Removal of heavy metals from soils by chelation with unfractionated fulvic acid fractions, EDTA, and citrate

In situ remediation of metal contaminated soils and groundwaters can be accomplished by a number of innovative-engineered technologies, which include flushing with organic chelating agents. This research studied the ability of unfractionated fulvic acids extracted from manure, a ubiquitous and low cost material, to effectively chelate copper, cadmium, lead, and nickel from ten different metal amended soils. EDTA and citrate were also tested and compared to fulvic acid extraction efficiencies. Experiments were divided into two sections, chelate comparison and sequential extraction. Metal removal efficiencies for EDTA were 49% to 100% for copper, 60% to 90% for lead, 23% to 97% for nickel, and 31% to 83% for cadmium; removal efficiencies for citrate were 15% to 62% for copper, 4% to 54% for lead, 4% to 50% for nickel, and 0% to 37% for cadmium; and extraction efficiencies for fulvic acid were 5% to 95% for copper, 1% to 94% for lead, 32% to 100% for nickel, and 19% to 87% for cadmium. Three sequential extractions with fulvic acid removed 18% to 100% copper, 9% to 99% lead, 39% to 99% nickel, and 30% to 90% cadmium. The data illustrate the potential of non-toxic fulvic acids as a chemically enhanced flushing agent for in-situ remediation.