Facile and Sustainable Modi cation for Improving the Adsorption Ability of Sugarcane Bagasse Towards Cationic Organic Pollutants

Using low-cost agro-industrial wastes and by-products derived from 5 lignocellulosic biomass for adsorption is believed to an affordable and sustainable way to tackle 6 the burning issue of cationic pollution in the marine, while its relatively low adsorption 7 capability limits its large-scale application. Chemical modifications to improve the adsorption 8 abilities of lignocellulosic biomass usually has problems such as long reaction time, high 9 operational cost, rigorous reaction conditions (high temperature and pressure) as well as the 10 second pollution. In this study, a green, rapid, simple, and mild method was developed by using 11 ozone to improve the adsorption abilities of sugarcane bagasse (SB). The effects of ozone 12 Jun Li* State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China; Email: ppjunli@scut.edu.cn Pengcheng Luan# State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China Jianming Liao# State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China Li Chen State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China Yuxiang Zhang State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China Yikui Zhu State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China Yonghong Dai Guangxi Boguan Environmental Products Co., Ltd., Guangxi, 547000, China Lihuan Mo State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510641, China # P. L. and J.L. contributed equally to this work.


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Ocean, accounting for 71% of the total area of the earth, is of crucial importance not only 24 to the worldwide energy systems but also to the nutrient supplies. Statistics show that more 25 than 155 million tons of seafood are taken from the ocean every year, providing at least 20% 26 of total animal proteins for 3.1 billion people. 1 Besides, they are also important sources of  Recently, adsorption by using low-cost lignocellulosic biomass, especially for the agro-47 industrial wastes and by-products, to remove the cationic organic pollutants from the marine 48 environment is considered a promising technology because of its simple operation process and 49 high feasibility. 5 Among those agro-industrial wastes and by-products, sugarcane bagasse (SB), 50 in the form of pulpy fibrous material, is the main by-product of sugar industry after crushing 51 the sugarcane to extract their juice. Because sugarcane from Nature is the world's largest crop 52 by production quantity with an annual output of more than 1.8 billion tons, SB is a widely 53 available, cost effective, sustainable, and carbon neutral material. SB is commonly used as the 54 primary fuel source for sugar mills and sometimes for pulping. The use of low-cost SB to 55 modification to increase its adsorption performance. Additionally, both the raw material and 78 reaction product of ozone are usually oxygen, indicating the green nature of ozone modification. 79 In this study, we developed a simple and green method by using ozone to increase the     The 20-40 mesh fraction of SB was collected and used in this experiment. Analytical grade 100 H2SO4, NaOH, NaCl, and MB were used in this study.

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Ozone treatment. 10 g of SB was firstly treated by 10 wt% H2SO4 at pH 2.0 for 30 min.

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Then the mixture was diluted by H2SO4 solution (pH = 2.0) to 40 wt% consistency. The  Table 4. ±25°C for 4h to obtain the weight of its ash. The weight of the solid residue after deducting 128 the weight of its ash is the weight of acid-insoluble lignin.

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The selectivity coefficient of ozone towards lignin and carbohydrates (cellulose and The copper number was determined according to Tappi standard method (T 430 cm-09).

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The carbonyl content was linear correlated with the copper number and calculated by the     (Figure 4a). This process can be divided into three steps 13 : the 308 formation of carbonyl groups, followed by oxidation to carboxyl groups, and 309 decarboxylation. 14 The reason for the steady-state of carboxyl content could be that the rate of 310 oxidation of the carbonyl groups to carboxyl groups was approximately equal to that of 311 decarboxylation. 14 Importantly, the total carboxyl and carbonyl groups were increased about The subsequent decrease could be due to the redeposition of dissolved lignin with a certain 345 carboxyl content. The carboxyl groups on the SB surface increased dramatically during the 346 ozone modification with a maximum increase of 257% at the ozone consumption of 3.0 wt%.

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When the ozone consumption reached 7.7 wt%, the carboxyl groups still increased about 132%.

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Overall, after ozone treatment, the surface of SB contains increased anionic groups (carboxyl 349 groups) and less hydrophobic lignin to expose the abundant hydroxyl groups, which could be 350 beneficial to its adsorption rate.    Table 3), among all the ozone-modified SB, Sample 1 exhibited the 375 largest adsorption capability of 9.237 mg/g SB, 11.3% higher than the original SB (8.295 mg/g 376 SB), and largest adsorption rate of 0.624 mg·g -1 ·min -1 after 10 minutes of contact with MB, 377 33.3% higher than original SB (0.416 mg·g -1 ·min -1 ). As the ozone consumption charge further 378 increased, both the maximum adsorption rate and adsorption capacity of SB slightly decreased.

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To reveal the mechanism of the ozone-modified SB participating in the MB adsorption 380 process, three kinetic models were adopted, namely irreversible first-order, reversible first-381 order, and pseudo-second-order models ( Table 2). The irreversible first-order model is derived 382 as the assumption that once adsorbed, the particle cannot diffuse along or desorb from the From Figure 5c~e and Table 3, compared to the other two models, pseudo-second-order 391 model is the best fitted model for both original and ozone-modified SB with a R 2 higher than 392 0.990. In addition, since the nonlinear regression method is believed to be more appropriate for 393 determining the rate kinetic parameters, 25, 26 nonlinear pseudo-second-order kinetic model was 394 also adopted in this study (Table 2). As shown in Figure 5f, the non-linear pseudo-second-order 395 kinetic plots correlated well with the experimental data (R 2 >0.990). The related adsorption 396 parameters (kⅡ and qe, Table 3) were very close to that of linear pseudo-second-order model 397 (kⅡ and qe) and the experimental data (qe), which further confirmed that the pseudo-second-398 order model could be suitable for investigating the adsorption mechanisms of SB towards MB.

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This indicated that the adsorption of MB by SB was more like the chemisorption-based process  Where R 2 is the squared regression correlation coefficient. In this study, SB was successfully modified by ozone at normal pressure and temperature.