Manganese sulphide nanoparticles (MnS NPs) and their application on the removal of triclosan in water

Manganese sulphide nanoparticles (MnS NPs) have emerged as promising adsorbents for environmental remediation due to their unique physicochemical properties. Therefore, in this study, MnS NPs were prepared using a rapid solid-state synthesis method at temperatures of 100–400 °C. The surface, structural, and morphological properties of MnS NPs were determined using various analytical characterisation techniques, including FTIR, XRD, TEM, SEM, EDX, and TGA. The results demonstrated that increasing the synthesis temperature leads to a reduction in particle size, enhanced crystallinity, and altered surface chemistry, which collectively improve the adsorption capacity. The adsorption performance of MnS NPs was evaluated for the removal of triclosan from water through optimised batch adsorption experiments. The kinetic data for triclosan adsorption onto MnS NPs were well described by the pseudo-first-order kinetic model at higher triclosan concentrations (30–50 mg/L) and by the pseudo-second-order kinetic model at 20 mg/L. Additionally, kinetic data reveal that the adsorption mechanism is primarily governed by intra-particle diffusion at low triclosan concentrations. The equilibrium was well fitted to the Langmuir isotherm model, and the maximum adsorption capacity of triclosan onto MnS NPs was 145 mg/g. The adsorption process involves a synergistic interplay of hydrogen bonding, hydrophobic interactions, and electrostatic forces, as revealed by FTIR studies. Interference studies with common pharmaceuticals confirm competitive effects on triclosan adsorption, highlighting the importance of considering complex water matrices. Regeneration tests show that MnS NPs retain high adsorption efficiency over multiple cycles, underscoring their potential for sustainable water treatment. Overall, MnS NPs exhibit excellent triclosan adsorption capability, with synthesis temperature serving as a key parameter to tailor their properties for water purification applications.