Synthesis and characterization of iodo polyurethane foam and its application in removing of aniline blue and crystal violet from laundry wastewater

A new sorbent was prepared by treating polyurethane foam with HCl and replacing the amino functional groups with iodine atoms. The properties of iodo-polyurethane were studied with infrared, ultraviolet and visible spectroscopy, bulk density, pHZPC and elemental and thermal analysis. Removal of aniline blue and crystal violet dyes from water with iodo-polyurethane were investigated with the batch technique. Maximum removal was achieved at pH 7–12. The effect of the initial dye concentration on the equilibrium adsorption from aqueous solutions with iodo-polyurethane was found to have a good correlation, with r2 = 0.995 and an intercept of 0.039 when analyzed in the Langmuir and Freundlich isotherm models. The capacity of iodo-polyurethane for aniline blue and crystal violet were 0.24 and 0.45 mmol g−1, respectively (188.9 and 183.6 mg g−1). The values of ΔG and ΔH were −7.7 kJ mol−1 and −26.1 kJ mol−1, respectively, indicating that sorption is spontaneous and exothermic. The sorption rate of the dyes onto iodo-polyurethane was rapid, with 50% removal within 50 s. The pseudo-second order equation best described the kinetics of absorbed aniline blue and crystal violet (r2 = 0.994). A modified equation (y = ax0.n) was used to treat deviation from the Morris–Weber model for the sorption diffusion mechanism of crystal violet onto iodo-polyurethane. Use of iodo-polyurethane for removing aniline blue and crystal violet contamination from laundry wastewater is thus possible.