Accepted Manuscript Molecular mechanism of anionic dyes adsorption on cationized
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| 2.6 Reusability studies
A recyclability experiment was conducted to test the reusability of the CRHC. After adsorption, the CRHC was soaked in a 0.1 mol L -1 NaOH solution and shaken at 120 rpm for 5h to obtain the regenerated CRHC. The regenerated CRHC was washed several times with deionized water, dried in a vacuum oven at 60°C and weighed for the next reuse cycle. After then, adsorption experiments were carried out to analyze the ability of regenerated CRHC adsorbent to remove Diamine Green B (DG-B), Acid Black 24 (AB-24), and Congo Red (CR) dye from the solution. In order to test the ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 9 reusability of CRHC, the adsorption-desorption cycle was repeated five times. 3. Results and discussion 3.1 Chemical composition Table 1 shows the chemical composition of Rice husks (RH), delignified rice husks (RHD), and bleached rice husks (RHC). It shows that the cellulose content was significantly increased by removing amorphous components such as lignin, hemicelluloses, and silica. During the alkali treatment process, a large amount of destruction of the lignocellulosic structure occurred resulting in an improvement in defibrillation. The partial hydrolysis of hemicelluloses and depolymerisation of a lignin unit also occurred, causing sugars and phenolic compounds to dissolve in water [22]. Moreover, most of hemicelluloses and lignin components present in the RH are dissolved [23]. So, some loose substance in the RH can be easily removed except for some hard components which are difficult to remove from the cell wall in the delignification process [24]. The alkali treatment was efficient in increasing the percentage of cellulose content of RH. Moreover, almost all of the silica content was removed during alkali treatment. For the bleaching process, there is a further decrease in the percentage of hemicelluloses and lignin and thus increasing the percentage of cellulose component present in the sample, resulting in almost pure rice husk cellulose (RHC), which reached 96%. Table 1 Chemical composition of Rice husks (RH), delignified rice husks (RHD), and bleached rice husks (RHC). Rice husks (RH) Delignified rice husks (RHD) Bleached rice husks (RHC) Cellulose (%) 33 72 96 Hemicellulose (%) 27 17 - Lignin (%) 18 7 - Silica ash (%) 18 - - tải về 1.26 Mb. Chia sẻ với bạn bè của bạn:
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