A review on polyaniline-based materials applications in heavy metals removal and catalytic processes

•Adsorptive features of polyaniline as a scalable and stable conductive polymer.•Catalytic features of polyaniline as an environmentally friendly polymer.•Polyaniline-based materials including composites in micro and nanoscale.•Polyaniline-based composites with natural or synthetic materials.•Polyaniline as a support or protective shell for hosting catalytic active components. Adsorption and catalytic applications of polyaniline-based materials have witnessed an increasing rate in recent years. Polyaniline (PAn), an important member of conductive polymers, is known for its high conductivity, simple preparation, and reasonable stability. In terms of adsorption perspective, novel PAn-based polymeric composites and nanocomposites have been developed to address the issue of growing scale of water contamination by different mono- and multivalent heavy metal ions in recent years. Owing to its distinct features such as ease of production and biocompatibility, PAn can be combined with a wide range of organic/inorganic, natural or synthetic materials to procure novel sorbents with higher removal efficiency and improved sorption properties for heavy metal ions. Applications of PAn-based materials for removal of other pollutants from aqueous media are briefly presented as well. Having said that PAn is a stable material, PAn-derived materials have also exhibitied good recyclability which is a crucial feature in the adsorption process. In terms of catalysis perspective, PAn can also be counted as a catalytic species or as a material for holding or protecting precious catalytic components. Either acting as a protective material or as a catalytic component, PAn has proven its capability as a proper platform for heterogenizing the catalyst of many catalytic reactions. Herein, a concise review of both adsorptive and catalytic behavior of new materials derived from polyaniline is presented. The attention was directed to the preparation protocles of PAn-derived materials along with the role of PAn in the related applications. Furthermore, other potential applications of PAn-based materials are also briefly summarized.