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The radial distribution function of K + , HCrO4 − and CrO4 2− ions around activated carbon molecule.
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Adsorption is one of the most successful physicochemical approaches for removing heavy metal contaminants from polluted water. The use of residual biomass for the production of adsorbents has attracted a lot of attention due to its cheap price and environmentally friendly approach. The transformation of Sargassum—an invasive brown macroalga—into ac...
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... property can be calculated from the atomic positions of MD simulation by the analysis of trajectory. The radial distribution function of K + , HCrO4 − and CrO4 2− ions around activated carbon molecule is depicted in Figure 7. Both AC, SAC600 3/1 and SBP10, have comparable adsorption capacities. ...
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... property can be calculated from the atomic positions of MD simulation by the analysis of trajectory. The radial distribution function of K + , HCrO 4 − and CrO 4 2− ions around activated carbon molecule is depicted in Figure 7. The radial distribution functions show sharp peaks at the distance (r) of around 0.2 nm for K + ions from the surface of activated carbon which proves that the K + ions are adsorbed by carboxylate groups of activated carbon. ...
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... property can be calculated from the atomic positions of MD simulation by the analysis of trajectory. The radial distribution function of K + , HCrO4 − and CrO4 2− ions around activated carbon molecule is depicted in Figure 7. In addition, the experimental results showed that the impregnation of activated carbon with Mg 2+ ions prior to the adsorption experiment, improves the adsorption of hexavalent chromium at the surface of AC. ...
Citations
... According to Fig. 8e, the [HCrO 4 ] − oxyanion remains dominant at pH < 4.5 and drops rapidly as pH increases, reaching about 50% at pH 6.5, while the formation of [CrO 4 ] 2− oxyanion starts at pH > 4.5. Studies on removing Cr 6+ generally show greater removal capacities under acidic pH conditions [72]. This behavior has been verified in the removal of Cr 6+ by activated red mud [73], Pinus sylvestris biomass [74], activated rice husk carbon and activated alumina [75], Tamarindus indica seeds [76], residue of alginate extraction from Sargassum filipendula [77], sericin/alginate beads [78], Jute fiber (PANI-Jute) [79], and chitosan Fe° Nanoparticles [80]. ...
... High Cr 6+ removals in the acidic pH range can be associated with its reduction to Cr 3+ since Cr 6+ is a strong oxidant [81]. Equations (6) and (7) present the reduction reactions of Cr 6+ species at low and moderate pH values, respectively [69,72]. a high crosslinking degree in the Hylon VII® hydrogel, which reveals that the increase in amylose content may have promoted more connections between structures in the crosslinking of this starch. ...
This study evaluated the effect of corn starch's amylose/amylopectin content on the development of crosslinked hydrogels with trisodium citrate for the sorption of potentially toxic metals (PTMs). The results, obtained through a robust methodology, indicated a clear relation between the amylose content and crosslinking degree, thereby impacting the properties of the hydrogels. The hydrogel with high amylose (70 wt.%) and low amylopectin (30 wt.%) content (Hylon VII®) demonstrated a high crosslinking degree (0.297) and good thermal stability and water absorption (72.71%), with a semicrystalline structure. The hydrogel with low amylose (1.8 wt.%) and high amylopectin (98.2 wt.%) content (Amisol 4000®), on the other hand, showed the lowest degree of crosslinking (0.109), water absorption (49.77%), and high solubility (46%), which makes its applicability difficult due to its low stability in aqueous media. The influence of amylose (28 wt.%) and amylopectin (72 wt.%) content indicated that the Amisol 3408® hydrogel showed valuable properties, presenting a higher potential for PTMs sorption with the following affinity order: Cu²⁺ (68.62%) > Cd²⁺ (63.13%) > Mn²⁺ (37.36%) > Zn²⁺ (26.61%) > Cr⁶⁺ (16.80%). Besides, the possible sorption mechanism was ion exchange between Cu²⁺/Cd²⁺/Mn²⁺/Zn²⁺ and H⁺ in the hydrogels. Thus, starch-based hydrogel is an alternative sorbent to remove and recover PTMs from wastewater.
... Different treatment methods of the CFX and Cr(VI) residues have been currently utilized such as photocatalysis [18], electrochemical oxidation [14,19], ion exchange [20,21], and adsorption [22,23]. Adsorption has been the most popular method due to its high treatment efficiency [24][25][26]. It is evident that both CFX and Cr(VI) removals through adsorption onto high-activity metal oxide adsorbent have become a new research approach with high potential. ...
In the present study, the MnO2 adsorbents with a crystal structure, the components of approximately 59% Mn and 40% O, and the specific linkages of -OH and O-Mn-O were characterized by the techniques XDR, EDX, and FI-IR, respectively. Especially, the individual and simultaneous adsorptions of chromium, Cr(VI), and an antibiotic, CFX, on the manganese dioxide (MnO2) material were systematically investigated. Compared with the individual adsorption, the CFX adsorption efficiency was significantly reduced in the Cr(VI) presence due to the Cr(VI)-CFX complexation formed by the Cr2O7²⁻ or HCrO4⁻-NH2⁺ electrostatic attractions. The optimal experimental conditions for the Cr(VI)-CFX simultaneous adsorption were found to be pH 6, 1 mM NaCl, 60 min contact time, and 50 mg.mL⁻¹ MnO2 dosage. The maximum adsorption efficiencies of the Cr(VI) and the CFX on the MnO2 were achieved at 98.1 and 87.5%, respectively. The maximum adsorption capacities of the Cr(VI) and CFX were correspondingly extrapolated to be 144.5 and 100.1 mg.g⁻¹ by the Langmuir adsorption model. The Cr(VI)-CFX simultaneous adsorption was adequately described by the Freundlich isotherm and the pseudo-second kinetic models. The chemisorption of Cr(VI)-CFX governed the simultaneous adsorption with the formation of multiple adsorbed layers.
Graphical abstract
... Through their small diameter, activated carbons efficiently bind onto microbes by adsorption to yield better or enhanced bactericidal properties [58,59]. Other features of activated carbons include high porosity, high specific surface area, and desired surface functionalization [56,60]. Although there are almost no standard reported threshold values for antimicrobial nanomaterials to ascertain their degree of activity, it is generally known that the lower the MIC values of the test samples, the greater the antimicrobial activity. ...
Caused by pathogenic microorganisms, infectious diseases are known to cause high
mortality rates, severe burdens of disability, and serious worldwide aftermaths. Drug-resistant
pathogens have reduced the efficacy of available therapies against these diseases, thus accentuating
the need to search for effective antimicrobials. Medicinal plants have served as starting material for
the preparation of a number of antimicrobial agents. To this end, the present study highlights the
green synthesis of Cocos nucifera-based nanomaterials and evaluation of the mechanistic basis of their
antimicrobial action. Accordingly, Cocos nucifera extract was used for the reduction of silver nitrate
solution to afford silver nanoparticles. These entities were further incorporated onto sulfuric-acidbased
activated carbons to generate the nanocomposites. The antimicrobial activity of the as-prepared
nanomaterials was evaluated using the broth microdilution method, while the antioxidant activity
was assessed through standard methods. The cytotoxicity of potent nanomaterials was assessed on
Vero cells by the spectrophotometric method. As a result, nanoparticles were successfully synthesized,
as evidenced by the ultraviolet–visible spectroscopy analysis that revealed an intense absorption
spectrum at 433 nm. Fourier Transform Infrared Spectroscopy presented the functional group moieties
involved as a capping and reducing agent in the synthesis of the nanomaterials. The incubation of
nanomaterials with selected bacterial and fungal strains has led to significant inhibitory effects of these
pathogens with minimum inhibitory concentrations ranging from 7.813 to 250 μg/mL. In antioxidant
assays, the nanocomposites presented scavenging activities comparable to those of ascorbic acid.
Cytotoxicity experiment revealed no toxic effects on Vero cells (range of selectivity indices: from >4 to
>128). These results provide evidence of the implication of Cocos nucifera-based nanomaterials in
targeting bacterial or fungal systems that mediate free-radical damage or by inhibiting the oxidative
damage caused by selected bacteria and fungi, the most susceptible being Escherichia coli and Candida
albicans, respectively.
... exhibits distinctive attributes that render it a highly suitable contender for the elimination of heavy metals. The substance exhibits a notable propensity for heavy metals and can accumulate them through diverse methods, such as biosorption and ion exchange [12]. Moreover, the transformation of biomass derived from Sargassum sp. ...
... Available literature has highlighted the potential of Sargassum activated carbon (SAC) as an adsorbent material, with its positive adsorption capabilities demonstrated in various studies [12,16]. SAC offers several advantages, including its abundant availability, low cost, and environmental friendliness. ...
Sargassum sp., a brown alga in the division of macroalgae was evaluated for its ability to synthesis macroalgal-based activated carbon and remove lead (II) ions from synthetic aqueous solution. The sargassum activated carbon (SAC) was prepared by chemical activation impregnated with zinc chloride followed by carbonization. The surface morphology and functional group of untreated Sargassum sp. powder (SAP) and activated Sargassum sp. carbon (SAC) were scanned and presented with the Scanning Electron Microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR). Batch studies were conducted to explore maximum removal efficiency in term of pH, initial lead (II) ions concentration, contact time, adsorbent dosage, and temperature for the efficient adsorption. The maximum lead (II) ions uptake capacity for SAC was obtained at pH 5, initial lead (II) ions concentration at 25 mg/L, operation time of 60 min, adsorbent dosage of 0.1 g and temperature of 40 °C. The adsorption data were well-fitted by the Freundlich isotherm model, with an R² value of 1.000, indicating a good fit. The kinetic study revealed that the adsorption of lead (II) ions followed a pseudo-first-order kinetic model, with an R² value of 0.9746. This study validates the use of brown algae in the treatment of heavy metal contamination in wastewater.
... Through their small diameter, activated carbons efficiently bind onto microbes by adsorption to yield better or enhanced bactericidal property [49,50]. Other features of activated carbons include high porosity, high specific surface area, and desired surface functionalization [47,51]. Although there is almost no standard reported threshold values for antimicrobial nanomaterials to ascertain their degree of activity, it is generally known that the less is the MIC values of the test samples the more is the antimicrobial activity. ...
Caused by pathogenic microorganisms, such as bacteria, parasites, fungi, among others, infec-tious diseases can spread directly or from one individual to another. According to the World Health Organization, these diseases are known to cause high mortality rates, severe burdens of disability and serious worldwide aftermaths. The inappropriate use of antibiotics in humans are the main origins of the development of drug-resistant pathogens, which reduce the efficacy of these therapies, thus accentuating the need to search for effective antimicrobials. Medicinal plants have served as starting material for the preparation of a number of antimicrobial agents. To this end, the present study highlights the green synthesis of Cocos nucifera-based nanomaterials and evaluation of the mechanistic basis of their antimicrobial action. Accordingly, Cocos nucifera extract was used to reduce different concentrations (5, 10 and 20 mM) of silver nitrate solution to afford silver nanoparticles (AgNPs). These entities were further incorporated onto activated carbons (obtained by chemical activation using sulphuric acid as activation agent) to generate the nano-composites. The antimicrobial activity of the as-prepared nanomaterials was evaluated using the broth microdilution method, while, the antioxidant activity was assessed through standard methods, such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Cytotoxicity of potent na-nomaterials was assessed on Vero cells by spectrophotometric method. As a result, nanoparticles were successfully synthesized as evidenced by the color change of the solution from transparent to dark brown. Further characterization was carried out by UV-visible spectroscopy that showed an intense absorption spectrum at 433 nm. Fourier Transform Infrared Spectroscopy (FTIR) re-vealed the functional group moieties involved as a capping and reducing agent in the synthesis of AgNPs. The incubation of nanomaterials with selected bacterial and fungal strains led to signif-icant inhibitory effects of these pathogens with minimum inhibitory concentrations ranging from 7.813 to 250 μg/ml. In antioxidant assays, the nanocomposites presented scavenging activities comparable to that of ascorbic acid. Cytotoxicity experiment revealed no toxic effects on the human mammalian cells Vero (range of selectivity indices: from >4 to >128). These results provide evidence of the implication of Cocos nucifera-based nanomaterials in targeting bacterial or fungal systems that mediate free-radical damage or by inhibiting the oxidative damage caused by selected bacteria and fungi, the most susceptible being Escherichia coli and Candida albicans, respec-tively.
... In recent years, numerous studies have been conducted in order to obtain ACs from a variety of lowcost materials. Some of these materials include hazelnut shell [25][26][27]; apple shells [28]; bamboo bark [29]; Sargassum [30]; Daniellia oliveri stem bark [31], and Moringa oleifera leaves and bark [32,33]. High carbon agricultural waste materials produce AC and contain lignocellulosic compounds and polar functional groups, making them potential sources for carbon production [34,35]. ...
... Thirty (30) batch adsorption experiments were conducted to study the effect of solution pH (1)(2)(3)(4)(5), contact time (10-90 min), adsorbent dosage (0.020-0.100 gL -1 ), and temperature (25-45°C). Each experiment was carried out in 100 mL Cr(VI) ion solution at a known initial concentration of 1.5 μg/mL. ...
This study investigated the removal of hexavalent chromium Cr(VI) ions in an aqueous solution using Moringa oleifera bark-derived activated carbon (MOBAC). The adsorption removal of Cr(VI) was systematically investigated as a function of four experimental factors: pH (1-5), contact time (10-90 min), adsorbent dosage (0.020-0.100 g L-1), and temperature (25-45°C) by following a statistical experimental design. A response surface methodology (RSM)-based central composite experimental design was used to establish an empirical model that assessed factors' effects on Cr(VI) ions adsorptive removal. The model was verified and validated and used to predict optimal adsorption removal of Cr(VI) from aqueous solutions. At optimized conditions, 99.612 % of 1.5 mg L-1 Cr(VI) ions are removed from the aqueous solution. These optimum condition values include a pH of 2.1, contact time of 62.72 min, adsorbent dosage of 0.065 g L-1, and temperature of 39.8°C. The adsorptive mechanism was assessed by conducting isotherm and kinetic studies. The adsorption process of Cr(VI) ions by MOBAC is described by Langmuir isotherm, indicating monolayer adsorption, and the reaction kinetics is described by pseudo-second order kinetics model. The Langmuir monolayer adsorption capacity of Cr(VI) adsorption on MOBAC was found to be 4.577 mg g-1 for Cr(VI) ions. The findings support the use of MOBAC in the removal of Cr(VI) ions from aqueous systems.
... As the solution pH increases, the net charge of the CCs-AC surface becomes negative, while Cr(VI) is still in negative form. Thus, the adsorption efficiency will gradually decrease due to electrostatic repulsions [24,25]. ...
This study evaluated the performance of a new activated carbon (CCs-AC) produced from corn cobs by boric acid activation for the effective removal of hexavalent chromium, a heavy metal with high potential to pollute the environment, from wastewater. For this purpose, with the help of parameters such as solution pH, contact time, initial Cr(VI) concentration, CCs-AC dose, desorption and temperature, the removal of Cr(VI) ions from aqueous solution by adsorption on CCs-AC was investigated from equilibrium, kinetic and thermodynamic point of view. As a result of the experiments, it was determined that the optimum solution pH was 2.0, the contact time was 4 hours, and the desorption solution was 3.0 M NaOH. From the kinetic data, it was determined that the adsorption was compatible with the pseudo-second order kinetic model and the maximum Cr(VI) adsorption capacity (123.7 mg/g) obtained from the Langmuir isotherm model showed that CCs-AC was of competitive quality with the literature. From the thermodynamic data, the positive ΔH value indicates that the adsorption is endothermic and the value of 12.00 kj/mol indicates that the adsorption is rather chemically driven. The negative ΔG value indicates that the process proceeds spontaneously with an increase in temperature, while the ΔS value indicates an increase in the amount of unused energy.
The possibility of using three types of NaOH-treated tea residues (green tea, pu-erh, and tieguanyin) as low-cost adsorbents for Cr(VI) treatment was investigated. The surface charge, composition, morphology, structure, and functional groups in the obtained biosorbents were characterized by pHzpc, cellulose content, SEM, BET, XRD, and FTIR spectroscopy. The nonlinear pseudo-first-order, pseudo-second-order, and Elovich models were used to investigate adsorption kinetics at various initial concentrations. The adsorption processes were more consistent with the pseudo-second-order kinetic model in the range of 5-50 mg L-1. The adsorption isotherm at 298 K was described using the nonlinear Langmuir, Freundlich, Temkin-Pyzhev, and Dubinin-Radushkevich models, indicating that the process was favorable and complex with maximum adsorption amounts of 6.15, 19.50, and 12.31 mg g-1 for green tea, pu-erh, and tieguanyin residues, respectively. Thermodynamic analysis revealed that the adsorption was a spontaneous, endothermic process. The results demonstrated that all materials had the potential to successfully remove Cr(VI) from the aqueous solution.
