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![Modeling of the positions of (a) 2,4-dichlorophenoxyacetic acid (2,4-D) and (b) 4-chloro-2-methylphenoxyacetic acid molecules adsorbed on the AC surface [10].](profile/Stanislav-Kulaishin/publication/361413762/figure/fig3/AS:11431281095309667@1667842030661/Modeling-of-the-positions-of-a-2-4-dichlorophenoxyacetic-acid-2-4-D-and-b.png)
Modeling of the positions of (a) 2,4-dichlorophenoxyacetic acid (2,4-D) and (b) 4-chloro-2-methylphenoxyacetic acid molecules adsorbed on the AC surface [10].
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![Fig. 1. Pore distribution for the samples F400, F400An, and F400NH 2 [48].](profile/Stanislav-Kulaishin/publication/361413762/figure/fig1/AS:11431281095309666@1667842030436/Pore-distribution-for-the-samples-F400-F400An-and-F400NH-2-48_Q320.jpg)
![Fig. 4. Chemical structures of (a) 2,4-D and (b) benazoline [89].](profile/Stanislav-Kulaishin/publication/361413762/figure/fig4/AS:11431281095342744@1667842030782/Chemical-structures-of-a-2-4-D-and-b-benazoline-89_Q320.jpg)
The influence of activation methods on the surface characteristics of activated carbons (ACs) and the relationships of these characteristics and the parameters of a medium with the efficiency of adsorption of herbicide molecules on ACs are considered. The main factors affecting the adsorption efficiency of ACs with respect to these pollutants are d...
Contexts in source publication
Context 1
... assumption that the carbonyl group acts as an electron donor to the aromatic nucleus of the adsorbate was also reported [99,100]. Figure 3 shows models of the most stable position of phenoxyacetic acid molecules on the AC surface [10]. Molecules of 2,4-D and 4-chloro-2-methylphenoxyacetic acid occupy a quasi-planar position on the AC surface (Fig. 3). ...
Context 2
... The assumption that the carbonyl group acts as an electron donor to the aromatic nucleus of the adsorbate was also reported [99,100]. Figure 3 shows models of the most stable position of phenoxyacetic acid molecules on the AC surface [10]. Molecules of 2,4-D and 4-chloro-2-methylphenoxyacetic acid occupy a quasi-planar position on the AC surface (Fig. 3). The energy of interaction between the adsorbent and the adsorbate is weak in this case; therefore, the physical nature of adsorption takes place. According to Spaltro et al. [10], there were no changes in the geometry of the test herbicide ...
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... The influence of carbon surface properties on adsorption effectiveness is widely investigated; however, despite much research, this area is not fully explained due to the many effects that determine the adsorption process. [33][34][35][36] However, the role of surface functional groups on other phenomena occurring in pores, like freezingmelting, is not a subject of many studies. 37,38 The role of solvents in adsorption systems is relatively rarely investigated. ...
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... In reviews by Kulaishin et al. 2022 [2] and Baskar et al. 2022 [3], adsorption on a variety of adsorbents, particularly on activated carbon (ACs), was emphasized as one approach for removing pesticides from the aqueous phase. There are certain drawbacks to other methods now in use, including the time needed for the process and reliance on environmental conditions for the biodegradation process, the need for energy for electrooxidation, and the photocatalytic process [2]. ...
... In reviews by Kulaishin et al. 2022 [2] and Baskar et al. 2022 [3], adsorption on a variety of adsorbents, particularly on activated carbon (ACs), was emphasized as one approach for removing pesticides from the aqueous phase. There are certain drawbacks to other methods now in use, including the time needed for the process and reliance on environmental conditions for the biodegradation process, the need for energy for electrooxidation, and the photocatalytic process [2]. ...
Adsorbents presenting high adsorption capacity, fast adsorption rate, easy regeneration, and a good possibility for reusability are ideal for removing 4-chloro-2-methyl-phenoxyacetic acid (MCPA) or other pesticides from wastewater. Here, the effects of regeneration treatments on adsorption–desorption cycles are examined using two commercial activated carbons (ACs) (Merck and Norit 1240 X). MCPA adsorption was fast on Merck and Norit ACs in powder form (6 h) but on Norit AC, in granular form, adsorption was too slow, and the equilibrium time was reached only after 288 h. MCPA adsorption kinetic data were analyzed by applying pseudo-first-order, pseudo-second-order, and Weber–Morris models. The pseudo-second-order model fit better to all data, and the Weber–Morris representation allows confirming that on Norit 1240 X, in granular form, the pore diffusion was the limiting factor concerning the MCPA adsorption. Merck and Norit 1240 X (in powder and granular form) ACs loaded with MCPA were submitted to different regeneration process by washing with distilled water, ethanol, HNO3, and NaOH solutions and washed with NaOH solutions or ethanol followed by a thermal treatment. The ACs regenerated with ethanol performed well in the subsequent adsorption–desorption cycles. All ACs had more than 99% desorbed MCPA after the first cycle of washing with ethanol. The washing with NaOH solution was less efficient. The regeneration process, consisting of washing the sample with a solution of NaOH and subsequent heating at 573 K, was very effective. After this regeneration procedure, the amount of MCPA adsorbed on Norit 1240 X AC was even higher than the amount adsorbed in the first adsorption cycle. At present, washing methods for adsorbent regeneration are not used at an industrial level. However, research for environmentally friendly regeneration methods is necessary to achieve the objectives of the circular economy.
... Among the most used methods for the removal of pesticides, from the aqueous phase, adsorption on a diversity of adsorbents, particularly on activated carbon (ACs) was highlighted, in reviews made by Kulaishin et. al in 2022 [1] and Baskar et. al, 2022 [2]. ...
... al, 2022 [2]. Some disadvantages concerning other methods currently used were identified, such as time consumption and dependency on environmental conditions for the biodegradation process, energy consumption for electrooxidation, and photocatalytic process [1]. ...
... Adsorption is a process with simple implementation and operation, being therefore widely used, for the removal of inorganic and organic contaminants from gaseous [3,4] or liquid effluents, such as drinking and wastewater [2]. However, adsorption present also has some limitations, such as adsorbent production cost, regeneration, and sustainable management of spent adsorbents [1][2][3][4][5]. ...
This paper describes the influence of the regeneration treatments on 4-chloro-2-methyl-phenoxyacetic acid (MCPA)-loaded activated carbons (ACs) on adsorption-desorption cycles with two commercial ACs, Merck and Norit 1240 X ( Norit 1240 X was used in a granular and powder form). The ACs were saturated with MCPA and then submitted to four regeneration cycles, by washing with ethanol, NaOH solutions and washed with NaOH solutions followed by a thermal treatment. The ACs regenerated with ethanol showed a better performance concerning the successive adsorption-desorption cycles. On the first cycle, the MCPA desorbed, from washing with ethanol, from all ACs was higher than 99%. After a fourth adsorption-desorption cycle, washing regeneration combined with thermal treatment allowed excellent regeneration results. The amount of MCPA adsorbed on Norit 1240 X AC was higher than the amount adsorbed in the first cycle. MCPA adsorption kinetic data were analyzed by applying pseudo-first-order, pseudo-second-order, and Weber-Morris models. The pseudo-second-order fit better fit to the data and the Weber-Morris representation allows confirming that on Norit 1240 X, in a granular form, the pore diffusion was the limiting factor concerning the MCPA adsorption.
... Finally, the maximum amount of each pesticide adsorbed on both ACs was slightly higher than the values obtained previously on ACs prepared from Tectona Grandis sawdust, by physical activation with CO 2 , at 973 K (maximum adsorption capacity of MCPA on Teak-7480 was 1.56 mmol·g −1 ) [10]. Nevertheless, these data compare favorably with published results obtained on a diversity of commercial ACs used for this purpose [10,39,40]. ...
This work presents a first approach concerning the valorization of Tectona Grandis tree by-products, from East Timor through their transformation into high activated carbon (AC) by chemical activation with KOH and K2CO3. The better ACs, Teak-KOH-1-1-700 and Teak-K2CO3-1-2-700, presented a high ABET (995 and 1132 m²·g⁻¹) and micropore volume (0.43 and 0.5 cm³·g⁻¹), respectively. Both ACs were tested on the removal of four pesticides, from the liquid phase. Both ACs performed better than existing commercial types, presenting a maximum adsorption capacity of 1.88, 1.67, 1.10 and 0.89 mmol·g⁻¹, for 4-chloro-2-methylphenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, diuron and atrazine, respectively. Pesticide adsorption from diluted and concentrated solutions confirms that diffusion is the limiting factor. The possibility of implementing a production unit for ACs in East Timor is very promising for that country. It presents an opportunity for job creation, biomass waste reduction and a contribution to environmental sustainability, thereby following the principles of a circular economy.
This work presents some preliminary results on the direct use of untreated biomass from agricultural activities as adsorbents for water treatment. Waste was also used to produce activated carbons (ACs) by chemical activation with KOH. The efficacy of agricultural waste such as stubble, sawdust from Teak (Tectona Grandis), fibers from Imbondeiro (Adansonia digitata L.), bamboo flowers, and other regional plants were tested on methylene blue (MB) removal from the aqueous phase. Adsorption studies were conducted in a batch system and the influence of kinetics, pH, and temperature was evaluated. The adsorption performance of the natural adsorbents was significantly high concerning MB. In particular, Imbondeiro presented a maximum removal capacity of 188.3 mg per gram. This amount was similar to or even higher than the values obtained on ACs produced by their predecessors at 873 K. The studies were finished by constructing slow filters containing natural adsorbents or ACs. The maximum amounts of MB removed on a continuous flux were lower than those obtained for a diversity of untreated biomass types on a batch system. However, these amounts were comparable to the published results obtained on a diversity of untreated biomasses in batch mode.
