Nitrates removal by bimetallic nanoparticles in water

Abstract

Nitrate contamination of groundwater has become a major environmental concern since nitrates are easily transferred from unsatured zone to the satured one, due to their solubility and low sorptivity on soil particles caused by their negative charge. The effectiveness and rapidity of the reduction of NO3- is strongly dependenton the contact time, the concentration of the reductive agent, the properties and composition of the surrounding medium (pH, dissolved oxygen concentration, heavy metals and organic matter concentration). The aim of this work was to investigate the effectiveness of nZVI and bimetallic nanoparticles of Fe/Cu in the remediation of nitrate-polluted groundwaters. nZVI and Fe/Cu nanoparticles were prepared by sodium borohydride reduction method at room temperature and ambient pressure. Results confirm that the decontamination of nitrate in groundwater via the in-situ remediation by Fe/Cu nanoparticles is environmentally attractive. Batch experiments were conducted on water samples contaminated in laboratoryusing NaNO3 to fix the initial nitrate concentration to 57.5 mg/L. The Cu/Fe0 ratio was fixed to 0.05 (w/w) andthe parameter investigated was the Fe0/NO3- weight ratio (5,10 and 15 w/w). During the tests the aqueous solution was analyzed to measure the evolution of NO3- and pH at 0, 30, 60, 90, 120 and 150 min. The results showed the increasing rate of reduction of nitrate by adding copper to ZVI particles; in fact fixing the Fe0/NO3- to 15 the tests without copper resulted in a complete removal within 150 min against the 60 min required by the tests with copper.