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This research explores the feasibility of using date seeds (DS), an agricultural waste, for the adsorption of malachite green (MG) dye from synthesized wastewater. The characterization of the DS before and after adsorption was accomplished by FTIR, SEM, BET, and EDX measurements. Batch adsorption experiments were investigated for MG dye adsorption from aqueous solution onto the DS. The effect of different parameters such as solution pH, adsorbent dose, contact time, temperature, and the initial dye concentration were studied. The optimum pH, adsorbent dose, temperature, and contact time for the dye removal were found to be 5, 0.1 g, 25 °C, and 30 min, respectively. The equilibrium studies for the data with Langmuir, Freundlich, and Temkin isotherms showed that Freundlich isotherm is the best model to describe the adsorption of MG onto the DS particles which has a heterogeneous surface. It was found that the adsorption process follows a pseudo-second-order kinetic model which revealed that the intra-particle diffusion stage is the rate-controlling stage for the process. The thermodynamic parameters ΔG, ΔS, and ΔH suggest the possibility of chemisorption and physisorption simultaneously and indicate the exothermic and spontaneous characters of the adsorption of MG dye on DS with negative values of ΔH and ΔG. This study used agriculture waste (date seeds) which is proved to be an environmentally friendly and low-cost adsorbent. The date seeds were shown to be a promising adsorbent, demonstrating high surface area and well-developed porosity. The prepared adsorbent will have a great impact on wastewater treatment technology and possible applications at a large scale. Thus, widespread and great progress in this area can be expected in the future. [ABSTRACT FROM AUTHOR]

Raw sago hampas (RSH) was grafted with oxygen-containing functional group through a functionalization process to form esterified sago hampas (ESH) for U(VI) adsorption and evaluated using adsorption kinetics, isotherm, and thermodynamics studies. Adsorption kinetics studies show that both adsorbents follow pseudo-second-order model while isotherm studies conclude that both adsorption processes fitted Sips isotherm model. Thermodynamic studies indicate both adsorption processes exhibited by the RSH and ESH were endothermic but spontaneous and non-spontaneous respectively. Strongs acids are tested to be the best desorption agents to release U(VI) from surfaces' of RSH and ESH. [ABSTRACT FROM AUTHOR]

Herein, poly(aniline‐co‐pyrrole) has been synthetized and investigated to adsorb phenylbutazone (PBZ), ceftiofur (CEF) and prednisolone (PRD) in aqueous medium as proof of concept. After proper adsorbent characterization, some studies were carried out in batch process, i. e., contact time, pH, and concentration. The adsorption mechanism has been conducted using kinetic and isothermal models. It was found that the reaction equilibrium was reached in 20 min for all analytes. The best fit for the experimental data were obtained employing the models of dual‐site Langmuir–Freundlich, Fritz–Schlunder and Langmuir, with R2=0.999, 0.952 and 0.974, for PBZ, CEF and PRD, respectively. For PBZ, CEF and PRD, poly(aniline‐co‐pyrrole) provided a Qmax=238.8 mg g−1 and Kmax=0.086 L g−1, Q=0.028 mg g−1 and Kmax=3.258 L g−1, Q=13.66 mg g−1 and KL=0.005 L g−1, respectively. Finally, the copolymer was evaluated in solid phase extraction, which showed recovery around 70 % for PBZ, offering also exciting opportunities for further application in the separation process. [ABSTRACT FROM AUTHOR]

The increase in the world population and the decrease in clean water resources increase people's interest in water purification technologies. Many industries, such as the textile industry, leather industry, cosmetics and food industry, color their products with substances such as dyes and pigments. In this study, a cheap, useful, innovative, environmentally friendly, and sustainable adsorbent was developed for the removal of Methylene Blue (MB), one of the dyes that is harmful to the environment. In fruit tree cultivation, in addition to the product, very high amounts of by-products/waste (branches, bark, leaves, fruit seeds, fruit shells, etc.) are produced. In this direction, walnut tree and olive tree wastes were immobilized with chitosan, made magnetic (m-WCH and m-OCH), and the adsorption of MB on the developed adsorbents was examined in a batch system. Characterization of the synthesized biocomposite adsorbents was performed by FT-IR, SEM, EDX and XRD analyzes. It has been thoroughly described how the pH solution of the MB dye compares to the pHPZC of the adsorbent surface. The pHPZC values for m-WCH and m-OCH were 5.2 and 5.5 respectively. MB adsorption of biocomposites depends on the pH of the environment (3–8), amount of adsorbent (2–10 gL−1), contact time (5–360 min), temperature (25–55 °C) and initial dye concentration (10–250 ppm) was examined as a function. The obtained data were evaluated with kinetic and isotherm models. Using adsorption equilibrium data obtained from MB adsorption studies using m-WCH and m-OCH biocomposite adsorbents, their suitability to Langmuir, Freundlich, Stachard, Dubinin–Radushkevich and Temkin models was examined. The empirical data of MB adsorption by m-WCH and m-OCH showed agreement with the Langmuir isotherm model. The maximum adsorption capacity for MB by m-WCH and m-OCH was estimated to be 85.47 mg g−1 and 53.48 mg g−1, respectively. The result showed that a higher adsorption selectivity on m-WCH compares to m-OCH. Among the kinetic models applied, the pseudo-second-order kinetic model was identified with the highest regression coefficients. In the light of these results, it was determined that there are new promising adsorbents of natural origin, with higher adsorption capacity, lower cost, and alternatives to commercially used adsorbents in the removal of MB from aqueous media. [ABSTRACT FROM AUTHOR]

The present study investigated crystal violet removal by modifying the chestnut shell with a chemical activation method. For this purpose, H2SO4 and NaOH pretreatments were applied to the chestnut shell and the pretreatment method that gave the best performance under the same conditions was determined. The best adsorption efficiency was achieved with the NaOH pretreatment (99.06%) and the crystal violet adsorption reached equilibrium within 60 min. After selecting the best chemical activation method, the modified chestnut shell was characterized before and after adsorption (FTIR and SEM). Furthermore, the effects of parameters such as pH, initial crystal violet concentration, adsorbent dosage, temperature, and contact time were observed. Moreover, isotherm, kinetics and thermodynamics of the adsorption process were researched in detail. The best results were obtained with the Langmuir isotherm model (R2=0.99) and the pseudo-second-order kinetic model (R2=0.99). Thermodynamic parameters showed that the adsorption process is spontaneous, endothermic and feasible. [ABSTRACT FROM AUTHOR]

The importance of adsorption in water purification and the need to guard against erroneous conclusions often associated with the use of equilibrium adsorption model studies in adsorption systems informed this work. Water purification by adsorption of Congo red (CR) from synthetic aqueous solution to acid treated corncob charcoal (ATCC) was carried out at three different pH values (8.0, 10.5, and 12.0) and at temperatures 10–40 °C. The maximum adsorption capacity of ATCC for CR was 85.8 mg/g at pH 12. The resulting data from the batch adsorption studies were plotted at different temperatures and were fitted to linear form of three isotherm models; Freundlich, Langmuir, and Temkin. Though all three models fitted the experimental data linearly, only Langmuir model was able to account for the observed thermodynamic behavior of the adsorbent–adsorbate systems under the pH conditions. The standard enthalpy values for the adsorption of CR on ATCC at pH 8.0, 10.5, and 12.0 were −5.010 ± 0.312, −7.024 ± 0.440, and −71.426 ± 3.130 kJ mol−1, respectively. The corresponding entropies at pH 8.0, 10.5, and 12.0 were 98.7 ± 1.0, 87.8 ± 1.5, and 129.0 ± 10.5 J mol−1 K−1, respectively. The effect of pH on the thermodynamic quantities were rationalized on the basis of the type of interaction between the CR and the adsorbent. To determine the most suitable model, it was important to juxtapose the observed dependence of adsorption affinity on temperature with the thermodynamic information of the adsorption studies. [ABSTRACT FROM AUTHOR]

In this study, a novel nanoadsorbent material is developed using plant waste dead bark of Azadirachta indica plant and activated with phosphoric acid. By using FTIR, XRD, UV–vis, FESEM, BET, and TEM analytical tools, the structural and morphological features of the prepared nanoadsorbent were investigated, and the adsorption capability was tested for the removal of a cationic dye methylene blue (MB) from an aqueous solution. N2 sorption study confirmed that the nanoadsorbent structure is composed of 2–50 nm diameter size of pores and illustrated a type IV isotherm with H3 type of hysteresis loop. Batch experiments performed for adsorption isotherm investigation revealed that the sorption equilibrium was achieved within 80 min at pH = 11 when used 30 mg of adsorbent in 50 mL of dye solution (30 mg/L) at room temperature. In 80 min of contact time, 99.49% adsorptive removal of MB dye was achieved at optimized adsorption operational parameters. The adsorption process of MB dye was exhibited better agreement with the Langmuir isotherm model, and the utmost adsorption capability was estimated to be 106.92 mg/g at 303 K. The kinetics of adsorption process was well followed to the pseudo-second-order kinetics and the adsorption of MB dye molecules on the developed nanoadsorbent was found to be directed by the intra-particle diffusion (IPD) process but it was not a sole directing factor. The thermodynamic investigation of adsorption study revealed that the process was spontaneous and endothermic, and increased randomness at the adsorbate-adsorbent interface. The recyclability study performed in four successive cycles established the stability and reusability of adsorbent which retained nearly 90% adsorption ability after fourth run of reuse. [ABSTRACT FROM AUTHOR]

Heavy metal contamination is a major concern, and the adsorption process is regarded as one of the most efficient water remediation processes to deal with it. Herein, we modified fly ash by a microwave-assisted hydrothermal process to enhance its adsorption capacity and tested the material toward Cd(II) and Cu(II). Characterization of the adsorbents was performed by several techniques in detail to elucidate considerable structural changes such as cracking of spherical morphology, increase in surface area and changing of the chemical composition. Then batch adsorption was performed under different conditions to investigate the equilibrium, kinetics, and thermodynamics of the process. NaOH-modified fly ash considerably has a higher adsorption performance than that of the as-received sample for both ions. The highest adsorption capacity of modified fly ash was achieved as 133.8 and 95.7 mg/g for Cd(II) and Cu(II), respectively. The kinetics and isotherms could be perfectly reflected by a pseudo-second-order rate equation and the Freundlich model, while thermodynamics confirmed the endothermicity of the process. [ABSTRACT FROM AUTHOR]

SBA‐15/polypyrrole composite was synthesized by polymerizing pyrrole in the presence of SBA‐15. The samples were characterized using the following techniques: low‐angle XRD, wide‐angle XRD, FTIR, FESEM, TGA, HRTEM, and BET. From the low‐angle XRD analysis, it confirms the formation of a mesoporous hexagonal structure (p6 mm). From the HRTEM image, an orderly arrangement of mesopores is evident. Using adsorption techniques, our objective is to remove sunset yellow, indigo carmine, titan yellow, and orange G dye from aqueous solutions with SBA‐15/polypyrrole composite. The removal efficiency for all the dyes was greater than 90 %. The isotherm was verified to follow the Langmuir isotherm model. The maximum adsorption capacities for sunset yellow, indigo carmine, titan yellow, and Orange G were found to be 78.74 mg/g, 83.33 mg/g, 78.74 mg/g, and 106.38 mg/g, respectively. The adsorption kinetics followed a pseudo‐second‐order model, and the R2 value was greater than 0.99 for all the dyes. The thermodynamic parameters of ΔG°, ΔS°, and ΔH° showed negative values, indicating that the adsorption was spontaneous, decreased entropy, and was exothermic. The recycling of the SBA‐15/polypyrrole composite resulted in a 90 % removal efficiency for three cycles. Therefore, the present adsorbent could be applied to treat industrial effluents that contain these dyes. [ABSTRACT FROM AUTHOR]

The rapid growth of the dye and textile industry has raised significant public concerns regarding the pollution caused by dye wastewater, which poses potential risks to human health. In this study, we successfully improved the adsorption efficiency of activated carbon derived from pomegranate peel waste (PPAC) through a single-step and surface modification approach using 5-sulfonate-salicylaldehyde sodium salt. This innovative and effective sulfonation approach to produce sulfonated activated carbon (S-PPAC) proved to be highly effective in removing crystal violet dye (CV) from polluted water. The prepared PPAC and S-PPAC were characterized via FESEM, EDS, FTIR and BET surface area. Characterization studies confirmed the highly porous structure of the PPAC and its successful surface modification, with surface areas reaching 1180.63 m2/g and 740.75 m2/g for the PPAC and S-PPAC, respectively. The maximum adsorption capacity was achieved at 785.53 mg/g with the S-PPAC, an increase of 22.76% compared to the PPAC at 45 °C. The isothermic adsorption and kinetic studies demonstrated that the adsorption process aligned well with the Freundlich isotherm model and followed the Elovich kinetic model, respectively. The thermodynamic study confirmed that the adsorption of CV dye was endothermic, spontaneous and thermodynamically favorable onto PPAC and S-PPAC. [ABSTRACT FROM AUTHOR]

Ideal Adsorbed Solution Theory (IAST) is a common method for modelling mixture adsorption isotherms based on pure component isotherms. When the adsorbent has distinct adsorption sites, the segregated version of IAST (SIAST) provides improved adsorbed loadings compared to IAST. We have adopted the concept of SIAST and applied it to an explicit isotherm model which takes into account the different sizes of the adsorbates: the so called Segregated Explicit Isotherm (SEI). The purpose of SEI is to have an explicit adsorption model that can consider both size-effects of the co-adsorbed molecules and surface heterogeneities. In sharp contrast to IAST and SIAST, no iterative scheme is required in case of SEI, which leads to much faster simulations. A comparative study has been performed to analyse the adsorption isotherms calculated using these three methods. The adsorbed loadings predicted by SEI and SIAST are in excellent agreement with the Grand-Canonical Monte Carlo (GCMC) simulation data. The loadings estimated by IAST show considerable deviations from the GCMC data at high pressures. Breakthrough curve modelling is used to compare the effects of these three models at dynamic conditions. The explicit model (SEI) leads to the fastest simulation run time, followed by SIAST. [ABSTRACT FROM AUTHOR]

In this study, the removal of heavy metals Pb(II), Cr(III), Zn(II) and Co(II) in wastewater with activated carbon (KB-A) obtained by boric acid impregnation to poplar sawdust (K-S) grown in the Van region was investigated. The parameters affecting adsorption were examined and optimum values were determined. For this purpose, the effects of different parameters such as solution pH, KB-A dosage, contact time and metal concentration were studied for their effects on the removal of heavy metals. As a result of the adsorption process, It was observed that the adsorption of all metals decreased with increasing temperature. The adsorption process was found to follow the Langmuir and Freundlich models. The maximum adsorption capacity values were determined as 30.89 mg g-1 for Cr(III), 30.49 mg g-1 for Pb(II), 30.30 mg g-1 for Zn(II) and 27.70 mg g-1 for Co(II). According to the thermodynamic parameter results, the adsorption process was spontaneous, and the reaction followed a pseudo-second-order kinetic model. The KB-A adsorption ability showed a trend ordered from large to small as Cr(III)˃ Pb(II) ˃Zn(II) ˃ Co(II). [ABSTRACT FROM AUTHOR]

Levofloxacin (LEV) is an important and widely used antibiotic. It is used to treat many bacterial infections. It may be found in water sources as a result of incomplete metabolism in humans and other sources. In this study, the adsorption of Levofloxacin by raw rice husk (RRH) was investigated. The effect of pH, time, temperature, RRH weight, and initial Levofloxacin concentration on the adsorption process were determined. Kinetic, isotherm and thermodynamic models were studied to explain the Levofloxacin adsorption mechanism on raw rice husk. The results of adsorption kinetics and isotherms revealed that the adsorption of LEV by RRH was better fitted with the Intraparticle model with coefficient of determination (R ² =96%), while the Langmuir model represents the best isotherm model to describe the adsorption process with (R ² =95%). The removal efficiency reached 99%, the monolayer maximum uptake qmax is 2.47 mg/g and the adsorption intensity parameter (1/n) value is 0.763, which means that the adsorption is favorable. According to the thermodynamic coefficients, the adsorption process was spontaneous and feasible for the temperatures under investigation; the sorption efficiency was more favorable at higher temperatures, and the adsorption process is endothermic. [ABSTRACT FROM AUTHOR]

• System development of water adsorption on zeolite 13X from moist air was proposed. • A novel adsorption heat pump system was assessed experimentally and numerically. • Supplying moist air up to 95 °C increased the bed temperature to 200 °C. • At 70 °C, both linear driving force and the Arrhenius correlations approached the tendency. • Linear driving force model resulted more appropriate under any conditions. This work investigated the generation of high-temperature steam by feeding saturated moist air through a steam generation system containing a zeolite 13X packed bed. The use of moist air was a unique aspect, which demonstrated a novel approach to steam generation system design. The issue with the steam generation system in previously existing published research works is that it needs high regeneration energy. In order to solve this issue, it is desirable to employ moist air as the working medium. In order to better understand the physical processes involved, numerical modeling of zeolite energy storage was also performed in addition to the experimental work. As the result, when the temperature of the moist air was raised from 30 to 95 °C, the maximum temperature of the resulting water vapor reached to about 200 °C. The maximum temperature of the water vapor was not greatly affected by the superficial velocity of the moist air between 0.108 and 0.216 m N /s. In the case that the moist air temperature was high, the maximum temperature of water vapor could be predicted based on correlations between the heat balance and adsorption equilibrium, assuming that temperatures of the moist air and zeolite were identical. The numerical technique also included a comparison between Arrhenius and linear driving force models. At higher temperature input moist air, both models resulted the close tendency. [ABSTRACT FROM AUTHOR]

The current study examined the use of Sansevieria plant leaves extract as an environmentally acceptable, inexpensive, and safe green approach for creating titanium dioxide nanoparticles (NPs). Batch studies have been used to test the particles' capacity to bind to the azo dye congo red (CR), which has been adsorbed from its aqueous solution. The effects of many factors, including the weight of TiO2 NPs, the contact duration to reach equilibrium, the concentration of CR, temperature, and pH, have been investigated. Both the Freundlich and Langmuir models were used to analyze experimental results. According to the high values of the Freundlich model's correlation coefficient R², it is discovered that the adsorption of CR dye onto nano TiO2 is well-suited. The kinetics analysis for the adsorption trials proposed the pseudo-second-order. Thermodynamic data showed that the CR dye adsorption onto nano TiO2 is a physical process that happens spontaneously and endothermically with increasing unpredictability. [ABSTRACT FROM AUTHOR]

This study aims to investigate the adsorption characteristics of tetracycline from polluted waters using C-4- hydroxyphenylcalix[4]resorcinarene as an adsorbent. The adsorptive efficiency of C-4-hydroxyphenylcalix[4]resorcinarene is optimized by adjusting various operational parameters such as the adsorbent dosage, the pH, the contact time, the temperature, and the initial adsorbate concentration. The most efficient remediation is 96% at 10.0 mg/L tetracycline as the initial concentration, 0.05 mg/L C-4-hydroxyphenylcalix[4]resorcinarene, a contact time of 30 min, pH 5.6, and ambient temperature. The adsorption ability of C-4-hydroxyphenylcalix[4]resorcinarene toward tetracycline is also investigated in water with different characteristics, including solutions with and without the addition of background salts. The results show that C-4-hydroxyphenylcalix[4]resorcinarene can effectively remove tetracycline from aqueous solutions with an adsorption capacity of ca. 36.9 mg/g. The study also finds that the removal process followed pseudo-second order kinetics and Freundlich isotherm models. Moreover, the adsorption is spontaneous and exothermic, suggesting a thermodynamically favorable chemisorption process. In addition, the optimized method is successfully applied to remove tetracycline from various real natural water systems. [ABSTRACT FROM AUTHOR]

Natural mulberry leaves and carboxylic acid-modified mulberry (Morus alba L.) leaves were used for the first time to scrutinize the effects of modification on the retention efficiency of an anionic dye (Remazol Brilliant Blue R (RBBR)) from aqueous solutions to suggest an economical and promising adsorbent for the treatment of dye-contaminated water. The characterization of the adsorbents was accomplished through common techniques including SEM, FTIR, and pHpzc determination. Several parameters studied in batch experiments pointed out that the initial pH of 2.0 and the contact time of 240 min were optimum conditions for all the developed RBBR uptake processes. An artificial neural network (ANN) model was applied to formulate a forecast model for the uptake efficiency of RBBR. The experimental data were assessed by different kinetic and isotherm models to explain the mechanism of the developed processes in more detail. Maximum monolayer adsorption capacities of natural mulberry leaves and acetic acid-, citric acid-, and oxalic acid-modified mulberry leaves were determined as 64.5, 95.2, 84.8, and 91.7 mg g-1, respectively, by the Langmuir isotherm model. These results demonstrated that the modification with carboxylic acids significantly increases the anionic dye adsorption capacity of the mulberry leaves. [ABSTRACT FROM AUTHOR]

The desiccant dehumidification system can separate the latent heat and sensible heat in the air-conditioning system and achieve energy savings by removing latent heat. Industrial waste heat and renewable energy could be utilized in desiccant dehumidification systems, where the desorption process can be performed below 70 °C. The vapor pressure and temperature of the regenerating air dictate the desorption process corresponding to the isotherm properties. This study has focused on the effects of various temperatures and humidity ratios of regeneration air on the performance of a desiccant dehumidifier using a polymer as an adsorbent. Experiments were performed using the regeneration air with the humidity ratios of 0.005 kg kg−1, 0.010 kg kg−1, 0.015 kg kg−1, and 0.020 kg kg−1, while the air temperatures were varied from 40 °C to 70 °C. The evaluation of this study employs the adsorption/desorption amount, average moisture removal capacity, and latent energy ratio (LER) of the regeneration process as key performance indexes. At the regeneration temperature of 68 °C, the peak desorption amount at the humidity ratio of 0.005 kg kg−1 and 0.010 kg kg−1 both reached 0.011 kg kg−1. The results indicated that the higher desorption temperature led to a higher desorption amount. Besides, with the increased desorption temperature, the average moisture removal capacity increases. In contrast, the high humidity ratio of regeneration air resulted in a weak dehumidification ability. Lower regeneration temperature was difficult to apply to regenerate the polymer-based desiccant under a high-humidity-ratio atmosphere. To attain a high LER, a lower humidity ratio of dry air and regeneration temperature was preferred. The regeneration air with a humidity ratio of 0.020 kg kg−1 is not suitable to apply in the dehumidification system in the temperature range of 40–70 °C. [ABSTRACT FROM AUTHOR]

In this study, a modified metal hydroxides on surface of Lewatit resin (HMO @LM500, where M indicates to Al, Fe, Mn or Zn) were designed and used as efficient adsorbents for uranium (U(VI)) ions capture from aqueous solution. The prepared materials were characterized by using transform infrared spectroscopy, scanning electron microscope, energetic dispersive x-ray techniques. Batch adsorption methods were done to investigate all factors affecting adsorption process such as the effect of pH, concentration, contact time and temperature. Optimum values of each parameter were calculated as pH of 1.8, temperature of 298 K (25 °C), contact time of 60min for the removal of uranium ions. Analysis within the nonlinear isotherm models indicates that the Liu model offers the best description for the equilibrium data since it has the highest R² value and the lowest error analysis value when compared with the other models. The calculated adsorption capacity of Liu model is 217.06mg g-1, whereas analysis within the nonlinear kinetic models indicate that pseudo-second-order behavior is involved. The thermodynamic examination of the equilibrium data proved that the adsorption process of U(VI) was found to be a spontaneous and exothermic process. The ΔH0 and ΔS0 parameters were calculated as ~66.5827 kJ mol-1 and ~0.2051 kJ mol-1 K-1, respectively. Therefore, the prepared adsorbent can be applied to capture of U(VI) ions from aqueous medium. [ABSTRACT FROM AUTHOR]

The study of the adsorption efficiency of new carbon/CNT composites was undertaken to remove a cationic dye, Rhodamine B (RhB), from dye-contaminated wastewater. Indeed, we investigated the effect of different experimental parameters such as time, initial concentration of dye and temperature on the adsorption of RhB by the carbon composites (KS44-0 and KS44-20). The results showed that the adsorption uptake increased with the initial concentration and solution temperature while maintaining a relatively constant pH. The presence of the carbon nanotubes provided more active sites for dye removal and improved the adsorption behavior of Rhodamine B dye. The analysis of the experimental data was conducted using model equations, such as Langmuir, Freundlich and Temkin isotherms. As regards the Freundlich isotherm model, it was the best fit for the equilibrium data obtained from the experiments. The applicability of the pseudo-second-order equation could be explained assuming that the overall adsorption rate is limited by the rate of adsorbate transport that occurs on the pore surfaces of adsorbents. Furthermore, the intraparticle diffusion and Bangham models were used to investigate the diffusion mechanism of RhB absorption onto carbon composites. They showed that multiple adsorption stages occurred simultaneously via pore surface diffusion. Concerning the thermodynamic parameters (∆G°, ∆H°, and ∆S°), they were calculated and explained in the mean of the chemical structure of the adsorbate. Negative standard Gibbs free energy change values (ΔG°ads) at all temperatures suggested that the adsorption process was spontaneous, and the positive values of the standard enthalpy change of adsorption (∆H°ads) revealed the reaction to be endothermic. The values of standard enthalpy (ΔH°ads) and activation energy (Ea) indicated that the adsorption process corresponds to physical sorption. The mechanisms for the removal of Rhodamine B dye from wastewater using carbon composite were predicted. RhB is a planar molecule that is readily adsorbed, in which adsorbed molecules are bound by hydrophobic or other weak interactions due to the π-π interactions between the dyes' aromatic backbones and the hexagonal skeleton of graphite and carbon nanotubes. Thus, the graphite carbon/carbon nanotube composite is believed to play a major role in organic pollutant reduction. [ABSTRACT FROM AUTHOR]

This contribution is focused on the examination of adsorption/desorptiom isotherms for nitrogen at 77 K and benzene vapors at 293 K on various hypercrosslinked polystyrene (HP) resins. All isotherms for N2 are identical in their shapes and are characterized by a steep rise of the adsorption branch at low p/p0 followed by a less steep hoisting of the branch with increasing relative pressure. Adsorption isotherm for benzene demonstrates an ill-defined convex initial part followed by a significant rise in network loading with further increase in relative pressure. In the both cases we assume the rise in adsorption to reflect the relaxation of inner stresses with the simultaneous increase in the volume of networks. The distinction between the two types of isotherms is conditioned upon the fact that in the networks cooled down to 77 K stresses are stronger and the initial volume of the sample is more compressed. The amounts of nitrogen and benzene absorbed at relative pressure of 0.95 are the same order of magnitude, indicating similar swelling of HP in the both adsorbates. The adsorption behaviors of hypercrosslinked PIM-type polymers are governed by the same effects. [ABSTRACT FROM AUTHOR]

The present study reports the cymoxanil adsorption efficiency on carboxy-carbon nanotubes (CNT-COOH)/manganese(IV) oxide (MnO2)/iron(II,III) oxide(Fe3O4) nanocomposite. The optimum conditions were determined by studying the influence of pH (2-10), temperature (20-60 °C), initial cymoxanil concentration (7-20 mg L−1), adsorbent dose (0.5-5 g L−1) and contact time (2-30 min) on the adsorption process. The isotherm and kinetic models were used to analyze the experimental data. The Langmuir isotherm model was shown to provide the best fit with a 10.672 mg g−1 maximum adsorption capacity. Also, the cymoxanil adsorption follows the pseudo-second order kinetic model. According to these results, the CNT-COOH/MnO2/Fe3O4 nanocomposite may be used for cymoxanil removal from aqueous solution. [ABSTRACT FROM AUTHOR]

A novel adsorbent-activated carbon-loaded cellulose composite bead (AC-CCB) was synthesized by sol-gel conversion for the removal of methylene blue (MB) from an aqueous solution. The adsorbent was characterized by Fourier transform-infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and X-ray energy dispersive spectroscopy (EDAX). The maximum dye removal was found to be 96.5, 92.3, and 81.8 %, corresponding to MB concentrations of 25, 50, and 100 mgL-1, respectively. Isotherm and the kinetic study were carried out with an AC-CCB dose of 1.0 g L-1, a shaking speed of 125 rpm, and the initial MB concentration ranging from 25-100 mg L-1. In order to study the kinetics of MB adsorption onto AC-CCB, the temperature was fixed at 298 K, whereas, for the isotherm study, the temperature varied from 298 to 318 K. The process followed pseudosecond-order kinetics with rate constant (k2) 28.7x10-2, 11.1x10-2 and 9.41x10-2 g.mg.min-1 corresponding to MB concentration of 25, 50 and 100 mg L-1. Freundlich, Langmuir, and Sips models were found to fit well with the adsorption data. The negative values and the positive values suggested that the adsorption of MB onto AC-CCB was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

This research aimed to assess the adsorption properties of raw walnut shell powder (WNSp) for the elimination of methylene blue (MB) from an aqueous medium. The initial MB concentration (2–50 mg/L), the mass of the biomaterial (0.1–1 g/L), the contact time (10–120 min), the medium's pH (2–12), and the temperature (25–55 °C) were optimized as experimental conditions. A maximum adsorption capacity of 19.99 mg/g was obtained at an MB concentration of 50 mg/L, a medium pH of 6.93 and a temperature of 25 °C, using 0.2 g/L of WNSp. These conditions showed that the MB dye elimination process occurred spontaneously. Different analytical approaches were used to characterize the WNSp biomaterial, including functional groups involved in MB adsorption, the surface characteristics and morphological features of the WNSp before and after MB uptake, and identification of WNSp based on their diffraction pattern. The experimental isotherm data were analyzed by the Langmuir and Freundlich models for the adsorption of MB dye. The corresponding values of parameter RL of Langmuir were between 0.51 and 0.172, which confirmed the WNSp's favorable MB dye adsorption. The experimental kinetic data were examined, and the pseudo-second-order model was shown to be more suitable for describing the adsorption process, with an excellent determination coefficient (R2 = 0.999). The exchanged standard enthalpy (H° = −22.456 KJ.mol−1) was calculated using the van 't Hoff equation, and it was proven that the adsorption process was exothermic. The spontaneous nature and feasibility of the MB dye adsorption process on WNSp were validated by negative standard enthalpy values (G°) ranging from −2.580 to −0.469 at different temperatures. It was established that WNSp may be employed as a novel, effective, low-cost adsorbent for the elimination of methylene blue in aqueous solutions. [ABSTRACT FROM AUTHOR]

The chemically modified Muscovite adsorbent was prepared by activation of Muscovite with HCl and H2O2, and used for the adsorption of Rhodamine-B dye removal (RB) from polluted water. Optimum conditions were applied for maximum RB dye adsorption (solution temperature, adsorbent dose, pH, stirring time, and initial dye concentration). The results show that the maximum adsorption of RB dye (21.22 mg g-1) was achieved using a Muscovite adsorbent prepared with a mixture of HCl/H2O2. The maximum adsorption of RB dye by activated Muscovite adsorbent was 88.2 % at initial RB concentration 50 ppm, 60 min contact time, 25°C, adsorbent dose 1 g 50 mL-1, and pH 4. The adsorption kinetics studies show that the RB adsorption follows the pseudo-secondorder kinetic model. Adsorption isotherm models were investigated and ended to that the adsorption of RB dye by the activated Muscovite fitted well Langmuir adsorption isotherm. The thermodynamics parameters of RB dye adsorption using activated Muscovite indicated spontaneous and endothermic processes. [ABSTRACT FROM AUTHOR]

The present investigation was carried out to evaluate the performance of copper modified zeolite-13X as an adsorbent for the removal of Fipronil (FP) pesticide from synthetic wastewater. The experiments on adsorptive removal were carried out varying different parameters such as pH of the solution (1 pH-10 pH), contact time (20 min – 120 min), stirring speed (50 rpm −200 rpm), a dose of adsorbent (1 g/L to 4 g/L), initial concentration of the solution (500 mg/L to 1000 mg/L). The removal of FP pesticide from its aqueous solution was found to be maximum i.e. 92.3%. At optimum pH 3, 84.2% removal of Fipronil was obtained. The removal of Fipronil decreases with the increase in the initial concentration of pesticides. The effect of temperature on Fipronil removal was also studied. At 25°C, the maximum percent removal is reported to be 92%. Also, the maximum removal is 92.3% at an optimum stirring speed of 200 rpm. The Freundlich isotherm fitted the experimental data well whereas the process of adsorption obeyed second-order kinetic model. The thermodynamics study of adsorption was also carried out. The results of the investigation revealed that copper-doped zeolite could be used as a potential sorbent towards the eradication of Fipronil pesticide from wastewater. [ABSTRACT FROM AUTHOR]

Waste from electrical and electronic equipment (WEEE) is constantly increasing in quantity and becoming more and more heterogeneous as technology is rapidly advancing. The negative impacts it has on human and environment safety, and its richness in valuable rare earth elements (REEs), are accelerating the necessity of innovative methods for recycling and recovery processes. The aim of this work is to comprehend the adsorption and release mechanisms of two different solid sorbents, activated carbon (AC) and its pentaethylenehexamine (PEHA)-modified derivative (MAC), which were deemed adequate for the treatment of REEs deriving from WEEE. Experimental data from adsorption and release tests, performed on synthetic mono-ionic solutions of yttrium, neodymium, and lanthanum, were modelled via linear regression to understand the better prediction between the Langmuir and the Freundlich isotherms for each REE-sorbent couple. The parameters extrapolated from the mathematical modelling were useful to gain an a priori knowledge of the REEs–sorbents interactions. Intraparticle diffusion was the main adsorption mechanism for AC. PEHA contributed to adsorption by means of coordination on amino groups. Release was based on protons fostering both a cation exchange mechanism and protonation. The investigated materials confirmed their potential suitability to be employed in real processes on WEEE at the industrial level. [ABSTRACT FROM AUTHOR]

In this study, a water- and heavy hydrocarbon-removal process of a natural gas refinery currently in operation using the temperature swing adsorption method is modeled and investigated. The aim of this process is to decrease the hydrocarbon dew point to −10 °C and diminish the water content of the gas to about 0.1 ppm. This unit consists of four beds with two layers in which two beds are in the adsorption state, while the others are kept in the regeneration state. The gas composition and the bed specification are obtained from the available data from the refinery. The Ergun equation is considered for the pressure drop calculation. The results show that the developed model can predict the outputs with good accuracy. Sensitivity analysis of operating condition parameters such as temperature, pressure, and regeneration gas flowrate are carried out. Analysis of the regeneration temperature proved that temperature reduction from 268 °C to 210 °C can improve recovery of the heavy components. In addition, the regeneration gas flow rate can be reduced to about 0.4 kmole·s−1 as an optimum value. Moreover, 303 to 310 °C is the optimum range for the feed temperature. Due to the presence of the air cooler in the upstream process, and according to the ambient air temperature, feed temperature can be decreased to obtain better results. [ABSTRACT FROM AUTHOR]

Methylene blue (MB) immobilized onto a sulfonated poly(glycidyl methacrylate) (SPGMA) polymer composite has been developed as a novel adsorbent for water treatment applications. The MB adsorptions onto sulfonated poly(glycidyl methacrylate) polymer characters have been studied. The adsorption isotherms, namely Langmuir and Freundlich, have been investigated. Other isotherm models. As a compromise between the Freundlich and Langmuir isotherm models, such as the D–R isotherm and the Temkin isotherm, have been compared. The results indicated that the adsorption process followed the Freundlich isotherm model, indicating heterogeneous surface site energies and multi-layer levels of sorption. This study selected three linear kinetic models, namely pseudo-first order, pseudo-second order, and Elovich, to describe the MB sorption process using SPGMA negatively charged nanoparticles (430 nm). The obtained data revealed that the adsorption process obeyed the pseudo-second-order kinetic model, suggesting that the rate-limiting step in these sorption processes may be chemisorption. Furthermore, the thermodynamic parameters have been evaluated. Moreover, the interaction of the MB molecules with SPGMA nanoparticles has been simulated using the governing equation that describes ion exchange resin derived from Nernst—Plank equations between two ion species. Finally, the developed MB-SPGMA composite adsorbent (27 mg/g) wastested for the first time for the removal of Cr6+ ions and Mn7+ metal ions from dichromate and permanganate-contaminated waters under mild adsorption conditions, opening a new field of multiuse of the same adsorbent in the removal of more than one contaminant. [ABSTRACT FROM AUTHOR]

In this study, the performance of chitosan based semi-IPN nanocomposite hydrogels for the adsorptive removal of basic violet 14 (BV14) from aqueous solution has been explored. Batch adsorption studies were conducted to determine the effect of various parameters on BV14 adsorption, and optimum values were reported as pH of 8, the adsorbent dosage of 0.025 g, initial BV14 concentration of 5 mg L-1 and contact time of 90 min at a temperature of 25 °C. The semi-IPN hydrogel containing 0.5% by weight GO showed the improved adsorption capacity for BV14 compared to the neat hydrogel adsorbent, and the maximum adsorption capacity was 276.21 mg g-1 with a removal efficiency of 90.4%. Kinetic studies have shown that the pseudo-second-order kinetic model can well describe BV14 adsorption. The equilibrium adsorption data showed the best fit with the Langmuir model. Thermodynamic studies revealed that BV14 adsorption was physical in nature and occurred spontaneously and endothermically. The BV14 removal efficiency above 84% was obtained after five consecutive adsorption-desorption cycles, which has proved the reusability performance of the adsorbent and the recovery potential of BV14 dye. Overall, the results of this study indicated that GO containing chitosan based semi-IPN nanocomposite hydrogel could be an effective and environmentally friendly adsorbent for the successful removal of BV14 molecules from aqueous solution. [ABSTRACT FROM AUTHOR]

• Intermittent characteristics of hybrid adsorption-compression systems are examined. • The hybrid system under intermittent mode exhibits a daily energy saving of 37%. • The system performance under intermittent mode outperforms the continuous operation. • PCM has significantly reduces the compressor on-time operations. • PCM is incorporated into the system to curtail the cyclic temperature fluctuations. In the current study, intermittent characteristics of hybrid adsorption-compression refrigeration systems are evaluated, notably for cold storerooms. This hybrid system utilizes ultra low-grade heat (65 °C) and works with natural refrigerants. Herein, the dual-bed adsorption system operates with a working pair of silica gel/water (R718), while isobutane (R600a) is adopted for the compression system. Phase change material (PCM) is additionally incorporated to prolong the compressor off durations and improve the stabilization of the air temperature inside the cold storeroom. Mathematical modeling of the proposed systems is established using MATLAB/SIMULINK framework and validated with relevant literature. An examination of the temporal behavior of the hybrid system's leading indicators such as temperature profiles, cooling capacity, COP, electric power, and electricity demand based on the intermittent characteristics has been conducted and compared against the baseline system. The results demonstrate that the energy saving of the hybrid system during the intermittent operation mode (37%) outperforms the continuous operation mode (31.63%). Also, the hybrid system at the steady-state stage attains COP of ∼4 compared to ∼2.3 for the baseline system. However, incorporating PCM into the hybrid system abates the air temperature fluctuation inside the cold storeroom, diminishes the cyclic operations, and reduces the on-time ratio by 24.1% compared to the baseline system (34.8%) while slightly reducing the system COP. The utilization of hybrid refrigeration systems accompanied by PCM has significant profit over conventional compression systems in the market. [ABSTRACT FROM AUTHOR]

Heavy metals such as zinc in untreated industrial effluents cause diseases and disorders in living organisms. They cannot be degraded like organic contaminants and hence have to be removed. Though physical and chemical methods are available for their removal, most of them are not economical and eco-friendly. Hence, a suitable technique is necessary to minimize the deleterious effects of dispersion of heavy metals in ecosystems. Though zinc serves as a micronutrient, it becomes toxic in higher concentrations. Bacteria can be used in the removal of zinc and the process is economical and ecofriendly. Hence, in the present study, we tested zinc removal efficiency of Bacillus subtilis (MTCC 2423) for various concentrations viz. 100, 200, 300, 400 and 500 ppm of zinc in nutrient broth for a period of 10 days. Samples were tested for the zinc level every two days in each concentration and the maximum removal was noticed after six days of treatment. With the increase in zinc concentration, both biomass and zinc removal efficiency showed an increase. Autoclaved cells showed maximum zinc removal when compared with other cell types. Among the other heavy metals tested, iron enhanced the biomass of B. subtilis during zinc treatment and the results are discussed. [ABSTRACT FROM AUTHOR]

Nonsteroidal anti-inflammatory drugs (NSAIDs) are highly consumed around the world and consequently found as emerging pollutants in water; they are found in concentrations up to µg L−1 making their removal a priority. In this matter, adsorption is an efficient alternative for drug removal, so using activated carbon (AC) as an adsorbent is a highly explored subject. The current interest is to obtain AC from waste, for example, those of agro-industrial origin, reducing this way the overall costs of the process. Although information regarding the use of AC from agro-industrial origin in the removal of NSAIDs is limited, an exclusive compilation is required to understand the state of the art to date. This work aims to update information related to the adsorption of ibuprofen, diclofenac, and naproxen on agro-industrial AC, and it is focused on the period 2016–2021. It highlights the characteristics of agro-industrial AC responsible for efficient adsorption. Recent adsorption studies, including kinetics, isotherms, and thermodynamics, are analyzed and compared. Progress on removing NSAIDs from real wastewater is also presented and finally proposed adsorption mechanisms and costs related to these removal processes. [ABSTRACT FROM AUTHOR]

This study investigated the performance of lemongrass (Cymbopogon nardus) leaves biowaste (LLB) to adsorb methylene blue (MB) dye from an aqueous solution using the batch method. Batch experiments were conducted in order to evaluate the effect of initial MB concentration, pH, contact time, and temperature. Point of zero charge measurement demonstrated that the LLB is anionic in a wide range of pH values (pH > 6.7) that support the adsorption of cationic contaminants. The adsorption process pursued Langmuir isotherm (R2 = 0.9960) and pseudo-second-order kinetic model (R2 = 0.9960) best fitted with a maximum capacity of 43.16 mg g−1 at room temperature. The adsorption process was spontaneous and exothermic. FT-IR spectra and SEM-EDX characterization before and after adsorption affirmed the interaction of MB dye onto the LLB. It is suggested that the adsorption of the dye proceeds via electrostatic attraction, cationic exchange, π-π bonding, and hydrogen bonding, while the role of pore filling is modest. LLB has good reusability, as evidenced by four cycles of desorption using 30% acetic acid as the eluent. The optimum conditions were applied to real wastewater with a removal efficiency was 93.58% at pH 9. Therefore, the LLB could be an effective adsorbent for removing MB dye from wastewater. [ABSTRACT FROM AUTHOR]

The binary adsorption isotherms of volatile organic compounds (VOCs), and water vapor from the air have been the focus of much research in recent years. The content of adsorbed VOCs in the presence of water vapor can be determined by the volumetric or gravimetric method, in a static or dynamic mode. This study focuses on the adsorption technique in a static mode for isotherm measurement of the co-adsorption of VOCs and water vapor from the air using the gravimetric method. The content of VOCs is determined using a total organic carbon analyzer, while the amount of the adsorbed water was calculated from the difference between total adsorption (VOCs and water) and the adsorbed VOCs. This paper presents several adsorption isotherms with different VOCs (toluene, benzene, methanol, ethanol and isopropyl alcohol) and adsorbents (ZSM-5 zeolite, silica gel and Na-Form mordernite) in the presence of water vapor. The well-known adsorption isotherm models (Langmuir, extended Langmuir, Freundlich, extended Freundlich and Hill) were used to treat experimental results. The adjusted R-Squared (adj. R2) values obtained for those non-linear models for isotherms (total adsorpton (qe,tot) as a function of equilibrium concentration of VOC (Ce) and the adsorbed VOC (qe) as a function of equilibrium concentration of VOC (Ce) are used to determine the best-fit isotherm model. The modeling results showed that the 3-parameter models could fit the data better than the 2-parameter model, with relatively higher adj. R2. Experimental results demonstrate that the presented adsorption technique can be used for isotherm measurement of the co-adsorption of VOCs and water vapor from the air. [ABSTRACT FROM AUTHOR]

The utilization of fibrous prunus dulcis seed shell powder (UPDSSP) and the phosphate-modified derivative (P-MPDSS) for the abstraction of Pb2+ was tested. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray (EDX), and the physicochemical characterizations revealed desirable characteristics of the adsorbents for efficient Pb(II) uptake. The FTIR of UPDSSP and P-MPDSS showed several functionality groups on the adsorbents. SEM morphology revealed high porosity surface structure of both adsorbents, while BET measurements showed an increase in surface area from 5.84 m2/g to 11.32 m2/g after phosphate modification. The modified adsorbent showed higher Pb(II) uptake than UPDSSP at variations of temperature, time, pH, metal concentration, and material dosage. pH 5.0 was optimum for Pb(II) adsorption and equilibrium was reached at 90 min on UPDSSP and P-MPDSS. The Freundlich isotherm presented the best fit (R2 > 0.991) than the Langmuir and Dubinin-Raduskkevich models. The pseudo-second-order gave the best fit (R2 > 0.971) than the pseudo-first-order and intraparticle diffusion kinetic equations. Thermodynamics showed endothermic, spontaneous, and physical adsorption of Pb(II) ions onto the adsorbents. The adsorbents showed good potentials for regeneration and reuse. The results revealed UPDSSP and P-MPDSS as viable materials for the decontamination of Pb polluted water. [ABSTRACT FROM AUTHOR]

In this work, significant interest has been focused on removing pharmaceutical pollutants, i.e., oxytetracycline (OTC), which was studied through adsorption onto activated carbon (ACT) produced from households or agricultural wastes under various experimental conditions. The physicochemical properties of the produced carbon were investigated using multiple techniques. The characterization analysis highlighted an essential concentration of surface functional groups and a very developed porous structure. The adsorption process onto activated carbon occurswith a high yield at a large range of pH values varying between 4 and 8 at an optimumcontact time of 2 h. It was established that the pseudo-second-order kinetic model fitted well OTC adsorption onto ACT. Moreover, the adsorption isothermdata showed that the pollutant removal process followed the Langmuirmodel with high regression coefficients (R²) values and important adsorption efficiency of 80% for 100 mg.L-1 of OTC. The displayed results consequently, the use of ACT as an adsorbent could be considered an efficient, sustainable, and low-cost alternative for pharmaceuticals-loaded wastewater treatment. [ABSTRACT FROM AUTHOR]

Successful synthesis of ZnO-chitosan nanocomposites was conducted for the removal of methylene blue from an aqueous medium. Remarkable performance of the nanocomposites was demonstrated for the effective uptake of the dye, thereby achieving 83.77, 93.78 and 97.93 mg g−1 for the chitosan, 5 wt.% ZnO-Chitosan and 10 wt.% ZnO-Chitosan, respectively. The corresponding adsorption efficiency was 88.77, 93.78 and 97.95 for the chitosan, 5 wt.% ZnO-Chitosan and 10 wt.% ZnO-Chitosan, respectively. Upon regeneration, good reusability of the nanocomposites was manifested for the continuous removal of the dye up to six consecutive cycles. The adsorption process was kinetically described by a pseudo-first order model, while the isotherms were best fitted by the Langmuir model. [ABSTRACT FROM AUTHOR]

In this study, the performance of boron carbide (B4C) on the adsorptive removal of methylene blue from aqueous solutions was investigated. Adsorption studies were carried out using different adsorbent dosage, dye concentration, pH, and temperature parameters. The BET analysis results showed the B4C surface area is 317.6 m2/g and B4C has a mesoporous structure. From the adsorption studies, the maximum dye removal percentage was obtained as 97.3% at 55 °C. Besides, different isotherm models were used during adsorption and the order was determined as Langmuir > Flory – Huggins > D – R > Freundlich > Harkins – Jura. For the Langmuir isotherm, qm was calculated as 188.68 mg/g at 55 °C. D-R isotherm, enthalpy, and activation energy data showed that adsorption took place physically. The kinetic studies showed that the adsorption was compatible with the pseudo-second-order kinetic model. Besides, it was determined from the thermodynamic studies that adsorption occurs endothermically and spontaneously. [ABSTRACT FROM AUTHOR]

In the present study, cellulose acetate/graphene oxide (CA/GO) composite nanofibers were prepared via the electrospinning method to remove Cr(VI) ions from aqueous solution via adsorption process in a batch mode. The impact of adsorption parameters, including contact time, pH, Cr(VI) concentration, and temperature was investigated to obtain the optimum conditions for the uptake of maximum Cr(VI) ions from water within a short time. The kinetic data of Cr(VI) adsorption were well fitted by pseudo-first-order and pseudo-second-order kinetic models, whereas Redlich-Peterson, Langmuir and Freundlich, isotherm models were used to describe the equilibrium data of Cr(VI) adsorption by the CA/GO nanofibers. The effect of temperature on the adsorption capacity of Cr(VI) ions using the nanofibers indicated that the higher temperatures were favorable for higher adsorption of Cr(VI) ions using the nanofibers. The thermodynamic parameters results indicated the spontaneous and endothermic of Cr(VI) sorption nature using the CA/GO nanofibrous adsorbent. The maximum monolayer adsorption capacity of nanofibers toward Cr(VI) ions sorption was 422.3 mgg−1 which was comparable with other adsorbents. The reusability of composite nanofibers was carried out for five adsorption–desorption cycles. The obtained results exhibited the high capability of CA/GO nanofibrous adsorbents for Cr(VI) ions sorption from actual wastewater. [ABSTRACT FROM AUTHOR]

Biomass is one of the most important carbon raw due to high availability and low cost. In this study mesoporous biomass carbon adsorbent derived from Luffa chemically modified with task-specific amidoxime group (Luffa-AO for short) was prepared. Luffa-AO was verified using SEM, TEM, FT-IR, N2 adsorption–desorption isotherm and X-ray photoelectron spectroscopy (XPS). The effects of operational parameters such as pH, mixing time, initial uranium concentration, temperature and recycle time on the adsorption of U(VI) with Luffa-AO were studied. The results showed that the saturation adsorption amount qmax reached 247.58 mg g−1, a competitive adsorption ability compared with the values reported in the previous references. Kinetics, isotherm and thermodynamics were investigated. The variation in binding energy elucidated with XPS indicated nitrogen and oxygen atoms involved in the process of complexing uranium. The study expanded the application fields of Luffa biomass and enriched the list of uranium adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel MOF adsorbent was synthesized by post-synthesis modification NH 2 -UiO-66. • The maximum adsorption capacity of Au(III) is 683.45 mg/g at 298 K. • The adsorbent has excellent selectivity and reusability. • The adsorption mechanism is electrostatic attraction, reduction and chelation. Efficient removal of gold ions from wastewater has become a hot research topic. A new metal–organic framework material (PAR-UiO-66) was prepared by post-modification of UiO-66-NH 2. A series of characterizations proved the successful preparation of PAR-UiO-66. The batch adsorption experiment was carried out. Under the room temperature (298 K) of and pH 4.0, the optimal adsorption capacity of PAR-UiO-66 for gold ions was 683.45 mg/g, which was an increase of 426.8 mg/g compared with that of UiO-66-NH 2. The adsorption of gold ions on PAR-UiO-66 accords with pseudo-second-order kinetics and Langmuir isotherm modles. The adsorption process was endothermic and spontaneous. PAR-UiO-66 has good selectivity and still has 92.5% adsorption efficiency after five repeated adsorptions. The adsorption mechanism is electrostatic attraction, reduction and chelation. [ABSTRACT FROM AUTHOR]

Introduction: Talquite consists of alternating three-layer bundles with weak Van der Waals bonds between them. The octahedral layer is located between two tetrahedral layers. It is used as an adsorbent for heavy metals in aqueous solution. Objective: To determine kinetic model, effective diffusivity and isotherms corresponding to the adsorption in the heterogeneous mass system of Cd (II) and Talquita ion in aqueous solution at temperatures of 298 and 333 K. Materials and Methods: A physical and chemical characterization of the adsorbent is performed. The kinetic, diffusive and equilibrium study of ion adsorption is carried out at 298 and 333 K. The adsorption processes are carried out with 150 rpm stirring on an AGU-10 Bunsen mechanical stirrer. Pseudo-first order, pseudo-second order, Elovich, liquid film diffusion, intraparticle diffusion, Bangham model, and effective diffusion models are instrumented. For isothermal balance studies, the Langmuir, Freundlich, Dubinin-Radushkevich, BET, Redlich, Toth and Flory-Huggins isotherms are implemented. Concentrations are determined by Atomic Absorption Spectroscopy. Results and Discussion: The pseudo-first order kinetic model has better adjust to the adsorption kinetics at two studied temperatures. The isothermal models of BET at 298 K and Flory-Huggins at 333 K have the better adjust to the adsorption of Cd (II) ions in aqueous solution. Conclusions: Talquite has moderate adsorption capacities for Cd (II) ions in aqueous solution. [ABSTRACT FROM AUTHOR]

Turkey tail (Trametes versicolor), cheap fungal biomass (TTFB), was used for the adsorption of CR from aqueous medium. Batch studies conducted to study the effect of pH (2.0–10.0), agitation speed (50–400 rpm), contact time (0–180 min), adsorbate concentration (300 and 500 mg/L), and temperature (303–333 K). TTFB characterized by FTIR, BET, SEM, and pHpzc. The maximum monolayer adsorption capacities of CR on TTFB were 318.1, 368.4, 394.8, and 415.7 mg/g at 303, 313, 323, and 333 K, respectively. The adsorption of CR was pH-dependent and maximum adsorption attained at pH 2.0 at all temperatures. Adsorption kinetic data evaluated by using the PFO and PSO non-linear equations. The kinetic data perfectly illustrated by the PSO model with R2 > 9935. Langmuir, Freundlich, D-R, and Temkin nonlinear isotherms applied for the experimental data, and it observed that the experimental data well fitted and found to be in good agreement with the Langmuir model (R2 > 0.9961) as compared with another three models. The values of ΔG° (–3.4159 to −6.1149 kJ/mol), ΔH° (23.2 kJ/mol), and ΔS° (0.088 kJ/mol K) revealed that the adsorption process was spontaneous, feasible and endothermic (ΔG° < 0, ΔS° > 0, and ΔH° > 0). The regeneration experiments indicated that the TTFB could successfully retain CR, even after five consecutive adsorption-desorption cycles. The binding of CR onto the TTFB surface was through electrostatic interactions. Therefore, TTFB considered as highly recyclable and efficient adsorbent material for CR as it can easily separate from the aqueous phase. [ABSTRACT FROM AUTHOR]

Biomass waste (Chinese traditional medicine residues) is one of the most promising sources of biochar. Here, the present study illustrated the activated biochar (BCA) was prepared using the herb residue (Astragalus membranaceus) via sodium carbonate (Na2CO3) activation for the removal of Cefradine (CF) in wastewater. The adsorbents were characterized by scanning electron microscopy, N2 adsorption-desorption analysis, Fourier transform infrared spectrum, X-ray diffraction, X-ray photoelectron spectroscopy and zeta potential analysis. The effects of initial pH value, BCA dosage, initial CF concentration and coexisting ion for CF removal were investigated. BCA showed much higher absorption capacity for CF (qm=64.76 mg/g) than the pristine biochar (BC). The uptake capacity of BCA and BC for CF was found to be pH-dependent. The analysis of the kinetic and isotherm studies indicated that strong chemical-sorption interactions occurred on the surface of BCA. The removal mechanisms of CF onto BCA would include π-π EDA interaction, hydrogen bonding, ion exchange and electrostatic adsorption. In addition, the fixed bed experiments demonstrated that BCA could be a promising and highly effective adsorbent to treat large volume of CF-contaminated wastewater. [ABSTRACT FROM AUTHOR]

A novel, green, and stable sorbent (Fe3O4@SiO2@l-Cysteine functionalized magnetic graphene oxide nanocomposites) was synthesized based on a chemical procedure to remove chromium(VI), lead(II), and cadmium(II) ions from wastewater samples. The l-Cysteine functionalized magnetic graphene oxide as a sorbent component was prepared based on the formation of the covalent bonding between graphene oxide and l-Cysteine. The percentages of the sorbent components, including Fe3O4 NPs, SiO2, and C-FGO were optimized using a D-optimal mixture design to enhance the sorbent stability, selectivity, and affinity toward the heavy metal ions. Besides, the critical factors on the heavy metal ion adsorption were investigated and optimized by a two-level full factorial central composite design. Electrostatic attraction is responsible for the adsorption of these ions on the sorbent, which is highly dependent on pH value. The kinetic study shows that the adsorption of these metal ions onto the sorbent follows the pseudo-second-order rate. The experimental results were investigated using the Freundlich and Langmuir models to determine the isotherm model, indicating the Freundlich isotherm model can well describe the adsorption procedure on the sorbent. The maximum adsorption capacity of 476.19, 526.32, and 588.23 mg g−1 was calculated for the Cr(VI), Pb(II), and Cd(II) ions with favorable adsorption and high affinity, respectively. The study of thermodynamic parameters indicates that the adsorption of these ions onto the sorbent is endothermic and chemical in nature. Moreover, the adsorption process is spontaneous in the temperature range of 278–328 K for removing these heavy metal ions. The obtained results confirm that the proposed sorbent is very suitable for the removal of the Cr(VI), Pb(II), and Cd(II) ions from electroplating wastewater samples with many advantages such as high efficiency, environment-friendly, low cost, and short absorption time. [ABSTRACT FROM AUTHOR]

In this present study, an adsorption process was investigated to removal of Congo Red (CR) dye from aqueous solutions by using multi-walled carbon nanotubes (MWCNTs) as an adsorbent. The physico-chemical properties of MWCNTs were characterized by TEM, SEM, Raman spectroscopy and BET surface area. The response surface methodology, which is including central composite design, was used to investigate the effects of four independent parameters (initial pH of solution (5.5–11.5), initial CR concentration (15–75 mg/L), MWCNTs amount (0.05–0.25 g/L) and contact time (20–60 min)). ANOVA evaluated with Design Expert 10.0 showed that a high value of regression coefficient (R2 = 0.988) a good agreement between experimental and model predicted response in addition to significance of the model. The optimum values of the independent variables giving the maximum removal efficiency (78.36%) of CR dye were obtained at the optimum adsorption conditions of initial solution pH: 5.5; initial CR concentration: 15 mg/L; MWCNTs dosage: 0.25 g/L and contact time: 59.62 min. The kinetic study illustrated that the experimental data are well defined with pseudo-second-order adsorption kinetic model. The maximum adsorption capacity (qmax) increased from 115.8 mg/g to 138.3 mg/g with the increase in temperature from 293 to 323 K. Thermodynamic parameters, ΔH (8.56 kJ/mol), ΔG (− 27.08 and − 30.73 kJ/mol) and ΔS (0.1215 kJ/mol K) were determined for the adsorption process. [ABSTRACT FROM AUTHOR]

The objective of this work is to test the effectiveness of hydrotalcite as an adsorbent for the retention of nitrate and nitrite ions and to study the influence of various reaction parameters such as pH, adsorbent dose, contact time and initial ion concentration. Hydrotalcites (HTx) of different Mg/Al ratios (x was Mg/Al ratio; 2, 3, 4) were synthesized by the co-precipitation method at constant pH and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). The results obtained indicate that hydrotalcite (HT3) allows good retention of nitrate and nitrite ions with no pH adjustment. Adsorption increases with decreasing mass of the adsorbent and increases with increasing initial concentration of nitrate and nitrite ions. When the Mg/Al ratio changes from 2 to 4; the electrical charge density between layers weakens; the inter-layer spacing increases and the material shows greater adsorption capacity. The equilibrium isotherm showed that the Langmuir model provided a better fit to the experimental data than the Freundlich model for nitrates and nitrites. The adsorption capacity of HT3 for nitrates and nitrites was found to be 6.92 mg/g and 9.26 mg/g, respectively. The XRD analysis after adsorption showed that materials that had undergone nitrate and nitrite ions adsorption, maintain the hydrotalcite structure. [ABSTRACT FROM AUTHOR]

The present study recommends the electrocoagulation (EC) technique as a possible-green option to the conventional process for the efficient removal of ibuprofen (IBU) from drinking water for the first time, investigating a thorough analysis by optimizing operational parameters and kinetics/isotherms models. Under the optimum conditions 63% of IBU was removed. The double-stage electrocoagulation resulted in the removal efficiency of 73.8%. The dynamic and equilibrium data followed first-order and Freundlich. The treatment cost of IBU removal by electrocoagulation would be 1.8 US $/m3. It is possible to consider the EC technique as the promising IBU removal method. [ABSTRACT FROM AUTHOR]

An adsorption N-Blue dye ions from aqueous solution on MWPMBC (Micro Wave assisted Pterocarpus Marsupium Bark Carbon) has been investigated. Analytical techniques have been employed to find characteristics of adsorbent materials. The adsorption of N- Blue dye ions was conducted in batch system. The effects of pH, adsorbent dosage and initial concentrations of N- Blue dye ions and contact time on adsorption efficiency were studied. Optimum adsorption was achieved at a pH 3 and equilibrium was established within 70 & 80 min of the process. The equilibrium adsorption data were analysed using four adsorption isotherm models: Langmuir, Freundlich, Temkin, Dubinin-Radushkevich isotherms. It is concluded that MWPMBC can be used as an effective adsorbent for removing N- Blue dye ions from aqueous solution. [ABSTRACT FROM AUTHOR]