Many industrial sectors use in their processes quartz and/or quartz-containing raw materials. Consequently, the occupational environments of these companies may contain appreciable quantities of this pollutant. However, quartz cannot be replaced in most cases.
The respirable fraction of crystalline silica (RCS) is made up of particles fine enough to remain suspended in the air for a long time and penetrate to the pulmonary alveoli, the last receptacles where oxygen and carbon dioxide exchange. The natural defense mechanisms of the human body allow us to eliminate most of the inhaled respirable dust. However, in cases of prolonged exposure in environments with a high concentration of RCS, its elimination from the lungs becomes difficult; its accumulation in the pulmonary alveoli can cause the disease called silicosis, causing serious irreversible effects. In addition, the International Agency for Research on Cancer (IARC) proposed in 1997 and endorsed in 2012 the classification of the SCR as a Group 1 Carcinogen: “Carcinogenic to humans”. This classification means that “there is sufficient evidence in humans for the carcinogenicity of crystalline silica in the form of quartz or cristobalite”.
Numerous studies suggest that the toxicity of quartz is conditioned by the surface chemistry of the quartz particles and, in particular, by the density and abundance of silanol groups. The effectiveness of the addition of substances like nano-alumina, aluminium lactate, and organosilanes to block these groups was studied in the SILICOAT project, showing that the toxicity of the RCS contained in the wet-processed raw materials of the traditional ceramic industries can be virtually nullified. This effect was obtained by adding an additive to the ceramic compositions, which coats the quartz surface so that it becomes no longer toxic. This technology was found to be technically and economically feasible for traditional ceramics.
From these results, project SILIFE extrapolated these good results to other industrial sectors which use quartz in their dry processes. The main objective consisted of producing commercial quartz powders that show very little or no RCS toxicity. To do this, a pilot plant for treatment of commercial quartz powders was designed. The treated quartz produced in this plant was verified by means of industrial trials performed by several end users from different industrial sectors with good results.