Biomedical Engineering Reference
In-Depth Information
As shown in Fig.1, in the design boundary, each response surface plot had a clear peak and
the corresponding contour plot had a clear maximum, which means that the maximum
hydrogen yield could be achieved inside the design boundaries (Ghosh & Hallenbeck, 2010).
The yield of nanocellulose increased with increasing ratio of NKC-9 to MCC, temperature
and time to the optimal levels, and then decreased with a further increase in these
parameters. The optimized conditions for maximum nanocellulose yield can be obtained by
Design-expert software. The optimum values of the test variables in uncoded units obtained
were ratio of NKC-9 to MCC 9.97: 1, temperature 48.30°C, time 189.00min. At these
optimized conditions, the model predicted that the maximum yield of nanocellulose is
50.93%.
As to the actual experimental condition, some conditions were modified as follows: ratio of
NKC-9 to MCC 10: 1, temperature 48°C and time 189min. To confirm the model adequacy
for predicting maximum yield, three replicates experiments under modified conditions were
conducted and the maximum yield of nanocellulose obtained was 50.04% which agreed well
with the predicted value.
Yield
Yield
Yield
3.50
3.50
60.00
45.8836
45.1582
42.6312
44.2574
44.2574
45.1582
47.2762
43.6266
47.5097
47.0441
45.4514
3.25
3.25
55.00
5
5
3.00
5
50.00
3.00
47.2762
49.101
48.9301
47.0441
45.00
2.75
2.75
49.1359
45.8836
45.4514
43.6266
43.2722
43.6266
45.8836
45.1582
43.2722
41.8018
41.8018
41.3863
41.3863
40.00
2.50
2.50
5.00
7.50
10.00
12.50
15.00
40.00
45.00
50.00
55.00
60.00
5.00
7.50
10.00
12.50
15.00
A: ratio
B: temperature
A: ratio
(a) (b) (c)
Fig. 1. Two and three dimensional contour plots for the maximum yield of nanocellulose.
RSM plots were generated with the data shown in Table 2. (a) Yield of nanocellulose (%) as a
function of ratio of NKC-9 to MCC and temperature. (b) Yield of nanocellulose (%) as a
function of ratio of NKC-9 to MCC and time. (c) Yield of nanocellulose (%) as a function of
temperature and time.
The interactions between ratio of NKC-9 to MCC and time are not perfectly elliptical
(Fig.1(b)). The yield of nanocellulose increased with time rising up to certain level, beyond
which yield declined slightly. This may be due to that over reaction time completely digests
