonlinear chi-square test (χ2) values, indicating that this model is the most appropriate approach for describing the adsorption of lead(II) onto the MnO2/CS nanomaterials. It is also found that the maximum monolayer adsorption capacity is 126.1 mg/g, which is higher than most of the values obtained from other materials. In addition, the results of the heat of the sorption process and the mean free energy calculated from the Fourier transform infrared spectroscopy (FTIR) suggested that the adsorption indeed follows a physical process. By using the Positron Lifetime Spectroscopy, which is used for the first time to investigate the “ions-holes” mechanism of the removal of lead(II) by CS loaded MnO2 nanoparticles, we found that the “ions-holes” mechanism in fact occurs at the micropores of MnO2 crystals in the MnO2/CS nanomaterials. This result is significant as it will be a reference for the use of the spectroscopic analytical methods for investigating the adsorption mechanism.

Thermostable and highly water-soluble polymers are essential for polymer flooding—one of the most effective methods used in the enhanced oil recovery (EOR) in high-temperature (HT) offshore reservoirs. In this research, the copolymerization reaction of the acrylamide (AM) and N-vinylpyrrolidone (NVP) monomers was performed via a free-radical mechanism induced by gamma-rays (γ-rays) irradiation. The impact of input data (the ratio and the concentration of the monomer to the viscosity of resultant solution) was scanned in detail and used to optimize the copolymerization conditions. The optimal viscosity values of the polymer concentration were 0.5 wt%. The optimal conditions for copolymerization were obtained at 1.7 for the AM/NVP monomer ratio and 23.2 wt% for the monomer concentration. The copolymerization induced by γ-rays irradiation under the optimized conditions was then carried out, and the obtained viscosity of 0.5 wt% of produced copolymers' solutions was 5.02 cP. These results were in good agreement with the calculated values. The obtained copolymers were then covalently coupled with graphene oxide (GO) synthesized from natural graphite using the modified Hummer’s method. The product nanocomposites (GO–P(AM-NVP) were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and gel permeation chromatography. The thermal and chemical stabilities of the brine-dispersed P(AM-NVP) copolymers annealed at 123 °C (the WT Miocene reservoir temperature) and the GO–P(AM-NVP) nanocomposite dispersion annealed at 135 °C (the WT Oligocene reservoir temperature) for 31 days were observed through the visual inspection and viscosity testing. Results indicated that the dispersions of the P(AM-NVP) copolymers and P(AM-NVP) copolymers conjugated on the GO nanosheets exhibited excellent thermal and chemical stabilities; therefore, they can serve asa promising agent for EOR in HT offshore reservoirs.

In this report, the adsorption of Zn(II) ion on g- and a-MnO2 nanostructures was compared. The results showed that the maximum adsorption was obtained at pH = 4.0 for both materials and after 60 minutes for g-MnO2 and 80 minutes for a-MnO2. Adsorption isotherm models demonstrated that the Langmuir was the best model to describe the adsorption of Zinc(II) on g- and a-MnO2 because of the highest correlation coefficient (R2), the smallest root mean square error (RMSE), and the nonlinear chi-squared test (c2) values. The maximum adsorption capacity of g-MnO2 calculated from Langmuir model was 55.23 mg/g, which was roughly double a-MnO2. The lower 1/n value from Freundlich model for a-MnO2 revealed that it was not as favourable as g-MnO2. The heat of the adsorption as well as the mean free energy estimated from Temkin and Dubinin - Radushkevich models to be less than 8 kJ/mol indicated that the adsorption on both materials followed a physical process. Kinetic studies showed that pseudo-second-order model was accurate to describe both materials in three stages.

Aqueous industrial wastes from heavy industry factories contain a large amount of Fe ions, which constitute a hazard for human life even at trace concentrations. Adsorption technology is a promising method for removing Fe(III) from aqueous solutions. In this report, the adsorption of the Fe(III) ion on γ- and α-MnO2 nanostructures was compared. The results showed that the maximum adsorption was obtained at pH = 3.5 for both materials after 120 min for γ-MnO2 and 80 min for α-MnO2. Adsorption isotherm models, such as Langmuir, Freundlich, Sips, Tempkin, and Dubinin–Radushkevich were applied to determine adsorption capacity as well as the nature of the uptake. The highest R2, the smallest of root mean squared error (RMSE), and the nonlinear Chi-square test (χ2) values determined that the Sips model was the most appropriate equation to describe the adsorption of Fe(III) on γ- and α-MnO2. The maximum monolayer adsorption capacity calculated from the Langmuir model and the maximum adsorption capacity calculated from the Sips model of γ-MnO2 was more than four times that of α-MnO2. The heat of the adsorption as well as the mean free energy estimated from Tempkin and Dubinin–Radushkevich was determined to be less than 8 kJ/mol, which showed that the adsorption on both materials followed a physical process. Kinetic studies showed that a pseudo-second-order model was accurately described on both samples with three stages.

In this work, gamma–MnO2 nanostructure was used as a sorbent to remove Zn (II) ion from aqueous solution. The influence of pH, sorption time and Zn (II) ion initial concentration were examined. The results showed that equilibrium adsorption was obtained after 60 minutes with 240 rpm of shaking speed at pH = 4.0. The experimental data were analyzed using five non-linear isotherm models: Langmuir, Freundlich, Sips, Tempkin and Dubinin – Radushkevich. The adsorption capacity (qm) from the Langmuir isotherm model for Zn (II) is founded as 55.23 mg/g. The heat of sorption process and the mean free energy were estimated from Temkin and Dubinin – Redushkevich isotherm models to be less than 8 kj/mol which vividly proved that the adsorption experiment followed a physical process. Kinetic studies have shown that although the adsorption data partially followed pseudo-first-order and pseudo-second-order equation for different time, it was well expressed by pseudo-second-order model.

MIL–88B(Fe) (MIL: Materials Institute Lavoisier) and bimetallic Al/Fe Metal-Organic Framework (Al/Fe-MOF) were synthesized by the microwave-assistant method. The as-synthesized samples were used as an effective catalyst for photo-Fenton degradation of rhodamine B (RhB) under visible light irradiation. The Al/Fe-MOF catalyst caused to degrade more than 96% of RhB in up to 120 min with the rate of reaction reached 2.8 × 10−2 min−1, while the rate achieved using MIL–88B(Fe) reached 1.2 × 10−2 min−1. Besides, the reaction mechanism of RhB photo-Fenton degradation process over Al/Fe-MOF also investigated. These results indicate that Al/Fe-MOF has been considered as a potential catalyst for wastewater treatment.

In this report, the adsorption of Cr(VI) onto MnO2/CS nanocomposite material from aqueous solution is investigated. All the factors, which affect the adsorption, such as pH, adsorption time, Cr(VI) initial concentration and adsorbent dosage, are also examined. The results obtained show that the Cr(VI) uptake is strongly affected by pH and ion strength. Analysis within the nonlinear isotherm models indicates that the Sips isotherm combining with the Langmuir and Freundlich models offer the best fit to the experimental data due to the obtained highest R2 and smallest RMSE and χ2 values. The calculated Langmuir monolayer adsorption capacity is 61.56 mg g−1 at pH of 2.0 and adsorption time of 120 min. Moreover, the mechanism studies by combining theoretical models with analytical spectroscopies reveal that the electrostatic attraction plays the important role to the uptake of Cr(VI) onto MnO2/CS nanocomposite. Therefore, the present nanocomposite material can be applied to remove total Cr from wastewater produced by the galvanized manufacturing factory with a relatively high efficiency.