It is well established that organic matter can change the surface reactivity of oxide surfaces in subsurface systems.  This leads to a change in the conditions under which heavy metals will adsorb to these surfaces, influencing the fate and transport of the heavy metals.  Using batch adsorption experiments, extended X-ray absorption fine structure spectroscopy (EXAFS), Fourier transform infrared (FTIR) analysis and computational chemistry, we examined the effect of the low molecular weight organic acid, citric acid, on lead adsorption onto the surface of hematite nanoparticles.  Batch adsorption experiments showed enhanced lead adsorption at low pH in the presence of citrate and depressed in the neutral pH range.  FTIR and EXAFS results show that citrate and lead are both independently and competitively bound inner spherically to the hematite surface.  In addition, the EXAFS data provide evidence for a lead � citrate outer-sphere complex formed that was not visible in the FTIR data.

Enhancement and hindrance of lead adsorption to hematite in the presence of citric acid

245th National Meeting (2013)

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