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In this study, a systematic analysis was conducted to investigate the efficiency and mechanism of methylene blue (MB) removal from water using blue coke-based activated carbon (AC) as an adsorbent. The investigation encompassed several critical parameters, including adsorbent dosage, contact time, pH, temperature, initial MB concentration, and the regeneration capacity of the adsorbent. The adsorption mechanism of MB by AC was elucidated through instrumental analysis and theoretical models such as adsorption kinetics, isotherm models, and thermodynamic analysis. The experimental results demonstrated several key findings: the removal efficiency of MB increased with the adsorbent dosage, although the unit adsorption capacity decreased; the removal rate of MB rose rapidly with increasing contact time and reached equilibrium after 90 min; the highest removal efficiency was achieved at pH 6; the adsorption capacity increased with higher initial MB concentrations. The adsorption kinetics conformed to the pseudo-second-order model, indicating that chemical adsorption was the predominant control step. The adsorption process was identified as a spontaneous reaction, with the Langmuir model suggesting a maximum adsorption capacity of 2040.696 mg/g at 318 K. Furthermore, AC exhibited an abundant mesoporous structure and surface functional groups, contributing to the efficient removal of MB. The adsorption mechanism involved pore-filling, hydrogen bonding, π-π interactions, and electrostatic attraction. Additionally, AC demonstrated excellent regeneration performance. These findings suggest that AC prepared from blue coke holds significant potential for industrial applications in MB removal, owing to its high removal efficiency, low cost, and good regenerative properties, making it highly valuable for practical use.

The removal of ammonium from wastewater is a crucial process to mitigate the potential environmental issues associated with high nitrogen content in the water bodies. Natural zeolite, particularly clinoptilolite, has shown promise as an adsorbent for this purpose due to its unique surface properties. While zeolite has been studied extensively in this context, the current work represents an exploration of natural zeolite from The Tanggamus District, Indonesia. The study evaluated the impact of the desilication process on the ammonium adsorption capacity of this natural zeolite. The zeolites were characterized using XRD, XRF, and SEM. Batch adsorption studies revealed that the modified zeolite showed promising ammonium adsorption performance up to 35.4 mg/g. The adsorption data fit well with the pseudo-second-order kinetics and Freundlich isotherm model, suggesting chemisorption as the predominant mechanism. The effect of temperature and thermodynamic parameters highlighted the exothermic nature of the adsorption process. [ABSTRACT FROM AUTHOR]

The flow of graphene oxide (GO) into natural water systems can adversely affect water environments and ecosystems. In this study, the adsorption effect of calcite on GO under different conditions was studied using calcite as adsorbent. Meanwhile, characterized by a combination of microscopic experiments, including SEM, TEM, XRD, FTIR, Raman, XPS, and AFM, additional research on the performance and the mechanism of GO sorption by calcite was conducted. The findings indicated that the highest adsorption efficiency was observed at a temperature of 303 K, pH 3, a mass of 90 mg of calcite, with an initial concentration of 60 mg L−1 GO, resulting in a 95% adsorption rate. The adsorption isotherm conformed to the model of Langmuir and Temkin, and it is a heat absorption process dominated by monolayer adsorption. The thermodynamic analysis showed that the adsorption was spontaneous and heat-absorbing. The adsorption kinetics conformed to the pseudo-second-order kinetic model, and the sorption procedure is chemisorption. In conclusion, calcite has a good sorption capacity for GO, which can provide a reference for the removal of GO in the aqueous environment. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to remove Cu (II) ions from the aqueous solution by Natural Mixed Type Siirt Clay (NMTSC-2) from the aqueous solution. NMTSC-2 (clay containing chlorite, montmorillonite, vermiculite, muscovite, kaolinite and illite) was characterized by analysis methods of X-ray fluorescence spectroscopy (XRF), Fourier transform infrared, (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM-EDS), Brunauer–Emmett–Teller (BET) and thermogravimetric analysis (TGA). The data obtained as a result of the experimental studies were applied to the Freundlich, Langmuir, Temkin, Elovich and Dubinin–Radushkevich (D–R), Harkins–Jura adsorption isotherms. In the study, a new linear equation was derived from the Harkins–Jura model. The new form was applied to the NMTSC-2 adsorption experiment of Cu (II), the obtained constants and the plots were given in the study. In order to compare the models, the results were subjected to regression analysis. The new linear equation was found to be the most suitable model for the experimental data. The Langmuir model was the second most compatible with the experimental data. In adsorption experiments were performed at 298, 308 and 318 K temperatures, Cu (II) ion qm values were found as 21.146, 25.380 and 29.850 mg g−1, respectively. Thermodynamic data for 298,308 and 318 K temperatures were found as ΔG = − 24.394, − 33.724 and − 43.054 kJ mol−1 ΔH = 53.039 kJ mol−1, ΔS = 0.181 kJ mol−1 K−1. [ABSTRACT FROM AUTHOR]

The discharge of diethylenetriamine (DETA) into aqueous environment poses a threat to public health and environment. Therefore, it is imperative to take effective measures to remove DETA from water. The elimination of DETA from water may be realized via the way of adsorption with activated carbon. In this paper, the adsorption of DETA from water by activated carbon originated from coconut shell has been explored in batchwise operation. The effects of stirring speed, temperature, pH, DETA concentration, carbon dosage and particle size on DETA adsorption have been determined by experiment. The adsorption results exhibit that the DETA adsorption rate increases with its concentration in the aqueous solution and temperature. However, the amount of DETA adsorbed on the carbon at equilibrium decreases slightly with temperature. The DETA adsorbed increases with pH changing from 8 to 11 and remains constant if pH rising over 11. The kinetic study shows that DETA adsorption on the activated carbon is in good agreement with the pseudo-second-order kinetic model with a correlation coefficient of 0.999. The DETA removal from the solution increases with the carbon dosage. The Langmuir equilibrium isotherm model has been found to provide a better fitting of the adsorption data than the Freundlich equilibrium isotherm model with a maximum adsorption of 90.50 mg g−1. The thermodynamic parameters evaluated from the experiments are ΔS 14.49 J∙mol−1∙K−1, ΔH −11.32 kJ mol−1 and ΔG changing from −15.71 from −16.15 kJ mol−1with the temperature rising from 30°C to 60°C. The thermodynamic study suggests the exothermic and spontaneous natures of DETA sorption on activated carbon. [ABSTRACT FROM AUTHOR]

The objective of this study is to prepare magnetic composites as adsorbents for Cr(VI) from wastewater. The prepared composites are magnetic activated carbon (M-AC), magnetic ash (M-ASH), and magnetic sand (M-SAND). These composites were characterized using XRF, FTIR, XRD, and TGA, and then tested as adsorbents for toxic Cr(VI) ions from synthetic wastewater. The elemental analysis of the composites showed a crucial increment in the Fe content of about 6425%, 3600%, and 93% for M-SAND, M-AC, and M-Ash, respectively. Their FTIR spectrum showed the existence of the Fe–O bond vibration, indicating the presence of Fe3O4 particles as confirmed by the XRD pattern. The pseudo-second-order model best described the adsorption kinetic results and the Redlich-Peterson isotherm model accurately described the equilibrium data of ion adsorption by the three composites at 25 and 40 °C with relatively high values of R2. The composites showed their highest adsorption capacities for Cr(VI) ions at 40 °C with an average adsorption capacity of the composites was about 50 mg/g. These relatively high values demonstrate the adsorption ability of the magnetic composites and present a strategy to use the adsorption process for Cr(VI) ions by these composites as efficient adsorbents.

In this study, a systematic analysis was conducted to investigate the efficiency and mechanism of methylene blue (MB) removal from water using blue coke-based activated carbon (AC) as an adsorbent. The investigation encompassed several critical parameters, including adsorbent dosage, contact time, pH, temperature, initial MB concentration, and the regeneration capacity of the adsorbent. The adsorption mechanism of MB by AC was elucidated through instrumental analysis and theoretical models such as adsorption kinetics, isotherm models, and thermodynamic analysis. The experimental results demonstrated several key findings: the removal efficiency of MB increased with the adsorbent dosage, although the unit adsorption capacity decreased; the removal rate of MB rose rapidly with increasing contact time and reached equilibrium after 90 min; the highest removal efficiency was achieved at pH 6; the adsorption capacity increased with higher initial MB concentrations. The adsorption kinetics conformed to the pseudo-second-order model, indicating that chemical adsorption was the predominant control step. The adsorption process was identified as a spontaneous reaction, with the Langmuir model suggesting a maximum adsorption capacity of 2040.696 mg/g at 318 K. Furthermore, AC exhibited an abundant mesoporous structure and surface functional groups, contributing to the efficient removal of MB. The adsorption mechanism involved pore-filling, hydrogen bonding, π-π interactions, and electrostatic attraction. Additionally, AC demonstrated excellent regeneration performance. These findings suggest that AC prepared from blue coke holds significant potential for industrial applications in MB removal, owing to its high removal efficiency, low cost, and good regenerative properties, making it highly valuable for practical use. [ABSTRACT FROM AUTHOR]

Inverse gas chromatography (IGC), atomic absorption spectroscopy (AAS), and Fourier-transform infrared spectroscopy (FTIR) were employed to investigate the surface properties of torrefied cardboard samples and their hydrocarbon adsorption. Three torrefied cardboard samples, TC-200, TC-250, and TC-300, were prepared at 200, 250, and 300 °C, respectively. A series of n-alkanes, BTX (benzene, toluene, and p-xylene), and several polar probes (dichloromethane, acetone, ethyl acetate, and tetrahydrofuran) were selected as molecular probes to measure the molar adsorption enthalpies ( Δ H m ), dispersive surface energies, and acid–base properties of torrefied cardboard samples. The Δ H m values of hydrocarbons measured on TC-300 and TC-250 were more exothermic than those measured for TC-200 by about 19 and 13%, respectively. The Δ H m values of benzene, toluene, and p-xylene on three torrefied cardboard samples became more negative than those of n-hexane, n-heptane, and n-octane by approximately 17–20%. Surface free energy analysis using molecular probes found that TC-300 exhibited higher dispersive and specific surface energy than TC-250 and TC-200 did. From FTIR spectra and elemental analysis via AAS, C=C moieties in the carbonaceous substances and inorganic mineral compositions are responsible for enhanced dispersive and specific surface energy of TC-300. BTX adsorption isotherms on torrefied cardboard samples were well-fitted using the Freundlich model. Fitted parameters of adsorption isotherms also found that TC-300 had a larger adsorption capacity toward BTX than TC-250, TC-200, and non-torrefied cardboard did. [ABSTRACT FROM AUTHOR]

Spent coffee grounds are a waste generated in large amounts by the food industry producing instant coffee. While it is used as animal feed, mostly spent coffee grounds are burned. In this study, The spent coffee grounds were modified to be magnetic in order to remove cadmium (II) ion. The magnetic solids are easy to separate from water with a magnet. The biochar was prepared at 400 °C. Several factors that affect the adsorption were studied, such as adsorbent dosage, contact time, initial metal ion concentration and effect of solution pH. At the optimum conditions (the adsorbent dosage 0.1 g l ^−1 , pH 7, time 30 min and the initial concentration 40 mg l ^−1 ), the percentage removal of Cd(II) was ∼96%. The surface morphology of the adsorbent showed iron particles with a cubical shape on the adsorbent, with 3–20 μ m average diameter. The adsorption data was well fit by a pseudo-second order and a Langmuir isotherm, with the maximum adsorption capacity 10.42 mg/g. The adsorption process was spontaneous and endothermic. The main goal of the study is to re-use the spent coffee grounds waste and use low-cost adsorbent for cadmium (II) removal in aqueous solution. The magnetic biochar was easily manipulated by external magnetic fields after treatment. With good adsorbent performance of the magnetic biochar, spent coffee grounds could be used to treat Cd(II) contamination.

A chelating fiber (CF), containing amine and hydroxyl groups, has been characterized and used as an adsorbent for the removal of U(VI) from aqueous solutions. The effects of pH value, contact time, adsorbent dosage, initial U(VI) concentration, temperature, and stripping agents on the adsorption behavior of U(VI) are studied. The results demonstrated that the maximum adsorption capacity is achieved at pH 3.0 and contact time 20 min. The adsorption behavior can be well described by the pseudo-second order kinetic and the Langmuir isotherm model equations. Additionally, it was found that the adsorbent can be reused for five repeating cycles. [ABSTRACT FROM AUTHOR]

Nano-Mg(OH)2, with low biological toxicity, is an ideal nano-carrier for insecticidal protein to improve the bioactivity. In this work, the adsorption features of insecticidal protein by nano-Mg(OH)2 have been studied. The adsorption capacity could reach as high as 136 mg g−1, and the adsorption isotherm had been fitted with Langmuir and Freundlich models. Moreover, the adsorption kinetics followed a pseudo-first or -second order rate model, and the adsorption was spontaneous and an exothermic process. However, high temperatures are not suitable for adsorption, which implies that the temperature would be a critical factor during the adsorption process. In addition, FT-IR confirmed that the protein was adsorbed on the nano-Mg(OH)2, zeta potential analysis suggested that insecticidal protein was loaded onto the nano-Mg(OH)2 not by electrostatic adsorption but maybe by intermolecular forces, and circular dichroism spectroscopy of Cry11Aa protein before and after loading with nano-Mg(OH)2 was changed. The study applied the adsorption information between Cry11Aa and nano-Mg(OH)2, which would be useful in the practical application of nano-Mg(OH)2 as a nano-carrier.

Heavy metal pollution has become one of the most serious environmental problems today. Keeping in view of the economic and pollution considerations; there is indeed need to develop process and practice for the waste management, for the disposal of industrial waste containing Cu(II) in a scientific manner. In the present study, sweet lime peels (SLP), an agricultural waste was utilized as an adsorbent for Cu(II) removal from aqueous solution. The biosorption mechanism and characteristics of SLP was studied by Fourier transform infrared. Kinetic studies based on pseudo-first-order and pseudo-second-order rate expressions have also been carried out. The pseudo-second-order kinetics was found to provide the best correlation with the experimental data. The effect of two parameters, namely, temperature (20, 30, 40, 50 and 60°C) and pH (2, 3, 4, 5, 6), were studied. The particle size effect in relation to biosorption capacity is also discussed. The experimental data were analysed using Langmuir, Freundlich, Redlich–Peterson, Temkin and Dubinin–Radushkevich isotherms. The Langmuir model was found to exhibit the best fit to experimental data. The maximum adsorption capacity was found to be 37.45 mg/g at 293 K. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also determined. Thermodynamic study showed that the biosorption was exothermic, spontaneous and favourable. [ABSTRACT FROM PUBLISHER]

Selenium (Se) is emerging as a contaminant that must be dealt with in many areas of the world, especially those areas impacted by past or current mining activities. In this study, we evaluate the effectiveness of synthesized nano-magnetite when used as an adsorbent to remove anionic selenium species from aqueous solutions. In conjunction with studies on the effects of pH, temperature, concentration, contact time, and presence of competing anions on selenium removal efficiency, a series of batch adsorption experiments were conducted to study adsorption isotherms and adsorptive thermodynamics. Compared with either natural magnetite (<5 μm) or nano-iron (∼10 nm), nano-magnetite (10-20 nm) was found to be a better adsorbent for selenite, while nano-iron showed better adsorption performance for selenate. From an initial selenium concentration of 100 μg-Se/L, which is comparable to those commonly found in mine water or mining impacted streams, a final concentration of <5 μg-Se/L could be achieved, using nano-magnetite. Low pH favored selenite adsorption, and elevated temperature enhanced selenium removal. Selenite adsorption followed the Freundlich isotherm model, and the presence of common anions did not significantly affect the adsorption capacity of nano-magnetite for selenite. Selective adsorption demonstrated that nano-magnetite could be a very promising nano-sorbent to treat selenium contaminated water. [ABSTRACT FROM AUTHOR]

Mesoporous molecular sieves (MCM-41) was successfully synthesized using hydrothermal synthesis and characterized by X-ray diffraction and nitrogen adsorption-desorption. Characterization results show that synthesized MCM-41 is a good adsorption material of good crystallinity, large surface area (1,040m²/g) and uniform diameter (centered at 2.8 nm). Removal of Cr (VI) from aqueous solution using MCM-41 was carried out by UV-Vis spectrophotometry. The different parameters affecting the adsorption efficiency were investigated and obtained their optimal values (pH 4, temperature 35°C, initial Cr (VI) concentration < 10 mg/L, adsorption time 2 h, adsorbent concentration of 10mg/L). It is very useful and important to dealwith Cr (VI) fromaqueous solution. The adsorption isotherm was also investigated. It is found that the adsorption isotherm follows the Langmuir model better. What's more, b of 76.71 mg-1 and q of 904 mg/g were calculated from Langmuir linear fitting. The adsorption reaction is spontaneous and endothermic as ΔG0 < 0 and ΔH0 > 0. Finally, we studied the adsorption kinetics and find that the adsorption of Cr (VI) ions onto MCM-41 is more suitable for pseudo-second-order kinetics. qe and k2 were calculated. The detailed kinetic mechanism is that film diffusion is its mainly controlling step, but intra-particle diffusion is a considerable contribution to adsorption mechanism, which must be meaningful to accelerate adsorption rate. [ABSTRACT FROM AUTHOR]

Abstract: This research involved the efficient adsorption of an anionic dye (Reactive Red 120) by natural untreated clay, a low-cost material abundant in highly weathered soils. The adsorption kinetics was investigated using the parameters such as contact time, stirring speed, initial dye concentration, initial pH, ionic strength, and solution temperature. According to these experiments the maximum removal is observed after 80 to 100min. The results showed that acid pH is favorable for the adsorption of dye and physisorption on broken edges of clay particles seemed to play a major role in the adsorption process. It was found that the rate of adsorption decreases with increasing temperature and the process is exothermic. The adsorption kinetics followed the pseudo-second-order equation for the dye investigated in this work. Furthermore the thermodynamic activation parameters such as the enthalpy and entropy were determined. Compared to adsorption experiments on other clays, the results show that the Fouchana natural clay is an efficient adsorbent for Reactive Red 120 dye. [Copyright &y& Elsevier]

Abstract: Benzoic acid removal is important for the water treatment, and adsorption is an efficient treatment process. Three kinds of modified bentonites, hydroxy-aluminum pillared bentonite (Al(OH)-Bent), octadecyl trimethyl ammonium chloride modified bentonite (OTMAC-Bent), and both octadecyl trimethyl ammonium chloride and hydroxy-aluminum modified bentonite (Al(OH)-OTMAC-Bent) were prepared and characterized by XRD, FTIR, and BET analysis. Experiments were conducted on the adsorption of benzoic acid by the prepared modified bentonites at different temperatures in batch experiments. The results show benzoic acid adsorption capabilities of Na-Bent and Al(OH)-Bent are even low, but high for OTMAC-Bent and Al(OH)-OTMAC-Bent. Optimal conditions for the adsorption of benzoic acid on OTMAC-Bent and Al(OH)-OTMAC-Bent were as follows: pH of 3.5, 0.04g/mL adsorbent, and contact time of 90min. Increased adsorption with temperature indicates that the adsorptions of benzoic acid onto Al(OH)-OTMAC-Bent and OTMAC-Bent are spontaneous and endothermic. The adsorption data could be well interpreted by the Langmuir model and Temkin Equation. The adsorption efficiency was higher than 85%, suggesting that OTMAC-Bent and Al(OH)-OTMAC-Bent are excellent adsorbents for effective benzoic acid removal from water. [Copyright &y& Elsevier]

To improve the adsorption capacity of chitosan, a novel technique for preparation of β-cyclodextrin-grafted chitosan (CD-CTS) was carried out by the reaction of β-cyclodextrin with epoxy-activated chitosan under alkaline conditions. Adsorption of Acid Red R (ARR) in aqueous solution onto CD-CTS was investigated in a batch system. Adsorption isotherm, adsorption kinetics and adsorption thermodynamics of ARR onto CD-CTS were examined. The influence factors on ARR adsorption were also investigated and described in details, such as contact time, pH value and initial ARR concentration. Equilibrium data agreed very well with the Langmuir model. Kinetic studies showed that the adsorption followed a pseudo second-order kinetic model. Thermodynamic parameters showed the endothermic heat of adsorption and the feasibility of the process. Compared with chitosan (CTS), the adsorption capacity of CD-CTS for ARR was increased by 20.2 mg/g after adsorption equilibrium. Results showed that CD-CTS is a favorable adsorbent. [ABSTRACT FROM AUTHOR]

The adsorption of Congo red from solution was carried out using calcium-rich fly ash with different contact times, concentrations, temperatures, and pHs. While the amount of dye adsorbed per unit weight of fly ash increases with increasing concentration and temperature, it decreases slightly with increasing pH. The adsorption was between 93 and 98% under the conditions studied. Kinetic studies showed that the adsorption process obeyed the pseudo-second-order kinetic model. It was also determined that the adsorption isotherm followed Freundlich and Dubinin–Radushkevich models. From thermodynamic studies, it was seen that the adsorption was spontaneous and endothermic. Desorption studies suggested that desorption was 29.18% in the presence of 0.1 N HCl and was 47.21% in the presence of CH3COOH (50% v/v). This indicated that most of the dye was held by fly ash via chemisorption as well as ion exchange. Furthermore, FTIR study also shows that a chemisorption process occurs between CR and fly ash, probably indicating dye/fly ash complexing. [Copyright &y& Elsevier]

The use of a natural Moroccan clay as an adsorbent for removal of the cationic dye methylene blue from aqueous solutions has been investigated. The starting material was activated by thermal treatment and by acid leaching with nitric acid in order to obtain samples with modified adsorption properties. The effect of the experimental conditions on the adsorption behaviour was studied by varying the treatment temperature from 373 to 1,073 K in the case of the thermally treated solids, the nitric acid concentration for the acid-activated solids and the adsorption temperature from room temperature to 368 K for both these solids. Data obtained from further batch studies were analysed using the Freundlich, Langmuir and Toth isotherm equation models. The thermodynamic parameters of the adsorption process were calculated, and the resulting Gibbs free energy indicated its spontaneity. The adsorption capacity of the clay materials makes them suitable as a low cost alternative for the removal of cationic dyes during wastewater treatment. [ABSTRACT FROM AUTHOR]