The removal of methyl blue (MB) from industrial wastewater is a critical environmental challenge due to its toxicity and persistence in aquatic ecosystems. Conventional adsorbents such as activated carbon and graphene exhibit high performance but suffer from high cost and complex synthesis processes, limiting their large-scale application. This study presents a novel, low-cost, and highly efficient adsorbent derived from azo-dyes through controlled carbonization under nitrogen atmosphere. The resulting material, termed oxidized-nitrogen rich carbon sheets (NeO-), demonstrates exceptional adsorption capacity for MB, reaching up to 3904 mg g⁻¹ under batch conditions—among the highest reported values for any carbon-based MB adsorbent.
The synthesis involves pyrolysis of Congo red (CR) at varying temperatures (500–900 °C), with optimal performance observed at 700 °C (CR-C-700). Characterization via XPS, FTIR, Raman, BET, and TGA confirms the formation of abundant NeO- functional groups, which are key to the enhanced adsorption mechanism. Unlike traditional adsorbents relying primarily on physisorption or electrostatic interactions, the NeO- groups facilitate strong chemisorption through electron-donor-acceptor (EDA) interactions with MB. This synergy is further supported by hydrophobic-hydrophobic interactions, especially effective at pH 5.5 where MB exists as a zwitterion, enabling close contact between the dye and the carbon surface.
Batch adsorption studies reveal rapid kinetics, with over 65% removal within 5 minutes, and equilibrium reached within 30 minutes.31362-50-2 Molecular Weight The adsorption data fit best with the Sips isotherm model (R² = 0.539-86-6 custom synthesis 99995), indicating heterogeneous monolayer adsorption with high affinity.PMID:29494101 The Langmuir maximum capacity (qm = 4023.6 mg g⁻¹) closely matches experimental results, validating the effectiveness of NeO- sites. Notably, despite having a low BET surface area (7.62 m²/g), CR-C-700 outperforms materials with much higher surface areas, proving that chemical functionality dominates over physical surface area in this system.
The material also performs exceptionally under continuous-flow conditions. When coated onto filter paper and used in a peristaltic filtration system, CR-C-700 removes ~85% of MB compared to only ~23% by plain filter paper. This demonstrates its practical applicability in real-world water treatment systems. Furthermore, the adsorbent exhibits excellent recyclability: after desorption via calcination at 700 °C under N₂, the regenerated material (r-CR-C-700) retains full activity after three cycles, confirming structural stability and reusability.
This work highlights the transformative potential of azo-dyes—not just as pollutants but as valuable precursors for sustainable, high-performance adsorbents. The presence of the N=N moiety in azo dyes is essential for forming NeO- during carbonization, explaining why other dyes like methyl blue fail to generate similar functional groups. In conclusion, NeO- rich carbon sheets represent a breakthrough in low-cost, efficient, and reusable adsorbents for dye wastewater remediation, offering a scalable solution for industrial and environmental applications.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
