This work consists of the removal of nickel by sulfide precipitation from an industrial electroplating wastewater and characterization of the produced sludge. Tests are carried out in a perfectly stirred batch reactor on electroplating industrial solution and synthetic solution prepared in the laboratory. The aim is to evaluate the impact of complexing agents formed during precipitation of metal ions in the industrial effluent. The concentration of nickel in both solutions is 100 mg/L. The operating conditions for sulfide precipitation process are optimized: pH, molar ratio [S=]/[Ni2+] and dosage of S= ions. For an initial pH of 5 and an equimolar ratio of [S=]/[Ni2+]:1/1, the results show that the removal efficiency of Ni2+ ions is approaching 91 and 94% for industrial and synthetic solutions, respectively. Otherwise, for the same pH value in supersaturation conditions ([S=]/[Ni2+]:1.5/1), the removal efficiency is approaching 62 and 92% for industrial and synthetic solutions, respectively. For an effective metal removal, the optimal dosage of sulfide ions was evaluated. For 33 mg/L of S=, the removal efficiency of Ni2+ is approximately 90%. The resulting sludge has been characterized by x-ray diffractometry, scanning electron microscopy, infrared spectroscopy and thermal analysis. It consists essentially of millerite and nickel oxide.

No abstract

In aerated processes, the oxygen transfer was limited by the presence of the suspended matter as colloid and the dissolved matter, which might decrease the biological degradation effectiveness. In this publication, three series of tests were conducted to study possibilities to reduce these matters: bacterial adaptation which was conducted in a biological aerated filter, adsorption/biosorption conducted on a biological aerated filter with a biofilm of adapted bacteria and percolation in a bioreactor with a packed plastic media. All the tests carried out gave convincing results concerning turbidity and chemical oxygen demand, as parameters limiting the oxygen transfer for a better biodegradation. The advanced adaptation improved their elimination. So, all these treatment techniques could be used as pretreatment processes; in addition, they required very little energy, particularly adsorption/biosorption and percolation.

No abstract