سینتیک جذب

Powdered rock phosphate may have the potential of soluble phosphate sorption because its particles are small.  Phosphorus (P) sorption-desorption behavior and sorption kinetics were studied on four different fine powdered phosphate rocks (PPR), from Esfordi, Chadormalu and Yasuj mines. Sorption isotherms were evaluated by equilibrating 1 g PPR with 20 ml CaCl2- 0.01 M containing 10, 50, 100, 200, 400, 600, 800 and 1000 mg P L-1, as KH2PO4 in duplicates. Consequently, P release was studied by equilibrating the samples with 20 ml 0.01 M CaCl2. FTIR analysis was conducted on the blank samples, and those equilibrated with 1000 mg P L-1. Kinetics of phosphate sorption on PPRs was evaluated with two initial P concentrations (50 and 100 mg P L-1) and contact times of 1, 2, 4, 8, 16, 24, and 48 h with 0.01 M CaCl2 as the background solution in duplicate. Results showed that the least P sorption was around 150, and the maximum P sorption was 12000 mg kg-1 PPRs. The highest P release was around 15% of sorbed P, and releasable P was reduced to 2-3% of sorbrd P with the increase of P sorption. P sorption data showed a good fit with Freundlich and Langmuir equations. The kinetic of P sorption showed a fast reaction that rapidly diminished soluble P. Results of the present study suggest that PPRs could reduce soluble P, which is better to be considered at different usage of PPR such as incorporation with organic wastes and its biosolubilization.

The adsorption of lead on two adsorbents, montmorillonite clay (Mt) and magnetic nano organo-composite, was investigated in this study. The magnetic nano organo-composite has been developed by modifying montmorillonite clay with the organic surfactant Hexa decyltrimethylammonium bromide and adding magnetite nano-particles (MagMt-H). X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to identify the nano organo-composite (MagMt-H). Two adsorbents were used to investigate the effect of lead initial concentration on its adsorption from aqueous solution. To comprehend the process of Pb adsorption, two adsorption isothermal models (Langmuir and Freundlich) and kinetic models (Pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion) were used. Surface adsorption in the nano organo-composite follows the isothermal models of Langmuir, as well as the pseudo-second order kinetic model, according to an examination of isothermal models and adsorption kinetics. The maximum adsorption capacity calculated from the Langmuir model at 30 °C in the nano organo -composite (73.58 mg g-1) was significantly greater than the value obtained in montmorillonite clay (49.54 mg g-1). The initial absorption rate (h) for nano organo-composite adsorbent (MagMt-H) with a value of 18.809 mg g-1min-1 compared to the montmorillonite (Mt) adsorbent with a value of 0.948 mg g-1min-1 indicates a much higher rate of lead (II) adsorption by nano organo-composite (MagMt-H). The results of this research demonstrated that the nano organo-composite (MagMt-H) was easily prepared and that new adsorption sites were created at its interface, making it extremely effective for removing lead from aqueous solutions.

Several physical, chemical, and biological methods are used to extract nitrate from water, which may be expensive and lead to the production of additional materials and toxic wastes, and are widely used.

Materials and Methods:

In this study, the ability of activated carbon as adsorbent for the removal of nitrate, ammonium and phosphate from the water were evaluated. For this purpose, the effect of contact time, initial concentration and pH on the absorption of nitrate, ammonium and phosphate on activated carbon were investigated. Absorbent surface characteristics studied by FTIR and SEM and their surface area were determined by methylene blue. Kinetics models to describe the psuedo-first-order and pseudo-second-order kinetics data and models to describe Langmuir and Freundlich isotherm adsorption data were used.

The results showed that the absorption of nitrate, ammonium and phosphate, over time, increased respectively after 60 and 120 minutes, reached its maximum. Ammonium and nitrate in activated carbon absorption maximum at pH=2 and the maximum adsorption at pH=8. By increasing the initial concentration of nitrate removal efficiency resulted in increased nitrate removal at a concentration of 100 mg/l of 86/88 percent and the highest removal efficiency of ammonia at a concentration of 5 mg/l of 92% and maximum removal of phosphate at a concentration of 7 mg/l 77 percent. According to the obtained results, the studied activated carbon had a high ability to remove nitrate, ammonium and phosphate pollutants.

 Phosphorus is an essential soil nutrient that plays key roles in plant growth and development. Limited availability of P is the main constraint for crop production in many soils. Long-term phosphate fertilizers application in agricultural areas to increase the physiological efficiency of crops can lead to a significant P accumulation. The process of P fixation or sorption includes precipitation and adsorption onto mineral and organic surfaces. Various factors such as clay content, organic matter, exchangeable Al, Fe, Ca content and pH soil affect P sorption capacity. In order to achieve the proper management of P fertilization, it is necessary to understand the mechanism of the sorption process and the contributing factors, as well as how to influence these factors. Qazvin plain is one of the most important agricultural plains in Iran, playing a pivotal role in maintaining national food security. Cultivating crops such as wheat, barley, alfalfa and corn in different areas of this plain is widespread. Therefore, high amounts of phosphate fertilizers are applied in this plain every year. In this study, the kinetic and equilibrium adsorption of P in a heavy textured agricultural soil sample in Qazvin plain were investigated under the influence of some different environmental parameters.

In order to conduct the kinetic adsorption experiment, one gram soil samples were placed in the shaker in contact with 25 ml of 0.01 M CaCl2 solution containing 20 mg P l-1. Time intervals were 0.17, 0.5, 1, 2, 4, 8, 16, 24, 48 and 72 hours. The effects of temperature (12, 25, 38 °C), salinity (0, 8.96, 17.02, 32.09, 46.25 dS m-1), pH (2.5, 3.5, 5.36, 7.5, 9.5, 11.5) and the type of background solution (distilled water and 0.01 M CaCl2 solution) were also investigated on P equilibrium adsorption. In the equilibrium batch experiments, the soil samples were placed in contact with the background solutions containing 0, 15, 20, 30, 50, 80 and 100 mg P l-1 (ratio 1:25) for 24 hours. The concentration of P in the samples was determined by a spectrophotometer after passing through the filter. The amount of P adsorption to each soil sample was then calculated based on the concentrations. The experiments were carried out in the factorial and completely randomized designs with three replications for each treatment. Using CurveExpert 1.4 software, the Langmuir and Freundlich isotherms, as well as the pseudo-first-order, pseudo-second-order, the Elovich and Intra-particle diffusion models were fitted to the obtained laboratory data. Statistical analysis of experimental data was done based on the Tukey test at 5% level using Minitab software. The thermodynamics of P adsorption was also determined by examining parameters of the Gibbs free energy, enthalpy and entropy changes.

 According to the results, the highest amount of adsorption occurred in the first 8 hours of soil contact with P solution, and approximate time of achieving the equilibrium conditions was 24 to 48 hours. The process of P adsorption onto soil particles consisted of two fast and slow stages until the equilibrium was reached. The kinetic adsorption properties of the studied soil was best described by the Elovich equation (r2=0.964). The Freundlich model showed better fit than the Langmuir equation to the equilibrium data. The effects of all four parameters of temperature, salinity, pH and background electrolyte solution on the P equilibrium adsorption were significant. By changing the temperature from 25 to 38 °C, qm (Langmuir coefficient) was 2.1 times. It was also 7.5 times under the conditions of using CaCl2 solution instead of distilled water. Increasing pH caused an increase in adsorption rate and the highest amount of adsorption changes occurred in the pH varying between 5.36 and 7.5. However, the highest and lowest P adsorption percentage with the values of 45 and 37% were related to zero and 46.25 dS m-1 salinity, respectively. The results also indicated that the sorption process was endothermic and spontaneous.

 Adjusting and controlling the studied parameters in the soil during the application of phosphate fertilizers can optimize P use efficiency and increase crop yield in the studied area. Based on the results of the present study, it is recommended to add sulfur, ammonium sulfate, ammonium nitrate fertilizers and organic compounds to the studied calcareous soil with high pH and low salinity. Application of this method can reduce soil pH, which leads to a decreased P sorption onto the soil particles and an enhanced P availability for plants. Adjusting the P fertilization time with the crop growth and uptake is also recommended due to the high adsorption of P onto the soil particles in a short period of time.

Recently, the influx of dyes into water resources has disrupted the natural order of ecologists due to their toxicity to biodiversity. In this study, activated carbon prepared from rice straw was synthesized with potassium hydroxide solution in ratios of 1: 3 and 1: 2 at temperatures of 800 °C and 900 °C, and it was used to absorb reactive yellow 145 dye prepared in a laboratory that has similar properties to the real effluent of Tehran textile industry. Then, the effect of important variables on the adsorption process such as pH (2-8), contact time (15-120 minutes), adsorbent dose (30-60 mg), dye concentration (50-200 mg/L), and temperature (15-45 °C) Checked out. The results showed that the adsorption rate was inversely related to the pH of the solution and the initial dye concentration and was directly related to the adsorbent dose, temperature, and activator saturation ratio. Among the isothermal models, the Redlich-Peterson model (R2 = 0.995) with the equilibrium adsorption capacity of 324.6 mg/g had a better agreement with the experimental adsorption results and the kinetic studies showed that the adsorption process follows the pseudo-second-order model (R2= 0.995). Thermodynamic studies also showed that the adsorption process is spontaneous and the negative slope of the Van-Hoff curve indicates that the reaction is endothermic. Due to the equilibrium time of 60 minutes in the adsorption mechanism, the synthesized adsorbent has a high rate of adsorption of reactive yellow 145 dye. The synthesized adsorbent with properties such as high specific surface area, environmentally friendly, availability of precursors, and suitable performance in dye adsorption can be used effectively in dye effluent treatment systems.

The potential of biochar for pollutant removal from aqueous solution greatly depends on biochar characteristics and its production conditions. The objective of this research was to investigate the efficiency of phosphorous adsorption from aqueous solution by date wood and sugarcane bagasse biochars produced at different pyrolysis temperature. For this purpose, biochars were produced at different temperatures (250, 400, 550 ˚C) and their physio-chemical characteristics were measured. Batch experiments performed to evaluate equilibrium and kinetics phosphate adsorption on biochars surface. Then, experimental data of phosphate adsorption were analyzed using the kinetic (Pseudo First-order, Pseudo second-order, and intra-particle diffusion) and the adsorption isotherm (Langmuir, Freundlich) models. In addition, the effect of various initial phosphate concentrations (25–500 mg L-1) and solution pH was investigated. The results indicated that the removal efficiency of sugarcane bagasse biochars was more than the date wood and increased with increasing of pyrolysis temperature. The sugarcane bagasse biochar produced at 550 ˚C, had maximum phosphorus adsorption from aqueous solution (46.94 mg g-1). Freundlich model showed the best fit for experimental data of phosphate adsorption onto biochar with R2=0.96 and RMSE=0.004. The results also revealed that Pseudo second-order kinetic model (R2 = 0.99) had the best fit for phosphate adsorption data. According to the results of this study, it can be concluded that the sugarcane bagasse biochar produced at 550 ˚C has high efficiency for removal phosphate from aqueous solution.

Nitrate is a major contaminant that is extensively found in water resources in many countries, leading to environmental problems. In this study, a batch system was used to study the removal of nitrate from aqueous solutions by micro and nanoparticles of beech leaves. After the preparation and modification of adsorbents, the effect of soluble pH, contact time, and dosage of adsorbent on nitrate adsorption were investigated. Kinetic and isotherm adsorption models were used to study the adsorption process. The results showed that the optimum pH and adsorbent dosage for nitrate removal by micro and nanoadsorbent of beech leaves were 3 and 10 g/L, respectively. Equilibrium time for micro and nanoadsorbent beech leaves was obtained 120 and 90 minutes, respectively. Among the kinetic models, Ho ̓s pseudo-second-order for the micro adsorbent and the Lagergren ̓s pseudo-first-order kinetic model for the nanoadsorbent had the best fit to the experimental data. According to the Langmuir model, the maximum adsorption capacity for nanoadsorbent beech leaves (16.69 mg/l) was higher than the micro adsorbent beech leaves (10.68 mg/l). The results showed that the nanoadsorbent of beech leaves are more capable for nitrate removal from aqueous solutions than the microadsorbrnt.

Adsorption processes are widely used by various researchers for the removal of heavy metals from wastewaters and in this type of processes, activated carbon is frequently used as an adsorbent. Many conventional methods including oxidation, coagulation, membrane filtration, reverse osmosis, adsorption, ion exchange, and precipitation have been reported in the literature to be used for the removal of cadmium metals from wastewater. These methods may be ineffective or extremely expensive especially when the wastewaters contain the relatively low concentration of metal (1–100 mg/L) dissolved in a large volume of wastewater. However, adsorption can be considered as one of the most popular methods for the removal of heavy metals from the wastewater due to its low-cost, availability, simplicity of design, and high removal efficiency. Despite its extensive usage in water and wastewater treatment industries, activated carbon remains as an expensive material. In recent years, the need for safe and economic methods for elimination of Cu from contaminated water has directed researche's interest toward the production of other low-cost adsorbents. Therefore, there is an urgent need to find out all possible sources of agro-based inexpensive adsorbents and also for studying their feasibility for the removal of Cu. In this study, the possibility of the utilization of Phragmites australis and sugarcane straw for Cu adsorption was investigated.
The Phragmites australis plant and sugarcane straw were obtained from Khuzestan Province, southwest Iran. The collected materials were washed with double distilled water and then were used as dry Phragmites and sugarcane straw. The size of microparticles was examined by sieving with a 200 mesh-number sieve. Surface area and surface morphology of the Phragmites australis and sugarcane straw adsorbents were investigated by methylene blue method, scanning electron microscope (SEM), and Fourier-transform infrared spectra (FTIR). FTIR study was carried out to understand surface properties and available functional groups involved in adsorption mechanism.
All solutions for the adsorption and subsequent analysis were prepared by diluting the prepared stock solution. The initial pH of the Cd solution was changed by adding 0.1 N HCl or 0.1 N NaOH solutions as required. The adsorption experiments were conducted via batch process. The effects of experimental parameters such as initial pH, equilibrium contact time, adsorbent dosage, and initial Cu ion concentration on the adsorption process were investigated. Pseudo-first-order and second-order kinetic models were based on the assumption of physisorption and chemisorption process, respectively. Intraparticle diffusion in liquid-porous solid was explained by surface diffusion, pore volume diffusion, or both of the processes. Diffusion models were also employed to explain the Cd adsorption process. Three main steps are involved in the solid–liquid sorption process occurred between the metal ions and the adsorbent (a) the metal ions are transferred from the bulk solution to the external surface of the adsorbent; this is known as film diffusion, (b) the metal ions are transferred within the pores of the adsorbent; this is known as intraparticle diffusion, occurring either as pore diffusion or as a solid surface diffusion mechanism, (c) the active sites on the surface of the adsorbent capture the metal ions. The FTIR study of fresh adsorbent was carried out to identify the function groups effective in the adsorption process. The results of FTIR indicated the wave numbers for different functional groups present in adsorbents. Aliphatic C–H and C–O stretching may be responsible for Cd adsorption onto P. Australis and sugarcane straw as wave number shifts from 2,918.55 to 2,913.74 cm−1 and 1,058.08 to 1,035.36 cm−1, respectively.
The Aliphatic C–H and C–O can show cadmium adsorption ability by studied adsorbents.
Hence, considering the results of FTIR, it was expected that P. Australis and sugarcane straw play a major role in Cd absorption. The results showed that the optimum pH was equal to 7 as the equilibrium time were 30 and 60 min for Phragmites australis and sugarcane straw, respectively. For the two sorbents, as the adsorbent dose increased from 0.1g to 2g, the removal percentage became 93.55% at 0.1g for sugarcane straw and 87.34% at 0.3g for Phragmites australis; however, the other values remained almost constant with the changes in adsorbent dosage, ranging from 0.1g and 0.3 to 2g. With the increase in Cu concentrations (5, 10, 20, 30 and40 mg/L) in Phragmites australis and sugarcane straw adsorbents, percentage removal decreased from 88.9% to 42.5% and 93.34% to 89.8%, respectively. The adsorption kinetics of Cu ions onto Phragmites australis and sugarcane straw was described successfully by pseudo-first-order model. Also, the adsorption behavior of Cu ions fitted Langmuir isotherm. The results of the present study indicated that Phragmites australis and sugarcane straw can be used to remove Cu ions during water treatment process. Compared with Phragmites australis adsorbent, sugarcane straw showed greater capability of Cu adsorption.

Despite the increase in population and the acute water shortage in recent years, reuse of agricultural waste has been considered as a solution. Due to the presence of contaminants in agricultural waste, attention to environmental issues and their impact on product quality is important. Phosphorus is one of the pollutants from agricultural waste that its unauthorized causes degrading aquatic ecosystems, reducing the quality of water resources and utrification. In the present study, trending of phosphorus removal by limestone and effecting of some factors such as particle size, temperature, pH on phosphorus removal and effecting of hydraulic e of flow on the adsorption isotherm was studied. In this regard, the absorption kinetics experiments on limestone mining Langmuir and Freundlich adsorption isotherm equation based on laboratory scale and physical model of drain channel was performed to investigate the effect of hydraulic flow drainage on the adsorption isotherm. Kinetic experiments showed that the rate of phosphorus removal by limestone was fixed after 30 hours. Two sizes of limestone, there was no significant difference in the percentage of phosphorus removal. Changes lead to a decrease in pH from 2 to 6 percent phosphorus removal was increased from 6 to 11 showed increased removal rate. Optimal pH for phosphorus removal was obtained for alkaline limestone. Increasing the temperature from 22 to 30 ° C was followed by a downward trend of phosphorus removal. Check isotherm, the Freundlich equation by limestone showed good agreement. Statistical comparison of adsorption isotherm and the physical model, the experimental results showed a statistically significant and did not stop.

The aim of this study is the investigation of nitrate removal from aqueous solution using quartz sand – supported zero valent iron nano particles (Sa-Fe0). The synthesis of Sa-Fe0 was based on the reduction of ferrous iron with borohydride, in which quartz sand acted as a porous-based support material. The structure of adsorbent was characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET-N2) analysis. The SEM images revealed that nano zero valent iron particles (nZVI) immobilized on Sa-Fe0 were spherical and clearly discrete and uniformly dispersed on the surface of the stabilizer without any obvious aggregation. In the batch mode adsorption studies, the effects of the contact time, initial nitrate concentration of solution, sorbent dosage,temperature and initial pH on the nitrate adsorption by the Sa-Fe0 have been studied. The adsorption capacity decreased with increasing the Sa-Fe0 dosage and initial pH value of the solution but increased with the increase in the temperature and initial concentration of nitrate. Removal of nitrate using Sa-Fe0 was in accordance with the pseudo first order kinetic model. The initial phase with the rapid rise of the adsorption rate was about 8h and the removal efficincy in this time interval was about 85% for the initial nitrate concentrations of 100 mg/L. The equilibrium data fitted well to the Langmuir model. The maximum adsorption capacity of Sa-Fe0 for nitrate was 20.833.

Existence of acid humic in water resources is undesirable and causes carcinogenic component in disinfection process due to reaction with chlorine. Due to their cost-effectiveness and higher physical resistance than activated carbon, natural zeloites are used for removing various pollutants. . In the present study, Iranian natural zeolite modified with cetylpyridinium bromide (CPB) was investigated for removing humic acid (HA) in an aqueous solution. In addition, common isotherms and kinetics in water and wastewater are studied. The effects of parameters such as initial humic acid viscosity, adsorbed dose. pH, and contact time with modified zeolite on humic acid adsorption were investigated. Findings indicated that increased contact time and adosorbed dose increases the efficiency of humic acid removal and increased pH decreases the removal efficiency of modified zeolite. The initial pH of the HA solution strongly affected the efficiency of SMZ for HA removal in an aqueous solution. The optimum initial pH values were in acidic levels for adsorption of the HA on SMZ. Furthermore, Langmuir isotherm and second-order kinetics were found to be the best models for explaining humic acid adsorption reactions on modified zeolite adsorbent.. This study showed that Iranian natural zeolite modified with cetylpyridinium bromide (CPB) as a cationic surfactant is a promising adsorbent for removal of humic acid.

The limitation of fresh water resources in the most parts of the country has necessitated the use of unconventional water resources. Wastewater is one of these unconventional sources, however the environmental impacts of wastewater reuse should be carfully considered. The present study aimed to examine the effect of the rubber powder to absorb the heavy metals of lead, zinc and manganese in laboratory scale. The batch tests to evaluate the absorption equilibrium time were conducted in constant pH of 5.5 and the soluble metal concentration equal to 100 mg per liter. The adsorption kinetic results showed, the removal efficiency of lead, zinc and manganese were 67.2, 74.3 and 39.9 percent, respectively. Time to reach equilibrium for zinc and manganese were 180 and 120 minutes, respectively. But lead does not reach equilibrium during the 180 minutes of testing time. Also, the adsorption isotherms tests were performed for these metals and the data were fitted with the linear, Langmuir and Freundlich models. The results showed that the Freundlich adsorption model with regression coefficient equal to 99 percent was the best compliance with the laboratory results.