جستجوی مقالات مرتبط با کلیدواژه « کربن فعال » در نشریات گروه « عمران »

Nitrates and sulfates are commonly present as common pollutants in most natural waters. Sometimes, human activities such as excessive use of chemical fertilizers, lack of proper control over water sources, and improper treatment of industrial wastewater cause an increase in the concentration of these types of pollutants in surface and groundwater. This study focuses on the efficient removal of nitrates and sulfates from contaminated water using a combination of permeable reactive barriers (PRB) containing zero-valent iron nanoparticles (nZVI) and an electrokinetic (EK) process. In this research, which was carried out on a laboratory scale, by using the PRB system, the nitrate, and sulfate in the polluted groundwater were removed, and simultaneously, with the help of the EK process, the early saturation of the bed was prevented and system performance time is increased. To check the system efficiency, various parameters on the system performance were investigated, and the optimal conditions were determined to grow the system performance time. Additionally, the experiments were repeated using PRB containing granular activated carbon for comparison. The results reveal that the substrate containing nZVI exhibited superior performance in removing nitrates and sulfates from groundwater compared to the modified activated carbon. According to the results, the best system performance was obtained at pH 7, initial nitrate concentration of 200 mg/L, initial sulfate concentration of 450 mg/L, 2.14 gr of nZVI per Kg of sand, and a potential difference of 20 volts. Under these conditions, the use of the PRB containing nZVI not only extended the system operation time by 35 hours for sulfate removal and 30 hours for nitrate removal but also increased the system's removal efficiency by 13% for sulfate and 10% for nitrate after 80 consecutive hours of use, compared to the PRB containing modified activated carbon. Overall, this research contributes to the development of more effective strategies for the simultaneous removal of nitrate and sulfate from contaminated groundwater, using a combination of PRB with nZVI and the EK process.

In this paper, activated carbon prepared from agricultural waste has been used as pollutants absorbent in porous concrete. This activated carbon is produced during two stages of carbonization (pyrolysis) and activation at high temperature. In order to reach the desired and optimal results, the response surface method (RSM) has been used. while evaluating the ability to remove pollutants from runoff water, it has been trying to improve the mechanical characteristics of this type of concrete by adding activated carbon, micro silica, water to cement ratio changes and the amount of fine grains. Design-Expert software was used to design the experiment using the Box-Behnken method. To use the Box-Behnken method, 4 input variables were defined including active carbon percentage (1% to 2.5%), water-cement ratio (0.3 to 0.4%), micro silica percentage (5% to 10%) and fine grain percentage (0 to 10%), which provided 27 mixing plans. Results showed that the presented models for estimating 28-day compressive strength are correlated with R² value of 0.97, 7-day compressive strength with R² value of 0.84, 42-day compressive strength with R² value of 0.95, COD with R² value of 0.94, TSS with R² value of 0.93 , TDS with R² value of 0.91 and copper heavy metal removal with R² value of 0.94, which indicate the significance of the test design as well as the improvement of the mechanical characteristics and removal of pollutants in porous concrete containing waste activated carbon.

Nitrate removal from polluted waters is one of the most important environmental issues. The aim of this study was to remove nitrate from municipal effluent by activated carbon of orange peel modified with chitosan synthesized from shrimp peel and iron (ш) chloride. Identification of activated carbon functional groups by FTIR, the morphology of carbon cavities by SEM, and porosity properties were investigated by BET analysis. The characterization results indicate a porous structure with different functional groups of modified activated carbon. Pseudo-first-order, pseudo-second-order, intra-particle, and Boyd kinetic models were used to describe the kinetic data, as well as Langmuir, Freundlich, and Dubinin-Radushkevitch isotherms to describe the adsorption equilibrium data. The effect of pH and the amount of adsorbent was investigated and the results showed that pH = 2 and the amount of adsorbent 0.2 g in 50 ml of solution are the optimal conditions to achieve maximum nitrate removal. The results showed that the adsorption followed the pseudo-second-order kinetics (R2 = 1). Also, among the studied isotherms, Langmuir model described well the adsorption of nitrate onto synthesized activated carbon (R2 = 0.999) and the maximum adsorption capacity was 263.157 mg/g activated carbon. This behavior means the adsorption of the monolayer and the predominance of the chemical adsorption mechanism. Nitrate uptake increased with decreasing temperature, indicating that the reaction was exothermic. Nitrate removal efficiency with modified activated carbon was estimated to be 99.58%. In general, it can be said that modified carbon can be a candidate for use on an industrial scale.

The rapid development of advanced technologies in the world increases the impact on the daily accumulation of heavy metals in daily life through wastewater. Long-term contact of the human body with heavy metals leads to a variety of infections and diseases. From an environmental and economic perspective, adsorption is an acceptable process that can be used in wastewater treatment. . However, the use of accepted and costly activated carbon adsorbents has led them to look for a suitable alternative to activated carbon. Many studies have been conducted on the physical and chemical properties of geopolymers, which have attracted attention to the replacement of activated carbon in the treatment of heavy metals. In this paper, based on scientific evidences, the absorption of heavy metals using geopolymer is investigated.

Aging in asphalt pavements results in reduced serviceability and flexibility of pavements. Aging is not commonly considered as distress, but it substantially effects the rate of evolution of various distresses. One of the common distress observed in aged asphalt pavements is cracking. If cracks/micro-cracks are healed during their initial formation, the service life of the pavement will be increased. Otherwise, there will be the risk of crack propagation that results in more cracking and loss of pavement strength. It is well known that asphalt mixes have capability of self-healing their cracks/micro-cracks when they are exposed to high temperatures. Cracks/micro-cracks in asphalt mixes can be healed through an induced healing process. Induced healing of asphalt mixes by applying external electromagnetic radiation is an innovative technique to repair cracks/micro-cracks. Applying external energy through electromagnetic radiation increases the temperature of the asphalt binder in mixes, allowing it to move and fill the cracks/micro-cracks. Flowing and crack filling of asphalt binder play a significant role in induced healing characteristics of mixes. As temperature of the asphalt binder is increased, its viscosity will be decreased drastically. When asphalt binder gets to Newtonian fluid temperature or higher, the melted binder moves inside the cracks and micro-cracks and subsequently, the cracks will be healed. The aim of this research was to evaluate the effects of different aging levels on induced heating-healing of asphalt mixes. In order to impose different aging levels, asphalt mixes were aged in oven for 3, 5, 7 and 9 days at 85 ºC. Activated carbon was added to mixes so that to enhance electromagnetic sensitivity of mixes. In addition, effects of activated carbon on mechanical properties and microwave heating rate of mixes were determined. Results indicated that activated carbon, as a powder-based additive, improves electrical conductivity, induced heating-healing rate of asphalt mixes. In addition, it was shown that aging phenomenon in asphalt mixes decreases their heating rate, which was more pronounced in higher aging level. Lower heating rate of asphalt mixes resulting in lower efficiency of induced healing of mixes. For evaluating healing capability of mixes that were subjected to different aging levels, Semicircular Bending tests (SCB) was conducted at intermediate and low temperatures. It presented that induced healing efficiency of mixes decreased as the aging level and the notch length in SCB testing were increased. The adverse effects of aging on induced healing process can be attributed to increased viscosity of the asphalt binder in mixes, which limits moving capability of melted asphalt binders to move through damages and properly heal the cracks. Moreover, it resulted that, lower heating rate of aged mixes can be considered as another reason of reduction in induced healing efficiency. The results indicated that increased notch lengths not only affects load at fracture and fracture energy of mixes, but also it plays a significant role in induced healing efficiency of mixes. For further evaluation of the healing ability of asphalt mixes, combination effects of aging, notch lengths and testing temperature parameters were also investigated. Notch length and testing temperature was found to have significant effects on induced healing efficiency of mixes. In addition, the results indicated that induced healing efficiency of low temperature cracked asphalt mixes were more than that of asphalt mixes that were cracked at intermediate temperatures. The results suggest that the necessity of considering aging level in analyzing induced heating-healing process of asphalt mixes.

Mesoporous activated carbon production from lignocellulose waste for removing reactive dyes Blue 19 and Blue 21 from aqueous solution Introduction. Reactive dyes have been increasing in textile industries for dyeing natural and synthetic fibers. Discharge of dye- bearing waste-water makes an adverse effect on aquatic environment because the dyes give water undesirable color. The major environmental and health problems associated with water pollution caused by the discharge of untreated textile effluent are due to disorders in the aquatic environment because of use of toxic chemicals. The aim of this study was to investigate the adsorption potential of as-produced activated carbon from grape wood residue (Vitis Vinifera) in order to remove Reactive Blue 19 (RB19) and Reactive Blue 21 (RB21) dyes from aqueous solution. Activated carbon is the most common adsorbent for the removal of many dyes.Activated carbons are made from various agricultural wastes by physical and chemical activation. The preparation of activated carbon from agricultural waste could increase economic return and also provides an excellent method for the solid waste disposal thereby reduce pollution. The adsorbates in this study included three reactive dyes, Reactive Red 23 (RR23), Reactive Blue 19 and Reactive Blue 21. All dyes were commercial grade and employed without further purification. The activated carbon was synthesized from grape wood biomass by activation of phosphoric acid (H3PO4) with impragnation ratios of 1:1 1:2,1:3, 1:4. The FTIR, BET, and SEM techniques were used to characterize the as-prepared carbon materials. In addition, dye adsorption experiments were carried out, which measurements are taken for all of the samples under in the same condition, at pH of 2, adsorbent dose of 0.01 g/l, initial dye concentration of 250 mg/l, sworking volume of 100 ml, and contact time of 120 min. The results showed that the carbon sample activated under imprenation ratio of 1:4 and temperature of 600oC, that obtained a special surface area of 1850 m2/g, and total pore volume of 2.40 cm3/g, and pore size distribution of mesoporous at 86%, had maximum adsorption capacity of 1932 and 908 mg/g for RB19 and RB21 dyes, respectively. The adsorption behaviors of three reactive dyes (Reactive Blue 19 23, Reactive Blue 21) onto this biomass activated carbon were investigated in batch systems. The experimental data were analysed by the Langmuir, Freundlich and Sips models of adsorption. Equilibrium data of dyse fitted well with the Sips model. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The equilibrium adsorption capacity of the Activated carbon was determined with the Langmuir equation found to be 1914 mg/g for Reactive Blue 19 and 1195 mg/g for Reactive Blue 21. This study showed that activated carbon produced from annual pruning vineyards waste has a high potential in the treatment of textile wastewater. Also results indicate that Activated carbon from grape wood could be employed as low-cost alternative to commercial activated carbon in wastewater treatment for the removal of acid dyes. Keywords: Activated carbon, lignocellulose waste, Grape wood, Blue 19, Blue 21

Distilleries wastewater (vinasse) because of its pollution problems is serious environmental concern. In this study the equilibrium and kinetic studies of adsorption organic compounds of vinasse onto granular activated carbon was investigated. In order to determine the effect of initial COD (Chemical Oxygen Demand) concentration on the adsorption effciency, different COD concentrations with granular activated carbon (GAC) dosage of 50 g/l were tested. The COD removal trends for different concentration vinasse solution was investigated at different initial concentration, pH=2 and temperature of 25 °C. The ultimate or equilibrium concentrations were determined for all initial COD concentration.

Heavy metals, such as lead, chromium and nickel, are known to be major environmental pollutants and highly toxic to humans and other organisms, even at low concentrations. Chromium is widely used in many industries in various forms, but chromium (VI) is considered a de nite carcinogen and, thus, should be almost completely removed from industrial wastewater to meet environmental laws and regulations. Many techniques are used to treat wastewater, containing Cr (VI), including; reduction followed by precipitation, Ion exchange, adsorption by clay or activated carbon and reverse osmosis. However, these processes often produce too much sludge, or are inecient when large volumes of wastewater are involved or do not meet environmental standards. Adsorption is another eective method with very few disadvantages compared to others. In recent years, synthetic polymers have been considered as quality adsorbents for removal of Cr(VI) from wastewater. The aim of this study is to investigate the possibility of absorption of chromium from aqueous solutions by a new and innovative adsorbent produced from Polyaniline-activated carbon. The eect of various operative parameters on the adsorption of Cr (VI) was studied. Experiments were carried in batch mode and the eect of variables, such as the initial concentration of Cr (VI), amount of adsorbent, adsorption time, and initial pH value and temperature, were studied. The maximum adsorption of Cr (VI) was obtained at 400C, with an initial concentration of 15 ppm, with an initial solution pH of less than 5 and addition of 10 g/lit Polyaniline-activated carbon. Recovery of the adsorbent was carried out by desorption with nitric acid, where 2 M nitric acid was used to recover 83% of Cr (VI). The results indicate that Polyaniline-Activated carbon can be eectively used in the treatment of wastewater containing Cr (VI). Kinetic studies on adsorption behavior closely followed the \Langmuir adsorption isotherm" model for a single layer.

Activated carbon is widely used at various industrial processes such as water and wastewater industries. Activated Carbon (AC) is an adsorbent which is mostly employed for removing dye from aqueous solutions because of its excellent adsorption properties. Therefore، AC is used in the adsorption process in order to remove different pollutants from the wastewater، especially colored contaminants. however; the use of commercial grade of activated carbon is faced with difficulties due to the high price of raw materials. The used newspaper found as a main component of solid wastes can be used for producing of activated carbon. One of the most important industrial pollutants، especially in textile industries، is the dyes that even at low concentrations of one parts per million (ppm) are recognizable by naked eyes. One of the mostly consumed materials in the dye industry is Methylene Blue (MB) which is used for cotton and silk dyeing. Up to now، a great number of methods have been proposed in order to remove dyes from the industrial waste water، among which adsorption is the most acceptable due to its cost effectiveness and the possibility of usage in large scales. The aim of this study is to evaluate the performance of activated carbon produced from the used newspaper for the removal of methylene blue dye in aqueous solution. KOH solution (weighted ratio of 1:3) was used to activation. The carbonization process was applied at 500˚C with the rate of 17˚C/min. After carbonization، the sample was cooled down to room temperature and then washed with distilled water until the pH of the filtered water was stabilized at 7. 5. N2 adsorption at 77K is used to characterize the produced activated carbon using BET isotherm. To evaluate the performance of methylene blue dye removal، the Langmuir، Freundlich، Temkin and Redlich-Peterson isotherms with pseudo-first and pseudo-second order and inter-particle diffusion kinetic models were used. Thermodynamic parameters such as enthalpy (ΔΗ˚)، entropy (ΔS˚) Gibbs free energy (ΔG˚) were also calculated. Based on the results، the values of SBET and VTOTAL were obtained 66. 01 m2/g and 0. 063 ml/g، respectively. According to the R2 and sum of squares for error (SSE%) values and regression curves، the optimum isotherm and kinetic model were determined Freundlich and pseudo-second order ones، respectively. In addition، qmax constant was obtained 68. 03 mg/g for Langmuir isotherm. Kinetic parameters showed the adsorption of methylene blue dye on the activated carbon is endothermic and spontaneous. Also، (ΔG˚) in physical adsorption was changed from 0 to -20 kJ/mol، while the amount of the chemical adsorption will changed between -80 to -400. Finally، the activated carbon obtained from used newspaper in this study showed a better specific surface area and adsorption capacity for methylene blue dye adsorption in compared with other grades. Thus، the production of activated carbon from used newspaper should be considered as a cheaper and more effective alternative.