In-situ synthesised polyaniline - halloysite nanoclay composite sorbent for effective decontamination of nitrate from aqueous streams

Abstract

ABSTRACT Nitrate (NO3 −) is one of the most common contaminants of water bodies with harmful effects to aquatic life and human beings. There is a need for development of sorbents for effective removal of NO3 − form aqueous streams. The aim of present study was to develop a Polyaniline modified halloysite nanoclay (PAni-HC) composite sorbent for the uptake of NO3 − from aqueous medium. Aniline coated on halloysite clay was oxidised in acidic medium at 4ºC to synthesise PAni-HC composite in one pot reaction. Successful incorporation of polyaniline (PAni) in the clay matrix was confirmed by different surface characterisation techniques. The as synthesised PAni-HC composite sorbent was tested for NO3 − sorption in a batch mode in the initial concentration range of 5–500 mg L−1. The analysis of NO3 − was performed using ion chromatography in the suppressed conductivity mode. The experimental data were assessed using different kinetic and equilibrium models for understanding the sorption behaviour of the PAni-HC composite. Sorption followed pseudo second order kinetics and intraparticle diffusion model. The maximum Langmuir sorption capacity of PAni-HC composite for NO3 − was found to be 27.9 mg g−1. The composite sorbent when treated with groundwater samples exhibited quantitative removal (> 90%) of NO3 −thus demonstrating the applicability of the sorbent in real situations.