In this study, the critical coalescence concentrations (CCC) of selected commercial frother solutions, namely polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and as a reference, methyl isobutyl carbinol (MIBC), were determined using a bubble column based on light absorption. The results for all seven frothers showed that BTEG has the worst bubble inhibiting performance, and PPG 600 has the best bubble inhibiting performance. While critical coalescence concentration (CCC) was found as 3 ppm for PPG 600, it increased to 25 ppm for BTEG. In the case of MIBC, which was the reference point, the CCC value was found as 10 ppm, which was consistent with the literature. The surface tension isotherms of the frothers were determined and analyzed with one of the latest adsorption models. The results indicated that the polypropylene glycol frothers showed more surface activity compared to alcohol or other frothers investigated. This is due to the additional reorganization of the PPG molecules on the air/water interface, thus boosting its surface activity.

In recent years, most of the studies have been adapted to determine the optimum conditions for the flotation of very fine minerals. In this context, besides parameters such as particle size, morphology, and pH, the effects of frother type and its concentration present a very significant role in optimizing the flotation conditions. Therefore, the effects of froth stability during flotation can be considered one of the most important issues. Considering that knowledge in mind, in this study, the foamability and froth decay rate of six frothers (PPG200, PPG400, PPG600, BTEG, BTPG, and BDPG) having different molecular weights but similar polyglycol structures were investigated. In addition, methyl isobutyl carbinol (MIBC) which is a well-known frother type in the industry was also used as a reference. Additionally, a series of tests were also performed in the presence of collectors (Dodecylamine hydrochloride, DAH, and sodium oleate, NaOL) + frother mixtures to mimic the flotation conditions. The results of these tests indicated that the bubble size became finer at even low concentrations of PPG600 and PPG400 frothers. Following that, a significant decrease in bubble size was also found for the collector + frother mixtures system regardless of the concentration of the frothers.

In this study, the free and hindered settling conditions for coal-shale-clay separation through a Falcon concentrator were determined experimentally using response surface methodology. The model parameters consisted of the separation efficiency and ash content of the concentrate and tailings. Based on the model with the highest response, free settling conditions dominated at centrifugal forces below 100 g and at solid concentrations of up to 30%–35%, especially for coarser particle sizes of 300 µm. These results revealed that, for effective fine coal beneficiation through a Falcon concentrator, the solid concentration should be maintained higher than 30%–35% (with a maximum of 45%–50%) to create hindered settling conditions because separation under these conditions is achieved based on specific gravity. The best results were obtained at a solid concentration of 50%. This finding was interesting because separations through enhanced gravity separators were achieved under conditions similar to separations performed in autogenous media.

In this study, the production of ultrapure Na-bentonite by centrifuge based techniques for organo and nano composite bentonite industry was investigated. Various parameters including centrifuging time, solids content, and g force were studied to determine the set points (cut size) for theoretical CEC (cation exchange capacity) and recovery limits. The experimental results were modeled using Response Surface Method (RSM) with high responses (regression > 85% and correlation coefficients > 0.85). it is shown that the commercial centrifugation equipment operating with residence time of 10–15 seconds and g values lower than 300 g such as Multi Gravity separator (MGS), Hydrocyclones and Falcon/Knelson concentrators are not suitable for obtaining pure quality Na-bentonite, since the set point size (5-8 µm) is higher than 2 µm which is defined for bentonite of high smectite contents. The RSM models demonstrate that only the kind of separators such as decanter centrifuges with operational g forces higher than 600 may exhibit the closest set point to 2 µm and thus enable the achievement of an ultra pure quality bentonite product. These assumptions obtained from the developed model were confirmed by running tests on Falcon and Mozley hydrocyclone separators.

In this study, fine coal from the Tunçbilek Region (Turkey) was subjected to autogenous medium washing tests. The autogenous medium was formed in the presence of clayey minerals with the increased solids concentration of the feed slurry. The clayey minerals also acted as tracer to investigate the conditions of free settling conditions where the particle size based separation was observed. The effect of feed slurry, solids concentration, and the presence of clayey minerals on the separation of coal fines were investigated for the sizes of −300, − 150, and −75 µm. The results reveal that the solids concentrations lower than 10% resulted in the particle size based separation (free settling conditions) and the solids concentrations higher than 10% required the density based separations (hindered settling conditions). Satisfactory separations were achieved at solids concentrations of 10–40%. In the case of higher solids concentrations, an additional increase on separation was ascribed to the development of autogenous medium separation. In addition, the increase in the solids concentration, the presence of clayey minerals on feed also created the autogenous medium separation conditions.