Synthesis of waterborne polyurethane–humic acid cross–linked biomass porous materials for the adsorption of methylene blue

A series of adsorbent materials (WPU-HA x – y ) with three–dimensional porous structure, green sustainability and excellent performance were prepared and evaluated for the removal of methylene blue using non–toxic and environmentally friendly waterborne polyurethane as matrix material and humic acid, a biomass material, as the functional material. The newly synthesised adsorbents were characterised by infrared spectroscopy, scanning electron microscopy, specific surface area and thermogravimetric. The effects of contact time (0–8 h), starting concentration (10–100 mg·L –1 ), pH (3–11), solution temperature (30–60 °C) and coexisting ions (Ca 2+ , Na + , K + , Mg 2+ ) on the performance were investigated. Pseudo-first-order, pseudo-second-order, elovich and intra-particle diffusion model were used to analyze the adsorption kinetics, the Langmuir, Freundlich, Temkin and Dubin–Radushkovich adsorption isotherms were evaluated, and the adsorption behaviour of the adsorbent materials was found to be more appropriate for the pseudo-second-order model for chemical pollutant removal and the Langmuir model which depends on monolayer adsorption. WPU-HA 2 -3 stood out with a maximum adsorption capacity of 813.0081 mg·g –1 fitted to the pseudo-second-order and 309.2832 mg·g –1 fitted to the Langmuir model, showing superior adsorption performance and regenerability.