minerals Article Synthesis and Application of FeCu Bimetallic Nanoparticles in Coal Mine Wastewater Treatment Nkosinathi Goodman Dlamini 1, * , Albertus Kotze Basson 1 and Viswanadha Srirama Rajasekhar Pullabhotla 2, *   Citation: Dlamini, N.G.; Basson, A.K.; Pullabhotla, V.S.R. Synthesis and Application of FeCu Bimetallic Nanoparticles in Coal Mine Wastewater Treatment. Minerals 2021, 11, 132. https://doi.org/10.3390/ min11020132 Received: 16 December 2020 Accepted: 20 January 2021 Published: 28 January 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Biochemistry and Microbiology, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, South Africa; BassonA@unizulu.ac.za 2 Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, South Africa * Correspondence: nathidlamini03@gmail.com (N.G.D.); PullabhotlaV@unizulu.ac.za (V.S.R.P.); Tel.: +27-35-902-6155 (V.S.R.P.) Abstract: Wastewater treatment has become a global challenge with wastewater treatment cost fast increasing. Industrial processes such as downstream processes, wastewater treatment, and several fermentation processes depend largely on the use of flocculants. Synthetic flocculants, which are conventionally used in wastewater treatment, are hazardous to the environment and are carcinogenic to human health. Therefore, bioflocculants can be used as an alternative due to their biodegradable and environmentally friendly nature. However, low efficacy hinders their industrial application. This necessitates the need for a new technology to combat wastewater treatment challenges. Nanotechnology provides the platform to explore the possible solutions to these problems. The combination of two different metals results in the formation of bimetallic nanoparticles (BNPs). Due to better properties, bimetallic nanoparticles have attracted huge attention as compared to monometallic nanoparticles from both technological and scientific views. Iron copper bimetallic nanoparticles (FeCu BNPs) were successfully stabilized by bioflocculant and used in the coal mine wastewater treatment. Infrared spectrometric analysis showed the presence of carboxyl (COO−), hydroxyl (−OH), and amino (−NH 2 ) functional groups. SEM images showed irregular and crystalline like morphology. Meanwhile, TEM analysis revealed chain like agglomerated nanoparticles. FeCu BNPs exhibited a wide pH stability range from 3, 7, and 11 with 99% flocculation activity at pH 7 and at lowest dosage of 0.2 mg/mL. After treating wastewater, the FeCu BNPs could remove pollutants such as phosphate, sulfate, calcium, chemical oxygen demand (COD), and biological oxygen demand (BOD) with phosphate having the highest removal efficacy of 99%. Keywords: bimetallic nanoparticles; flocculation; pollutants; removal efficiency; wastewater 1. Introduction The most common sources of environmental pollutants among others is waste dis- charge and industrial effluents. Generally, where coal mine activities are common, large amounts of wastewater are generated during coal processing resulting in water resource pollution. A vast number sulfide mineral such as pyrite ore (FeS 2 ) is exposed to water, air and microbes during mining and generate acid mine drainage (AMD) [1] and other pollutants such sulfur, phosphate, COD, and BOD [2]. Any water contaminated by organic pollutants, industrial effluent, bacteria, and microorganisms or any compound that deterio- rate its initial quality is defined as wastewater and can be subdivided into domestic and industrial [1]. Chemical flocculants have been used extensively in pollutants removal in wastewater. This is due to their effectiveness at low dosages, long shelf life, and low cost [3]. Even though the chemical flocculants exhibit all these remarkable capabilities, in some developed countries these flocculants were banned due to the detrimental effect they possess to human, animals, and the environment [4]. The chemical flocculant shortcomings among others, include non-degradability and toxicity [5]. Recently, most emphasis is given to naturally Minerals 2021, 11, 132. https://doi.org/10.3390/min11020132 https://www.mdpi.com/journal/minerals