Use of polyurethane foams for the removal of the Direct Red 80 and Reactive Blue 21 dyes in aqueous medium

The use of polyurethane foam (PUF) as an alternative adsorbent was investigated with the objective of removing Direct Red 80 (DR80) and Reactive Blue 21 (RB21) dyes from aqueous solutions. The adsorption isotherms were obtained in batches using the Langmuir model, which accurately described the sorptive behavior of the system with a correlation coefficient of R2 > 0.98. The maximum adsorption capacities of PUF for DR80 and RB21 dyes were 4.50 and 8.31 mg g− 1, respectively. The static studies were conducted in a glass column with an internal volume of 11.40 cm3 that was filled with 1 g of foam. Univariate experiments were conducted to investigate the influence of 2.5, 7.5, 12.5 and 17.5 mL min− 1 flow and the influence of dye concentrations on the interval between 10 to 60 mg L− 1 in the foam adsorption process. With dye concentrations maintained at 30 mg L− 1, a 22 central composite design (CCD) was applied whose variables of interest were pH and flow. The best experimental conditions for the adsorption of each dye were established after data processing and surface response analysis. It was observed that under optimized experimental conditions the removal of the studied dyes was over 80%.

► The batch studies indicated that the acidic environment favored the adsorption of both dyes by the polyurethane foams.
► The Langmuir isotherms showed a correlation coefficient of > 0.98 for both dyes.
► Removal above 80% for concentrations of 30 mg L− 1 for both textile dyes in aqueous solution was observed.