Abstract
Green synthesis of core–shell nanoparticles is gaining importance nowadays as it is viewed as being environmental friendly and cost effective. The present study aimed to synthesize iron@copper core–shell nanoparticles using a polysaccharide-based bioflocculant from Alcalegenis faecalis and to evaluate its efficiency in dye removal and river water and domestic wastewater treatment. The synthesized samples were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, transmission electron microscopy, and UV-Vis spectroscopy analysis. To optimize the best concentration for core–shell formation, different ratios of iron to copper were prepared. Sample 1 (S1) contained 1:3 iron to copper (Fe 25%–Cu 75%), sample 2 (S2) contained 1:1 iron to copper (Fe 50%–Cu 50%), and the third sample (S3) contained 3:1 iron to copper (Fe 75%–Cu 25%). The flocculation activity (FA) was above 98% at 0.2 mg/mL for all the samples and the samples flocculated well under acidic, alkaline, and neutral pH conditions. Sample 3 was shown to be thermostable, with flocculation activity above 90%, and samples 2 and 1 were also thermostable, but the flocculation decreased to 87 at 100 °C. All three samples revealed some remarkable properties for staining dye removal as the removal efficiency was above 89% for all dyes tested. The synthesized core–shell nanoparticles could remove nutrients such as total nitrogen and phosphate in both domestic wastewater and Mzingazi river water. Furthermore, high removal efficiency for chemical oxygen demand (COD) and biological oxygen demand (BOD) was also observed.
Highlights
Drinking water scarcity, i.e., water free of pathogens and toxic chemical substances, is a worldwide problem due to population growth, extended droughts, competing demands from different users, and more health-based regulations
The limitations of bioflocculants are their high production cost and low flocculation efficiency as compared to their counterpart synthetic flocculants; some of the bioflocculants require cations to work effectively. These findings suggest that the synthesized iron@copper core–shell nanoparticles could be cost-effective as their flocculation activity was found to be above 95% in the absence of cations
The synthesis of core–shell nanoparticles was achieved using the description by Yu et al [16], where 10 mL of 0.02 M FeCl3 aqueous solution was prepared in a flask, after which 0.5 g of bioflocculant was added
Summary
I.e., water free of pathogens and toxic chemical substances, is a worldwide problem due to population growth, extended droughts, competing demands from different users, and more health-based regulations. Chemical flocculants are widely used nowadays owing to their low-cost, effective flocculation performance. Their application has been found to cause environmental and health hazards such as Alzheimer’s disease [2]. Use of bioflocculants has gained interest in recent years due to the biodegradability properties bioflocculants possess and their negligible environmental hazards. Higher production costs and low flocculation yields are limitations to the industrial application of bioflocculants [3]. In recent years research has mainly focused on the synthesis of nanoparticles from bioflocculants and their application in industrial effluents and Catalysts 2020, 10, 755; doi:10.3390/catal10070755 www.mdpi.com/journal/catalysts
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