Influence of kaolin clay on mechanical properties and on the structure formation processes of white ceramics with inclusion of hazardous laundry sewage sludge

The present study deals with the development of new composites, which use kaolin clay for strong chemical bonding of heavy metals from industrial laundry water cleaning sludge (LS) after the washing of heavily soiled industrial uniforms. Compositions of these materials with up to 20 wt% content of LS were sintered at temperatures of 1100 - 1150 - 1200 - 1250 and 1300 °C. The raw materials and ceramics were analyzed by XRD, XRF, SEM, EDS and LAMMA methods. The flexural resistance of the compositions ranged from 2.80 to 12.52 MPa, linear shrinkage values varied from 4.52 to 14.06%, water absorption values diverged from 13.03 to 20.33% and density floated from 1.65 to 1.83 g/cm3. Sintering at temperatures of 1150 °C and 1300 °C, with a partial melting of components, decomposed the Kaolin, Gibbsite, Dickite, Dolomite, and Almandine crystalline structures in the chemical environment of the compounds mixture and led to the synthesis of mainly amorphous vitreous substances with inclusions of crystalline structures such as Mullite, Cristobalite, and Alumina. The most important aspect of this research is the use of hazardous industrial waste as raw material for the consequent reduction the environmental burden caused by the indiscriminate disposal of these waste and thus abating the extraction of natural resources for the production of ceramic materials.