Institute of Petroleum and Natural Resources, Pontifical Catholic University of Rio Grande do Sul, 6681 Ipiranga Avenue, Building 96J, 90619-900 Porto Alegre, Brazil.
State University of Rio Grande do Sul, 1156 Sete de Setembro Street, 90010-191 Porto Alegre, Brazil.
Sci Total Environ. 2020 Nov 25;745:140875. doi: 10.1016/j.scitotenv.2020.140875. Epub 2020 Jul 15.
Flocculants and coagulants market is expected to grow in a Compound Annual Growth Rate (CAGR) of 5.9% between 2017 and 2022. The development of non-pollutant coagulants/flocculants aiming to replace conventional ones, usually toxic, has been extensively studied and one alternative is the possibility of obtaining tannin-based flocculants, compounds present in many plants and easily extracted. However, in order to use tannins as flocculants, their cationization is necessary, which is normally accomplished by Mannich reaction that requires formaldehyde addition, a toxic compound. In order to fill a gap in the literature, regarding coagulants/flocculants synthesis through green procedures, this paper aims to synthesize a flocculant from tannins with no use of formaldehyde, and optimize this synthesis through a Central Composite Rotatable Design (CCRD). The optimization variables were ammonium hydroxide (NHOH) to tannin ratio, in the range of 1:1 to 5:1, and reaction time, in the range of 1 to 4 h The evaluation of the synthesized flocculant samples was accomplished by jar tests using a simulated effluent containing humic acid and the effect of reactant ratio and reaction time used in the synthesis was assessed. The flocculant synthesis methodology proposed on this study showed excellent results regarding turbidity and color removal, since 100% of turbidity removal and 89.9% of color removal were achieved. This novel tannin-based flocculant synthesis methodology is a promising technology to replace conventional coagulants/flocculants, once it is environmentally friendly.
絮凝剂和混凝剂市场预计在 2017 年至 2022 年间将以 5.9%的复合年增长率（CAGR）增长。为了取代通常有毒的传统污染物而开发的无污染物混凝剂/絮凝剂已得到广泛研究，其中一种替代方法是获得单宁基絮凝剂的可能性，这种化合物存在于许多植物中，并且易于提取。然而，为了将单宁用作絮凝剂，需要对其进行阳离子化，通常通过曼尼希反应来完成，该反应需要添加甲醛，这是一种有毒化合物。为了填补文献中的空白，关于通过绿色工艺合成混凝剂/絮凝剂，本文旨在不使用甲醛合成一种来自单宁的絮凝剂，并通过中心复合旋转设计（CCRD）优化该合成。优化变量为氨（NHOH）与单宁的比例，范围为 1:1 至 5:1，反应时间，范围为 1 至 4 小时。通过使用含有腐殖酸的模拟废水进行的罐试验评估合成絮凝剂样品，评估了合成中使用的反应物比例和反应时间的效果。本研究提出的絮凝剂合成方法在去除浊度和颜色方面表现出优异的效果，因为实现了 100%的浊度去除和 89.9%的颜色去除。这种新型基于单宁的絮凝剂合成方法是一种很有前途的技术，可以替代传统的混凝剂/絮凝剂，因为它是环保的。
