Life cycle assessment of chitosan modified Ni–Fe layered double hydroxide for arsenic(iii) sequestration in aqueous medium: comparison of the impacts of adsorbent recycling, instrument use and source of energy

Abstract

Evidence of arsenic in potable water is a huge global concern for human well-being. For the adsorption of arsenic from groundwater, a promising material Ni–Fe layered double hydroxide modified using chitosan (NFC) was synthesized in a lab-scale study. In the original research, two pollutant-adsorbent contact approaches, i.e., magnetic stirrer and ultrasonicator, were utilized to accomplish maximum pollutant removal, and the latter was found to give better results. The current work utilized OpenLCA software and the ReCiPe Midpoint (H) (v1.02) approach to conduct a Life Cycle Assessment (LCA), which assesses and compares the environmental effects of both techniques. The synthesis of 1 kg of NFC and treatment of 1000 L of water contaminated with As(III) from a 50 mg L⁻¹ initial concentration to its WHO acceptable limit served as the basis for evaluations. Environmental effects of handling used materials were taken into account. Furthermore, environmental impacts arising from recycling of the adsorbent were also determined. According to the LCA analysis, the use of electricity and chemicals mainly nickel and liquor ammonia were the main causes of the environmental effects, especially in the global warming potential, human toxicity potential, freshwater ecotoxicity potential, and marine ecotoxicity potential categories. The manufacture of the nanomaterial was the most energy-intensive step of the process, which indicates that energy consumption needs to decrease during scaling up. As electricity consumption is optimized for large-scale operations, there is potential for an increased relative contribution of chemicals to environmental impacts. Furthermore, two distinct electrical sources were chosen to perform sensitivity analysis. The environmental effects of the current development process and application were contrasted with those of granular activated carbon (GAC) and it was found to have fewer negative effects than LDH. It can be concluded that energy and chemical optimization should take precedence in the manufacture of future materials.