La-doped Zn(O,S) nanoparticles (NPs) with different contents of lanthanum have been synthesized with a simple sol-gel method at low temperature (90 degrees C) for 4-nitrophenol (4-NP) detoxification. The as-prepared catalysts were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), photoluminescence (PL) and UV-vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and photoresponsivity. In this work, it is considered that the detoxification of 4-NP to 4-aminophenol (4-AP) without NaBH4 by using photocatalytic method is a green chemical conversion. The experimental data showed 30 ppm toxic 4-NP had been totally converted to useful 4-aminophenol (4-AP) with lower toxicity in 2 h, which was confirmed with a specific peak shift as indicated with UV-vis absorbance spectra and high performance liquid chromatography (HPLC) measurement. The lower amount of evolved hydrogen from photocatalytic process on La-doped Zn(O,S) NPs in the presence of 4-NP confirmed the produced hydrogen was consumed as a reducing agent during the 4-NP-to-4 AP conversion. The photocatalytic detoxification of 4-NP to 4-AP had been demonstrated and an appropriate mechanism based on the experimental data had been proposed and elucidated in this work.