Abstract:
Coagulation is a water and wastewater treatment technology that has been widely used due to its high efficiency and effectiveness.
Various inorganic salts are commonly used as coagulant; however, there are some negative impacts of utilization
of these chemical coagulants, such as high costs, large sludge volume, and also potential negative impact to human health.
To overcome these problems, natural-based coagulants have been explored to reduce and substitute chemical coagulants.
In this study we investigated utilization of Leucaena leucocephala seed protein, extracted using 0.5 M MgCl2 solution as
natural coagulant to treat synthetic Congo red wastewater. From the protein solubility profile at various pH, it could be
observed that leucaena protein’s isoelectric point was around pH 4. The optimization of coagulation condition was done by
using Response Surface Method (RSM)—Central Composite Design (CCD) with variations of pH (2.93–4.12), coagulant
dose (183.52–496.58 mg eq BSA/L), and dye concentration (44.1–56 mg/L). This experimental design was used to obtain
the optimum condition that gave maximum dye removal percentage and minimum sludge volume. It was found that pH,
coagulant dose, and dye concentration were significant for dye removal and sludge volume. Furthermore, it became evident
that charge neutralization was the coagulation mechanism in this study. Based on the obtained model, 88.61% dye removal
with 16.93 mL/L sludge volume was obtained at the optimum condition. The predicted optimum condition was in a good
agreement with experimental data with relatively low error value. The obtained result implies good potency of leucaena as
natural coagulant.
