Processing of Aniline Aerofloat Wastewater with SBR System and Its Biodegradation Mechanism

ObjectiveThis study aimed to investigate the biodegradation effect and biodegradation mechanism of aniline aerofloat wastewater. MethodSmall-scale processing of simulated aniline aerofloat wastewater was carried out with SBR （Sequencing Batch Reactor） system; intermediate products in the process were analyzed using high-performance liquid chromatography. ResultAccording to the experimental results, the small-scale process was basically stably operated after 40 days of activation and regulation, leading to relatively ideal degradation effect on aniline aerofloat, the COD removal efficiency reached 64.3% , degradation rate of aniline aerofloat reached 93.4%, which could be applied in the treatment of mine flotation wastewater containing such pollutant. During the degradation process, pH increased from 5.83 to 6.60 and then dropped to 6.17, which might be caused by the thiocyanate ions and aniline generated in the degradation process. Aniline aerofloat mainly produced two preliminary products during the biodegradation process： aniline and a substance that was difficult to be biodegraded under aerobic conditions, which was the main reason for the relatively high COD value in effluent. Furthermore, aniline was eventually biodegraded. ConclusionThis study provided basis for the development of biological treatment of flotation wastewater in China and showed great significance for the improvement of ecological environment around the mines.

Plastic Not Welcome

Kenya seeks to eliminate plastic packaging,an environmental scourge on a national and even continental scaleJOHN Onyango lives in Nairobi,Kenya＇s capital.As he comes out of a downtown supermarket on an afternoon in October,the 61-year-old mechanic is carrying fruit in a recyclable cloth bag.

Significant influence of trace Li on the mechanical properties, corrosion behavior, and antibacterial properties of biodegradable Zn–4Cu alloys

In this work,trace Li was introduced to strengthen Zn–4Cu alloys.The results indicated that trace amounts of Li contributed to a significant increase in strength,resulting in an acceptable loss of elongation at fracture.Additionally,Li in the form of LiZn_(4) led to more intensive galvanic corrosion,which accelerated the early corrosion rate.The release of a large amount of Zn^(2+),caused by the addition of Li,affected the phase composition of the main Zn-containing corrosion products.Moreover,the inhibition effect of the alloy on Staphylococcus aureus(S.aureus)was enhanced by the addition of 0.02 wt.%Li.

In Vitro Evaluation of the Feasibility of Commercial Zn Alloys as Biodegradable Metals

In this work, three widely used commercial Zn alloys （ZA4-1, ZA4-3, ZA6-1 ） were purchased and pre- pared by hot extrusion at 200℃. The microstructure, mechanical properties, corrosion behaviors, biocompatibility and hemocompatibility of Zn alloys were studied with pure Zn as control, Commercial Zn alloys demonstrated increased strength and superb elongation compared with pure Zn. Accelerated corrosion rates and uniform corrosion morphologies were observed in terms of commercial Zn alloys due to galvanic effects between Zn matrix and α-Al phases. 100% extracts of ZA4-1 and ZA6-1 alloys showed mild cytotoxicity while 50% extracts of all samples displayed good biocompatibility. Retardant cell cycle and inhibited stress fibers expression were observed induced by high concentration of Zn^2＋ releasing during corrosion. The hemolysis ratios of Zn alloys were lower than 1% while the adhered platelets showed slightly activated morphologies. In general, commercial Zn alloys possess promising mechanical properties, appropriate corrosion rates, significantly improved biocompatibility and good hemocompatibility in comparison to pure Zn. It is feasible to develop biodegradable metals based on commercial Zn alloys.

Microstructure, Mechanical Properties, Corrosion Behavior and Biocompatibility of As-Extruded Biodegradable Mg–3Sn–1Zn–0.5Mn Alloy

The microstructure evolution and mechanical properties of biodegradable Mg-3Sn-1Zn-0.5Mn alloys were investigated by the optical microscopy, X-ray diffractometer and a universal material testing machine. The corrosion and degradation behaviors were studied by potentiodynamic polarization method and immersion test in a simulated body fluid （SBF）. It was found that the as-extruded Mg-3Sn-1Zn-0.5Mn alloy has the fine equiaxed grains which underwent complete dynamic recrystallization during the hot extrusion process, with the second phase particles of Mg2Sn precipitated on the grain boundaries and inside the grains. The tensile strength and elongation of as-extruded Mg-3Sn-1Zn-0.5Mn alloys were 244 ± 3.7 MPa and 19.3% ± 1.7%, respectively. The potentiodynamic polarization curves in SBF solution indicated the better corrosion resistance of the as-extruded Mg-3Sn-1Zn-0.5Mn alloy in the SBF solution. Immersion test in the SBF solution for 720 h revealed that the corrosion rate of as-extruded Mg-3Sn-1Zn-0.5Mn alloy was nearly 4±0.33 ram/year. The hemolysis rate of as-extruded Mg-3Sn-1Zn-0.5Mn alloy was lower than the safe value of 5% according to ISO 10993-4. As-extruded Mg-3Sn- 1Zn-0.5Mn alloy showed good biocompatibility after being implanted into the dorsal muscle and the femoral shaft of the rabbit, and no abnormalities were found after short-term implantation. It was revealed that the as-extruded Mg-3Sn-1Zn-0.5Mn alloy is a promising material for biodegradable implants, which possesses an interesting combination of preferred mechanical properties, better corrosion resistance and biocompatibility.

Processing of a Novel Zn Alloy Micro-Tube for Biodegradable Vascular Stent Application

In recent years, zinc based alloys as a new biodegradable metal material aroused intensive interests. However, the processing of Zn alloys micro-tubes （named slender-diameter and thin-walled tubes） is very difficult due to their HCP crystal structure and unfavorable mechanical properties. This study aimed to develop a novel technique to produce micro-tube of Zn alloy with good performance for biodegrad- able vascular stent application. In the present work, a processing method that combined drilling, cold rolling and optimized drawing was proposed to produce the novel Zn-5Mg-1Fe （wt%） alloy micro- tubes. The micro-tube with outer diameter of 2.5 mm and thickness of 130 μm was fabricated by this method and its dimension errors are within 10 μm. The micro-tube exhibits a fine and homogeneous microstructure, and the ultimate tensile strength and ductility are more than 220 MPa and 20% respectively. In addition, the micro-tube and stents of Zn alloy exhibit superior in vitro corrosion and expansion performance. It could be concluded that the novel Zn alloy micro-tube fabricated by above method might be a promising candidate material for biodegradable stent.

Simultaneous Improvements of Thermal Stability and Mechanical Properties of Poly(propylene carbonate) via Incorporation of Environmental-friendly Polydopamine

Inspired by the photoprotection, radical scavenging of melanin together with versatile adhesive ability of mussel proteins, polydopamine（PDA） nanoparticles were successfully prepared and incorporated into environmentally friendly polymer, poly（propylene carbonate）（PPC） via solvent blending. The prepared composites exhibited excellent thermal stability in air and nitrogen atmosphere and extraordinary mechanical properties. The composites displayed eminent increase of temperature at 5% weight loss（T5%） by 30-100 K with 0.3 wt%-2.0 wt% loadings, meanwhile, the tensile strength and Young＇s modulus were significantly improved from 11.5 MPa and 553.7 MPa to 40.5 MPa and 2411.2 MPa, respectively. The kinetic calculation indicated that improvement of T5% is presumably derived from suppressing chain-end unzipping. The glass transition temperature（Tg） of the PPC/PDA composites increased by 8-10 K. This is probably due to hydrogen bonding interaction since the abundant proton donors along PDA chains would interact with proton acceptors like C = O and C―O―C in PPC which would cause restriction of segmental motion of PPC chains.