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Nanotechnology is nowadays very much successful in producing specifically functionalized nano-sized particles. In this work, copper nanoparticles were prepared by reduction method which is greener and environmentally suitable, cheap and best as compared to other conventional methods, particularly in the context of COVID in globalized world. The formation and size of copper nanoparticles was evidenced by the X-ray diffraction and transmission electron microscopy. The very high surface area of 35–50 m²/gm and very small crystallite sizes of 5–15 nm of these metal nanoparticles is mainly responsible for their effective involvement in removal of carbon dioxide gas as one of major hazardous pollutants from the environment. This chapter, as its main objective, mainly focuses on utility of nano technology and its beneficiary in creating a sustainable environment in economic world. Apart from laboratory experimental procedure and characterizations for preparation of copper nanoparticles, appropriate research methods such as simple statistical, econometric tools and mathematical tools have been used for economic analysis. However, as major findings of the results, developed countries have been successful in maintaining a sustainable human development, in spite of having higher per capita income (PCI) growth as compared to the role of developing countries with lower PCI in this global world.

Purpose – In this study, the possibility of the application of rice husks for adsorbing Mn(II) ion in the water phase has been studied.

Design/Methodology/Approach – Experimental studies have been initiated by preparing activated carbon from rice husks. The activation of rice husks was done using both physical and chemical treatment methods through heating at 110 °C and washing with citric acid activator at 0.2 M, 0.4 M, and 0.6 M. The adsorption tests were conducted as two part tests: preliminary and primary. The preliminary test was conducted to choose the best condition of four independent variables, i.e., contact time (0–120 minutes), activator concentrations (0.2, 0.4, and 0.6 M), initial Mn(II) concentrations (10, 20, 50, 100, 200, and 400 mg/L), and adsorption temperatures (30, 47, and 67 °C).

Findings – By identifying the substituted groups using Fourier Transform Infrared Spectroscopy after activation with citric acid, it was found that the highest transmittance percentage was present in activated carbon with 0.2 M of citric acid. The best adsorption capacity and efficiency was 13.87 mg/g and 79.60%, respectively, which were obtained at 200 mg/L initial concentration with a 0.2 M citric acid concentration for 120 min contact time at 47 °C. These results lead to a conclusion that rice husks after activation with citric acid can be applied as an adsorbent for Mn(II) adsorption in the water phase.

Research Limitations/Implications – The activated carbon produced was only applicable for the adsorption of Mn(II) ions from the water phase, but not applicable for the adsorption of other heavy metals ions.

Practical Implications – Rice husks were potentially prepared as an adsorbent for Mn(II) ion adsorption in the water phase that was low cost, environmental friendly, and easy to prepare.

Originality/Value – Activated carbon prepared from biomass was mostly carried out using acids at high concentrations while the study was conducted using weak acids (citric acid) at low concentrations.