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.

混凝是一种水和废水处理技术，由于其高效和高效而已被广泛使用。各种无机盐通常用作凝结剂；但是，使用这些化学混凝剂会产生一些负面影响，例如成本高，污泥量大以及对人体健康的潜在负面影响。为了克服这些问题，已经探索了基于天然的凝结剂以减少和替代化学凝结剂。在这项研究中，我们调查了使用0.5 M MgCl ₂提取的白花白桦种子蛋白的利用溶液作为天然混凝剂来处理合成刚果红废水。从不同pH下的蛋白质溶解度曲线，可以观察到白桦蛋白的等电点在pH 4附近。通过使用响应表面法（RSM）-中央复合设计（CCD）改变pH（ 2.93–4.12），凝结剂剂量（183.52–496.58 mg eq BSA / L）和染料浓度（44.1–56 mg / L）。该实验设计用于获得最佳的条件，该条件给出了最大的染料去除率和最小的污泥量。发现pH，凝结剂剂量和染料浓度对于染料去除和污泥量是重要的。此外，很明显，电荷中和是该研究中的凝结机理。基于所获得的模型，染料的去除率为88.61％，去除率为16。在最佳条件下获得93 mL / L的污泥量。预测的最佳条件与误差值较低的实验数据吻合良好。获得的结果暗示了白桦作为天然凝结剂的良好效力。