Volatilization and sorption of dissolved mercury by metallic iron of different particle sizes: Implications for treatment of mercury contaminated water effluents

•Volatilization and adsorption of Hg from aqueous solutions by Fe0.•Hg volatilization accounts only for a very small fraction.•Temporal changes in the SSA of Fe0 particles are a function of water chemistry.•Nano-size Fe0 particles show higher rates of Hg removal than bulk Fe0 particles. Batch experiments were conducted to investigate the interactions between metallic iron particles and mercury (Hg) dissolved in aqueous solutions. The effect of bulk zero valent iron (ZVI) particles was tested by use of (i) granular iron and (ii) iron particles with diameters in the nano-size range and referred to herein as nZVI. The results show that the interactions between Hgn+ and Fe0 are dominated by Hg volatilization and Hg adsorption; with Hg adsorption being the main pathway for Hg removal from solution. Hg adsorption kinetic studies using ZVI and nZVI resulted in higher rate constants (k) for nZVI when k values were expressed as a function of mass of iron used (day−1g−1). In contrast, ZVI showed higher rates of Hg removal from solution when k values were expressed as a function iron particles’ specific surface area (gm−2day−1). Overall, nZVI particles had a higher maximum sorption capacity for Hg than ZVI, and appeared to be an efficient adsorbent for Hg dissolved in aqueous solutions.