An overview on cellulose-supported semiconductor photocatalysts for water purification

Abstract

Metal oxides have been widely used in wastewater treatment, but due to their limitations there is a need of some modifications to make them an efficient photocatalyst. Many support materials are used to enhance the photocatalytic efficacy of many photocatalysts. Recently, cellulose nanomaterials have been utilized as green prototype for the preparation of metal or metal oxide nanomaterials and to improve their photocatalytic efficacy as it acts as a good adsorbent and support material. Cellulose fibers (macro and nano) have gathered the interest of scientific community due to its easy fabrication and some unique possessions. Through immobilization, photocatalysts can be used for the removal of pollutants by fixing the raw catalyst powder onto a support material. Physical adsorption and covalent binding on carrier substance are various strategies for immobilization. In composites, cellulose fibers (macro and nano) have been utilized as a driving force owing to its structural properties (presence of functional groups, i.e., carboxylic, hydroxyl, methoxy and phenolic groups) and hydrophilic nature which helps in increasing surface roughness in composites. The present review offers an outlook on metal oxides, their limitations, immobilization and support materials where cellulose performed as support (to enhance surface area), adsorbent, immobilized and functionalized material to minimize the limitation of metal oxides. The main focus of this review is on different role of cellulose materials which describes the fundamental properties of cellulose and its amendments by coupling with other metal oxides such as TiO2, ZnO, Ag and phosphates.