Dynamic modeling and simulation of fixed bed adsorption process was carried out by explaining the behavior of breakthrough curve parameter. Adsorption of sulfur compound, present in road fuel, has posed a great challenge. A model of fixed bed adsorption of benzothiophene from fuel was formulated with non-ideal plug flow behavior and considered velocity variation along a column. The model was solved using the Method of Line (MOL) numerical solution-a technique for solving PDEs-in which all but one dimension is discretized; as a result, the set of ODEs can be solved by highly accurate methods and low computational cost. The effects of various factors, such as flow rate (4-10 cc/min), inlet concentration (125-500 ppm), and bed height (10-40 cm), on adsorption performance, were investigated. Specific characteristics, typical of breakthrough curve, were analyzed in terms of degree of bed utilization, break point time, film mass transfer coefficient, and height of adsorption zone. High bed column, high flow rate, and high inlet concentration happened to be better conditions, in term of used overall bed capacity percent for adsorption system.

Organic manures are the source of many pathogenic bacteria which could be dangerous for human health. In this study, the effects of soil texture and structure on transmitting and filtering of manure-borne Escherichia Coli were investigated. The intact soil samples (25 cm in height and 16 cm in diameter) were taken from a sandy clay loam soil and a loamy sand soil. Three manures including: cow manure, poultry manure and sewage sludge was applied on the surface of the soil cores at the rate of 10 Mg ha-1 on dry basis. With controlled steady-state unsaturated water flow, the influent and effluent concentration of Escherichia Coli were determined vs. time up to four pore volumes (PV). In spite of greater adsorptive sites of sandy clay loam soil, more bacteria have been transmitted and polluted the effluent of the soil. The loamy sand soil filtered more Escherichia Coli compared with the sandy clay loam soil. The effluent contamination of poultry manure-treated columns was greater than the cow manure and that of treated sewage sludge. In the majority of the columns, the difference between cow manure and sewage sludge was negligible. The filtration of Escherichia Coli in loamy sand soil was greater due to weaker structure and discontinuity of pores which are responsible for Physical filtering. In sandy clay loam soil, the stable structure and preferential pathways are believed to cause funneling of the bacteria towards the bottom of the columns and the early appearance of Escherichia Coli in the drain water. The results demonstrated the importance of soil structure and preferential (macroporous) flow in bacteria transport which could diminish the impacts of soil texture and adsorptive sites on the transmission mechanisms.

In this research, the adsorption of sulfur compounds from propane and butane streams (real gas from Assaluyeh) using faujasite-type zeolite in constant pressure and temperature was studied. Zeolite NaY was synthesized in order to specify the effect of NaY size on adsorption of sulfur compounds. The synthesized samples were characterized by XRD, FE-SEM and BET analyses then three different sizes of NaY zeolite (60nm, 800nm, 2400nm) were selected to specify the effect of the particle size on the sulfur compound’s removal performance. The outlet gas streams were characterized using a potentiometric method (UOP212). breakthrough curves were plotted for each stream; moreover, the breakthrough curves were modeled using BDST (bed depth service time) model and Yoon-Nelson model in order to determine the effect of adsorbent’s size, type of inlet gas and the amount of sulfur compounds on the parameters of Yoon-Nelson and BDST models. After making a comparison between the results from breakthrough modeling, it was concluded that for BDST model, decreasing the size of NaY zeolite increased the adsorption capacity index while the proportionally constant model was being decreased; however, in Yoon-Nelson model, decreasing the size of NaY zeolite increased time to %50 of breakthrough curve and decreased the proportionally constant model.

In this research paper, an experimental breakthrough curve for citric acid in an adsorption recovery process was determined by an ion-exchange resin in 20, 35, 55°C. Also, a mathematical model for breakthrough curve was presented. Among ion exchange resins that have been experienced, many weak and strong basic anionic resins are available such as, IRA-92, IRA-93, IRA-420 and IRA- 458 and all of them were experienced in this work. It was shown that IRI-93 has good performance and compatibility. To obtain concentration of citric acid in the outlet stream from the resin glass column, spectrophotometer DV-VIS, Cary 1E/ Cary 3E from Varian Company was used. The results indicated weak basic kinds are '"suitable for organic acids recovery, especially for citric acid. Also, the results showed that Amberlite IRA-93 is one of the best resins for recovery of citric acid. In the transient state adsorption, the breakthrough isothermal adsorption curve was obtained in different temperatures. Generally, although an increase in temperature causes an increase in diffusion coefficient of particles, the saturation capacity of resin (or the effective adsorption of acid in the bed) decreases. Several models in different forms, such as fractional, polynomial and exponential, were developed and with analyzing these models a new mathematical model in the form of C=at/b+c° and modified form of c at were developed for C/CF=at/b+(c/cf)n prediction of the breakthrough curve with low error. Also, if the model is to be used for the break through curve between start and terminal rapture points, the situation of fitting is in the best condition and error less than 1% could be achieved. In this way, least square method in Eviews software was applied. With using these models, the variation of similar breakthrough curves could be fitted, appropriately.

Background and Objectives: Organic matter improves the physical condition of the soil and due to the increase in water holding capacity of the soil, changes the pattern of contaminant uptake and prevents them from leaching into groundwater. Dispersion is important factor affecting soil solute transport in porous media that used in the advection-dispersion equation and it is a function of the transmission distance. The aim of this study was to investigate the effect of biochar on the leaching process of deltamethrin in soil columns. During this study, the breakthrough curve and dispersion coefficient of this pesticide in vertical soil columns were determined. Materials and Methods: This study was carried out in soil columns with a height of 15 and 30 cm and in a period of 12, 23, 56 and 112 days and including different levels of 1. 5 and 3 WP% (Weight percent) of wheat biochar and control treatment as a completely randomized factorial design. The concentration of deltamethrin used was 300 cc per thousand liters per hectare. To determine the residual concentration, the pesticide was sprayed on the surface only once with the recommended dose and according to the considered irrigation periods, the changes of the pesticide over time and at different depths of the soil columns were studied. In this study, Brigham's analytical method was used to obtain the dispersion coefficient. Analysis of variance and comparison of means in the studied treatments was performed using LSD statistical test and SAS 9. 4 software. Results: The results showed that the residual concentrations of pesticides in 1. 5 and 3% of biochar treatments compared to the control were decreased 26 and 43%, at depths of 0-15 cm and 37 and 17% at depths of 15-30 cm respectively. Based on the results, pesticide uptake and stabilization in 3% biochar treatment was more than other treatments. In the control treatment, with increasing soil depth, it was observed that the dispersion coefficient decreased, in the modified treatment with biochar 1. 5%, the dispersion increased while in the biochar 3% treatment, the dispersion coefficient decreased significantly by increasing the sample length. Deltamethrin dispersion coefficient in 15 cm columns for control, biochar 1. 5 and 3% treatments were 5. 37, 1, 3. 59 cm and in 30 cm columns 3. 91, 1. 27, 0. 92 cm was obtained, respectively. Conclusion: Biochar production is very convenient and cost-effective and is successful in restricting the movement and stabilization of pesticides in the soil and by increasing its weight percentage in the soil, due to the surface area of biochar can control the movement of pesticides.

Due to limitations of laboratory tools and difficulty in interpreting the results obtained from complex porous media such as soil, artificial porous media such as glass beads, pure sand and quartz and riverbed sand are oftenly used to investigate the transfer of nanoparticles in porous media. In this study, the effect of different flow rates on transfer of titanium dioxide nanoparticles was investigated in the undisturbed soil columns. The flow rate equal to 100, 90, 70 and 50% of the saturated hydraulic conductivity were applied on the soil columns by the peristaltic pump (BT100-1F). By measuring the breakthrough curves for each column, the parameters explaining the transfer of nanoparticles based on a one-site sorption model, one-kinetic site sorption model, and a two-kinetic site sorption model were determined. The results indicate by increasing the flow rate, the reltive concentration of TiO2 nanoparticles (C/Co) in the soil column increases from 3% to 28%. Among the three studied models, the two-kinetic site sorption model which consider the physical straining mechanism based on the particle size and porosity of the porous medium, the function of saturation of the porous media particles with nanoparticles and the physical straining function considering changes of this mechanism with distance, shows the best fit (R2>%90) for estimation of the nanoparticles transfer in the soil column.

Water and organic contaminant transport in soil porous media, particularly in light textured soils due to high transmission capacity and create a secondary sources of pollution is very important. The aim of this study was kerosene and water transport in a light texture soil system containing different treatments of montmorillonite nanoclay. For this purpose, treatments including 0, 2, 4 and 6 wt% of nano clay- sandy soil in a funnel containing filter paper based system was applied. Then kerosene and water (4 pore volumes alternatively) were passed into soils. The breakthrough curves showed that the water passes through soils was slower and gentler slope, so the volume output was lower compared to kerosene. It seems that water molecules with a diameter of less than 3.0 nm fitted well in the small spaces between the layer of nanoclay, which are held with strong hydrogen bonds. Kerosene, with a density equals 0.78, only attract surface places, therefore, pass from porous soil surface well due to having molecules with 11 to 15 carbon atoms, which are larger than the density of water. In both fluids, the more percentage of nanoclay there is, the more retention of kerosene and water would be expected. The results of X-ray showed that the distance of nanoclay increased from 14.4 to 24.77 Å with addition of water.

Introduction Recently, the presence of pathogenic bacteria in the municipal water network has been observed and proven. Applying animal manure in agricultural lands with improper drainage is the main cause of this pollution. Identifying and investigating the movement of intestinal bacteria, especially E. Coli, which is the source of their distribution in most waters, agricultural activities, and urban sewage, is considered one of the appropriate and necessary ways to preserve drinking water resources Some of the soil characteristics that affect the movement of bacteria are: particle size distribution, structure, porosity and apparent density of the soil, in addition, plant roots and pores and cracks are caused by root activity. Plants and animals in the soil create fast water passages to facilitate the transport of pollutants. These routes are called preferential pathways and the flow is named preferential flow. Therefore, considering the environmental importance of the movement of E. Coli bacteria as a pathogen in the soil, so far, most of the studies on the transfer of bacteria without the presence of plants and its effect on the release of bacteria have been investigated. Therefore, this research aims to investigate bacteria transport from cow manure in four granulation levels in the presence of grass plants. Materials and Methods This study was conducted in the greenhouse of Shahrekord University to investigate the transport of E. Coli bacteria caused by the addition of cow manure in four levels of granular size in the soil profile with/without grass cultivation. Some physical and chemical characteristics of the soil were measured by usual methods. In this research, cow manure with a scale of 36 tons per hectare with four granulation levels of 0.25, 0.5, one, and two mm was used as a source of bacteria. The grass was prepared at a height of five cm and was placed on the surface of the soil columns for 14 days to stabilize the roots. The used columns were 24, made of polyethylene and in the form of a cylinder with an external diameter of 160 and a height of 350 mm. First, the soil was passed through a two mm sieve and then the columns were filled with soil up to a height of 300 mm. The treatments included grass cultivation in two levels (without cultivation and with grass cultivation) and the size of manure particles in four levels (0.25, 0.5, one, and two mm). The columns were irrigated with the usual irrigation schedule (once every two days) with the same volume and flow in the surface method until the field capacity was reached. After seven irrigations, the transfer test was performed. The transfer test with municipal water in the columns continued up to seven pore volumes (PV) and sampling was carried out in pore water volumes of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8,0.9, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.5 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 and 7 were done for each treatment. After the end of the transfer test, to measure the population of bacteria in the soil profile, samples were taken from every five cm of soil depth. In this study, the live count method was used to measure the bacterial population. Results and Discussion There is no significant difference in the relative concentration curve of bacteria in the state of cultivation and without the cultivation of grass. It can be said that the effect of the cultivation of grass in the transfer of bacteria was not observed for 2 mm fertilizer particles, but the shape of the curves has changed in diameters less than 2 mm. It can be stated that in all treatments, the larger the amount of fertilizer, the higher the relative concentration of bacteria in low PVs. In other words, by washing the bacteria from the surface of the fertilizer particles, they are freed and enter the soil, and by continuing the washing, the maximum relative concentration of bacteria in the treatments without grass cultivation and in the diameters of 2.0, 1.0, 0.5 and 0.25, respectively, is 0.6. 0.7, 0.6, and 0.9 times the pore volume occurred. These values were equal to 0.7, 1.0, 0.9, and 1.0 times the pore volume in the treatments with grass cultivation, respectively. After this period, the concentration of released bacteria decreased sharply. The results showed that the presence of grass in the soil for all diameters of fertilizer, except the diameter of 0.25 mm, caused the peak of the breakthrough curve to be delayed. In addition, it is observed that the relative concentration of bacteria in the treatments with grass cultivation has decreased with a gentler slope compared to the treatments without grass cultivation. The amount of zero torque in the treatments with grass cultivation in all fertilizer sizes was more than the same treatment as compared to the conditions without cultivation, and this indicates that the presence of grass caused more bacteria to escape from the drainage of the columns. For fertilizers with particle sizes of 0.25, 0.5, and 2.0 mm in the condition of no cultivation, there is not much difference in the delay factor with the similar treatment in the condition of grass cultivation, but in the treatment with the particle size of one mm in the condition of grass cultivation, the rate of fertilization is delayed. has had a significant increase. Conclusions The results showed that for two mm fertilizer particles, the amount of bacteria transfer increased in the case of no grass cultivation compared to the one, 0.5, and 0.25 mm treatments. The maximum relative concentration of bacteria in the breakthrough curve for 0.25 mm fertilizer particles was lower between one and two mm compared to larger fertilizer particles and was observed with a delay compared to coarser fertilizer particles. In the treatment without grass cultivation, the maximum concentration per fertilizer with the particle size of 0.25 mm was observed at PV 0.9, while in the treatment with the particle size of two, one, and 0.5 mm, the maximum relative concentration of bacteria was 6.6, respectively. About 0.0, 0.7, and 0.6 times the pore volume occurred. In the presence of grass in the soil, the bacteria reached the bottom of the soil column at a faster rate. One of the causes of this phenomenon is the role of plant roots in accelerating the transfer of bacteria in the soil in such a way that the preferential flow paths created by grassroots have moved the bacteria down.

Introduction: Nowadays pollution of sand columns and water resources with hexavalent chromium is enhancing due to the increase of industrial and agricultural activities. In recent years nanoscale zerovalent iron particles (nZVIP) have been used according to special properties comprising of high surface area, high reaction sites, non-toxic, non-expensive and high potential for removal of pollutants such as hexavalent chromium from sand columns and water. The size range of Zerovalent iron nanoparticles is less than 100 nm. So they could potentially be transported into the subsurface and finally be mixed with the target pollutants. Chromium is one of the steely-grey, lustrous and toxic heavy metals with high toxicity potential. Upon chromium (VI) toxicity this element is classified as a primary contaminant. Chromium (III) compounds is not toxic and hazardous and are grouped as one of the beneficial elements for human and other animals, while the toxicity and carcinogenic properties of hexavalent chromium have been realized for a long time in all over the world. Application of polymers as nZVIP stabilizers diminishes flocculation and sedimentation of nanoparticles. So usage of such polymers may lead to decreasing of particle size, enhancing reactivity and increasing particle transport in column and continuous medium studies. The objectives of this study were: (1) synthesis and characterization of different surface modified nZVIP with some polymers including Polyacrylamide (PAM) and Guar gum (GG), (2) the removal of hexavalent chromium ions from sand columns by application of different stabilized nZVIP, (3) investigation the impacts of different experimental situations on hexavalent chromium removal from sand columns including primary nZVIP dosages and primary hexavalent chromium dosages, and (4) evaluation nZVIP transportation in sand columns. Material and Methods: In this research, nZVIP were synthesized using chemical reduction of ferrous sulfate by sodium borohydride. Guar gum (GG) as a green and environmentally friendly coating and polyacrylamide (PAM) as an anionic and biodegradable polymer were applied for stabilizing of nanoparticles. Zeta potential values were determined by a ZetaPlus zeta-potential analyzer from Brookhaven Instruments Corporation and the measured values were gathered from a suspension containing 5 mg zero valent iron nanoparticles in 100 mL of 1 mM NaCl solution, at room temperature. The hydrodynamic diameter of nanoparticles was determined using a ZetaPlus zeta potential analyzer and the Brownian movement of particles was related to nanoscale zerovalent iron particles hydrodynamic diameter. The morphology of zerovalent iron nanoparticles was determined by scanning electron microscope (SEM). Furthermore, the size of the synthesized nanoparticles was considered using a transmission electron microscope (TEM) via image measuring software. Results and Discussions: The results showed by increasing of nanoparticle and hexavalent chromium dosage the removal efficiency of chromium increased and decreased from sand columns, respectively. Increasing of hexavalent chromium dosage from 40 to 80 mg/L in sand columns lead to more excessive chromium ions at sand columns and diminishing of hexavalent chromium removal efficient from sand particles. When the dosage of nanoscale zerovalent iron particles raised from 1 to 3 g/L and while the concentration of Cr (VI) was on a constant value of 100 mg/L, the effective reaction sites for hexavalent chromium removal would increase and so the removal performance would enhance according to the nanoparticle dosages. The findings of the current study also revealed when ionic strength and nZVIP dosage enhanced, the transportation of nZVIP decreased in sand columns. By enhancing the concentration of nZVIP, the surface reaction sites of nZVIP increased and hence the efficiency of chromium removal raised from sand columns. Zeta potential is a good parameter for evaluating the colloidal stability. This parameter is an index of stability that reflects the electrostatic repulsion forces between charged particles. By shifting the zeta potential values to the higher records (more negative) the magnitude of repulsion forces among the particles will increase and the stability of them will enhance as a result. In this research the achieved zeta potential records for synthesized nZVIP showed that PAM-stabilized nZVIP and non-stabilized nZVIP had the most and the least stability values respectively. Conclusion: The final results of this study revealed that increasing dosages of synthesized zerovalent iron nanoparticles enhanced the removal efficiency of nitrate and hexavalent chromium from sand columns. When dosages of Cr (VI) increased the removal efficiency of current pollutants decreased. TEM results showed the order of particle sizes were upon to the following trend: PAM-nZVIP < GG-nZVIP < Bare-nZVIP. So PAM stabilized zerovalent iron nanoparticles and the bare nanoparticles were the smallest and largest sizes of all. The efficiency of hexavalent chromium removal and nanoparticle transormation were according to the following trend: polyacrylamide (PAM)-nZVIP> Guar gum (GG)-nZVIP> Bare-nZVIP

Increased use of nitrogen fertilizers due to high dynamics of soil nitrate is a serious threat to groundwater and as a result for human health. The purpose of this study is evaluation of nitrate dispersivity values in the sandy soils of coarse, medium and fine-distance transmission at 80, 40 and 20 cm in laboratory conditions with three models including, Brigham, Fried-Combernous and CXTFIT code. For this purpose, pure potassium nitrate salt solution as sustainable contaminant under the steady regim with concentration of 160 mg/lit was added to the soil column. In order to obtain the required parameters for the three models, output nitrat concentration were measured in the different nolum porosity and breakthrough curves were plotted for each column. The results showed that in all three models with a moderate increase in transmission distance of medium and coarse sand, the amount of nitrate dispersivity increased. At various distance of transportation, dispersivity values were measured for fine sand from 0.09 to 3.06 cm, 0.23 to 1.6 cm for medium sand and 0.43 to 2.18 cm for coarse sand, respectively. But the Brigham and CXTFIT models showed that the dispersivity of fine sand increases when the distance increases. It was also found that for the fine sand with reduction of transport distance, Brigham model and CXTFIT code showed better results.