Ali Güney

Selective separation of virgin and post-consumer polymers (PET and PVC) by flotation method

More and more polymer wastes are generated by industry and householders today. Recycling is an important process to reduce the amount of waste resulting from human activities. Currently, recycling technologies use relatively homogeneous polymers because hand-sorting waste is costly. Many promising technologies are being investigated for separating mixed thermoplastics, but they are still uneconomical and unreliable. At present, most waste polymers cause serious environmental problems. Burning polymers for recycling is not practiced since poisonous gases are released during the burning process. Particularly, polyvinyl chloride (PVC) materials among waste polymers generate hazardous HCl gas, dioxins containing Cl, etc., which lead to air pollution and shorten the life of the incinerator. In addition, they make other polymers difficult to recycle. Both polyethylene terephthalate (PET) and PVC have densities of 1.30-1.35g /cm(3) and cannot be separated using conventional gravity separation techniques. For this reason, polymer recycling needs new techniques. Among these techniques, froth flotation, which is also used in mineral processing, can be useful because of its low cost and simplicity. The main objective of this research is to recycle PET and PVC selectively from post-consumer polymer wastes and virgin polymers by using froth flotation. According to the results, all PVC particles were floated with 98.8% efficiency in virgin polymer separation while PET particles were obtained with 99.7% purity and 57.0% efficiency in post-consumer polymer separation.

New aspect of chromite gravity tailings re-processing

Abstract Karagedik Chromite Concentrator of the ETI Holding Co., which is located in Fethiye (south Turkey), has been producing chromite concentrate assaying 47–48 % Cr2O3 from chromite ores containing 30–35 % Cr2O3 by gravity separation methods since 1920. The tailings, containing 13–14 % Cr2O3, which had been removed from this plant, were accumulated at stockpiles, amounting to about 1.2 million tons. Generally, at the chromite concentrators of Turkey, such as Karagedik Concentrator, ultra fine size chromite particles (minus 0.038 mm.) were removed as tailings. Likewise, the tailings of the Karagedik concentrator contain a minus 0.038 mm fraction amounting to 42 % of the total. The Cr2O3 content of this size faction is about 23 % with Cr2O3 distribution of 76 %. In order to recover the ultra fine chromite particles from the Karagedik Concentrator tailings, a new process, including Wet High Intensity Magnetic Separation and column flotation, was developed and the Karagedik Research Pilot Plant based on this process was commissioned in 1999. At this plant, final concentrates, assaying 46–48% Cr2O3 are produced and overall plant recoveries are about 60–65%.

Beneficiation of fine coal by using the free jet flotation system

Abstract The free jet flotation system was developed at the Berlin Technical University in 1985. This system was able to treat ultrafine particles of about −53 μm. In the present study, the fine size fraction of the coal (−0.5 mm) containing 45% ash taken from the Zonguldak Central Washery Plant (ZCWP) of Turkish Hard Coal was beneficiated by using the free jet flotation system. In the flotation tests, the best results were obtained in the case of using a mixture of 90% kerosene and 10% iso-octanol in the amount of 400 g/ton as a collector. Also, the optimum system parameters of a 30 l free jet type flotation (FJFT) cell used in this study were determined from the results of systematic tests. In the optimum free jet flotation conditions, the floating coal containing 18.73% ash with a combustible recovery of 72.4% was obtained.

A new flowsheet for processing chromite fines by column flotation and the collector adsorption mechanism

Tailings produced from Uckopru Chromite Concentrator are composed of fines mostly below 1 mm of which 52.3 wt. % is below 0.1 mm. A new flow sheet involving shaking table for processing −1 + 0.1 mm size fraction, and High Intensity Wet Magnetic Separator (HIWMS) and column flotation for treating -0.1 mm size fraction was put forward. According to the new ffowsheet, the Uckopru Concentrator tailings assaying 13.99 wt. % Cr2O3 was upgraded to 47.4 percent Cr23 at a recovery of 66.4 wt. % using shaking table followed by a combination of magnetic separation and column flotation with a mixture of anionic collectors at pH 11. The success of such high pH with anionic surfactants is indeed intriguing. Electrokinetic methods were used to elucidate the mechanism of collector adsorption and correlate the findings with the optimum flotation conditions. Multivalent constituent ions such as Cr3+, Al3+, Fee+ and Mg2+ were found to adsorb on chromite surface and shift the iep of chromite in the direction of oxide form of the mineral. The anionic collectors also imparted a negative charge to chromite in the entire pH region. The positive sites on the chromite surface, onto which anionic collectors adsorb, are generated through the formation of significant amounts of hydroxy complexes of magnesium ion at pH 11. Complementary infrared data reveals the absence of a shift in the spectra indicating the possibility of physical adsorption in the system.

Beneficiation of low-grade feldspars using free jet flotation

The largest feldspar reserves of Turkey are located in the western part of the country. This region has albite reserves of as much as 400 million tons. The main impurities in these deposits are TiO 2 and Fe 2 O 3 bearing minerals with grain sizes of 30-500 microns. Beneficiation of low-grade feldspar ores by jet flotation was investigated by using jet flotation parameters including immersion depth of the nozzle, thicknesses of turbulence, and laminar zones. As a result of these tests, air volume flow was also calculated for a pilot scale free jet flotation unit. The results showed that an effective separation of TiO 2 and Fe 2 O 3 bearing minerals by jet flotation could be accomplished through careful optimization of the parameters.

Investigation of thermal treatment on selective separation of post consumer plastics prior to froth flotation

Plastics have become the widely used materials because of their advantages, such as cheapness, endurance, lightness, and hygiene. However, they cause waste and soil pollution and they do not easily decompose. Many promising technologies are being investigated for separating mixed thermoplastics, but they are still uneconomical and unreliable. Depending on their surface characteristics, these plastics can be separated from each other by flotation method which is useful mineral processing technique with its low cost and simplicity. The main objective of this study is to investigate the flotation characteristics of PET and PVC and determine the effect of plasticizer reagents on efficient plastic separation. For that purpose, various parameters such as pH, plasticizer concentration, plasticizer type, conditioning temperature and thermal conditioning were investigated. As a result, PET particles were floated with 95.1% purity and 65.3% efficiency while PVC particles were obtained with 98.1% purity and 65.3% efficiency.

Separation of PET and PVC by Flotation Technique Without Using Alkaline Treatment

PET and PVC cannot be separated by gravity separation techniques due to their close density. For this reason, plastic recycling needs other separation techniques. Froth flotation, which is used in mineral processing, could be useful because of its low cost and simplicity. The main objective of this research is to investigate the flotation characteristic of PET and PVC and determine the effects of plasticizers on plastic separation without any alkali pre-treatment. In selective flotation experiments, water bottles and waste water pipes were used for this purpose, and Triton XL-100 N and diethylene glycol dibenzoate were used as plasticizers. Various parameters such as pH, plasticizer concentration, conditioning time, and flotation time were investigated. According to the results, PET particles were floated with 100% purity, and the product remaining in flotation cell (PVC particles) was obtained with 86.1% purity.

Selective flotation of PVC using gelatin and lignin alkali

Recycling has become one of the most important issues as a result of increasing waste mass in present day. This is especially important for polymer wastes as they are hard to degenerate in nature. Today, most of the practical methods used for the recycling of waste mass, such as hand sorting, gravity separation, etc., cannot be performed successfully owing to close densities of polymers. Froth flotation can be used successfully and economically for this purpose. The main objective of this study was to investigate the effect of plasticizer reagents and the success of froth flotation at plastic recycling. In this study, lignin alkali and gelatin were used as plasticizer reagents. The effect of these reagents was searched with the parameters of pH, concentration, conditioning and flotation time. In the case of post-consumed polyethylene terephthalate and polyvinyl chloride (PVC), 98.9% purity of PVC was obtained at optimum conditions.

EFFECTS OF MODIFYING REAGENTS ON HUNTITE FLOTATION

Huntite is one of the most important flames retardant additive materials. Although various areas of the world have potential huntite deposits, huntites place in industry is not well known and a detailed field search for hunites deposits has not been conducted yet. Formations in the world include different types of minerals such as huntite, hydromagnesite, magnesite, clay minerals, and dolomite. However, physical, chemical, physicochemical, and mineralogical properties of these ores have not been determined yet. In this study, the flotation behavior and electrokinetic properties of huntite were determined in the presence of potassium oleate. The effects of common ions that are expected in flotation pulps, such as Mg2+and Ca2+, were studied. The influences of pH and modifying reagents such as sodium silicate (Na2SiO3·5H2O) and carboxymethyl cellulose (CMC) on surface properties of huntite were also examined. Electrokinetic measurements showed that the iso-electric point of huntite was approximately 8.0. The surface charge of huntite becomes positive in the presence of 10−2 M of MgCl2 and CaCl2 at all pH values. According to microflotation test results, Mg2+ and Ca2+ ions have a detrimental effect on the floatability of huntite. Na2SiO3 was seen to have no significant effect on the floatability of huntite. Flotation experiments with CMC indicated that it acts as a depressant on huntite.

New Developments in the Processing of Chromite Tailings

Shaking table, multi-gravity separator, high intensity wet magnetic separator, free jet and column flotation were applied for concentration of Uckopru fine chromite tailings amounting about 1 million tons and occupying an area of approximately 50000 m2. A flow-sheet was developed for the concentration of chromite tailings economically and a concentrate of about 48% Cr2O3 content could be obtained with a recovery of about 67.3%. Resultant tailings with 5.6% Cr2O3 can be transported to an environmentally suitable area.