Effect of structural differences of pumice on synthesis of pumice-supported nFe 0 : removal of Cr (VI) from water

In this study, pumice from different regions of Turkey (Diyarbakir, Southeast Turkey and Bitlis, East Turkey) has been supplied and used as supporting material for nanoscale zero-valent iron (nFe 0 ). Native Bitlis pumice (NBP)-supported nanoscale zero-valent iron (BP-nFe 0 ) and native Diyarbakir pumice (NDP)-supported nanoscale zero-value iron (DP-nFe 0 ) were synthesized under the same conditions. Native pumice (NDP, NBP) and pumice-supported nFe 0 (DP-nFe 0 and BP-nFe 0 ) adsorbents were morphologically and structurally characterized by SEM, EDX, XRF and BET. When using NBP as support material, the iron content of the BP-nFe 0 increased 1.9-fold from 1.99 to 3.83%. However, iron content of NDP (2.08%) increased approximately 29 times after it is used as a support material in synthesis of DP-nFe 0 (60%). The removal potential of native pumice (NBP and NDP) and iron-modified pumice (BP-nFe 0 and DP-nFe 0 ) samples was investigated to remove Cr(VI) ions. The parameters of solution pH, initial metal concentration, contact time and the amount of adsorbent in the removal of chromium (VI) ions were investigated. Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Jovanovic isotherm models were used to evaluate the adsorption equilibrium data. The equilibrium adsorption was found so as to be well described by the Langmuir isotherm model for all the adsorbents studied. The maximum adsorption capacity of Cr(VI) ions for NDP, NBP, DP-nFe 0 and BP-nFe 0 was 10.82, 14.30, 161.29 and 17.39 mg/g, respectively. The rate of Cr(VI) removal was subjected to kinetic analysis using pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich models. Kinetic studies suggest that adsorption of NDP, NBP, DP-nFe 0 and BP-nFe 0 described more favorably by the pseudo-second-order kinetic model. The results showed that NDP is a much better support material for nFe 0 when compared to NBP.