![](bg4.png)
200 mins. Almost 90% of the ultimate sorption
occurred in the first 300 mins for all three sorbents,
and follwed with a quick approach to the
equilibrium. The Cd (II) removal percentages by BC,
BC+HA and HAC at equilibrium were 41.1%,
80.5%, and 82.7%, respectively. To fit the
experimental data, equations of pseudo first order
and pseudo second order were both used. For HAC,
the R
2
value of pseudo-second-order model (0.992)
was relatively higher than that of pseudo-second-
order model (0.982), indicating the chemisorption
involved between Cd(II) and sorbents in the sorption
process.
0 200 400 600 800 1000 1200 1400 1600
0
5
10
15
20
25
30
35
40
45
BC
BC+HA
HAC
pseudo-1st-order of BC
pseudo-1st-order of BC+HA
pseudo-1st-order of HAC
pseudo-2nd-order of BC
pseudo-2nd-order of BC+HA
pseudo-2nd-order of HAC
sorption amount (mg/g)
time (min)
Figure 4: Cd(II) sorption kinetics of BC, BC+HA and
HAC.
4 CONCLUSIONS
Based on the rice husk biochar and the
hydroxyapatite, a hydroxyapatite-biochar composite
was fabricated in this study. Through characteristics,
effect of initial pH and kinetic analysis, HAC
showed a better sorption performace than pure
biochar and a lower cost than physical mixture of
biochar and hydroxyapatite. The results revealed that
HAC exhibited a potential application as an
excellent sorbent for Cd (II) reduction from polluted
waters.
ACKNOWLEDGEMENTS
This research was supported by the following funds:
the National Science Foundation of China
(41807111), the Shandong Provincial Natural
Science Foundation, China (ZR2016YL002), and the
Research Project (Youth Fund) of Shandong
Academy of Sciences (2017QN007).
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