Water Softening Performance of Crystalline α-Zirconium Phosphate
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Alkalinity, Adsorption, α-Zirconium Phosphate, Hardness, Isotherm
Abstract
This research focuses on drinking water softening and treatment using a simple and novel approach based on an easily prepared inorganic ion exchange material (α-zirconium phosphate). To the best of our knowledge, this is the first study to investigate the use of α-zirconium phosphate for the removal of hardness and alkalinity from water, although it has previously been applied for heavy metal removal. The study showed that percentage hardness removal decreased, while exchange capacity increased as the initial ion concentration increased. With adsorbent doses ranging from 10 to 60 g/L, percentage removal increased for both hardness and alkalinity. The contact time study showed no significant effect on percentage removal, while exchange capacity was approximately 3.3 times higher for hardness than for alkalinity. The Langmuir isotherm model showed a good fit for both hardness and alkalinity (R² = 0.9966 and 0.9950, respectively). The Freundlich isotherm model indicated physisorption behaviour, with n_F values of 3.08 for hardness and 20.29 for alkalinity. The Temkin isotherm model also showed a good fit with the experimental data (R² = 0.9259 for hardness and 0.9694 for alkalinity). The heat of adsorption (B) was found to be 9 kJ/mol for hardness, indicating physisorption, and 444 kJ/mol for alkalinity, suggesting chemisorption. Pseudo-first-order and pseudo-second-order kinetic models were applied and showed good agreement with the experimental data (R² = 0.9635 and 0.9999 for hardness, and 0.9195 and 0.9066 for alkalinity, respectively).
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References
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