Zinc removal from soil by washing with saponin obtained from Sapindus mukorossi

Soumyadeep Mukhopadhyay, Sumona Mukherjee, Mohd Ali Hashim, Jaya Narayan Sahu, Nadia Martinez-Villegas, Bhaskar Sen Gupta

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This study explores the possible application of a biodegradable plant-based surfactant saponin obtained from Sapindus mukorossi or soapnut, for washing zinc from contaminated soil. Batch experiments were conducted by varying pH, surfactant concentration and soil: solution ratio and compared to SDS, a synthetic surfactant. It was observed that soapnut was more efficient than SDS due to its lower pH. Also, the surfactants were more effective at higher concentrations. Soapnut solution removed more than 73% zinc while SDS solution could only wash out up to 31% of the total zinc from the soil under similar experimental conditions. pH played a very important role in zinc removal and at pH4, both soapnut and SDS removed nearly similar amount of zinc. Analysis of the FT-IR data suggested that saponin did not interact chemically with zinc, offering an option for reusing the surfactant after precipitating the zinc by using NaOH at pH of 10.3. Damage to the soil was found to be negligible. This study concludes that soapnut can be used as a washing agent for removal of Zn from high iron soil with minimal damage to the soil.
Original languageEnglish
Number of pages8
JournalJournal of Environmental Analytical Chemistry
Issue number4
Early online date31 Oct 2018
Publication statusE-pub ahead of print - 31 Oct 2018


  • Soil washing
  • Soapnut
  • Sapindus mukorossi
  • Zinc
  • Plant based surfactant


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