Chelation of heavy metals by potassium butyl dithiophosphate

摘要

Potassium butyl dithiophosphate (PBD) was developed and introduced as a new chelating agent for heavy metal removal. The synthesized PBD were characterized by IR and NMR. The effects of pH, chelating agent dosage, and other heavy metal ions on the performance of PBD in Cd 2+ removal from water are investigated. Experimental results showed that the chelating agent could be used to treat acidic heavy metal wastewater. The Cd 2+ removal was not affected by solution pH value within the range of 2 to 6. The Cd 2+ removal rate could reach over 99%. Therefore, the deficiency of the precipitation process using hydroxide under alkaline condition can be overcome. Without the need for pH adjustment, the method could save on costs. If Cd 2+ co-exists with Pb 2+ and Cu 2+ , the affinity of the chelating agent with these three heavy metal ions was in the order of: Cu 2+ > Pb 2+ > Cd 2+ . Through PBD chelating precipitation, all the contents of Pb 2+ , Cd 2+ , and Cu 2+ in wastewater met the standard levels through a one-step treatment. The one-step treatment process was superior to the process (sectional treatment is required) of precipitation with hydroxide. When the pH was between 3 and 11, the amount of leached chelated Cd 2+ was much lower than that obtained by precipitation with hydroxide. Therefore, the risk of environmental pollution could be further reduced.