Green finance in circular economy: a literature review

Developing markets are using sustainable development potential to reach zero-carbon goals. Due to the limitation of natural resources, companies need to use environmentally friendly manufacturing to develop a circular economy (CE). Green finance (GF) and the CE are linked in a systematic and complex approach; therefore, it was essential to employ the coupling coordination-level framework to explain their relationship and feedback. Any study linking green financing and CE together has been found. The objective of this research is to explore this twofold domain and determine its main characteristics. To address this objective, a comprehensive review of the literature was conducted, supplemented by a bibliometric analysis. The results confirm that GF has the potential to help society, sustainability, and the prevention to climate shifts, investing in the CE. There are many hurdles to overcome, including inadequate knowledge about CE and GF, ambiguous definitions, a lack of coherence between legal frameworks on CE and green financing, unclear laws, and a lack of financially viable motivation for investors and financial institutions that are ready to promote in sustainability. This study explores CE and GF domains. Managers may readily increase their understanding of methods, strategies, and technical solutions beneficial to assist their operations toward a green economy depending on various CE and GF elements. Finally, based on a categorization of GF types, the assessment identifies future investment potential consequences of green financing in the CE.

Highly ordered CaO from cuttlefish bone calcination for the efficient adsorption of methylene blue from water

The aim of this study is to synthesize cheap and highly ordered CaO from cuttlefish bone (CFB) as a green alternative to conventional adsorbents such as activated carbon. This study focuses on the synthesis of highly ordered CaO via calcination of CFB, at two different temperatures (900 and 1000°C) and two holding times (0.5 and 1 h), as a potential green route for water remediation. The as-prepared highly ordered CaO was tested as an adsorbent using methylene blue (MB) as a model compound for dye contaminants in water. Different CaO adsorbent doses (0.05, 0.2, 0.4, and 0.6 g) were used, keeping the MB concentration fixed at 10 mg/L. The morphology and crystalline structure of the CFB before and after calcination was characterized via scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, while the thermal behavior and surface functionalities were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy, respectively. Adsorption experiments using different doses of CaO synthesized at 900°C for 0.5 h showed an MB removal efficiency as high as 98% by weight using 0.4 g (adsorbent)/L(solution). Two different adsorption models, the Langmuir adsorption model and the Freundlich adsorption model, along with pseudo-first-order and pseudo-second-order kinetic models, were studied to correlate the adsorption data. The removal of MB via highly ordered CaO adsorption was better modeled by the Langmuir adsorption isotherm giving (R² =0.93), thus proving a monolayer adsorption mechanism following pseudo-second-order kinetics (R²= 0.98), confirming that chemisorption reaction occurs between the MB dye molecule and CaO.