(371q) Degradation of Reactive Black 5 Dye Using Nanostructured Carbon Adsorbents

Hazardous effluents from global textile industries contain several hundred thousand tons of synthetic dyes per year [1]. A standard azo dye known as reactive black 5 (RB5) provides color for a substantial range of materials in the textile industry; however, water contamination from RB5 can lead to harmful impacts on local ecosystems and human health [1]. The structure of RB5 is inherently stable due to its aromatic and heterocyclic characteristics, rendering it non-biodegradable and mutagenic [2]. As a result, it is necessary for textile industries to employ waste treatment techniques in an effort to remove harmful dyes before they can pollute the environment.

A variety of techniques, such as flocculation and biological degradation methods, have been utilized in the past to facilitate the separation of azo dyes from wastewater. However, these strategies are characterized by major drawbacks, including costly reagents and lengthy removal processes [3]. The aim of the current research is to develop a practical dye removal method for the treatment of RB5-contaminated water. Nanostructured carbon, including activated carbon (AC), graphene nanoplatelets (GNP) and graphene oxide (GO), was investigated as adsorbents for RB5. These materials have been known to exhibit high surface area, stability in aqueous environments and potential for recyclability [2,4,5].

During the course of the experiments, a constant quantity of each studied adsorbent (AC, GNP or GO) was employed and the RB5 degradation capability was tested for 2 hours in RB5 aqueous solutions with concentrations ranging from 10^-4 to 10^-5 moles/liter (M) under ultraviolet radiation (365 nm). A TECAN microplate reader was utilized as adsorption spectrophotometer. Representative spectra are shown in Figure 1 for AC at an RB5 concentration of 10^-4 M. The maximum adsorption peak for RB5 was found to occur at approximately 600 nm and is due to the existence of the nitrogen-nitrogen double ‘azo’ bond dissociated by the degradation agent [3]. Over the course of two hours, it was observed that the intensity of this peak decreased in the case of all studied adsorbents. Utilizing the value of the decreasing peak over time, it was possible to calculate the remaining RB5 concentration at the end of each experiment, using the calibration curve generated from the pure RB5 concentrations that were studied.

In addition to UV radiation, adsorbents were tested under visible light condition and dark conditions. Finally, equilibrium data of RB5 adsorption on AC, GNP and GO were obtained by carrying out degradation experiments over a 24-hour period, which was deemed to be adequate for the attainment of equilibrium [6]. The results were fitted to the Langmuir and Freundlich isotherm models to evaluate their efficacies. Activated carbon was found to have the highest RB5 degradation capability among the nanostructured carbon adsorbents that were investigated. The results are analyzed and discussed in order to demonstrate the most practical RB5 degradation catalyst that could be employed for RB5 removal in the textile industry.

References:

[1] Bilal, Muhammad, et al. “Toxicological Assessment and UV/TIO2-Based Induced Degradation Profile of Reactive Black 5 Dye.” Environmental Management, vol. 61, no. 1, 2017, pp. 171–180., https://doi.org/10.1007/s00267-017-0948-7.

[2] Fraga, Tiago José, et al. “Comparative Approach towards the Adsorption of Reactive Black 5 and Methylene Blue by N-Layer Graphene Oxide and Its Amino-Functionalized Derivative.” Adsorption, vol. 26, no. 2, 2019, pp. 283–301., https://doi.org/10.1007/s10450-019-00156-9.

[3] Ben Mbarek, W., et al. “Rapid Degradation of Azo-Dye Using MN–Al Powders Produced by Ball-Milling.” RSC Advances, vol. 7, no. 21, 2017, pp. 12620–12628., https://doi.org/10.1039/c6ra28578c.

[4] Karadag, Dogan, et al. “Adsorption Equilibrium and Kinetics of Reactive Black 5 and Reactive Red 239 in Aqueous Solution onto Surfactant-Modified Zeolite.” Journal of Chemical & Engineering Data, vol. 52, no. 5, 2007, pp. 1615–1620., https://doi.org/10.1021/je7000057.

[5] Kotal, Moumita, et al. “Graphene-Templated Cobalt Nanoparticle Embedded Nitrogen-Doped Carbon Nanotubes for Efficient Visible-Light Photocatalysis.” Crystal Growth & Design, vol. 20, no. 7, 2020, pp. 4627–4639., https://doi.org/10.1021/acs.cgd.0c00430.

[6] Mengelizadeh, Nezamaddin and Pourzamani, Hamidreza, “Adsorption of Reactive Black 5 Dye from Aqueous Solutions by Carbon Nanotubes and its Electrochemical Regeneration Process”, Health Scope, vol. 9, no 4, 2020, e102443, doi: 10.5812/jhealthscope.102443.