Abstract
Dye sludge is a major by-product and it will bring critical environmental problems in the textile industry. In this study, dicyandiamide formaldehyde resin (DFR) is used as an effective flocculating agent for the removal of anionic dyes from textile dye wastewater. Employing dye-contaminated sewage sludges as precursors, N, S dual-doped carbon materials are successfully synthesized by using DFR as a soft template. The specific surface area, morphology, and pore structure of the resulting annealed products can be easily controlled by changing the DFR content of the dye sludge. The oxygen reduction reaction performance of optimal carbon material (N, S-DF-2) is close to commercial 20% Pt/C in alkaline medium, including onset potential (0.98 V), half-wave potential (0.82 V), as well as limiting current density (5.46 mA·cm−2). Furthermore, it also shows better durability and crossover resistance. In addition, N, S-DF-2 exhibits a large specific capacitance (230 F·g−1 at 1 A·g−1) and super capacitance retention (nearly 98% at 10 A·g−1) after 2500 cycles as supercapacitors electrodes. This work opens up a new method to take full advantage of organic polymeric flocculant as a soft template to prepare N, S dual-doped carbon materials, which will be beneficial for the reuse and recycling of sewage sludge, as well as for the production of good quality energy conversion and storage materials.
Highlights
It is estimated that over 8 × 105 tons of commercial dyes and pigments are applied in the textile industry annually [1,2]
We explored the effect of the dicyandiamide formaldehyde resin (DFR) flocculant dosage on dye HK2BP, various dosages (4–28 mg·L−1) were exposed to a fixed dye concentration (100 mg·L−1) at pH 8.0
A low flocculant dosage with simultaneously high dye removal efficiency is desirable for industrial dye wastewater treatment
Summary
It is estimated that over 8 × 105 tons of commercial dyes and pigments are applied in the textile industry annually [1,2]. 10%–15% of azo dyes do not bind to the textile fibers in the dyeing process and are released into the environment in the dyeing process [3,4]. Azo dyes are soluble in water leading to an undesirable color, eventually causing major damage to the aquatic environment due to their high resistance to natural degradation. Several treatment technologies, such as adsorption, chemical oxidation, photo degradation, and even biological degradation, have been used to treat high-concentration dye wastewater extensively. The two methods only convert azo dye wastewater into huge solid wastes, which raises issues and challenges for further disposal of these hazardous sewage sludge (SS). Transforming environmental wastes to utilizable energy materials is a promising strategy for economic sustainable development considering that it concerns environment and energy aspects [5,6]
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