Highly Active Ag-Cu Nanocrystal Catalyst-Coated Brewer’s Spent Grain Biochar for the Mineralization of Methyl Orange and Methylene Blue Dye Mixture

Abstract

The aim of the present work is to valorise the brewing industry’s waste, i.e., brewer’s spent grain (BSG), into functional biocarbon for environmental catalysis applications. In this context, cost-effective and environmentally friendly biochar support coated with in-situ-generated Ag-Cu nanocrystals, was developed via the wet impregnation of BSG biomass powder with copper (II) nitrate trihydrate and silver nitrate aqueous solution prior to pyrolysis at moderate temperature (500 °C). Small-size homogenously distributed Ag-Cu nanocrystals (≤80 nm) on the surface of the biochar (Biochar@Ag-Cu) were observed by field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Elemental compositions were determined by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX). The crystalline nature of the nanoparticles was confirmed by X-ray powder diffraction (XRD). Information about the thermal stability of the materials and quality were obtained by thermogravimetric analysis (TGA) and Raman, respectively. The potentiality of the Biochar@Ag-Cu catalyst in the field of pollutant removal is demonstrated by taking methyl orange and methylene blue as model dyes. A kinetics study was performed and analyzed by UV–vis spectroscopy. Its highly active catalytic nature is proved by the complete mineralization of the methyl orange dye (100%) through oxidative degradation. The reusability of the catalyst has shown 96% removal efficiency after 3 cycles. The linear plot of −Ln (CA/C0) vs time (R2 = 0.9892) reveals that the mineralization of the methyl orange dye follows pseudo-first-order kinetics (k = 0.603 × 10−2 min−1). A methyl orange + methylene blue dye mixture degradation study has revealed the faster kinetics of the present catalyst towards methylene blue degradation. The current study suggests that BSG Biochar@Ag-Cu can be a potential candidate in contribution towards SDG 6.

Surface Treatment of Biochar: Methods, Surface Analysis and Potential Applications. A Comprehensive Review

“…We thus expect even more publications on the topic and the valorization of numerous other wastes. There are already, and there will be new regional niches from North to South to valorize biomasses such as Douglas fir, 81 brewer spent grain, 95 sugarcane bagasse, 68 olive 96,97 and date 98 stones, durian, 82 …. However, more rationality is needed to select which agrowaste is worth the thermochemical transformation into biochar, by determining the initial cellulose-hemicellulose-lignin composition as their thermochemical transformation yields biochars with completely different properties and thus different potential applications, for example as electrode materials.…”

Carbon Dioxide Methanation Enabled by Biochar-Nanocatalyst Composite Materials: A Mini-Review

“…Given the skyrocketing number of publications on biochar (about 5000-6000 publications yearly since 2021), it is clear that this support obtained by thermochemical treatment of the biomass, mostly lignocellulosic waste, has much to offer; this is what has attracted our attention. In the past two years, we have spent time and effort on the design of biochar nanocatalysts from various lignocellulosic wastes for the degradation of dyes [18][19][20][21] and the elimination of other emerging pollutants. Apart from de-pollution, and investigating green and valuable methods to design biochar-based materials for the energy sector, we decided to invest time in the attractive and challenging process of CO 2 methanation.…”