Thermally Tuned Novel Metal Borate Decorated Carbon Nanocomposites for Efficient Rhodamine B Uptake

Rhodamine b is a persistent dye that harms aquatic life through strong color stability, toxic effects, and disruption of primary production. It also endangers human health through cellular oxidative stress and organ-specific impacts, so its release must be tightly controlled. This study reports a facile Pechini sol-gel route to produce novel Mg 2 B 2 O 5 /Ni 3 B 2 O 6 /SrB 2 O 4 /SrO(B 2 O 3 ) 2 /MgSrB 2 O 5 /C nanocomposites denoted MSN500 at 500 and MSN700 at 700 o C for efficient sequestration of rhodamine b dye from water. XRD confirms purposeful multiphase construction and yields mean crystallite sizes of 55.5 nm regarding MSN500 in addition to 68.8 nm regarding MSN700, which reflects thermally driven growth. EDX verifies the targeted elements and shows for MSN500 the atomic percentages: C (16.5 %), O (45.5 %), Mg (7.5 %), Ni (14.1 %), Sr (10.3 %), and B 6.1 %. The atomic percentages for MSN700: C (12.1 %), O (55.2 %), Mg (7.9 %), Ni (9.3 %), Sr (8.2 %), and B (7.3%), which indicates lower residual carbon and higher oxidation at 700 o C. FE-SEM reveals MSN500 as agglomerated plate-like clusters, while MSN700 displays rods together with spherical and plate-like grains. HR-TEM shows MSN500 as fused spherical and elliptical nanoparticles, while MSN700 exhibits larger plate-like and polygonal particles with clearer boundaries. Maximum adsorption capacities are 348.43 mg/g regarding MSN500 in addition to 280.11 mg/g regarding MSN700. Thermodynamic and kinetic assessments indicate an exothermic, spontaneous, and physical process, and the uptake follows the pseudo-first-order model in addition to the Langmuir isotherm. Also, the spent adsorbents regenerate readily with HCl and maintain high removal over five repeated cycles, which supports practical reuse.