Diatomite is well known to remove particulate matter for a broad range of applications due to diatom skeleton structures. Hydrothermally treated diatomite has been demonstrated to be a feasible pathway to produce advanced materials for the removal of aqueous heavy metal ions. However, single-synthesis routes to obtain altered diatomite for simultaneous removal of dissolved and particulate contaminants are still missing. Therefore, hydrothermal experiments at pH 12.8 ([KOH] = 0.1 M), and T = 100 °C and different added Al concentrations (0 mM ≤ [Al] ≤ 11 mM) were conducted. Results reveal that in comparison with previous experiments (Höllen et al. in J Mater Sci Eng B 2(10):523–533, 2012) using less alkaline solutions slower dissolution of diatomite is triggering the formation of nanosized spherical particles (NSP) in the presence of diatom skeleton relicts. NSP ranged between 10 and 50 nm in size and were located within the micropores of the diatoms (100–200 nm). TEM-SAED analyses of NSP indicated nanocrystalline phases with distinct lattice planes of 0.45 and 0.26 nm, which could not be attributed to common aluminosilicates. In accordance with the small crystal size, no X-ray diffraction peaks occurred in the bulk reaction product using powder XRD analyses. Metal ion removal experiments at ambient temperature indicated its high removal capacities for aqueous Cu2+, Pb2+ and Zn2+ ranging from 10 to 99 % (e.g., ion sorption capacities of about 0.02–0.2 mval/g). The synthesized product was also successfully tested for its metal ion removal behaviour using a mine drainage solution containing Cd2+, Pb2+, Zn2+ and Sr2+. The developed synthesis path yields a hierarchically structured material based on combined micropores (about 100 nm) from the diatoms and NSP with nanopores (1–5 nm) which is promising for large-scale production to simultaneously remove dissolved and particulate contaminants from aqueous solutions.
- Heavy metal ion removal
- Hierarchically structured material
- Hydrothermal alteration
- Nanosized spherical particles
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry