The excessive amount of global plastic produced over the past century, together with poor waste management, has raised concerns about environmental sustainability. Plastic recycling has become a practical approach for diminishing plastic waste and maintaining sustainability among plastic waste management methods. Chemical and mechanical recycling are the typical approaches to recycling plastic waste, with a simple process, low cost, environmentally friendly process, and potential profitability. Several plastic materials, such as polypropylene, polystyrene, polyvinyl chloride, high-density polyethylene, low-density polyethylene, and polyurethanes, can be recycled with chemical and mechanical recycling approaches. Nevertheless, due to plastic waste’s varying physical and chemical properties, plastic waste separation becomes a challenge. Hence, a reliable and effective plastic waste separation technology is critical for increasing plastic waste’s value and recycling rate. Integrating recycling and plastic waste separation technologies would be an efficient method for reducing the accumulation of environmental contaminants produced by plastic waste, especially in industrial uses. This review addresses recent advances in plastic waste recycling technology, mainly with chemical recycling. The article also discusses the current recycling technology for various plastic materials.

Oxygen transfer enhancement in aquaculture was investigated using a low-cost fine-bubble spray system operated under controlled hydrodynamic conditions. Experiments were conducted under oxygen-depleted conditions (initial DO = 2.4 mg L⁻¹), and oxygen transfer kinetics were evaluated using the dynamic method. The dissolved oxygen concentration increased to 6.2 mg L⁻¹ within 1 h, corresponding to a net oxygen transfer of 9.55 ± 0.46 g. The volumetric mass transfer coefficient (kLa) was determined to be 1.44 h⁻¹ (R² = 0.97), while the specific oxygen transfer efficiency (SOTE) reached 76.4 ± 7.8 gO₂ kWh⁻¹. Dimensionless analysis (Re ≈ 2 × 10⁴, Sc ≈ 500, Sh ≈ 682) indicates a turbulent, convection-dominated transport regime. Biological observations showed a 43% increase in fish growth under spray-assisted conditions, indicating improved oxygen availability. The observed oxygen transfer enhancement was primarily associated with hydrodynamic interfacial area generation rather than diffusion-limited transport. The low-power configuration and simplified system design suggest potential applicability for decentralized aquaculture operations. The proposed approach also provides an engineering framework for evaluating low-cost aeration technologies under aquaculture operating conditions.

Dissolved oxygen (DO) management is a primary challenge in intensive aquaculture, where conventional aeration often suffers from high energy costs and low efficiency in decentralized systems. Oxygen transfer kinetics were investigated under oxygen-depleted conditions (initial DO = 2.4 mg L⁻¹) using the dynamic method. The system's performance was characterized through the volumetric mass transfer coefficient (kLa), Specific Oxygen Transfer Efficiency (SOTE), and dimensionless analysis (Reynolds, Schmidt, and Sherwood numbers). After 1 hour of operation, the DO concentration increased to 6.2 mg L⁻¹, achieving a net oxygen transfer of 9.55 ± 0.46 g. The system yielded a kLa of 1.44 h⁻¹ (R² = 0.97) and a SOTE of 76.4 ± 7.8 gO₂ kWh⁻¹. Dimensionless analysis (Re ≈ 2 x 10⁴, Sc ≈ 500, Sh ≈ 682) confirms that oxygen transfer is governed by hydrodynamic-induced interfacial area generation rather than molecular diffusion. Biological validation demonstrated that fish (catfish) grown under nanobubble-assisted conditions achieved a 43% higher growth rate over 17 days compared to non-assisted groups. These findings demonstrate that hydrodynamically controlled nanobubble spray systems provide an energy-efficient and scalable solution for decentralized aquaculture aeration.