Removal Of Heavy Metals From Wastewater By Ion Flotation With Plant-derived Biosurfactant Tea Saponin

Many industry including metals finishing, planting and mining acidic bring waste water containing cadmium, lead, copper, et al. Long-term ingestion of water containing higher concentration of heavy metals can cause many diseases such as stomach ailment, metal retardation, liver and kidney damage. Research in heavy metals removal and recovery are always a key problem in environmental protection.The methods frequently used for heavy metal removal from solutions include chemical precipitation, ion exchange, solvent extraction and electrolysis can remove heavy metals from concentrated solution. However, these methods are not good for the dilute solution .Ion flotation is an effective method to separate heavy metal ions from dilute solution. In ion flotation, surfactant serves as foam agent and flotation agent. As environment acceptable compounds, biosurfactants although have been used in a variety of environmental applications, little is known about the potential for biosurfactants application in ion flotation.Based on above theories, our research was focus on the following aspects and received several conclusions.The potential of plant-derived biosurfactant tea saponin to remove cadmium from wastewater was investigated. The main physicochemical parameters influencing the process, such as pH of the solution, the collector-cadmium ratio(molar ratio), the ionic strength (NaNO3 and Na2SO4), as well as kinetic parameters, such as flotation time and air flowrate were evaluated. Promising results have been obtained. The removal of cadmium is the best when the solution pH is 6.00, the collector- cadmium ratio(molar ratio) is 2∶1, air flotation is 0.15 l·min-1. Under the optimum conditions removal of cadmium was 85.87 %, the enrichment ratio of cadmium is 19.43. And when the collector to cadmium ratio is 2∶1, pH is 8.00, the removal efficiency is 70.97 %, and the enrichment ratio is 32.17. An increase in magnitude of ionic strength from 1×10-4 mol·L-1 to 1×10-1 mol·L-1, significantly decreased Cd2+ removal. The recovery fraction of Cd in foam is 79.62%.Based on the foregoing research results, the potential of tea saponin to remove cadmium, lead and copper from wastewater was investigated, and lauryl sodium sulfate was used as contrast. The effects of pH value, concentration of surfactants, ionic strength (NaCl and Na2SO4), and the frothers was studied. With the concentration of surfactant increases, the removal efficiency increased. The...