The photocatalytic reduction of NO3- to N2 with ilmenite (FeTiO3): Effects of groundwater matrix

WATER RESEARCH

卷:200

Article

Silveira, Jefferson E.¹  Ribeiro, Alyson R.^1,2  Carbajo, Jaime¹  Pliego, Gema¹  Zazo, Juan A.¹  Casas, Jose A.¹ 

[1] Univ Autonoma Madrid, Dept Chem Engn, Madrid 28049, Spain

[2] Univ Estadual Campinas, Inst Chem, Dept Analyt Chem, POB 6154, BR-13084971 Campinas, SP, Brazil

关键词: Nitrate;    Photo-reduction;    Groundwater;    Ilmenite;    Water conditioning;   

DOI  :  10.1016/j.watres.2021.117250

来源: Elsevier

【 摘 要 】

This work analyzes the role of natural groundwater, as well as the effect of HCO3-, Ca2+, Mg2+, K+, SO42- and Cl- concentrations, upon the photocatalytic nitrate reduction using ilmenite as catalyst and oxalic acid as hole scavenger. The nitrate removal and the selectivity towards N-2 are significantly limited compared to previous experiments using ultrapure water matrix. Calcium (Ca2+), bicarbonate (HCO3-) as well as pH are claimed as the major controlling factors related to the process yield. Thus, Ca2+ promotes the formation of insoluble oxalate microcrystals, reducing the amount of hole scavenger available. The presence of HCO3- leads to a steeply increase in the pH value, favoring the adsorption onto the ilmenite surface of ions OH(-)instead of NO3-, NO2- and C2O42. The aforementioned issues are overcome by working with C2O42-/NO3- ratio well above the stoichiometric one, that also maintains the pH value in an acid range. A completed depletion of the starting NO3-, the no detection of either NO2- or NH4+ in the aqueous phase, and a selectivity towards N-2 above 95% were achieved using two times the stoichiometric dose. (C) 2021 The Author(s). Published by Elsevier Ltd.

【 授权许可】

Free