HEAVY-METAL REMOVAL WITH LIGNIN

Increasing discharges of toxic heavy metals and the concomitant environmental damage has resulted in stringent standards for effluent disposal. Techno-economic limitations of conventional metal removal methods dictate the development of alternate, inexpensive techniques to meet the discharge criteria. Heavy metal removal with lignin, a multifunctional group polymer easily recovered from pulp and paper industry waste, appears to be a potential solution. Copper and cadmium removals by solid lignin are governed by the pH of the metal solution, lignin dose and lignin / metal ratio. The optimum pH for maximum metal removal was 5.5 for copper (1.2 mg/gm lignin) and 6.5 for cadmium (2.5 mg/gm lignin). The optimum contact time was one hour. Metal removal was accompanied by release of hydrogen ions in solution. © 1990 by Marcel Dekker, Inc.