Figure 2 - uploaded by Luiz Eduardo Nochi Castro
Content may be subject to copyright.
(a) Determination of the point charge zero (PZC) of the coffee husk and the synthesized adsorbents, with phosphoric acid (H3PO4) and with zinc chloride (ZnCl2); (b) Isotherms of adsorption (A) and desorption (D) of nitrogen (N2) from the coffee husk and the synthesized adsorbents H3PO4 and ZnCl2; (c) Ponceau 4R dye removal percentage in preliminary adsorption assays with synthesized adsorbents H3PO4 and ZnCl2.
Contexts in source publication
Context 1
... adsorbents were characterized by PZC, SEM and N2 adsorption/desorption measurements. In the case of the PZC results, it can be seen in Figure 2a that the pHPZC values of the coffee husk (pHPZC = 6.60) and the ZnCl2 adsorbent (pHPZC = 6.12) were higher than the pHPZC = 5.6 value, referring to the solution of Ponceau 4R dye. Thus, the surface of the adsorbents (coffee husk and ZnCl2) is negatively charged, and this causes cations to be adsorbed on the material surface to balance the negative charges. ...
Context 2
... for the H3PO4 adsorbent (pHPZC = 2.75), the pH is below the pHPZC of the dye, so the surface of the adsorbent is positively charged, which leads to the attraction of negatively charged charged species, it is known that dye molecules present free electrons in their structure, so there is a tendency to have a negative charge, contributing to the adsorption process [30]. Based on the study of N2 physisorption for the studied materials it was possible to observe that the isotherms (Figure 2b) for the ZnCl2 adsorbents and coffee husks were similar to type II isotherms, typical of non-porous or macroporous materials, while the H3PO4 adsorbent isotherms were similar to type I isotherms, typical of microporous materials (dp < 20 Å) [43,44]. ...
Context 3
... the surface of the material chemically treated with H3PO4 (Figure 3b) showed a high pore distribution over the entire surface, an important factor in the adsorption process, since the adsorbate molecules find suitable sites to be adsorbed, a behavior similar to that found for porous materials in the literature [4,43,45]. In addition, the adsorbent treated with H3PO4 had the largest surface area around 430 m 2 g -1 in relation to the other materials and it had the lowest pore diameter value (11.4 Å) according to Figure 3d, which corroborates with its isotherm (Figure 2b), characterizing the material as microporous. The combination of high surface area and micropore diameter reveals the characteristics of adsorbent materials in relation to their effectiveness [43,46,47]. ...
Context 4
... to the results from micrographs and analyzes of N2 physisorption, it was observed that the structure of the adsorbent treated with phosphoric acid would be conducive to the removal of the Ponceau 4R dye, since the structure of the material is highly porous with a high area superficial. Thus, preliminary assays were carried out to evaluate the percentage of dye removal by the materials H3PO4 and ZnCl2, according to Figure 2c. It can be seen that the adsorbent treated with H3PO4 promoted removal of approximately 100 % of the dye, while the adsorbent ZnCl2 managed to remove only around 50 %. ...
Context 5
... difference in the removal of the Ponceau 4R dye by the different adsorbents observed in Figure 2c), can be explained by the characterization analysis of the materials. Through the PZC analysis, it was possible to observe that the H3PO4 adsorbent has its surface positively charged, which makes it suitable for the adsorption of anionic molecules, such as the Ponceau 4R dye molecules. ...
Context 6
... adsorbents were characterized by PZC, SEM and N2 adsorption/desorption measurements. In the case of the PZC results, it can be seen in Figure 2a that the pHPZC values of the coffee husk (pHPZC = 6.60) and the ZnCl2 adsorbent (pHPZC = 6.12) were higher than the pHPZC = 5.6 value, referring to the solution of Ponceau 4R dye. Thus, the surface of the adsorbents (coffee husk and ZnCl2) is negatively charged, and this causes cations to be adsorbed on the material surface to balance the negative charges. ...
Context 7
... for the H3PO4 adsorbent (pHPZC = 2.75), the pH is below the pHPZC of the dye, so the surface of the adsorbent is positively charged, which leads to the attraction of negatively charged charged species, it is known that dye molecules present free electrons in their structure, so there is a tendency to have a negative charge, contributing to the adsorption process [30]. Based on the study of N2 physisorption for the studied materials it was possible to observe that the isotherms (Figure 2b) for the ZnCl2 adsorbents and coffee husks were similar to type II isotherms, typical of non-porous or macroporous materials, while the H3PO4 adsorbent isotherms were similar to type I isotherms, typical of microporous materials (dp < 20 Å) [43,44]. ...
Context 8
... the surface of the material chemically treated with H3PO4 (Figure 3b) showed a high pore distribution over the entire surface, an important factor in the adsorption process, since the adsorbate molecules find suitable sites to be adsorbed, a behavior similar to that found for porous materials in the literature [4,43,45]. In addition, the adsorbent treated with H3PO4 had the largest surface area around 430 m 2 g -1 in relation to the other materials and it had the lowest pore diameter value (11.4 Å) according to Figure 3d, which corroborates with its isotherm (Figure 2b), characterizing the material as microporous. The combination of high surface area and micropore diameter reveals the characteristics of adsorbent materials in relation to their effectiveness [43,46,47]. ...
Context 9
... to the results from micrographs and analyzes of N2 physisorption, it was observed that the structure of the adsorbent treated with phosphoric acid would be conducive to the removal of the Ponceau 4R dye, since the structure of the material is highly porous with a high area superficial. Thus, preliminary assays were carried out to evaluate the percentage of dye removal by the materials H3PO4 and ZnCl2, according to Figure 2c. It can be seen that the adsorbent treated with H3PO4 promoted removal of approximately 100 % of the dye, while the adsorbent ZnCl2 managed to remove only around 50 %. ...
Context 10
... difference in the removal of the Ponceau 4R dye by the different adsorbents observed in Figure 2c), can be explained by the characterization analysis of the materials. Through the PZC analysis, it was possible to observe that the H3PO4 adsorbent has its surface positively charged, which makes it suitable for the adsorption of anionic molecules, such as the Ponceau 4R dye molecules. ...
Citations
... For instance, from banana peel, obtained activated carbon with a surface area over 2000 m 2 g −1 and a yield higher than 35%. Highlighting the significance of method selection, it is crucial to consider factors such as the time required for synthesis, the nature and potential harm of the reagents, the properties of the resulting material, and, most importantly, the level of complexity and the equipment needed [18][19][20]. ...
... This study employed a one-step acid activation procedure using H 3 PO 4 [18]. In this process, 20 g BSG were combined with 20 g H 3 PO 4 solution (85% w/v). ...
... The theoretical amount of lactose, BOD 5 , and COD adsorbed at equilibrium (q e ) was determined using four kinetic models: pseudo-first-order (PFO), pseudo-second-order (PSO), and Avrami fractional-order (AFO) [18,[36][37][38]. These values were then compared with the experimental values obtained for the parameters adsorbed at equilibrium (q eExp ). ...
Brewer’s spent grains (BSG) are a significant by-product of beer production, and its improper disposal poses environmental challenges. This study investigated the use of BSG for activated carbon production with phosphoric acid as a chemical activator and its application in cheese whey remediation through liquid-phase adsorption. The adsorbent was thoroughly characterized through using techniques such as FTIR, SEM, N2 isotherms, and surface charge distribution. The adsorbent exhibited substantial pores, a high surface area (605.1 m2 g–1), good porosity, and positive surface charges that facilitated favorable interactions with cheese whey compounds. Equilibrium was achieved in 330 min for lactose, BOD5, and COD. The maximum adsorption capacities were 12.77 g g–1 for lactose, 3940.99 mg O2 g–1 for BOD5, and 12,857.92 mg O2 g−1 for COD at 318 K. Removing these adsorbates from cheese whey effluent reduces its organic load, enabling water reuse in the manufacturing unit, depending on its intended use. The adsorption process was spontaneous and endothermic, with ΔH° ≥ 265.72 kJ mol−1. Additionally, the activated carbon produced demonstrated impressive regeneration capability with sodium hydroxide, maintaining 75% of its adsorption capacity. These results emphasize the potential of activated carbon as an effective adsorbent for cheese whey remediation, providing a sustainable solution for waste management in the dairy industry and water reuse.
... These materials have chemical and structural properties that may favor the removal of highly toxic organic components. 35,36 Silica-based adsorbents are widely used for cleaning aqueous solutions in solid-phase extraction. 37 Silica modified with octadecyl groups improves the material's polarity in the extraction and separation of polar components. ...
During the process of subcritical water hydrolysis of lignocellulosic compounds, such as brewers’ spent grains, some toxic compounds can be formed due to the breakdown of the cellulose structure. These compounds are known as furanic aldehydes, and they are inhibitors of microorganisms that are used in different processes, such as fermentation and anaerobic digestion, among others. The detoxification and conditioning of these hydrolysates are required before their use in other processes that require low concentrations of toxins. One of the mechanisms that can be used to diminish those compounds is the adsorption process. Because of this, this study evaluated at‐line and in‐line purification strategies using different adsorbents in fixed‐bed columns to remove furanic aldehydes from a model feed simulating hydrolysate from subcritical water hydrolysis. The model feed consisted of simple sugars and furanic aldehydes at appropriate concentrations. The selected adsorbents were silica‐C18, hydrocarbons, and activated carbon. The results indicate that among the studied adsorbents, activated carbon was the most efficient for the removal of both 5‐hydroxymethyl furfural and furfural. The activated carbon removed >99% of furanic aldehydes in the experiments conducted in the at‐line system. Sequential subcritical water hydrolysis followed by either at‐line or in‐line purification has promise for integrated inexpensive and efficient hydrolysate purification.
Recently, the development of techniques to produce detoxified biocompounds has attracted much research interest. This study reviews adsorbents for application in the purification and detoxification of biocompounds, aiming to identify the field's knowledge gaps, trends, updates and hotspots. This review focuses on the description of the types of adsorbents (activated carbon, zeolites, clays, clay minerals and biosorbents) and their activation methods (chemical and physical) for laboratory and industrial adsorption. The adsorbents that stand out are activated carbon and chitosan‐based adsorbents. Moreover, there is a research trend toward using adsorbents to purify bioactive compounds, sugars and amino acids. Finally, adsorbents underscore a growing global research interest in exploring effective treatments for removing various combinations.
