Adsorption of Acid orange 7 dyes from aqueous solution using Polypyrrole/nanosilica composite: Experimental and modelling

The adsorption of Acid orange 7 (AO7) by Polypyrrole/nanosilica composite (PPN/SiO₂) was studied and various parameters have been investigated, more than 99.4% of the adsorption efficiency was obtained under the optimal conditions (PPN/SiO₂ mass = 1 g/L, contact time = 90 min, Initial AO7 concentration = 10 mg/L, shaking speed = 200 rpm and temperature = 328 K and pH = 3).PPN/SiO₂specifications were determined using FTIR, XRD, TGA, pH_zpc,TEM and SEM analysis. The kinetic data were fitted by the pseudo-second-order kinetic; the rate constant K increased when temperature increased indicating the adsorption was endothermic in nature. The studies related to the adsorption mechanism illuminated that the AO7 adsorption process was complex and obeyed both surface adsorption and particle diffusion. Moreover, based on the results, the adsorption happens through film diffusion at low concentrations while the particle diffusion is the rate-determining step at higher concentration. The isotherm equations showed that the equilibrium data followed more than the Langmuir isotherm with a maximum adsorption capacity of 181.4 mg/g. The thermodynamic parameters were calculated, and their negative value of ΔG° and positive value of ΔS° and ΔH° showed that the adsorption was spontaneous and endothermic.