بازیافت

To address climate change issue and transition from fossil fuels to renewable energy, wind energy plays a pivotal role. Several countries have installed wind turbines in the past years and have long-term plans to harness wind energy in the coming decades. Given the large number of these turbines and their limited lifespan, typically ranging from 20 to 30 years, managing the waste from their components has become a significant challenge. In particular, the recycling of wind turbines blades, mostly made of fiberglass composites, is a difficult task. It is predicted that by the end of 2050, approximately 43 million tons of blades will reach the end of their operational life. The present study introduces the waste management and recycling technologies for these blades. Following the waste management hierarchy, which consists of the prevention, reuse, repurpose, recycling, recovery, and disposal, the three key recycling methods_ mechanical, thermal, and chemical_ are thoroughly examined. The chemical method can be applied not only to new blades but also to older ones, bringing them back to the recycling process and contributing to the production of new-generation blades, thereby supporting the development of a circular economy.

In this study, by selecting the appropriate process conditions and using aluminum cans, the aluminum alkoxide compound was prepared and used as a precursor in aluminum oxide (Al2O3) nanoparticle synthesis processes by sol-gel method. In the production of mesoporous Al2O3 nanoparticle via sol-gel process, the aging temperature of 25, 60, 80 °C and time of 12, 24 and 48 h were selected and investigated as the main parameters in determining the solute particle size and bonding during the gel process. The results showed that the aging temperature is 80 °C and 24h time as the optimal conditions for the synthesis of Al2O3 nanoparticle with superior properties in terms of specific surface area and porosity. The calcination temperature showed that the minimum temperature required to reach the alumina phase is 500 °C. However, due to the necessity of the presence of crystalline phase with maximum ordering in the layout of the atomic plates of 900 °C and 1 hour storage time, the optimum calcination conditions were selected. Scanning and transmission electron microscopy studies of the optimum sample showed that the final product had the same appearance as the nanoparticles, and the particle size distribution was in the range of 20 to 40 nm. It was also found that the synthesized nanoparticles have very distinct crystalline plates, and as a result of the nanoparticles bonding to each other and forming larger masses, porosities in the meso-range were formed in their microstructure which made the end product to be used as a catalyst substrate.

Lead-acid batteries are a significant part of the global battery market; however, due to limited life of these batteries, we are faced with major environmental challenges associated with lead-acid battery waste. One of their main components is the separator. In addition to polyethylene and silica, the separator of these batteries also contains lead compounds. In this research, lead-acid battery separator and polyethylene were used as a matrix for preparing a composite that could improve polyethylene's mechanical properties due to the presence of silica. Samples of HDPE and LLDPE with 5% to 15% lead-acid battery separator were prepared and their mechanical and thermal properties were evaluated and compared. By analyzing the DSC results, the type of polyethylene in the battery separator, HDPE, was determined. By adding the battery separator to HDPE matrix, elastic modulus increased by about 22% and bending modulus by about 55%. For LLDPE elastic modulus increased by approximately 35%. The yield strength of the sample, with HDPE matrix containing 15% separator has increased from 25.1 MPa to 28 MPa, and for the sample, with LLDPE matrix containing 15% separator, yield strength increased from 11.9 MPa to 13.7 MPa. Hardness and modulus for 15% of the separator are at maximum value. Consequently, 15 wt.% separator is an optimal value to improve samples' mechanical properties.

U-500 is a nickel-based superalloy which has significant amounts of some precious elements such as cobalt and chromium. Due to the economic and strategic value of these metals, their recovery from the used superalloys is of great importance. Hydrometallurgy is an economical and effective method for recovering these valuable metals from the superalloy scraps. So in this investigation, the dissolution behavior of nickel, cobalt and chromium elements from the used U-500 superalloy in the electro leaching process as well as the effect of different process parameters (such as: sulfuric acid concentration, applied voltage, process temperature, stirring and cathode-anode distance) on the dissolution of these elements are studied in details. The results show clearly that by increasing the concentration of sulfuric acid in the electrolyte, the applied voltage, and temperature, as well as decreasing the cathode-anode distance, the anodic dissolution of the superalloy U-500 is improved. Electrolyte stirring has no significant effect on increasing the anodic dissolution of the superalloy. The optimum conditions for the anodic dissolution of superalloy U-500 in sulfuric acid electrolyte was determined as acid concentration of 125 g/L, applied voltage of 4 V, stirring speed of 300 rpm, and cathode-anode distance of 3 cm without temperature control (starting with ambient temperature as the initial temperature(. Under these conditions, about 75% nickel, 84% cobalt and 67% chromium were durnig 25 minutes.

In the present project, the use of scarp electronic components in the synthesis of silver nanoparticles was investigated. For this purpose, crystalline oscillators were used as a consumable piece to synthesize these particles. The results showed that by optimizing the time and temperature of dissolution process with nitric acid solution up to 90% silver can be separated from these components. The temperature of 60°C and the time of one hour were determined as the optimum conditions of this section. Then, the synthesis of silver nanoparticles was investigated using silver nitrate solution. The results showed that the initial silver nitrate concentration had a significant effect on the final product quality, so that at 1 mollar concentration, the best conditions were provided for the synthesis of silver nanoparticles with suitable properties. Phase’s evaluation illustrated that the main phase of the synthesized silver particles had an FCC structure and no unwanted phase was observed. UV analysis of the synthesized powder showed that the core peak of the silver nanoparticles appeared in the wavelength range of 400 to 450 nm. The DLS results showed that the concentration of 1 mollar was the optimum concentration of silver nitrate in the present study. The AFM and TEM observation show that the silver particles synthesized with a particle size less that 20 nanometer, spherical morphology and uniform particle size distribution.

In this paper, the properties and microstructure of foam glasses obtained from the wasted cathode ray tube (CRT) display panels were investigated. The foam glasses were prepared at the temperatures of 850, 950 and 1050C using 2, 4, 6 and 8 wt.% silicon carbide (SiC) as the foaming agent. The physical and mechanical properties of the samples including the density, porosity, four-point bending strength were evaluated in this research. The microstructures of samples were examined by means of a scanning electron microscope. The results showed that SiC as the foaming agent is able to control the pore size and also to cause a narrow distribution of pores in the microstructures. The decomposition of SiC in the presence of oxygen at the temperature of 950C led to the formation of gas bubbles and therefore, the foam glass was produced. The sample with 6 wt.% SiC exhibited the highest amount of porosity (about to 55%) and relatively uniform microstructure after being sintered at 950C for 1 hour. The four-point bending strength of the latter sample was measured to be 12 MPa. The properties and microstructure of this sample were found to be comparable with those of the commercial samples