Removal of Metals from Industrial Sludge by Extraction with Different Acids
Resource
Journal of Environmental Science and Health A39 (8): 2205-2219
Journal
Journal of Environmental Science and Health
Journal Issue
8
Pages
2205-2219
Date Issued
2004
Date
2004
Author(s)
Abstract
This study addresses the feasibility of removing Cu and Ni from sludges of printed circuit board (PCB) plants by acidic extraction. Citric acid, acetic acid, hydrochloric acid, nitric acid, and sulfuric acid at various concentrations were experimentally examined to determine preferred conditions for removing Cu and Ni. Experimental results indicate that the removal ratios of Cu were 57% (citric acid), 79% (acetic acid), 81% (hydrochloric acid), 91% (nitric acid), and 92% (sulfuric acid), and that of Ni was 74% (citric acid), 70% (acetic acid), 75% (hydrochloric acid), 92% (nitric acid), and 93% (sulfuric acid), using 1 N extractants. The removal ratios obtained using sulfuric acid or nitric acid at a particular concentration were in the order Pb > Ni > Cu > Zn. The kinetic extraction results revealed that the extraction of Cu and Ni by nitric acid and sulfuric acid exhibited a lagphase after 60 min and the removal ratio was then around 90%. The kinetic results also revealed that the extraction rate constants of Cu and Ni increased with the concentration of the acid. The extraction rate constants of Cu and Ni followed the order sulfuric acid > nitric acid > acetic acid, and it also showed that Ni was more easily extracted than Cu from PCB sludge. The total percentages of Cu extracted by 1 N acetic acid, nitric acid, and sulfuric acid, determined in three replicate extractions were 78, 94, and 94%, and those of Ni were 89, 94, and 98%, respectively. The residue sludge, following three replicate extractions using 1 N acetic acid, nitric acid, and sulfuric acid, was further tested by toxicity characteristic leaching procedures (TCLP), and more than 15 mg/L of Cu was leached, exceeding the legal concentration in Taiwan. This observation reveals that the residue sludge following three replicate extractions by acids remained hazardous waste. Further treatment, such as solidification, must be performed before the sludge is disposed of.
Subjects
Acid extraction; Copper; Industrial sludge; Metal removal; Nickel
Other Subjects
Acetic acid; Extraction; Hydrochloric acid; Printed circuit boards; Reaction kinetics; Sulfuric acid; Extractants; Metal removal; Sewage sludge; acetic acid; acid; citric acid; copper; heavy metal; hydrochloric acid; nickel; nitric acid; sulfuric acid; acid extraction; article; electronics industry; extraction; extraction rate constant; hazardous waste; heavy metal removal; industrial sludge; kinetics; printed circuit board plant; removal ratio; residue sludge; solidification; stoichiometry; Taiwan; toxicity characteristic leaching procedure; toxicity testing; waste; waste management
Type
journal article
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