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The present investigation explored the feasibility of newly synthesised hydroxy apatite-carbon nanotubes based hybrid nanocomposite adsorbent and its potential application for the removal of Mn(II) from aqueous solution to avoid water pollution. The nanocomposite adsorbent was characterised using a scanning electron microscopic, energy dispersive x-ray spectroscopic, Fourier transform infrared spectroscopic, and BET surface area analysis. The effect of operating parameters namely initial pH (3–11), manganese concentration (50–200 mg/L), nanocomposite dose (0.5–6.0 g/L), and agitation speed (0–300 rpm) on the manganese uptake was investigated. Acidic pH does not favour the higher metal uptakes and the manganese uptake decreased with an increase in dose. The optimal pH and nanocomposite dose were found to be 6.0 and 2.0 g/L, respectively. The metal uptake capacity of nanocomposite was achieved as 70.95 mg/g. Langmuir and Freundlich isotherms were fitted to the experimental data and the Langmuir separation factor ( R L < 1) confirmed favourable adsorption. The pseudo-second-order model represented the data well with a rate constant of 2.26 × 10−3 g/mg. min. The synthesised material can be an alternative to other adsorbents for the effective separation of manganese from aquatic system. [ABSTRACT FROM AUTHOR]