Separation and recovery of materials from the waste light emitting diode (LED) modules by solvent method

摘要

Nowadays, a large quantity of Light Emitting Diodes (LEDs) have been produced and updated with the development ofoptoelectronic industry. At the same time, many waste LEDs are discarded. However, there are many metals and non-metalsin waste LEDs, which may cause secondary pollution and waste of resources if disposed improperly. In this study, solventmethod was used to dissociate the waste LED modules and recycle resources. Firstly, the components of the waste LEDmodules were analyzed. The main component of the transparent plastic part, usually used as packaging materials, is curedepoxy resin, and the main component of the white plastic part as the skeleton of LED modules is a mixture of polyphenyleneoxide (PPO) and polystyrene (PS). Then, eight organic solvents, [EMIM~+]BF_4~− ion liquid and sodium hydroxide (NaOH)inorganic reagent were tried to separate a 40 × 40 mm~2 waste LED module respectively. The results showed that only threeorganic solvents—dimethylformamide (DMF), dimethylacetamide (DMA), dimethyl-sulfoxide (DMSO) could dissociatethe waste LED module very well. The used DMF solution was purified by rotary evaporation, and the regenerative DMFsolution could be reused because its property has not changed. The solid residue obtained after rotary evaporating DMFwas identified as polystyrene (PS). It was inferred that the waste LED module was dissociated through the DMF dissolvingthe PS of white plastic. In addition, the effect of DMF, DMA and DMSO dissociating the waste LED modules with thechange of temperature was discussed. It was found that the choice of suitable solvent is a key for this method, and the heatingtemperature was also a very important factor. Finally, it was measured that the cured epoxy resin and the white plasticof the waste LED module accounted for about 31.4% (w/w) and 37.7% (w/w) respectively, which can be recycled. In short,the method not only separated completely the waste LED module and its each part was recycled easily, but the solvents canbe reused. This study suggests a new route to recycle LEDs due to its environmentally friendly process, which may exert asignificantly beneficial impact on our environment.