The efficacy of sono-electro-Fenton process for removal of Cefixime antibiotic from aqueous solutions by response surface methodology (RSM) and evaluation of toxicity of effluent by microorganisms

The increasing use of antibiotics by humans and their persistence in the environment leads to the development of drug resistance, which is nowadays considered as an environmental problem. The aim of this study was to determine the efficacy of sono-electro-Fenton process for removal of Cefixime antibiotic from aqueous solutions by Response Surface Methodology (RSM) and to evaluate the toxicity of effluent by microorganisms. In the present study, the degradation of synthetic wastewater containing Cefixime was investigated in a reactor (with a useful volume of 1 L) located in the chamber of the ultrasonic device. The effects of pH, hydrogen peroxide concentration, voltage, initial antibiotic concentration, and electrolysis time were investigated using the Box-Behnken model, and the optimal conditions for elimination were obtained by analyzing the variance. The performance of the electro-Fenton and ultrasonic process was evaluated separately and in combination under optimal conditions. Toxicity of inlet and outlet was tested by Escherichia coli and Staphylococcus aureus, and growth inhibition percentage was calculated. The intermediates were determined by LC-MS with the lowest molecular mass. The results showed that the sono-electro-Fenton process under optimum conditions, including pH of 3.07, hydrogen peroxide concentration of 0.85 mL/L, voltage 15 V, initial antibiotic concentration 10.4 mg/L and electrolysis time of 81.5 min has a percentage of removal of 97.5%. Under optimum conditions, the percentage of removal by electro-Fenton and ultrasonic separately were 81.7% and 9%, respectively, and in the hybrid process of sono-electro-Fenton, the percentage of removal increased to 97.5%. The results also showed that the biological toxicity of the outlet effluent from the sono-electro-Fenton process, compared to the inlet solution, was significantly reduced. So, we conclude that the Sono-electro-Fenton process has a significant effect on the removal of Cefixime from aqueous solutions and can also significantly reduce the biological toxicity of the effluent.     

Biodegradable polymers by reactive blending trans-esterification of thermoplastic starch with poly(vinyl acetate) and poly(vinyl acetate-co-butyl acrylate)

Wheat starch was reacted with poly(vinyl acetate) and with poly(vinyl acetate-co-butyl acrylate) in an internal mixer at 150 °C in the absence of catalyst, and in the presence of sodium carbonate, zinc-acetate and titanium(IV) butoxide. The resulted blends were pressed into film and characterized by ¹H NMR-¹³C NMR spectroscopy, differential scanning calorimetry (DSC), mechanical testing, dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and water absorption. Partial trans-esterification took place between wheat starch and the polymers. The blends appeared as homogenous, translucent films with one glass transition temperature range, between that of starch and of the polymer. The presence of wheat starch in the blends improved the mechanical strength of the polymers, although elongation at break severely decreased, which is disadvantageous for processability. Zinc-acetate improved the tensile strength of the blends of starch with PVAC, while all catalysts resulted in an increase in strength of the blends of starch with poly(vinyl acetate-co-butyl acrylate) compared to the strength of the blends without catalyst. Water absorption of wheat starch/copolymer blends was between 150% and 250%, higher than that of the blends with the homopolymer, which was between 100% and 150% after soaking in water. The onset temperature of thermal decomposition was between 290 and 300 °C for all the blends, although the presence of sodium carbonate resulted in a decrease in the onset temperature of thermal decomposition by about 60 °C.     

Elevated ductility,optical, and air barrier properties of poly (butyleneadipate‐co‐terephthalate) bio‐based films via novel thermoplastic starch feature

It is important to develop high performances biodegradable polymers to eliminate the “white pollution” evoked by petroleum‐based polymer. Thermoplastic starch (TPS) with nano‐ellipse configuration was fabricated to reinforce the performances of poly (butylene adipate co‐terephthalate) (PBAT) biocomposites. Effects of tartaric acid (TA) (0.5% wt) on the structure of TPS and compatibility for PBAT were evaluated by Fourier‐transform infrared spectroscopy (FTIR), viscosity and rheological measurement, dynamic mechanical analysis (DMA) and scanning electron microscope (SEM), respectively. They revealed that TA reduced the molecular weight of starch and shear viscosity of TPS were beneficial for TPS dispersing in PBAT matrix with 184‐nm averaged diameter. PBAT/TPS‐TA (70:30 wt%) biocomposite films were blew with different blow‐up ratio. The morphology of films presented that nano‐TPS‐TA wrapped in the PBAT matrix and deformed from ball to capsule feature without agglomeration. Compared with those of PBAT film, the increment in elongation at break of PBAT/TPS‐TA film was 100%. The air permeability and UV‐VIS transmittance of PBAT/TPS‐TA films decreased from 6.92 × 10^?9 to 3.72 × 10^?9 cm³·cm·cm^?2 s^?1 Pa^?1 and 47.6% to 23.5%, respectively. This study proposed a facile approach to fabricate low‐cost PBAT films with significant improved mechanical, optical, and air barrier properties for commercial application. Mechanism for nanoparticles of TPS‐TA motivated the elevated performances was proposed, synchronously.