جستجوی مقالات مرتبط با کلیدواژه « absorption » در نشریات گروه « محیط زیست »

Various pollutants such as dyes following the arrival to ecosystems lead to serious global environmental pollution. Due to global strict regulations, it is obligatory to treat the wastewaters before being discharged into the environment. One of the common, reliable and useful techniques employed for removal of synthetic dyes from industrial effluents is an adsorption process. In this study, the adsorption of crystal violet (CV) was carried out from aqueous solution PCN-224/Sepiolite composite obtained from meso-tetrakis (4-carboxyphenyl) porphyrin (TCPP) with different experimental conditions was investigated. The composition and structure of compounds were characterized by FESEM and XRD methods. The effect of various variables including dye concentration, adsorbent amount and contact time was investigated by batch method. Equilibrium data were evaluated using Langmuir, Friendlich and Tamkin isotherms. The Langmuir model best describes the CV dye adsorption, which shows that the CV dye adsorption on PCN-224/Sepiolite composite is monolayer and homogeneous. The maximum adsorption capacity under optimal conditions (adsorbent: 0.02 g, contact time: 120 min, temperature: 25°C) was 38.17 mg g-1. Kinetic data were analyzed using first-order and second-order equations. The quasi-second-order model showed the best fit for the synthetic studies (R2=0.9985), which indicates that CV adsorption is limited by the chemical adsorption process. Overall, the results show that PCN-224/Sepiolite composite can be used as an efficient adsorbent for the treatment of colored effluents.

In this study, the adsorption of methylene blue (MB) from an aqueous solution on copper-alginate (Cu(II)-A) granules containing activated carbon derived from polyethylene terephthalate (PEtAC) with different experimental conditions was investigated. The composition and structure of the granules were characterized by SEM and BET methods. The effect of various variables including dye concentration, pH, adsorbent amount, and contact time was investigated by batch method. Equilibrium data were evaluated using Langmuir, Freundlich, and Temkin isotherms. The adsorption isotherm fits well with the Langmuir model (0.9973), which shows that the MB dye adsorption on the granules is homogeneous. The maximum adsorption capacity under optimal conditions for the removal of MB was 86.96 mg/g. Kinetic data were analyzed using the first-order and second-order Lagergren equations. The quasi-second-order model showed the best fit for the synthetic studies (R2 = 0.9997). In addition, no obvious decrease was observed after up to five adsorption cycles, indicating that the PETAC/Cu (II) -A adsorbent has good stability and reusability. Overall, the results show that the prepared granules can be used an am efficient adsorbent for the treatment of colored effluents.

Phytoremediation can be one of the most promising techniques for elimination of pollutants from water and soil and environmental management. Through absorption and desorption processes, we can determine the level of maintenance for cations and anions. Based on transition factor of elements it is possible to specify that elements like Barium and Lithium have the least and elements like Cadmium and Boron have the highest accumulation. Soil pH also affects the level of availability and mobility of elements by controlling solubility of soil organic matters and it is in direct relationship with oxidation and reduction conditions. Absorption of ions by plant roots can be both passive (in direction of diffusion gradient) and active (against diffusion gradient using energy) processes. Phytoremediation is accomplished in four states including 1) phytostabilization and deposition of pollutants in the root, 2) phytoextraction that can be divided into two categories: continuous that requires the use of plants throughout their lifetime and induced by addition of accelerants or chelators to the soil, 3) phytovolatilization and transfer of contaminants from the root to leaves and the atmosphere and 4) phytofiltration to remove contaminants from water. For instance, to remove Arsenic, Cadmium (Zinc), Chromium, Mercury, Nickel, Lead, and Selenium plants such as P. vittata, T. caerulescens, Betula sp. tree, Amanita muscaria, Alyssum lesbiacum, Arabidopsis sp., and B. juncea could be used respectively.

The importance of producing aquaculture feeds which is water stable, particularly for crustacean use, feeding efficiency and reducing FCR and obtaining high production, has been mentioned. Since, many different substances chemicals and neutral have been used for increasing the water stability of aquaculture diets. Till now chemical ones such as Poly Sorbate, Carbapol, Poly Methyl Carbamide or Basfin (a kind of polymer of urea formaldohyde), Bentonites and … were used which is not towards on security policy of feeding. In this project, the aim is using Sargassum ilicifolium as a marine brown seaweed which is abundant in coast of Iranian south beaches as binder in zero, 2 and 5% of shrimp feed pellete comparing to chemical binder poly Sorbate used in control feed showed water stability and water absorbtion of pellet with 5% seaweed, higher than poly Sorbate treatment, statistically and made better texture, color, taste and scent feed for shrimp culture.

The hexavalent chromium is one of the toxic and soluble heavy metals, which is absorbed and stored in human body through the digestive system and skin. Therefore, the aim of this study was to adsorb the hexavalent chromium from aqueous media using continuous flow fixed bed of pine fruit. The adsorbent was prepared in laboratory scale and pulverized by standard ASTM sieve (100 mesh). Stock solution of chromium was prepared using potassium dichromate and the unknown concentration of hexavalent chromium was determined using atomic absorption spectrometry. In order to study the behavior of the sorbent in the fixed-bed column, we used glass column with the length of 25 cm and diameter of 2.5 cm. The effect of initial concentration of chromium and flow rate were examined. Test results showed that the maximum uptake of Cr(VI) obtained was 38.748 mg/g in a flow rate of 12 ml/min and initial concentration of 0.11 mg/l. According to the obtained results, the total amount of chromium absorbed and the adsorption capacity of the column decreased by increasing the concentration of initial chromium concentration. The maximum adsorption of Cr(VI) using the pine fruit powder achieved at flowrate of 4 ml/min and initial concentration of adsorbent of 0.15 mg/l. our findings confirms the capability of pine fruit powder application as an effective and cheap method for the removal of Cr(VI) from polluted effluents.

Heavy metals such as Cadmium are created by major urban, industrial and agricultural activities and cause pollution. According to increasing need to forestry in Iran, conducting a comprehensive research on fast-growing Platanus orientalisspecies and its role in absorbing heavy metals like Cadmium is necessary. For this purpose, the leaves and stems of plantain and soil samples from the downtown of Tehran. Leaves and stems of plantain and soil samples outside of Tehran as controls were selected randomly and were then harvested. Shoot dry weight and accumulation of cadmium in the plant was tested. The results showed that the concentration of cadmium, shoot dry weight was significantly reduced, yet significant differences between shoot dry weight was observed in the control area and the downtown area. The results showed that the concentration of cadmium, shoot dry weight was significantly reduced, yet significant differences between shoot dry weight was observed in the control area and downtown area of Tehran. The concentration of cadmium in leaves and stems in the control area with the downtown area has significant difference at 95 percent.

Bio-absorption is presented as an alternative to traditional physicochemical means for removing toxic metals from ground water and wastewater. In this research 99 bacterial strains were isolated from three wastewater samples from one of Iran petrochemical industries. Examination of these isolated for Pb2+ tolerance were carried out by using PYT agar medium containing different concentrations of Pb (NO3)2 from 4 to 15 mM. The isolated KAH1, KAH2 and KAH3, had tolerance to Pb 15, 6.5 and 6.5 mM respectively. These high tolerant strains were selected and their ability of lead bio-absorption, were investigated by atomic absorption spectrophotometer. The highest ability was observed in the strain KAH1 and this strain decreased Pb concentration from 80 mg/l to 44.4 and 48.2 mg/l after 48 and 96 hours incubation, respectively. The results of the experiments showed that bio-absorption was affected by the initial pH of the medium, initial metal ion and exposure time. According to the morphological, physiological and biochemical characterizations of the strain with that of valid strains, the strain was tentatively identified as Bacillus sp. strain KAH1. The maximum Lead bio-absorption capacity of KAH1 isolate was determined to be 48.25 mg/g (97.67%) at pH 4.0 with 150 mg/l concentration in 4 hours equilibrium time.

Development of electroplated coated sheets، such as tin coat، has resulted in the formation of effluents with various contents، one of which is phenol sulfonic acid (PSA)، which is as electrolyte in these industries and، because of its acidity and having a phenolic cycle، has been identified as a well-known environmental pollutant. In this research، to treating the sewage containing this combination، three methods of coagulation and flocculation، absorption (using GAC) ad reverse osmosis were used. In the coagulation and flocculation method، three coagulants، i. e. alum، ferrous sulfate and chloroferric along with lime (as coagulant) were used. In the best conditions، the material mentioned above shows the efficiencies of %43. 4، %36 and %32. 7، respectively. In the second method، PSA treat ability by the absorption system (using GAC) was examined in different PSA concentrations. Subsequent studies indicated optimum activated carbon quantity for the treating in question to be 163 lit/kg، in total yielding the efficiency of %90. In the PSA treat ability method، two different concentrations of this material، i. e. 200 mg/lit and 25 mg/lit were used by the R. O. system and، in one continuous exploitation mode، efficiencies of %99. 9 and %100 were obtained، respectively.