This study investigates potassium-L zeolite (K-L) as an adsorbent for the removal of thallium (Tl⁺) from aqueous solutions, focusing on the relationship between cation exchange and framework structural response. X-ray powder diffraction (XRPD), thermal analysis, and Rietveld refinements were employed to monitor structural modifications upon Tl⁺ uptake, combined with batch adsorption experiments to evaluate the removal performance. At low Tl⁺ uptake, only minor structural perturbations occur, mainly involving slight shifts in extra-framework cation positions and limited rearrangement of channel water molecules. At higher Tl⁺ concentrations, a measurable anisotropic expansion of the zeolite framework is observed, consistent with partial substitution of K⁺ by Tl⁺ and progressive modification of the hydration environment within the pores. Moreover, the crystallographic distribution of Tl⁺ differs from that of the original K⁺ cations, suggesting a specific site preference during the uptake process. Batch experiments reveal rapid uptake kinetics, with equilibrium reached within minutes, and high removal efficiency up to 99.5%. The adsorption behaviour is well described by the Langmuir model, with a maximum adsorption capacity of 631 mg g⁻¹. These findings highlight the coupling between ion exchange and structural flexibility in K-L zeolite and support its potential application for efficient thallium removal from contaminated water.

The European Union has established the necessity of securing internal supplies of Critical (CRM) and Strategic Raw Materials (SRM) to mitigate supply dependency of non-EU countries dependence and supply chain risks. In this context, the numerous small-scale Volcanogenic Massive Sulphide (VMS) deposits in the Northern Apennines, many of which have been historically exploited, may represent a potential reserve, although they require systematic re-evaluation. In this paper, we conducted whole-rock major and trace element analyses on ophiolitic basalts, with no evidence of sulphide mineralisation (i.e., barren) and mineralised samples from two previously overlooked VMS sites, Boccassuolo and Montecreto, Modena Province (Emilia-Romagna Region, Italy). The analyses confirm that the VMS-type mineralisation is associated with tholeiitic basaltic host-rocks of the External Ligurian (EL) Domain. Mineralised samples from both sites show high enrichment in base metals. They contain up to 6250 ppm Zn, meaning up to 93 times Upper Continental Crust (UCC) mean composition, and up to 4650 ppm Cu, meaning up to 176 times UCC. Montecreto mineralised samples show higher Cu/Zn ratio compared to Boccassuolo, suggesting relatively higher temperatures of the hydrothermal system, suggesting proximal conditions within the mineralised source, typically observed in modern hydrothermal vents and smokers. The petrographic investigation and qualitative mineralogic analyses conducted on Montecreto samples revealed a sulphide association of pyrite, chalcopyrite and bornite hosted within quartz veins. This study demonstrated that these abandoned historic mine sites VMS provide key insights into localised hydrothermal and mineralisation pathways, highlighting the importance of re-evaluating small-scale mining (SSM) to better understand the geochemical diversity of Northern Apennine EL ophiolites.