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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]

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]

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]

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, 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 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]

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]

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 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 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]

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]

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]

In this study, the pine cone was activated using NaOH solution and used in the adsorption of malachite green. The effects of initial pH, temperature, initial concentration, and contact time on the adsorption process were evaluated. Functional groups of active pine cone were characterized using Fourier Transform Infrared (FT-IR). Surface tissue images were obtained using Scanning Electron Microscopy (SEM). Isotherm studies were performed by analyzing data at the equilibrium. The compatibility of the experimental data with Langmuir, Freundlich, and Temkin isotherms was tested and results revealed that the data fits well to Langmuir type 2. Adsorption capacity is 111.1 mg/g and high adsorption value. Pseudo-first order and pseudo-second order kinetic model equations were used to analyze the kinetic data of the adsorption process. The pseudo-second order kinetic model was found to fit very well. The adsorption process was found to be endothermic, spontaneous and physical process according to thermodynamic parameters (ΔG0, ΔH0, ΔS0). [ABSTRACT FROM AUTHOR]

In this study, Fe3O4@ABDA nanocomposite was fabricated and used as an efficient material for elimination of MB dye from aquatic environment. The structural characterization, surface morphology, and thermal stability of Fe3O4@ABDA nanocomposite were achieved by using FTIR, TEM, TGA/DTG, XRD, and zeta potential. The impact of different parameters such as pH values, equilibrium time, temperature, and initial MB concentration on the elimination MB onto Fe3O4@ABDA nanocomposite was studied. The equilibrium time was reached in 180 min at pH 7 at 25°C. The maximum removal capacity for MB could reach 123.5 mg/g. The removal mechanism was mainly assigned to columbic and π – π combination among the molecules of MB and the Fe3O4@ABDA surface. [ABSTRACT FROM AUTHOR]

This study investigated the removal of phosphorus (PO4−3-P) from water samples by SnO2 and WO3 nanoparticles (NPs). The effects of adsorbent dosage, pH, contact time and temperature with an initial concentration of 50 mg L−1 of P were investigated. SEM-EDX, FTIR, XRD, and BET analyses were performed to characterize these nanoparticles. The results indicated that the maximum adsorption capacity of SnO2 and WO3 NPs was 21.5 and 19.0 mg g−1, respectively and occurred at pH = 3. Within 40 min of operation, about 47.2% and 45.2% of P ion were removed from the solutions by SnO2 and WO3 NPs, respectively. The kinetics of P adsorption from solutions was analyzed by fitting the experimental data to the pseudo-first and second-order kinetic models. The result showed that the pseudo-second-order kinetics model provided much better R2 values. In the multi-component solutions, in the presence of Cl−, NO3− and Cr2O72− ions, the adsorption rates decreased to (26.2% and 28.5%), (27.2% and 30.0%), and (48.0% and 33.0%) by SnO2 and WO3 NPs, respectively. Thermodynamic data (ΔG°< 0) fitting showed that the reactions of adsorption of P were spontaneous. In general, the nanoparticles of SnO2 had better efficiency in the removal of phosphorous from water. [ABSTRACT FROM AUTHOR]

The potential of activated charcoal supported on Manganese ferrite (AC-MnFe2O4) powder, for the removal of methylene blue (MB) dye from aqueous solution was investigated. Batch adsorption studies were conducted and various parameters such as initial dye concentration, pH, and temperature were studied to observe their effects in the dye adsorption process. The optimum conditions for the adsorption of MB onto AC-MnFe2O4 were found to be time and pH dependent. The amount of dye adsorbed increases from 1.67 to 27.49 mg/g as the initial concentration increases from 10 to 50 mg/L. Kinetics modeling showed that the pseudo-second-order model best described the process while Freundlich isotherm gives the best fit. The maximum adsorption isotherm of 77.44 mg/g was obtained for the adsorbent. The adsorption/desorption study showed that the adsorbent has over 99% for more than seven cycles. Increase in temperature from 30 to 50 °C raised the Qe, equilibrium adsorption capacity from 86.39 to 101.79 mg/g while the thermodynamic study shows that the process is favored with ΔG < 0, ΔH value shows that the process is endothermic. [ABSTRACT FROM AUTHOR]

Two novel adsorbents (AGD301 and ArgD301) were successfully prepared through ring-opening reaction. The adsorption performance and recognition selectivity of AGD301 and ArgD301 towards AuCl4− were studied by batch adsorption experiments. The results showed that adsorption time, pH, temperature and solution concentration had a significant influence on the adsorption performance. At 298 K and pH of 2, the equilibrium adsorption capacity of AGD301 and ArgD301 towards AuCl4− could reach 400.75 and 451.67 mg·g−1, respectively. In addition, AGD301 and ArgD301 possessed excellent selectivity and good reusability. [ABSTRACT FROM AUTHOR]

The novel organic capturing agent was synthesized through the amidation of 2-amino-5-guanidinopentanoic acid anchored on activated carbon with dimercaptosuccinic acid for effective elimination of toxic Pb(II) ions originated from contaminated water. The SH@AGPA@AC was examined by FT-IR, thermo-gravimetric analysis–DTG, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett Teller (BET), and X-ray photoelectron spectroscopy (XPS). The influence of experimental conditions like pH, adsorption time, initial Pb(II) concentration, and temperature on the performance of Pb(II) capturing was examined. The results revealed that the SH@AGPA@AC adsorbent was successfully fabricated. The kinetics data achieved a quite fit with the pseudo-second-order model. The SH@AGPA@AC obeyed the Langmuir model. The Pb(II) was fully desorbed with HCl (0.1 M) acid and then ready to reuse in the subsequent cycle after rinsing with water with the identical organic moieties of the SH@AGPA@AC. Thus, the SH@AGPA@AC was considered as an achievable and auspicious candidate for Pb(II) elimination from contaminated water with the highest adsorption capacities amount to 116.3 mg/g. [ABSTRACT FROM AUTHOR]

The electrospinning method was used to prepare novel PSM/EC microfiber characterized by SEM and BET analyses. Subsequently, the batch adsorption capacity of the PSM/EC microfiber was investigated for the removal of lead (ΙΙ) from aqueous solution. The effect of adsorbent concentration, initial solution pH, contact time and temperature on the adsorption process was studied. It was found that the double-exponential model was a better fit for the kinetic data. The equilibrium data were better predicted by the Liu Isotherm model with adsorption capacity of 44.6 (mg/g) rather Langmuir and Freundlich. The process is spontaneous and endothermic due to thermodynamic parameters. [ABSTRACT FROM AUTHOR]

The removal of Reactive Black 5 (RB5) using chemically modified banana peel powder (CMBPP) from aqueous solution was dealt with in the present investigation. Factors affecting the adsorption of RB5 (like pH solution, agitation speed, initial concentration of RB5, contact time and temperature) were investigated. FTIR, SEM-EDX, BET and Elemental analysis characterized the adsorbent material. Adsorption kinetic results evaluated by non-linear pseudo-second-order model was fitted well and showed good correlation with the experimental data than the pseudo-first-order model. The experimental equilibrium data evaluated by non-linear Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Temkin equations and the experimental data were well described by the Langmuir isotherm model. Langmuir monolayer sorption capacity of RB5 onto CMBPP was observed at pH 3.0 (211.8 mg/g). The values of thermodynamic parameters revealed that the sorption process was feasible, spontaneous, endothermic, and physisorption in nature, i.e. (ΔG° <0, ΔH° > 0, and ΔS° > 0). Desorption studies reveal that the maximum recovery of RB5 when 0.1 M NaOH solution used as a desorbent. The CMBPP also exhibited excellent regeneration efficiency for the five cycles of successive adsorption–desorption. The results exposed that CMBPP could use as a prospective adsorbent material for the removal of RB5 from aqueous media. [ABSTRACT FROM AUTHOR]

In this study, the main objective is the elimination of Basic Red 46 dye by coupling two processes, adsorption on activated clay followed by photocatalysis over ZnO as photocatalyst. The adsorption was investigated under different conditions of pH, adsorbent dose, dye concentrations, and temperature. The best adsorption yield occurs at neutral pH ~ 7 within 60 min with an uptake percentage of 97% for a concentration of 25 mg/L and a dose of 0.5 g/L. The results at equilibrium were successfully described by the Langmuir model with an adsorption capacity of 175 mg/g. To investigate the mechanism of dye adsorption characteristic, the adsorption constants were determined using pseudo first order, pseudo second-order and intraparticle diffusion model. It was found that the Basic Red 46 dye adsorption is well described by the pseudo second-order kinetic. The second part of this work was dedicated to the photodegradation onto ZnO under solar irradiation of the residual BR 46 concentration, remained after adsorption. For the remaining concentrations, the removal yields reach 100% under. [ABSTRACT FROM AUTHOR]

Fluoride concentration, if exceeds the standard levels in drinking water, can lead to adverse effects on human health. Adsorption is one of the widely considered appropriate technologies for water defluoridation. In this study, modified pumice with HCl and NaOH were used for the fluoride removal from aqueous solution, and two linear forms of the Langmuir and Freundlich isotherms model were applied to determine the best fit of equilibrium expressions. Several experimental parameters including pH (2–10), temperature (20–60°C), adsorbent dosage (2–10 g/L), fluoride concentration (5–20 mg/L), and contact time were studied. Results showed that removal efficiency improved with increase in contact time, initial fluoride concentration, and adsorbent dosage. The maximum removal efficiency (96%) was observed at pH 6, 10 g/L adsorbent dosage, 20°C solution temperature, 90-min reaction time, and 20 mg/L of fluoride concentration. The kinetic studies indicated that the adsorption equilibrium and kinetic data were in good agreement with the Langmuir Model (R2 = 0.95) with qmax = 65.5 mg/g and pseudo-second-order reaction (R2 = 0.99). According to the results, the modified pumice was found to be able to remove fluoride from aqueous environments with good removal efficiency and adsorption capacity. [ABSTRACT FROM AUTHOR]

This study was aimed at evaluating the isotherm of lead(II), manganese(II), and cadmium(II) adsorption in single and multimetal solutions using Nigerian bentonite. The natural and calcined clays were characterized for specific surface area, surface morphology, elemental composition, and cation exchange capacity (CEC). The adsorption data were analyzed and interpreted using isotherm models. The natural bentonite exhibits a specific surface area of 23.5 m2/g and a CEC value of 47.7 mEq/100 g and displays a higher adsorption capacity of all heavy metals in both single and multimetal solutions than the calcined bentonite. The removal of lead(II) by natural bentonite in single-component system is 0.0448 mmol/g. The order of selectivity is lead(II) > cadmium(II) > manganese(II). Result also shows that both clays demonstrate a preferable adsorption toward lead(II). Lead(II) adsorption is less affected by the presence of counter cations in multimetal solution. The adsorption of heavy metals onto Dijah-Monkin bentonite is site selective and site specific, and the adsorption data are well presented by the Langmuir model. The CEC could be the primary mechanism for the uptake of heavy metals, and the removal capacity was shown to depend on the ionic radius of metal ions. [ABSTRACT FROM AUTHOR]

Present study reports the adsorption of aromatic amine, 4-chloro-o-toluidine (4-COT), onto synthesized mesoporous Mobil Composition of Matter No. 41 (MCM-41) silica nanoparticles, in batch mode. Synthesized MCM-41 was characterized by XRD, BET, FTIR, SEM and TEM analysis. The effects of pH, MCM-41 dose, 4-COT concentration, contact time and temperature were studied, and interaction of 4-COT with the surface of MCM-41 and adsorption process controlling mechanism were investigated. BET analysis of MCM-41 showed 502.77 m2 g–1 of surface area. Kinetic experimental data were well represented by the pseudo-second order kinetic model. Freundlich and Temkin isotherm models well represented the adsorption equilibrium isotherm data. [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]

Adsorption of Ni(II) onto blue-green marine algae (BGMA) is investigated under batch condition. Under optimum experimental conditions, the initial Ni(II) metal ion concentration is varied from 25 to 250 ppm and the maximum adsorption capacity of BGMA is found to be 42.056 mg/g. The optimum pH, biomass loading, and an agitation rate on maximum removal of Cu(II) ion are found to be 6, 2 g, and 120 rpm, respectively. 24 h of contact time is allowed to achieve equilibrium condition. All the experiments are carried out at room temperature. The equilibrium experimental data infer that the isotherm is L-shaped. It is the indication of no strong competition between solvent and Ni(II) to occupy the active sites of BGMA. Also, it indicates that the BGMA has a limited sorption capacity for adsorption of Ni(II). The experimental data are tested with various isotherm models; subsequently, the mechanism of adsorption is identified and the characteristic parameters for process design are established. Fritz-Schlunder-V isotherm model is highly significant in establishing the mechanism of adsorption of Ni(II) under the conditions employed in this investigation followed by Freundlich. The qmax of 41.89 mg/g obtained by this model indicates its relevance more precisely with experimental data. [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]

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 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]

Magnetic biocomposite (MB) was fabricated by co-precipitation of palm seed-based biochar in the presence of Fe3O4particles. The MB sorption behaviour was investigated using nickel as the target pollutant. The MB characterisation revealed that its maintained micro-mesoporous character and high saturation magnetisation (65.8 Am2/kg) enable it to be separated from a solution using a magnet. The nickel removal efficiency of MB, 87% (28 mg/g), was achieved at pH 3; however, this was reduced to 45–75% (15–24 mg/g) in the presence of competing ions. The isotherms and kinetics studies revealed a monolayer interaction via a two-stepped sorption mechanism. [ABSTRACT FROM AUTHOR]

In the this research, removal of acid blue 62 from aqueous solution using mesoporous crystalline material-41 (MCM-41) loaded by polypyrrole (PPy) and polyaniline (PAni) was investigated. Synthesized composites were characterized by SEM, TEM, FTIR, XRD and BET analysis. Langmuir adsorption isotherm showed the best compatibility with the experimental data in comparison with other isotherm models (qm= 55.55 mg/L). Kinetic studies proved that the adsorption process is compatible with the pseudo-second-order kinetic model. Thermodynamic parameters such as Gibbs free energy changes (ΔGo), Enthalpy changes (ΔHo) and Entropy changes (ΔSo) were calculated. Negative value of ΔGoand positive value of ΔHoshow that adsorption of Acid blue 62 on PPy/MCM-41 nanocomposite is a spontaneous process also endothermic. Ulk4 is expressed in a cell cycle dependent manner and modulates cell cycle and Wnt signaling, thereby regulating embryonic corticogenesis, postnatal oligodendrogenesis and adult neurogenesis through the size of neural stem cell pool. [ABSTRACT FROM PUBLISHER]

Adsorption fixed bed models are of paramount importance in chemical and environmental engineering research. Although the related literature is rich, the vast majority of models employed are either phenomenological, based on chemical reaction kinetics, or limited to systems that obey simple equilibrium isotherms (favorable, unfavorable, linear, and rectangular) combined to linear driving force (LDF) for the solid-phase mass transfer kinetics and ideal plug flow. This paper complements the existing studies by presenting and analyzing a versatile nondimensional fixed bed model equipped with diffusion-based mass transfer kinetics and nonideal flow terms and adapted to deal with S-shaped (sigmoidal) isotherms. A discussion is conducted on the rather unusual fixed bed dynamics produced by systems that follow S-shaped isotherms, a subject which has been rarely and nonsystematically discussed in the related literature. Thus, this study aims at providing better understanding of the interactions of S-shaped isotherms, mass transfer, and axial dispersion on the shape of adsorption fixed bed breakthrough curves and comes to clarify and complement previously published results, especially on the unexplored effects of the isotherms’ inflection point on the breakthrough curves. [ABSTRACT FROM AUTHOR]

Functional cross-linked polymers (Poly(AA-co-DVB)) were synthesized using a one-step method. The properties of Poly(AA-co-DVB) were measured by SEM, FTIR, and TGA. The adsorption capacity of the Poly(AA-co-DVB) was investigated using methylene blue as an adsorbate. The effect of the mole compositions of acrylic acid and divinylbenzene monomers on the adsorption capacity was investigated in detail. The initial pH of solutions and contact time were also studied. The kinetics and isotherms of the adsorption process were also investigated. The result showed that the maximum equilibrium adsorption capacity was 1698.9 mg/g at room temperature and the adsorption kinetic was well fitted by a pseudo-second-order model and the adsorption isotherm agreed well with the Langmuir model. [ABSTRACT FROM PUBLISHER]

Adhesion of bacteria to clay minerals is of great importance in both natural soil environments and technological applications. In the present study, equilibrium experiments along with Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) were used to investigate the adhesion of Pseudomonas putida to the palygorskite and sepiolite clay minerals. The results showed that bacterial adhesion was rapid and reached equilibrium within 30 min. Equilibrium data showed that sepiolite has higher capacity and affinity than palygorskite for P. putida retention. Mixed FT-IR peak features of the clay minerals and P. putida were observed in the clay–bacteria complex spectra, indicating significant adhesion of P. putida to the minerals. However, some differences in the position of the individual bands were observed between infrared spectra obtained for pure bacteria or clay minerals and their corresponding clay–bacteria complexes, which are believed to be related to clay–bacteria interactions via different mechanisms. SEM/EDX analysis demonstrated fine fibrous clay particles adhered to the surface of individual P. putida cells. The results revealed rapid and close interactions of palygorskite and sepiolite with P. putida cells, which is important for better understanding the fate of bacteria in soil systems dominated by fibrous clay minerals and their practical applications in bioengineering and biotechnology. [ABSTRACT FROM AUTHOR]

Water discharged by several industries contains toxins, and it needs to be treated before disposal or reuse. In the present study, feasibility of adsorptive removal of Cobalt(II) ion in waste water, usingCocos nuciferaleaf powder, is exhaustively studied and reported. Effects of contributing parameters like Cobalt(II) ion concentration, initial solution pH, adsorbent dosage, and temperature are studied and the levels of parameters optimized, following a two level−four full-factorial experimental design with 6 center points and 24 non-center points. 15 g/L ofCocos nuciferaleaf powder could reduce the Cobalt(II) ion concentration by 84.82% in 70 min at a pH of 5.0 and a temperature of 303 K. Freundlich model is marginally superior to Langmuir, Halsey, and Temkin models in representing the equilibrium, at the optimized conditions. Pseudo-second-order kinetics model describes the adsorption process with a rate constant of 0.1238 g/mg-min. From thermodynamic analysis, it is noted that the adsorption is endothermic and facilitated. [ABSTRACT FROM PUBLISHER]

Based on the abundance of seed-watermelon pulp (SWP) in Xinjiang, China, SWP was employed to prepare low-cost adsorbent toward the removal of methylene blue (MB). The effects of contact time at different initial concentration were studied. The widely used adsorption isotherm models including Langmuir, Freundlich, and Temkin isotherms were employed to depict the adsorption process. The Langmuir isotherm was best fitted to the experimental data. Batch kinetic studies showed that an equilibrium time of 300 minutes was needed for the adsorption. The adsorption properties can be well described by pseudo-second-order kinetic model and the MB uptake was not controlled by intraparticle diffusion mechanism. [ABSTRACT FROM AUTHOR]

The textile industry is responsible for discarding wastewater contaminated with dyes. The timber industry generates waste in the form of sawdust. The aim of the present study was to evaluate the adsorptive potential of sawdust obtained from the Aspidosperma polyneuron tree for the removal of the textile dye from wastewater. Sawdust was subjected to different pre-treatments (acid, alkaline and polyethyleneimine) in order to increase its adsorption capacity. Based on the results from the isotherms, treatment with polyethyleneimine (PEI) led to the greatest adsorption capacity and fits the Freundlich model, indicating cooperative adsorption. Other treatments with sawdust best fit the Langmuir model, but the untreated sawdust presented better results than the treated sawdust. These results were only surpassed by sawdust treated with PEI. A. polyneuron revealed good potential for use as an adsorbent to remove dyes, which is a novel result, since to date there is no study on its use as a sorbent material. [ABSTRACT FROM AUTHOR]

The presence of water in coal presents a technological challenge for its industrial use in energetic processes. Water tends to negatively affect the coal quality and its net heating value (NHV), in addition to affecting its transportation costs. Therefore, this study aims to investigate the effects of glycerol and temperature on water adsorption onto systematically modified coals. A Colombian bituminous coal sample was used as support for being modified with glycerol. The virgin coal and modified coal were characterized by nitrogen adsorption at 77 K (SBET), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, elemental analysis (C–H–N elemental), and thermogravimetric analysis (TGA). The results showed that the water uptake decreased as the amount of glycerol on the coal surface increased. The optimum concentration of 8 wt% of glycerol impregnated on the coal minimized water adsorption. Over a range of water activity evaluations, this amount of glycerol (C8) reduced water adsorption by approximately 60% compared with nonimpregnated coal (C0). As expected, water uptake decreased with increasing temperature. These results are reflected in the NHV with an increase of 17% for the C8 sample compared with the other samples evaluated. The Talu and Meunier model was used to fit the experimental adsorption isotherms, and the mean square root error (MSRE%) was lower than 10%. The isosteric heat of sorption (IHS) for coal tends to decrease as the amount of adsorbed water increases. In addition, the value of IHS decreases as the concentration of glycerol increases due to the blocking of polar adsorption sites present on the coal surface, which are the main regions of low uptake of adsorbed water. Additionally, the Gibbs free energy was found to have negative values, which corroborates the spontaneous adsorption process. [ABSTRACT FROM PUBLISHER]

As(III) adsorption on NiFe2O4nanoparticles were systematically investigated by controlling parameters such as stirring rate, pH, initial arsenic concentration, contact duration, temperature, and adsorbent dose. It was observed that the amount of adsorbed arsenic concentration is strongly depended on pH and temperature. The temperature and pH give rise to significant changes in the amount of adsorbed arsenic. As compared with Langmuir and Freundlich isotherms models, the latter is found to be well suited. Pseudo-first order, pseudo-second order, and intraparticle diffusion models were applied to adsorption equilibrium data obtained from the analysis of arsenic with diverse amount of initial concentration. [ABSTRACT FROM AUTHOR]

In this paper, chitosan hydrogel beads were modified with gemini surfactant C12-4-C12 · 2Br and then used for the adsorption and removal of Congo red dye. The effects of pH, inorganic salt, temperature, shaking rate, and surfactant concentration were investigated in detail. The gemini surfactant concentration was the main factor, and the maximum adsorption amount was observed at 0.5% C12-4-C12 · 2Br. The Sips isotherm model fit well with the equilibrium experimental data, and the values of the heterogeneity factor (n) indicated heterogeneous adsorption. The adsorption kinetics was found to follow the pseudo-second-order rate model better than the pseudo-first-order rate model. [ABSTRACT FROM AUTHOR]

We studied the adsorption of Brilliant Yellow (BY) from aqueous solutions onto sepiolite and determined the adsorption equilibrium isotherms. We applied pseudo-first-order and pseudo-second-order kinetic models; the adsorption of BY onto sepiolite was best described by the pseudo-second-order kinetic model. The experimental data obtained at different temperatures were analyzed using various isotherm models; the Koble-Corrigan isotherm model provided the best fits for the BY adsorption data at all temperatures. The thermodynamic parameters of the BY adsorption onto sepiolite indicated that the adsorption process is spontaneous and exothermic in nature. [ABSTRACT FROM AUTHOR]

In this study, bentonite originating from Turkey (Eskişehir province) and activated carbon obtained from grapeseed were used as adsorbents for the removal of lead (Pb2+) and copper (Cu2+) ions from aqueous solutions. Experiments were performed in single- and binary-ion systems at constant temperature of 298 K and pH value of 5. In order to describe the adsorption mechanism Langmuir, Freundlich and Temkin isotherms were used. The total adsorption capacity values of adsorbents were compared. It was observed that the total adsorption capacity values were changed depending on the type of adsorbent used, type of metal ion and interaction between metal ions. [ABSTRACT FROM PUBLISHER]

Multi-walled carbon nanotubes (MWCNTs) and powder-activated carbon (PAC) were used as adsorbents for adsorption of nitrofurazone, a veterinary medicine, from aqueous solutions. The adsorbents were characterized using FTIR transform infrared spectroscopy, N2adsorption/desorption isotherms, and scanning electron microscopy. The effects of initial pH, contact time, and temperature on adsorption capacity of the adsorbents were investigated. For MWCNT and PAC, the result showed that when the pH value was ranged from 2.0 to 10.0, the dosage of adsorbent was 0.02 g, and adsorptive time is 4 hours, the removal efficiencies for nitrofurazone were 96.8% and 94.7%, and the corresponding maximum capacities at 283 K were close to 50.8 mgg−1and 59.9 mgg−1, respectively. For nitrofurazone, the pseudo-second-order kinetic model provided the best fit to the experimental data. The Boyd model indicated the mechanism for adsorption processes was mainly external mass transfer, while the effect of particle internal diffusion was relatively weak. Liu model could best fit to the experimental data of isothermal adsorption. The data of adsorption thermodynamics showed that the adsorption process was spontaneous. [ABSTRACT FROM PUBLISHER]

Methane storage was studied on the wet activated carbons by hydrate formation in the mesopore structures. Coconut shell was used as a raw material for preparation of the activated carbon samples. These highly mesoporous samples were prepared by the combination of both physical and chemical activation processes. After wetting the adsorbents with a constant water/carbon weight ratio (R) close to 1, the isotherms were obtained at 2°C up to the pressure of 80 bars. Wetted carbons exhibited stepwise isotherms at the critical pressure in the pressure range of 25–50 bars depending on the activated carbon samples. At this critical pressure, hydrate formation took place slowly. The amounts of methane uptake at 80 bars were obtained ranging from 14.9 to 24.8 mmol.g–1based on the dry adsorbent for different samples. By considering the density of activated carbon samples, the amounts of methane storage varied in the range of 185–237 V/V. [ABSTRACT FROM PUBLISHER]

Cr(VI) adsorption from aqueous solutions on Mg-Al hydrotalcite and Mg-Al hydrotalcite-gibbsite with Al/(Al+Mg) ratios (R) of 0.3 and 0.6 (MgAlHTR = 0.3and MgAlHTGR = 0.6) was investigated as a function of the pH and chromium concentration. The results showed that the maximum Cr(VI) adsorption by Mg-Al compounds do not depend on the value of R at pH 7. In addition, the chromate equilibrium sorption capacity for MgAlHTGR = 0.6is at least 4.8 times higher than that for MgAlHTR = 0.3at pH 5. The Cr(VI) maximum capacities of MgAlHTR = 0.3and MgAlHTGR = 0.6at pH 7 were similar, 6.5 and 6.8 mgCr(VI)/g, respectively. [ABSTRACT FROM PUBLISHER]

The adsorption of FD&C red 2 and FD&C yellow 5 onto chitosan films (CFs) was evaluated by equilibrium isotherms, thermodynamics, and kinetic studies. The effects of temperature (298–328 K), initial dye concentration (50–300 mg L−1), stirring rate (50–350 rpm), and contact time (0–120 min) were investigated at pH of 2.0 and 100 mg L−1of CFs. The dye concentration was determined by spectrophotometry. Freundlich and Langmuir models were used to represent the equilibrium data. The Langmuir model was the more adequate to represent the equilibrium data (R2 > 0.99 and average relative error <2.50%) and the maximum adsorption capacities were 494.13 and 480.00 mg g−1for FD&C red 2 and FD&C yellow 5, respectively, obtained at 298 K. TheRLvalues ranged from 0.044 to 0.145. The adsorption was exothermic, spontaneous, and favorable. For the FD&C red 2, 90% of saturation was attained at 120 min and the Elovich model was the more appropriate. For the FD&C yellow 5, 95% of saturation was attained at 20 min and the pseudo first-order model was the more adequate to fit the kinetic data. CFs were easily separated from the liquid phase after the adsorption process, providing benefits for industrial applications, and its application range can be extended for azo dyes. [ABSTRACT FROM PUBLISHER]

Analysis of differential pore-volume distribution (PVD) patterns of commercial clinoptilolite fractions [(<125 µ (Z8; fine), 125–250 µ (Z9; medium), and >250 µ (Z10; coarse)] has been conducted experimentally using an analyzer to measure the nitrogen (N2) adsorption isotherms. The differential PVDs of the clinoptilolite fractions were calculated from the hysteresis loop according to the adsorption and desorption curves of the Barret, Joyner, and Halenda (BJH) model. The adsorption and desorption cycles of BJH produced heterogeneous as well as dissimilar differential PVD patterns with assorted peaks. While the adsorption curve has prolonged up to 300 nm, the desorption cycle was confined up to 190-nm pore diameter only. In the adsorption cycle, all the clinoptilolite fractions displayed U-shaped curves and had a differential pore volume in the range of 3 × 10–3to 8 × 10–3 cm3/g A° in the micropore region with a sole peak at 1.75 nm for the fine fraction (Z8). In contrast, the curves were linear in the mesoporous region for all the fractions, with the fine fraction (Z8) having the greatest differential pore volume, whereas the other two fractions were almost parallel to each other. The desorption cycle has revealed an inverted V-shape curve with no definite patterns for the microporous region. Although the adsorption cycle could ascertain the micropore region, the desorption cycle was unable to do so. It was apparent from the differential PVD of the BJH model that fraction size has a major role in determining the textural properties of clinoptilolite fractions. [ABSTRACT FROM AUTHOR]

We have studied the adsorption of argon at 87 K in slit pores of finite length with a smooth graphitic potential, open at both ends or closed at one end. Simulations were carried out using conventional GCMC (grand canonical Monte Carlo) or kMC (kinetic Monte Carlo) in the canonical ensemble with extremely long Markov chain, of at least 2 × 108configurations; selected simulations with much longer Markov chains do not show any change in the results. When the pore width is in the micropore range (0.65 nm), type I isotherms are obtained for both pore models and for both simulation methods. However, wider pores (1, 2 and 3 nm in width) all exhibit hysteresis loops in the GCMC simulations, while in the canonical ensemble simulations, the isotherms pass through a sigmoid van der Waals type loop in the transition region. This loop locates the true equilibrium transition. For the pores with one closed end, this transition is close to, or coincides with, the adsorption branch of the GCMC hysteresis loop, but for the open-ended pores, it is more closely associated with the desorption branch. In a separate study of adsorption hysteresis in an infinitely long slit pore, using both simulation techniques, the van der Waals loop follows the adsorption branch of the GCMC isotherm to the transition, then reverts to a long vertical section that falls midway between the two hysteresis branches and finally moves to the desorption transition close to the evaporation pressure. An examination of molecular distributions inside the pores reveals two coexisting phases in the canonical simulations, whereas in the grand canonical simulations, the molecules are uniformly distributed along the length of the pores. [ABSTRACT FROM AUTHOR]