Natural Zeolites Application as Sustainable Adsorbent for Heavy Metals Removal from Drinking Water

Background: There are great resources of natural zeolite in Iran. Zeolite, an inorganic ion-exchanger, may be used as a suitable technical-economical solution for water treatment in many regions of Iran. In this study, the characterization of natural zeolite natrolite and the feasibility of removing hardness, cations, and anions were investigated. Methods: First, zeolite composition and type were determined using X-ray Fluorescence (XRF), thermal analysis, and infrared spectrometer. Also, cation exchange capacity (CEC) and its impact on water hardness reduction evaluated. Then, isotherm curves for Fe, Cr, Al, Bi, Cd, Mn, Ca, Mg, Ag, Ni, Zn, Cu, Pb, and their disposition to zeolite phase besides removal rate of the mentioned cations in analyzed water samples identified. Eventually, zeolite structure was rectified using surfactant (HMNDA) for anions removal. Results: Natrolite zeolite was more effective for waters with higher hardness, but it turned out to be moderate for waters with lower hardness. The ability of natrolite zeolite for permanent hardness removal was more than others and was less for temporary hardness. Also, the natrolite zeolite was more effective in removing non-heavy metal cations and by increasing the HMNDA concentration, arsenate anion removed fast from water samples. However, by pH increases in the water sample, the arsenate anion removal arbitrarily changed : less in pH=3. But the removal efficiency got better in alkaline pH. It is obvious that by increasing the pH of water samples, the removal efficiency will decrease. In spite of that, the removal efficiency of chromate ion , in acidity pH, was more than alkaline. The maximum removal of Cr (VI) occurred in acidic media at pH<1.5. Conclusion: The natrolite zeolite could remove different heavy metals from drinking water. Moreover, the removal efficiency of natrolite zeolite was enhansed by surfactant modification.