Geochemical processes and sensitivity analysis of flow velocity and column depth for effective nickel removal

Eliminating heavy metals from the environment is crucial, even in low concentrations, due to their high toxicity, persistence, and tendency to accumulate in living organisms, posing serious threats to human health and ecosystems. This study investigates the geochemical processes that govern nickel (Ni) removal in Filtralite and evaluates how different parameters influence its effectiveness. The interaction between contaminated water and Filtralite-forming minerals results in a rapid increase in pH, leading to the immediate precipitation of teophrastite (Ni(OH)₂) at the initial filtration stages. However, as water continues to interact with Filtralite, its capacity to maintain high pH levels declines over time, reducing the Ni removal efficiently. In regions with a Mediterranean climate and considering an infiltration system that manages runoff from 10 % of the urban landscape, a filter layer of 200 mm combined with flow velocities below 828 mm/h has been found to optimize metal retention. Under these conditions, more than 90 % of the filter's total Ni-holding capacity is effectively used, and replacement is expected to be necessary roughly every three years. Additionally, tests simulating intense rainfall confirm that the eliminated Ni remains securely bound within the filter media, reinforcing Filtralite's reliability as a filtration material for infiltration systems. This research contributes to a better understanding of the geochemical mechanisms involved in metal removal and lays the groundwork for future design considerations in Filtralite-based filtration applications.