Showing 15 results for Adsorption
M. Maftoun, H. Haghighat Nia, N. Karimian,
Volume 4, Issue 2 (7-2000)
Abstract
As apparent Zn recovery in mineral soils (saturated and unsaturated) is nill, the precise assessment of processes responsible for Zn retention in these soils is of great importance. A laboratory study was conducted to characterize Zn adsorption in eight lowland calcareous soils. The fit of sorption data was evaluated by Freundlich and Langmuir isotherms. In this study, 2-g soil samples were equilibrated for 24 hours with 40 mL 0.0lM CaCl
2 solution containing 5 to 500 mg Zn L
-1. The amount of Zn adsorbed was calculated based on the difference between the initial and equilibrium Zn concentrations.
Zinc adsorption data were fitted to a linear form of Freundlich equation. However the Langmuir isotherm was divided into two distinct linear portions, representing two different types of adsorption sites. The Langmuir K1 was higher and adsorption maxima (b1) was lower in part I (corresponding to lower Zn concentration) than in part II (corresponding to higher Zn concentration). Thus, it seems that in parts I and II, sites are more important for their high adsorption energy and adsorption capacity, respectively. Langmuir adsorption maxima (b2) was positively correlated with clay content, CCE and P concentration and negatively correlated with CEC.
M. Soleimani, M. Shahedi,
Volume 10, Issue 2 (7-2006)
Abstract
Isotherm curves are useful for the designing of dryer as well as controling of the seed moisture content during storage and drying process. To study the curves, this research was performed on the basis of two factorial experiments including three factors: (1) hybrid at two levels (Three Way Cross 647 and Single Cross 704) (2) temperature at 6 levels (from 5 to 55°C) and (3) Relative Humidity (RH) at 5 levels (from 10 to 90 percent) for the analysis of the adsorption and desorption phenomena. For maintaining RH at the above mentioned ranges, glycerol solutions with different concentrations were used. The results showed that the relationship between solutions concentration and their RH was non-linear and somewhat related to temperature. Also, statistical analysis displayed that for 3 factors of tepmerature , RH and hybrid, the effects on Equilibrium Moisture Content (EMC) in both adsorption and desorption phenomena were significant at α=1%. Comparisons of means showed that hybrid 704 had higher EMC values than did hybrid 647 under the same conditions, in other words, hybrid 704 produced lower aw than did hybrid 647 at the same moisture content. Fitting experimental values on non-linear models (Henderson, Chung-Pfost and Oswin) showed Oswin as the best model for adsorption and desorption curves for hybrid 704 and also for adsorption curve for hybrid 647 , but the best model for desorption curve for hybrid 647 was Chung-Pfost.
A. Safadoust , A. Mahboubi, M. R. Mosaddeghi, Gh. Khodakaramian, A. Heydari,
Volume 15, Issue 57 (10-2011)
Abstract
In this study, the transport of nalidixic acid-resistant Escherichia coli (E. coli NAR) through two soils of sandy loam and clay loam was investigated. Saturated and unsaturated flow conditions were applied at two temperatures of 5 and 20ºC. Leaching was done using large repaired soil columns which had been subjected to physical weathering. A 20-cm diameter disk infiltrometer was set up to establish the steady-state flow conditions. Effluent was sampled at three depths of 15, 30 and 45 cm of soil columns. Saturated flow condition, temperature of 20 ºC and clay loam soil resulted in increasing the bacteria concentration in the leachate. Filtration coefficient and relative adsorption indices in sandy loam soil (average flow conditions, temperature and depth) were greater than those of clay loam soil with the respective values of 33% and 23%. These results may be related to the instability of soil structure and abundance of micropores in the sandy loam columns. In other words, the bacteria were physically blocked and entrapped in the fine pores of sandy loam soil. Effluent bacteria concentration decreased by depth of soil column, indicating the effect of soil on bacterial filtration as a natural filter. Leaching with cold water led to decrement of flow rate and consequently increment of bacterial filtration in the two soils of clay loam and sandy loam (average flow conditions, temperature and depth) with the respective values of 100% and 68%.
M. Liaghat, F. Khormali, S. A. Movahedynaeini, E. Dordipour,
Volume 16, Issue 61 (10-2012)
Abstract
Studies on the soils of western Golestan province show that regardless of increased rain and presence of clay minerals with high cation exchange capacity, potassium extractable with ammonium acetate is low. In order to find the reason for this low amount of available K, clay minerals and micromorphology of the soil porosity were studied. Twenty disturbed and undisturbed samples from each horizon were taken for physicochemical properties, mineralogy and micromorphological studies. Four selected profiles included Gypsic Aquisalids, Typic Endoaquepts, Typic Calcixerolls and Typic Hapludalfs. The results showed that in addition to the clay content and type of clay minerals in soils that can affect soil available K (Kava.), it seems soil porosity can also affect Kava. mainly through their effects on extension of roots, water and nutrients transmission. Favorable content of clay and dominance of smectites in Mollisols and also higher porosity and dominance of channel porosities caused the presence of higher Kava, in these soils. presence of HIS. poor soil drainage, reduction of Fe3+ in smectite crystal lattice in Inceptisols, and also less amount of porosities caused the presence of higher potassium fixation and reduction of Kava. in these soils.
L. Divband, S. Boroomand Nasab, M. Behzad, J. Abedi Koupai,
Volume 17, Issue 65 (12-2013)
Abstract
Heavy metals in water resources are one of the most important environmental problems in most of countries. Up to now, various methods for removing these metals including using low price materials have been used. In this study, two new absorbents (zizyphus spinachristi leaf and its fly ash) were studied for adsorption of cadmium from aqueous solutions using batch experiments. The effect of contact time, pH, and amount of adsorbent on adsorption efficiency was evaluated and the best kinetic and isotherm model was determined. Results showed that optimal absorption of pH was 5 and 6 for zizyphus spinachristi leaf and its fly ash, respectively. The equilibrium time was 45 min for zizyphus spinachristi leaf and 30 min for ash. Adsorption efficiency was increased by increasing the adsorbent dose. By comparing the parameters of isotherm models, it was observed that the cadmium adsorption capacity of fly ash (4.27 mg/gr) was higher than that of zizyphus spinachristi (3.91 mg/gr).
A. Samadi, E. Sepehr,
Volume 17, Issue 65 (12-2013)
Abstract
In order to determine optimum equilibrium solution phosphorus (P) concentration using P adsorption isotherm and obtain model(s) by integrating soil solution P concentration, physicochemical properties, and soil P test (available P) which predict standard P requirements to achieve maximum yield, laboratory and glasshouse experiments were conducted on 36 soil samples belonging to 15 soil series and 14 soil samples, respectively. Using wheat as a test crop, the glasshouse experiment was laid out with five P levels in a completely randomized design with three replications. Concentrations of P in solution established by adding P in the pots estimated from the sorption curve ranged from 0.2 to 1.2 mg P/L including check treatment (no P). The results showed that equilibrium solution P concentration (EPC) was almost low in comparison with the requirement for most crops (<0.2 mg/L). The amount of P adsorbed by the soils at 0.2 mg/L EPC ranged from 5 to 114 mg/kg soil. The phosphate adsorption was well described by Freundlich (R2 = 0.96) and Langmuir (R2 = 0.88) isotherms. Langmuir maximum adsorption (Xm) and Freundlich coefficient (aF) estimated from Langmuir and Freundlich equations ranged from 127 to 238 mg P /kg soil and from 43 to 211 mg P/kg, respectively. Yield of wheat in all soils approached maximum as adjusted P levels were increased to 0.4 mg P/L. The results showed that some soils studied were adequate in available P by the NaHCO3 test, but required an amount of P fertilizer by the isotherm P requirement test to obtain maximum biomass production. Soil clay content was significantly related to the soil P sorption indices, P0.4 (P sorbed at 0.4 mg P/L EPC) (R = 0.40, P<0.01), PBC (P buffering capacity) (R = 0.54, P<0.001), aF (R = 0.48, P<0.01), and Xm (R = 0.40, P<0.01). Total CaCO3 and Active CaCO3 were found to be less important factors affecting P adsorption. Using stepwise regression analysis resulted in a useful regression model including the combination of Olsen P and clay content for the prediction of standard P requirement (P0.4).
A. Mohammadi, M. Chorom, N.hosseini Zare, H. Amerikhah, A. Ramazan Poor,
Volume 17, Issue 65 (12-2013)
Abstract
The purpose of this study was to investigate cadmium adsorption through Freundlich and Langmuir equations in sediments of Karun River in three hydrometric stations (5th Ahvaz Bridge, Darkhovin and Khorramshahr) in the low-water and high-water seasons. Fitting of data from experiments on cadmium absorption to Freundlich and Langmuir equation showed they are compatible. According to the conducted experiments, there was a significant difference at 0.01 levels between b coefficient of Langmuir equation with the organic matter percentage and the clay content in both Low and high water seasons, while there was no significant difference between k coefficient of Langmuir equation with the organic matter percentage and the clay content for the two seasons. The results also suggested that there is a significant relationship between Kf of Freundlich equation with the organic matter percentage and clay content, at significant levels of 0.05 and 0.01 for the organic matter percentage and the clay content, respectively. Comparison of the means of low and high water seasons revealed that there is no significant relationship between Langmuir coefficients, whereas in Freundlich equation, a significant difference at 0.01 level was observed between kf coefficients. Generally, the obtained results indicated that cadmium adsorption by sediments in low-water season is higher than high-water season. Also, cadmium adsorption by the 5th Ahvaz Bridge sediments due to the sandy texture was less than those adsorbed by both Darkhovin and Khorramshahr sediments.
N. Mazloom, R. Khorassani, A. Fotovat, Y. Hasheminezhad,
Volume 17, Issue 66 (2-2014)
Abstract
The reclamation of salt-affected soils which occur on 831×106 ha can be effective in increasing agricultural production. Cultivation of plant species which are resistant to salinity can improve the soil by increasing the solubility of calcite and releasing the calcium in soil solution. This study was conducted as a column experiment with a saline-sodic soil (SAR = 23.8, EC= 12.88 dS m-1, pH= 7.7, CaCO3= 15.15 %). Three plant treatments including Sesbania acuelata, Cyanodon dactylon and Rubia tinctorum, and three chemical treatments including gypsum in two levels (50% and 100% gypsum requirement) and sulfuric acid with a control were arranged. All treatments were replicated 3 times. The soil columns were similarly leached by 41 liters of tap water during 30 days in 8 stages. After leaching, SAR and EC in soil, the amounts of sodium in leachate and total amount of sodium in plants shoot were determined. Results showed that the SAR was decreased compared to control by the plant treatments and the chemical amendments by about 59% and 65%, respectively. Moreover, two plants of Cyanodon dactylon and Rubia tinctorum had maximum amount of leachate sodium, which shows an impressive role of these plants in dissolution and leaching of exchangeable or sediment sodium in comparison with the other treatments. According to salient performance of phytoremediation in improvement of physicochemical properties of soil compared to chemical amendments, phytoremediation can be recommended as a profitable low-cost and effective method for remediation of saline-sodic soils.
R. Samiei Fard, H. Matinfar,
Volume 21, Issue 4 (2-2018)
Abstract
Reflectance spectroscopy is a fast and safe method to predict soil physicochemical and biological properties in low cost ways. Traditional methods to determine soil properties require spending a lot of time and money so that farmers are generally reluctant to use the results of laboratory measurements in soil and water management. Reflectance spectroscopy in the spectral range of 400-2500 nm (VNIR) is an alternative method for estimating the soil properties. The aim of this study was to evaluate the results of laboratory spectrometer to estimate the concentration of Lead (Pb) and Nickel (Ni) in soils irrigated with water from treatment of urban sewage sludge of Rey city and finally to compare these results with the results of measurements of atomic absorption spectrometry. In this study, the Partial Linear Square Regression (PLSR) model was used to estimate the concentration of heavy metals and Residual Mean Square Error (RMSE) was used to evaluate the performance of this model. In this research, after spectral corrections related to elimination of the water absorption bands as well as elimination of the inefficient spectrum from heavy metals estimations, the methods of estimating these elements were studied through mathematical derivation of spectral values and also the acquisition of the continuum removal spectra. The results show that the estimated values from first derivate spectra are more consistent with the results of atomic absorption spectrometers.
J. Bayazzadeh, E. Sepehr, H. Momtaz,
Volume 23, Issue 2 (9-2019)
Abstract
To study the behaviour of phosphorus (P) sorption in the agricultural soils of Khoy region and the effect of long-term cultural management with the application of poultry manure on the P sorption parameters, bath experiments were carried out with 16 soil samples (8 cultivated and 8 virgin soils) and 9 initial P concentrations from 0 to 30 mg L-1 in 0.01M CaCl2 as a background solution. After equilibrium, the remaining amount of P in solution was measured and the experimental sorption data were fitted to the Langmuir (R2=0.93-0.99) and Freundlich (R2=0.87-0.99) models. The results showed that P sorption was increased with enhancing the initial P concentration, eventually reaching the steady-state plateau. Based on the coefficient of determination (R2) and the standard error of estimate (SE), both isotherms models, Langmuir and Freundlich, showed a relatively good fit to the experimental data. The maximum mono layer sorption of Langmuir (qmax) varied from 233 to 486 and from 340 to540 mg kg-1, and the energy parameter of Langmuir (KL) ranged from 0.12 to 0.50 and from 0.22 to 0.71 for the cultivated and virgin soils, respectively. Freundlich sorption capacity (KF) and intensity (n) parameters showed the same trends and KF varied from 36.4 to 123 and 59.3 to 145.2; also n varied from 1.18 to 1.50 and 1.47 to 1.71 in the cultivated and virgin soils, respectively. Consequently, all sorption parameters and the buffering indices showed a decreasing trend in the cultivated soils, as compared to the corresponding virgin soils and the cultural and fertilization management; especially, the application of the poultry manure in this region reduced phosphorus sorption by soil and then increased phosphorus availability to plants. Hence, less fertilizer would be needed to maintain a favourable P concentration in the soil solution for the optimum plant growth.
S. Z. Kiani Harcheghani, A. R. Hosseinpur, H. R. Motaghian,
Volume 23, Issue 2 (9-2019)
Abstract
Adsorption is one of the most important processes controlling the concentration of zinc (Zn) in the soil solution. The presence of nutrient anions in the solution can affect Zn2+ adsorption. In this study, the effect of orthophosphate, nitrate and chloride anions on the Zn2+ adsorption in five calcareous soil samples of Chaharmahal-va-Bakhtiari province was investigated. In order to study the Zn adsorption isotherms, solutions containing 25, 50, 75, 100, 150 and 200 mg/L Zn of ZnSO4 source were used in KH2PO4, KNO3 and KCl electrolytes (electrolytes concentration equal to 50 mM). The Freundlich, Langmuir, and linear equations were used to investigate the ability to describe the Zn adsorption. Based on the results, the Freundlich and Langmuir equations could describe the Zn adsorption. The results of this study showed that Zn in the presence of orthophosphate anion had the maximum adsorption capacity and an adsorption intensity higher than that of chloride and nitrate anions; meanwhile, in comparison with nitrate and orthophosphate anions, adsorption energy (k), maximum buffering capacity (MBC), and distribution coefficient (kf) in the presence of chloride anion were higher (p< 0.05). The results of this study, therefore, showed that in the presence of anion orthophosphate, Zn adsorbed more intensity and strongly, while adsorption energy was less than the presence of the other two anions. Therefore, it could be concluded that Zn and phosphate fertilizers should not be applied together in the soil.
R. Torki Harchegani, N. Mirghaffari, M. Soleimani Aminabadi,
Volume 23, Issue 2 (9-2019)
Abstract
Fruits and citrus wastes are generated in the food industry in large quantities. Their management in Iran, as one of the major hubs of fruits and citrus production, is of great importance. In this study, the biochar samples were prepared from pomegranate, orange and lemon peel waste produced in a juice factory using the pyrolysis process in the range of 400-500 °C; then their efficiency for zinc adsorption from an aqueous solution was investigated. The kinetic and isotherm data of zinc adsorption were fitted by the linear and nonlinear forms of the Langmuir and Frendlich isotherm models and the first-order and second-order pseudo-kinetics models. The results showed that under the experimental conditions applied, the maximum amount of zinc absorption by biochars derived from pomegranate, orange and lemon peel was 2.42, 1.83 and 3.17 mg/g, respectively. The results of adsorption isotherm models also showed that the use of the linear form could lead to a completely different interpretation, as compared to the original form of the model. Based on the linear forms, the Langmuir isotherm was the best; meanwhile, according to the non-linear forms, the Freundlich isotherm was the best model to describe the adsorption data. In addition, the reaction kinetics indicated that both original and linear models had the same results, and the data were better fitted by the pseudo-second order model.
M. Khamseh Mahabadi, M. Shirvani, M. R. Mosaddeghi,
Volume 24, Issue 1 (5-2020)
Abstract
Shortage of water resources and deterioration of water quality have urged the need to develop new technologies for the removal of contaminants from water. Heavy metals produced by municipal and industrial activities are among the most toxic contaminants present in the natural and waste waters. Different methods have been developed for the elimination of heavy metals from water resources and industrial waste waters. Adsorption is an effective and economic method for the water purification purposes. Nowadays, clays and natural polymers have been widely used as the adsorbents for heavy metals, due to their eco-friendly nature, natural abundance, low cost and high specific surface area. If these adsorbents are used as a hybrid material, some of their physical and chemical restrictions would be alleviated. In this study, polyacrylic acid–bentonite hybrids and natural bentonite were compared in terms of Pb adsorption in the batch and fixed-bed column systems. Besides, the effect of pH on Pb retention was investigated in both systems. The results of the batch studies showed that Langmuir and Freundlich isotherm models were appropriate in ing quilibrium Pb sorption data. Pb sorption by the sorbents was increased with the rise in solution of pH from 4 to 6, showing the greatest Pb sorption capacity at pH values of 4 (83.29 mg g-1) and 6 (103.3 mg g-1). Different indices of filtration and adsorption, including average relative effluent concentration, relative adsorption index, relative transmitted index, and filtration coefficient, were calculated from the break-through curves, indicating that the polyacrylic acid-bentonite nanocomposite was superior in the Pb sorbtion, as compared to bentonite. Also, a higher pH value resulted in the greater Pb removal from the solutions.
H. Shabani, M. A. Delavar, S. T. Fardood,
Volume 24, Issue 1 (5-2020)
Abstract
Today, to reduce the risks of contaminants, new remediation techniques have been focused on low-cost and environmentally friendly manners. Given the frequency of access, inexpensiveness and good physical and chemical properties, biochar has a high potential for the remediation of water pollutants. In this paper, the efficiency of chitosan engineered biochar (Bc-Ch) and pristine biochar (Bg-Bc) prepared from sugarcane bagasse biomass (Bg) in the Cd2+ removal in aqueous solution was investigated. To this aim, the effects of contact time, adsorbent dosage and solution pH on cadmium removal were evaluated by adsorption isotherms and Kinetic models. The results indicated that the Langmuir isotherm and the pseudo-second-order kinetic model could be well fitted with the process of cadmium biosorption. The maximum adsorption capacities of Bc-Ch, Bg-Bc and Bg ,according to Langmuir model, were found to be 32/78 mg/g, 11/57 mg/g and 2/23 mg/g, respectively. For these absorbents, the pseudo-second-order kinetic model showed the best fit to the experimental adsorption data. This study, therefore, indicated that the chitosan engineered biochar could be used as an effective, low-cost, and environmentally-friendly sorbent to remediate heavy metals contamination in the environment.
M. Jamali Jezeh, Mohammad Shayannejad, S. M Hejazi,
Volume 24, Issue 4 (2-2021)
Abstract
Water resources are limited in many areas of the world; sometimes, even these limited resources are negligently contaminated. One of the polluting factors of water is oil and its derivatives. Oil absorption using textiles is one of the common ways to separate oil from water. In this study, we used three types of textiles with different properties in order to make the filter. The experiments were performed using three different concentrations of 10, 20 and 30% oil. In this study, three types of BC, PET and PP textiles in the presence of horizontal and vertical drainages were investigated. The PET and PP textiles were made of nonwoven polyester and polypropylene fibers, respectively, and the BC textile was a two-component nonwoven textile of both polyester and polypropylene fibers that was used for the first time. Flow through the textiles was turbulent. Coefficients of flow were calculated using non-Darcy flow relations and the optimization method. The results showed that at low oil concentrations, the oil absorption had an inverse relation with the porosity and turbulent flow coefficients, but at higher concentrations, the effect of these agents was less; instead, the effect of the concentration and the intrinsic ability of the non-woven fibers was greater. The best performance was related to PP and PET with the horizontal drainage that had 95 and 91 absorption rates, respectively.
