Novel carbonate, oxide, and hydroxide nanohybrids based on Mg, Ba, and Ca for efficient Safranin O dye adsorption

Safranin O dye threatens human health and aquatic systems through persistent color and cellular toxicity. Its presence in water lowers light transmission and suppresses primary production. Novel MgO/BaCO₃/CaCO₃/Ca(OH)₂ nanocomposites were synthesized by a facile Pechini sol-gel route at two set temperatures (600 and 800 °C) and are denoted BMC600 and BMC800, respectively. XRD confirms multiphase products with an average crystal size of 60.52 nm regarding BMC600 and 68.64 nm regarding BMC800. EDX detects C, O, Mg, Ca, and Ba with atomic percentages for BMC600 equal to 13.2, 57.8, 12.0, 12.7, and 4.3% and for BMC800 equal to 10.3, 53.9, 11.2, 17.9, and 6.7%. FE-SEM shows agglomerated faceted grains in BMC600 with a mean grain size of 0.16 μm and rounded grains in BMC800 with a mean grain size of 0.44 μm. HR-TEM reveals quasi-spherical particles for BMC600 with a mean diameter of 28.52 nm and larger near-spherical particles for BMC800 with a mean diameter of 164.92 nm. Maximum adsorption capacities reach 318.47 mg/g regarding BMC600 in addition to 270.27 mg/g regarding BMC800. Kinetic analysis follows the pseudo-first-order model. Equilibrium follows the Langmuir isotherm. Thermodynamic results indicate exothermic, spontaneous, and physical adsorption with negative ΔH°, negative ΔG°, and positive ΔS°. Regeneration with HCl enables desorption up to 99.74% and stable reuse over five cycles. Findings demonstrate efficient dye removal due to multiphase synergy and scalable synthesis.