Review A review on novel composites of MWCNTs mediated semiconducting materials as photocatalysts in water treatment Kranthi Kumar Gangu, Suresh Maddila, Sreekantha B. Jonnalagadda ⁎ School of Chemistry & Physics, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa HIGHLIGHTS • Review on MWCNTs/semiconductor composites as superior photocatalysts • MWCNTs acted as good electron reser- voirs and substrate adsorbents in the composites. • MWCNTs retard recombination of photogenerated electron-hole pairs in composites. • Higher MWCNTs composition impacts the photocatalytic activity of compos- ites. • Photocatalytic mechanisms in the gen- eration of reactive oxygen species GRAPHICAL ABSTRACT abstract article info Article history: Received 23 May 2018 Received in revised form 11 July 2018 Accepted 26 July 2018 Available online 27 July 2018 Editor: Paola Verlicchi Many technologies were explored to eliminate the harmful pollutants entering water systems and to minimize their impact on environment. In general, photo-catalysis is one of the sustainable techniques with wider applica- tions and semiconductors in particular were efficiently utilized in the photocatalytic degradation of pollutants. Semiconducting materials, such as TiO 2 , ZnO, BiO, CdS, and Ag 3 PO 4 are frequently used as photo-catalysts due to their suggestible band gap and structural properties. The generation of reactive oxygen species such as hy- droxyl and superoxide radicals is the crucial factor in degradation of pollutant molecules. The rapid recombina- tion of photo-generated electron-hole pairs impacts on the efficacy of semiconductors as photo-catalysts. The integration of properties of multi-walled carbon nanotubes (MWCNTs) with semiconductors is considered as im- perative alternative strategy to boast the photocatalytic efficiency. The combinative merits of composites of MWCNTs and various semiconductor materials give new vista for water treatment and environmental protec- tion. This review describes the scope of different types of MWCNT and semiconductor composites as photo- catalysts and their structure-property relationships in oxidative degradation and mineralization of organic pol- lutants, in particular. © 2018 Elsevier B.V. All rights reserved. Keywords: Semiconductor-MWCNTs Nanocomposites Photocatalysis Reactive oxygen species Synergistic effect Environmental protection Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1399 1.1. Synthesis of composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1400 Science of the Total Environment 646 (2019) 1398–1412 ⁎ Corresponding author at: School of Chemistry & Physics, University of KwaZulu-Natal, Durban 4000, South Africa. E-mail address: jonnalagaddas@ukzn.ac.za (S.B. Jonnalagadda). https://doi.org/10.1016/j.scitotenv.2018.07.375 0048-9697/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv