The present paper reports the photocatalytic efficiency of Mn-S-co-doped TiO2 under visible light for phasing out the organic pollutants from environmental matrix. The as-synthesized photocatalyst was prepared by ecofriendly method using ultrasonic irradiation in shorter time. The incorporation of dopant Mn2+ onto the S-TiO2 lattice was confirmed from XRD, EDS and EPR technique. The crystallite size of the Mn-S-co-doped TiO2 calcinated at 450, 550 and 750 degrees C was found to be 56.4, 25.43 and 46.45 nm respectively. Co-doping led to the lowering of the band gap of TiO2 to 2.4 eV. The photo catalytic efficiency of the synthesized catalyst was investigated and maximum degradation was observed with MnST-550 under wavelength region of 490 nm for quinalphos (98.0%) at pH 7. The intermediates formed during the photocatalytic reaction were identified by using analytical techniques such as GC-MS. Seven possible intermediates were identified and the formation of initial intermediates involved photooxidation of P=S to P=O (quinalphos-oxon), attack by hydroxyl group on quinoxaline ring and dealkylation of the phosphate moiety. The complete degradation of quinalphos has been obtained in 24 h, as no peaks have been observed in a gas chromatogram and the mechanism of the photocatalytic degradation was proposed. (C) 2017 Elsevier B.V. All rights reserved.