Mechanical recycling of polylactide, upgrading trends and combination of valorization techniques

The upcoming introduction of polylactides in the fractions of polymer waste encourages technologists to ascertain its valorization at the best quality conditions. Mechanical recycling of PLA represents one of the most cost-effective methodologies, but the recycled materials are usually directed to downgraded applications, due to the inherent thermomechanical degradation affecting its mechanical, thermal and rheological performance. In this review, the current state of mechanical recycling of PLA is reported, with special emphasis on a multi-scale comparison among different studies. Additionally, the applications of physical and chemical upgrading strategies, as well as the chances to blend and/ or composite recycled PLA are considered. Moreover, the different valorization techniques that can be combined to optimize the value of PLA goods along its life cycle are discussed. Finally, a list of different opportunities to nurture the background of the mechanical recycling of PLA is proposed, in order to contribute to the correct waste management of PLA wastes

Effects of organic nutrients and growth factors on biostimulation of tributyltin removal by sediment microorganisms and Enterobacter cloacae

Natural attenuation can reduce contamination of tributyltin (TBT), but persistence of the xenobiotic can cause long-term issues in the environment. Biostimulation is used to accelerate biodegradation. This study investigated the ability of individual organic nutrients and growth factors to enhance TBT biodegradation by sediment microorganisms (SED) and Enterobacter cloacae strain TISTR1971 (B3). The supplements that produced high biomass yield were selected for degradation enhancement. For TBT degradation at initial concentration of 0.1 mg/l, negative or limited degradation was observed in some selected supplements indicating that increasing the biomass did not necessarily promote degradation. Consequently, the addition of nutrients was expected to increase both dioxygenase activity and the degrader population. At different concentrations of supplements, a mixture of succinate/glycerol showed the highest removal for SED which reduced TBT by 77%, 75%, and 68% for 0.1×, 1×, and 10× supplement concentration, respectively. For B3, the addition of succinate showed degradation of 49% (0.1×), 75% (1×), and 77% (10×). Most nutrients and amino acids had an inhibitory effect at 1× or 10× levels. Excess amount of the nutrients added can inhibit the initial degradation of TBT. Therefore, TBT biostimulation requires supplements that increase the capability of TBT degraders at an appropriate amount