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Abstract Background The use of bacteria to synthesize nanoparticles as an environment-friendly method has recently been considered by researchers. Bacteria residing in different mines have shown high potential in the synthesis of metal nanoparticles due to their compatibility with the environment. The aim of this study was to evaluate the ability of Zarshouran gold mine bacteria to synthesize silver nanoparticles and their antibacterial activity. Methods After isolation of mine bacteria and several screening steps, silver ion tolerant bacteria that were able to synthesize extracellular silver nanoparticles were isolated and the most suitable isolate was selected and sequenced. The characteristics, stability, and production efficiency of silver nanoparticles were evaluated using UV–vis spectrophotometry, DLS, TEM, FTIR, and X-ray diffraction analysis. Finally, the antibacterial effect of silver nanoparticles against pathogenic bacteria was investigated. Results Among the eight silver-tolerant bacteria, isolate No. 6 had high antibacterial activity and high potential in the synthesis and stabilization of silver nanoparticles. Therefore, this isolate was selected for the next experiments. The results of 16S rDNA sequencing showed that this isolate is related to Bacillus pumilus. We registered in the NCBI Bank called ROM6 with access number MW440543. The DLS and TEM analysis showed that silver nanoparticles produced by this isolate were most spherical with a size of less than 25 nm and were stable for at least 180 days. The efficiency at concentrations less than 0.9 g/l silver nitrate was over 90% and the minimum inhibition concentration of nanoparticles was determined against S. aureus, E. coli, P. aeruginosa, and A. baumannii ranging from 1.4 to 5.6 µg/ml. Conclusion We found that the bacteria residing in the gold mine have a high capacity for the synthesis of spherical and high stable silver nanoparticles with a strong antibacterial effect.

Some defects of polylactic acid (PLA), especially its poor mechanical properties, were modified using a minimum content of non-biodegradable maleated polypropylene (MAPP). To this end, first, the amount of MAPP was optimized, which was 20 wt.%. Second, MgO was used as a new catalyst to improve the exchange reactions between active groups in both polymers in a reactive blending process. Tensile and izod analyses showed that, compared to neat PLA, with a slight decrease in modulus and tensile strength, elongation at break, and impact resistance were improved in the presence of 20 and 0.1 wt.% of MAPP and MgO, respectively. This improvement in mechanical properties can be related to the exchange reactions between two polymers and the formation of PLA-MAPP block copolymers. MFI and WDCA analyses demonstrated the increase in melt flowability and surface hydrophilicity of the resulting blends, respectively. DSC analysis showed that the Tg values of both polymers approached each other in the presence of catalyst. Also, the elimination of cold crystallization of PLA and the decrease in the Tm and crystallinity of both polymers are clear reasons for the miscibility of the alloy. TEM displayed the proper dispersion of MgO nanoparticles within the polymer matrix, and in addition, the XRD test also proved the decrease in the crystallinity of both polymers and appropriate miscibility of the samples containing 20 and 0.1 wt.% of MAPP and MgO, respectively. These results can promise the design of a compound with the maximum amount of PLA for further use in various industries. [ABSTRACT FROM AUTHOR]

A TiO2@WO3/ZnO photocatalyst was synthesized and employed in the degradation of methyldiethanolamine (MDEA) (a pollutant of wastewater from gas refinery complexes) under LED light. The synthesized photocatalyst was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FT-IR). In the wastewater treatment process, a number of experiments were designed by central composite design, where parameters including the irradiation time, pH, TiO2@WO3/ZnO catalyst mass and MDEA concentration involved in the process were optimized. The significance of the individual parameters and their possible interactions were investigated using analysis of variance. The optimum values of 30 min, 9, 0.15 g, and 0.4% were obtained for the irradiation time, pH, TiO2@WO3/ZnO catalyst mass ratio and the initial concentration of MDEA, respectively. Under such conditions, the photodegradation percentage of MDEA was 86%, and a maximum photocatalytic activity with 72% degradation of gas refinery effluent was achieved in 70 min. [ABSTRACT FROM AUTHOR]

Natural gas has wide range of acid gas concentrations such as CO2 and H2S. Alkanolamines dissolved in aqueous solutions are commonly employed to scrub CO2 and H2S from natural gas. As a result, the high level of this polutant is emitted through the waste water during cleaningIn this study a novel photocatalyst, TiO2@WO3/ZnO, has been designed and fabricated. To prepare the catalyst with the highest performance, the optimized weight fraction of WO3+Zno (with 1:4 weight ratio) has been alloyed with TiO2. The results from BET and BJH indicated that the synthesized catalyst had relatively high specific surface area (10.3 m² g-1) and mesopore structure with cavities diameter of 10.9 nm. The as-synthesized photocatalyst has been employed in the alkanolamine contaminant degradation of wastewater obtained from an industrial gas refinery plant in the presence of LED light. In this regard, the degradation of alkanolamine during time was monitored using UV-Vis and fluorescence spectroscopies. The obtained results confirmed high performance of the designed catalyst in the rapid treatment of the wastewater of gas refinery effluent at very low catalyst loading of only 0.5 wt.%, thereby making it a good candidate for the catalytic purposes. Finally, a possible mechanism for catalytic degradation of alkanolamine over TiO2@WO3/ZnO was suggested. [ABSTRACT FROM AUTHOR]

In this study, a multi-objective design optimization method based on a radial basis function (RBF) model was applied to minimize the volumetric shrinkage and warpage of hip liners as an injection-molded biomedical part. The hip liners included an ultrahigh molecular weight polyethylene (UHMWPE) liner and UHMWPE reinforced with a nano-hydroxyapatite (nHA) liner. The shrinkage and warpage values of the hip liners were generated by simulation of the injection molding process using Autodesk Moldflow. The RBF model was used to build an approximate function relationship between the objectives and the process parameters. The process parameters, including mold temperature, melt temperature, injection time, packing time, packing pressure, coolant temperature, and type of liner, were surveyed to find the interaction effects of them on the shrinkage and warpage of the liners. The results indicated that the addition of nHA helps the liners to obtain more dimensional stability. The model was validated by the k-fold cross validation technique. Finally, the model revealed the optimal process conditions to achieve the minimized shrinkage and warpage simultaneously for various weights. [ABSTRACT FROM AUTHOR]