Synthesis and characterization of CCDA
Cellulose extracted from pine needle of P. wallichiana was converted into its sodium salt by reaction with NaOH. It was crosslinked with 1:1 ratio of epichlorohydrin and NH4OH which binds the two cellulose chains through single bondOH group at C6 position [30]. CC so obtained was then oxidized with NaIO4 to get the final product, CCDA. The periodate oxidation proceeds by breaking of the glucopyranose ring by the selective cleavage of the vicinal diol at 2,3 position resulting in the formation of two aldehyde functional groups. The periodate anion forms a cyclic intermediate via co-ordination with 2,3-diol which then rapidly converts to the dialdehyde stage with the loss of iodate [31]. In the present case, cellulose was oxidized with a 60% degree of oxidation (aldehyde content). The overall scheme of CCDA synthesis from cellulose and its use in CR adsorption is presented in Scheme 1.