Remediation of water contamination using catalytic technologies

Remediation of contaminated ground and underground water is becoming a critical issue in Europe and worldwide. We discuss here the role of catalysis in water remediation, with reference to two specific examples of catalytic water remediation technologies: (i) the elimination of nitrate and pesticides from water contaminated as a result of agricultural practices and (ii) the conversion of methyl tert-butyl ether (MTBE) in contaminated underground water. Of particular interest is a technology based on catalytic membranes for remediation of water contaminated by nitrate, which offers various advantages with respect to conventional technologies. Using a Pd-Cu-based catalytic membrane, a reaction temperature below 15 °C, a mixed 4:1 CO2:H2 feed and controlling bulk solution pH by HCl addition, it is possible to obtain a nitrate conversion higher than 80% even with ammonium ion formation below 0.5 ppm, i.e. the maximum concentration allowed to meet the requirements for drinking water quality. In MTBE conversion in contaminated underground water, acid zeolites with suitable pore structures (channel structure and pore openings) such as H-ZSM-5 and H-BEA can be used as catalytic permeable reactive barriers for in situ remediation. These zeolites not only act as adsorbents for both MTBE and its reaction products, but also effectively catalyze the hydrolysis of MTBE to t-butyl alcohol (TBA) and methanol (MeOH) which then can be rapidly biodegraded by indigenous microorganisms.