Marble processing effluent treatment sludge in waste PET pyrolysis as catalyst-I: pyrolysis product yields and the char characteristics

The processing and evaluation of industrial wastes together with other wastes may help material to remain in the system longer within circular economy. This study aimed to evaluate marble processing effluent physicochemical treatment sludge (K1) as catalyst in the waste poly(ethylene terephthalate)-PET pyrolysis. The effects of K1 dose (10-50%) and target temperature (300, 500, 700 degrees C) on the pyrolysis product yields and char characteristics were investigated. Fixed bed batch pyrolysis system was used under nitrogen atmosphere. The pyrolysis gas, oligomer and char product quantities changed in the range of 10.2-43.9, 2.42-21.9 and 23.5-83.8%, respectively. The increase in the K1 dose increased the char and decreased the liquid amount. Thermal, chemical, mineralogical characterization and proximate analyses were applied to char products. PET + K1 mixtures' chars mainly contain calcium carbonate (CaCO3), dolomite (CaMg(CO3)(2)), Ca(OH)(2), CaO, calcite (Mg0.03Ca0.97)(CO3). The char humidity and heat values decreased with increasing K1 doses. The residual value at 900 degrees C for PET waste was 14.2% while for PET + K1 mixtures it varied between 15.2 and 33.9%. Thermal degradation residual percentages of the 500 degrees C pyrolysis chars varied between 79.2 and 58.8%. K1 increased the thermal stability of the char, and this can provide it new areas of use. For example, when thermally stable char is needed with low pore volume and low surface area, K1 dose between 30 and 50% and the pyrolysis temperature of 500 degrees C can be suggested. By using K1, the variety of chars having different characteristics was obtained which transformed K1 and chars economic value as second-generation solutions.