Investigation of the usage of waste materials and By-Products as grinding aids in calcite grinding

Along with the increasing importance of water worldwide, it is thought that developments in fine grinding processes performed by dry grinding and using grinding aids are too essential to be ignored. Indeed, grinding chemicals in the form of pure or commercial mixtures are intensively used in mineral processing plants in dry grinding systems to micronized sizes, e.g., dry grinding of calcite to micronized sizes. This study investigated the usage of olive pomace oil (OPO) and olive waste water (OWW), waste/by-products of the olive oil industry, as grinding aids in the dry grinding of calcite to micronized sizes using a laboratory-scale stirred ball mill and compared them with pure and commercial grinding aids. The test results were evaluated in terms of product fineness, powder flowability, color factor, surface adsorption characteristics, and agglomeration behavior. The study revealed that using any of the grinding aids tested improved the grinding process in comparison with the no aid condition. It was understood from the experiments and analyses that using OPO and OWW as grinding aids positively affected grinding performance. Particularly, the particle size analyses showed that the product fineness obtained in dry grinding tests was close to that obtained with commercial and pure grinding aids. Considering all the investigated grinding aids (except for OWW), powder flowability increased with the increasing concentration of the grinding aid. Remarkably, the OWW results demonstrated that the increase in dosage was not beneficial in terms of the ffp index. However, the enhancement of particle size was obvious. When evaluated in terms of product quality, four types of grinding aids increased total color differences with respect to feeding material and no aid test. Furthermore, the Fourier transform infrared spectroscopy (FTIR) conducted to determine the interaction between particle surfaces and grinding aids indicated that the grinding aids used in this study were adsorbed on the calcite surfaces by their non-polar, polar functional group and hydroxyl group. The analysis, in which the agglomeration phenomenon was examined with SEM (scanning electron microscopy) images, revealed that using grinding aids reduced the formation of agglomerates in comparison with the no grinding aid condition.