Removal of hardness agents, calcium and magnesium, by natural and alkaline modified pumice stones in single and binary systems

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• 作者：Mohammad Noori Sepehr^a ; Mansur Zarrabi^a ; ^{mansor62@gmail.com} ; Hossein Kazemian^b ; Abdeltif Amrane^c ; Kamiar Yaghmaian^d ; Hamid Reza Ghaffari^e
• 关键词：Calcium ; Magnesium ; Adsorption ; Modification ; Batch system
• 刊名：Applied Surface Science
• 出版年：2013
• 出版时间：1 June, 2013
• 年：2013
• 卷：274
• 期：Complete
• 页码：295-305
• 全文大小：2506 K

文摘

Natural and alkaline modified pumice stones were used for the adsorption of water hardening cations, Ca²⁺ and Mg²⁺. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. At equilibrium time and for 150 mg/L of a given cation, removal efficiencies were 83 % and 94 % for calcium and 48 % and 73 % for magnesium for raw and modified pumices, respectively. The optimal pH for raw and modified pumices were found to be 6.0, leading to the removal of 79 and 96 % of calcium and 51 and 93 % of magnesium by 10 g/L of raw and modified pumice adsorbents, respectively. Maximum adsorption capacities were 57.27 and 62.34 mg/g for Ca²⁺ and 44.53 and 56.11 mg/g for Mg²⁺ on the raw and modified pumices, respectively. Ca²⁺ and Mg²⁺ adsorption capacities of the pumice adsorbents decreased in the presence of competing cations. Less than 300 min were needed to achieve 99 and 92 % desorption of the adsorbed Ca²⁺ and 100 and 89 % of the adsorbed Mg²⁺ from the natural and modified pumices, respectively. After treating synthetic water solution simulating an actual water stream with the alkali-modified pumice, total hardness of the treated sample met the required standard for drinking water, namely below 300 mg/L of CaCO₃ (297.5 mg/L). The studied pumice adsorbents, and especially the treated pumice, can be therefore considered as promising low cost adsorbents, suitable for the removal of hardness ions from drinking water.