Effect of transition metal ions on the thermal degradation of chitosan

Figures & data

Table 1. Characteristic FTIR bands of chitosan–transition metal compounds

Sample		FTIR wave number (cm^−1) of different functional groups/bonds
		${\mathit{\nu }}_{{\text{OH+NH}}_2}$	νC=O coupled with δN–H	νC–N coupled with ωN–H	νC–O–C	β-(1–4) glycoside bridge	γN–H
CTS		3,520	1,613	1,406	1,024	1,133,875	706
CTS-Cd	1	3,451	1,613	1,405	1,024	1,133,878	644
	2	3,449	1,613	1,408	1,024	1,133,875	658
	3	3,454	1,625	1,408	1,024	1,139,871	659
	4	3,514	1,615	1,410	1,024	1,135,872	648
CTS-Ni	1	3,354	1,556	1,408	1,039	1,149,872	655
	2	3,336	1,596	1,412	1,022	1,131,868	646
	3	3,330	1,555	1,409	1,026	1,133,870	655
	4	3,326	1,553	1,412	1,026	1,130,870	655
CTS-Mn	1	3,516	1,641	1,414	1,039	1,132,874	715
	2	3,508	1,587	1,403	1,024	1,135,875	634
	3	3,480	1,628	1,410	1,024	1,136,873	694
	4	3,485	1,639	1,437	1,024	1,136,873	675
CTS-Co	1	3,495	1,556	1,406	1,024	1,135,867	655
	2	3,490	1,553	1,408	1,024	1,136,873	646
	3	3,512	1,610	1,405	1,024	1,132,869	643
	4	3,440	1,553	1,416	1,024	1,136,869	648
CTS-Zn	1	3,453	1,553	1,409	1,024	1,136,868	664
	2	3,442	1,612	1,415	1,024	1,133,868	644
	3	3,428	1,601	1,414	1,024	1,133,868	659
	4	3,352	1,559	1,411	1,024	1,133,871	651

Table 2. Characteristic temperatures and the extent of decomposition for the main thermal degradation of chitosan–transition metal compounds

Weight fraction (%)	^aPeak maximum (°C)					Weight loss (%)
	Cd(II)	Ni(II)	Mn(II)	Co(II)	Zn(II)	Cd(II)	Ni(II)	Mn(II)	Co(II)	Zn(II)
0	279.0	279.0	279.0	279.0	279.0	54.4	54.4	54.4	54.4	54.4
1	278.1	269.8	270.1	265.7	268.9	51.8	52.8	52.9	51.1	53.9
2	275.1	268.9	262.1	257.6	253.8	55.8	51.6	51.1	55.1	46.2
3	256.7	261.8	256.4	255.1	249.6	48.5	49.0	50.7	49.5	50.9
4	269.7	260.0	255.4	256.2	247.4	52.7	51.2	48.5	48.4	51.3

^a This temperature was obtained from differential TGA.

Table 3. Activation energies during the second thermal degradation stage of chitosan–transition metal compounds

Weight fraction (%)		Activation energy (kJ mol^−1)
		Period I (225–252°C)	Period II (252–282°C)	Period III 280–350°C)	Total value
CTS		19.6	49.5	19.6	88.7
Cd(II)	1	22.5	46.7	19.4	88.6
	2	24.6	43.8	18.2	86.6
	3	34.9	27.8	17.7	80.4
	4	27.2	37.7	14.9	79.8
Ni(II)	1	23.7	43.2	18.1	85.0
	2	27.6	40.3	17.2	85.1
	3	31.3	35.6	17.2	84.0
	4	36.7	32.4	15.3	84.4
Mn(II)	1	24.3	43.4	17.4	85.1
	2	30.2	38.0	16.1	84.3
	3	36.2	29.5	15.1	80.8
	4	36.4	28.7	15.3	80.4
Co(II)	1	24.2	44.1	16.4	84.7
	2	30.5	36.5	14.7	81.7
	3	36.8	30.5	14.1	81.4
	4	39.6	28.4	13.5	81.5
Zn(II)	1	23.5	45.1	16.0	84.4
	2	28.7	33.1	15.7	77.5
	3	28.5	32.6	15.5	76.6
	4	33.3	23.2	18.9	75.4