Maryam Rabiee Abyaneh; Gholamreza Nabi Bidhendi; Ali Daryabeigi Zand
Abstract
Introduction: Landfill leachate is a highly toxic and hazardous form of wastewater due to its complex composition characteristics. Effective removal of heavy metals from landfill leachate is of great concern due to the fact that toxic metals can seriously threaten the food chain, and therefore the human ...
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Introduction: Landfill leachate is a highly toxic and hazardous form of wastewater due to its complex composition characteristics. Effective removal of heavy metals from landfill leachate is of great concern due to the fact that toxic metals can seriously threaten the food chain, and therefore the human health. The main objective of this work was to study the utilizing of low-cost pruning residues in the production of biochar and its application in removal of lead (Pb) from landfill leachate.Material and methods: Leachate produced in Babol municipal solid waste landfill was used as an adsorbent solution. Pruning residues were collected and used for biochar preparation. Biochar produced under the pyrolytic temperature of 700°C with a 1-hour retention time. The adsorption mechanism of pruning waste biochar to Pb was analyzed through BET surface area and scanning electron microscope (SEM) tests. Batch experiments were performed to study the effects of adsorption parameters on Pb removal. The influence of contact time (30-300 min), adsorbent dosage (1-50 g/L), as well as particle size (1-2 mm and 63-75 µm) was investigated. Moreover, the kinetic and isotherm models were applied to the experimental data to predict the adsorption parameters.Results and discussion: The results obtained from the analysis of the untreated Babol landfill leachate was revealed that the Pb concentration was about 4.94 mg L-1. The surface area of the produced biochar was determined to be 292.44 m2 g-1. SEM microstructure of the biochar showed the developed surface area with visible pores. All of these data seem to suggest a great potential for pruning residues biochar to Pb removal. The adsorption of Pb was mainly affected by contact time, adsorbent dose, and biochar particle size. Higher contact time and adsorbent dosage showed higher uptake of Pb. Whereas, the uptake of Pb ions onto pruning residues biochar was substantially reduced with increase the biochar particle size. Maximum Pb percentage removal was observed at a contact time of 90 min and with an optimum biochar dosage of 20 g L-1 (89.06% removal) for biochar with 1-2 mm particle size. While, biochar with particle size of 64-75 µm can removed Pb to almost 100% at a contact time of 120 min and with an optimum biochar dosage of 20 g L-1. The kinetic study showed that adsorption can be well described by the pseudo-second order kinetic model. This supports the chemisorption theory behind the pseudo-second order kinetic model for the adsorption system. The results of isotherm models implied that the behaviors of the isotherms are more appropriate for the Langmuir model, showing a monolayer adsorption capacity for Pb.Conclusion: Findings of this research demonstrated the applicability of pruning residues biochar as an economic adsorbent for the removal of the Pb from landfill leachate. On the other hand, the crop residue burning poses a threat to the environment and human health due to the emission of toxic gasses and particulate matter. So, conversion of pruning residues to biochar and its application to heavy metal removal is a useful and environment-friendly alternative to crop residue and biomass burning.
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.
Elham Noshadi; Mehdi Homaee; Mohammad Mahmoudian Shoushtari
Volume 15, Issue 2 , July 2017, , Pages 111-128
Abstract
Introduction:
Contamination from agricultural inputs, particularly herbicides, is one of the most important environmental challenges and the use of modern technologies such as herbigation has intensified this problem. Thus, employing optimal management strategies based on knowledge of herbicide behaviour ...
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Introduction:
Contamination from agricultural inputs, particularly herbicides, is one of the most important environmental challenges and the use of modern technologies such as herbigation has intensified this problem. Thus, employing optimal management strategies based on knowledge of herbicide behaviour and processes in soil is necessary. The objective of this study was to assess quantitatively the herbicide adsorption-desorption behaviour in soil in the laboratory and under real field conditions.
Materials and methods:
Consequently, metribuzin was applied to the experimental plots using the herbigation (HRB) and conventional spraying (CS) methods, and to laboratory samples. After inspecting the adsorption and desorption behaviour of herbicide by batch and centrifugal methods, different models of equilibrium adsorption were fitted to the data.
Results and discussion:
Results indicated that, due to the low amount of organic matter and clay in the soil, herbicide adsorption was generally weak in all three types of treatment and that the overall process followed the Freundlich model. The results further showed that in all three treatments because of the adsorption mechanism’s weak hydrogen bond, a large portion of the adsorbed molecules desorbed after four washing cycles. However, in the laboratory and herbigation treatments, the amount desorbed was relatively less and, due to the diffusion of molecules into inter-aggregate pores, a small hysteresis can be seen.
Conclusion:
In conclusion the results show, the adsorption amount in laboratory and herbigation treatments is greater than conventional spraying treatments due to a higher moisture level in the soil and increased hydrophilic sites on organic matters and diffusion within the inter-aggregate pores. Therefore, the methods of pesticide application affect the adsorption and desorption behaviour of it. So pesticide application by herbigation is suggested in order to reduce losses and increase efficiency in the field.
Hamid Raftari; Hamid Moazami; Hossein Ganjidoust; Bita Ayati
Volume 8, Issue 3 , April 2011
Abstract
Lead and copper are heavy metals that are applied in different industries. Their standard limits in drinking water are 0.05 and 1.3 mg/L, respectively. Since natural absorbents are inexpensive and may be achieved without any cost and they are usually found in abundance in nature, absorption of solute ...
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Lead and copper are heavy metals that are applied in different industries. Their standard limits in drinking water are 0.05 and 1.3 mg/L, respectively. Since natural absorbents are inexpensive and may be achieved without any cost and they are usually found in abundance in nature, absorption of solute ions by these materials is a proper method for eliminating heavy metals from polluted waters and industrial wastewaters. In this study, tea leaves and wheat straw wastes were used to absorb lead while sawdust and rice hull were applied to absorb copper from a polluted solution under batch and continuous conditions. The experiments have been carried out at different concentrations and times with an optimum pH of 5 and 5.5 for lead and copper, respectively. According to the batch experimental results, the equilibrium time has been found to be within the range of two hours. By increasing the concentration of absorbed material, the absorption efficiency has been diminished. The results of the batch experiments coincided with Langmuir and Freundlich isotherms but did not agree with BET and Linear isotherms. Continuous experiments have been accomplished with the use of an absorption column and a high up-flow rate of 0.35 L/min. In general, absorption efficiency has a decreasing trend over time. Based on the results of the continuous column system, the percentage maximum sorption of lead for tea leaves and wheat straw wastes came to be 99.5. This value for copper by sawdust and rice husk was found to be 95 and 63 percent, respectively.
Akbar Baghvand,; Ali Daryabeigi Zand,; Gholamreza Nabibidhendi; Nasser Mehrdadi
Volume 8, Issue 2 , January 2011
Abstract
Column leaching tests become increasingly important for assessing the risk of release of pollutants from soil into water. In this study a column leaching test was designed to provide insight into the fate of selected PAHs in soils and their leaching behavior. Two columns (columns 1 and 2) were prepared ...
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Column leaching tests become increasingly important for assessing the risk of release of pollutants from soil into water. In this study a column leaching test was designed to provide insight into the fate of selected PAHs in soils and their leaching behavior. Two columns (columns 1 and 2) were prepared based on a standard procedure in which 5 and 20 percent of contaminated soil were used, respectively. The percolates were collected at specified L/S ratios. Results showed relatively high initial concentrations of flourene, fluoranthene and benzo(a)anthracene for column 2. Released amounts of PAH compounds were decreasing with increasing molecular size, or rather the hydrophobicity of the compound. The effect of dissolved organic carbon on PAHs leaching was also investigated in this research. Approximately 2.45% and 0.67% of the total initial amounts of studied PAHs in the soil was leached in columns 1 and 2, respectively. Results showed that high PAHs concentration in the solid phase does not necessarily imply serious groundwater contamination risk during a leaching event (e.g. rain fall) and significant amount of contaminants may stay in the soil layer for a long time and do not leach down into groundwater.
