A Synthesis of Magnetic Natural Coagulant and Its Application to Treat Congo Red Synthetic Wastewater

Abstract

Natural plant-based coagulant has been extensively studied these days due to its effectiveness and efficiency in wastewater treatment. However, utilization of plant-based coagulant happens to hold certain drawbacks, namely a long settling time and an increase of dissolved organic in the treated water. A combination of magnetic iron nanoparticles and plant-based protein was subsequently proposed as a solution. In this study, magnetic natural coagulant was synthesized via adsorption of Leucaena (Leucaena leucocephala) protein on tannic acid–modified Fe3O4. The obtained magnetic coagulant was furthermore analyzed using Fourier transform infrared spectroscopy to observe the characteristics before and after protein adsorption. The effect of pH (2 to 4) and coagulant dosage (25 to 250 mg L¯¹) on the removal of Congo red from wastewater and sludge formation was observed. The best condition was found at pH 2 due to the charge neutralization mechanism. Furthermore, the highest removal of 89.10% with a sludge volume of 4 mL L¯¹ and a settling time of 5 min was obtained at a magnetic coagulant dosage of 100 mg L¯¹ and pH 2. The removal result was comparable with a crude extract of Leucaena, however with a much faster settling time. Furthermore, coagulation using magnetic natural coagulant resulted in higher removal of dissolved organics in the treated water, compared to crude extract, where the increase of organic contents was detected due to the presence of various soluble organic compounds in the crude extract. The results obtained in this study show a promising application of magnetic natural coagulant for sustainable water–wastewater treatment.