Dodecylamine Hydrochloride (DAH) Enhances Coal Tailings Dewatering: A Combined Experimental and Simulation Study on the Boundary Slip Effect

Efficient dewatering of fine https://creativecommons.org/licenses/by/4.0/clay-rich coal tailings water is a critical bottleneck in water process engineering, restricting water recovery and increasing environmental discharge risks. This study demonstrates that dodecylamine hydrochloride (DAH) induces boundary slip at the solid–liquid interface to significantly improve the dewatering performance of filter cakes composed of kaolinite, a typical clay mineral. A slip-modified capillary filtration model was developed by incorporating slip length into the classical capillary filtration framework, quantitatively linking interfacial slip to cake-specific resistance and filtrate flow. DAH adsorbed onto kaolinite via electrostatic attraction and hydrogen bonding, enhancing surface hydrophobicity and increasing the interfacial slip length to approximately 70 nm. Consequently, the cake-specific resistance decreased from 1.90 × 1015 to 0.76 × 1015 m−2, and the filtration rate increased markedly. X-ray microtomography showed that the addition of DAH produced a more connected pore network: total porosity increased from 12.62% to 13.73%, effective porosity increased from 9.09% to 11.74%, and the isolated-pore fraction decreased from 27.73% to 14.57%. Lattice Boltzmann simulations further revealed that boundary slip induced by DAH addition reduces interfacial resistance within pore channels, increases the fraction of high-velocity streamlines, and thereby markedly enhances permeability. These findings confirm that DAH addition triggers boundary slip and improves the dewatering performance of kaolinite, which provides a theoretical basis for enhancing dewatering performance and process efficiency in the treatment of clay-rich coal tailings.