Degradation of nitrate and secondary pollution in drinking water by S-NZVI prepared from steel pickling waste liquor

Abstract

In this study, degradation of nitrate in drinking water by nanoscale zero-valent iron prepared from steel pickling waste liquor(S-NZVI) was investigated. Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM) and Specific Surface Area Analyzer (BET) were used to characterize the properties of the synthesized nanoparticles. Effects of different parameters, such as S-NZVI dosage, initial nitrate concentration, and pH, on the denigration were conducted. The results showed that S-NZVI had the similar characteristic of the NZVI prepared by chemical agents. The experiments indicated that the slightly acid medium with the S-NZVI dosage of 2.8 g/L had a better removal effect of nitrate, and the high removal efficiency of 96% was observed after the reaction time of 2 h, which demonstrated it was feasible and effective to remove nitrate by S-NZVI. The kinetic studies indicated that the degradation rate of nitrate by S-NZVI followed the pseudo-first order kinetics. By analyzing the end-products of nitrate reduction, 94% of nitrate was converted into ammonia ions by S-NZVI and the others translated into a little amount of nitrite and nitrogen. It is a relatively easy and cost-effective method for nitrate removal, so S-NZVI has a great potential application in nitrate removal of drinking water. The ammoniac nitrogen pollution, the main product and second pollution from the denitrification by S-NZVI can be completely degraded by cation exchange resin. So the nitrogen pollution has been completely removed from drinking water polluted by nitrate.