Abstract

Cyclopentane hydrate desalination has emerged as a promising low-energy alternative to con- ventional desalination because water forms hydrate lattices that encapsulate cyclopentane while excluding dissolved salts. In addition to producing fresh water, the proposed process analyzes streams such as seawater, hydrate-concentrated brine, and post-recovery process solutions that require accurate Ca2+ and Mg2+ determination for process monitoring, mass balance calculations, and resource recovery optimization. These ions are also precursors for high-value products such as struvite fertilizers, magnesium oxide nanoparticles, and hydroxyapatite materials. The process centers on an inexpensive ethylenediaminetetraacetic acid (EDTA) complexometric titration for Mg2+ and Ca2+ determination in diverse matrices associated with cyclopentane hy- drate desalination. It is compared for performance with flame atomic absorption spectroscopy (AAS). Total (Ca2+ + Mg2+) concentration was determined via titration with standardized EDTA at pH 10 using Eriochrome black T. Ca2+ concentration was determined at pH 12 using calcon after Mg2+ precipitation as magnesium hydroxide, and Mg2+ concentration was calculated as the dif- ference between the total and Ca2+ concentrations. Analytical conditions were optimized with respect to sample dilution factor, sodium chloride concentration, pH, indicator dosage, and poten- tial Sr2+ and boron species interferences. The proposed method demonstrated excellent linearity (R2 > 0.999), limits of detection (4.5 mg L−1 and 5.5 mg L−1 for Ca2+ and Mg2+, respectively,) recov- eries (98%–103%,) and relative standard deviations (below 3.5%). Statistical comparison with flame AAS showed excellent agreement without significant differences in precision or mean values based on F tests and Student's t tests at the 95% confidence level. The proposed method provides an ac- curate and economical analytical tool for Mg2+ and Ca2+ determination across multiple matrices and supports sustainable resource recovery.