Lifecycle assessment of environmental and economic impacts of nano-iron synthesis process for application in contaminated site remediation

Abstract

Nano-scale zero-valent iron (nZVI) is the main nanomaterial used in environmental remediation processes. Its wide application is due to its various characteristics, such as high specific surface area, low toxicity, and low production costs. However, as with any remediation technique, the use of nanomaterials can also cause undesirable impacts on human health and the environment. Thus, this study aims to characterize and analyze the environmental and economic impacts of the production methods of nZVI used in the remediation of contaminated sites. For this purpose, an evaluation of the lifecycle of these environmental (LCA) and economic (LCC) aspects was performed for three methods of nZVI synthesis: milling, liquid chemical reduction with sodium borohydride, and chemical reduction with hydrogen gas. For the analysis of environmental impacts, a lifecycle assessment tool called Simapro was used. This LCA was performed using the ecoinvent database and the Impact 2002 + method, that is, using four impact categories (climate change, ecosystem quality, resources consumed, and human health). For the economic aspects, an analysis of the lifecycle costs (LCC) was carried out, and a specific method was adopted in Simapro, evaluating the internal and external costs. The limits of the system included the stages of raw material extraction and manufacturing, not considering the use of nZVI after its production. The functional unit considered was the kg of nZVI produced. The results indicated that the method involving reduction with sodium borohydride will create the less significant environmental impacts, while the hydrogen gas reduction method results in greater environmental impacts. The LCC demonstrated that the milling method results in lower costs compared to the hydrogen gas reduction method. Thus, it can be said that the methods with the greatest environmental and economic benefits are the reduction with sodium borohydride method and the milling method. These methods are simple and with lower impacts and costs compared to the hydrogen gas reduction method. In this way, the application of the LCA and LCC assists in the evaluation of the environmental and economic performance of the production methods, promoting a broad analysis of the main elements that contribute to the environmental and health impacts of each method.