Valorization of sewage sludge for methylene blue removal from aqueous solution

In this research, we look into the use of dried sewage sludge biomass in its crude form generated from a municipal wastewater treatment plant localized in Mascara (West of Algeria) when it comes to the elimination of methylene blue (MB) from artificial wastewater aqueous solutions in batch process. Moreover, the sewage sludge biomass was characterized by different techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and thermal gravimetric analysis (TGA). In order to optimize the removal of methylene blue (MB) by the present adsorbent, various parameters were explored, including pH effect, initial methylene blue (MB) concentration, adsorbent dose, temperature, and contact time.The results revealed the presence of abundant functional groups (–COOH) responsible for methylene blue (MB) adsorption by electrostatic attraction, optimal pH = 5, and optimal sewage sludge biomass concentration of 2 g/l. The maximum measured adsorption capacity of methylene blue on the sewage sludge biomass was about qe = 325 mg/g at 20 min of contact time. Based on the R2, X2, RMSE, Average relative error (ARE) coefficients, the pseudo-second-order kinetic model and Langmuir model describe well the experimental kinetic and equilibrium data. The application of the Weber and Morris model to the kinetic data shows that the overall mass transfer rate was controlled simultaneously by film diffusion and intraparticle or pore diffusion. The value of intra-particle or pore diffusion coefficient was found to be Kp (mg/g min0.5) = 0.112. On the basis of energy used in the adsorption process and estimated value from Temkin model, adsorption is considered to be a physical process. The thermodynamic analysis revealed that the adsorption mechanism was spontaneous and endothermic, as reflected by the ΔG° and ΔH° values obtained.