Cleaner production of garnet sand for environmental abatement

An improved process for the removal of surface coatings of garnet sand that create environmental hazard through dust produced during blasting/water-jet cutting applications is discussed in this paper. The process involves attrition scrubbing in the presence of surfactants and desliming by hydrocyclones. Decontamination of the surface was measured in terms of turbidity of the resultant water expressed in Nephelometric Turbidity Units (NTU). The turbidity of the resultant water was brought down to 30-60 NTU from the initial value of above 1,400 NTU by the above process. The qualitative improvement in surface cleanliness was also expressed in terms of change in surface energy of garnet grains as determined by contact angle measurements before and after the process. The conceptual flow sheet of the process along with the methodology for the estimation of surface contamination of garnet was discussed. Among the various detergents tried as scrubbing aids, the extract from pericarp (outer shell) of soapnut from Sapindus emarginatus was found to be most effective.