Patent ID: 7419605

Claim:
A method of removing dissolved metal contaminants from water, wherein said metal contaminants comprise one or more of mercury, chromium, copper, lead, nickel, zinc, and aluminum, comprising the steps of: (a) dispersing lignin derivatives in said dissolved metal-contaminated water, said lignin derivatives comprising one or more of lignosulfonates, kraft lignin and sulfonated kraft lignin salts to form a lignin-metal complex; (b) dispersing a coagulant comprising a ferric salt in the mixture formed in step (a), the mass ratio of the lignin derivatives to the coagulant being at least 1:1; (c) adjusting the ph of the mixture formed in step (b) to a pH in the range of 4-10, causing the formation of a floc including hydrolyzed coagulant and said lignin-metal complex; (d) allowing said floc to settle, resulting in a liquid and a sludge; and (e) separating said sludge from said liquid.