New LCD Panel Recycling System Reduces Hazards And Protects The Environment

- Oct 10, 2018-

            

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With the increasing reliance of home users on electronic devices and the increasing popularity of liquid crystal display (LCD) vehicles, once these devices are no longer in use, reducing their environmental impact is becoming increasingly important.


Previous studies have demonstrated the dangers of LCD panels containing liquid crystals, indium and other heavy metals, but there is currently no solution for recycling these panels.


In this context, researchers at the Taiwan Industrial Technology Research Institute (ITRI) plan to develop a new LCD waste recycling system to change this situation. The system is cost effective, does not generate any waste, and allows manufacturers to save and reuse some valuable heavy metals for LCD panel production. The system enables the recovery of liquid crystal, indium and glass by integrating sequential separation, ppb purification, and nanopore technology.


Liquid crystal is a synthetic chemical with high unit cost and high stability and is not easily biodegradable. The liquid crystal structure contains a large amount of benzene ring, fluorine, chlorine and bromine. If it is buried, it will penetrate into the groundwater system and affect the ecosystem.


ITRI researcher Chien-Wei Lu said: "Liquid crystal panels, although only a few millimeters thick, contain more than a dozen materials, making their handling and recycling particularly difficult. We have in-depth analysis of the characteristics and reusability of each material in the LCD panel. And according to the correlation between each material, the logic separation program is designed: firstly separate the liquid crystal, indium and glass materials, and then develop different purification technologies for each material, and then realize the reuse of these materials." The method is smashed from the panel The system begins with the ability to smash the LCD panel to expose the liquid crystal material in the panel. The separated LCD panel then enters a continuous liquid crystal extraction system and the liquid crystal therein can be extracted by a specific reagent in a plurality of cycles. The liquid crystal is exposed on the surface of the glass substrate, enabling the system to reduce processing time by integrating extraction and purification functions. The impurities therein can be removed by salt adsorption. After removal of the liquid crystal, the panel fragments enter the indium extraction system and are repeatedly used by the scrubbing agent to enable removal of indium from the panel fragments. The precipitate containing indium is dissolved with a reagent and enters an indium concentration system, which is then concentrated by a precipitation principle.


After removing most of the material, the collection process of SiO2, Al2O3, B2O3, and other alkaline earth metal oxide glass was started. The liquid crystal extracted by this new method can be reused to realize the recycling of indium and the liquid crystal glass material. Liquid crystal extraction from a waste liquid crystal panel can achieve near 100% liquid crystal recovery and 90% indium recovery. This process can reduce the cost of new liquid crystal generation and reduce the impact on the environment.


LCD panel hazard


Earlier studies have shown the dangers of liquid crystals, indium and other heavy metals present in LCD panels. If organisms ingest fat-soluble liquid crystals, they are likely to be stored in the organism without metabolism, leading to various organ diseases. If incinerated at a sufficiently high temperature, the liquid crystal may turn into a CFC and destroy the atmospheric ozone layer; if it is incinerated at a low temperature, the liquid crystal may become dioxins, PCB, hydrochloric acid or hydrofluoric acid, and these are the culprits of environmental pollution. The culprit.


Conventional physical treatment of liquid crystal panels requires the board to be broken and then added to cement or concrete, but this method cannot remove materials such as liquid crystal, indium, tin and molybdenum in the liquid crystal panel. Therefore, after rainwater erosion, liquid crystal materials and heavy metal materials may cause serious pollution to the environment.


LCD panels are marked as hazardous waste in many countries and regions. This situation requires on-site processing or burying, burning, or physical processing of LCD panel waste, but this increases the cost of processing and environmental damage.


To test this new technology, ITRI has set up a pilot plant that can process about 3 tons of LCD panel waste per day, produce 3 kg of liquid crystal, 750 g of indium and about 2550 kg of glass, which can be reused as a green building or as a heavy metal adsorbent.


It is estimated that hundreds of thousands of tons of LCD panel waste are produced every year in North America. Therefore, the effective treatment of LCD panel waste is an urgent task!