Lithium slag is an industrial waste residue of the extraction of lithium carbonate industry, which has the issue of high output and low utilization rate. In order to improve the utilization rate and value of lithium slag, it was directly used as a raw material to synthesize NaX zeolite using a hydrothermal and microwave-assisted method in this paper. The process of synthesizing NaX zeolite from lithium slag was analyzed and characterized by X-ray diffractometry, Fourier transform infrared spectroscopy and solid state nuclear magnetic resonance. The reaction mechanism of NaX zeolite from lithium slag was also proposed. The structure of NaX zeolite synthesized from lithium slag was characterized. The results indicate that during the synthesis, aluminum species in the lithium slag transform from Al^VI to Al^IV, and the silicon species undergo a transition from Q⁴ (0Al) and Q⁴ (1Al) structures to Q⁴ (1Al) and Q⁴ (2Al) structures. The synthesis time of NaX zeolite with the microwave-assisted method is only about 1/3 that of hydrothermal synthesis. Microwave irradiation accelerates the dissolution of lithium slag, the generation of aluminosilicate gels, and the crystallization of the NaX zeolite, but does not change the process of synthesis of NaX from lithium slag. The NaX zeolite synthesized from lithium slag has smaller grains (0.5–0.8 μm) and good stability, and the adsorption capacity of water reaches 32 wt% when the relative humidity is 90%. This study provides technical support for the large-scale production of NaX zeolite from lithium slag.

Bragg gratings were fabricated in all-solid Bragg photonic crystal fibers with 100 fs, 800 nm infrared radiations and a phase mask. Both multimode and single-mode grating resonances were achieved by accurately adjusting the focal position of the irradiation beam in the Bragg fiber. Thermal annealing investigations indicated that the gratings were induced by Type I-IR and Type II-IR refractive index change. Typical Bragg wavelength shifted with the change of temperature and strain, which were measured respectively.

The adsorption desulfurization process of diesel fuel is suffering from adsorbent regeneration limitation. Adsorption performance of activated carbon (AC) for S-compounds and hydrocarbons in low-sulfur real diesel was investigated by an adsorption fixed bed. The exhausted AC was regenerated by different solvents, including n-octane, ethanol and cyclohexane. AC samples were characterized using N₂ adsorption–desorption isotherm at 77 K, TG and FT-IR. S-species and hydrocarbons-species in real diesel and the regeneration solutions were analyzed by gas chromatography-sulfur chemiluminescence detection (GC-SCD), gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC). The effects of hydrocarbons on desorption performance of S-compounds and extraction capability of n-octane were investigated. The effect of n-octane as a recycled regeneration solvent on the regeneration stability of AC in this work was also considered. The S-content in diesel was reduced to less than 10 ppm from an initial S-content of 34.83 ppm. The competitive adsorption between polycyclic aromatic hydrocarbons (PAHs) and S-compounds was the largest in hydrocarbons. The regeneration performance of different solvents for AC decreased as follows: n-octane > ethanol > cyclohexane. The regeneration efficiency of AC was 100% after a first adsorption–desorption cycle, and was held near 73% after 50 cycles using fresh n-octane as a regenerating solvent. The regeneration efficiency of AC can be maintained at 45% after 20 cycles using n-octane as a recycled regeneration solvent. According to the results of characterizations and tests, we found that multilayer adsorption of S-compounds and PAHs occurred in the mesopores of AC, while the aggregation phenomenon of small alkane molecules mainly existed in the micropores.