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

In this paper, the preparation of nano zeolite was carried out at different grinding times using a dry planetary ball mill. Sodium Hexa Meta Phosphate (SHMP) was introduced as the dispersant in the milling of natural zeolite adsorbent. In the next step, to remove and adsorb heavy metal ions such as nickel, copper, and cadmium, the application of nano zeolite was studied in batch mode.

In this paper, zeolite nanoparticles were produced using planetary and ball mills. Adsorption experiments were conducted to investigate the adsorption of nickel, copper, and cadmium using new nano zeolite adsorbent. 

The effect of Sodium Hexa Meta Phosphate (SHMP) on grinding and adsorption of ion metals by nano zeolite was investigated and results showed that the application of SHMP led to lower energy consumption in grinding and had a positive effect on nickel and cadmium removal from aqueous solution by nano zeolite particles.

The effect of sodium hexametaphosphate on the absorption of nickel, cadmium, and copper metals showed that this reagent had a positive effect on the absorption of nickel and cadmium ions on nanozeolite particles, but it did not affect the absorption of copper ions. Nano-zeolites have a larger external surface area and a shorter diffusion path length due to having nano-sized particles, so their absorption capacity is very high.

The increase of various industries and the ever-increasing growth of the population of the planet have caused all kinds of contamination in the environment. One of the most important contaminants in water, which has many risks for human health and living organisms and important environmental risks, is anionic compounds in high concentration. Chromium is one of these contaminants that causes contamination in the environment and brings many risks to human health and other living organisms. Various methods have been evaluated to remove heavy metals from water, which often include chemical or energy-intensive processes. Therefore, it is important to modify these sources with the help of affordable adsorbents and with low energy consumption. Previous studies showed that biochar, metal-coated biochars and carbon-metal composites are highly effective in removing chromium contaminants with a concentration of 20 mg/liter from water, but so far the effect of these adsorbents on removing this anionic contaminant in high concentrations has not been investigated.

In this research, the efficiency of different adsorbents (biochar, copper-coated biochar, aluminum-coated biochar, iron-coated biochar, biochar-copper composite, biochar-aluminum composite and biochar-iron composite) on the removal of chromium, with a concentration of 300 mg per liter, from water was investigated. Metal-coated biochars were prepared from the combination of metals (copper, iron and aluminum) with a concentration of 10000 mg/kg with biochar produced at 600 degrees Celsius and various biochar-metal composites were prepared from the combination of these metals with rice straw and then the samples were pyrolyzed at 600 degrees Celsius. In order to determine the efficiency of the adsorbents, 0.5 grams of each adsorbent was mixed with 40 ml of chromium solution with a concentration of 300 mg/l and pH= 6 and shaken for three hours until they reached equilibrium. Then the samples were centrifuged for 5 minutes at 6000 rpm and after the filtration, the final concentration of the contaminant was obtained and the percentage of chromium removal was calculated.

The results of the present study showed that all of the applied adsorbents were effective in removing high concentrations of chromium from water. The lowest removal rate of this contaminant was related to the biochar sample, which only removed 15.28% of this contaminant from water; And the highest amount of removal was achieved using iron composite, which removed 44.45% of the contaminant from the aqueous solution. According to the results of this research, it can be observed that coating biochar and rice straw with metals has been able to increase the efficiency of this adsorbent in removing chromium from water. For example, iron composite and iron-coated biochar were able to remove 44.45 and 30.86% of chromium contaminant from the aqueous solution, respectively, while rice straw biochar was only able to remove 15.28% of this contaminant from water.

The results of present study showed that iron coated biochar and biochar-iron composite had more ability to remove chromium contaminant from aqueous solution than other metal coated biochars and biochar-metal composites and were able to perform more successfully. Therefore, the use of these adsorbents can be effective in the treatment of chromium-contaminated water.

In this study, hydroxyapatite-supported zero-valent iron nanoparticle was synthesized by the sodium borohydride reduction method. To evaluate the performance of adsorbent for the removal of Cu(II) and Ni(II) ions, the influence of different sorption parameters, such as contact time, temperature, initial concentration of metal ions, the dosage of adsorbent, and pH value of the solutions were investigated. The highest removal efficiency of both metals occurred under the optimal conditions of 7, 45 min, 0.1, 50 ºC, and 5 mg/l for pH, contact time, adsorbent mass, temperature, and initial concentration, respectively. The kinetic and equilibrium data were well fitted by the pseudo-second-order model and Langmuir- Freundlich model, respectively. The maximum adsorption capacities of adsorbent towards Cu(II) and Ni(II) were 138 and 108 mg/g, respectively. The results indicated that the adsorbent could remove the majority of metals (95%) within 40 min without pH control. Thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, indicated that the sorption process was spontaneous and thermodynamically favorable.

 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.

 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.

 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.

 Findings of this research demonstrated the applicabil ity 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.

The performance of the Fe3O4- CeO2- NH2/ chitosan/ Polyvinyl alcohol nano hybrid synthesized by casting method was investigated for the adsorption of Cu (II) and Ni (II) cations from water system. The synthesized nano hybrid adsorbents were characterized by FESEM, BET and FTIR analyses. The effect of single and binary oxides content, Fe3O4-CeO2-NH2 content, pH, initial cation concentration, contact time and temperature on the adsorption capacity was evaluated in a batch system. The results showed that the adsorption capacity significantly increased after modification of adsorbent with Fe3O4- CeO2- NH2 nanoparticles. The kinetic and equilibrium data were accurately evaluated by the double- exponential and Redlich- Peterson models, respectively. The maximum adsorption capacity of nano hybrid adsorbent was estimated to be 246.9 and 88.6 mg / g at 45 º C for Cu (II) and Ni (II) cations, respectively. Thermodynamic investigation indicated an endothermic and spontaneous adsorption for both metal cations; and adsorption was favored at higher temperature. The synthesized nano hybrid can be easily regenerated after five cycles of adsorption- desorption. 

Nitrogen dioxide (NO2) is one of the most dangerous pollutants in the environment. NO2 certainly causes lung damage at high concentrations. Exposure to its moderate levels (50 ppm) for a short period may produce irritation of the eyes, nose, and throat, cough, hemoptysis, dyspnea, and chest pain and contact to its high concentrations (> 100 ppm) can result in pulmonary edema, which can be fatal. Therefore, it is very important for environment the removing of the pollutant from air. The aim of this study has been the removal of NO2 gas by some natural adsorbents by using the adsorption method.

 In this work, it has been investigated the removal of NO2 gas by adsorption on different natural adsorbents including eggshell, eucalyptus bark, fennel seed, pine leaf, tea waste, and wheat straw. It was also studied the effect of some experimental conditions including adsorbent column length and initial NO2 amount on the adsorption percentage.

The most desirable adsorption percentage obtained with adsorbent column length 50 cm and initial NO2 amount 6.3 mmol. In addition, Fennel seed and eggshell can adsorb 96.8 and 92.1% of NO2 gas in the optimum conditions, respectively.

Among the used adsorbents, the most appropriate adsorbents are fennel seed and eggshell for the adsorption process. In addition, it was correlated the equilibrium data with the adsorption isotherms such as the Langmuir, Freundlich, Temkin, and Harkin-Jura and the results showed that Harkin-Jura isotherm describes the experimental results better than the other isotherms.

Industrial and agricultural processes have resulted in the release of cadmium metal into the ecosystem. One way to remove this heavy metal is adsorption. This research aimed to determine the efficiency of magnetic nanographene for removing cadmium ions from aqueous solution., This research was done in a discontinuous system at a laboratory scale. For this purpose, the effect of effective parameters such as pH, concentration, contact time, ambient temperature, adsorbent dose, and other factors was investigated. The results showed that the maximum amount of cadmium absorption occurred in the conditions of pH=6, concentration 100 mg/l, contact time 120 min, ambient temperature 45 ° C and adsorbent dose 0.01 g.  Thermodynamic parameters showed that the absorption process of cadmium metal was spontaneous and endothermic in the temperature range of 288 to 318 K The pseudo-second-order model with adsorption rate constant (K2 = 0.0092) and coefficient of determination (R2 = 0.99) showed that it describes the laboratory data better. Also, the examination of adsorption isotherms showed that the Freundlich isotherm (R2 = 0.96) was more suitable for describing the adsorption process and was more consistent with the laboratory data. According to the results of this research, magnetic oxide nanographene adsorbent with 92.8% efficiency can be used to remove cadmium from aqueous solutions.