Improved photocatalytic activity of CdSe-nanocomposites: Effect of Montmorillonite support towards efficient removal of Indigo Carmine Rajeev C. Chikate ⇑ , Brijesh S. Kadu ⇑ Nanoscience Group, Department of Chemistry, Post-graduate and Research Centre, MES Abasaheb Garware College, Karve Road, Pune 411004, India highlights  Highly dispersed CdSe nanoparticles in Montmorillonite clay.  Kinetics and adsorption behavior of IC on CdSe-MMT nanocomposites.  Spontaneous, exothermic and chemisorptive mineralization of IC.  Pseudo-multilayer boundary diffusion controlled adsorption process. graphical abstract article info Article history: Received 8 August 2013 Received in revised form 8 November 2013 Accepted 23 December 2013 Available online 4 January 2014 Keywords: CdSe nanocomposites Indigo Carmine Photocatalysis Adsorption isotherms Intra-particle diffusion abstract To ascertain the contribution of adsorptive capacity of Montmorillonite (MMT) towards photocatalytic process, CdSe-MMT nanocomposites are explored for adsorptive removal of Indigo Carmine (IC). The nanocomposites are prepared via two approaches: (a) in-situ formation and (b) wet impregnation of CdSe onto MMT support. XRD analysis of composites suggested the proper dispersion of CdSe nanoparticles in MMT clay matrix with spherical morphology of 5–10 nm sized CdSe nanoparticles. These nanocompos- ites are employed for photocatalytic degradation of IC under visible light at various IC concentrations and different amount of catalyst. Kinetics of IC is found to be of pseudo-second order with 10% in-situ and 50% loaded nanocomposites exhibiting better photocatalytic activity at 1.0 g L 1 catalyst and 100 mg L 1 of IC. Dynamics of its adsorptive removal on the composite surface evaluated by employing error estimation tools clearly suggest that Redlich–Peterson and Flory–Huggins adsorption isotherms effectively describe the multi-layer process. It is observed that spontaneous, exothermic chemisorption process occurring on the surface indeed enhances photocatalytic activity. Moreover, such a feature is also found to be associated with diffusion of IC within mesoporous structure of MMT that subsequently favors pore-diffusion controlled adsorption process. IR spectral analysis demonstrated that IC molecule is degraded on the catalyst surface. Light or oxygenated species induced photocorrosion of CdSe is suppressed due to its composite formation with MMT that results in 620 ppm removal of IC during successive cycles; a feature ascribed as improved photocatalytic activity for CdSe nanoparticles. Ó 2014 Elsevier B.V. All rights reserved. Introduction Synthetic dyes emanated by textile, leather and printing industries causing contamination in water resources is a serious environmental concern [1]. Currently, many methods are employed to remove dyes from polluted water, that include sedimentation, coagulation, flocculation, chemical treatments, oxidation, electrochemical methodology, photodecomposition, biological treatments, adsorption, and membrane process [2]. Among these, photocatalysis involving semiconductor nanoparti- cles under visible light have been extensively studied as it is con- sidered to be a cleaner and greener, lesser photo-corrosive and 1386-1425/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.12.099 ⇑ Corresponding authors. Tel.: +91 20 41038263; fax: +91 20 25438165. E-mail addresses: rajuchikate29@gmail.com (R.C. Chikate), brijesh_kadu@ yahoo.co.in (B.S. Kadu). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 124 (2014) 138–147 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa