Phosphorus Speciation in Sludge from Nickel Electroplating

Abstract

The recycling of secondary resources to close material cycle loops should reduce the consumption of natural resources and thus help to reduce the environmental impact. For recycling, it is crucial to consider not only the nickel (Ni) content in the secondary resources, such as Ni plating waste liquids and sludge, but also the impurity levels, particularly the phosphorus (P) concentration. This study characterized the P species in three sludges from Ni electroplating processes using P K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The Ni and P concentrations in the sludges ranged from 11 to 41% and 2,800 to 24,000 ppm, respectively, depending on the type of sludge. The P K-edge XANES analysis identi ed phosphates and organic P as the major P species in the sludges, and hypophosphite and phosphite species as minor species. These ndings provide detailed knowledge that should help to control P in Ni electroplating sludge.

Microwave Drying Kinetics of Chromium-Rich Electroplating Sludge

“…According to Figure 12a, the microwave drying process of CRES could be roughly separated into three successive stages considering the variations of drying rate constant with time and load mass. Figure 12b shows that the drying rate constant was basically negatively correlated with the load mass before 110 s, agreeing with the dependence shown by Equation (6). Thus, in this stage, the drying process was limited by external diffusion.…”

“…Untreated electroplating sludge has a pretty high moisture content, up to 80 wt% [5,6]. Drying electroplating sludge can reduce its quantity and volume with the retention of heavy metal ions.…”