Sorption Equation Research Articles

Application of genetic algorithms to determine heavy metal ions sorption dynamics on clinoptilolite bed

Application of genetic algorithms to determine heavy metal ions sorption dynamics on clinoptilolite bed In the last decade a growing interest was observed in low-cost adsorbents for heavy metal ions. Clinoptilolite is a mineral sorbent extracted in Poland that is used to remove heavy metal ions from diluted solutions. The experiments in this study were carried out in a laboratory column for multicomponent water solutions of heavy metal ions, i.e. Cu(II), Zn(II) and Ni(II). A mathematical model to calculate the metals' concentration of water solution at the column outlet and the concentration of adsorbed substances in the adsorbent was proposed. It enables determination of breakthrough curves for different process conditions and column dimensions. The model of process dynamics in the column took into account the specificity of sorption described by the Elovich equation (for chemical sorption and ion exchange). Identification of the column dynamics consisted in finding model coefficients β, KE and Deff and comparing the calculated values with experimental data. Searching for coefficients which identify the column operation can involve the use of optimisation methods to find the area of feasible solutions in order to obtain a global extremum. For that purpose our own procedure of genetic algorithm is applied in the study.

Dynamic separation of ultradilute CO2 with a nanoporous amine-based sorbent

An alternative amine-based sorbent (RFAS) was developed in this work. RFAS was assessed under various conditions. Studies show that the CO2 sorption capacities of RFAS increase considerably with N loading, slowly with increasing temperature (apparently contrary to the prediction with the isothermal equation of exothermic sorption), and gradually with the decease of gas flow rate in the tested range. In addition, CO2 sorption capacity increases and then decreases as the H2O:CO2 mole ratio increases, and the stoichiometric ratio 1:1 is the turning point. The CO2 sorption capacities achieved by RFAS with 8.07mmolN/g for air with 400ppm CO2 and the CO2–N2 gas mixtures containing 1 vol% CO2 are 1.78mmol CO2/g and 1.92mmol CO2/g, respectively, higher than those reported in the most recent literature. A kinetic model corresponding to three proposed pathways is derived and expected to quantitatively predict the CO2 sorption characteristics given that the involved parameters can be established in the future. The half-CO2-adsorption and desorption times of RFAS along with temperatures are used to evaluate the dynamics of the sorbent. The adsorbed CO2 can be completely desorbed at only 80°C within as short as 30min. Low temperature desorption not only leads to the decrease in energy consumption but also benefits the structure stability of RFAS. The CO2 sorption capacities of RFAS within 10 sorption–desorption cycles are repeatable. All the results confirm that RFAS is a highly adsorptive, reversibly dynamic, and regenerable sorbent for capture of ultradilute CO2 from gas mixtures.

Storage Stability of Pupuru Flour (A Cassava Product) at Room Temperature

Aims: The knowledge of water sorption Isotherm gives information about water activity of foods; to investigate chemical reactions during drying and storage. This study therefore, was to determine the sorption properties of pupuru flour during storage at ambient temperature. Study Design: Research study. Results: The coefficients of determination varied from 0.881- 0.993. Both Henderson and Oswin models gave the most suitable models for describing the sorption data. The appropriate constants in the sorption equation were determined by regression analysis at temperature of 27°C. A comparison of the EMC curves showed that the toasted pupuru sample had lower equilibrium moisture contents than the smoked and oven dried samples at lower aw but higher EMC at higher aw. Conclusion: It can also be concluded that the models are quite useful in assessing the storage stability of pupuru flour. The toasted pupuru flour has a higher sorption capacity and longer storage stability at higher aw of the tropics than the other two samples at atmospheric temperature of 29°C. Research Article

Phosphate Desorption Characteristics of Some Representative Soils of Bangladesh: Effect of Exchangeable Anions, Water Molecules and Solution to Soil Ratios

Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P desorption and the relationship between phosphate sorption and desorption. Among the soil series, the Ghior soil had the highest percent clay (59.32%) and free iron oxide (15241 mg·kg–1) content. Along the catena of the calcareous soils, percent clay contents increased. For sorption study, the soils were equilibrated with 0.01 M CaCl2 solution containing 0, 1, 2, 4, 8, 16, 25, 50, 100 and 150 mg·P·L–1 solution. For desorption, three extractants namely, SO42- (0.005 M) as Na2SO4, HCO3- (0.01 M) as NaHCO3 and distilled water were used at extractant to soil ratios of 30:1, 60:1 and 100:1 (v/w). Among the sorption equations, the Langmuir equation showed better fit to the sorption data at higher P concentrations. The amount of phosphate desorbed by all the three extractants increased significantly with the increasing extractant to soil ratios. Phosphate desorption by and water molecules was highly correlated with pH, percent clay and free iron oxide content of the soil. Significant positive correlation (r > 0.64, P L). Phosphate desorption by SO42- and water molecules was also positively correlated with Freundlich constant, N (r > 0.67, P 0 (r > 0.72, P –0.77, P L). The results suggest that freshly sorbed phosphate ions (inner-sphere complex forming species) can be readily desobed by outer-sphere complex forming species like sulphate and bicarbonate ions. Water molecules also desorbed significant amount of freshly sorbed phosphate from the soil colloids.

The Preparation of TCAS-Loaded Resin and its Adsorption Property to Pb<sup>2+</sup> Ion

A adsorbent for cadmium has been prepared by loading an anion-exchange resin with a novel supramolecular compound named thiacalix[4]arenetetrasulfonate (TCAS). The adsorption properties of Pb2+ on TCAS-loaded resin had been studied and the effects of varying temperature, pH value, adsorption time and initial concentration. Batch extraction studies had revealed a high adsorption ability of the TCAS-loaded resin toward this heavy metal ion with high selectivity. The maximum adsorption capacity of the TCAS-loaded resin toward Pb2+ was 26.32 mg•g-1. The removal rate of Pb2+ in water was up to 99% after 40min at 20°C when a 50mL aqueous solution of Pb2+ (10 mg•L-1) was adsorbed by 0.5g TCAS-loaded resin. The removal percentage steadily retained above 99% when the pH values were in the range of 4 to 7. The adsorption isotherm of the TCAS-loaded resin to Pb2+ ions fits well to linear form of Langmuir sorption equation.

Modeling of kinetics of pertechnetate removal by amino-functionalized glycidyl methacrylate copolymer

Technetium-99 comprises a significant health risk, since edible plants can bioaccumulate and convert it to more lipophilic species that cannot be excreted through urine. Batch kinetics of pertechnetate removal from aqueous solutions by two samples of crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) functionalized with diethylene triamine (PGME-deta) was investigated at the optimum pH value of 3.0, and the initial solution activity of 325 MBq dm−3. PGME-deta was characterized by elemental analysis, mercury intrusion porosimetry, and scanning electron microscopy. Five kinetic models (pseudo-first, pseudo-second order, Elovich, Bangham, and intraparticle diffusion) were used to determine the best-fit equation for pertechnetate sorption. After 24 h, PGME-deta samples sorbed more than 98% of pertechnetate present, with maximum sorption capacity of 25.5 MBq g−1, showing good potential for remediation of slightly contaminated groundwater.

Analysis of water adsorption by wood using the Guggenheim-Anderson-de Boer equation

The Guggenheim-Anderson-de Boer (GAB) three-parameter sorption equation has been used to interpret the adsorption and desorption isotherms of water vapour measured for 21 important cultural heritage wood species used in the past for panel paintings and woodcarving. The equation is capable of describing the full shape of the isotherms and yields meaningful physical parameters, especially the monolayer capacity from which the water accessible specific surface area can be obtained. It is demonstrated that average sorption isotherms can be derived using the GAB equation for the sorption data available for sets of specimens and that moisture properties of various wood specimens or chemically modified wood can be more easily compared.

Sorption of methane on lignite from Polish deposits

Abstract Coal samples from Miocene lignite deposits (ortholignite—ECE-UN 2002) in Belchatow, Adamow, Konin and Turow (Poland) were analyzed to determine the relationships between coal properties and gas capacity. Investigations presented here addressed the occurrence of methane sorbet in lignite deposits within Poland's largest penetrated lignite deposits (e.g., Belchatow, Adamow, Turow and Konin). Lignite samples collected from surface mines were detritic coal with variable contents of xylites. The highest level of xylites (up to 25 vol.%) was found in carbon samples taken from the Belchatow deposit. Samples from other mines contained no more than 10 vol.% xylites. Petrographic compositions were dominated by huminite group macerals (73–88 vol.%) with atrinite, densinite and texto-ulminite, a porous form of ulminite; inertinite groups were less important components (4–8 vol.%). Isotherms were determined for methane sorption at 298 K with test pressure ranges below 1.2 MPa. At a pressure of 1.0 MPa, the largest gas capacity of approximately 1.7 [dm3 STP/kg] was found in the sample from Belchatow. This result may have been attributable to differences in the porosity of the samples; the porosity of the sample from Belchatow was twice as high as the porosities of the other coal samples. This variation in porosity resulted from the lithologic and maceral composition of the coal sample that contained substantial quantities of porous textinite and texto-ulminite. The thermal sorption equation was used to determine the limiting values of isosteric enthalpy of sorption, which suggested weak interactions between methane and the lignite matrix. The residual gas capacity of the tested samples was also determined. All samples exhibited a high residual methane-bearing capacity, which may not only cause methane to be released from coal at a pressure of 1 bar but also may pose a gas risk during mining operations.

Basic isotherm equations of ion microcomponent sorption on macrocomponents of heterogeneous systems

Physicochemical calculations for ion microcomponent sorption on heterogeneous system macrocomponents are converted into general physical formulas.

Sorption behavior of phenanthrene in Yangtze estuarine sediments: Sequential separation

In the present study, phenanthrene was chosen as the probe compound for determining the sorption of PAHs in sediments from Yangtze estuary and nearby coastal area, China. Sorption isotherms were fitted well by the Freundlich and dual models, respectively. Selected sediments were further sequentially separated to remove the carbonate and organic carbon (OC). Calculated OC sorption capacity values based on both H2O2 oxidization and 375°C combustion methods were similar and comparable to the Koc values estimated by the empirical linear sorption equations. Both sorption models and sorption data using sequentially separated samples achieve the similar conclusions: (1) the partition behavior dominated by OC in sediments with foc>0.01; (2) for sediments with 0.001<foc<0.01, OC dominated sorption at relatively high aqueous concentration; whereas mineral phase adsorption dominated sorption at lower concentration especially when Cw/Sw was in the range of 0.0001–0.001 in natural aqueous system.

Properties and sorption studies of polyethylene oxide–starch blended films

A series of polyethylene oxide (PEO) and starch blends were prepared by extrusion and their films prepared by compression molding. The mechanical, barrier, optical, thermal properties and surface morphology characteristics of PEO–starch blended films were studied. The tensile strength of the blended films decreased whereas the haze values increased with an enhanced starch concentration in PEO–starch blends. The inter-molecular interaction between PEO–starch blends were investigated with FTIR. The thermal properties were also analyzed by differential scanning calorimetric (DSC) and thermo-gravimetric analysis (TGA) techniques. Moisture-sorption characteristics of PEO–starch blended films were carried out at 27 °C for water activity (a w) ranged from 0.1 to 0.9. The sorption data at different a w were used to fit different sorption isotherm models as proposed in the literatures. The model constants were determined by linear fitting of the sorption equations. The high coefficient of determination R 2 (ranged from 0.7 to 1) confirms the applicability of the equations employed. The study on the application of such water activity data of PEO/starch blended films on different model equations will be helpful in prediction of durability and functional behavior of moisture sensitive biopolymeric films.

A laboratory batch study on arsenic sorption and desorption on guava orchard soils of Baruipur, West Bengal, India

Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long term detrimental effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable and fruits, are used for human consumption. Therefore, an understanding of the sorption and desorption behavior of As in surface soils is of high importance, because these processes regulate the bioavailability of As in the soil environment. In this study, we have collected soils from guava orchards of Baruipur, West Bengal, and characterized soil chemistry and batch sorption and desorption behavior in the laboratory. The sorption and desorption behavior of As in the soils were examined using the Langmuir and Freundlich sorption equation. Regression analysis of the soil chemical characteristics and sorption equation parameters were also performed. The results suggest that the sorption behavior of arsenate is highly dependent on soil characteristics, specifically organic carbon, clay and Al 2O 3 content of the soils. Whereas desorption behavior is critically influenced by the presence of high concentrations of amorphous and/or crystalline Fe 2O 3 in the soils. Retention of the significant portion of As in the soils (~ 84% of the total) suggests that As in the orchard soils may not be highly bioavailable to plants for uptake. However, more detailed studies will be required to ascertain the role of individual soil components on the As sorption and desorption processes.

Drying kinetics and sorption isotherms of cornelian cherry fruits

In this study, drying kinetics and sorption isotherms of cornelian cherry fruit are investigated under various drying air conditions. Experiments are conducted in a lab-scale convective drier under the following drying conditions: temperatures at 25, 30, 40, 50 and 60 °C; velocities at 0.3, 0.6 and 0.9 m/s; relative humidity values at 25%, 40%, 55% and 70%. Sorption isotherms of the dried cornelian cherry fruit are determined for different temperatures and water activity values at first. At a given water activity, the results show that the equilibrium moisture content decreases with increase in temperature. The experimental sorption curves are then described by the GAB, Oswin, Smith and Halsey models. A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. The GAB model was found to be suitable for describing the sorption curves. Later, drying experiments are conducted for various values for drying air. The experimental moisture data were fitted to some models ...

Moisture Sorption Isotherms and Storage Stability of Spray-Dried Yogurt Powder

Moisture adsorption isotherms of spray-dried yogurt powder were determined at 10, 25, and 40°C using the standard, static-gravimetric method. Experimental data were fitted to five mathematical models (Guggenheim-Anderson-de Boer [GAB], Brunauer-Emmett-Teller [BET], Halsey, modified Oswin, and modified Henderson). A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. The shelf-life of yogurt powder was predicted based on the relationship between permeability coefficient of the packaging material and moisture adsorbed by the powder determined by the GAB equation. Furthermore, the storage stability of spray-dried yogurt powder in terms of quality parameters including moisture content, water activity, color change, and thiobarbituric acid (TBA) value was studied in aluminum laminated polyethylene (ALPE) pouches under storage conditions of 25°C and 50% relative humidity (RH).

Moisture Sorption Characteristics of Chitosan/Polyethylene Oxide Blended Films

Studies on the moisture sorption characteristics of chitosan/polyethylene oxide (PEO) blended films have been carried out at 27 °C for water activity (aw) from 0.1 to 0.9. The sorption data at different aw were used to fit 12 different sorption isotherm models proposed in the literature. The model constants were determined by linear fitting of the sorption equations. The ranges of applicability of water activity for the isotherms reported in the article lie between 0.11 to 0.44 (monomolecular layer) for the BET model and between 0.11 to 0.86 (monolayer & multilayer’s) for Smith, Caurie, Bradley and Oswin. The water activity for Halsey and Chung & Pfost models lies between 0.44 to 0.86 (multilayer) and 0.33 to 0.86 for Henderson and Freundlich models and 0.11 to 0.65 for Kuhn, Linear and Iglesias & Chirife models. The high coefficient of determination R2 (ranges from 0.82 to 1) confirms the applicability of the equations employed. The study on the application of such water activity data of chitosan/PEO blended films on different model equations will be helpful in prediction of durability and functional behavior of moisture sensitive biopolymeric films

Impact of Kerogen Heterogeneity on Sorption of Organic Pollutants. 2. Sorption Equilibria

Phenanthrene and naphthalene sorption isotherms were measured for three different series of kerogen materials using completely mixed batch reactors. Sorption isotherms were nonlinear for each sorbate-sorbent system, and the Freundlich isotherm equation fit the sorption data well. The Freundlich isotherm linearity parameter n ranged from 0.192 to 0.729 for phenanthrene and from 0.389 to 0.731 for naphthalene. The n values correlated linearly with rigidity and aromaticity of the kerogen matrix, but the single-point, organic carbon-normalized distribution coefficients varied dramatically among the tested sorbents. A dual-mode sorption equation consisting of a linear partitioning domain and a Langmuir adsorption domain adequately quantified the overall sorption equilibrium for each sorbent-sorbate system. Both models fit the data well, with r2 values of 0.965 to 0.996 for the Freundlich model and 0.963 to 0.997 for the dual-mode model for the phenanthrene sorption isotherms. The dual-mode model fitting results showed that as the rigidity and aromaticity of the kerogen matrix increased, the contribution of the linear partitioning domain to the overall sorption equilibrium decreased, whereas the contribution of the Langmuir adsorption domain increased. The present study suggested that kerogen materials found in soils and sediments should not be treated as a single, unified, carbonaceous sorbent phase.

Kinetics of hexavalent chromium sorption on amino-functionalized macroporous glycidyl methacrylate copolymer

Two samples of macroporous crosslinked poly(glycidyl methacrylate- co-ethylene glycol dimethacrylate), poly(GMA- co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and functionalized with ethylene diamine and diethylene triamine. The kinetics of Cr(VI) sorption by amino-functionalized poly(GMA- co-EGDMA) was investigated under non-competitive conditions. Competitive kinetics was studied from following multicomponent solutions: Cu(II) and Cr(VI); Cu(II), Co(II), Cd(II) and Ni(II); Cr(VI), Cu(II), Co(II) and Cd(II) solutions. Two kinetic models (the pseudo-first and pseudo-second-order) were used to determine the best-fit equation for the metals sorption by poly(GMA- co-EGDMA)-en and poly(GMA- co-EGDMA)-deta.

Evolution of internal stress during drying, cooling and conditioning of rubberwood lumber

In an attempt to develop a real-time measurement technique for an internal stress perpendicular to grain in the radial direction of rubberwood lumber during drying and conditioning, a novel design of a force measuring device, consisting of a restrained half-sawn specimen and a restrained free shrinkage specimen, was constructed. The measured force was verified with a differential released strain obtained from the conventional McMillen slice technique. The device was then employed to investigate the internal stress evolution during drying and conditioning of rubberwood lumber. It was shown that the force measured using the device strongly correlates with the differential released strain. The extents of the internal stress characteristics such as the maximum tensile and compressive forces and the reciprocal of time at stress reversal obey the Arrhenius equation and the adapted equation of sorption for the temperature and humidity dependences, respectively. The results also indicate that cooling under relatively high humidity after drying improves the internal stress relaxation process during conditioning. Possible application of the technique in kiln drying of rubberwood has been demonstrated. The measured force could be used as controlling parameter for an adaptive wood drying control system taking into account real-time material response of wood during drying and conditioning.

Sorption of p-nitrophenol by anion–cation modified palygorskite

A series of anion–cation modified palygorskites were prepared by microwave irradiation, and characterized with FT-IR. Compared with natural palygorskite, the p-nitrophenol sorption capacity with anion–cation modified palygorskite was significantly improved. The maximum sorption capacity (137.74 mg g −1) was obtained with the mass ratio 1:4 and 3:10 of hexadecyltrimethylammonium bromide to sodium dodecyl sulfate and the surfactant to palygorskite of at 313 K. The sorption equilibrium was in accordance with the Langmuir isothermal sorption equations. Thermodynamic function calculated showed that the sorption was a spontaneous and exothermic process. Free energy of the sorption increased with the increase of the temperature. The sorption of p-nitrophenol followed the pseudo-second-order process (sorption rate constant: 0.00453 mg −1 min −1).

Two-dimensional numerical modeling of chemical transport–transformation in fluvial rivers: formulation of equations and physical interpretation

Based on previous work on the transport–transformation model of heavy metal pollutants in fluvial rivers, this paper presents the formulation of a two-dimensional model to describe chemical transport–transformation in fluvial rivers by considering basic principles of environmental chemistry, hydraulics and mechanics of sediment transport and recent developments along with three very simplified test cases. The model consists of water flow governing equations, sediment transport governing equations, transport–transformation equation of chemicals and convection–diffusion equations of sorption–desorption kinetics of particulate chemical concentrations on suspended load, bed load and bed sediment. The chemical transport–transformation equation is basically a mass balance equation. It demonstrates how sediment transport affects transport–transformation of chemicals in fluvial rivers. The convection–diffusion equations of sorption–desorption kinetics of chemicals, being an extension of batch reactor experimental results, take both physical transport, i.e. convection and diffusion, and chemical reactions, i.e. sorption–desorption into account. The effects of sediment transport on chemical transport–transformation were clarified through three simple examples. Specifically, the transport–transformation of chemicals in a steady, uniform and equilibrium sediment-laden flow was calculated by applying this model, and results were shown to be rational. Both theoretical analysis and numerical simulation indicated that the transport–transformation of chemicals in sediment-laden flows with a clay-enriched riverbed possesses not only the generality of common tracer pollutants, but also characteristics of transport–transformation induced by sediment motion. Future work will be conducted to present the validation/application of the model with available data.