The efficient utilization of natural metal resources and the promotion of resource circulation through urban mining (recycling) are becoming increasingly important for achieving a circular economy. As a pretreatment of smelting, physical separation is essential to separate valuable minerals and metals from ores and waste products, respectively. The author has been conducting research on the separation of valuable minerals from ores using flotation, a type of physical separation technology. This paper introduces case studies on the improvement of flotation processes in natural mining development by the author and discusses the challenges in applying flotation to urban mining development.

Due to recent global concerns about plastic waste and the growing interest in a circular economy, recycling methods for polyester materials are attracting increasing attention. This article focused on the chemical recycling methods for PET, which is the most widely produced type of polyester. Recent examples of research on chemical recycling of mixed polyester materials were highlighted.

In August 2024, the Fifth Basic Plan for Recycling was approved by the Cabinet and “transition to a circular economy” was set as a national strategy. Currently, efforts for the supply of recycled materials and other activities through arteriovenous cooperation have only just begun. Meanwhile, a draft ELV regulation has been proposed in Europe that would make the use of recycled plastics in automobiles mandatory, which will inevitably affect the manufacturing industry in Japan. The Ministry of the Environment launched the “Industry-Government-Academia Consortium for Buildinga Market for Recycled Plastics for the Automotive Industry”, and compiled the “Action Plan for Building a Market for Recycled Plastics for the Automotive Industry” in March 2025. Biomass composite materials such as cellulose/CNF are expected to reduce plastic usage, and are expected to be applied to automobiles in parallel with the construction of the recycled plastics market.

Packaging materials generate the highest plastic waste of all plastic applications. Therefore, packaging plastic waste issues must be addressed on a global basis. Regulations have been enacted in many countries and industrial associations and researchers are investigating recycling processes, materials, and hygiene. The purpose of this review article is to introduce the trends of national laws, industrial activities for reduction of plastic waste in packaging, and some studies for material recycling with colorants.

2-(4-(N,N-diphenylamino)phenyl)-9-(1-pyrenyl)tryptanthrin (T2PhNPh₂9Py), which has pyrene introduced at the 9-position of 2-(4-(N,N-diphenylamino)phenyl)tryptanthrin (T2PhNPh₂), where aggregation-induced emission (AIE) is observed, was synthesized and its photophysical properties were investigated. The aggregation properties of T2PhNPh₂9Py were studied using a mixture of THF (good solvent) and water (poor solvent) to create an aggregate state by increasing the water content. When excited at 340 nm in the pyrene absorption band of the energy donor (D) in fluorescence resonance energy transfer (FRET), at 0% water content, weak D-derived pyrene fluorescence was observed near 450 nm, but with increasing water content, the pyrene fluorescence gradually disappeared and the energy acceptor (A)-derived T2PhNPh₂ fluorescence increased near 650 nm. Therefore, T2PhNPh₂9Py was observed to have a combination of intra- and intermolecular FRET and AIE properties.