Comparative metal (Cu, Ni, Zn, total Cr, and Fe) removal from galvanic sludge by molasses hydrolysate

BACKGROUND: The objective of this study was to evaluate the chemical extraction efficiency of five metals (Cu, Ni, Zn, total Cr, and Fe) from galvanic sludge using molasses hydrolysate produced from molasses, a by-product of the sugar industry. The study was also aimed to compare the extraction efficiency of the molasses hydrolysate with those of nitric acid and EDTA. RESULTS: The experimental results showed that the metal removal (%) increased with extracting solution concentration, but decreased with increasing solid: liquid (S: L) ratio. The highest removal efficiencies using molasses hydrolysate were: Cu 90%; Ni 100%; Zn 90%; total Cr 100%, and Fe 81% at 10 min extracting time and S: L = 1: 10 g mL(-1). CONCLUSION: Molasses hydrolysate was found to be more effective than nitric acid and EDTA in the extraction of metals from the sludge. It was concluded that although using HNO3 was more economical than Na(2)EDTA and molasses hydrolysate, using molasses hydrolysate which is a novel, environmentally friendly, biodegradable extracting agent would be appropriate to prevent secondary pollution. (C) 2013 Society of Chemical Industry