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.
Ali Marefat; Abdolreza Karbassi; Hassan Sereshti
Volume 15, Issue 1 , April 2017, , Pages 15-26
Abstract
Introduction: Nowadays, the study of estuarine zones is essential because more than half of the world’s population is living along estuaries. As a result, estuaries are potentially facing a lot of different pollutants, including heavy metals. For this purpose, estuary conditions must be simulated. ...
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Introduction: Nowadays, the study of estuarine zones is essential because more than half of the world’s population is living along estuaries. As a result, estuaries are potentially facing a lot of different pollutants, including heavy metals. For this purpose, estuary conditions must be simulated. Since the formation of estuaries is the result of mixing of fresh river water with saline sea water, they can be simulated by creating different salinity regimes.Materials and methods: this simulation was an attempt to study the behaviour of heavy metals (Zn, Pb, Ni, Cu and Mn) in the estuary of the biggest river of northern Iran, the Sefidrud River that flows into the Caspian Sea. For this purpose, fresh and saline water were mixed in 5 different proportions until salinity regimes of 1 to 3.4 psu were created. After flocs were formed, each of samples was filtered separately by 0.22 -µm Millipore membrane filters. Filters containing the flocs were put in small beakers, and 5 cc of acid nitric was added to the beakers. After 6 hours both filters and the flocs on the filters were digested. The volume of liquid inside the beakers was increased to 10 cc by using 1 N HCl. The metal contents of the metals were measured by ICP. Cluster analysis, a statistical method, was used to determine the effect of chemical and physical parameters on the flocculation process. Results and discussion: Estuaries act as filters to reduce the load of heavy metals in saline water environments such as seas. The present investigation provides a laboratory experimental study of eliminating soluble and colloidal elements of manganese, zinc, lead, nickel and copper during the estuarine mixing of Sefidrud River water with Caspian Sea water due to the flocculation process. The results obtained show that the two elements zinc and lead are, respectively, flocculated at 100% and 0% during the estuarine mixing. Such extremely high and low flocculation is indicative of the conservative and non-conservative nature, respectively, of Pb and Zn.The flocculation rates of copper, nickel and manganese are as follows: Cu (55%)> Ni (41%)>Mn (4%). In other words, various portions of the studied metals are removed during estuarine mixing in the form of tiny flocculants. Statistical analyses indicate that S, E, C, pH and Eh govern the flocculation of zinc. Dissolved oxygen was the only parameter that affected the flocculation of copper. It should be pointed out that the flocculation of nickel and manganese is not governed by S, EC, pH and Eh. Conclusion: estuarine zone has different effects on different metals because of the various forms of the metals and chemical and physical parameters.
