Sonocatalytic rapid degradation of Congo red dye from aqueous solution using magnetic Fe0/polyaniline nanofibers

Raghunath Das; Madhumita Bhaumik; Somnath Giri; Arjun Maity

doi:10.1016/j.ultsonch.2017.02.022

Sonocatalytic rapid degradation of Congo red dye from aqueous solution using magnetic Fe⁰/polyaniline nanofibers

Ultrason Sonochem. 2017 Jul:37:600-613. doi: 10.1016/j.ultsonch.2017.02.022. Epub 2017 Feb 20.

Authors

Raghunath Das¹, Madhumita Bhaumik², Somnath Giri¹, Arjun Maity³

Affiliations

¹ Department of Civil and Chemical Engineering, University of South Africa (UNISA), South Africa.
² Department of Applied Chemistry, University of Johannesburg, Johannesburg, South Africa.
³ Department of Civil and Chemical Engineering, University of South Africa (UNISA), South Africa; DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa. Electronic address: maityarjun@gmail.com.

PMID: 28427673
DOI: 10.1016/j.ultsonch.2017.02.022

Abstract

Nano-sized magnetic Fe⁰/polyaniline (Fe⁰/PANI) nanofibers were used as an effective material for sonocatalytic degradation of organic anionic Congo red (CR) dye. Fe⁰/PANI_, was synthesized via reductive deposition of nano-Fe⁰ onto the PANI nanofibers at room temperature. Prepared catalyst was characterized using HR-TEM, FE-SEM, XRD, FTIR instruments. The efficacy of catalyst in removing CR was assessed colorimetrically using UV-visible spectroscopy under different experimental conditions such as % of Fe⁰ loading into the composite material, solution pH, initial concentration of dye, catalyst dosage, temperature and ultrasonic power. The optimum conditions for sonocatalytic degradation of CR were obtained at catalyst concentrations=500mg.L^-1, concentration of CR=200ppm, solution pH=neutral (7.0), temperature=30°C, % of Fe⁰ loading=30% and 500W ultrasonic power. The experimental results showed that ultrasonic process could remove 98% of Congo red within 30min with higher Q_max value (Q_max=446.4 at 25°C). The rate of degradation of CR dye was much faster in this ultrasonic technique rather than conventional adsorption process. The degradation efficiency declined with the addition of common inorganic salts (NaCl, Na₂CO₃, Na₂SO₄ and Na₃PO₄). The rate of degradation suppressed more with increasing salt concentration. Kinetic and isotherm studies indicated that the degradation of CR provides pseudo-second order rate kinetic and Langmuir isotherm model compared to all other models tested. The excellent high degradation capacity of Fe⁰/PANI under ultrasonic irradiation can be explained on the basis of the formation of active hydroxyl radicals (OH) and subsequently a series of free radical reactions.

Keywords: Active radicals; Congo red; Dye degradation; Nanofibers; Ultra-sonication.