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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]

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 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]

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]

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]

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 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]

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]

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]

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]

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]

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]

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]

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]

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]

In this study, the adsorption behavior of Basic Red 46 (BR 46) in aqueous solutions by single-walled carbon nanotube (SWCNTs) and functionalized SWCNTs having covalent attachments of carboxylic group (SWCNT-COOH) surface as adsorbents were investigated. The adsorption equilibrium data were analyzed using various adsorption isotherms, and the results have shown that adsorption behavior of BR 46 could be described reasonably well by a generalized isotherm. Kinetic studies indicated adsorption of BR 46 by SWCNTs and SWCNT-COOH surfaces follows a pseudo-order model. The maximum adsorption capacities of BR46 by SWCNTs and SWCNT-COOH surfaces are reported at 298 K, 38.35 and 49.45 mg/g, respectively. The adsorption of BR 46 depends on the initial pH of the solution with maximum uptake occurring at about pH 9. Decrease in the absolute value of ΔG0 with increasing temperature indicates that higher temperatures hardship the adsorption. The negative value of ΔH0 reflects an exothermic adsorption and indicates that the adsorption is favored at low temperature. The negative entropy states that the adsorption of BR 46 by SWCNT-COOH and SWCNTs surfaces are orderly adsorbed by the surfaces. [ABSTRACT FROM AUTHOR]

This study evaluated the adsorption capacity of ethylenthiourea (ETU) and 1H-1,2,4-triazole (1,2,4-T) for two commercial activated carbons: charcoal-powdered activated carbon (CPAC) and bovine bone-powdered activated carbon (BPAC). The tests were conducted at a bench scale, with ETU and 1,2,4-T diluted in water, for isotherm and adsorption kinetic studies. The removal of the compounds was accompanied by a total organic carbon (TOC) analysis and ultraviolet (UV) reduction analysis. The coals were characterized by their surface area using nitrogen adsorption/desorption, by a scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) and by a zero charge point analysis (pHpcz). The results showed that adsorption kinetics followed a pseudo-second-order model for both coals, and the adsorption isotherms for CPAC and BPAC were adjusted to the Langmuir and Freundlich isotherms, respectively. The CPAC removed approximately 77% of the ETU and 76% of the 1,2,4-T. The BPAC was ineffective at removing the contaminants. [ABSTRACT FROM PUBLISHER]

This paper reports the monolayer characteristics of cationic octadecylamine (ODA) on both distilled water and aqueous Erythrosine B (EB) dye solution at the air-water interface. From the pressure-area isotherms at various pHs, EB anions in the subphase were found to interact with the insoluble monolayer of cationic octadecylamine (ODA). Adsorption kinetics shows that the amount of dye adsorbed depends on the concentration of the dye present in the subphase. It was observed that the adsorption process mainly occurred due to the electrostatic interaction between the cationic amino group of long chain amine and the anionic part of EB. The spectroscopic characteristics of the mixed LB films, solution, have been compared using UV-vis absorption and fluorescence spectroscopic data. These studies indicate the formation of aggregates in the thin films. Scanning electron microscopic study certainly confirms the presence of aggregates of EB dye in the (ODA-EB) mixed LB films. [ABSTRACT FROM PUBLISHER]

This study provides an electrocoagulation process for the removal of metals such as cobalt, copper, and chromium from water using magnesium as anode and galvanized iron as cathode. The various parameters like pH, current density, temperature, and inter electrode distance on the removal efficiency of metals were studied. The results showed that maximum removal efficiency was achieved for cobalt, copper, and chromium with magnesium as anode and galvanized iron as cathode at a current density of 0.025 A dm−2 at pH 7.0. First- and second-order rate equations were applied to study adsorption kinetics. The adsorption process follows second-order kinetics model with good correlation. The Langmuir and Freundlich adsorption isotherm models were studied using the experimental data. The Langmuir adsorption isotherm favors monolayer coverage of adsorbed molecules for the adsorption of cobalt, copper, and chromium. Temperature studies showed that adsorption was endothermic and spontaneous in nature. [ABSTRACT FROM PUBLISHER]

The technical feasibility of utilization of fly ash as a low-cost adsorbent for the removal of metals from water has been studied. For two types of fly ashes, the retention capacities of copper, lead, and zinc metal ions have been studied. Contact time, initial concentration, and pH have been varied and their effect on retention mechanism has been studied. The dominant mechanisms responsible for retention are found to be precipitation due to the presence of calcium hydroxide, and adsorption due to the presence of silica and alumina oxide surfaces in the fly ash. First-order kinetic plots have revealed that the rate constant increases with increase in the initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions considered under different conditions. X-ray diffraction studies revealed the formation of new peaks corresponding to respective metal ions precipitates under alkaline conditions. [ABSTRACT FROM PUBLISHER]

The removal of some of pollutants including catechol, 3-methylcatechol, 3-methoxycatechol, and 2,3-dihydroxybenzoic acid by adsorption onto activated carbon cloth (ACC) at 35.0 ± 0.1°C was investigated. The equilibrium experimental data were fitted to Langmuir, Freundlich, Temkin, Langmuir-Freundlich, and Redlich-Peterson isotherms. Also the kinetic experimental data were fitted to the pseudo-first-order and pseudo-second-order kinetic models. It was found that the pseudo-second-order model describes the kinetic of adsorption better than the other one. By comparing the obtained results with the previously reported data, it can be concluded that ACC is a high efficient adsorbent for removal of phenolic compounds from aqueous solutions. [ABSTRACT FROM AUTHOR]

The competency of a locally available granular activated carbon (GAC) in removing color from textile wastewater was studied in a fluidized bed. The characteristics of the fluidized bed with different GAC particles were obtained. A reactive dye was used to prepare the colored water of different dye concentrations. The effects of the GAC particle size, velocity and initial concentration of the colored water on dye removal were investigated. Equilibrium adsorption isotherm and breakthrough curves were generated to determine adsorption characteristics of activated carbon as well as mass transfer coefficients of the fluidized bed. The results of these experiments showed that an increase in liquid velocity and a decrease in particle size increased the color removal. The experiments were also carried out with industrial effluent and the de-colorization achieved was satisfactory. The mass transfer coefficient calculated for the fluidized bed was very low, which suggests that the GAC used in the local industries, although less expensive, may not be economically viable for de-colorization of industrial effluent. [ABSTRACT FROM PUBLISHER]

The adsorption of N-vinylpyrrolidone from aqueous polyvinylpyrrolidone solution using bamboo-based activated carbon was studied. The adsorption isotherms of N-vinylpyrrolidone on the carbon were determined and modeled with the Langmuir, Freundlich, and Temkin models. The Langmuir model provides the best fitting for the equilibrium data and the maximum monolayer adsorption capacity was estimated to be 833.3 mg/g. The kinetics of the adsorption process of N-vinyulpyrrolidone were modeled using various equations including pseudo first-order, pseudo second-order, and intra-particle diffusion equations. The adsorption process follows the pseudo second-order kinetic model, suggesting that the adsorption mechanism is chemisorption. The activation energy for the adsorption is 86.4 kJ/mol. Thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were determined. The positive value of enthalpy change indicates that the adsorption process is endothermic. [ABSTRACT FROM PUBLISHER]

Activated carbon has been applied for the adsorption of Alizarin Red S (ARS) from the waste water in a batch method to obtain high removal percentage. The influence of variables such as pH, temperature, ARS concentration, mass and size of adsorbent, and contact time on ARS removal percentage was investigated. Different kinetics, thermodynamics, and isotherm models were applied for fitting the experimental data. The adsorption process follows a pseudo second-order kinetic model with R 2 of 0.98 and Freundlich, Tempkin, and Dubinin-Radushkevich isotherm models with high determination coefficients (R 2) of 0.91, 0.98, and 0.98, respectively. High enthalpy (positive value), Gibbs free energy (negative value), and high entropy values shows the feasibility and the endothermic spontaneous nature of the removal process. [ABSTRACT FROM PUBLISHER]

The characteristics and kinetics of phosphate (P) adsorption on dewatered ferric-alum water treatment residuals (Fe-Al-WTRs) have been investigated. The existence of both aluminum (Al) and iron (Fe) in the residuals can result in significantly high P adsorption capacities. The P adsorption kinetics of Fe-Al-WTRs exhibited an initial rapid phase, followed by a slower phase. This could be described by three models, including a pseudo–first-order equation, a pseudo–second-order equation, and a double-constant rate equation. The latter was especially good for those runs with initial P concentrations of 500 and 1000 mg L−1. Both the Langmuir and Freundlich isotherms fit the experimental data well, particularly the Freundlich isotherm, which had a correlation coefficient of 0.9930. The maximum measured P adsorption capacity of Fe-Al-WTRs was 45.42 mg g−1, which is high when compared to those of most WTRs, as well as other reported adsorbents. The results also show that the P adsorption is a spontaneous endothermic process. Highest P adsorption capacities of Fe-Al-WTRs were measured at low pHs and a particle size range of 0.6 to 0.9 mm. [ABSTRACT FROM PUBLISHER]

The present study explores the ability of surfactant modified bamboo sawdust in removing zinc (II) ions from aqueous solutions. The modified bamboo sawdust is characterized by surface area analysis, Scanning Electron Microscope, and Fourier Transform Infrared and X-ray fluorescence analysis. Adsorption isotherm and kinetic models were used to study the adsorption characteristics of zinc (II) ions onto modified bamboo sawdust. The equilibrium adsorption isotherm data were fitted into the Langmuir and Freundlich adsorption isotherms. It was found that modified bamboo sawdust yielded maximum adsorption capacity of 111.12 mg/g at 50°C for zinc (II) ions. The kinetic data obtained at different initial concentrations were analyzed using first-order-reversible reaction, pseudo-first-order, and pseudo-second-order models. The results provide strong evidence to support the hypothesis of adsorption mechanism. [ABSTRACT FROM PUBLISHER]

Persimmon tannin was chemically modified to prepare a quaternary amine type of adsorption gel, named as quaternary amine modified persimmon tannin (QAPT) gel. The QAPT gel has been used to investigate the adsorption behaviors for Au(III), Pd(II), and Pt(IV) from HCl media. It was found that the gel exhibited good selectivity towards precious metals over a wide concentration range of HCl. However, it exhibited poor affinity towards base metals such as Cu(II), Fe(III), Ni(II), and Zn(II). The adsorption isotherms of the gel for precious metal ions were described by the Langmuir model. The maximum adsorption capacities for Au(III), Pd(II), and Pt(IV) were evaluated as 4.16, 0.84, and 0.52 mmol g−1, respectively. Although the anion exchange is the main mechanism for the adsorption of anionic species of Au(III), Pt(IV), and Pd(II), adsorption of Au(III) is followed by subsequent reduction, which results in the extraordinary high adsorption capacity for Au(III). Adsorption behavior of QATP gel for Au(III) was also compared to that of the persimmon tannin, the feed material. [ABSTRACT FROM PUBLISHER]

The studies of kinetics and thermodynamics of adsorption of Pb(II), Cd(II) and Cu(II) ions in aqueous solutions on single-walled carbon nanotube (SWCNTs) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces were by atomic absorption spectroscopy. The adsorption kinetics was well described by a pseudo-second-order rate model, while Langmuir, Freundlich, Redlich-Peterson (R-P) and Tempkin isotherms described the adsorption isotherms, and the adsorption thermodynamic parameters of equilibrium constant (K0), standard free energy (ΔG0), standard enthalpy (ΔH0) and standard entropy changes (ΔS0) were measured. The adsorption of Pb(II), Cd(II) and Cu(II) ions from aqueous solutions on SWCNTs and SWCNT-COOH. The values of ΔH0 and ΔG0 suggested that the adsorption of mentioned ions on SWCNT-COOH and SWCNT were endothermic and spontaneous. The adsorption of mentioned ions on SWCNT-COOH is more than SWCNTs surfaces. [ABSTRACT FROM AUTHOR]

The adsorption of a synthetic textile dye (Remazol Brilliant Black Reactive) on cocoa pod husk-based activated carbon was investigated in batch process. The adsorbent prepared was characterized by gas adsorption surface analysis (Brunauer Emmett Teller, BET), scanning electron microscopy, and Fourier transform infrared spectroscopy. The effects of initial dye concentration, contact time, solution temperature, and solution pH were evaluated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, the first being the best with maximum monolayer coverage of 111 mg g-1. Kinetic data were fitted into pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models; the pseudo second-order model provided the best correlation. Maximum adsorption was observed at pH 7. Standard free energy, standard enthalpy, and standard entropy were also calculated. The adsorption interaction was found to be endothermic and spontaneous. Both the mean free energy of adsorption and the activation energy show that the mechanism is by physisorption. [ABSTRACT FROM AUTHOR]

The present study explores the ability of a new adsorbent-conch shell powder (CSP) in removing Malachite Green from aqueous solutions. The effect of various process parameters, namely initial solution pH, temperature, initial dye concentration, adsorbent dose, and contact time was investigated. Adsorption equilibrium data were well described by the Langmuir isotherm with maximum adsorption capacity of 92.25 mg g-1 at 303 K. The kinetic data conformed to the pseudo-second-order kinetic model. A thermodynamic study showed the spontaneous nature and feasibility of the adsorption process. The results provide strong evidence to support the hypothesis of adsorption mechanism. [ABSTRACT FROM AUTHOR]

The adsorption behaviors of hydrophobic charge induction chromatography (HCIC) adsorbents with different functional ligands were investigated with immunoglobulin of egg yolk (IgY) as a model antibody. The adsorption isotherm and retention behavior in the column were studied, and the influences of the ligand structure and the pH on the adsorption were discussed. The results indicated that the pI of the target protein and pKa of HCIC ligand are the important parameter to determine the maximum adsorption pH of HCIC adsorbent, and high adsorption of IgY was found at pH 5 for all five adsorbents tested. Some differences could be found for different HCIC adsorbents, and the ligand structure influenced pH effect on the binding/elution of target protein. 2-mercapto-1-methyl-imidazole (MMI) ligand with a sulfone group showed a high adsorption capacity and strong pH-sensitivity, which would be more suitable for antibody purification. Moreover, the retention experiments indicated that IgY could be efficiently eluted from the adsorbents with 4-mercapto-ethyl-pyridine (MEP) or MMI as the ligand at acid conditions, while 2-mercapto-benzimidazole (MBI) ligand showed some difficulties on the elution. The retention study would help in defining not only the effective pH of elution for a given protein but also the elution efficiency of a given adsorbent. [ABSTRACT FROM AUTHOR]

Batch adsorption study was carried out to remove excess fluoride from water using pyrophyllite. Result showed that adsorption of fluoride was rapid in first 20 min and thereafter increased slowly to reach the equilibrium in about 2 hrs. About 85% removal efficiency was obtained within 2 hrs at an adsorbent dose of 4 g/L for initial fluoride concentration of 10 mg/L. Maximum fluoride adsorption takes place at pH 4.9. Thermodynamic parameters such as Gibb's free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were determined for the adsorption process. Negative ΔH° value signified that the adsorption process was exothermic in nature. From the kinetic study it was found that fluoride adsorption by pyrophyllite followed pseudo-second-order kinetics with an average rate constant of 0.92 g/mg · min. Intraparticle diffusion model was studied to determine the rate limiting step of the adsorption process. The system followed the Langmuir isotherm with maximum adsorption capacity of 2.2 mg/g of fluoride. [ABSTRACT FROM AUTHOR]

New poly[acrylamide/maleic acid/2-methacryloxy ethyl trimethylammonium chloride], poly[AAm/MA/METAC], super absorbent hydrogels (M1-M4) were prepared via microwave irradiated free radical solution polymerization using different compositions. According to swelling experiments, hydrogel M1 with higher METAC content gave relatively higher swelling percentage compared to other hydrogels. The hydrogel M1 was characterized by FT-IR, TGA, and SEM analysis. The influence of the uptake conditions such as pH, time, adsorbent dose and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. Furthermore, the Langmuir and Freundlich adsorption isotherms were applied and they showed a good fit to the experimental data. [ABSTRACT FROM AUTHOR]

Chitosan derivatives, such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS), are prepared and their coordination behavior toward Ca(II) was studied. The adsorption isotherms were correlated by dc/dt = -kcn at 20°C, 30°C, 40°C, 50°C, and 60°C. By linear correlation, the shapes of the isotherm curves were similar to the kinetic function of 1/c = kt and the rate equation was dc/dt = -kc2; the activation energies were 13.31 and 14.76 kJ mol-1 for KCTS and HKCTS, respectively. The overall rate of Ca(II) adsorption is likely to be controlled by the chemical process. The coordination mechanism of chitosan derivatives with Ca(II) was studied by infrared and X-ray photoelectron spectroscopy. The results indicated that -NH- of KCTS was coordinated. Nitrogen of amino, oxygens of hydroxamic acid, and carbonyl in HKCTS coordinated with Ca(II). [ABSTRACT FROM AUTHOR]

The structural organization of chitosan hydrogel beads (CSBs) formed by various anionic surfactants, sodium dodecyl sulfate (SDS), sodium decyl sulfate (DS), dodecyl benzenesulfonic acid sodium salt (SDBS), and dioctyl sulfosuccinate sodium salt (DSS), and their applications as adsorbents for environmental purifications were investigated using Congo red (CR) as a model dye. The adsorption capacities of CSB as a function of surfactant concentration revealed that CSBs formed by 5 g/L anionic surfactant were the most effective for CR adsorption. The structure of CSBs and their adsorption capacities for CR depend on the nature of anionic surfactants. The maximum adsorption capacities of CSBSDS, CSBDS, CSBSDBS, and CSBDSS obtained from the Langmuir isotherm model were 186.02, 209.28, 207.25, and 113.83 mg/g, respectively, indicating that CSBDS was the best adsorbent for CR. [ABSTRACT FROM AUTHOR]

The adsorptive performances of alkaline treated peat have been investigated for the removal of Pb(II), Co(II), and Ni(II) ions from aqueous solutions. The influence of initial metal ions concentration and equilibrium contact time was studied in a series of batch experiments, in comparison with natural peat. An increasing of adsorption capacity of alkaline treated peat was obtained for all studied heavy metals (23.07% - Pb(II), 23.53% - Co(II), and 26.19% - Ni(II)). The Langmuir isotherm model was the best model for the mathematical description of studied heavy metals adsorption on alkaline treated peat. A significant decrease of equilibrium contact time in case of alkaline treated peat was also found. The kinetics of Pb(II), Co(II), and Ni(II) uptake by alkaline treated peat followed the pseudo-second order mechanism. The FT-IR spectrometry analysis showed that carboxylic (-COO-) and hydroxyl (-OH) groups play an important role in the heavy metals binding process. The heavy metal could by easily eluted from the loaded adsorbent with 0.1 mol/L HCl and the adsorbent may be reused in several adsorption/desorption cycles. The alkaline treated peat has better adsorption characteristics for the removal of heavy metals from aqueous solutions, and the cost of this treatment is very low. [ABSTRACT FROM AUTHOR]

In this work, a new simple correlation has been derived for the prediction of the bulk porosity decline during nanofiltration of a salty (ionic) solution using the PVD membrane. This model has been developed on the basis of the adsorption of the cations available in the feed onto the membrane. Therefore, three adsorption isotherms were tested and fitted to the equilibrium adsorption data, and the Freundlich isotherm was subsequently realized as the best choice. The porosity model included two adjustable parameters which can be determined theoretically and experimentally. Adsorption isotherms were combined for the determination of the first parameter and a novel method called 'Flux test' was developed for the other parameter estimation. A reasonable agreement was observed between experimental- and model-predicted porosity. The model's ability of estimation indicates a little decrease at higher pressures due to approaching an unfavorable equilibrium adsorption condition and deviation from the isotherm's parameters from the actual equilibrium amounts to this situation. [ABSTRACT FROM AUTHOR]

In this study, removal of arsenazo(ΙΙΙ) using activated carbon (AC) and multiwalled carbon nanotubes and of methyl red using AC from waste water is reported. The influences of pH, temperature, concentration of the dye, amount of adsorbents, particle size of adsorbent, and contact time on the efficiency of removal from aqueous solution are investigated. Adsorption experiments indicate that the extent of adsorption is strongly dependent on the pH of the solution. Changes in free energy of adsorption ( [image omitted]), enthalpy ( [image omitted]), and entropy ( [image omitted]) are calculated to understand the nature of adsorption. The calculated values of [image omitted] indicate that the adsorption process is spontaneous. The estimated values of [image omitted] and [image omitted] are positive which indicates that the adsorption process is endothermic and that the dye molecules are organized on the adsorbent surface in a more random fashion than in solution. The dye adsorption process follows a pseudo-second-order model under involvement of an intra-particle diffusion mechanism. Standard adsorption isotherms are used to fit the experimental data. [ABSTRACT FROM AUTHOR]

The adsorption characteristics of Pb2+ on pre-boiled treated onion skins (PTOS) and formaldehyde-treated onion skins (FTOS) were evaluated. The effects of Pb2+ initial concentration, agitation rate, solution pH, and temperature on Pb2+ adsorption were investigated in batch systems. Pb2+ adsorption was found to increase with increase in initial concentration. The point of zero net charge (PZC) was 6.53. The optimum pH for the maximum removal of Pb2+ was 6.0. The adsorption equilibrium data was best represented by the Langmuir isotherm model for FTOS and the Freundlich isotherm model for PTOS. The maximum amounts of Pb2+ adsorbed (qm), as evaluated by the Langmuir isotherm, was 200 mgg-1 for FTOS. The efficiencies of PTOS and FTOS for Pb2+ removal were 84,8.0% and 93.5% at 0.15 g/200 mL-1 adsorbent dose, respectively. (C0 = 50 mg L-1). Study concluded that onion skins, a waste material, have good potential as an adsorbent to remove toxic metals like Pb2+ from water. Boehm titration analysis was conducted to determine the surface groups. It was found that the adsorption kinetics of Pb2+ obeyed pseudo-first-order kinetic model as based on Δq (%) values. FTIR and SEM images before and after adsorption was recorded to explore changes in adsorbent-surface morphology. Activation energy (Ea) was obtained as 25.596 kJ/mol. [ABSTRACT FROM AUTHOR]

Bentonite clay is tailored in three different ways to produce porous materials viz. PCH1, PCH2, and PILC, where PCH1 and PCH2 are two different clay heterostructures and PILC is a Zr-oxide pillared clay. Surface characterization materials shows that both of PCHs have a higher surface area than PILC, and have micro and mesoporosity, where PILC is basically a microporous. DRIFT and X-ray techniques were used to investigate the surface-groups and height of micropores in PCHs and PILC, respectively. Adsorption isotherms of ethane and ethylene were measured on these materials up to high pressure (1000 kPa) under different temperatures, and by processing the obtained data these materials were evaluated for their aptness for ethane ethylene separation. Isosteric heats of adsorption were observed higher for ethylene than ethane during initial surface coverage for each material-gas system. Interaction in each material-gas system with gradual increase in pressure was elucidated with the help of isosteric heat curves. Adsorption performances of these materials were compared with already studied materials (reported by other workers for ethane/ethane separation). Comparison was based on selectivity and working capacity, which are the two decisive parameters for screening suitability of any adsorbent material (for PSA application). [ABSTRACT FROM AUTHOR]

The adsorption isotherms indicated that the adsorption of boron (B) increased with its increasing concentration in the equilibrium solution. The Langmuir adsorption isotherm was curvilinear and it was significant when the curves were resolved into two linear parts. The maximum value of adsorption maxima (b1) was observed to be 7.968 mg B kg-1 in Garhi baghi soil and the bonding energy (k) constant was maximum at 0.509 L mg-1 in Jodhpur ramana soil. The Langmuir isotherm best explains the adsorption phenomenon at low concentrations of the adsorbent, which of course was different for different soils. There was significant correlation between b1 and clay (r = 0.905**), organic matter contents (r = 0.734*), and cation exchange capacity (CEC; r = 0.995**) of soils. A linear relationship was observed in all the soils at all concentration ranges between 0 and 100 mg B L-1, indicating that boron adsorption data conform to the Freundlich equation. Soils that have a higher affinity for boron adsorption, like Garhi baghi, tended to desorb less amount of boron, that is, 43.54%, whereas Ballowal saunkhari desorbed 48.00%, Jodhpur ramana 48.42%, and Naura soil 58.88% of the adsorbed boron. Boron desorption by these soils is positively and significantly correlated with the sand content (r = 0.714**) and negatively with clay content (r = -0.502*) and CEC (r = -0.623**). The maximum value of 37.59 mg kg-1 for desorption maxima (Dm) was observed in Garhi baghi soil and also a constant related to B mobility (Kd) was found to be maximum in Garhi baghi (0.222 L kg-1) soil Note: *P<0.05; **P<0.01. [ABSTRACT FROM AUTHOR]

Rapid industrial development in the old northeastern industrial region of China resulted in Hg pollution. A series of batch experiments were conducted to assess the adsorption/ desorption and transfer of Hg (II) within typical black soil in this region and typical red soil in south China as a comparison: both are typical soils in China. It was found that both soils had high affinity for Hg (II) and the absorbed amount was more than 95% of the added. Hg (II) adsorption isotherms were well fitted with the Langmuir and Freundlich equations. The affinity of Hg (II) for black soil was three times higher than that of red soil. Results demonstrated that soil organic matter had an important role in Hg (II) adsorption. Fifty-three and twenty-eight percent of the maximum sorption amount for Hg (II) was contributed by organic matter for black soil and red soil, respectively. Kinetic studies showed that Hg adsorption on both soils was characterized by a biphasic pattern, with a fast step followed by a slow step. Black soil completed 90% of total Hg (II) adsorption in 34 min and reached equilibrium in 321 min, compared to 91 min and 630 min on red soil, respectively. [ABSTRACT FROM AUTHOR]