Self-Nitrogen-Doped Nanoporous Carbons Derived from Poly(1,5-diaminonaphthalene) for the Removal of Toxic Dye Pollutants from Wastewater: Non-Linear Isotherm and Kinetic Analysis

The high surface area and porosity of self-nitrogen-doped porous carbons (SNPCs) nominates them for potential application in water treatment due to their high efficiency towards the removal of various pollutants. In this study, SNPCs were fabricated from poly(1,5-diaminonaphthalene) (P(1,5-DANPh) by single and simultaneous carbonization at the activation step at different temperatures (600, 700, and 800 °C). The carbonization’s temperature plays a vital role in controlling the nitrogen-doping, surface area, porosity, and morphology of SNPCs. The SNPCs-7 sample prepared at 700 °C showed the highest surface area (1678.8 m(2) g(−1)) with pore volume (0.943 cm(3) g(−1)) with a micro/meso porous structure. The prepared SNPCs were used as an effective adsorbent for removal of crystal violet dye (CV) from contaminated water. SNPCs-7 showed the highest adsorption of 487.53 mg g(−1) and the adsorption capacity of the SNPCs samples follows the order SNPCs-7 > SNPCs-8 > SNPCs-6, which is consistent with the results of their surface area and porosity. The adsorption for CV dye followed Freundlich isotherm models and a pseudo second order kinetic model. The negative values of Gipps free energy (ΔG°) and positive value of enthalpy (ΔH°) indicated that the adsorption of CV dye onto the surface of SNPCs was a spontaneous and endothermic process, respectively. Based on the results, the adsorption mechanism of CV dye onto the surface of SNPCs was proposed.