Characterization of Activated Carbon Prepared From the Nucleus of Ziziphus Lotus (NBEG): Isothermal Study and Kinetics of Adsorption of Methylene Blue

25 Ziziphus lotus (Nbeg) is very common in Morocco where it occupies various ecosystems and 26 presents different interests; however it remains devalued and knows recent deterioration due 27 to the human pressure through clearing, wood collection, irrational cuts’ exploitation an d 28 overgrazing. This study aims to prepare activated carbon from the cores of this interesting 29 biomaterial, for the first time to the best of our knowledge, according to a manufacturing 30 process based on its chemical and thermal activation. The cores of Ziziphus lotus (Nbeg) were 31 chemically activated by sulfuric acid (H 2 SO 4 , 98%) for 24h with a mass contribution (1:1), 32 and then carbonized at a temperature of 500 °C for 2 hours. The obtained activated carbon 33 was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform 34 infrared spectroscopy and specific surface measurement. These characterization results 35 showed an important porosity and a surface structure having acid groups and carboxylic 36 functions. The adsorption of methylene blue (MB) was evaluated, by Langmuir and 37 Freundlich models examination, in order to explain the adsorption efficiency in a systematic 38 and scientific way. Also pseudo-first order and pseudo-second order kinetic models were used 39 to identify the possible mechanisms of this adsorption process. The results showed that the 40 MB adsorption process on activated carbon follows the Langmuir model and that the 41 adsorption kinetic is best represented by kinetics data of the pseudo-second order model. 42 Therefore, Z. lotus can be used as a low-cost available material to prepare a high quality 43 activated carbon having a promising potential in the wastewater treatment. 44 This study was carried out in order to prepare an activated carbon from a biomaterial by using a manufacturing process based on chemical and thermal activation. The results of this work show that the cores of Ziziphus lotus (Nbeg) represent an interesting source of raw material 319 for the preparation of high quality activated carbon. The activated carbon was obtained using 320 a chemical and thermal activation processes. The chemical activation was carried out by 321 sulfuric acid (H 2 SO 4 , 98%) with a mass contribution (1:1), and the carbonization was 322 conducted at a temperature of 500ºC for a duration of 2 h. Characterization results by 323 scanning electron microscopy and Fourier transform infrared spectroscopy reveals the presence of a porous structure having different functions on the surface of CNZL. Moreover, 325 results show that the adsorption process is very fast. The adsorption isotherm data are well fitted with the Langmuir monolayer model. Kinetic modeling of MB adsorption on CNZL activated carbon follows the pseudo-second order model well. Furthermore, these results proved that CNZL can be used as a new low-cost carrier for the remediation of urban and industrial waste-water loaded with organic pollutants such as dyes. Finally, this carbon should 330 be promoted and considered as a cheaper alternative to commercial adsorbents.


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Water is the most fundamental and essential element of all natural resources. Its role is crucial 50 for the economic and social development of a country; nevertheless the management of water 51 resources is a challenge for most countries in the world. Currently, these resources are facing 52 problems of quantity and quality, related to global warming and irrational use. Thus, their 53 quality is increasingly worsened by various pollutant discharges, such as urban and industrial 54 wastewaters (Touzani et al., 2020), leading to pollution of surface water, groundwater and 55 soil, which can directly affect ecosystems and the services they provide (Corcoran, 2010). 56 Waste-water can contain many substances, in solid or dissolved forms that are more or less 57 biodegradable (Alsheyab et al., 2018). Among these organic micro-pollutants, dyes are used 58 in many industrial sectors such as textiles, food and cosmetics. Dyes have characteristics of 59 synthetic origin and a complex molecular structure that makes them more stable and difficult 60 to biodegrade (Ghaedi et al., 2014). The various dyes that exist in industrial effluents can 61 present adverse environmental effects, as they cause a change in the color of waters, reducing 62 sunlight penetration and photosynthetic activities (Sikdar et al., 2020). As a result, ecological 63 damage can spread downstream to agricultural or aquaculture areas, affecting aquatic flora 64 and fauna (Abbas and Trari, 2020). In addition, they can also cause eye burns responsible for al., 2016). In addition, it is universal as it can be used to remove soluble, insoluble, and 73 biological contaminants with 90-99% removal efficiency compared to other treatment 74 methods. 75 Since the introduction of this process, activated carbon has been one of the most frequently 76 used products due to its highly developed adsorption capacity. The main characteristics of 77 activated carbon are its porous structure, in relation linked to the accessible specific surface 78 area into which molecules can penetrate, the pore size distribution and their average 79 geometric shape (Li et al., 2020). The adsorption properties of activated carbon depend on the 80 functional groups, resulting mainly from the activation process, on the precursors, and thermal     Where qe and qt are the quantities of adsorbed ion (mg.g -1 ) at equilibrium and time t, 165 respectively, and k1 is the equilibrium velocity constant of pseudo first order (min -1 ).

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Pseudo-second order 167 This model is defined in the form below (Raoul et al., 2014).
Where k2 is the pseudo-second order adsorption rate constant (g/mg.min).

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Adsorption isotherms 171 An adsorption process can be described using an adsorption isotherm. Langmuir and carbon. An isotherm is a curve that represents the relationship between the amount of solute

Specific surface 239
The structure of an adsorbent is well defined by its specific surface area which represents the 240 total surface area per unit mass of the product accessible to atoms and molecules, as well as 241 the pore volume, the pore shape and the pore size distribution. Figure 5,  The correlation coefficients as well as the kinetic constants corresponding to the two models and Kf, respectively, can be calculated. Table 3 summarizes the results of both isotherms.

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These results show that the correlation coefficient R2 of the adsorption isotherm of the    This study was carried out in order to prepare an activated carbon from a biomaterial by using 317 a manufacturing process based on chemical and thermal activation.