Prospective life cycle assessment for sustainable synthesis design of organic/inorganic composites for water treatment

Abstract Considering a sustainable approach to the production of novel materials used for water treatment processes, this study presents the development and implementation of prospective life cycle assessment (LCA) as an environmental support tool to identify and quantify the potential environmental impacts during the design, synthesis and testing of innovative organic/inorganic composites for heavy metal ions removal. This research explores two layer-by-layer syntheses routes to develop silica//polyethylenimine (PEI) microparticles with similar characteristics but different efficiencies in the sorption of Cu2+ ions from water and it investigates how scenario-based LCA may be used to forecast potential environmental impacts and sustainability hot spots during the design and synthesis phases. Furthermore, the study explores different approaches to critical LCA elements (e.g. functional units, system limits, design scenarios, and uncertainty analysis). The LCA uses a cradle-to-gate approach for the laboratory scale synthesis and testing processes of inorganic/organic composites, for which chemicals and energy production processes were considered in the life cycle inventory (LCI). Life cycle impact assessment (LCIA) was performed with ReCiPe 2016 at midpoint in 3 steps: at first, initial environmental profiles were generated to evaluate the environmental impacts of the two silica/polymer composites syntheses routes; secondly 3 alternative eco-design scenarios were investigated for replacing some of the chemicals and finally, a scenario-based sensitivity analysis was performed to investigate how inventory data impacts the environmental profiles. The environmental profiles of the two syntheses routes have shown that the B synthesis strategy leads to lower environmental impacts, with the exception of the toxicity related categories, where the initial PEI complexation with Cu2+ ions leads to higher environmental impacts. The eco-design scenarios have demonstrated that by changing the silica support particle with inert quartz microparticles would greatly increase impacts, while changing the initial PEI complexation ion from Cu2+ to another metal would decrease the toxicity related impacts. A sensitivity analysis has recorded significant coefficients of variability for 10 out of 18 impact categories, meaning high uncertainty for these impact values and has identified the silica source as the most important variability contributor.