Gl. Rorrer et al., SYNTHESIS OF POROUS-MAGNETIC CHITOSAN BEADS FOR REMOVAL OF CADMIUM IONS FROM WASTE-WATER, Industrial & engineering chemistry research, 32(9), 1993, pp. 2170-2178
Chitosan is a glucosamine bipolymer capable of adsorbing transition-me
tal ions from aqueous solution. Highly porous chitosan beads were prep
ared by dropwise addition of an acidic chitosan solution into a sodium
hydroxide solution precipitation bath. The gelled chitosan beads were
cross-linked with glutaraldehyde and then freeze dried. Beads of 1- a
nd 3-mm diameter were prepared. Beads of 1-mm diameter possessed surfa
ce areas exceeding 150 m2/g and mean pore sizes of 560 angstrom and we
re insoluble in acid media at pH 2. Well-mixed batch adsorption experi
ments revealed that both metal and hydronium ions compete for availabl
e adsorption sites by a chelation mechanism. Adsorption isotherms at 2
5-degrees-C and pH 6.5 over the concentration range 1-1690 mg Cd2+/L p
ossessed a stepped shape and maximum adsorption capacities for the 1-
and 3-mm beads were 518 and 188 mg of Cd/g of bead, respectively. The
stepped shape of the isotherm was explained by a pore-blockage mechani
sm.