Removal of brilliant green from aqueous solutions based on polyurethane foam adsorbent modified with coal

Coal, resulted from plants degradation, is composed primarily of carbonaceous materials along with minerals (chiefly hydrogen, sulfur, oxygen and nitrogen). Because of its availability, coal is one of the excellent adsorption capacities toward dyes. In this work, a series of novel polyurethane foam materials modified with coal (C/PUF) were prepared by one step foaming technology. The structure and thermal property of prepared foam materials were characterized by Fourier transform infrared (FTIR), thermalgravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The C/PUF was applied to the process of removal of brilliant green (BG) from aqueous. The effects of coal content, the adsorbent dosage and the temperature on the adsorption efficiency of BG dye solution were evaluated by a batch of adsorption experiments. Under optimal conditions (coal content of 4%, C/PUF dose of 4 mg/mL and time of 200 min at 40 °C), high removal efficiency of dyes (99.40%) was obtained. The experimental data were evaluated by Langmuir and Freundlich isotherm models. The results indicated that the adsorption system showed an excellent correlation with the Langmuir isotherm model, with maximum adsorption capacity (134.95 mg/g) of BG. The adsorption kinetics of the system was investigated and the result showed that the adsorption of BG onto C/PUF material followed pseudo-second-order kinetic model. The adsorbent showed a remarkable regeneration capability (no obvious change in adsorption capacity), making them an ideal candidate for removing BG from solution. This present study showed a simple way to treat BG using the polyurethane foam materials modified with coal by one step foaming technology.