Hybrid process for the purification of water contaminated with nitrites: Ion exchange plus catalytic reduction

MENDOW, GUSTAVO; GROSSO, CÉSAR I.; SÁNCHEZ, AGUSTINA; QUERINI, CARLOS A.

CHEMICAL ENGINEERING RESEARCH & DESIGN

INST CHEMICAL ENGINEERS

Año: 2017

0263-8762

Water polluted with nitrites represents a big risk to human health. In this work,palladium supported on macroporous anionic exchange resin was used in the catalyticnitrite reduction. This process is compared with the traditional ion exchange procedureusing the same catalytic resin. Both, the resin and the catalyst behaviour were evaluatedin a fix-bed reactor, feeding water containing nitrites and other competitor ions, such as3sulphate, bicarbonate, and chlorides, and adjusting the pH with carbon dioxide. Whenfeeding water containing only nitrites, it was observed that the catalytic reduction makesit possible to treat 55% more water than when using the ion exchange process, at thesame level of nitrites elimination. Moreover, in steady state it was possible to obtain anitrite conversion to nitrogen of 54% with high selectivity, obtaining an ammoniumconcentration lower than 0.2 mg/L. In the case of having other ions present in thesystem, both the conversion and the selectivity decreased. A regeneration strategy isalso developed, using a very low hydrogen flow rate at atmospheric pressure and roomtemperature. This treatment leads to the reduction of more than 99% of the nitritespresent in the contaminated water. The catalyst was used in several consecutive cyclesmaintaining a very good performance, even in the presence of competitor ions. Theprocess was scaled up to a pilot level obtaining identical results.K