Performance evaluation of activated carbon from neem seed shells (azadirachta indica a. juss) for the removal of complex mixture of dye (methylene blue) and heavy metals (copper, nickel and iron)

Industrial and urban wastewater contributes significantly to environmental pollution. That is why, it is essential that wastewater be treated before being discharged into the environment. The aim of this study is to evaluate the performance of Activated Carbon (AC) from neem seed shells for the removal of a complex mixture of dye and heavy metals (Methylene Blue (MB), copper, nickel and iron) in aqueous solution. The AC used in this study was produced by chemical activation with phosphoric acid (85%) at an impregnation ratio of 1/3, at 120°C for 6 hours, followed by pyrolysis at 528°C for 1 hour. The AC contains has high porosity, methylene blue (39.21 mg.g⁻¹), and iodine (788.20 mg.g⁻¹) indices, and a heterogeneous surface rich in functional groups (alcohols, carboxylic acids, esters, aldehydes, ketones, ethers and lactones). The study of adsorption kinetics reveals that the pseudo-second order model best describes the adsorption of all the pollutants studied, except for the copper, which is better described by the pseudo-first order model. Isotherm modelling shows that the adsorption of all pollutants, except for the Ni(II) is best explained by the Langmuir model, while that of Ni(II) ions is best described by the Freundlich model. The results indicate that AC is more effective at removing dye than heavy metals, with an affinity order of BM > Ni(II) > Fe(II) > Cu(II). This study shows that neem seed shells, considered waste, are an excellent precursor to produce commercial AC that can be used to treat wastewater.