Enhanced Arsenic Adsorption to Magnetite Nanoparticles with Zinc

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Recent research published in the journal Water Research has revealed a significant enhancement in arsenic adsorption to magnetite nanoparticles in the presence of a small amount of zinc ions. The study, conducted by W.C. Yang and colleagues at Nankai University, found that the addition of less than 3 mg/L of zinc ions to the arsenic solution prior to the addition of magnetite nanoparticles resulted in an increase in arsenic removal from 66% to over 99% for arsenate and from 80% to 95% for arsenite. The researchers attributed the enhanced adsorption to the formation of a ternary surface complex by zinc, arsenic, and magnetite nanoparticles.

Key Takeaways:

  • Arsenic adsorption to magnetite nanoparticles at neutral or slightly basic pH can be significantly enhanced with a trace amount of Zn2+ due to the formation of a ternary surface complex.
  • The addition of less than 3 mg/L of Zn2+ to the arsenic solution prior to the addition of magnetite nanoparticles resulted in an increase in arsenic removal from 66% to over 99% for arsenate and from 80% to 95% for arsenite.
  • The adsorption-enhancement effect of Zn2+ was not observed at pH 4.5-6.0, nor with ZnO nanoparticles, nor with surface-coated Zn-magnetite nanoparticles.
  • The enhanced arsenic adsorption in the presence of Zn2+ cannot be due to reduced negative charge of the magnetite nanoparticles surface by zinc adsorption.
  • Other cations, such as Ca2+ and Ag+, failed to enhance arsenic adsorption.
  • The researchers tested and ruled out several potential mechanisms that could have caused the enhanced adsorption of arsenic.

Statistics:

  • Initial arsenic concentration: 100 μg/L,
  • Percentage of arsenic removal by magnetite nanoparticles at pH 4.5-6.0: 66% and 80%,
  • Percentage of arsenic removal by magnetite nanoparticles at pH 8.0 with 3 mg/L Zn2+ addition: 99% for arsenate and 95% for arsenite,
  • Adsorption rate increase with Zn2+ addition: significant.
  • pH range for enhanced arsenic adsorption: 8.0,
  • Concentration of Zn2+: less than 3 mg/L.
  • Country: People's Republic of China, Tianjin.

Sources:

  • Yang, W.C., et al. (2010). pH-dependent effect of zinc on arsenic adsorption to magnetite nanoparticles. Water Research, 44(19 Sp. Iss), 5693-5701.
  • Chen, W. (Contact Information), Nankai University, College Environmental Science & Engineering, Tianjin Key Laboratory Environmental Remediat & Pollut Contro, Minist Education, Key Laboratory Pollut Processing & Environmental Criter, Wei Jin Rd. 94, Tianjin 300071, People's Republic of China.
  • Pergamon-Elsevier Science Ltd. (Publisher's contact information for the journal Water Research), The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, England.