CoFe₂O₄/graphene oxide/ostrich eggshell/chitosan/polypyrrole nanocomposite for removal 4-nitrophenol

A nanocomposite comprising CoFe₂O₄/graphene oxide/ostrich eggshell/chitosan/polypyrrole (CF/GO/ES/CS/PPY) was fabricated as both an adsorbent and photocatalyst to examine the adsorption and degradation efficiency of the organic pollutant 4-nitrophenol (4-NP), both in the absence of light and under visible light irradiation. The nanocomposite material outperformed adsorption in photocatalytic experiments conducted using the Box-Behnken Design (BBD) within response surface methodology, which investigated the correlation between responses and process variables and identified optimal combinations with Design Expert software. Under optimal conditions, the highest percentage of adsorption and degradation of 4-NP was achieved, with a pH of 5.04, concentration of 4-NP of 24.73 mg/L, nanocomposite mass of 0.04 g, and time of 27.64 min, resulting in reported efficiencies of 89.76, and 99.98% for adsorption and degradation, respectively. Upon statistical analysis, it is clear that the Langmuir isotherm model is the best fit for the studied phenomena, displaying a strong correlation (0.990) and minimal error. The data suggests that the intraparticle diffusion kinetic model has the highest correlation coefficient (0.9925) among the models examined. The value of ΔG° computed for the adsorption process exhibits an increase from 1.3704 to 3.9439 kJ/mol as the temperature rises, indicating the nonspontaneous nature of the adsorption process.