In this work, a new strategy has been reported for the portable detection of HS based on Fe-doped hydroxyapatite nanoparticles (Fe-HA) using a colorimetric paper test strip integrated with a smartphone platform. Fe-HA NPs were fabricated successfully via recycling waste coal ash. The obtained probe response toward HS was through a distinct visual color change. The sensing mechanism is based on the displacement reaction, in which PO is replaced by S. The prepared test strip shows high selectivity, and the other compounds containing thiol and sulfur anion have a negligible effect on the detection of HS. The designed scheme is applied for HS detection in the concentration range of 0.5-130 ppm with a limit of detection of 70 ppb. Furthermore, such a disposable sensor was used as a practical system for monitoring HS in actual water samples, suggesting the promising potential of this platform for suitable analysis of HS in an aqueous environment.