Accepted Manuscript Molecular mechanism of anionic dyes adsorption on cationized

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Fig. 3. (a) Point of zero charge of CRHC, (b) Effects of pH on Diamine Green B 
(DG-B), Acid Black 24 (AB-24) and Congo Red (CR) adsorption onto CRHC. 
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Fig. 4. The possible molecular mechanism of Diamine Green B (DG-B), Acid Black 
24 (AB-24) and Congo Red (CR) adsorption onto CRHC 
The electrolyte in the dye bath will block the coulomb charge between the dye 
and the adsorbent, resulting in a decrease in the electrostatic interaction force, which 
will increase or decrease the adsorption capacity of the dye onto the adsorbent. Fig. 5a 
shows the effect of ionic strength on the adsorption capacity of Diamine Green B 
(DG-B), Acid Black 24 (AB-24) and Congo Red (CR). As can be seen from Fig. 5a, 
the adsorption capacity of three dyes increased with the increasing of sodium chloride 
concentration, indicating that electrostatic interaction force is not the only force 
between the dye and the adsorbent, Van der Waals force and hydrogen bonding force 
may still exist. Moreover, the salting-out effect leads to a decrease in the solubility of 
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the dye and a decrease in the hydrophilicity of the dye, which leads to an increase in 
the adsorption of the dye by the hydrophobic effect [35]. So, the higher ionic strength 
thus improves the dye adsorption capacity onto CRHC. 
Fig. 5. Effect of ionic strength on the adsorption of Diamine Green B (DG-B), Acid 
Black 24 (AB-24) and Congo Red (CR). 
3.4 Reusability 
From a practical point of view, the reusable experiments are of great significance 
for the practical application of the adsorbents. The adsorption-desorption cycle was 
repeated five times and the results are shown in Fig.5b. The adsorption capacity was 
decreased with the increasing of cycle times. However, the regenerated CRHC still 
possessed a high adsorption capacity for Diamine Green B (DG-B), Acid Black 24 
(AB-24) and Congo Red (CR), and the decrease in adsorption capacity is not 
significant. It is recommended that the CRHC has a good reusability and high 
adsorption performance for dye removal. 

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