Removal of Cationic or Anionic Dyes from Water Using Ion Exchange Cellulose Monoliths as Adsorbents

This work deals with the preparation of poly(sodium p-styrenesulfonate) (PSS) and poly[(3-acryloylaminopropyl)trimethylammonium chloride] (APTAC) modified ion exchange cellulose monoliths (C-g-PSS and C-g-APTAC, respectively). The obtained ion exchange monoliths were employed for the removal of cationic or anionic dyes from aqueous solutions with particular reference to the effects of initial dye concentration, flow rate and ionic strength on adsorption. Detailed adsorption characteristics of ion exchange monoliths including operational parameters, adsorption kinetics and adsorption isotherms were investigated. Results showed exceptional affinity for adsorption of dyes due to the charge-induced adsorption. The observations from dynamic adsorption experiments indicated that the modified monoliths allowed ultra-fast adsorption of dyes at relatively high flow rates and were more favourable under low ionic strength conditions. An ultrahigh equilibrium adsorption capacity of 606.3 mg g−1 and dye removal efficiency of 72.3% for methylene blue was observed for the C-g-PSS monolith, which exhibited better adsorption performance than that of APTAC functionalized monolith for acid red 70. However, C-g-APTAC monolith was found superior in dye recoveries and regeneration, the adsorption efficiency can be maintained at 97% after 7 adsorption-desorption cycles. Combining the ultrafast adsorption kinetics with high removal capacity and good recyclability, the ion exchange monoliths have great potential for effluent treatment applications.