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Abstract A unique set of 6 polar adsorptives of relatively large dipole moment and of increasing kinetic diameter were used to probe pore volumes available and their mechanism of adsorption on a well-characterised microporous carbon. Multiple adsorption isotherm measurements were made and repeatable results with relatively small standard deviations in amount adsorbed at low relative pressures were obtained. Inconsistencies were observed between calculated Gurvitsch volumes. Sources of these were analysed and identified as contributions from one or more of: (a) molecular sieve effects; (b) molecular packing effects, and; (c) 2D molecular structure formation due to hydrogen bonding. These inconsistencies were further studied by comparison with pore volumes derived via the Dubinin-Radushkevich (DR) equation. Qualitative analyses of the micropore filling processes were proposed, and substantiated by complementary DR analyses. Although most of the isotherms showed Type I character, recasting the relative pressure axis in logarithmic format highlighted clear differences as contributions from fluid-fluid and fluid-solid interactions during pore filling. Overall, the adsorptives were classified into three groups: (a) polar adsorptives with primarily specific interactions adsorbing as a condensation process over a relatively narrow relative pressure range in a medium and late pressure range (iso -PrOH, MeOH, 2-methyl, 2-butanol, H 2 O); (b) polar adsorptives with potential for non-specific interactions adsorbing as a condensation process over a relatively narrow pressure range in a medium pressure range (pyridine, iso -PrOH, 2-methyl, 2-butanol); and, (c) halogenated adsorptives adsorbing with an S-shaped uptake extending over a broad relative pressure (dichloromethane). Graphical abstract Image 1 Highlights • Six polar molecules with increasing kinetic diameter used as adsorptives. • High-resolution gas/vapour adsorption isotherms including uncertainty in the data. • Pore volumes evaluated via Gurvitsch and DR methods – inconsistencies analysed. • Low pressure isotherms show pore filling dependence on adsorptive size, shape, and polarity. • Pore filling classified into low, intermediate, and high relative pressure ranges. [ABSTRACT FROM AUTHOR]

Ternary layered double hydroxide (Co-Zn-Al LDH) intercalated with carbonate was synthesised via a simple co-precipitation method at pH ≥10. It was characterised using the Fourier transform infrared (FTIR) spectrometer, X-ray diffractometer (XRD), surface area and porosity analyser, Thermo-gravimetric/differential thermal analysis (TGA-DTA), and Scanning Electron Microscope (SEM). The Pb(II) adsorption properties, mechanism, and possible reuse of the LDH were also investigated by the batch technique. The characterisation results showed the presence of hydroxyl group as well as the intercalated carbonate anions within the well-defined LDH crystal structure. The TGA-DTA results confirmed the presence of these anionic groups which were liberated from the structure at ≈200 and 300°C, respectively. The LDH-specific surface area, pore diameter and width are 54.0 m2/g, 41.3 and 25.1 nm, respectively. Adsorption results showed that Pb(II) equilibrium could be achieved in 120 min, and adsorption increased with concentration and temperature. A Pb(II) adsorption capacity of 130.34 mg/g was reached for this LDH, and the adsorption process was spontaneous, endothermic and mainly electrostatic with most of the adsorption occurring within the pores. Desorption test suggested that approximately 90% of the adsorbed Pb(II) could be desorbed; hence, the Co-Zn-Al-CO3 LDH may be reused. [ABSTRACT FROM AUTHOR]

For removing the fluoride contamination as a serious threat to human health, the adsorption process has shown an appropriate performance among several treatment methods applied in the past. Therefore, the present study investigated the removal of fluoride using the low-cost adsorbent of clinoptilolite treated with acid from aqueous solution. The adsorbent was characterized by various techniques, that is, scanning electron microscopy, X-ray diffraction, XRF and BET. In this lab-scale study, the effect of contact time (1-240 min), pH (3-11), initial concentration (2-8 mg/L) and adsorption dose (1-20 g/L) on the fluoride removal efficiency was evaluated in a batch system. In addition, the isotherm and kinetic studies were applied to describe the data obtained from the adsorption process. The results showed that the highest fluoride removal efficiency (87%) was obtained in the condition of pH = 3 and equilibrium time of 2 h. In addition, it is observed that the pseudo-second-order kinetic model and both the Freundlich and Langmuir isotherm models appropriately describe the obtained data during fluoride adsorption onto the studied adsorbent. Based on the results of this study, acid-treated clinoptilolite indicated an affordable and promising potential for the removal of fluoride from aqueous solution. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the performance of eggshells modified with alum for fluoride removal from aquatic solution and determine the isotherm and kinetic isotherms. This study was conducted on the batch mode and some effective parameters on the adsorption rate such as contact time, pH, adsorbent dose and adsorbate concentration were evaluated. The characteristic of the modified adsorbent was determined via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of XRD showed the peaks for modified eggshell powder with alum, which illustrated the presence of the alumina on the adsorbent. SEM images disclosed that the particles in the raw eggshells are broken down into small pieces with sharp-sided. In addition, the batch experiments showed that the residual concentration of fluoride has decreased as time increases. Also, the removal efficiency has decreased as pH increases toward alkaline phase. It is observed that increase in the adsorbent dosage subsequently decreases the residual concentration level of fluoride. The results of the experimental data showed that Dubinin-Radushkevich isotherm and pseudo-second-order model (high R²) gave much better fit with data. According to the results, eggshell adsorbent modified with alum has been recommended for fluoride removal from aqueous solution. [ABSTRACT FROM AUTHOR]

Excessive phosphate effluent discharged in the surface water source rush to eutrophication. Consecutively this disturbs the water quality and aquatic ecosystem, due to the depletion of dissolved oxygen. Reduced oxygen level in water bodies affects aquatic life and decreases biodiversity. The present investigation emphasized the phosphate adsorption over nano‐alumina. Surface characteristics of the adsorbents, BET, FTIR, XRD, TEM, and SEM were analyzed to reveal the phosphate adsorption mechanisms. The adsorption isotherms, kinetics, pH effect were observed in batch experiments. The pHpzc value of nano‐alumina adsorbent was found as 8.1. The maximum phosphate adsorption was found to be 98.75% at contact time of 90 min and pH 6. Different models, e.g., Langmuir, Freundlich, Temkin, and Dubinin‐Radushkevich were used for isotherm study. The kinetic data were tested by pseudo‐first order and second order models. An attempt was made to regenerate the spent adsorbent for reuse in the adsorption process. Low cost and high capability of nano‐alumina make it feasible to utilize as cost‐effective phosphate remediation from wastewater. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S77–S85, 2019 [ABSTRACT FROM AUTHOR]

Highlights • Adsorption and desorption behaviors of SDZ and SMX in soil systems were revealed. • Adsorption was highly affected by soil texture, solution pH and ionic strength. • The mechanisms of physical and chemical sorption of SDZ and SMX were disclosed. Abstract This study focused on the adsorption/desorption behavior and mechanisms of sulfadiazine (SDZ) and sulfamethoxazole (SMX) in two Chinese agricultural soils. The sorption on these two soil systems was investigated through a batch reactor at different initial concentrations (0.5–10 mg L−1), different pH values (4–9) and ionic strengths (0.01–0.5 M). The obtained isotherms were linear within experimental uncertainty. The reversibility of adsorption process was assessed through desorption experiments of SDZ and SMX loaded soil samples. The results demonstrated that sorption was mainly influenced by the physicochemical properties of soil and the adsorbable species. It means that the sorption ability is stronger at higher organic carbon, higher clay fraction, lower pH value and intermediate ionic strength. An apparent decrease in the sorption capacity of SDZ and SMX with increasing pH was primarily attributed to the electrostatic repulsion between anionic species and negatively charged soil particles. Under various ionic strengths, the sorption affinity of SDZ and SMX in two soils revealed that sorption first increased and then decreased with increasing ionic strength. The thermodynamic analyses suggested that the sorption of SDZ and SMX was a spontaneous process. The results from Fourier transform infrared spectroscopy (FTIR) verified that the sorption of these sulfonamides was dominated by hydrogen bonds, electrostatic interactions and π-π interactions. This study contributed substantially to understanding the adsorption/desorption behavior and mechanisms of SDZ and SMX in the environment. [ABSTRACT FROM AUTHOR]

A natural clinoptilolite zeolite was modified through high temperature and chemical process to use for adsorption Mn2+, Ni2+, Co2+ and Cs+ from simulated radioactive solution. A series of analyses techniques including SEM, XRD and FTIR were applied to characterize the modification samples. The adsorption and kinetics were finely described by Langmuir isotherms and the pseudo second-order model. The adsorption rate constants denoted the adsorption rate had the following priority: Cs+ > Mn2+ > Ni2+ > Co2+. The thermodynamic parameters denoted that the adsorption of Mn2+, Ni2+, and Co2+ onto the modification sample were endothermic processes, and that of Cs+ was an exothermic process. [ABSTRACT FROM AUTHOR]

The current study discusses application of the lanthanum ions (La3+) as an activating agent incorporated /immobilized into coconut shell–based granular activated carbon (GAC) for porosity development; subsequently, the carbon material is used for the adsorption of phenol from aqueous solutions. The new carbons were characterized using FTIR, XRD, CHNO, burn off, and carbon yield. The surface functional groups were determined by Boehm titration. The Brunauer–Emmett–Teller (BET) surface area of the carbons is 953 m2 g−1 (GACLa1073), 997 m2 g−1 (GAC383), and 973 m2 g−1 (GACO383). Langmuir, Freundlich, Dubinin–Radushkevich, and John–Sivanandan Achari (J‐SA) isotherm models on the equilibrium isotherm data were examined for the new carbon‐phenol system. It is found that the Langmuir isotherm fits better with a monolayer adsorption capacity, highest for GACLa1073 (387.59 mg g−1) followed by GAC383 (303.03 mg g−1) and GACO383 (197.62 mg g−1). Kinetic studies reveal that the adsorption system follows the pseudo–second‐order kinetic model. Isotherm analysis by the phase change method of John‐Sivanandan Achari (J‐SA) isotherm gives a better insight into adsorption phenomena, which is accompanied by regeneration studies of carbon with >75% for GACLa1073 after three cycles. [ABSTRACT FROM AUTHOR]

The value of the thermodynamic determination of the Rehbinder effect is studied analytically as a function of adsorbate volume concentration in a liquid solution flowing about a solid surface in the case in which its isotherm has an S-type shape on the undeformed surface. Using a previously developed theory of equilibrium adsorption on a solid surface, taking its deformation and the presence of an electrical charge on it into account, the conditions are derived for the change in type of dependence of the Rehbinder effect value on the adsorbate volume concentration, from domelike to monotonically increasing. [ABSTRACT FROM AUTHOR]

Highlights • Zeolite loaded with ternary (hydr)oxides was developed for phosphate removal. • Phosphate was effectively captured over a wide pH range of 4–10. • The equilibrium pH after phosphate adsorption was near neutrality. • The maximum adsorption capacity of the zeolite (MALZ) was 80.8 mg P/g at 25 °C. • Phosphate was mainly captured by ligand exchange and the formation of LaPO 4 · x H 2 O. Abstract A novel La-incorporated nanostructured ternary (hydr)oxides adsorbent (MALZ) was prepared and employed for enhanced phosphate removal in this study. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that MALZ presented an amorphous surface with Mg, Al and La homogeneously dispersed on the outer region of zeolite. Effective phosphate removal was obtained over a wide pH range of 4–10 and the equilibrium pH after phosphate adsorption was in near neutrality. A relatively fast adsorption of phosphate was observed in the kinetics experiment, and the maximum adsorption capacity of MALZ (12.5 wt% La) was determined at 80.8 mg P/g at pH 6.6 in the equilibrium adsorption isotherm study. The coexisting anions (e.g., Cl−, SO 4 2− and NO 3 −) had insignificant effects on phosphate adsorption. The adsorption–desorption experiment suggested that MALZ could be regenerated by 0.5 M NaOH solution and maintained 75.8% of its initial phosphate adsorption capacity at the fourth adsorption–desorption cycle. The combined results of zeta potential analysis, SEM, XRD and X-ray photoelectron spectroscopy demonstrated that electrostatic attraction, ligand exchange of surface hydroxyl groups by phosphate and the complexation of forming inner-sphere complex (LaPO 4 · x H 2 O) were the main adsorption mechanisms. Furthermore, La played a key role in the complexation of phosphate, while the introduction of Mg and Al further facilitated the dispersion of La and enhanced the surface charge of the adsorbent. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First work studying the adsorption of daptomycin by two the magnetic biochars. • Ultra-fine magnetic wood-based biochars were prepared and characterized. • Maximum capacity of 217.39 and 212.77 mg/g was reported for daptomycin, respectively. • The adsorption mechanism of daptomycin was explored. • Kinetics and isotherm studies were performed for DAP adsorption. Abstract The adsorption of a new antibiotic, daptomycin, on two magnetic ultra-fine wood-based biochars were investigated in detail using batch experiments. The adsorbent materials was prepared by ball milling method, which was characterized by laser particle size analyzer, elemental analyzer, ICP-OES, VSM, BET, TG-DTG, FTIR and SEM. Furthermore, the effects of most important variables in the adsorption process, including solution pH, contact time, initial concentration and temperatures were investigated. The results exhibited that the adsorption of daptomycin was highly pH-dependent, and the capacity decreased with increasing pH. The adsorption process follows pseudo-first order and pseudo-second order models, analysis indicated that their adsorption was dominantly by physisorption. Equilibrium data were fitted well with Freundlich isotherm model, implying a multilayer adsorption. Thermodynamic parameters demonstrated that the adsorption was spontaneous, endothermic and increased randomness process. Mechanism study suggested the boundary layer diffusion was the rate limiting step. [ABSTRACT FROM AUTHOR]

Abstract The importance of adsorptive purification of the gas phase in HVAC-systems has constantly increased over the last few years, because people spend a large part of the day indoors. During this time they can be exposed to a variety of harmful gaseous contaminants, e.g. volatile organic compounds (VOC), which negatively influence health. Adsorptive HVAC-filters can help to reduce the concentration levels of noxious gases. For the comparison of HVAC-filter media the standard ISO 10121-1 determines test procedures. In ISO 10121 toluene is suggested as representative test substance for VOC at concentrations of 9 or 90 ppm in conditioned air (23 °C, 50% RH). The test concentrations in the standard tests are clearly higher than VOC concentrations in real buildings in order to limit testing times and to avoid being dependent on highly sensitive measurement technology. In this study, a methodology was investigated that forecasts breakthrough curves of toluene at concentrations down to 0.09 ppm predicted from measurement data at normatively proposed higher concentrations. The results can be used to estimate the service life of adsorptive filter media. The prediction is based on the isotherm equations of Langmuir, Freundlich or Dubinin-Radushkevich and the Wheeler-Jonas equation. The methodology was validated using three commercially available activated carbon based filter media. Good agreement between prediction and experimental data was achieved for s-shaped and moderate agreement for convex breakthrough curves. For the prediction of the equilibrium, the Freundlich and Dubinin-Radushkevich equation have proven to be accurate. Highlights • Service time of HVAC filters against VOC can be estimated at low concentrations. • The estimation is based on data at higher concentrations and a prediction method. • Combination of isotherm models and Wheeler-Jonas equation was used for the method. • Accurate or moderate prediction have been achieved for toluene breakthrough curves. • Freundlich and Dubinin-Radushkevich isotherm models gave the best fit. [ABSTRACT FROM AUTHOR]

Background: Phosphate (PO43−) is the main etiological factor of eutrophication in surface waters. Metal organic frameworks (MOFs) are novel hybrid materials with amazing structural properties that make them a prominent material for adsorption. Methods: Zeolitic imidazolate framework 67 (ZIF-67), a water stable member of MOFs, with a truncated rhombic dodecahedron crystalline structure was synthesized in aqueous environment at room temperature and then characterized using XRD and SEM. PO43− adsorption from synthetic solutions using ZIF-67 in batch mode were evaluated and a polynomial model (R2: 0.99, R2adj: 0.98, LOF: 0.1433) developed using response surface methodology (RSM). Results: The highest PO43− removal (99.2%) after model optimization obtained when ZIF-67 dose, pH and mixing time adjusted to 6.82, 832.4 mg/L and 39.95 min, respectively. The optimum PO43− concentration in which highest PO43− removal and lowest adsorbent utilization occurs, observed at 30 mg/L. PO43− removal eclipsed significantly in the presence of carbonate. The equilibrium and kinetic models showed that PO43− adsorbed in monolayer (qmax: 92.43 mg/g) and the sorption process controlled in the sorption stage. Adsorption was also more favorable at higher PO43− concentration, according to the separation factor (KR) graph. Thermodynamic parameters (minus signs of ∆G°, ∆H° of 0.179 KJ/mol and ∆S° of 44.91 KJ/mol.K) demonstrate the spontaneous, endothermic and physisorption nature of the process. Conclusion: High adsorption capacity and adsorption rates, make ZIF-67 a promising adsorbent for PO43− removal from aqueous environment. [ABSTRACT FROM AUTHOR]

This study represents the application of nanozeolite NaX (NZX) synthesized by hydrothermal treatment without addition of any expensive structure directing agent for the highly effectual adsorption of biochanin A from aqueous solution. The characteristics and surface morphology of NZX were determined using FT-IR, SEM, TEM, BET, and XRD. The adsorption performance of NZX was analyzed at different conditions such as temperature, pH, contact time, adsorbent dose, and initial adsorbate concentration. The adsorption mechanism was well verified by pseudo-second-order kinetic and Redlich-Peterson isotherm models. The thermodynamic parameters revealed that the removal process was exothermic and spontaneous. [ABSTRACT FROM AUTHOR]

Modified xanthan gum (XG-AM-TTE) was employed as an adsorbent to study the adsorption behavior, thermodynamics and kinetics of crystal violet (CV) from an aqueous solution. Fourier transform infrared spectroscopy analysis indicates that the functional groups present in the adsorbent, such as carboxyl, ester and hydroxyl groups, are included on the external surface of the material, and these groups are potential active sites for interaction with CV. According to X-ray diffraction results, the structure of XG-AM-TTE after CV adsorption became more disordered, and the microstructure change is an indication of effective adsorption of CV to the surface, with CV becoming remarkably dispersed in the adsorbent according to the scanning electron microscopy observations. The adsorption kinetics and adsorption equilibrium were best described by the pseudo-second-order model and Freundlich isotherms, respectively. The thermodynamic parameters, as the Gibbs-free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), indicated that the adsorption is a spontaneous, endothermic and entropy increase process. The maximum adsorption capacity of XG-AM-TTE was 183±12 mg/g, suggesting that XG-AM-TTE is an efficient adsorbent. [ABSTRACT FROM AUTHOR]

This study reports the preparation of highly dispersed nanoscale zerovalent iron (nZVI) with core-shell structure decorated onto graphene nanosheets (Gr-NS) to form nZVI-Gr-NS composite. Meanwhile, its excellent performance for concentrated Zn(II) wastewater treatment is also studied. The adsorption of Zn(II) onto nZVI-Gr-NS is well simulated by the pseudo-second-order model, which indicates the adsorption is the rate-controlling step. Moreover, the adsorption isotherms of Zn(II) on the nZVI-Gr-NS can fit well with the Langmuir model. The negative thermodynamic parameters (△GƟ, △HƟ, △SƟ) calculated from the temperature-dependent isotherms indicate that the sorption reaction of Zn(II) is an exothermic and spontaneous process. The high saturation magnetization (37.4 emu g−1) of the nZVI-Gr-NS makes separation of nZVI-Gr-NS-bound Zn(II) easily and quickly from aqueous solution. Most importantly, nZVI-Gr-NS composites not only remove Zn(II) but also spontaneously remove As, Se, and Cu ions from real smelting wastewater samples. This study provides a good solution for heavy metal removal in real wastewater. [ABSTRACT FROM AUTHOR]

In the latest years, there is an increase of an interest for cleaning industrial polluted waters containing heavy metals, which threatens the human health and pollutes the environment as well. A high amount of toxic metals in industrial polluted waters are shed in the environment in several forms. The metallurgic processes are producing a high amount of solid and liquid waste that are dumped into the water and in this way creates significant harmful effects for the environment and human health. It is known that heavy metals such as manganese, iron, nickel, chrome, arsenic, cadmium, cobalt, uranium, copper, etc. are very toxic elements, therefore, by dumping them into waters they will pollute the environment as well as living beings directly through the food chain. The critical toxicity of heavy metals has caused several disasters in the environment in the human history, so there is a fear of a catastrophic pollution nowadays, therefore new methods for treatment are required which do not have side effects. Biosorption is a special method of extraction and elimination of heavy metals from polluted waters and the same is done with natural wastes which are relatively cheap and easily approachable (biomass), these are food waste and the phyto-pharmaceutical waste. Vegetative waste from extraction of Herba Hypericum can be used as a biomass in order to eliminate completely or to reduce extremely toxic metals from the polluted water, especially chrome, cobalt and nickel that are considered as highly toxic metals which are very difficult to extract compared with other methods. This kind of treatment of metallic polarities is of a great importance for developing countries, in economic aspects and the aspect of accomplishing strict criteria of green technology. [ABSTRACT FROM AUTHOR]

In this work, the use of a novel low-cost adsorbent derived from Ziziphus lotus (ZL) and industrial carbon (IC) has been successfully applied to the removal of methylene blue (MB) from aqueous solutions. The efficiency of this material was studied through Lagergren pseudo-first-order and pseudo-second-order kinetic models. The process for the novel activated carbon and the IC were best represented by the pseudo-second-order rate model. Langmuir and Freundlich isotherms were used to describe the sorption equilibrium data. The Langmuir model turned out to be the most adequate and maximum capacities were measured to be 833.33 and 142.85 mg.g-1 for ZL activated carbon and IC from Sigma Aldrich, respectively. The thermodynamic study revealed that the sorption process is spontaneous and endothermic for the two adsorbents. To explain the effectiveness of MB removal, ZL activated carbon was characterized by scanning electron microscopy, Brunauer-Emmett-Teller surface area, X-ray diffraction and Fourier transform infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract In this work, we develop two-dimensional models based on the non-local density functional theory (2D-NLDFT) for the analysis of pore size distribution (PSD) of oxide materials with cylindrical pores with rough and heterogeneous walls. The existing standard NLDFT models for porous oxides assume the smooth energetically uniform surface of the pore walls. Due to this assumption, the calculated theoretical isotherms show typical layering transitions, which are not consistent with the experimental adsorption isotherms measured on real oxide materials. As a result, the fits of standard NLDFT models to N 2 or Ar adsorption isotherms show deviations from the experimental points in association with artifacts observed on the calculated PSD plots. The 2D-NLDFT framework allows us to improve the standard model by introducing the corrugation and energetic heterogeneity to the surface of cylindrical pores. The surface roughness and energetic heterogeneity are known characteristics of the oxide surfaces. With these assumptions we develop a comprehensive approach in which both branches of the adsorption isotherm may be used for the PSD analysis of mesoporous oxide materials. We validate this approach by using Ar data measured at 87 K on the reference set of MCM-41 silica samples (Kruk and Jaroniec, 2000). The generated kernels are smooth, do not show layering transitions and fit accurately the reference data. [ABSTRACT FROM AUTHOR]

Isotherms are of paramount importance for the interpretation of adsorption and ion exchange mechanisms and the design of separation and catalytic processes. Although the literature on sorption isotherms is rich, most of experiments and models employed are limited to systems that obey simple equilibrium isotherms, such as linear, favorable (convex-upward) or unfavorable (concave-upward). This paper deals with the rather overlooked S-shaped isotherms and their dimensionless forms, which are of great importance for the modeling of separation processes and interpretation of equilibrium data. A review on the physical significance and applications of S-shaped isotherms in adsorption and ion exchange process is also presented. [ABSTRACT FROM AUTHOR]

The CO 2 adsorption and CO 2 adsorption kinetics were evaluated by thermogravimetry on two Prussian blue analogues, K 2 x /3 Cu II [Fe II x Fe III 1- x (CN) 6 ] 2/3, with nominally K-free x  = 0.0 and K-rich x  = 1.0. Differential isosteric heats of adsorption were determined from adsorption isotherms using the Clausius-Clapeyron equation and integral values by differential scanning calorimetry. The average differential heats of CO 2 adsorption are 28 kJ/mol for x  = 0.0 and 33 kJ/mol for x  = 1.0. Both compositions show small maxima in differential heat at ∼1 mmol/g. The integral adsorption heats were determined to be 26 kJ/mol for both x  = 0.0 and x  = 1.0. The kinetic CO 2 adsorption/desorption curves can be modeled by a double exponential function describing two parallel processes with different rate constants. The activation energies for CO 2 adsorption on x  = 0.0 were 6 (1) kJ/mol for the faster component and 16 (1) kJ/mol for the slower one, while the corresponding values for x  = 1.0 were 9 (1) kJ/mol and 7 (1) kJ/mol, respectively. The maximum CO 2 uptake for both compositions was found to be ∼4.5 mmol/g, 19.8 wt %, at 1 bar and 273 K. The materials exhibited fast adsorption kinetics and stable cyclic performance at room temperature. The kinetics were slower for the samples with x  = 1.0 than for x  = 0.0 which may be attributed to interactions between CO 2 molecules and K + ions. [ABSTRACT FROM AUTHOR]

P-cresol formaldehyde resin was prepared and characterized by FTIR technique, then composited with polystyrene in order to produce electrospun nanofiber membrane by the electrospinning method. Zinc oxide nanoparticles was prepared and characterized by FTIR, XRD SEM and EDX techniques in order to modified first membrane. Both prepared nanofiber membranes characterized by SEM and EDX techniques and used as adsorbents to adsorb methylene blue dye from their aqueous solutions. The factors of adsorption were investigated, contact time, initial concentration, adsorbent dosage, ionic strength and temperature. The adsorption isotherms described by Langmuir and Freundlich models. So, thermodynamic functions ΔG, ΔH and ΔS of adsorption were estimated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Magnesium carbonate with cellulose pellets were optimized for phosphate adsorption. • Adsorption best described by pseudo -second-order kinetics and Langmuir isotherm. • Pellet with 15% cellulose showed best result for phosphate removal across studies. Abstract Phosphorus is an essential and limited nutrient that is supplied by a depleting resource, mineral phosphate rock. Eutrophication is occurring in many water bodies which provides an opportunity to recover this nutrient from the water. One method of recovery is through adsorption; this study focused on fabricating a porous and granular adsorptive material for the removal and recovery of phosphate. Magnesium carbonate was combined with cellulose in varying weight ratios (0, 5, 10, 15, 20%) to synthesize pellets, which were then calcined to increase internal surface area. Physiochemical properties such as surface area, surface morphology, elemental composition, and crystal structure of the materials were characterized using Brunauer, Emmett, and Teller (BET) surface area analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The pellet proved to be uniform in composition and an increase in BET surface area correlated with an increase in cellulose content until pellet stability was lost. Phosphate adsorption using the pellets was studied via batch kinetics and sorption isotherms. The pseudo -second-order kinetics model fits best suggesting that the adsorption occurring was chemisorption. The isotherm model that fit best was the Langmuir isotherm, which showed that the maximum equilibrium adsorption capacity increased with an increase in cellulose content between 10% and 20%. The average adsorption capacity achieved in the triplicate isotherm study was 96.4 mg g−1 for pellets synthesized with 15% cellulose. Overall, using cellulose and subsequent calcination created an additional internal surface area for adsorption of phosphate and suggested that granular materials can be modified for efficient removal and recovery of phosphate from water. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) have become material of special attention due to their high porosity and large surface area. Adsorptive removal of ciprofloxacin hydrochloride using MOFs from aqueous waste and real wastewater has been studied in this work. The MOF-5 synthesized showed higher adsorption capacity as compared to activated charcoal. The adsorption satisfies the pseudo-second-order kinetic model and adsorption isotherm is very well explained by the Freundlich and the Sips isotherm. The adsorption mechanism may be explained by the electrostatic interactions of the pharmaceutical compounds and the MOF-5 surface. Finally, it can be concluded that MOF-5 has shown a great potential for their application in wastewater treatment technology development. [ABSTRACT FROM AUTHOR]

The adsorption of serine anion on a smooth and platinized platinum electrode is investigated. The stationary and kinetic adsorption isotherms are plotted. For both smooth platinum electrodes and Pt(Pt) electrodes, the kinetics of the processes under investigation obeys the Roginsky-Zeldovich equation, and the stationary coverage is described by the Temkin isotherm. The main thermodynamic characteristics (adsorption equilibrium constant and change in the Gibbs free energy) of the process of adsorption of serine anion on both electrodes are found. [ABSTRACT FROM AUTHOR]

Abstract Caffeic acid(CA) was grafted on PVDF by UV pre-activation/thermal initiated grafting method with PVDF solution as substrates for the first time. The PVDF-g-CA was employed for fabrication of adsorptive membranes for cesium, and the static and dynamic adsorption, along with elution and membrane reusability, were studied. The results show that, under the same concentrations and grafting time, the average grafting degree of UV pre-activation/thermal initiated grafting method is much higher than that of the two-step UV grafting and the one-step UV grafting. The PVDF-g-CA membranes show high adsorption capacity for Cs+(0.23 mmol/g, 25 °C), and the selectivity factor of Cs+ vs. Li+, Na+ and K+ is 8.46, 3.68 and 3.23. This is the first report about the selective adsorption of Cs+ by CA-based materials. The adsorption isotherm can be well described by the Langmuir model. The membrane can be reused for 4 times without apparent performance deterioration, indicating great potential in adsorption of cesium from aqueous solutions. [ABSTRACT FROM AUTHOR]

Objective: The presence of dyes in the water is toxic and harmful to human body so, it must be removed from the water. In the present study, the removal of methyl violet (MV) from aqueous solutions using brown algae "Padina sanctae-crucis" was investigated. Materials and methods: The rate of adsorption was investigated under various parameters such as contact time (5–200), pH (2–11), dye concentration (10–60 mg/L), amount of adsorbent (0.25–5 g/L) and temperature (25–45°C). Results: The maximum adsorption was achieved in 10 mg/L, pH=8 and adsorbent dose 2 g/L and 80 min contact time for removal of MV from aqueous solutions. Kinetic studies showed that the pseudo second-order model describes adsorbent kinetic behavior better. Besides, experimental data have been modeled using Langmuir and Freundlich isotherms and the results showed that both models are proper to describe adsorption isotherm behavior. In addition, the equilibrium study shows that the adsorption was physical and favorable. Moreover, a thermodynamic study revealed that the adsorption process is exothermic and spontaneously in nature. Furthermore, Maximum adsorption capacity using adsorbent was 10.02 mg/g. Conclusions: It could be concluded that the P. sanctae-crucis biomass is a good adsorbent for removing MV dyes from aqueous solutions. [ABSTRACT FROM AUTHOR]

Adsorption and photocatalytic decomposition of anionic and cationic surfactants are presented. Two different types of photocatalysts were studied, commercial TiO2‐P25 (Evonik) with pHpzc = 5.65 and nitrogen‐modified TiO2/N pHpzc = 6.7 (point of zero charge). Two different types of surfactants were used: anionic surfactant NaDBS (sodium dodecylbenzene sulfonate) and cationic surfactant BtCl (benzethonium chloride). Obtained adsorption isotherms of NaDBS and BtCl comply with the conditions of monolayer Langmuir model isotherms. The maximal anionic surfactant adsorption took place at acidic pH and it was higher for TiO2/N (196 mg g−1) than for commercial TiO2‐P25 (140 mg g−1). There was the opposite situation in the case of cationic surfactants, higher adsorption took place at alkaline condition and it was higher for TiO2/N (100 mg g−1) than for commercial TiO2‐P25 (85 mg g−1). Photocatalytic degradation has been found to be more effective in neutral and high than in low pH solutions for both surfactants. It is mainly the difference between charges of the surface of photocatalysts and ionic parts of individual surfactants that determined the effectiveness for each of them. [ABSTRACT FROM AUTHOR]

The amorphous SiO2 (200-300 nm) was synthesized as an absorbent and thorium adsorption of SiO2 was investigated using experimental and RSM method. The SiO2 particles were made for the adsorption of thorium from aqueous solutions, and characterized by particle size measurement, XRD and SEM. The adsorption of thorium process was optimized with RSM method. The correlation between four variables was modeled and studied. Under optimum conditions, the adsorption capacity of SiO2 particles was found to be 134.4 mg/g, the correlation coefficient (R2) and the F value was obtained 0.96 and 1.98 × 10−6, respectively. In addition, the adsorption isotherms were examined. [ABSTRACT FROM AUTHOR]

Adsorption and photocatalytic decomposition of anionic and cationic surfactants are presented. Two different types of photocatalysts were studied, commercial TiO2‐P25 (Evonik) with pHpzc = 5.65 and nitrogen‐modified TiO2/N pHpzc = 6.7 (point of zero charge). Two different types of surfactants were used: anionic surfactant NaDBS (sodium dodecylbenzene sulfonate) and cationic surfactant BtCl (benzethonium chloride). Obtained adsorption isotherms of NaDBS and BtCl comply with the conditions of monolayer Langmuir model isotherms. The maximal anionic surfactant adsorption took place at acidic pH and it was higher for TiO2/N (196 mg g−1) than for commercial TiO2‐P25 (140 mg g−1). There was the opposite situation in the case of cationic surfactants, higher adsorption took place at alkaline condition and it was higher for TiO2/N (100 mg g−1) than for commercial TiO2‐P25 (85 mg g−1). Photocatalytic degradation has been found to be more effective in neutral and high than in low pH solutions for both surfactants. It is mainly the difference between charges of the surface of photocatalysts and ionic parts of individual surfactants that determined the effectiveness for each of them. [ABSTRACT FROM AUTHOR]

Abstract In this work, the pseudo-first-order (PFO), pseudo-second-order (PSO) and Vermeulen equations were modified by introducing an adjustable parameter i.e. the fractional surface coverage θ. The Langmuir kinetic equation was modified by the fractal-like approach and the separation factor R H was proposed to express essential characteristics of the fractal-like Langmuir isotherm. The kinetic and isotherm data obtained from nitrate adsorption on the PAN/AC composite were used to evaluate the validity of these models. Results indicated that the modified PSO equation could accurately predict the equilibrium time at different initial nitrate concentrations (R 2 > 0.998) and that the fractal-like Langmuir isotherm could better describe the equilibrium data at different temperatures (R 2 > 0.994). The magnitude of parameter b reflected the affinity of the adsorbent for the adsorbates. The innovation and significance of the present study was that the modified kinetic and isotherm models could predict the equilibrium time and describe the heterogeneous surfaces, respectively. Therefore, this work is expected to extend the application scope of the PFO, PSO and Vermeulen equations and Langmuir isotherm. Highlights • The equilibrium time can be predicted by modified PFO, PSO and Vermeulen equations. • The fractal-like Langmuir isotherm model is proposed. • The fractal-like Langmuir equation can describe nitrate adsorption well. • A new separation factor is defined. [ABSTRACT FROM AUTHOR]

High concentrations of fluoride in drinking water have adverse health effects for consumers. So, the aim of this study was to study the effectiveness of metal organic frameworks for fluoride adsorption. The adsorption process of fluoride using one of these novel adsorbents, known an Uio-66, was optimized using a central composite design. As-synthesized Uio-66 was characterized by XRD, FT-IR spectra, FESEM, EDX, and BET surface area. Furthermore, the variables of fluoride concentration, pH, adsorbent dose, and contact time were investigated. The findings showed that the maximum capacity of Uio-66 for fluoride adsorption was 31.09 mg g-1. The experimental data of Uio-66 fitted well with the pseudo-second order model and the Langmuir I model. The findings also showed that Uio-66 adsorbent has a high capacity for fluoride adsorption and can be functionalized to enhance the adsorption capacity. [ABSTRACT FROM AUTHOR]

Sorption is the most effective approach to the treatment of acid mine drainage (AMD) and wastewaters, but the removal of the adsorbents from water has always been a challenging problem which may be resolved by using magnetic separation. In this work, a magnetic bioadsorbent was prepared using low cost and high-performance sources and applied in Cr(VI) removal from a synthetic solution. Initially, magnetite nanoparticles were synthesized from iron boring scraps by chemical co-precipitation method. Results of dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) analyses showed that the synthesized nanoparticles were around 40 nm in size and had a significant magnetization. Then, the magnetite nanoparticles were attached to the dead and alkaline activated biomass of Aspergillus niger. Central composite design (CCD) was applied to determine the optimal condition of Cr(VI) adsorption on the produced magnetic nanobiocomposite. The maximum chromium removal (~ 92%) was achieved at pH 5.8, Cr concentration 23.4 mg/l, adsorbent dose 3.72 g/l, agitation rate 300 rpm, and duration 11 min. Kinetic studies showed that regardless of temperature, the process was controlled by mass transfer and intraparticle diffusion with an equilibrium constant of 0.74 mg/g min1/2 at 40 °C. Also, the adsorption isotherms followed the Temkin model, which indicated the physical adsorption of Cr(VI) on the produced sorbent. Therefore, the magnetic nanobiocomposite has a perfect ability to be used as the chromium adsorbent and can be collected by a low external magnetic field.Synthesis of the magnetic nanobiosorbent and its application in the removal of Cr(VI) from wastewaters. [ABSTRACT FROM AUTHOR]

Goethite is ubiquitous in the environment and plays key role in preserving dissolved organic matter (DOM) and deactivating potentially toxic elements (PTEs) by adsorbing DOM and PTEs. Various non-Fe metals are usually incorporated into natural goethite, substituting Fe in the goethite structure, which dramatically influence the physico-chemical properties and adsorption behavior of the goethite. In the present study, adsorption of DOM and Pb(II) on Mn-substituted goethite samples was investigated. The results displayed that the specific surface area (SSA) of mineral samples increased by 67.6% as the incorporation of Mn for Fe, from 25.71 m2 g−1 for pure goethite to 43.09 m2 g−1for Mn-goethite. Besides, the Mn substitution caused more hydroxyl groups and relatively fewer positive charges on mineral surface, and Mn in the Mn-goethite samples was predominantly present as Mn(III). The amount of DOM adsorbed to per unit mass of goethite was increased as Mn content increased, which was attributed to Mn incorporation increasing the SSA of mineral samples. However, the SSA-normalized absorption capacity for goethite to DOM was decreased by Mn because Mn substitution decreased the number of positive charges of mineral samples, which weakened the electrostatic attraction between DOM and the minerals. The amount of Pb(II) adsorbed to per unit mass of goethite was increased by Mn substitution, and the amount of Pb(II) adsorbed to per unit SSA of goethite increased as the amount of Mn substitution increased, indicating that the increased capacity for adsorbing Pb was not only caused by the SSA increasing but also by there were more surface hydroxyl groups on the Mn-goethite than pure goethite and Pb(II) preferentially adsorbed to Mn sites on the Mn-goethite. The present study results showed that Mn-goethite could be used to sequester DOM and remediate soil contaminated with PTEs because Mn-goethite has a high adsorption capacity and is environmentally benign. [Display omitted] • The enhancement of Mn-substitution for the DOM and Pb adsorption capacity of mineral. • PH plays an important role in the adsorption of DOM and Pb on mineral samples. • Ionic strength does not significantly affect Pb (II) adsorption to Mn-goethite. • Electrostatic interaction has important effect on the adsorption Mn-goethite to DOM. • Surface complexation is main mechanism involved in Pb (II) adsorption at low pH level. [ABSTRACT FROM AUTHOR]

In order to address the increasingly severe pollution issue caused by heavy metals, activated carbon-based absorbents have gained considerable attention. Herein, two novel adsorbents, amino-functionalized activated carbon (N-AC) and thiol-functionalized activated carbon (S-AC), were successfully synthesized by stepwise modification with tetraethylenepentamine (TEPA), cyanuric chloride (CC) and sodium sulfide. The pristine and synthesized materials were characterized by BET analysis, SEM, FTIR spectroscopy, elemental analysis and zeta-potential analyzer. Meanwhile, their adsorption properties for Cd 2+ and Pb 2+ and the effects of various variables on the adsorption processes were systematically investigated. The findings confirmed that amino-groups and thiol-groups endowed the AC with a strong affinity for metal ions and that the pH of solution affected the uptake efficiencies of the adsorbents by influencing their surface charges. Furthermore, six isotherm models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Sips and Redlich-Peterson) and four kinetic models (pseudo-first-order, pseudo-second-order, Intra-particle diffusion and Elovich) were applied to interpret the adsorption process at three different temperatures (288 K, 298 K and 308 K). The results indicated that temperature played an important role and that the rate-limiting step was chemosorption. A better fit for all adsorption systems was obtained with Langmuir model, with the maximum adsorption capacities at 298 K of 79.20 mg Cd 2+ /g and 142.03 mg Pb 2+ /g for N-AC, 130.05 mg Cd 2+ /g and 232.02 mg Pb 2+ /g for S-AC, respectively. Subsequently, the thermodynamic parameters revealed the nature of the adsorption was endothermic and spontaneous under the experimental condition. The possible adsorption procedures and the underlying mechanisms comprising physical and chemical interactions were proposed. Moreover, the as-synthesized adsorbents exhibited excellent regeneration performance after five adsorption/desorption cycles. The overall results demonstrated that both N-AC and S-AC could be the promising efficient candidates for removing Cd 2+ and Pb 2+ from contaminated water. [ABSTRACT FROM AUTHOR]

Apricot stone activated carbon (ASAC), was powdered, activated and to be used as effective adsorbent to remove the dyes from aqueous solutions through batch experiments under operational factors namely, pH, contact time, adsorbent dose, initial dyes concentration and temperature. The physico-chemical, morphological and structural properties of the adsorbents were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) instruments. Different kinetic models indicated that the adsorption is well described by the pseudo-second order model. The isotherms of methyl green (MG) adsorption on ASAC were obtained and correlated with various models. The smaller RMSE values for the Langmuir and Dubinin-Radushkevic models indicated the best fitting; the mono layer adsorption capacity of MG was found to be 148.478 mg g–1 at 21°C and 88.11 mg g–1 at 46°C at pH 10. The thermodynamic functions showed spontaneous and endothermic MG adsorption. In conclusion, the adsorbent prepared from apricot stone (ASAC) was found to very effective and suitable adsorbent for reactive dyes removal from aquatic environment, due to its simple and cheap preparation, easy availability and good adsorption capacity. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Pomelo (Citrus grandis) is the largest citrus fruit, the peel of which is a well‐known agricultural wastes. Disposal of pomelo peel after consumption is a serious environment problem. As a natural, versatile bio‐absorbent, pomelo peel has shown excellent adsorption capacity for several pollutants, attributed to its micro‐pores; however, there is no relevant report on its adsorption capacity for natural products or food ingredients. The ability of pomelo peel to adsorb epigallocatechin‐3‐gallate (EGCG) was examined in this study. The physicochemical characterizations of pomelo peel were determined by Fourier transform infrared spectroscopy, scanning electron microscopy and high‐performance liquid chromatography. The adsorption process of EGCG onto pomelo peel from aqueous solution was carried out at a range of concentrations (50–800 mg L−1) and temperatures (25, 40 and 55 °C). RESULTS: The main components of pomelo peel are composed of dietary fiber, which provide sufficient adsorption sites during the adsorption process. The adsorption of EGCG onto pomelo peel showed excellent fitness with a pseudo‐second‐order model. Both Langmuir and Freundlich models were able to describe the isothermal adsorption of EGCG onto pomelo peel. The results of thermodynamic analysis suggested that adsorption is spontaneous and endothermic in nature, and that the process is likely to be dominated by a physisorption mechanism. CONCLUSION: The results of this study indicate that pomelo peel has potential adsorption capacity for EGCG, which can be used as an effective, low‐cost carrier for delivery of natural products in functional food and dietary supplement applications. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

An experimental chamber (CIME2) has been specially designed to simulate wet atmospheric deposition on limestones used in Paris cultural heritage. This instrument is a complementary tool to CIME, a previously developed chamber dedicated to the simulation of dry atmospheric deposition on monuments and artifacts. The aim of this paper is to describe CIME2 and characterize the wet deposits produced inside it. Mist (fog), drizzle, and rainfall are differentiated in order to document their ability to saturate the limestones most currently used in Paris monuments: The Saint-Maximin’s limestone, the Liais of Saint-Maximin, and the Chauvigny’s limestone are tested. The comparison between normalized and environmental petrophysical data shows that in the wet deposition simulations, limestones are not systematically water-saturated. Moreover, the realistic experimental conditions chosen favor a more rapid evaporation of the stone water. The quantification of the non-saturation state is a first step that has to be taken into account to improve the geochemical models used to predict the alteration. [ABSTRACT FROM AUTHOR]

The present study deals with the preparation, characterization of a green natural product-based adsorbent, acid washed black cumin seeds (AWBC), and its application for adsorption of Methylene blue (MB) dye from aqueous solution. AWBC was prepared by washing black cumin (BC) seed powder with hydrochloric acid which was characterized using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy equipped with Energy-dispersive X-ray spectroscopy (SEM-EDAX) and transmission electron microscopy (TEM) techniques. Batch experiments were performed with varying adsorbent dose (1–5 g L −1 ), pH of the solutions (2−10), contact time (15–120 min), concentration (10–60 mgL −1 ), temperature (27, 35 and 45 °C) and agitation at 215 rpm. Langmuir, Freundlich, Temkin, and D-R isotherm models were used to determine the adsorption capacity, mechanism and other various parameters related to temperature effects. Results of the study indicated that the AWBC adsorption data fitted well with the Langmuir and Freundlich isotherms. The maximum Langmuir adsorption capacity of acid washed BC seeds for methylene blue was found to be 73.529 mg g −1 at 27 °C which decreased slightly with the rise of solution temperature. The pseudo-first-order, pseudo-second-order and Elovich kinetic models were used to demonstrate the reaction kinetics. Adsorption reaction followed the pseudo-second order kinetics. Overall, hydrochloric acid washed BC seeds offered low-cost adsorbent for MB removal from water. [ABSTRACT FROM AUTHOR]

Magnesium acetate, magnesium oxalate and magnesium oxide were employed to prepare waste polyester textiles-based activated carbons with well-developed mesoporous structures. TG analysis was conducted to explore the pyrolysis process and pore-forming mechanism. N 2 adsorption/desorption isotherms, EA, XRD, SEM and FTIR were performed to investigate the influences of different Mg-containing compounds on the physicochemical properties of activated carbons. The results indicated that the samples prepared by two organic magnesium salts exhibited higher specific surface area and porosity than that by magnesium oxide. Diversity in pore structure, morphology and surface groups of the carbons were owing to the differences in grain size of MgO and pyrolysis pathway of Mg-containing compounds. The adsorption isotherm of Cr(VI) for the activated carbons fitted well with Freundlich model, indicating that the adsorption process accorded with the theory of multilayer adsorption. The maximum adsorption capacity of Langmuir model of the sample prepared from magnesium acetate was the highest, and the main adsorption mechanisms were confirmed as electrostatic interaction and reduction reaction. [ABSTRACT FROM AUTHOR]

In this work, microwave-assisted hydrothermal process was applied to modify the municipal solid waste incineration (MSWI) fly ash and get zeolitic production. The condition of hydrothermal process was fixed at 200 °C and 30 min. The 1 mol/L Na 2 HPO 4 was selected as the additive, and the liquid to solid ratio was 3 ml/g. X-ray diffraction results revealed that analogous zeolite crystals formed by the MSWI fly ash during the hydrothermal process. The cation exchange capacity (CEC) was 0.498 meq/g of the modified fly ash, which increased about 22 times compared to the raw MSWI fly ash. To obtain the adsorption mechanism of the modified fly ash, the experiments of adsorption isotherm and kinetics were researched. The adsorption isotherms of heavy metal cations in mixed solution could be described by Langmuir isotherm equations, with a high correlation coefficient value. The experimental products were better fitted by the pseudo second-order kinetics rather than the pseudo first-order kinetics. Although the adsorption capacity of the modified fly ash needs to be promoted, it is a potential utilization for MSWI fly ash to be the original materials as adsorbents. [ABSTRACT FROM AUTHOR]

In this paper, three-dimensional carbon aerogel (CA) combined sodium titanate (CA/Na 2 Ti 3 O 7 ) was synthesized via a facile hydrothermal method, which was applied to remove Rb + and Cs + from aqueous solution. It is found the CA/Na 2 Ti 3 O 7 composites have larger adsorption capacity and faster adsorption equilibrium time than that of pure Na 2 Ti 3 O 7 , which is ascribed to the enhanced effect of CA on Na 2 Ti 3 O 7 . The adsorption isotherms can be fitted by the Langmuir model well. The adsorption mechanism at pH < 8.0 is attributed to the ion exchange process, while inner-sphere surface complexation is predominant at pH > 8.0. The adsorption kinetics follows the pseudo-second-order model and the major mechanism is identified by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The adsorption of Rb + and Cs + on CA/Na 2 Ti 3 O 7 can be explained by the ion exchange between Rb + /Cs + and Na + in the interlayer of Na 2 Ti 3 O 7 and the complexation of Rb + /Cs + with the –OH functional groups of CA/Na 2 Ti 3 O 7 . These results show potential application of CA/Na 2 Ti 3 O 7 in the elimination of radionuclides from wastewater. [ABSTRACT FROM AUTHOR]

Porous chitin sorbents (PChs) with different content of chitin, ranging from 0.9% to 3.5%, were prepared by gel method with CaBr 2 ·xH 2 O/CH 3 OH solution and characterized by FT-IR, XRD and SEM. The adsorption isotherms and kinetic analysis of methylene blue (MB) onto PChs were studied. Experimental results illustrated lower crystallinity and more pores of PChs containing 3.5% chitin displayed higher adsorption capacity, the removal of MB was 79.8%. The adsorption equilibrium isotherm curve of MB onto PChs adsorbents conformed to the Freundlich equation. The PFO, PSO and Weber-Morris models were applied to fit with the adsorption kinetics. The results demonstrated the adsorption of MB might be the mass transfer of heterogeneous system and involve multiple diffusion steps. The adsorption capacity of PChs with 3.5% chitin can maintain 65% removal ratio of MB after being used six adsorption-desorption cycles. It was supposed that PChs may be a promising, cheap, environmentally friendly and efficient adsorbent for some dye wastewater treatment in the near future. [ABSTRACT FROM AUTHOR]

In the present study, hexagonal mesoporous silica (HMS) was synthesized and modified by tannic acid as a natural poly-phenol and amine (TA-A-HMS) and was applied for the adsorption of bovine serum albumin (BSA) from aqueous media. To investigate the structure of HMS and TA-A-HMS, SEM, TEM, XRD, BET and FTIR analysis were applied. The effects of pH, adsorbent dosage, contact time and temperature on the BSA adsorption were studied. After modification, BET surface area of HMS was reduced from 885 m 2 /g to 51 m 2 /g which confirms the presence of tannin and amine groups that inhibit the adsorption of nitrogen molecules. According to the results of equilibrium data, it is shown that Langmuir isotherm with maximum adsorption capacity of 1000 mg/g is the predominant model and adsorption is mono-layer. Kinetic and thermodynamic studies also reveal that adsorption kinetic followed by pseudo-second order model and the adsorption process is exothermic. [ABSTRACT FROM AUTHOR]

Ammonium is a water pollutant that harms the environment, particularly fisheries. Rice straw is also an economic waste of rice, with millions of tons produced per year around the world. In this paper, physical and chemical procedures for the modification of rice straw were studied. The kinetic and isothermal adsorption trends were investigated, including the ammonium removal efficiency, the contact time of the adsorbent, the amount of adsorbent, and the initial concentration of NH4 þ . The effect of temperature and pH on the adsorption process was discussed. The removal efficiency of NH4 þ recorded 43, 53.7, and 69.5%, with maximum adsorption values of 2.9, 3.5, and 4.5 mg/g at temperatures of 25±, 35±, and 45±С, respectively, at pH 7.5. The biochar obtained from rice follows the pseudo-second-order equation for ammonium adsorption kinetics (R=188;0.98). The adsorption isotherm follows Freundlich's model (R=0.99) and Langmuir's model (R=0.98). [ABSTRACT FROM AUTHOR]

The detailed thermodynamic characteristics of the adsorption of water into iodide sodalite are studied. The correlation between the adsorption-energy characteristics and the crystal-chemical structure of the sodalide iodide was found, and the molecular mechanism of the adsorption of water into iodide sodalite was found throughout the entire filling region. [ABSTRACT FROM AUTHOR]

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The objective of this work was to study the efficiency of activated carbon prepared from agricultural waste (olive stones; OS) on diclofenac (DCF) adsorption in aqueous solutions. The prepared charcoals were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM)/Energy Dispersive X-Ray Analyser (EDX), and Brunauer-Emmett-Teller (BET) analysis techniques. The results show that DCF adsorption is favorable in acid medium and low temperature. The adsorption kinetics follows a pseudo-second-order kinetic model. The adsorption was found to be spontaneous (ΔG° < 0) for OS600°C, whereas the negative values of the enthalpy (ΔH°) suggest an exothermic adsorption for both adsorbents. [ABSTRACT FROM AUTHOR]

Polypyrrole is incorporated with activated carbon in large size dopant solution and investigated for 137Cs removal studies. Adsorption experiments showed optimum conditions within 240 min contact time, pH 6, 0.2 g adsorbent and ≤ 100 mg/l adsorbate dose, respectively, while the kinetic data followed pseudo-first-order model. Isotherm data were reproducible by the Langmuir isotherm yielding 23 mg/g maximum sorption capacity. Regeneration of adsorbent was attempted and indicated promising results within three cycles. The surface behavior has also been examined and revealed a well-ordered structure under gamma irradiation. This is a cheap adsorbent to consider and has also proven to possess higher sorption capacity than most highly-cost inorganic materials in use. [ABSTRACT FROM AUTHOR]