Gjergj Dodbiba

Combination of sink-float separation and flotation technique for purification of shredded PET-bottle from PE or PP flakes

Abstract In this contribution, the separation of polyethylene terephthalate (PET)–polyethylene (PE) and polyethylene terephthalate (PET)–polypropylene (PP) mixtures was studied in order to improve the grade of the raw input used in PET bottle recycling. First, PET bottles and their caps (made of PE or PP) were shredded and the floatability of each polymer was tested. Even with the addition of the wetting reagents dodecylamine acetate (DAA) or polyvinyl alcohol (PVA), the results did not suggest that the required 99.995% purity of PET plastic could not be achieved by floatation. Second, the mixtures were separated with a sink–float process using a drum separator. Finally, as the required purity of PET could not be obtained by either technique alone, a system utilising a combination of the two processes was developed. This system easily achieved the desired PET grade. At last, some sink–float experiments were performed with a medium of magnesium sulphate (dense medium separation).

Progress in Separating Plastic Materials for Recycling

In order to deal with the problems facing the plastics processing industry research, work is focused primarily on designing, developing and testing a variety of separation and sorting techniques able to recover plastics from wastes, which can be re-used or re-processed to form new products. In this regard, technologies developed in mineral processing can be of great help. Various techniques for separating plastics materials have been recently developed. These techniques can be divided in two main categories, i.e. wet separating techniques and dry separating techniques. This paper presents the recent progress in separating plastics reviewing the potential of the available techniques.

Leaching of indium from obsolete liquid crystal displays: Comparing grinding with electrical disintegration in context of LCA

In order to develop an effective recycling system for obsolete Liquid Crystal Displays (LCDs), which would enable both the leaching of indium (In) and the recovery of a pure glass fraction for recycling, an effective liberation or size-reduction method would be an important pre-treatment step. Therefore, in this study, two different types of liberation methods: (1) conventional grinding, and (2) electrical disintegration have been tested and evaluated in the context of Life Cycle Assessment (LCA). In other words, the above-mentioned methods were compared in order to find out the one that ensures the highest leaching capacity for indium, as well as the lowest environmental burden. One of the main findings of this study was that the electrical disintegration was the most effective liberation method, since it fully liberated the indium containing-layer, ensuring a leaching capacity of 968.5mg-In/kg-LCD. In turn, the estimate for the environmental burden was approximately five times smaller when compared with the conventional grinding.

ELECTROSTATIC SEPARATION OF THE SHREDDED PLASTIC MIXTURES USING A TRIBO-CYCLONE

In this experimental work, artificial plastic mixture of two kinds of components (i.e. PET and PE mixture) is tribo-electrostatically separated. The mixture is charged by friction in a tribo-cyclone.

Evaluation of a recycling process for printed circuit board by physical separation and heat treatment.

Printed circuit boards (PCBs) from discarded personal computer (PC) and hard disk drive were crushed by explosion in water or mechanical comminution in order to disintegrate the attached parts. More parts were stripped from PCB of PC, composed of epoxy resin; than from PCB of household appliance, composed of phenol resin. In an attempt to raise the copper grade of PCB by removing other components, a carbonization treatment was investigated. The crushed PCB without surface-mounted parts was carbonized under a nitrogen atmosphere at 873-1073 K. After screening, the char was classified by size into oversized pieces, undersized pieces and powder. The copper foil and glass fiber pieces were liberated and collected in undersized fraction. The copper foil was liberated easily from glass fiber by stamping treatment. As one of the mounted parts, the multi-layered ceramic capacitors (MLCCs), which contain nickel, were carbonized at 873 K. The magnetic separation is carried out at a lower magnetic field strength of 0.1T and then at 0.8 T. In the +0.5mm size fraction the nickel grade in magnetic product was increased from 0.16% to 6.7% and the nickel recovery is 74%. The other useful mounted parts are tantalum capacitors. The tantalum capacitors were collected from mounted parts. The tantalum-sintered bodies were separated from molded resins by heat treatment at 723-773 K in air atmosphere and screening of 0.5mm. Silica was removed and 70% of tantalum grade was obtained after more than 823K heating and separation. Next, the evaluation of Cu recycling in PCB is estimated. Energy consumption of new process increased and the treatment cost becomes 3 times higher comparing the conventional process, while the environmental burden of new process decreased comparing conventional process. The nickel recovery process in fine ground particles increased energy and energy cost comparing those of the conventional process. However, the environmental burden decreased than the conventional one. The process for recovering tantalum used more heat for the treatment and therefore the energy consumption increased by 50%, when comparing with conventional process. However, the market price for tantalum is very large; the profit for tantalum recovery is added. Also the environmental burden decreased by the recycling of tantalum recovery. Therefore, the tantalum recovery is very important step in the PCB recycling. If there is no tantalum, the consumed energy and treatment cost increase in the new process, though the environmental burden decreases.

Separation of Rare Earth Fluorescent Powders by Two-Liquid Flotation using Organic Solvents

In this paper, we describe a method for separation of ultra-fine particles prior to recycling. The authors suggest a two-step process for separating a mixture of three different rare earth fluorescent powders (i.e., red, green, and blue). Each step of the process is a two-liquid flotation, which involves two organic solvents (i.e., a non-polar and a polar solvent, in order to create two different phases) and a surfactant to manipulate the wettability of the powders. In the first step, the green powder migrates toward a non-polar phase such as n-heptane and remains at the interface of two solvents. The remaining two components precipitate in the polar phase. In the second step, the blue powder migrates toward a non-polar phase and remains at the interface of two solvents, while the red powder precipitates in the polar phase. After testing various non-polar solvents, a selection was made, and the operational parameters (e.g., concentration of surfactant and solid) were varied in order to maximize the efficiency of the process. The grade and recovery of each separated fluorescent powder were both greater than 90%.

Separation Performance of PVC and PP Plastic Mixture Using Air Table

The aim of the research presented in this article was to investigate separation performance of the air table when separating a binary mixture of plastics. Separation using the air table, i.e. a dry mechanical process that grades constituents of the mixture with differences in specific gravity, is employed for separation of the PVC/PP mixture. Moreover, the performance of the laboratory-scale air table is improved by increasing the height of riffles laid on the porous deck.

Characterization of Magnetorheological Suspension for Seal

Magnetorheological suspension (MRS) dispersing spherical several gm of iron particles in the low vapor pressure of dimethylpolysiloxane has been prepared. Yield stress has been proportional to square of magnetic field intensity and increases as containing larger volume fraction of iron particles and using solvent that is more viscous. The plastic viscosity increased linearly as a function of volume fraction of iron particles. The burst pressure of MRF seal is related on the dispersed iron particle size. The burst pressure is related on the magnetization curve in the MRS dispersing less than several gm of iron particles. On the other hand, the surface tension of solvent influences on the burst pressure in the MRS dispersing more than several gm of iron particles. Also the burst pressure is affected on the seal gap. In the large gap, the burst pressure in stationary condition adds the pressure by the yield stress of MRS. However, in the small gap the burst pressure of rotating condition is almost the same as that of stationary condition because the arranged iron particles cannot be reconstructed in a small gap. The larger viscosity of solvent and volume of iron in MRS increases the burst pressure.

MR FLUID OF LIQUID GALLIUM DISPERSING MAGNETIC PARTICLES

The heat convection, which can be provided from a magneto-rheological (MR) fluid, is a useful process in converting heat from high to low temperature and vice versa. In this work, the property and preparation of liquid gallium-based MR fluid is presented. The prepared MR fluid disperses micron-sized iron or nicked metal powders in liquid gallium (Ga). In this experiment, supercooling of MR fluid was investigated in order to obtain the condition under which the liquid state can be kept below the melting point. Moreover, the viscosity and elasticity of the prepared MR liquid were measured as a function of magnetic flux density. Finally, it was demonstrated that liquid Ga is a useful base for preparing a new type MR fluid.

FeNbVB ALLOY PARTICLES SUSPENDED IN LIQUID GALLIUM: INVESTIGATING THE MAGNETIC PROPERTIES OF THE MR SUSPENSION

A MR suspension was prepared by dispersing silica-coated iron alloy particles into a liquid gallium. In other words, the iron alloy particles of 30 to 50 nm in diameter were first prepared and then coated with silica. Next, the particles were then suspended in a liquid Ga (assay: 99.9999%). In addition, the magnetic properties of the synthesized particles and suspension under the influence of the magnetic field were investigated. One of the main findings of this study is that the prepared powder showed a temperature sensitive of magnetization within the testing temperature range of 293–353 K. The saturation magnetization of silica-coated FeNbVB particles was about 0.55 T, whereas the saturation magnetization (297 K) of the synthesized MR suspension was 0.019 T.