In the present study, seven types of films were produced using different proportions of polyethylene containing silver, clay, and titanium dioxide nanoparticles. Following the determination of the minimum inhibitory concentration of the films in the eradication of Staphylococcus aureus and Escherichia coli, the film containing 5% silver nanoparticles and 5% titanium dioxide nanoparticles was found to have the highest antimicrobial property and was determined to be an ideal cover for food products. The antibacterial effect of the films on the shelf life extension and quality of the chicken stored at 4 °C in the Days 1, 3, and 5 of the experiment was checked. The structure and morphology of the nanoparticles and the selected films were evaluated using a field emission scanning electron microscope, scanning electron microscope, transmission electron microscope, Fourier‐transform infrared spectroscopy, and dynamic light scattering. The analysis of the results indicated that the most appropriate inhibition growth was observed with S. aureus and E. coli in nutrient agar and the largest diameter of the radial inhibition zone occurred with S. aureus. Moreover, the analysis of variance showed that the effect of different concentrations of silver and titanium dioxide nanoparticles was significant (p < .05). The results of this study showed that the produced nanocomposite was used to preserve chicken meat for 5 days at 4 °C inhibited the growth of both types of bacteria.
Practical applications
Nowadays production of active packaging is increasing worldwide as they were proved to have numerous effects on inhibiting of microbial growth and even bactericidal effects. Therefore, a wide variety of food producers in different sections namely agriculture, dairy, and meat industries have applied nanopackaging using different nanoparticles. Thus, more research on different physicochemical and antimicrobial effects are needed.
One of the massive by-products of concrete to concrete recycling is the crushed concrete fines, that is often 0 -4mm. Although the construction sector is to some extent familiar with the utilization of the recycled coarse fraction (>4 mm), at present there is no high-quality application for fines due to its moisturized and contaminated nature. Here we present an effective recycling process on lab scale to separate the cementitious powder from the sandy part in the crushed concrete fines and deliver attractive products with the minimum amount of contaminants. For this study, a lab scale Heating-Air classification system was designed and constructed. A combination of heat and air classification, resulted in a proper separation of finer fraction (0 -0.250 mm), from coarser fractions. Heating of the materials was followed by ball milling to enhance the liberation of the cementitious fraction. Experiments were carried out at different heating temperatures and milling durations. Experimental results show that by heating the materials to 500˚C for 30 seconds, the required time of ball milling is diminished by a factor of three and the quality of the recycling products satisfies well the market demand. In addition, the removal of contaminants is complete at 500˚C. The amount of CaO in the recovered finer fraction from the recycling process is comparable with the amount of CaO in low-quality limestone. By using this fraction in the cement kiln as the replacement of limestone, the release of the chemically bound CO2 could be reduced by a factor of three.
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