Work

Comparison of the performance of inorganic ultrafiltration and organic nanofiltration membranes for removal of nitrate contamination of groundwater

Year: 2020

Type: article

Abstract: ABSTRACT Contamination from Moroccan agricultural activity and, specifically, nitrate (NO 3 – ) pollution is a major concern in groundwater supervision. This study aims to compare inorganic ultrafiltration (γ-Al 2 O 3 ) to organic nanofiltration membranes (NF90 and NF270 Dow/Filmtec, South Miami, USA) in terms of NO 3 – removal and permeate flux. The influence of experimental parameters (pH, applied pressure, ionic strength, and the variation of the chemical composition of feed solution) on the membranes’ performance, onto NO 3 – removal, was studied. The influence of the associated cation was also highlighted. The filtration experiments were first carried out on synthetic solutions, then on groundwater from two different Moroccan regions. The experimental filtration results demonstrated that the UF membrane underscores its position in NO 3 – removal among organic membranes (R(NF90) % > R(UF) % > R(NF270)%). The NO 3 – rejection depends on pH. The best rejections for NF90 and NF270 are, respectively, in the order of 70% and 41% at pH above 8, while the best rejection of 60% is found for γ-Al 2 O 3 UF at pH 7. The increase of NO 3 – concentration and multivalent anions, lead to a decrease in NO 3 – rejection. Ions’ valency and hydrated radius, as well as, membrane-solute electrostatic interaction have a drastic effect on NO 3 – rejection. The NF90 has the highest rejections since the separation is caused by dual forces, charge, and size effects. The electrostatic interactions during tight UF are more pronounced than NF270. Denitrification of Sidi Taibi groundwater by NF90, UF, and NF270, amounts, respectively, to approximately 64%, 56%, and 20% for 6 bar and natural pH. The total mineralization of water influences drastically on NO 3 – removal.

Source: Desalination and Water Treatment

DOI: 10.5004/dwt.2020.26444