A structurally tunable interface control reagent for efficient Solid-Liquid separation in coal flotation tailings

The solid–liquid separation of coal tailings is crucial for enhancing coal resource utilization and water circulation. With the mining and processing of low-quality coal, the coal flotation tailings (CFT), characterized by fine particle size, variable mineral composition and complex particle surface properties, presented significant challenges to efficient solid–liquid separation. This study synthesized a series of polycarboxylate ether (PCE) reagents with tunable structure to optimize solid–liquid separation performance and investigate their interaction mechanisms with CFT. The results showed that increasing the carboxyl acid ratio in PCE significantly improved settling and filtration performance. Increasing the carboxyl acid ratio in PCE from 2:1 to 6:1 improved settling rate by 6.5 times and sediment solid content by 9.13 wt%, while reducing specific filtration resistance by 42.86% and filter cake moisture by 3.14%. Analysis of particle surface electrical property and wettability indicated that an increase in the carboxyl acid ratio in PCE enhanced its ability to neutralize the negative charges on the particle surface and its hydrophobic ability. The growth behavior and properties of flocs were investigated by means of focused beam reflectance measurement microscopic observation and fractal dimension analysis. The results showed that an increase in carboxyl acid ratio in PCE promoted floc growth, regrowth, and shear resistance. The floc size increased by 10.48%, and the fractal dimension increased from 1.532 to 1.636, resulting in the formation of flocs with a denser structure. These improvements in floc properties were closely related to the enhancement of CFT settling and dewatering performance. This study provided new insights into the mechanisms of PCE in enhancing solid–liquid separation of coal tailings and highlighted its potential for treating complex tailings.