Efficient adsorption of Hg2+ ions on chitin/cellulose composite membranes prepared via environmentally friendly pathway

Chitin/cellulose blend membranes were successfully prepared in 7 wt% NaOH/12 wt% urea aqueous solution via a freezing/thawing method to dissolve chitin, and then by coagulating with 5 wt% Na2SO4 to regenerate. The morphology and structure of the resultant composite membranes were investigated by scanning electron microscope, thermogravimetry, X-ray diffraction and Fourier transform infrared spectroscopy. The metal ions adsorption capacities of the membranes were determined by atomic absorption spectroscopy. The results revealed that the composite membranes exhibited efficient removing of heavy metal ions (mercury, copper and lead) from aqueous solution, as a result of their microporous structure, large surface area and affinity on metal ions. The uptake capacity of the heavy metal ions on chitin /cellulose blend membranes increased with the chitin content. The amount of metal ions adsorbed onto the unit amount of the membrane (qe) was in the order of Hg2+ > Pb2+ > Cu2+, indicating a good adsorption of Hg2+. The adsorption equilibrium was well described by Langmuir adsorption isotherms, showing a monolayer adsorption. The major mechanism of the adsorption of metal ions by chitin/cellulose composite membranes could be described as multi-interactions including complexation, electrostatic attraction, and metal chelation and ionic exchange. Moreover, the chitin/cellulose membranes could be easily regenerated. This work provided a “green” pathway for removing of the hazardous materials in wastewater.

► In this work, the chitin/cellulose composite membranes were prepared by directly dissolving chitin and cellulose in 7 wt% NaOH/12 wt% urea aqueous solution at low temperature.
► The membranes exhibited high efficiency to remove heavy metal ions from wastewater, and indicated a superior adsorption of Hg2+.
► The chitin/cellulose sorbents had good mechanical properties, and could be recovered completely.
► The major mechanism of the adsorption of metal ions by chitin/cellulose composite membranes was described as multi-interactions.