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Adsorption of 2,4-dichlorophenoxyacetic acid (2,4D) on sargassum activated carbon
Abstract
The production of activated carbon was carried out by impregnating the sargassum with a 85% H3PO4 solution in a mass ratio of 1/3 sargassum/ H3PO4, with an impregnation time of 15 hours. The production of activated carbon from sargassum was carried out in a pyrolytic muffle furnace with a controlled nitrogen atmosphere. Sargassum samples were collected on the beaches of the Dominican Republic. Sargassum activated carbon has a specific surface area of 754 m2/g and the 2,4-D adsorption was pH dependent.
This study aims (i) to use Sargassum (sp) for producing activated carbon applied for the removal of caffeine from water (ii) to understand the associated adsorption mechanism by exploring interactions between the micropollutant and acidic groups of AC surface using molecular modeling. The AC preparation was carried out using H3PO4 as an activating agent and the impregnated precursor was pyrolyzed under N2 atmosphere. The AC characterization was performed using N2 adsorption-desorption isotherms, FTIR spectroscopy, X-ray photoelectron spectroscopy, Boehm titration and pHpzc methods. The best adsorption was observed under the following experimental conditions: solution pH 6.0, optimal residence time of 90 min, adsorbate concentration equal to 5 000 mg/L. Adsorption equilibrium was evaluated from the adsorption isotherms at 25 °C, for a maximum adsorption capacity equal to 221.61 mg/g. The mechanism of caffeine adsorption on AC surface was studied using both experimental and molecular modelling approach. This preliminary work on these algae, opens up interesting prospects to produce AC from Sargassum (sp) for water treatment.
Au/TiO 2-CeO 2 photocatalysts were studied in the photodegradation of the 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous medium under UV light emission source. The TiO 2-CeO 2 supports (2.5-10 wt.% CeO 2) were prepared by the sol-gel method using titanium alkoxide and cerium nitrate as starting precursors. Gold nanoparticles were prepared by the deposition-precipitation method with urea and deposed on the supports to obtain Au/TiO 2-CeO 2 photocatalysts. The BET area increases as function of the CeO 2 content from 64 m 2 /g for the bare TiO 2 solid to 71-137 m 2 /g for the TiO 2-CeO 2 mixed oxides. TEM and HRTEM images showed Au nanoparticles ranking from 8.1 to 3.4 nm. Additionally well defined gold plas-mon and a red shift in the E g band gap energy (3.14-2.47 eV) was observed by UV-vis spectroscopy on the mixed oxides. For the photodegradation of 2,4-D it has been observed an important effect of cerium oxide in the photoactivity, it varies from 78 to 99% of 2,4-D conversion and from 61 to 88% of total organic carbon conversion for the Au/TiO 2 and Au/TiO 2-CeO 2 photocatalysts respectively. A synergetic effect where gold plays the role of electrons tramp and the cerium oxide the role of oxidizing agent is proposed.
Recently, removal of trace hazardous organic contaminants in the water is still a challenge work and attracting a growing number of concerning. Herein, a photo-responsive cellulose based intelligent imprinted material (PR-Cell-MIP) was fabricated through SI-ATRP (surface-initiates atom transfer radical polymerization) and employed for the selective adsorption of a typical pesticide residue, 2,4-dichlorophenoxyacetic acid (2,4-D). The characterization results showed that the obtained PR-Cell-MIP displayed 2-D petal-like laminar sheet and owned ample functional groups such as N=N, COCl and –COOH. The photo-responsive tests confirmed the excellent photo-isomerization property of PR-Cell-MIP, leading to a satisfactory regeneration during the 2,4-D adsorption. Batch adsorption experiments demonstrated that the 2,4-D adsorption followed Frendlich adsorption isotherm. Meanwhile, the higher equilibrium template bindings (89.03%), lower specific binding constant KD (11.601 mg L⁻¹) and apparent maximum number Qmax (11.039 mg g⁻¹) suggested much higher adsorption performance of PR-Cell-MIP than that of the non-imprinted polymer (PR-Cell-NIP). The selectivity experiments revealed that PR-Cell-MIP presented better specificity towards 2,4-D than its structural analogues. In addition, the PR-Cell-MIP also displayed outstanding stability, reusability (8 cycles) and green regeneration. Furthermore, the selective adsorption and green regeneration were attributed to the exposure and blockage of specific recognition sites, allowing the precise and reversible switching of the host-guest interaction between receptor sites and 2,4-D. These findings will provides a fundamentally technical basis for the remediation of the trace hazardous pollutants.
This research demonstrates the production of mesoporous activated carbon from sargassum fusiforme via physical activation with carbon dioxide. Central composite design was applied to conduct the experiments at different levels by altering three operating parameters. Activation temperature (766–934 °C), CO2 flow rate (0.8–2.8 L ⋅ min⁻¹) and activation time (5-55 min) were the variables examined in this study. The effect of parameters on the specific surface area, total pore volume and burn-out rate of activated carbon was studied, and the influential parameters of methylene blue adsorption value were identified employing analysis of variance. The optimum conditions for maximum methylene blue adsorption value were: activation temperature = 900 °C, activation time = 29.05 min and CO2 flow rate = 1.8 L ⋅ min⁻¹. The activated carbon produced under optimum conditions was characterized by BET, FTIR and SEM. The adsorption behavior on congo red was studied. The effect of parameters on the adsorbent dosage, temperature, PH and initial congo red concentration was investigated. The adsorption properties of the activated carbon was investigated by kinetics. The equilibrium removal rate and maximum adsorption capacity reaches up to 94.72%, 234 mg/g, respectively when initial congo red concentration is 200 mg ⋅ L⁻¹ under adsorbent dosage (0.8 g ⋅ L⁻¹), temperature (30 °C), PH7.
A novel polymer/activated carbon composite was prepared in this study by one-step chemical activation of Sargassum horneri, followed by surface modification with chitosan, a widely abundant biopolymer. The prepared composite was used as adsorbent to remove one of the most toxic metal ions, Cr(VI), from aqueous solution. Surface characterization tests revealed the material to be predominantly mesoporous with the specific surface area of 293.4 m²·g⁻¹ and the average pore diameter of 6.27 nm. Enhanced uptake capacity of Cr(VI) by the prepared composite was obtained due to the presence of more metal-binding functional (amino and hydroxyl) groups on its surface. Extremely fast adsorption rate of Cr(VI) was also achieved due to the porous structure of the prepared composite. This study has clearly shown that Sargassum horneri can be a potential alternative precursor for carbon-based adsorbents and the proper designed polymer/AC composites can be tailor-made adsorbents for heavy metal removal.
Background: Advanced Hybrid Oxidation Processes(AHOPs) have the ability to romove the
pesticides. The aim of this study was optimization of sono-electroperoxone process (US-EP) in the removl of 2.4 D from aqueous via RSM.
Methods: The pilot that used to in this study included an ozone generator, an ultrasonic generator and an electric direct current source. Two graphene electrodes as anodes and two titanium electrodes as cathodes were used. This electrodes connected to DC as direct monopolar connection. pH, direct electric current, ozone gas concentration, reaction time and initial 2,4 D concentration were optimized as an independet and inffluence parameters. COD and TOC removal, kinetics of reaction, synergyist effects of variables, presence of radical scavangers and optimal electrolyte concentration were
determined in optimum condition.
Results: Efficiency of process was 55-90 percent in different runs. The optimized conditions are modeled was pH=6/04, ozone concentration equal to 2 mg/L.min, electric current equal to 1 amperes, 2, 4 D concentration equal to 30.3 mg/L and in 103 minutes reaction time in the presence of ultrasonic waves with frequencies 40 kHz. The Efficiency of US-EP in this situation was 95 percent. COD and TOC removal were 71% and 63%, respectively. The kinetics of the process follow the first order kinetics. The P-Value and F-value was determined by ANOVA analysis 0.0033 and 24.19 respectively, which indicates the model is significant. R2, R2 adj and R2 predicted were 0.94, 0.84 and
0.89, respectively.
Conclusion: US-EP process had a high performance in removing of 2.4 D. The process is an environmentally friendly process because don’t use of chemicals.
The adsorption of Diphenolic acid (DPA), 2,4-Dichlorophenoxyacetic acid (2,4-D), and 2-methyl-4-chlorophenoxyacetic acid (MCPA) were examined in aqueous solution using activated carbon rice straw. The rice straw was activated by using two reagents, zinc chloride and phosphoric acid and named as RSZ, RSP, respectively. The results showed that both carbons have a relatively high adsorption capacity. Concerning the adsorption kinetic, the second-order model has better fit than the first model to experimental data. The adsorption yield of both carbons increased in the order: DPA < 2,4-D < MCPA. The pore volume diffusion model satisfactorily fitted the experiment on both carbons. Furthermore, solution pH has a high influence on the adsorption capacity for both carbons. The adsorption mechanism of selected pollutants onto carbon samples has been controlled by dispersion interaction π-π electrons and electrostatic interaction, moreover, the contribution of pore volume diffusion is the controlling mechanism of the overall rate of adsorption.
The article presents the behavior of phenoxy acids in water, the levels in aquatic ecosystems, and their transformations in the water environment. Phenoxy acids are highly soluble in water and weakly absorbed in soil. These highly mobile compounds are readily transported to surface and groundwater. Monitoring studies conducted in Europe and in other parts of the world indicate that the predominant phenoxy acids in the aquatic environment are mecoprop, 4-chloro-2-methylphenoxyacetic acid (MCPA), dichlorprop, 2,4-dichlorophenoxyacetic acid (2,4-D), and their metabolites which are chlorophenol derivatives. In water, the concentrations of phenoxy acids are effectively lowered by hydrolysis, biodegradation, and photodegradation, and a key role is played by microbial decomposition. This process is determined by the qualitative and quantitative composition of microorganisms, oxygen levels in water, and the properties and concentrations of phenoxy acids. In shallow and highly insolated waters, phenoxy acids can be decomposed mainly by photodegradation whose efficiency is determined by the form of the degraded compound. Numerous studies are underway on the use of advanced oxidation processes (AOPs) to remove phenoxy acids. The efficiency of phenoxy acid degradation using AOPs varies depending on the choice of oxidizing system and the conditions optimizing the oxidation process. Most often, methods combining UV radiation with other reagents are used to oxidize phenoxy acids. It has been found that this solution is more effective compared with the oxidation process carried out using only UV.
As release formulations, superabsorbent polymers have attracted considerable attentions to reduce herbicide leaching and mitigate contamination. For this purpose, this study dealt with preparation, characterization, and performance test of a novel amphoteric superabsorbent polymer in adsorption and release of 2, 4‐Dichlorophenoxyacetic acid (2, 4‐D) herbicide. LW‐g‐p(AA‐co‐DMDAAC) was successfully synthesized by using leather waste (LW) as raw material and acrylic acid (AA), and dimethyldiallylammonium chloride (DMDAAC) as monomers. Then, the resulting LW‐g‐p(AA‐co‐DMDAAC) was characterized before and after 2, 4‐D sorption by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). In addition, LW‐g‐p(AA‐co‐DMDAAC) with great equilibrium swelling capacity of 3203 g/g in distilled water, 181 g/g in 0.9 wt % NaCl exhibited excellent performance of swelling. Two absorption peaks appeared at pH = 4 and 7 solely when swelling occurred, and the swelling behavior in pH = 7 satisfied the pseudo first‐order kinetic equation. Moreover, the sorbed 2, 4‐D reached at 68 mg/g and showed sustained release cycle of 45 days under acidic or alkaline conditions. Therefore, the sustained release pattern of 2, 4‐D as well as water absorbency made LW‐g‐p(AA‐co‐DMDAAC) suitable and potential candidate for controlling the release of herbicides to improve utilization and reduce environmental pollution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48480.
In this dataset, the removal of ammonia from synthetic and real wastewater was studied using the Ziziphus spina-christi activated carbon (ZSAC) and the biochar of Sargassum oligocystum (BSO). Several analyses such as FTIR, SEM, EDS, XRD, and BET were used to determine the physical and surface properties of the adsorbents. The BET analysis showed a high specific surface area of 112.5 and 45.8 m2/g for ZSAC and BSO, respectively. Also, the results indicated that the highest adsorption of ammonia from synthetic wastewater using ZSAC and BSO were obtained 97.9% and 96.2%, at contact time of 80 min, 25 °C, pH 8, and adsorbent dosage of 5 g/L. In addition, the adsorption results of real wastewater from Asaluyeh Pardis Petrochemical Company demonstrated that both adsorbents had the removal efficiency of approximately 90%, which indicates high adsorption efficiency using two adsorbents. Moreover, equilibrium studies showed that the adsorption process of ammonia from wastewater using both adsorbents follows the Freundlich model and the maximum adsorption capacity using the Langmuir isotherm were calculated to be 25.77 mg/g and 7.46 mg/g for ZSAC and BSO, respectively. Furthermore, the thermodynamic study showed that the adsorption process using the bio-adsorbents was spontaneous and exothermic.
High-performance microporous activated carbon (AHC) for CO 2 capture was prepared from an emerging marine pollutant, Sargassum horneri , via hydrothermal carbonization (HTC) and KOH activation. The as-synthesized carbon material was characterized by N 2 sorption-desorption measurement, TGA, SEM, XRD, FTIR, and elemental analysis. Impressively, the activated carbon exhibited high specific surface area (1221 m ² /g), narrow distributed micropores (∼0.50 nm), and a relatively high nitrogen content (3.56 wt.%), which endowed this carbon material high CO 2 uptake of 101.7 mg/g at 30°C and 1 bar. Moreover, the carbon material showed highly stable CO 2 adsorption capacity and easy regeneration over four adsorption-desorption cycles. Two kinetic models were employed in this work and found that the pseudo-first-order kinetic model ( R² = 0.99) provided the best description. In addition, the high CO 2 uptake is mainly attributed to the presence of abundant narrow microporous. The macroporous structure of hydrochar (HC) played an important role in the production of microporous carbon with high adsorption properties. This work provides an efficient strategy for preparing microporous activated carbon from Sargassum horneri , and AHC is a promising candidate acting as an efficient CO 2 adsorbent for further industrial application.
From mid-2014 until the end of 2015, the Mexican Caribbean coast experienced a massive influx of drifting Sargassum spp. that accumulated on the shores, resulting in build-up of decaying beach-cast material and near-shore murky brown waters (Sargassum-brown-tides, Sbt). The effects of Sbt on four near-shore waters included reduction in light, oxygen (hypoxia or anoxia) and pH. The monthly influx of nitrogen, and phosphorus by drifting Sargassum spp. was estimated at 6150 and 61 kg km− 1 respectively, resulting in eutrophication. Near-shore seagrass meadows dominated by Thalassia testudinum were replaced by a community dominated by calcareous rhizophytic algae and drifting algae and/or epiphytes, resulting in 61.6–99.5% loss of below-ground biomass. Near-shore corals suffered total or partial mortality. Recovery of affected seagrass meadows may take years or even decades, or changes could be permanent if massive influxes of Sargassum spp. recur.
In recent years there have been massive inundations of pelagic Sargassum known as golden-tides on the beaches of the Caribbean, Gulf of Mexico and West Africa causing considerable damage to the local economy and environment. Commercial exploration of this biomass for food, fuel and pharmaceutical products could fund clean-up and offset the economic impact of these Golden-tides. This paper reviews the potential uses and obstacles for exploitation of pelagic Sargassum.
Although, Sargassum has considerable potential as a source of biochemicals, feed, food, fertiliser and fuel, variable and undefined composition together with the possible presence of marine pollutants may make golden-tides unsuitable for food, nutraceuticals and pharmaceuticals and limit its use in feed and fertilisers.
Discontinuous and unreliable supply of Sargassum, also presents considerable challenges. Low cost methods of preservation such as solar drying and ensiling may address the problem of discontinuity. The use of processes that can handle a variety of biological and waste feedstocks in addition to Sargassum is a solution to unreliable supply, and anaerobic digestion for the production of biogas is one such process.
More research is need to characterise golden-tides and identify and develop commercial products and processes.
Among the several synthetic herbicides available currently, 2,4-D is a commonly used herbicide to control broadleaf weeds in agriculture and forestry. However, its increasing use in agricultural and nonagricultural activities has resulted in increasing concentrations of 2,4-D being detected in water bodies. Thus, there is a need to identify methods to remove 2,4-D to protect the environment. Among the various methods used for 2,4-D removal, adsorption is found to be effective, and several adsorbents have been studied to remove 2,4-D from aqueous solutions. In this study, we used bagasse fly ash (BFA), a common industrial waste generated in large amount worldwide, for 2,4-D removal from aqueous solution using batch and continuous packed-bed adsorption. In the batch adsorption process, the effects of initial concentration, contact time, temperature, pH, and particle size of BFA were studied. The packed-bed performance of BFA was investigated by varying the influent concentration (50–150 mg/L), flow rate (1.2–4 mL/min), and bed height (4.5–9 cm). Isotherm and thermodynamic parameters are determined for batch adsorption, whereas the performance of continuous adsorption is evaluated by different packed-bed models. The particle-size effect indicated the higher removal of 2,4-D on the bigger particles of BFA due to greater BET surface area and carbon-to-silica ratio than smaller particles. The maximum percentage removal (37.04) is achieved for an influent concentration of 50 mg/L, flow rate of 1.2 mL/min, and bed height of 6.5 cm. For the first time ever, the deactivation kinetic model was applied for the solid–liquid adsorption system and it showed the best fit among the selected models. The bed capacity (m2/g) of BFA is three times greater than synthetic activated carbon for adsorption of 2,4-D. This informs that the BFA can be used as an adsorbent for 2,4-D removal from aqueous solution.
RESUMEN Sargassum fluitans y Sargassum natans son macroalgas pardas holopelágicas que se pueden agregar para formar extensas masas flotantes en la superficie del Atlántico Norte (Mar de los Sargazos). El presente trabajo describe la ocurrencia de una excesiva arribazón de Sargassum fluitans en la costa este de la provincia de Cienfuegos, región centro-sur de Cuba, en mayo de 2012. El mayor impacto de la arribazón por efecto mecánico sobre la costa fue reportado en el sector turístico. Se observaron condiciones meteorológicas atípicas durante la arribazón de Sargassum. ABSTRACT Sargassum fluitans y Sargassum natans are holopelagic brown macroalgae that can aggregate to form extensive floating mats on the surface of North Atlantic (Sargasso Sea). The present paper describes the occurrence of an excessive drift of Sargassum fluitans in the East coast of Cienfuegos province, central-southern region of Cuba, in May of 2012. Most impact of the drift by mechanic effect on the coast was reported in the touristic sector. Atypical meteorological conditions were observed during the Sargassum drift.
We report an unusual biomass of floating Sargassum, composed of the species S. fluitans and S. natans, that reached the northeastern coast of San Andres island in September 2014. The time and size of the event is unprecedented to the island.Cantidades masivas de Sargassum pelágicos en las costas de San Andrés Isla, Caribe suroccidentalSe reporta la llegada de una biomasa inusual de Sargassum flotante, compuesta por las especies S. fluitans y S. natans, a la costa nororiental de la isla de San Andrés. La época y el tamaño del evento nunca habían sido reportados anteriormente para la isla.
Activated carbon (AC) is employed in drinking water purification without almost any knowledge about the adsorption mechanism of persistent organic pollutants (POPs) onto it. Hexachlorocyclohexane (HCH) is an organochlorinated contaminant present in water and soils of banana crops production zones of the Caribbean. The most relevant isomers of HCH are γ-HCH and β-HCH, both with great environmental persistence. A theoretical study of the influence of AC surface groups (SGs) on HCH adsorption is done in order to help to understand the process and may lead to improve the AC selection process. A simplified AC model consisting of naphthalene with a functional group was used to assess the influence of SGs over the adsorption process. The Multiple Minima Hypersurface (MMH) methodology was employed to study γ-HCH and β-HCH interactions with different AC SGs (hydroxyl and carboxyl) under different hydration and pH conditions. The results obtained showed that association of HCH with SGs preferentially occurs between the axial protons of HCH and SG’s oxygen atom, and the most favourable interactions occurring with charged SGs. An increase in carboxylic SGs content is proposed to enhance HCH adsorption onto AC under neutral pH conditions. Finally, this work presents an inexpensive computer aided methodology for preselecting activated carbon SGs content for the removal of a given compound.
The degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been studied by electro-oxidation (EOx) and electro-Fenton/BDD (EF/BDD) using a 3-L pre-pilot plant with a BDD/BDD cell of 64 cm2 of electrode area. Electrolyses were performed with 60 mg L−1 2,4-D in 0.05 M Na2SO4 at pH 3.0, current densities between 7.8 and 31 mA cm−2, and liquid flow rates between 4 and 10 L min−1. In these electrochemical advanced oxidation processes, the main oxidants are hydroxyl radicals (•OH) formed from water oxidation at the BDD anode and/or from Fenton’s reaction between added Fe2+ and H2O2 generated at the BDD cathode. The EOx treatment at 31 mA cm−2 yielded 70 % mineralization as maximal at 160 min, which decreased at lower liquid flow rate because it was limited by the mass transport of organics toward the anode. Faster degradation was found for EF/BDD with 0.7 mM Fe2+, leading to 81–83 % of mineralization in 120 min. High current efficiency was determined at the beginning of this process, and the lowest energy cost of 95 kWh kg−1 TOC (2.0 kWh m−3) was obtained at 7.8 mA cm−2. 2,4-D was rapidly removed by EF/BDD. Four chloroaromatic products (2,4-dichlorophenol, 4,6-dichlororesorcinol, chlorohydroquinone, and chloro-p-benzoquinone) and three hydroxylated derivatives were detected by liquid chromatography–mass spectrometry, whereas hydroquinone and p-benzoquinone were identified by reversed-phase HPLC. A reaction sequence for the degradation of 2,4-D by EOx and EF/BDD involving all detected aromatics is proposed.
This study explores the feasibility of pumpkin seed hull as a potential raw precursor for preparation of mesoporous activated carbon by microwave induced KOH activation. The pumpkin seed hull activated carbon (PSHAC) was characterized by pore structural analysis, zero-point-of-charge, Fourier transform infra-red spectroscopy and scanning electron microscopy. The adsorptive performance of PSHAC was quantified using pesticide, 2,4-dichlorophenoxyacetic acid (2,4-D) as model adsorbate. The effects of contact time, initial concentration, and solution pH on the adsorption process were evaluated. Results indicated high percent of removal, with the adsorptive removal of 98.28%, 97.57%, 96.03%, 93.40%, 78.11% and 65.07% at the initial concentration 50, 100, 150, 200, 300 and 400 mg/L, respectively. Kinetic studies showed that the adsorption process was well described by the pseudo-second-order kinetic model. The adsorption isotherm was analyzed using the nonlinear Langmuir, Freundlich and Temkin isotherm models. The best fit was obtained with the Temkin isotherm model, predicting a uniform distribution of binding energy over the heterogeneous surface binding sites. The maximum monolayer adsorption capacity of 2,4-D for PSHAC was identified to be 260.79 mg/g.
Las arribazones algales consisten en la llegada a las playas o a las riberas de lagunas costeras y estuarios de grandes cantidades de macroalgas sensu lato, es decir, pertenecientes a cualquiera de los phyla Chlorophyta (algas verdes), Ochrophyta (algas pardas) o Rhodophyta (algas rojas).
In recent years pelagic Sargassum has invaded the coastlines of the Caribbean region, Gulf of Mexico, Florida and West Africa, triggering human health concerns and negatively impacting environmental and economic productivity. Sargassaceae are nutrient-dense and currently utilized as fertiliser and food, while extracts of their phytochemicals exhibit unique biosorption and medicinal properties. This macroalgae also shows biofuel potential but hitherto, methane recovery is low due to a carbon to nitrogen ratio below 20:1, the restricted bioavailability of structurally complex carbohydrates for degradation and high insoluble fibre, salt, polyphenol and sulfur content. To optimise the microbial bioconversion of this biomass, pre-treatment and co-fermentation with other substrates have been explored. This paper reviews the challenges associated with, and potential solutions for, Sargassum inundation, and provides a critical evaluation of its bioconversion to biogas and fertiliser using anaerobic digestion technology. As the Caribbean region is primarily impacted by drifting Sargassum blooms, the paper concludes with a case study on Barbados and investigates the feasibility of repurposing this brown macroalgae from landfill disposal to a feedstock for electricity and fertiliser production. The results of this study indicate that Sargassum mono-digestion is unsustainable for energy extraction given its low bioconversion efficiency and unpredictable influx volume. Alternatively, the co-digestion of these seaweeds with organic municipal solid waste is economically and energetically advantageous, potentially enhancing energy recovery by 5-fold. Notably, the hydrogen sulfide fraction of the biogas generated must be controlled given its corrosive properties and potential to effect co-generation engine damage and failure. Additional income can also be derived through the agricultural application of the digestate generated both locally and externally, following ammonia treatment and heavy metal stripping. Further research and pilot-scale studies are therefore necessary to support the utilisation of this marine biomass in commercial energy and fertiliser production.
Recently, environmental problems such as climate change and global warming caused by the greenhouse effect have become a worldwide topic of concern. In this article, two kinds of seaweed porous biochars were prepared by utilizing widely sourced seaweed (sargassum and enteromorpha) using single step KOH activation. The physical and chemical properties of the seaweed porous biochar adsorbents were characterized, and CO2 adsorption performance over seaweed porous biochars was tested in a fixed-bed adsorption system. The textural properties and functional groups of the raw seaweed biochars are significantly improved by KOH activation. The seaweed porous biochars (SCK-800-1 and ECK-800-1) prepared with KOH/biomass weight ratio of 1:1 at 800 °C exhibit the maximum CO2 capacity (reaching 1.05 mmol/g and 0.52 mmol/g at 25 °C, respectively). The adsorption capacity of CO2 decreases with the increase of adsorption temperature, and increases with the increase of CO2 initial concentration. The flue gas components such as O2 and NO do not affect the adsorption capacity of CO2 for SCK-800-1 and ECK-800-1, while SO2 slightly inhibits the CO2 adsorption performance. After ten cycles of adsorption-desorption, the adsorption capacities of seaweed porous biochars only decrease slightly. The pseudo-first order model better fits the experimental data, which demonstrates that the external mass transfer plays a dominant role in CO2 adsorption over two kinds of seaweed porous biochars. The present results may inspire new research interests and provide necessary theoretical guidance for the application and research of seaweed biomass-based biochars for CO2 capture, and effectively expand the utilization of marine biomasss.
Activated carbons are well-known porous materials as an effective adsorbent used for the removal of emerging contaminants, such as herbicides, which are increasingly present in water bodies. Most water treatment plants, specially in Brazil, are unable to completely remove such contaminants by the conventional process and advanced treatment using activated carbons is required. The aim of this paper was to verify the influence of the activated carbons granulometry and specific surface area on the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide removal efficiency using distilled-deionized water and filtered water collected from a conventional Water Treatment Plant. Commercial activated carbons samples used in this work were obtained from two different manufacturers. Activated carbons were analyzed by the specific surface area, pore size and volume distribution, nuclear magnetic resonance, infrared and x-ray spectroscopy, moisture, volatile matter and ash contents. Batch adsorption isotherms experiments were used and performed by Langmuir and Freundlich models. Granular and powdered activated carbons removed over 99% of 2,4-D in distilled water and near to 99% using filtered water. The activated carbons evaluated in this work presented high performance and played a key role in water treatment by removing 2,4-D herbicide, ensuring the protection of human health and the ecosystem.
The activated carbon was made of carbonized chest nut shell (CCS) and used as low cost adsorbent for 2,4-D (2,4-dichlorophenoxyacetic acid) removal. The experiments were conducted at different temperatures such as 35, 45 and 55 °C and this system represents as L type adsorption behavior. The experimental data were modelled using several isotherm models such as Langmuir, Freundlich, Temkin and Dubinin Radushkevich. The adsorption dynamics were searched by applying pseudo first, pseudo second and intra particle diffusion models. The thermodynamic approach was conducted for determining the thermodynamic values of ΔH°, ΔS° and ΔG°.
In this work, activated carbons prepared from rice husk (RH) and coffee husk (CH), using NaOH or ZnCl2 as activating agents, were evaluated for the removal of acetaminophen (ACE) in both distilled water and synthetic urine. The activated carbon prepared from RH and activated with NaOH showed the best results in both matrices, which was attributed to the high external surface area and the microporosity developed in the activation process. The influence of the activation temperature (500–800 °C) in the preparation of the activated carbons from RH was also tested. As temperature raised to 800 °C, surface and microporous areas further increased to 1004 and 869 m² g⁻¹, respectively. Consequently, the material obtained at 800 °C (RH-NaOH-800) allowed a better ACE removal, which showed to be more efficient compared with a commercial activated carbon. The developed material did not experience a detrimental effect by the urine components (more than 95% of ACE was removed in both cases). Furthermore, the adsorption process showed a well-fit to the Redlich-Peterson isotherm. β values of approximately 1, indicated that the process resembles Langmuir, and suggests a homogeneous adsorption process. Kinetics analysis showed a better fit for the pseudo-second-order model, while the intra-particle diffusion model showed that the adsorption of ACE occurs both at the surface and within the material pores. According to thermodynamic results, the process occurred by physisorption in an endothermic and spontaneous way. Also, the adsorption mechanism showed that ACE is adsorbed on RH-NaOH-800 by hydrogen bonds and π-π interactions.
Abstract
Clopyralid degradation by different treatment processes combining olive stone activated carbon (OSAC), ozone and Solar-Simulated Radiation (SSR) were studied. Firstly, a detailed study of clopyralid adsorption onto OSAC was carried out. The fitted experimental data suggest pseudo-first order kinetics and Freundlich equilibrium isotherm models to describe the process. Secondly, the application of catalytic ozonation was explored. The combination of ozone and OSAC significantly improved the generation of hydroxyl radicals. Moreover, the catalyst showed higher stability and kept efficiency in reuse cycles, if compared to adsorption. Thirdly, the combination of O3, OSAC, and SSR was applied, and different systems were compared, focusing on pH as the main variable. At basic pH (pH = 9), the best removal rate was achieved by O3/OSAC/SSR. Finally, all systems were applied for the treatment of the target compound in an urban wastewater matrix, focusing on the effect of inorganic carbon. The presence of carbonates inhibited only the mineralization rate, not affecting the compound removal.
Compared to land, the ocean is much richer in biomass resources. As an attempt to actively explore the utilization of these vast marine biomass resources, in this study, novel activated carbons were prepared from two representative seaweed species (sargassum and enteromorpha), and their efficiencies and mechanisms for Hg ⁰ removal were evaluated in a fixed bed reactor. The effects of modification methods, modification temperatures and reaction temperatures on Hg ⁰ removal were also studied. The experimental data were also tested with different adsorption kinetic models for the best fits, and standard thermodynamic parameters evaluated in order to elucidate Hg ⁰ adsorption mechanisms. The results appear to reveal that the performances of seaweed biomass-based activated carbons (denoted SAC and EAC, respectively) for Hg ⁰ removal, are by far more superior to those of seaweed biomass-based the same pyrolysis chars. The best activation temperature for both samples was found to be 800 °C (and hence denoted SAC-800 and EAC-800); and the Hg ⁰ removal efficiency of both samples also increased with increasing reaction temperature. The kinetic results show that the Hg ⁰ removal is controlled by the external mass transfer at 80 °C and controlled by the chemisorption at 120 °C and 160 °C. It was determined that the Hg ⁰ process was a combination of physisorption and chemisorption; with the excellent physical properties (specific surface area and pore structure), and the surface active sites (C-Cl groups and oxygen species) responsible for the physisorption and chemisorption, respectively.
Novel Fe3O4-CsxWO3/NiAl layered double hydroxides composites (FCW/LDH) for the activation of peroxymonosulfate (PMS) and the succedent degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was synthesized through a simple method. The composites prepared were characterized by XRD, SEM, EDS, FT-IR, UV-vis DRS, and N2 physisorption, respectively. It was found that FCW/LDH could effectively catalyze PMS to generate sulfate radicals (SO4-•) to degrade 2,4-D. The added 2,4-D (20 mg/L) was almost completely removed (with a removal of 90.53%) in 180 min by using 1.00 g/L FCW/LDH and 0.50 g/L PMS. Several related factors (PMS concentration, initial pH, disturbing anions) were tested in order to understand their effect on the degradation performance. Furthermore, the photocatalysts exhibited good reusability and stability after four recycles. Finally, a possible degradation mechanism was provided according to above experimental results. This desired FCW/LDH composites showed promising application in purifying the water.
Scientists scramble to explain unusual bloom of Sargassum weed.
Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-metylphenoxyacetic acid (MCPA) from aqueous solution onto activated carbons derived from various lignocellulosic materials including willow, miscanthus, flax, and hemp shives was investigated. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first order and pseudo-second order equations. The adsorption kinetics of both herbicides was better represented by the pseudo-second order model. The adsorption isotherms of 2,4-D and MCPA on the activated carbons were analyzed using the Freundlich and Langmuir isotherm models. The equilibrium data followed the Langmuir isotherm. The effect of pH on the adsorption was also studied. The results showed that the activated carbons prepared from the lignocellulosic materials are efficient adsorbents for the removal of 2,4-D and MCPA from aqueous solutions.
This work aimed at comparing different UV and H2O2 based advanced oxidation processes (AOPs) −photolysis, UV/H2O2, and photo-Fenton reaction- for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), a common ingredient of phytosanitary products. The influence of oxidant dose (H2O2), catalyst type and concentration, pollutant concentration, water matrix and irradiation spectrum was also analyzed. Under reference conditions (25 mg/L of 2,4-D in osmosed water), photo-Fenton oxidation using Fe²⁺ salt, initial pH value of 2.6 and a low-pressure mercury vapor lamp (10 W, λ = 254 nm) yielded more than 85% of pollutant mineralization in one hour, as compared to 60% and less than 10% for UV/H2O2 and photolysis, respectively. Such a performance could be achieved in 10 min only when applying optimal concentration range for Fenton’s reagent (2 to 5 times the stoichiometric amount of H2O2 and oxidant-to-catalyst molar ratio from 25 to 40). Conversely, addition of a ZSM-5 zeolite bearing iron active sites albeit catalyzing Fenton oxidation at natural pH – did not bring additional benefit to UV/H2O2 process. Use of wastewater treatment plant effluent as aqueous matrix or irradiation in the UVA-visible range somewhat lowered the fficiency of the homogeneous photo-Fenton process. Nonetheless, bench scale experiments under sunlight gave promising results for 2,4 D remediation in wastewater, leading to over 80% conversion of the pollutant within ten minutes.
This study investigated the preparation of activated carbon from low-cost biomass as precursor and the using of obtained activated carbon for the removal of Fe(III) and 2,4-D pollutants from model solution. The different parameters affecting the adsorption were examined. Equilibrium data were fitted into Langmuir, Freundlich, D-R and Temkin isotherm models for four different examined temperatures (from 20°C to 50°C). Adsorption of 2,4-D was well described by Freundlich isotherm as a physical adsorption, whereas Langmuir model well described the adsorption of Fe(III) at four different temperatures from 20°C to 50°C. Pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich models were used to analyse kinetic data. The adsorption kinetics for both pollutants were found to match pseudo-second-order kinetic model with high correlation (between 0.975-0.999 for Fe(III), between 0.995-0.999 for 2,4-D) than the other models. In addition, the thermodynamic parameters were evaluated and discussed for the thermodynamically modelling of the adsorption processes.
Highly porous nitrogen-doped carbon was obtained from the pyrolysis of ionic liquid (IL)-incorporated metal-organic frameworks (MOF, named ZIF-8) (IL@ZIF-8). IL@ZIF-8-derived carbon (IMDC), MOF-derived carbon (MDC, obtained from pure ZIF-8), and commercial activated carbon (AC) were applied in the removal of the toxic herbicides diuron [3-(3,4 dichlorophenyl)-1,1-dimethylurea), DUR] and 2,4-dichlorophenoxyacetic acid (2,4-D) from water. The adsorption capacity of IMDC was found to be the highest for DUR and was also remarkable for 2,4-D compared with any reported adsorbent, including MDC and AC. The maximum adsorption capacities of IMDC for DUR and 2,4-D were 284 and 448 mg·g⁻¹, respectively. The remarkable adsorption efficiency of IMDC is probably due to the abundant number of active sites present on its surface because of nitrogen doping and its relatively high porosity, even though it is less porous than MDC. To determine a plausible adsorption mechanism, not only detailed characterizations of the adsorbents were performed but also adsorptions across a wide pH range were carried out. Hydrogen bonding (IMDC: H-donor; adsorbates: H-acceptor) with hydrophobic and π-π interactions was suggested as a plausible mechanism for adsorption. Moreover, IMDC can be regenerated by a simple solvent treatment and used for successive adsorptive removal of the studied adsorbates. Therefore, IMDC is recommended as a potent adsorbent for the removal of herbicides such as DUR and 2,4-D from water.
The environmental friendly and cost-effective few-layered graphene nanosheets (GNs) are identified as superior adsorbent for chlorophenoxyacetic acid herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP) from an aqueous solution. The effects of pH, ionic strength and temperature on the adsorption of herbicides were explored. The prepared GNs showed the maximum removal efficiencies of 82, 80, 86, 82 and 70% for 2,4-D, 2,4-DP, 2,4,5-T, MCPA and MCPP respectively. The results revealed that the adsorption follows a pseudo-second-order kinetics model and confirms the Langmuir adsorption isotherm. From the thermodynamic parameters, it is suggested that the adsorption of herbicides on GNs follows the endothermic and spontaneous processes. The results show that the electrochemically prepared GNs will be considered the suitable material for water purification in the near future.
An environmentally benign and efficient hydrothermal carbonization method is widely applied for the preparation of carbon-based adsorbents. However, the adsorption capacity toward anionic species would be influenced due to the negatively charged surface of the traditional hydrothermal carbonaceous materials; moreover most of the carbonaceous materials were in the form of powder which restricted the practical applications. Herein, amino-rich hydrothermal carbon-coated electrospun polyacrylonitrile fiber (PAN@NC) adsorbents were obtained through one-step hydrothermal carbonization approach assisted by diethylenetriamine using polyacrylonitrile (PAN) fibers as the templates, which showed highly efficient adsorption for anionic pollutants. The PAN@NC fibers were characterized in detail to confirm their structures and composition. The flexible and robust PAN@NC fiber membrane exhibited high adsorption capacity and good regeneration and recycling ability toward the anionic metal ion Cr(VI) and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). According to the Langmuir model, the adsorption behaviors showed monolayer adsorption capacities of 290.70 mg/g and 164.47 mg/g for Cr(VI) and 2,4-D, respectively, which were higher than that of many other adsorbents. Recycling study indicated that the removal efficiencies for both pollutants retained above 90% after five cycles. These findings demonstrate that PAN@NC fibers are promising adsorbents for the removal of anionic pollutants from wastewater solutions.
Background: Heavy metals pollution of drinking water has become one of the most serious problems due to their sever toxicities to human body. Materials and Methods: In this study, the adsorption of Pb⁺², Cd⁺² and Cu⁺² ions from contaminated water using dried brown alga Sargassum latifolium (SAP) and its activated carbon (SAC) was investigated. The impact of different parameters such as initial metal ions concentration, contact time, adsorbent dose and pH on the removal were evaluated. Results: The optimum adsorption was found to occur at contact time 60 min, pH value 5.0, adsorbent dose 8.0 g L⁻¹ and initial concentration 80 mg L⁻¹. The maximum removal capacity of SAC was 167 mg g⁻¹ for Cd⁺², 147 mg g⁻¹ for Cu⁺² and 141 mg g⁻¹ for Pb⁺². The SAC was found to be the highest efficient column capable to remove 100% of heavy metals from drinking water samples. Conclusion: Thus SAC column is considered as an efficient and cheap biotechnology for removing the heavy metals in drinking water treatment plants.
The adsorption characteristics of carbonaceous materials obtained by combustion synthesis and commercial carbon blacks for the removal of 2,4-dichlorophenol and 2,4-dichlorophenoxyacetic acid from aqueous solutions, have been investigated. The adsorption was studied in a batch adsorption system, including both kinetics and equilibrium. The kinetics was fitted with the pseudo-first order, pseudo-second order and intraparticle diffusion models. The adsorption kinetics was found to follow the pseudo-second order model with the coefficient of determination values greater than 0.99. The adsorption isotherms were determined and modeled with the Freundlich and Langmuir equations. The experimental data received were found to be well described by both the Freundlich and Langmuir models. The effect of the solution pH on the adsorption was also studied.
Activated carbons (ACs) are widely used in the purification of drinking water without almost any knowledge about the adsorption mechanisms of the persistent organic pollutants. Chlordecone (CLD, Kepone) is an organochlorinated synthetic compound that has been used mainly as agricultural insecticide. CLD has been identified and listed as a persistent organic pollutant by the Stockholm Convention. The selection of the best suited AC for this type of contaminants is mainly an empirical and costly process. A theoretical study of the influence of AC surface groups (SGs) on CLD adsorption is done in order to help understanding the process. This may provide a first selection criteria for the preparation of AC with suitable surface properties. A model of AC consisting of a seven membered ring graphene sheet (coronene) with a functional group on the edge was used to evaluate the influence of the SGs over the adsorption. Multiple Minima Hypersurface methodology (MMH) coupled with PM7 semiempirical Hamiltonian was employed in order to study the interactions of the chlordecone with SGs (hydroxyl and carboxyl) at acidic and neutral pH and different hydration conditions. Selected structures were re-optimized using CAM-B3LYP to achieve a well-defined electron density to characterize the interactions by the Quantum Theory of Atoms in Molecules approach. The deprotonated form of surface carboxyl and hydroxyl groups of AC models show the strongest interactions, suggesting a chemical adsorption. An increase in carboxylic SGs content is proposed to enhance CLD adsorption onto AC at neutral pH conditions.
In this study, the solar photocatalytic activity of ZnO-Fe2O3 coupled oxide was investigated for the degradation of commercial Dicamba and 2,4-D herbicides. Both pesticides, which are extensively used in agriculture, are active ingredients in water-soluble commercial formulations called Fortune (R) (480 g/L 3,6-dichloro-2-methoxybenzoic acid, Dicamba) and Hierbamina (R) (479.5 g/L 2,4-dichlorophenoxyacetic acid, 2,4-D). The catalyst was synthesized via the sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and Raman spectroscopy. UV-vis diffuse reflectance spectroscopy (DRS) was used to estimate the band gap energy (Eg) of the prepared material. Photocatalytic tests were conducted in a planar reactor operated in batch-mode using a solar light simulator. Complete degradation of both herbicides was attained for a 10 mg/L initial concentration after 300 min using 0.5 g/L of catalyst loading. Oxalic, formic, and acetic acids were the byproducts identified during the degradation of both herbicides. Dechlorination after photocatalytic decomposition was complete for Dicamba. However, only 70% dehalogenation was attained for 2,4-D under simulated solar light
This report presents a comprehensive study of the degradation kinetics of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) using ozone with and without intensification with ultraviolet C (UVC) radiation. The byproducts cause several series-parallel reactions that compete with the process of photon absorption when radiation is applied. Five processes were analyzed separately: (i) the direct photolysis of 2,4-D and its main byproducts, (ii) direct ozonation in the absence of hydroxyl radicals using tert-butyl alcohol as radical scavenger, (iii) the oxidation when ozone reacts in parallel with hydroxyl radicals, (iv) the reaction enhanced with UVC radiation, and (v) the oxidation improved by pH modifications. A kinetic model was developed on the basis of the main reaction byproducts. The corresponding parameters of the reacting system were determined (nine of its 29 kinetic constants were previously unknown). Simulation results, including a rigorous description of the reacting system and the radiation field (having dark and illuminated volumes), agree very well with the experimental data.
Sudden beaching of huge seaweed masses smother the coastline and form rotting piles on the shore. The number of reports of these events in previously unaffected areas has increased worldwide in recent years. These 'seaweed tides' can harm tourism-based economies, smother aquaculture operations or disrupt traditional artisanal fisheries. Coastal eutrophication is the obvious, ultimate explanation for the increase in seaweed biomass, but the proximate processes that are responsible for individual beaching events are complex and require dedicated study to develop effective mitigation strategies. Harvesting the macroalgae, a valuable raw material, before they beach could well be developed into an effective solution.
Among the clay minerals, montmorillonite is the most extensively studied material using as adsorbents, but palygorskite and its organically modified products have been least explored for their potential use in contaminated water remediation. In this study, an Australian palygorskite was modified with cationic surfactants octadecyl trimethylammonium bromide and dioctadecyl dimethylammonium bromide at different doses. A full structural characterization of prepared organo-palygorskite by X-ray diffraction, infrared spectroscopy, surface analysis and thermogravimetric analysis was performed. The morphological changes of palygorskite before and after modification were recorded using scanning electron microscopy, which showed the surfactant molecules can attach on the surface of rod-like crystals and thus can weaken the interactions between palygorskite single crystals. Real surfactants loadings on organo-palygorskites were also calculated based on thermogravimetric analysis. 1 CEC, 2 CEC octadecyl trimethylammonium bromide modified palygorskites, 1 CEC and 2 CEC dioctadecyl dimethylammonium bromide modified palygorskites absorbed as much as 12mg/g, 42mg/g, 9mg/g and 25mg/g of 2,4-dichlorophenoxyacetic acid respectively. This study has shown a potential on organo-palygorskites for organic herbicide adsorption especially anionic ones from waste water. In addition, equilibration time effects and the Langmuir and Freundlich models fitting were also investigated in details.
In this work data are reported on the possibility for detection of environmental contaminants endowed with toxic effects by specifically designed electrochemical biosensors. A new bienzymatic inhibition biosensor based on the combined catalytic activity of the enzymes alkaline phosphatase and glucose oxidase is proposed and discussed for the direct determination of 2, 4-dichloro-phenoxyacetic acid (2, 4-D), one of the most powerful and diffused defoliants, which also is endowed with estrogenic properties. A discussion on the different approaches followed to manage the experimental data obtained by enzymatic inhibition biosensors is also presented.