Copper Sludge Research Articles

Sulfidation treatment of copper-containing plating sludge towards copper resource recovery

The present study is concerned with the sulfidation treatment of copper-containing plating sludge towards copper resource recovery by flotation of copper sulfide from treated sludge. The sulfidation treatment was carried out by contacting simulated or real copper plating sludge with Na 2S solution for a period of 5 min to 24 h. The initial molar ratio of S 2− to Cu 2+ (S 2− to Me 2+ in the case of real sludge) was adjusted to 1.00, 1.25 or 1.50, while the solid to liquid ratio was set at 1:50. As a result, it was found that copper compounds were converted to various copper sulfides within the first 5 min. In the case of simulated copper sludge, CuS was identified as the main sulfidation product at the molar ratio of S 2− to Cu 2+ of 1.00, while Cu 7S 4 (Roxbyite) was mainly found at the molar ratios of S 2− to Cu 2+ of 1.50 and 1.25. Based on the measurements of oxidation–reduction potential, the formation of either CuS or Cu 7S 4 at different S 2− to Cu 2+ molar ratios was attributed to the changes in the oxidation–reduction potential. By contrast, in the case of sulfidation treatment of real copper sludge, CuS was predominantly formed, irrespective of S 2− to Me 2+ molar ratio.

Copper dissolution and electrochemical behavior in EDTA- and EDA-based solutions for steam generator chemical cleaning

Copper dissolution and electrochemical behavior have been investigated in order to find out which parameters are critical and important during the two major copper removal processes for chemical cleaning of nuclear steam generator and to evaluate safety aspects and effectiveness of these processes. Hydrogen peroxide was very effective for the process using EDTA-based solution at 38 °C to control the corrosion potential of copper into an optimum potential range from −0.3 to +0.2 V for copper sludge dissolution. Corrosion rates of carbon steel SA 285 Gr.C and Alloy 600 were very small in this potential range. The process using EDA-based solution at 60 °C was effective to dissolve copper sludge if the corrosion potential of copper could be controlled above −0.3 V. However, it was very difficult under the laboratory conditions to raise its corrosion potential to this range by air blowing and stirring.

Response of sweetgum to mycorrhizae, phosphorus, copper, zinc, and sewage sludge

A recent study has suggested that sweetgum (Liquidamberstyraciflua L.) differs from other species in that its marked response to mycorrhizae is not due to improved nutrient uptake. To investigate this possibility, sweetgum seedlings were grown in a 1:1:1 mix of peat, sand, and sandy loam treated factorially with: (i) 0, 50, or 500 ppm P; (ii) 0 or 5 ppm Cu; (iii) 0 or 8 ppm Zn, and (iv) Glomusfasciculatus Gerdemann and Trappe or no mycorrhizal inoculum. After 5 months' growth in the greenhouse, nonmycorrhizal seedlings receiving 500 ppm P were growing at the same rate as P-fertilized mycorrhizal seedlings and foliar P concentrations were higher in the mycorrhizal treatments. Mycorrhizae also alleviated a minor copper deficiency which occurred at the high level of P in the nonmycorrhizal treatments. The benefit of mycorrhizae to sweetgum is therefore a typical nutrient response, which may have been overlooked in previous work with this species by use of too narrow a range of phosphorus levels.