Ecologically viable carbon nano-onions for the efficient removal of methyl orange azo dye and its environmental assessment†

The rapid development of industrialization led to a significant rise in the volume of dyes discharged into the environment which are toxic and harmful to the ecosystem. Green modification is considered the most effective and environmentally beneficial approach for producing eco-friendly materials due to its non-adverse effects on the biosphere. In this regard, we synthesized sustainable and cost-effective carbon nano-onions (CNOs) and examined their utility in adsorbing methyl orange dye. CNOs demonstrated adsorptive removal of methyl orange dye within 30 minutes at room temperature with an outstanding efficiency of 99.99%. The kinetic regression and isotherm results confirmed that adsorption of methyl orange dye follows pseudo-second-order kinetics and Langmuir isotherm models. Furthermore, CNOs exhibited effective removal efficiency for methyl orange dye in real water samples, similar to their performance in deionized water, with rates of 99.20%, 98.88%, and 97.22% for tap water, lake water, and dam water, respectively. The hydrophobic nature of CNOs renders them highly suitable for recyclable applications in the removal of methyl orange dye from wastewater, exhibiting effectiveness for up to seven cycles. Significantly, treated wastewater has been examined for the growth of barley plants. As a result, maximum growth of barley plants was found in treated wastewater, while in water polluted by methyl orange dye they showed retarded growth. The above results highlighted the virtuous development prospects of biomass-derived CNOs in wastewater remediation and further practical uses of treated water.