[Desorption behaviors of 4-nitrophenol on hyper-cross-linked polymer resin NDA-701]

Desorption behaviors of loaded 4-nitrophenol (4-NP) on hyper-cross-linked polymer resin NDA-701 were studied. The molar ratio of NaOH and 4-NP desorbed (M(NAOH/4-NP)) selection experiments were carried out at two different reaction temperature(303 K and 333 K). Desorption kinetics characteristic of4-NP on NDA-701 in the batch and fixed-bed mode were examined at different reaction temperature and M(NaOH/4-NP) values. The results showed that optimal M(NaOH/4-NP) values were 1.2 and 100% 4-NP could be desorbed from NDA-701 at two different temperature. When the M(NaOH/4-NP) was lower than 1.2, the desorption efficiency increases with the increase of temperature, but the function of temperature decrease with increasing of M(NaH/4-NP) values for desorption ratio. The information indicated that desorption thermodynamic characteristic of NDA-701 was controlled by M(NaOH/4-NP) values. Desorption kinetics in the alkaline system can be well described by pseudo-second-order kinetic model, and desorption rate is increased with the increase of desorption temperatures, the k2 value increase from 0.010 g x (mmol x min)(-1) to 0.035 g x (mmol x min)(-1) when desorption temperature increase from 303 K to 333 K. Nevertheless, higher M(NaOH/4-NP) values could not promote desorption rate if only M(NaOH/4-NP) value was larger than the optimal molar ratio of NaOH and 4-NP. When M(NaOH/4-NP) values increase from 1.2 to 5.0, the k2 value increase from 0.038 g x (mmol x min)(-1) to 0.044 g x (mmol x min)(-1) merely at 333 K. the results indicated that desorption kinetic characteristic of NDA-701 was controlled by temperature. NDA-701 can be completely recovered using 2 times Bed Volume of 2% NaOH solution at the temperature of 333 K, comparing with field application, implying that more energy and cost can be saved in comparison with the actual desorption process in the industry.