Influence of terminal group structure in hydrophilic long side chains of polycarboxylate dispersants on the properties of coal water slurry: experimental and simulation insights

Polycarboxylate dispersants (PCs) are high-performance additives with a structure – activity relationship that is crucial for the preparation of low-rank coal water slurry (LCWS). This study investigates how variations in the terminal group structures of hydrophilic long side chains grafted onto PCs affect the dispersion performance of LCWS. Three PCs with the terminal group of hydrophilic long-side chains as methyl, naphthalene ring, and multi-benzene ring were synthesized, denoted as PC-PEG, PC-BNO, and PC-AE, respectively. The results indicate that the apparent viscosity of LCWS prepared with PC-BNO and PC-AE, is approximately 200 mPa·s lower than that of PC-PEG. Additionally, all three LCWS samples exhibited strong shear-thinning behavior. A combination of experiments and molecular dynamics simulation (MD) was adopted to investigate the dispersion mechanism of the three PCs. The experimental results reveal that the dispersant adsorption capacity of PC-BNO and PC-AE is significantly enhanced, and compared with PC-PEG, the absolute zeta potential of PC-BNO increases apparently. The results of MD simulation indicate that the terminal group modification primarily affects the adsorptivity or optimizes the adsorption behavior of PC, thereby enhancing their dispersion performance. Based on this study, PC-AE has a stronger compatibility with low-rank coal to prepare high-performance LCWS.聚羧酸系分散剂（Polycarboxylate dispersants, PCs）是一类高性能添加剂，其结构-活性关系对于低阶煤水浆（low-rank coal water slurry, LCWS）的制备至关重要。本研究探究了接枝于PCs上的亲水长侧链的端基结构变化对低阶煤水浆分散性能的影响。研究团队合成了三种亲水长侧链端基分别为甲基、萘环与多苯环的PCs，分别记为PC-PEG、PC-BNO与PC-AE。实验结果表明，采用PC-BNO与PC-AE制备的低阶煤水浆的表观黏度较PC-PEG组低约200 mPa·s。此外，三种低阶煤水浆样品均表现出显著的剪切变稀行为。本研究采用实验与分子动力学模拟（molecular dynamics simulation, MD）相结合的方法，探究了三种PCs的分散机制。实验结果显示，PC-BNO与PC-AE的分散剂吸附容量显著提升；相较于PC-PEG，PC-BNO的绝对ζ电位明显升高。分子动力学模拟结果表明，端基改性主要通过影响或优化PCs的吸附行为，进而提升其分散性能。基于本研究结果，PC-AE与低阶煤的相容性更强，可用于制备高性能低阶煤水浆。