A microencapsulation process of liquid mercury by sulfur polymer stabilization/solidification technology. Part I: Characterization of materials; Proceso de microencapsulación de mercurio líquido mediante tecnología de estabilización/solidificación con azufre polimérico. Parte I: Caracterización de materiales

European Directives consider mercury a priority hazardous substance due to its adverse effects on human health and the environment. In response to environmental concerns, a microencapsulation process has been developed within the European LIFE program as a long-term storage option for mercury. This process leads to the obtainment of a stable concrete-like sulfur matrix that allows the immobilization of mercury. The final product, in the form of a solid block containing up to 30 % Hg, exhibits excellent mechanical properties (compressive strength 53-61 MPa and flexural strength 7-10 MPa), low porosity (0.57 % PHe), very low total pore volume (0.63x10 -2 cm3 g-1), and extremely low permeability (coefficient of water absorption by capillarity 0.07 g cm-2). Toxicity characteristic leaching tests reveal a mercury concentration in leachates well below the 0.2 mg L-1 set out in US EPA Land Disposal Restrictions (LDRs). The values of mercury vapor emissions of final products were lower than those of cinnabar and metacinnabar.