RESUMEN
The adsorption performances of ammonia nitrogen (NH+4-N) in water by unmodified biochar are ineffective. In this study, nano zero-valent iron-modified biochar (nZVI@BC) was prepared to remove NH+4-N from water. The NH+4-N adsorption characteristics of nZVI@BC were investigated through adsorption batch experiments. The composition and structure characteristics of nZVI@BC were analyzed using scanning electron microscopy, energy spectrum analysis, BET-N2 surface area (SSA), X-ray diffraction, and FTIR spectra to explore the main adsorption mechanism of NH+4-N by nZVI@BC. The results showed that the composite synthesized at the iron to biochar mass ratio of 1:30 (nZVI@BC1/30) performed well in NH+4-N adsorption at 298 K. The maximum adsorption amount of nZVI@BC1/30 at 298 K was remarkably increased by 45.96% and reached 16.60 mg·g-1. The pseudo-second-order model and Langmuir model fitted well with the adsorption process of NH+4-N by nZVI@BC1/30. There was competitive adsorption between coexisting cations and NH+4-N, and the sequence of coexisting cations to the adsorption of NH+4-N by nZVI@BC1/30 was Ca2+> Mg2+> K+> Na+. The adsorption mechanism of NH+4-N by nZVI@BC1/30 could be mainly attributed to ion exchange and hydrogen bonding. In conclusion, nano zero-valent iron-modified biochar can improve the adsorption performance of NH+4-N and enhance the application potential of biochar in the field of nitrogen removal from water.
RESUMEN
The distributions and effects of 31 selected endocrine disrupting chemicals (EDCs) in two drinking water factories were analyzed in this study. The distributions of EDCs were analyzed by solid phase extraction (SPE) combined with liquid chromatography tandem mass spectrometry (LC-MS/MS). The concentrations of these EDCs were from lower than the LOD (limit of detection) to 23.13 ng L (- 1) in the samples; most of them were lower than 1 ng L (- 1). The highest concentration (23.13 ± 1.45 ng L (- 1)) was detected in the raw water. Twenty-six chemicals were found in the raw water and only five in the finished water of drinking water factory A, while 25 chemicals were detected in the raw water and two in the finished water of drinking water factory B. The results indicate that most of the EDCs can be removed by the water treatment process. In the advanced treatment process, the ozonation processes have the highest removal efficiency. Separate analyses in May and September show similar results. Apart from the chemical analysis, yeast strain transformed when the estrogen receptor α (ERα) gene was employed to test the estrogenic effects of the water samples. Due to the low concentrations of these EDCs, no significant estrogenic effects were found from the samples.