Facilitated by TiO2 particles absorbing La3+ in hydrosol, La-doped TiO2 was prepared by a sol-hydrothermal method. Electron paramagnetic resonance and Brunauer−Emmett−Teller (BET) surface area analysis showed that the obtained La-doped anatase TiO2 surface provided a higher density of oxygen vacancies without a change in the BET surface area. A theoretical calculation was carried out to explain the generation mechanism of the increased oxygen vacancies. The results showed that the La-doped anatase TiO2 (101) surface tends to engender oxygen vacancies. The photoelectric conversion efficiency of dye-sensitized solar cells fabricated from 1 mol % La-doped TiO2 reached 6.72%, which gave an efficiency improved by 13.5% compared with that of the cells fabricated from pure TiO2. The improvement in the efficiency was ascribed to more dye absorbed on the surface of TiO2.

Cobalt (Co) and lithium (Li), rare and valuable elements, are mainly used to prepare lithium cobalt oxide (LiCoO2) for applications in lithium-ion batteries (LIBs). Developing an effective method to recover Co and Li from the waste LIBs is of great significance. In the present study, Co and Li were extracted from pure LiCoO2 powders and the extracted cathode materials powders from the waste LIBs after acid dissolution via a mechanochemical reduction process with iron powders. For pure LiCoO2 powders, the effects of Fe to LiCoO2 mass ratio, rotation speed, and mechanochemical reduction time were examined. These parameters influenced positively the extraction of Co, while they showed negligible effects on the leaching of Li. The X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated a promoted extraction of Li arising from the reduction of particle sizes, magnification of specific surface area, and change of the crystal structure of particles. For high-efficiency leaching of Co by the mechanochemical reduction process with iron powders, X-ray photoelectron spectroscopy (XPS) analysis indicated the changes in the valence state of Co. The actual cathode materials disassembled from the wasted LIBs pretreated by this novel mechanochemical reduction process were also explored. The results indicated that the leaching ratios of Li, Co, Mn, and Ni could reach 77.15%, 91.25%, 100%, and 99.9%, respectively. This novel mechanochemical process would be of great importance for the recovery of valuable metals from waste LIBs.

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Desoldering separation of solder from waste printed circuit boards (PCBs) is a key step to recycle or dispose the electronic waste effectively. In the present work, a novel way for selective desoldering separation was achieved by dissolving lead−tin solder in fluoroboric acid containing H 2 O 2 . This leachant was observed possible to take the solder into solution with negligible dissolution of copper or other metals within 35 min. After leaching, the electronic components (ECs) could be easily removed from the boards under good experiment conditions. The effects of oxidants, dosage of H 2 O 2 , and acid concentration were explored to obtain the suitable experimental conditions. The results showed that 2.5 mol/L fluoroboric acid containing 0.4 mol/L added oxidant H 2 O 2 within the reaction of 35 min could be regarded as the optimum conditions for the selective desoldering separation from the waste PCBs. Both theoretical analysis using HSC Chemistry software and actual waste PCBs examination verified that the solder could be dissolved selectively by this novel process via excess solder added to inhibit the effect of copper dissolution if exists. This safe, fast, economic, and environmentally friendly dismantling PCBs process would be of great importance in recycling waste electrical and electronic equipment (EEE) effectively.