Magnesium adsorption on modified clinoptilolite zeolites

Most of the water resources should be treated for purification before consumption, because of existing various chemical components, such as hardness, nitrate contamination and heavy metals. Among these compounds, water hardness can appear problematic in some cases. In general, water supplies with total hardness higher than 500 mg/L are not acceptable for most of the domestic consumptions. Hardness in water refers to existing divalent ions, such as iron, manganese, calcium and magnesium. Among them, calcium and magnesium are known as the dominant species for water hardening and most of treatment method was done to decrease these two cations [1]. In other way, application of differerent natural and synthetic zeolites for purification and treatment of water have gained great attentions in recent years. Clinoptilolite is one of these natural zeolites [2] that its application was investigated for adsorption of magnesium in this work.Firstly, the natural Clinoptilolite was modifed with the following basic and acidic solutions: NaOH 1.0 M, NaOH 0.1M, HCl 1.0 M and HCl 0.1 M. The obtained modified zeolites were characterized by BET and XRD techniques. Then, the efficiency of these modified zeolites were compared with unmodified clinoptilolite. The obtained results for removal of Mg2+ by these modified zeolites were: 38%, 46%, 0.16% and 14% for NaOH 1.0 M, NaOH 0.1M, HCl 1.0 M, HCl 0.1 M modified Clinoptilolites, respectively. Whereas, the obtained removal efficiency for the unmodified clinopltiolite was 0.81%. Therefore, the NaOH 0.1M modified Clinoptilolite was used as the selected modified adsorbant in the further experiments. In the final stage, the effect of experimental condition on the removal process was studied; that the obtained contact time was 2 hours, and the obtained mass of adsorbent was 0.3g.