Waste bulrush transformed into copper-enhanced material for dye removal from wastewater
Industrial activities such as textile manufacturing, paper production, leather processing and food processing can generate wastewater containing synthetic dyes. Because many synthetic dyes are chemically stable, difficult to biodegrade and environmentally persistent, their release into waterways can pose risks to aquatic ecosystems and human health.
Researchers at Doshisha University in Japan have developed a novel method to transform agricultural waste, specifically bullrush, into a copper-enhanced activated carbon material capable of removing synthetic dyes from wastewater. Conventional treatment methods for removing these dyes from wastewater are expensive, energy-intensive, and may produce secondary waste products, making them less than ideal for large-scale applications.
To address this, the team turned to bullrush agricultural waste as an affordable and renewable carbon source, and copper precursors to create a unique composite material. By using a single-step co-pyrolysis process, the researchers introduced zero-valent copper nanoparticles (Cu0) into the mesoporous structure of the bullrush biomass.
This was achieved through the use of copper(II) nitrate trihydrate and potassium hydroxide (KOH) as the copper precursors, combined with the biomass' own volatile reducing gases (CO and H2) during pyrolysis. The resulting material, dubbed ZVCu@BAC (zero-valent copper nanoparticle-enhanced bullrush activated carbon), exhibited a high surface area of 984.5 m2/g, a total pore volume of 0.615 cm³/g, and needle-like Cu0 structures uniformly dispersed throughout the carbon matrix.
This composite was found to have an amphoteric interface, making it effective in removing both cationic and anionic dyes. In tests using methylene blue (a cationic dye) and methyl orange and sunset yellow (both anionic dyes), the ZVCu@BAC composite achieved removal efficiencies of 62.31 mg/g, 56.37 mg/g, and 35.76 mg/g, respectively.
The Langmuir isotherm and pseudo-second-order kinetics best described the adsorption process, indicating that chemisorption played a significant role in removing the dyes. The adsorption process was also found to be spontaneous and exothermic, with multiple mechanisms contributing to the removal process, including electrostatic attraction, π-π stacking, pore filling, and coordinate bonding with the metallic Cu0 sites.
After six regeneration cycles using a KOH/acetone eluent, the composite retained 90.6% MB removal efficiency and 88.0% MO removal efficiency. With an estimated production cost of about ¥1,800 per kilogram, the researchers believe that this bullrush-derived ZVCu@BAC composite could provide a cost-effective, sustainable, and scalable solution for treating industrial wastewater containing synthetic dyes.
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