Toktam Shahriari; Abdolreza karbassi; Maryam Shirazinejad
Abstract
Introduction: Industrial plating wastewater contains various types of detrimental heavy metals in high concentrations. One of this toxic metal is Nickel that its discharge into the surface waters and soil is considered as an environmental problem. Hence removing of this metal from wastewaters is crucial ...
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Introduction: Industrial plating wastewater contains various types of detrimental heavy metals in high concentrations. One of this toxic metal is Nickel that its discharge into the surface waters and soil is considered as an environmental problem. Hence removing of this metal from wastewaters is crucial and vital for protecting the environment and human health. Applying of nanotechnology in elimination of environmental contaminants is one of the methods which attracted a great deal of attention in recent years. In present research, nanographite was utilized as efficient adsorbent in order to remove Ni ions. Materials and methods: In order to investigate the adsorption process, nanographite with a purity of 99.9% and a specific surface area of 18-24 m2/g and a plate morphology was prepared from Pishgaman Iranian Nanomaterials Company and used as an adsorbent. Also, the wastewater used in the experiments was prepared from one of the plating workshops in Tehran, which contained 765 mg/L of nickel and a pH of about 1. The parameters of pH, time and amount of adsorbent were evaluated. In each experiment, one of the parameters was considered variable and the other two parameters were considered constant. The amount of nickel was determined before and after each test.Results and discussion: In this study, the parameters including pH, adsorption time and adsorbent dosage were investigated as effective factors on Ni adsorption process. In order to analyze the adsorption mechanism, the obtained results were examined by the Langmuir and Fruendlich isotherm models. In addition, pseudo-first-order and pseudo-second-order models were studied to investigate adsorption kinetics. According to the results, the Ni uptake by nanographite was enhanced significantly with increasing of the pH value from 5 to 7. Thus the pH of 7 was determined as optimum pH for Ni removal. Investigations also showed that increasing the time up to the first 80 minutes had a relatively good effect on nickel adsorption by the nanoparticle, and after that the adsorption almost reached equilibrium. Finally, it was observed that in a constant time, increasing the amount of adsorbent led to an increase in adsorption, and to achieve the maximum adsorption of nickel, the amount of 2g was chosen for the adsorbent. Based on the obtained results, 97.52% primary nickel was adsorbed by nanographite. Results also revealed that the data were best fitted to the Fruendlich models. After determining the amount of nickel adsorption at different times, the resulting data were analyzed by the kinetic model.Kinetic studies also indicated that the adsorption data were described well by pseudo-second-order model. Conclusion: Examining the results showed that pH plays an important role in the adsorption process and the adsorption rate increases with increasing time until the equilibrium time is reached. One of the effective factors is the amount of adsorbent, which has a direct effect on adsorption. Following the Freundlich isotherm in this research indicates that the adsorption sites in the adsorbent have different energies. Also, the pseudo-second-order model in adsorption kinetics refers to the process of chemical adsorption in addition to physical adsorption.
Afsaneh Mirzakhani; Morteza Gholami; Arash Amini; Mehdi Borghee
Volume 16, Issue 4 , January 2019, , Pages 249-270
Abstract
Introduction:
The presence of iron in groundwater, even at low concentrations, results in many problems regarding the drinking water. Iron increases the growth of chlorine-resistant microorganisms in drinking water distribution system, leading to an increase in disinfection cost, in addition to problems ...
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Introduction:
The presence of iron in groundwater, even at low concentrations, results in many problems regarding the drinking water. Iron increases the growth of chlorine-resistant microorganisms in drinking water distribution system, leading to an increase in disinfection cost, in addition to problems regarding changes in odor and taste of water. In order to remove iron from water, diverse techniques are being used including oxidation and filtration, absorption or catalytic bed filtration, ion exchange, softening, biofiltration and adsorption. One of the cheapest methods to remove iron from drinking water is adsorption by cheap minerals such as glauconite. In this study, drinking water iron removal by two mineral absorbent glauconites from Sarakhs and Maraveh Tapeh has been investigated.
Material and methods:
The natural glauconites were collected from glauconitic sandstones in Sarakhs (Neyzar formation) and Maraveh Tapeh (Aitamir formation) and were processed in the laboratory and graded in particle diameter 0.5-1.0 mm. The specific surface area and volume of the cavities of the two specimens were determined by BET analysis by nitrogen absorption method. In order to study the kinetic and equilibrium behavior of the adsorption process, iron adsorption kinetic and adsorption isotherm curves on glauconite absorbents have been determined through experimental tests. These tests were done at three pH levels (5, 7, and 9). The aqueous solutions containing 5 mg/l of iron in a volumetric flask were exposed to different amounts of the absorbent at a constant temperature (20 °C).
Results and discussion:
BET analysis as a nitrogen absorption method revealed the specific surfaces of the two glauconite samples from Sarakhs and Maraveh Tapeh as 0.999 and 2.833 m2/g, respectively. The pore volume of Sarakhs and Maraveh Tapeh glauconites were measured as 0.006 and 0.0123 cm3/g, respectively and the average pore diameter were determined 24.07 and 17.31 nm, respectively. The results indicated that as the pH increased, the iron adsorption capacity and absorption rate by the glauconite from Sarakhs and Maraveh Tapeh increased significantly. Comparing the iron adsorption of glauconites revealed that the extracted glauconite from Maraveh Tapeh had more iron adsorption capacity than that of Sarakhs, corresponding to the higher specific surface area of this absorbent. At pH 5, 7, and 9, the ultimate absorption capacity of glauconite from Maraveh Tapeh was 17.3, 11.7 and 13.9 % higher than that of Sarakhs. The kinetic model regression indicated that Hu et al. and Ritchie's models have absolutely similar behavior in describing the iron adsorption kinetics curves on glauconite absorbents. Eventually, it can be stated that the process of iron adsorption by glauconite follows the second order kinetics. The best isotherm model to describe the iron adsorption equilibrium data on glauconite are the models developed by Temkin and Davoudinejad. Accordance with Davoudinejad's model demonstrates the presence of monolayer adsorption along with heterogeneous adsorbent surface and steric hindrances for absorption. Complying with Temkin’s model indicates that absorption enthalpy is a linear function of absorbent surface loading.
Conclusion:
Glauconite mineral absorbents extracted from Sarakhs and Maraveh Tapeh performed better than natural Zeolite and Kaolin and had similar performance to Manganese zeolite, Pyrolusite, and Pumice for iron absorption from the water. Regarding their abundance in Iran, they can be used as an affordable method to solve the problem of the presence of iron in drinking water in Iran.
