Removal of Congo red from aqueous solution using Moringa oleifera seed cake as natural coagulant

This study investigated the feasibility of Moringa oleifera seed cake powder (MOSCP), a natural product after oil extraction, for Congo red (CR) removal from aqueous solution. Coagulation experiments indicated that CR was efficiently removed by MOSCP in short time. Fourier Transform Infrared Spectroscopy spectra showed that large amount of proteins was contained in MOSCP. The removal of CR was contributed to both the adsorption and charge neutralization of proteins on the surface of MOSCP particles, and nucleation of these particles. No significant impact of solution pH was observed on CR removal under acid and neutral conditions, but the CR removal decreased remarkably with increasing pH under basic condition. An optimal MOSCP dosage was found that was linearly proportional to CR initial concentration.