Oxidized Carbon Nanoparticles from Industrial Feedstock for Allura Red AC Dye Removal

Allura Red AC (AR) is a synthetic anionic dye commonly used as a coloring agent in food and beverages. The extensive use and subsequent discharge of this dye as an industrial effluent raises significant health and environmental concerns. In this research, oxidized graphene-like carbon nanoparticles (Ox-CNPs) were evaluated for their potential in adsorption of AR. Characterization confirmed successful oxidation of the base CNPs, with specific surface area increasing from 107.75 to 175.53 m2 g−1 and average particle diameter decreasing from 142 to 96 nm. Batch adsorption tests assessed the influence of initial dye concentration, pH, contact time, and adsorbent dosage on performance. Optimal dye uptake was observed at pH 3.0 with an adsorbent dosage of 5 mg/ 25 ml of a 100 mg L−1 dye solution at 25 0C. Non-linear kinetic modeling showed the process followed the Elovich model, confirming a chemisorption-dominated mechanism, while equilibrium data showed a good fit with the Freundlich isotherm. Zeta potential measurements revealed a net-negative Ox-CNP surface across the tested pH range, indicating hydrogen bonding and π-π interactions, rather than electrostatic attraction, govern the adsorption mechanism. Based on the Langmuir isotherm, the maximum adsorption capacity was calculated to be 104.08 mg g−1. The adsorbent displayed good reusability with 80% retention of the adsorption capacity over three cycles and retained the majority of its performance against real wastewater. This study presents the Ox-CNPs as a promising material to remove harmful synthetic dyes in wastewater remediation.