Improved sea water quality by removal of the total hardness using static step-by-step deposition and extraction technique as an efficient pretreatment method

• A pretreatment method of sea water from total hardness and scale formation.
• Over 91.5% removal of total hardness by using static step-by-step deposition and extraction technique.
• Several experimental controlling factors were evaluated.
• The number of dipping cycles and exposed surface area are highly significant.
• The pH value of sea water dropped from 8.0 to 6.5.

The static step-by-step deposition and extraction technique (SbS-DET) was explored as a prior methodology for efficient and low cost treatment of total hardness in sea water. Removal of Ca(II) and Mg(II) ions from sea water samples was based on sequential surface deposition in the form of 8-hydroxyquinolate complexes. Several important experimental controlling factors were examined, optimized and evaluated in this study such as the effect of dipping time, reaction temperature, initial concentration of 8-hydroxyquinoline ligand, number of dipping cycle and exposed surface area. The results of this study refer to an excellent and efficient removal of total hardness from the investigated sea water samples. The number of dipping cycle and exposed surface area were characterized from this study as the most important experimental controlling factors. The total hardness was dropped from 4629 to 381.9 mg L−1 as CaCO3 with a 91.75% removal value by using 30 dipping cycle, 3 min dipping time and 76 cm2 surface area. The same trend was also obtained by producing a 91.47% removal value of the total hardness when the exposed surface area was used as 114 cm2. The progress of SbS-DET was also characterized by a gradual drop in the pH value of sea water from 8.0 to 6.5 upon completion of the removal process.

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