Polyethylene terephthalate (PET), as one of the most indispensable synthetic organic compounds with high strength and transparency properties, can be widely used for textile and food packaging. With the increasing demand for PET production, the recycling of discarded PET has attracted great interest. In this work, we first proposed ethylene glycol (EG) dispersions of highly dispersed Fe3O4 nanoparticles, which were prepared through a co-precipitation route, as efficient and recoverable nanocatalysts for a PET chemical depolymerization achieved by a glycolysis reaction. The as-prepared Fe3O4 nanoparticles have an average size of 11 nm and can be stably dispersed in EG for up to 6 months. This glycolysis process was optimized in terms of catalyst concentrations, EG dosages, degradation temperature, and reaction time. Furthermore, the possible reaction mechanism of PET glycolysis using Fe3O4 as a catalyst was presented. More importantly, 100% PET conversion was achieved, and the bis(2-hydroxyethyl) terephthalate (BHET) yield reached more than 93% under optimal conditions (Fe3O4/PET = 2%, EG/PET = 13, 210 °C 30 min) even after three cycles. The Fe3O4 nanocatalysts are relatively stable during recycling and have great application prospects in chemocatalysis for future research.

Colloidosomes as Pickering emulsion microcapsules are expected to serve various applications, including encapsulation of drugs and loading of functional materials. Normally, when using colloidosomes for drug encapsulation, the latex particles as shell materials need to be mixed with drugs before the assembly process. However, this procedure may cause aggregation of latex particles, thereby resulting in disordered assembled shells or a low loading efficiency. Herein, we propose a three-fluid nozzle spray drying process to efficiently assemble latex particles of P(styrene (St)-co-butyl acrylate (BA)) into colloidosomes. The three-fluid nozzle spray drying equipment allows for the preparation for drug encapsulation without advance mixing of drug and shell materials. This strategy enables the construction of colloidosomes with uniform and controllable pores and the loading of functional materials. The effects of the compressed air flow rate, inlet temperature, feed rate, and solid content were explored, revealing the formation mechanism of colloidosomes during the spray drying process. Doxycycline hydrochloride (DH) was encapsulated in colloidosomes for controllable release, and the sustained release time is up to 100 h. The release rate can be adjusted by varying the glass transition temperature (T g) and size of latex particles. Furthermore, Fe3O4 nanoparticle (NP)-loaded colloidosomes were constructed by this strategy. The magnetic response intensity of colloidosomes can be modulated by varying the amount of Fe3O4 NPs. The anticancer drug encapsulation and loading of other functional particles were also explored to expand applications.

Colloidosomes are widely applied in drug delivery systems on account of their outstanding biocompatibility and stimuli response. Herein, a novel and environmentally friendly approach is presented for efficiently fabricating colloidosomes by high-gravity technology, which is not only favorable for controllable latex particle size and large-scale production but also makes it avoidable to use a great deal of organic solvents. First, the latex particles as shell materials with a range of 47–62 nm are controllably prepared using high-gravity-assisted pre-emulsification for emulsion polymerization. Because of this pre-emulsification, the polymerization time is greatly shortened from 4 to 1 h, and the mean particle diameter is reduced by about 29%. In addition, the self-assembly of latex particles forming into colloidosomes is achieved using high-gravity technology. Compared with the preparation process in a conventional high-speed shearing machine, the colloidosomes prepared with the high-gravity self-assembly process have a decreased size of 3.5 to 2 μm and a narrower size distribution. Furthermore, an anticancer drug of doxorubicin hydrochloride is in situ encapsulated into the colloidosomes, displaying excellent controllable release properties.