Structural regulation of electroplating sludge by a metal–organic framework synthesis method for an enhanced denitrification activity

Abstract

Electroplating sludge contained multi-metals and organics. In previous reports, electroplating sludges were usually recycled by direct calcination and pyrolysis for structural regulations. For the first time, a metal–organic framework synthesis method was utilized to regulate the structure of an electroplating sludge. In brief, the sludge was hydrothermally treated in solution of 1,3,5-trimesic acid, ethanol, and N,N-dimethylformamide. After this strategy, the sludge particle size was decreased; metals and organics formed coordination bond, and transformed oxygen-centered radicals to carbon-centered radicals; amorphous phases were re-crystalized to form well-dispersed crystals. As a result, the regulated sludge showed an enhanced denitrification activity. It removed 61.6% of nitric oxide (990 ppm) at a temperature as low as 150 °C. The activity was even close to 99.9% at 350 °C. What is more, the regulated sludge was characterized by plenty of free carboxylic groups and multi-metal catalytic centers, which make it a better catalyst than the pure-reagent-synthesized catalyst. Therefore, this paper put forward a novel strategy for the high value-added utilization of electroplating sludge.