Sorption Equation Research Articles

Groundwater Solute Transport Modeling: Effects of Transport and Fate

In this paper, the solution of the advection-dispersion equation with different sorption values is used for the prediction of solute concentration in groundwater. Sorption process in the groundwater is complex, due to increasing the groundwater pollution the effect of different chemical transport plotted. The fate and sorption process of different chemical different degradation constant. We used the analytical solution to evaluate the transport phenomenon and analysis of the chemical dissolved in groundwater. The solute transport model simulated with the analytical solution and final result obtained using MATLAB software. The solution of a test problem based on the sequential degradation of the different chemical in the groundwater. This solution of equilibrium and rate of sorption dynamics of processes is imperative for accurate fate and transport modeling. The present study shows the effects of advection, dispersion/diffusion, and sorption equation on the saturated media of soil. MATLAB software used for analyzing the solution of groundwater and showing the different case taking care of saturated aquifer and with different void ratio of soil its shows that the soil parameter is also impotent parameter and its effect can see in plot between concertation vs time. The solute transport model simulated with the analytical solution and final result obtained using MATLAB software. The solution of a test problem based on the sequential degradation of the different chemical in the groundwater. This study compares the solute concentration with respect to distance and its different hydraulics conductivity of dense sad and lose.

Simultaneous removal of cationic, anionic and organic pollutants in highly acidic water using magnetic nanocomposite alginate beads

Novel magnetic nanocomposite alginate beads are fabricated for the simultaneous removal of cationic, anionic and organic pollutants in highly acidic water. Copper, phosphate and toluene are used as representative cationic, anionic and organic pollutants respectively. The alginate beads were impregnated with a nanocomposite material composed of zeolites, activated carbon, layered double hydroxides and magnetic nanoparticles bound together by xanthan gum. A 3:4:1 aspect ratio (alginate: nanocomposite: xanthan gum) is used for fabrication of the beads. The beads show removal percentage for phosphate at 97.9%, copper at 81.8% and toluene at 43.4% and adsorption capacities of 60.24 mg g–1, 120.77 mg g–1 and 25.52 mg g–1 respectively. Isothermal studies show that the Langmuir isotherm model is the governing equation for sorption. Pseudo-second-order model is the governing equation for the kinetics of sorption. The sorption process is also spontaneous and exothermic. This sorbent shows great potential to be used for simultaneous removal of cationic, anionic and organic pollutants removal in water.

Изучение влияния состава и природы элюента на сорбцию бензимидазола и его производных на сверхсшитом полистироле методом ВЭЖХ

The effect of water-acetonitrile and water-methanol eluents composition on newly synthesized benzimidazole derivatives sorption by supercrosslinked polystyrene (SCP) using high performance liquid chromatography was studied. It is shown that the nature of the organic modifier affects on the considered biologically active compounds sorption. The angular coefficients of the Snyder-Sochevinsky equation, characterizing the number of organic modifier molecules, displaced by one molecule of sorbate, for benzimidazole derivatives, are calculated. The angular coefficients was calculated from the dependence, characterized by a high coefficient of determination. The article demonstrated that the Snyder-Sochevinsky model could be used for describing of all studied compounds sorption in the system “SCP – water-methanol eluent” and for describing of volume sorbates with hydrophobic substituting groups sorption in the system “SCP – water-acetonitrile solution”. The value of the slope of the Snyder-Sochevinsky equation of benzimidazoles sorption from water-methanol solutions is higher than that from water-acetonitrile solution; this fact indicates a lower elution power of the water-methanol eluent in compare to water-acetonitrile eluent. The Snyder-Sochevinsky model is not fulfilled in the concentration range from 75% to 85% of acetonitrile for small volume benzimidazole molecules containing hydrophilic amino and hydroxymethylene groups in the «SCP – water-acetonitrile eluent» system. The composition of the mobile phase influence of benzimidazoles sorption was studied. It is demonstraited the relationships between volume fraction of the organic modifier increase and decreases of benzimidazoles sorption.

Removal of strontium from aqueous solutions by sodium dodecyl sulfate-modified palygorskite

Palygorskite (PAL) was modified with sodium dodecyl sulfate (SDS) for the removal of Sr(II) from aqueous solutions. Analysis of the structural characteristics of PAL before and after modification showed that PAL was successfully modified with SDS. Sorption experiments were conducted in batch mode under optimum conditions to evaluate the effect of initial pH and co-existing ions on the removal of Sr(II) by SDS-modified PAL. The equilibrium sorption isotherm data for Sr(II) were analyzed using Freundlich and Langmuir isotherm sorption equations, and the data fitted well to the Freundlich isotherm model. Pseudo-first-order and pseudo-second-order kinetic models were examined, and the sorption of Sr(II) showed better agreement with the pseudo-second-order kinetic model (r2 > 0.99). The desorption experiments indicated that the SDS-modified PAL having sorbed Sr(II) does not release significant amounts of Sr(II) into the environment under natural conditions, thus avoiding secondary pollution.

Application of the Theory of Volume Filling of Micropores to Analysis of the Structure of Nanoporous Fibers and Properties of Swelling Fiber-Forming Polymers

The influence of the mechanism of sorption processes on the distribution parameters of the dimensionless value of sorption over a dimensionless chemical potential is analyzed. In the equation of the theory of volume filling of micropores, the rank of the distribution n > 1 characterizes convex isotherms of vapor sorption in microporous adsorbents. The rank of distribution n <1 corresponds to the formation of a homogeneous sorption solution in the supramolecular structure of the swelling polymer. The limitations of the thermal sorption equation are shown, which must be considered when analyzing the microporous structure and properties of fiber-forming polymers.

Sequestration Specificity of Single or Co-existing Benzene, 1,3,5-Trimethylbenzene, and Naphthalene in Soil

The sequestration (aging) of petroleum hydrocarbons in soil can have a significant effect on the remediation of contaminated sites, but organic chemicals and how they co-exist can result in different sequestration abilities. In this study, sorption, methanol extraction, and sequestration of single and co-existing benzene, 1,3,5-trimethylbenzene, and naphthalene in soil were investigated to evaluate their sequestration ability in soil and the influence of co-existing organic chemicals. A higher linear adsorption coefficient based on the linear sorption equation (ke) was observed for naphthalene (11.5–25.0) compared with benzene (3.8–3.9) and 1,3,5-trimethylbenzene (2.8–5.6), followed by a lower linear methanol extraction coefficient based on the methanol extraction equation (km = 0.3) and a higher linear sequestration coefficient based on the linear sequestration equation (ks = 0.7). The co-existence of benzene, 1,3,5-trimethylbenzene, and naphthalene increased the sorption ability of 1,3,5-trimethylbenzene (ke increased from 2.8 in the single system to 5.6 in the mixed system) and naphthalene (ke increased from 11.5 in the single system to 25.0 in the mixed system) due to their larger molecular size and higher molecular polarity; however, this was not observed for benzene (ke ranged from 3.8 to 3.9 in the single and mixed systems). In summary, the co-existence of benzene, 1,3,5-trimethylbenzene, and naphthalene does not affect methanol extraction and sequestration ability.

Moisture Sorption Isotherms and Prediction Models of Carboxymethyl Chitosan Films from Different Sources with Various Plasticizers

Carboxymethyl chitosan (CMCH) from different chitosan sources (shrimp, crab, and squid) and molecular sizes (polymer and oligomer) were synthesized via carboxymethylation reaction. The CMCH films were prepared by solution casting. All the CMCH films had high water solubility, higher than 85% of the dry matter of the films. The sorption isotherm of the CMCH films was evaluated at several values of relative humidity (0% RH, 23% RH, 34% RH, 43% RH, 65% RH, 77% RH, and 86% RH) at 25 ± 1°C. The equilibrium moisture content values of all the CMCH films were low at lower aw but increased considerably above aw = 0.65. The sigmoidal moisture sorption isotherms of this product can be classified as type II. Understanding of sorption isotherms is an important prerequisite for the prediction of moisture sorption properties of films via moisture sorption empirical models. The experimental data were analyzed and fitted by the nine sorption models. The various constants determined by linear fitting of the sorption equation with r2 values were in the range of 0.7647 to 0.999. The GAB model was found to be the best-fitted model for CMCH films (aw = 0.23–0.86, 25 ± 1°C), and the model presented the optimal root-mean-square percentage error (%RMS) values when compared with other models. In conclusion, it can be stated that the GAB model was found to be better estimated for predicting the CMCH films than other models. Therefore, the constant derived from different sorption models were applied for use in terms of information and for the determination of the stability of CMCH packaging films for specific end uses.

Neumann boundary value problem for system of equations of non-equilibrium sorption

Neumann boundary value problem for system of equations of non-equilibrium sorption

Adsorption and transport behavior of arsenate on saline-alkali soils of tidal flat of Yellow Sea, Eastern China

ABSTRACTThe adsorption of arsenic plays an important role in the mobility of this toxic element in the saline-alkali soil environment. The adsorption and transport of arsenate [As(V)] in saline-alkali soils were investigated in this study. The results of kinetic experiments indicated that the rate of As(V) adsorption was initially rapid and then became slow, which were modeled well with the pseudo-second-order rate model. The adsorption isotherms were best fitted by the Langmuir and Freundlich sorption equation. The maximum adsorption capacity of soil L1was the lowest (202.8 mg/kg), and that of soil D1 was the highest (686.6 mg/kg). The difference in adsorption capacity in five soils was mainly due to the CaCO3 content. The CaCO3 enhanced As(V) adsorption due to the adsorption and coprecipitation of calcium with As(V). The column experiments demonstrated that the transport of As(V) in soils was detained and the degree of detainment increased with decreasing As(V) concentration.

The third boundary value problem for the system of equations of non-equilibrium sorption

The third boundary value problem for the system of equations of non-equilibrium sorption

Modeling of the reinforced concrete structure performance at joint influence of mechanical and chemical loads

The present work offers formation principles of reinforced concrete structures design models that are used in the environment with joint influence of mechanical loads and chemically aggressive media. The model is proposed to be described with an equations system of mechanics and physics and chemical kinetics which includes: static equations (L. Navier); geometric equations (A. Cauchy); physical equations (R. Hooke, etc.); kinetic equations of aggressive medium transfer (A. Fick); kinetic equation of substances interaction (K. Guldberg – P. Waage); sorption equation (I. Langmuir). Practical methods for assessing the kinetics of estimated parameters change were developed. Methods for assessing a service life of reinforced concrete structures used in the joint conditions influence of mechanical loads and chemically aggressive media allowing predicting the service life of a structure at different stages - from design to physical wear - were developed.

Use of a 3D finite element model for post fumigation phosphine movement analysis: Presentation

Phosphine is a dangerous gas commonly used in fumigations throughout the world. Grain that has not fully released the phosphine it absorbed during fumigation may continue to desorb phosphine into the headspace of a storage structure. U.S. OSHA standards for handling phosphine state the acceptable limit at 0.3 ppm. If this limit is exceeded grain handling may become dangerous. It is important to understand the process of phosphine venting and desorption in order to ensure safe handling of fumigated grain in silos and during shipments. In order to achieve this, the venting and release of phosphine was studied on location in a well-sealed grain silo in Lake Grace, Western Australia, to serve as a set of data for verification of a computational model. This situation was then modeled using a 3D finite element model and compared to the real world results. Results were calculated using two fumigant desorption models based on previous literature, a reversed sorption model and an air-grain equilibrium model. Simulations reproduced accurate trends of desorption but did not accurately reproduce the quantity of fumigant, with a 55.5% error for the model based on reversed sorption equations and 86.3% error for the air-grain equilibrium based model. For both models, simulations were conducted to compare the effectiveness of existing grain venting regulations at producing grain that is within safe handling limits. These results highlight the necessity for continued desorption research and the importance of following venting guidelines.

Cadmium removal by a low-cost magadiite-based material: Characterization and sorption applications

The sorption of cadmium from nitrate medium at room temperature was carried out using solid phase magadiite and magadiite impregnated with Cyanex 272 [bis(2,4,4-trimethylpentyl)phosphinic acid]. The sorbent materials have been characterized by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy-energy dispersive X-ray analyses (SEM-EDX) and thermogravimetric analysis (TGA/DTG). The UV–vis spectrophotometry technique was used to determine the amount of Cyanex-272 inserted into the solid support. Various parameters such as pH of the aqueous solution, initial Cd(II) concentration and equilibrium time were studied. The sorption data fitted the Sips sorption equation, and the sorption kinetics follows the model of the pseudo-second order. The maximum sorption capacity of Cd(II) was found to be 64.06 mg g−1 and 49.45 mg g−1 (i.e., 0.57 and 0.44 mmol g−1) from magadiite and magadiite-Cyanex 272, respectively. The elution of the materials was performed with 0.1 M HNO3 solution, and 80% of the initial sorbed cadmium was recovered.

Preparation and characterization of green adsorbent from waste glass and its application for the removal of heavy metals from well water

Waste glass disposal causes environmental problems in the cities. To find a suitable green environmental solution for this problem low cost adsorbent in this study was prepared from waste glass. An effective new green adsorbent was synthesized by hydrothermal treatment of waste glass (WG), followed by acidic activation of its surface by HCl (WGP). The prepared adsorbent was characterized by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), and BET surface measurement. The developed adsorbent was used for the removal of heavy metals (Cd, Cu, Fe, Pb and Zn) from well water. Batch experiments were conducted to test the ability of the prepared adsorbent for the removal of Cd, Cu, Fe, Pb and Zn from well water. The experiments of the heavy metals adsorption by adsorbent (WGP) were performed at different metal ion concentrations, solution pH, adsorbent dosage and contact time. The Langmuir and Freundlich adsorption isotherms and kinetic models were used to verify the adsorption performance. The results indicated high removal efficiencies (99-100%) for all the studied heavy metals at pH 7 at constant contact time of 2 h. The data obtained from adsorption isotherms of metal ions at different time fitted well to linear form of the Langmuir sorption equation, and pseudo-second-order kinetic model. Application of the resulted conditions on well water demonstrated that the modified waste glass adsorbent successfully adsorbed heavy metals (Cd, Cu, Fe, Pb and Zn) from well water.

Equilibrium and Kinetic Studies on the Removal of Acid Red-14 from Aqueous Solutions Using PSMA

The use of low-cost and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. In this study, not hydrolyzed poly(styrene-alternative-maleic anhydride) (PSMA) polymer have been used as new synthetic adsorbent to removal of acid red-14 dye from aqueous solutions (industrial wastes). Batch sorption studies have been carried out to determine the effect of agitation time, pH, adsorbent dose, and initial concentration of the sorbate and temperature. The effect of electrolyte interference such as \( {\text{Na}}^{ + } \) and \( {\text{Cl}}^{ - } \) on dyes removal efficiency was investigated. The acid red 14 dye showed maximal amount of sorption capacity as 5.12 mg/g at pH 6.1 and 25 °C. Equilibrium data were fitted with Langmuir and Freundlich isotherms to find the best fit, and it was found that the adsorption of this dye on adsorbents particles are monolayer and correspond to the Langmuir isotherm. Adsorption kinetics were investigated using pseudo-first-order and pseudo-second-order rate equations and kinetic data followed the pseudo-second-order rate equation for sorption of this dye on PSMA adsorbent. The application of adsorbents performance was tested with real samples which contain limit exceeded amount of foresaid dyes which had been taken from a Dyeing Factory. This study provides good background to development of dye removal in waste waters by polymeric sorbent.

The verification of the estimation of transport and sorption parameters in the MATLAB environment. Column test

Mathematical modelling of the migration of pollutants in the groundwater environment requires knowledge of the values of transport and sorption parameters. The aim of this study was 1) to determine the values of advection, dispersion and sorption parameters of selected tracers that are transported through a porous medium, and 2) to verify the applied parameters estimation procedure. The authors examined the migration of a solution containing conservative and reactive tracers (chloride, nitrate, lithium and ammonium ions) through a sample of medium sand. The soil sample for the column test was taken from an aquifer near the Tursko groundwater intake (Wielkopolska province, Poland). The parameter estimation procedure, conducted in the MATLAB environment, included the numerical solution of the differential equations of transport and sorption, and the application of the numerical optimization method. During the identification, the authors tested twelve mathematical models including the advection-dispersion model, as well as single and hybrid (i.e. two-site) sorption models. The authors made a comparison of parameter values obtained by means of the global and local optimization method. The fitting quality was assessed by calculating the root mean square error RMSE and correlation coefficient r. As a result of the research, the authors determined the values of the advection-dispersion parameters: hydraulic conductivity k, effective porosity ne, and longitudinal dispersivity α. The authors found out that the nature of lithium ions migration is best captured by the single sorption model (equilibrium sorption), whereas the nature of ammonium ions migration is by the hybrid model with irreversible sorption. Lithium ions on the tested soil revealed low sorption intensity, ammonium ions showed medium intensity, while nitrate ions were transported at the same rate as chloride ions, exhibiting no retardation. The verification of parameter estimation in the MATLAB environment was carried out by comparing it against the alternative, well-known and often tested method, based on analytical solutions of the transport and sorption equation, combined with optimization within the FIELD and KLUTE-STEP programmes.

Spatial Analysis of Stover Moisture Content During Harvest Season in the U.S.

Abstract. The moisture content of a maturing crop varies as the harvest season progresses. For crop residues such as corn stover, moisture content at the time of harvest can be as high as 75% (wet mass basis) to less than 20% depending on the geographic location (climate conditions) and stage of harvest. Biomass moisture content is critical for baling and extended storage. It is therefore essential to have an estimate of the quantities of corn stover available as wet or dry for various parts of the U.S. To this end, we analyzed hourly weather data (temperature, humidity, and rainfall) from the Typical Meteorological Year v.3 (TMY3) dataset developed by the National Renewable Energy Laboratory. A recently published set of equations for calculating the moisture content of stover as a function of hourly temperature, humidity, and rainfall were used. The annual start and end of corn grain harvest along with annual grain production (in bushels) for each state were extracted from USDA National Agricultural Statistics Service reports. Using these datasets and moisture sorption equations, the percentage of corn stover tonnage with moisture content less than 20%, between 20% and 40%, or greater than 40% was estimated from the length of time that the biomass was in these moisture content ranges. These calculations were carried out for several locations within each of the states for which TMY data were available. It was concluded that about 37.2% of corn stover is dry (&amp;lt;20% moisture content), whereas 36.5% is wet (&amp;gt;40% moisture content) nationwide. The remaining 27.0% of corn stover is between 20% and 40% moisture content. Keywords: Corn stover, Equilibrium moisture content, Field drying, Moisture content, Stover harvest, Typical Meteorological Year data.

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application.

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η − γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment.

Moisture sorption isotherms and thermodynamic properties of Oak wood (Quercus robur and Quercus canariensis): optimization of the processing parameters

The aim of this paper was to determine the moisture desorption isotherms and essentials thermodynamic properties of two Oak wood varieties. Desorption isotherms were measured using a static gravimetric method at 50, 60, 70 and 80 °C within the range of 5–90 % relative humidity. The equilibrium moisture content decreased with increasing temperature and decreased with decreasing relative humidity at a constant temperature. The ‘Thermodynamic’ sorption equation was found to be the best for describing the experimental moisture sorption isotherms of woods within the range of temperature and water activity investigated. The Fiber saturation point, deduced from the ‘Thermodynamic’ model parameters, depends on the temperature and varying from 22.6 to 54.4 (% kg water/kg dry matter). Isosteric heat of desorption and differential entropy were calculated by applying Clausius–Clapeyron equation to the desorption data fitted by the ‘Thermodynamic’ model. The isosteric heat of desorption and the differential entropy decreased with increasing moisture content according to an exponential law equation and varying from 2.03 to 31.14 kJ/mol and from 73.98 to 4.34 J/(mol K), respectively. The linear relationship between differential enthalpy and entropy satisfied the enthalpy–entropy compensation theory. The sign of Gibbs free energy was found to be positive (+283 J/mol) and (+97 J/mol) for Quercus robur and Quercus canariensis, respectively. The isokinetic temperature was found to be greater than the harmonic temperature. Based on the enthalpy–entropy compensation theory, it could be concluded that the moisture desorption isotherm of Oak wood is a non-spontaneous and enthalpy-controlled process.

Moisture Sorption Isotherms of Yogurt Powder Containing Candied Chestnut Puree

Yogurt powder was produced by freeze drying and with added candied chestnut puree at ratios of 5, 10, and 20 % by weight. Moisture sorption isotherms of yogurt powder samples, plain (YP), and containing 5, 10, 20% candied chestnut puree (CCP) were determined at 25°C using the standard, static-gravimetric method. The experimental adsorption data of yogurt powders at 25°C were fitted to 14 sorption equations which are most widely used to fit experimental sorption data of various food materials. The parameters of the sorption models were estimated from the experimental results by using the nonlinear regression analysis. The GAB model gave the closet fit to the sorption data of freeze dried yogurt powders with candied chestnut puree at 25°C. BET, Ferro Fanton, Henderson, Halsey, Oswin and Modified Oswin models are also acceptable for describing the adsorption isotherms for freeze dried yogurt with candied chestnut puree at 25°C.