جستجوی مقالات مرتبط با کلیدواژه « adsorption isotherm » در نشریات گروه « مهندسی آب »

In this paper, the removal of nitrates from urban raw sewage (Tehran) by walnut tree sawdust using the surface absorption method was introduced as an efficient green method, and the effect of various parameters was studied. The results obtained from Langmuir isotherms R2=0.9951 and Freundlich R2 = 0.9936 indicated better absorption in low concentrations, which follows the Langmuir model. To complete the present studies, the adsorption diagram, the effect of pH, thermodynamic and kinetic studies were investigated. Kinetic studies showed that the surface adsorption process of nitrate by walnut tree sawdust follows the pseudo-first order kinetic. The absorption capacity obtained from this equation was 34.2 mg/g (its experimental value of 32 mg/g). The results showed that this process is controlled by reversible physical adsorption. According to the FT-IR spectrum of the absorbent, the phenomenon of nitrate absorption takes place with the help of the cellulose structure of the absorbent. The use of walnut tree sawdust (micro size) without chemical modification as a natural, green, environmentally friendly, efficient, and effective adsorbent in removing nitrates from the raw sewage of Tehran city was one of the important features of this research.

The problem of toxic-metal-contaminated water has become a great environmental concern and presents significant hazards to the public health and economy. In this study, drinking water treatment sludge was activated and used as an efficient, cheap and cost effective sorbent in the removal of Pb (II) ion from water samples. The prepared material was characterized by Fourier transfer infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), surface analysis (BET method) and X-ray fluorescence (XRF) analysis. The effects of various parameters such as the solution pH, adsorption time, adsorbent dosage, and initial metal ion concentration upon adsorption were investigated. Equilibrium isotherm studies were carried out with different initial concentrations of Pb (II), and three models (Langmuir, Freundlich and Temkin isotherms) were utilized to analyze the equilibrium adsorption data. The best adsorption performance was obtained at the following conditions: pH of sample, 7.5; contact time, 15 min; adsorbent dosage, 0.3 g; intitial concentration of Pb (II), 20 mg/L; agitation speed, 200 rpm. The results revealed that the adsorption process obeyed the Langmuir model, with the maximum monolayer capacity (qmax) and the Langmuir constant (KL) calculated as 54.9 mg/g and 0.973 mg/L, respectively. Kinetic studies indicated that the adsorption process followed a pseudo-second-order model based on the obtained R2 values. Comparison study with the other natural adsorbents revealed that the activated sludge has the highest adsorption capacity and provides the lowest adsorption time. Desorption study exhibited that the Pb (II) ions can be desorbed from the adsorbent by 0.25 mol/L HCl solution with a recovery percentage of 98%. The results exhibited that activated sludge is an efficient and cost-effective material for the adsorption of Pb (II).

One of the hazardous compounds for humans and the environment is polycyclic aromatic hydrocarbons, which are the naphthalene of the precursor of two-ring aromatic hydrocarbons. These compounds are carcinogenic and toxic, they cause anemia and damage to the retina and are also toxic to plants and aquatic animals, these compounds have been identified as priority pollutants by the World Health Organization, yet these compounds are difficult to remove by biological methods. This study was performed in batch in vitro where the effect of parameters such as retention time 15, 30, 45, 60, 90 and 120 minutes, concentration of multi-walled carbon nanotubes and activated carbon from coconut skin 0.1, 0.25, 0.5, 0.75, 1 and 2 g/L), solution concentration 1, 5, 10, 15, 20, 50 and 100 mg/L and pH 3, 4, 5, 6, 7 and 8 the concentration of 10 mg/L naphthalene solution in naphthalene removal was investigated. Experimental data of adsorption equilibrium with different Langmuir and Freundlich adsorption isotherm models are evaluated and analyzed with adsorption kinetics by comparing R2 coefficient of analysis and analyzed by excel software. Maximum naphthalene adsorption on both carbon nanotubes and activated carbon nanotube adsorbent at initial concentration of 10 mg/L naphthalene and adsorbent dose equal to 0.75 g/L at pH=7 is an appropriate time to achieve maximum naphthalene adsorption;the balance mode is 90 minutes. The adsorption mechanism is consistent in both adsorbents of Langmuir adsorption isotherm and their coefficient of determination in carbon nanotubes is (R²=0.9589) and in coconut shell activated carbon (R²=0.9319). and both adsorbents are from adsorption synthetics second-degree followers. Multiwalled carbon nanotubes and activated carbon from coconut skin due to their small size, high cross-sectional area as a result of high reactivity, as an adsorbent for removal of naphthalene from water. And the nanotube has a higher absorption than activated carbon from the coconut skin, so it is considered as a better adsorbent because of its affordability and availability.

Dyes are one of the most important existing pollutants in textile industrial wastewater. They are often toxic, carcinogenic, teratogenic, and non-biodegredable. So the aim of this study was synthesis Fe2O3@SiO2 nanoparticle and using it as adsorbent for the removal of acid blue 92 from aqueous solutions. In this study, the electrochemical method for synthesis nanoparticle was used and characteristics of nanoparticle were analyzed by SEM (Scanning electron microscopy) technique. In this study, the effect of the pH (2-11), contact time (20-150 min), nanoparticle dosage (0.02-0.14g/L) and concentration of dye (20-120 mg/L) was investigated by one factor at the time method and then was optimized. The pH equal to 2, contact time of 40 min, and absorbent of 0.08 g/l was obtained as experimental data correlate to the pseudo-second order kinetic (R2=0.995) and Dubinin-Radushkevich adsorption isotherm model (R2=0.989). In optimal conditions, Fe2O3@SiO2 nanoparticle has well potential to quickly and effectively remove dye and simply be separated from the solution by the magnet due to its magnetic property.

Recently the low-cost adsorbent for heavy metals removal such as Lead in recent years has been noticed by researchers. In this study, lead removal by clinoptilolite has been investigated. Non-continuous lead absorption from aqueous solution was carried out by using clinoptilolite. The zeolite characteristics were analyzed with SEM and XRD. The effect of pH variables (1, 3, 5, 7, 10), contact time (15, 30, 45, 60, 90 min), clinoptilolite adsorbent dosage (1, 3, 5, 7, 10 g) and lead concentrations (10, 20, 40, 50, 60, 70, 80 & 100 mg/L) were studied on lead removal efficiency and adsorption isotherms and kinetics in constant temperature and stirrer speed of 250 rpm. According to the results, optimum conditions of lead removal by natural zeolite were pH of 8, adsorbent dosage of 5 g/L and contact time of 45 min., the highest removal efficiency of 89.6 achieved. By increasing metal concentration, the amount of removed lead was decreased while absorption capacity increased. Of the two studied models, the Langmuir isotherm had better conformity for lead adsorption (R2=0.99) than other isotherms. Also the pseudo second order kinetics model had better conformity with achieved data than other models. Results of this study indicated that natural clinoptilolite zeolite can be considered as an efficient and cost effective adsorbent for lead removal from aqueous solutions.

Dyes are a main source of pollutants in textile plant effluents. Due to their molecular structure, they are usually toxic, carcinogenous, and persistent in the environment. The aim of the present work was to explore the removal of basic blue159 (BB159) using magnetic sodium alginate hydrogel beads. Magnetic sodium alginate hydrogel beads were initially synthesized accoriodng to Rocher method using CaCl2 as a crosslink agent. Fourier transform infrared spectroscopy (FTIR) was then employed to examine the functional groups on the surface of the magnetic sodium alginate hydrogel beads. In a third stage, the magnetic properties of the beads were measured using a vibrating sample magnetometer (VSM) and the magnetic parameters were calculated. Subsequently, the effects of such parameters as adsorbent dosage, pH, initial concentration of dye, and contact time were evaluated on the BB159 removal efficiency of the adsorbent used. Finally, the Langmuir, Freundlich, Temkin, and B.E.T models were exploited to study the adsorption isotherm of BB159 onto the magnetic sodium alginate hydrogel beads. It was found that the magnetic sodium alginate beads possess both –COO and –OH groups that play important roles in the adsorption of the positively charged BB159 dye. A saturation magnetization equal to 21/8(emu/g) was obtained for the sodium alginate beads/nano Fe3O4. Results also revealed that the highest dye removal from aqueous solutions was achieved at pH=11 in 120 minutes for 9 grams of the adsorbent. The study indicated that BB159 removal using the magnetic sodium alginate hydrogel beads as the adsorbent obeys the Langmuir model. Moreover, it was shown that the efficiency of the process for BB159 removal from aqueous solutions was satisfactory (85%).

The presence of nondegradable toxic compounds such as phenol in the environment has nowadays led to many health and environmental problems. The present empirical study was conducted on the lab scale to evaluate the efficiency of Acacia tortillis pod shell as a new alternative and low cost adsorbent for removing phenol from aqueous solutions. The experiment was performed in a batch system and the effects of important operation variables including initial phenol concentrations of 0.5, 1, 2, 4, 8, 16, 32, and 64 mg/l, absorbent doses of 0.1, 0.2, 0.4, 0.8, and 1.6g/l in predetermined mesh sizes (ranging over 30-60 and 60-100), pH levels of 2, 4, 6, 8, 10, and 12, and contact times of 10, 20, 30, 40, 50, and 60 min were evaluated. Finally, the Freundlich and Langmuir adsorption isotherms were determined in order to describe the relationship between the colored solution and the absorbent. Results showed that the highest phenol absorption efficiency achieved was above 95% which was obtained with an optimum pH level of 2, an optimum absorbent dose of 0.2 g/l, and a mesh size of 60-100 for a contact time of 10 minutes and at a low pollutant concentration. Increasing phenol concentration increased its removal efficiency but this removal rate was lower at extreme concentrations. Also, the adsorption process was found to be more compatible with the Freundlich model. Based on the results obtained, the pod shells of Acacia tortillis pod shell may be claimed to be an effective, efficient, and cheap absorbent for the removal of phenol from aqueous solutions.

Water and soil pollution by heavy metals is a serious threat to environment and human health. Therefore finding an effective method for removing heavy metals from water is very important. Removal of heavy metals from water by adsorption method has increasingly received much attention in recent years because it is simple relatively low-cost and effective method. The main objective of this research is to investigate the possibility of removing Cu (II) from aqueous solution using modified tea waste with magnetite nanoparticles. Consequently، modified tea waste with magnetite nanoparticles were prepared and characterized by Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR). The effects of various parameters، such as contact time، pH، Cu concentration and adsorbent dosage were studied. The adsorption isotherm data were fitted to Langmuir and Freundlich equation. The results indicated that the sorption data can be represented by both Langmuir and Freundlich isotherm models، and the Langmuir adsorption capacity، was found to be 22. 4 mgg−1. The results indicated that Cu (II) adsorption increased with increasing solution pH. Maximum removal of Cu (II) was obtained at pH=5. 5. The results also showed the adsorption were decreased by increasing of initial Cu (II) concentration. An increase in adsorbent dosage increased the removal of Cu (II). The results also revealed that modified tea waste with magnetite nanoparticles can be an attractive option for metal removal from contaminated water.