期刊
CHEMOSPHERE
卷 290, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2021.133331
关键词
Nitrate removal; Groundwater anions; Catalytic denitrification; Competitive inhibition; N-2 selectivity
资金
- Research Grants of Nazarbayev University [091019CRP2106, 021220FD1051]
- Ministry of Education and Science of the Republic of Kazakhstan [APO9260229]
The presence of oxyanions in groundwater significantly affects the reactivity and selectivity of Cu-Pd-hematite bimetallic catalysts for NO3- reduction, making their successive application challenging.
The presence of various oxyanions in the groundwater could be the main challenge for the successive application of Cu-Pd-hematite bimetallic catalyst to aqueous NO3- reduction due to the inhibition of its catalytic reactivity and alteration of product selectivity. The batch experiments showed that the reduction kinetics of NO3- was strongly suppressed by ClO4-, PO43-, BrO3- and SO32- at low concentrations (>5 mg/L) and HCO3- , CO32-, SO42- and Cl- at high concentrations (20-500 mg/L). The presence of anions significantly changing the end product selectivities influenced high N-2 selectivity. The selectivity toward N-2 increased from 55% to 60%, 60%, and 70% as the concentrations of PO43-, SO32-, and SO(4)(2-)increased, respectively. It decreased from 55% to 35% in the presence of HCO3- and CO32- in their concentration range of 0-500 mg/L. The production of NO2- was generally not detected, while the formation of NH4+ was observed as the second by-product. It was found that the presence of oxyanions in the NO3- reduction influenced the reactivity and selectivity of bimetallic catalysts by i) competing for active sites (PO43-, SO32-, and BrO3- cases) due to their similar structure, ii) blockage of the promoter and/or noble metal (HCO3-, CO32-, SO42-, Cl- and ClO4- cases), and iii) interaction with the support surface (PO(4)(3-)case). The results can provide a new insight for the successful application of catalytic NO3- reduction technology with high N-2 selectivity to the contaminated groundwater system.
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