4-Nitrobenzoic acid is stable, toxic, and non-biodegradable. Conventional methods for wastewater treatment are ineffective for the treatment of 4-nitrobenzoic acid. In this study, the degradation efficiency of 4-nitrobenzoic acid by ultrasound in the presence of zero-valence zinc (Zn) was reported. The operating parameters were optimized, and the potential mechanisms were investigated. The results showed that there was a significant synergetic effect between ultrasound and Zn, and the synergetic factor was 2.26. The optimized treatment conditions were as follows: Initial pH 7.0 and Zn dosage of 0.4 g/L, under which the 4-nitrobenzoic acid degradation efficiency reached more than 85% after 30 min. The potential mechanisms included hydroxylation and the mechanical effect of ultrasound and the reduction and particle effects of Zn, which enhanced each other. The determination of intermediate products indicated that the catalytic degradation of 4-nitrobenzoic acid started with the destruction of the nitro group.

The coal mine underground reservoir is an appropriate solution between coal mining and groundwater resource protection and utilization. By calculating the storage capacity of a groundwater reservoir, the storage coefficient has been proved to be always an empirical value. Based on the mathematical derivation of the vertical fracture area ratio and the horizontal fracture area rate of the collapse zone and the fissure zone in the goaf area of the coal seam, the mathematical models of tem are derived, and the model for calculating the water storage coefficient is derived. The water storage coefficient derived from the theoretical model had more basis and more advanced than the traditional empirical value. By using this method, the practical calculation of No.1 underground reservoir of the DaLliuta Coalmine in Shenhua Shendong, has got a perfect matching with the actual groundwater storage capacity.