Ionic liquid assisted extraction of gallium and recovery of valuable metals from spent LED lights

• Recovery of Ga, Au, Cu from spent LEDs using Cyphos IL 104 as extractant. • Ga is extracted as R 3 R'P + GaCl 4 − , confirmed by 31 P NMR. • Recovery of Ga and Cu as oxide nanoparticles and Au as gold nanoparticles. • Extractant is recyclable with negligible loss in extraction efficiency. • Final products are obtained with more than 99.9 % purity. The increasing use of LEDs has led to a significant accumulation of electronic waste, highlighting the need for efficient and sustainable methods to recover valuable metals such as gallium, copper, and gold. Present study addresses gallium extraction from chloride media using Cyphos IL 104 (diluted in toluene), as a promising extractant to recover valuable metals from spent LED lights. Preliminary studies were conducted with Cyphos IL 104 to optimize different parameters like time of equilibration, concentration of acid, chloride ion and extractant on gallium extraction. Slope and 31 P NMR analysis were also performed to identify the extraction mechanism of gallium into organic phase. Optimized extraction parameters have been used to recover gallium, copper and gold from leach liquor of spent LED lights containing 136 mg L −1 gallium, 33 mg L −1 gold, 381 mg L −1 copper, 84 mg L −1 aluminum. McCabe‒Thiele plots were employed for determination of the required number of extraction-stripping stages, which were further verified using counter‒current studies with leach liquor. Copper, gallium and gold were separated by selective stripping using oxalic acid (0.5 mol L −1) , H 2 SO 4 (0.5 mol L −1 ) and thiourea (0.02 mol L −1 ) solutions, respectively with > 99% purity. The solutions from stripping of gallium and copper were used to obtain their oxides by precipitation followed by thermal decomposition. Gold was recovered from the strip solution as gold nanoparticles (NPs) by reduction. Synthesized oxides were characterized by advanced techniques such as Field-emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The present work may be employed for the recovery of valuable metals from industrial waste using an environmentally friendly extractant.