Malays. J. Anal. Sci. Volume 30 Number 3 (2026): 1851

 

Research Article

 

Catalytic reduction of 4-nitrophenols using heterostructure gold nanoparticles on imine-bearing di-tert-butyl substituted functionalized magnetite

 

Syaharil Saidin1, Siti Kamilah Che Soh1*, Wan M. Khairul1, Ku Mohd Kalkausar Ku Yusof1, Juan Matmin2, and Mohamad Azmirrudin Ahmad3

 

1Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia

2Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Johor Bahru, Malaysia

3Industrial Centre of Innovation in Bio-Medical, Lot 34, Jalan Hi-Tech 2/3, Kulim Hi-Tech Park, 09000 Kulim, Kedah, Malaysia

 

*Corresponding author: sitikamilah@umt.edu.my

 

Received: 1 March 2026; Revised: 29 April 2026; Accepted: 10 May 2026; Published: 30 June 2026

 

Abstract

Nonbiodegradable aromatic pollution, such as 4-nitrophenol (4-NP), is known for its adverse effects on human health and aquatic reservoirs. As a result, it has now become increasingly significant among environmental concerns due to its toxicity and persistence. 4-NP is a common organic pollutant found in industrial effluents originating from dye, pesticide, and pharmaceutical manufacturing. Due to its extensive presence, the chemical reduction of 4-NP is a promising strategy and an essential model reaction for compound conversion to the less toxic and biodegradable 4-aminophenol (4-AP). In this study, a heterogeneous catalyst composed of gold nanoparticles (AuNPs) supported on imine-bearing di-tert-butyl-substituted functionalized magnetite was designed, synthesized, and evaluated for catalytic reduction activity. The introduction of imine functionalization, incorporating sterically bulky di-tert-butyl groups, successfully provided a stable anchoring platform for uniform dispersion of AuNPs, which significantly enhances electron transfer and catalytic performance through improved metal-support interactions. Unlike conventional Au@Fe3O4 systems that rely on bare magnetite or amine-only supports, the imine-bearing, di-tert-butyl-functionalized magnetite provides simultaneous steric protection against AuNP aggregation and enhanced metal-support interaction, thereby yielding superior catalytic stability and recyclability. Meanwhile, the magnetic properties of bare magnetite (Fe3O4) allow for facile recovery and reuse of the catalyst, addressing sustainability and economic concerns in wastewater remediation. The obtained supported catalyst was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometry (VSM), and thermogravimetric analysis (TGA). The catalytic performance was evaluated under varying catalyst loadings (5-50 mg), and the samples demonstrated rapid and complete reduction of 4-NP within 4 minutes in the presence of NaBH4 as a reducing agent. The tunable color of the yellow solution (4-NP) to colorless (4-AP) indicates the effectiveness of the catalyst. In particular, the synthesized supported catalyst exhibited excellent performance and reusability, with a high retention of 92.18% efficiency after nine consecutive cycles, offering significant economic advantages.

 

Keywords: 4-nitrophenol reduction, gold nanoparticles, imine-functionalized magnetite, heterogeneous catalysis, magnetic nanocatalysts

 

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