Adsorption of 2,4-dichlorophenol and 2,4-dichlorophenoxyacetic acid from aqueous solutions on carbonaceous materials obtained by combustion synthesis

Enhanced biodegradation of 2, 4-dichlorophenol in packed bed biofilm reactor by impregnation of polyurethane foam with Fe3O4 nanoparticles: Bio-kinetics, process optimization, performance evaluation and toxicity assessment

In this work, an effort has been made to enhance the efficacy of biological process for the effective degradation of 2, 4-dichlorophenol (2, 4-DCP) from wastewater. The polyurethane foam was modified with Fe3O4 nanoparticles and combined with polyvinyl alcohol, sodium alginate, and bacterial consortium for biodegradation of 2, 4-DCP in a packed bed biofilm reactor. The maximum removal efficiency of 2, 4-DCP chemical oxygen demand, and total organic carbon were found to be 92.51 ± 0.83 %, 86.85 ± 1.32, and 91.78 ± 1.24 %, respectively, in 4 days and 100 mg L-1 of 2, 4-DCP concentration at an influent loading rate of 2 mg L-1h-1 and hydraulic retention time of 50 h. Packed bed biofilm reactor was effective for up to four cycles to remove 2, 4-DCP. Growth inhibition kinetics were evaluated using the Edward model, yielding maximum growth rate of 0.45 day-1, inhibition constant of 110.6 mg L-1, and saturation constant of 62.3 mg L-1.

Enhancing the adsorption capacity of organic and inorganic pollutants onto impregnated olive stone derived activated carbon

This study presents a sustainable approach to activated carbon production from olive stones in comparison to commercial ones, using various activating agents such as H3PO4, KOH, and ZnCl2, for enhancing the adsorption properties and versatile adsorption capability to remove a range of pollutants including copper ion, methylene blue, and 2,4-Dichlorophenoxyacetic acid from aqueous solutions. The performances of activated carbons across varying conditions such as pollutant concentrations, temperatures, pH levels, and adsorbent amounts were tested. Increased initial pollutant concentrations correlated with higher adsorption capacities. Maximum adsorption capacities were achieved at pH levels of 5, 10, and 2 for Cu, MB, and 2,4-D, respectively. For KOSAC, Cu removal rose from 27 % to 52 %, for ZOSAC, MB removal increased from 39 % to 65 %, and for ZOSAC, 2,4-D removal surged from 33 % to 99 % at varying adsorbent amounts. Model validation was carried out utilizing the kinetic models (PFO, PSO) and isotherm models (Langmuir, Redlich-Peterson). The PFO kinetic model and Langmuir isotherm model proved more suitability for Cu adsorption, whereas PFO and PSO kinetic models, along with Redlich-Peterson isotherm models, were more prominent for MB and 2,4-D adsorption. Thermodynamic analysis revealed that the adsorption of Cu and 2,4-D was exothermic, while MB adsorption was endothermic. By optimization of experimental conditions, the maximum adsorption capacities were attained at 30.34 °C and 297.65 mg L-1 for KOSAC-Cu, 48.62 °C and 269.37 mg L-1 for ZOSAC-MB, and 30.31 °C and 299.02 mg L-1 for ZOSAC-2,4-D sorption. This research highlights ZOSAC's potential as a cost-effective, eco-friendly solution for water treatment, contributing to environmental sustainability and economical feasibility.

Ethylene Elimination Using Activated Carbons Obtained from Baru (Dipteryx alata vog.) Waste and Impregnated with Copper Oxide

Ethylene is a plant hormone regulator that stimulates chlorophyll loss and promotes softening and aging, resulting in a deterioration and reduction in the post-harvest life of fruit. Commercial activated carbons have been used as ethylene scavengers during the storage and transportation of a great variety of agricultural commodities. In this work, the effect of the incorporation of copper oxide over activated carbons obtained from baru waste was assessed. Samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption at -196 °C, field-emission scanning electron microscopy (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDS), and infrared (IR) spectroscopy. The results showed that the amount of ethylene removed using activated carbon obtained from baru waste and impregnated with copper oxide (1667 μg g-1) was significantly increased in comparison to the raw activated carbon (1111 μg g-1). In addition, carbon impregnated with copper oxide exhibited better adsorption performance at a low ethylene concentration. Activated carbons produced from baru waste are promising candidates to be used as adsorbents in the elimination of ethylene during the storage and transportation of agricultural commodities at a lower cost.

Influence of light-emitting diodes (LEDs) on the 2,4-diclorophenoxyacetic acid phytoremediation by plectranthus neochilus

2,4-Dichlorophenoxyacetic acid (2,4-D) is an herbicide widely used in crops against broadleaf weeds. However, 2,4-D residues are considered an environmental pollutant in bodies of water. Phytoremediation with Plectranthus neochilus is a substantial strategy to remove 2,4-D from the aquatic environment. The objective of this study was to verify the efficiency of the association of the photostimulus by Light Emitting Diodes (LED) with P. neochilus to improve phytoremediation of 2,4-D in water. Phytoremediation was evaluated with the following samples: natural light, white LED, blue LED, and red LED, with and without the plant as controls. The data corresponding to the validation of the method were in accordance with the required parameters: R2: 0.9926; RSD: 1.74%; LOD: 0.075 mg.L-1; LOQ: 0.227 mg.L-1 and recovery by SPE was 76.57%. The efficiency of the association of LED with P. neochilus in the 28 days was: ambient light + plant (47.0%); white light + plant (37.10%); blue light + plant (26.80%); red light + plant (3.32%). This study demonstrated, for the first time, the efficiency of using LEDs light in association with P. neochilus for the phytoremediation of 2,4-D in water.

Enhanced adsorption of phenolic compounds using biomass-derived high surface area activated carbon: Isotherms, kinetics and thermodynamics

The progress of industrial and agricultural pursuits, along with the release of inadequately treated effluents especially phenolic pollutant, has amplified the pollution load on environment. These organic compounds pose considerable challenges in both drinking water and wastewater systems, given their toxicity, demanding high oxygen and limited biodegradability. Thus, developing an eco-friendly, low-cost and highly efficient adsorbent to treat the organic pollutants has become an important task. The present investigation highlights development of a novel adsorbent (CFPAC) by activation of Cassia fistula pod shell for the purpose of removing phenol and 2,4-dichlorophnenol (2,4-DCP). The significant operational factors (dosage, pH, concentration, temperature, speed) were also investigated. The factors such as pH = 2 and T = 20°C were found to be significant at 1.6 g/L and 0.6 g/L dosage for phenol and 2,4-DCP respectively. Batch experiments were further conducted to study isotherms, kinetic and thermodynamics studies for the removal of phenol and 2,4-DCP. The activated carbon was characterised as mesoporous (specific surface area 1146 m2/g, pore volume = 0.8628 cc/g), amorphous and pHPZC = 6.4. At optimum conditions, the maximum sorption capacity for phenol and 2,4-DCP were 183.79 mg/g and 374.4 mg/g respectively. The adsorption isotherm was better conformed to Redlich Peterson isotherm (phenol) and Langmuir isotherm (2,4-DCP). The kinetic study obeyed pseudo-second-order type behaviour for both the pollutants with R2 > 0.999. The thermodynamic studies and the value of isosteric heat of adsorption for both the pollutants suggested that the adsorption reaction was dominated by physical adsorption (ΔHx < 80 kJ/mol). Further, the whole process was feasible, exothermic and spontaneous in nature. The overall studies suggested that the activated carbon synthesised from Cassia fistula pods can be a promising adsorbent for phenolic compounds.

Phenolic compounds occurrence and human health risk assessment in potable and treated waters in Western Cape, South Africa

Phenolic pollutants from industrial and agricultural activities pose a major threat to the world's potable water supply. The persistent micro-pollutants often find their way into drinking water sources with possible adverse human health implications. In this study, bottled water, tap water, and wastewater treatment plant (WWTP) effluent samples from the Boland region of the Western Cape, South Africa were assessed to determine 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) levels using HPLC/DAD instrumentation. The selected area is known for its vast agricultural ventures and wineries. Evaluation of the human health risk (cancer risk) for the pollutants was conducted using the hazard quotient (HQ). The Ames mutagenicity test was also conducted using the Salmonella typhimurium T98 and T100 strains and the S9 activation enzyme. Trace levels of the phenolics were detected in the samples with a range of 9.32 × 10-7-1.15 × 10-4 mg/L obtained for 4-CP, and 8.80 × 10-7-1.72 × 10-4 mg/L recorded for 2,4-DCP. Both compounds had levels below the limit of 0.01 mg/L prescribed by South African legislation. The assessed HQ for the phenolic concentrations indicates a low level of potential ecological risk and none of the samples had a cancer risk value that exceeded the regulatory limit. The possibility of the analyzed samples causing cancer is unlikely, but non-carcinogenic adverse effects were found. Strong mutagenicity was observed for the T98 strains with a potential ability to cause mutation toward the insertion or deletion of a nucleotide. The T100 bacterial strain showed very slight mutagenicity potential, however, it is unlikely to cause any mutation. The levels of phenolics in the potable water samples may pose a significant threat to human health. Hence, screening persistent organic chemicals in potable water sources and evaluating their potential human health effects is pertinent to prevent associated health challenges.

Removal of an agricultural herbicide (2,4-Dichlorophenoxyacetic acid) using magnetic nanocomposite: A combined experimental and modeling studies

This study focused on modeling the removal of one of the widely used agricultural herbicides known as 2,4-Dichlorophenoxyacetic acid (2,4-D) using polypyrrole-coated Fe2O3 nanoparticles (Fe2O3@PPy). The Fe2O3@PPy nanocomposite was synthesized by surface-coating the Tabebuia aurea leaf extract synthesized Fe2O3 nanoparticles with polypyrrole. After characterization, the adsorptive potential of the nanocomposite for removing 2,4-D from aqueous solution was examined. Central composite design (CCD) was employed for optimizing the adsorption, revealing an adsorption efficiency of 90.65% at a 2,4-D concentration of 12 ppm, a dosage of 3.8 g/L, an agitation speed of 150 rpm, and 196 min. Adsorption dataset fitted satisfactorily to Langmuir isotherm (R2: 0.984 & χ2: 0.054) and pseudo-second-order kinetics (R2: 0.929 & χ2: 0.013) whereas the exothermic and spontaneous nature were confirmed via the thermodynamic study. The predictive models, including adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN), and response surface methodology (RSM), demonstrated good precision for the prediction of 2,4-D adsorption, with respective R2 of 0.9719, 0.9604, and 0.9528. Nevertheless, statistical analysis supported ANFIS as the better forecasting tool, while RSM was the least effective. The maximum adsorption capacity of 2,4-D onto the Fe2O3@PPy nanocomposite was 7.29 mg/g, significantly higher than a few reported values. Therefore, the Fe2O3@PPy nanocomposite could serve as a competent adsorbent to remove 2,4-D herbicide from aqueous streams.

A novel magnetic adsorbent from activated carbon fiber and iron oxide nanoparticles for 2,4-D removal from aqueous medium

Carbonaceous materials have been widely applied as adsorbents, but there are some factors that affect their efficiency. In this context, advances in nanotechnology provide new and more efficient methodologies for water treatment. This study evaluated the efficiency of a novel carbon-based adsorbent developed from Brazilian polyacrylonitrile textile fiber and functionalized with iron oxide magnetic nanoparticles for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from the aqueous medium. The synthesized adsorbent (ACF-Fe3O4) was characterized by FTIR, XRD, VSM, Zeta potential, SEM, EDX, and TEM. The characterization techniques showed that the adsorbent has peaks characteristic of its precursors and superparamagnetic characteristics, confirming the efficiency of the synthesis method. The adsorption tests evaluated the influence of adsorbent dosage, pH of the contaminant solution, contact time and temperature on the removal of 2,4-D. The experimental data were better adjusted by the pseudo-second order kinetic model and by the Langmuir isothermal model. The thermodynamic parameters revealed that the process is exothermic, spontaneous and thermodynamically favorable. Under the best experimental conditions, the maximum adsorption capacity obtained was 51.10 mg g-1 with an adsorbent concentration of 0.33 g L-1, natural pH of the solution, temperature of 288 K at the equilibrium time of six hours. Adsorbent reusage was studied in four desorption cycles. The adsorption mechanism can be explained through π-π bonds, hydrogen bonds and electrostatic interactions. The prepared material presented high-efficiency adsorption capacity of 2,4-D compared to other carbonaceous materials present in the literature, demonstrating its viability for the removal of this contaminant from the aqueous medium.

Adsorption of Phenoxyacetic Herbicides from Water on Carbonaceous and Non-Carbonaceous Adsorbents

The increasing consumption of phenoxyacetic acid-derived herbicides is becoming a major public health and environmental concern, posing a serious challenge to existing conventional water treatment systems. Among the various physicochemical and biological purification processes, adsorption is considered one of the most efficient and popular techniques due to its high removal efficiency, ease of operation, and cost effectiveness. This review article provides extensive literature information on the adsorption of phenoxyacetic herbicides by various adsorbents. The purpose of this article is to organize the scattered information on the currently used adsorbents for herbicide removal from the water, such as activated carbons, carbon and silica adsorbents, metal oxides, and numerous natural and industrial waste materials known as low-cost adsorbents. The adsorption capacity of these adsorbents was compared for the two most popular phenoxyacetic herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA). The application of various kinetic models and adsorption isotherms in describing the removal of these herbicides by the adsorbents was also presented and discussed. At the beginning of this review paper, the most important information on phenoxyacetic herbicides has been collected, including their classification, physicochemical properties, and occurrence in the environment.

Adsorption of 2,4-D and MCPA Herbicides on Carbon Black Modified with Hydrogen Peroxide and Aminopropyltriethoxysilane

The carbon black N-220 surface was subjected to modification through H2O2 oxidation and deposition of aminopropyltriethoxysilane. The pristine (CB-NM) and modified materials (CB-Ox and CB-APTES) were characterized by N2 adsorption−desorption isotherms, scanning electron microscopy, energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetry, and FTIR spectroscopy. Carbon black samples were applied as adsorbents for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) herbicides from aqueous solutions. The influence of their surface properties on adsorption efficiency was analyzed and discussed. The results showed that the adsorption of the herbicides was pH-dependent, and the most favorable adsorption was observed in an acidic environment. The experimental data best fit pseudo-second-order and Langmuir models for kinetic and equilibrium data, respectively. The adsorption rate of both the herbicides increased in the order of CB-APTES < CB-Ox < CB-NM and was closely correlated with the mesopore volume of the carbon blacks. The monolayer adsorption capacities were found to be 0.138, 0.340, and 0.124 mmol/g for the adsorption of 2,4-D and 0.181, 0.348, and 0.139 mmol/g for the adsorption of MCPA on CB-NM, CB-APTES, and CB-Ox, respectively. The results showed that the surface chemistry of the adsorbent plays a more important role than its porous structure. Both herbicides were preferably adsorbed on APTES-modified carbon black and were adsorbed the worst on oxidized carbon black (CB-APTES > CB-NM > CB-Ox).

Efficient removal of 2,4-D from solution using a novel antibacterial adsorbent based on tiger nut residues: adsorption and antibacterial study

We engineered a tiger nut residue (TNR, a low-cost agricultural waste material) through a facile and simple process to take advantage of the introduced functional groups (cetylpyridinium chloride, CPC) in the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in batch mode and further investigated its impingement on bacterial growth in a yeast-dextrose broth. The surface characterizations of the adsorbent were achieved through Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller method (BET), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The batch adsorption studies revealed that solution pH, adsorbent dose, temperature, and salt affected the adsorptive capacity of TNR-CPC. The equilibrium data were best fitted by Langmuir isotherm model with a maximum monolayer adsorption capacity of 90.2 mg g^-1 at 318 K and pH 3. Pseudo-second-order model best fitted the kinetics data for the adsorption process. Physisorption largely mediated the adsorption system with spontaneity and a shift in entropy of the aqueous solid-solute interface reflecting decreased randomness with an exothermic character. TNR-CPC demonstrated a good reusability potential making it highly economical and compares well with other adsorbents for decontamination of 2,4-D. The adsorption of 2,4-D proceeded through a probable trio-mechanism; electrostatic attraction between the carboxylate anion of 2,4-D and the pyridinium cation of TNR-CPC, hydrogen bonding between the hydroxyl (-OH) group inherent in the TNR and the carboxyl groups in 2,4-D and a triggered π-π stacking between the benzene structures in the adsorbate and the adsorbent. TNR-CPC reported about 99% inhibition rate against both gram-positive S. aureus and gram-negative E. coli. It would be appropriate to investigate the potential of TNR-CPC as a potential replacement to the metal oxides used in wastewater treatment for antibacterial capabilities, and its effects against airborne bacteria could also be of interest.

High surface area acid-treated biochar from pomegranate husk for 2,4-dichlorophenol adsorption from aqueous solution

In the present study, zinc chloride (ZnCl₂) followed by acid treating was employed for the fabrication of activated biochar from pomegranate husk (APHBC) for 2,4-dichlorophenol (2,4-DCP) adsorption from an aqueous solution. The batch adsorption experiments were carried out as a function of solution pH, APHBC dose, initial 2,4-DCP concentration, contact time, and ionic strength. The APHBC showed a well-developed pore with specific surface areas of 1576 m²/g due to explosive characteristics of ZnCl₂. In addition, the XRD analysis showed that the diffraction peaks between 15 and 35° corresponded to amorphous carbon. The pore size distribution results showed that APHBC was dominantly mesoporous materials. The pH_pzc value of APHBC was 6.15 ± 0.15. According to batch experiments, the optimum adsorption conditions were pH of 3.0, contact time 60 min, APHBC dose of 1.75 g/L and without ionic strengths. The absorption capacity of 2,4-DCP at the initial concentration of 150.0 mg/L promptly decreased from 259.5 ± 12.9 to 74.5 ± 3.7 mg/g as the APHBC dose increased from 0.50 to 2.00 g/L. The isotherm and kinetics study of 2,4-DCP adsorption by APHBC revealed that Liu and Avrami fractional-order well fitted with experimental data, respectively.

Pepsin immobilization: Influence of carbon support functionalization

Among the matrices for enzyme immobilization, activated carbon has been standing out in immobilization processes due to its properties and to its characteristics that provide superficial modification by inserting new functional groups capable of binding the enzymes forming covalent bonds. In this study the effect of different modification methods of activated carbon (functionalization with genipin, metallization, metallization in the presence of chelating agent, and functionalization with glutaraldehyde) on efficiency of pepsin immobilization was evaluated. The effect of immobilization pH and the reaction medium on hydrolysis activity of bovine casein was also evaluated. The functionalization of activated carbon using iron ions allowed an immobilization capacity of 98.93 mg·g^-1, with immobilization efficiency greater than 99%, and enzyme activity of 2.30 U, which was higher than the other modifications, and closer to the enzyme in the native form activity (3.32 U). In general, the carbon surface modifications were responsible for forming more stable bonds between support and enzyme, improving its proteolytic activity (from 1.84 to 2.30 U) when compared to traditional immobilization methods by adsorption and covalent binding using glutaraldehyde (from 1.04 to 1.1 U).

Preparation of a novel non-burning polyaluminum chloride residue(PACR) compound filler and its phosphate removal mechanisms

As an inevitable industrial by-product, polyaluminum chloride residue (PACR) will cause serious harm to the environment if directly buried and dumped. The aim of this paper was searched a new economical, environmental, and practical way of utilization for PACR. In this paper, a novel non-burning PACR compound filler was made from mainly PACR. The prepared compound filler has excellent physical properties and phosphate adsorption efficiency of up to 99.9%. Static adsorption experiments showed that the adsorption process of phosphorus by the compound filler conformed to the pseudo-second-order kinetic model and intra-particle diffusion model. Langmuir and Freundlich isotherm models described the phosphorus adsorption process well, and the maximum phosphate adsorption capacity arrived at 42.55 mg/g. The phosphate adsorption by the compound filler is a spontaneous endothermic process. The main mechanisms are ligand exchange and Lewis acid-base interactions; calcium and aluminum play important roles in the adsorption of phosphorus by the compound filler. Dynamic column experiments showed that as much as 90% of the phosphorus removal by compound filler, and the phosphorus concentration decreased from 1 to ~0.1mg/L. The results provide a new waste resource utilization method for PACR and show the good application potential of prepared compound filler in constructed wetlands.

Immobilisation of phosphonium-based ionic liquid in polysulfone capsules for the removal of phenolic compounds, with an emphasis on 2,4-dichlorophenol, in aqueous solution

Phosphonium-based ionic liquid immobilised in polysulfone capsules were prepared by the phase inversion technique for the adsorption of different phenolic compounds from aqueous solution. Some techniques, including Scanning Electron Microscopy (SEM), surface analysis by Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermogravimetric Analysis (TGA), were used to characterize the capsule and indicated that trihexyltetradecylphosphonium decanoate (ionic liquid) was successfully immobilised in polysulfone, the immobilisation was determined to be 63.29%. Adsorption tests showed that the developed capsules have the potential to remove varied phenolic compounds. For compounds 2,4-dichlorophenol (2,4-DCP) the best removal was achieved between pH 3.0 and 9.0. Temperature variation (25-70 °C) and sodium chloride concentration (0-1000 mg⋅L^-1) had no significant changes in adsorption, demonstrating the scope for using this adsorbent with real effluents. Adsorption kinetics demonstrated the mechanism occurs in second order, the Weber-Morris model delimited the intraparticle diffusion as the adsorption limiter. The Redlich-Peterson model was the isothermal analysis that best suited the experimental data, with a β value equal to 0.821 approaching the Langmuir model, which obtained a q_max of 404.50 mg⋅g^-1. Consequently, these results demonstrate that these capsules have potential application in the treatment of environmental pollution caused by phenolic compounds.

Adsorption investigation of 2,4-D herbicide on acid-treated peanut (Arachis hypogaea) skins

In this work, peanut (Arachis hypogaea) skin, a by-product generated by the agricultural production of its seeds, was employed as a precursor in the preparation of an adsorbent for the 2,4-D removal in water. The skins were treated with sulfuric acid and characterized by different techniques. The adsorption was favored at acid pH = 2 with pH_pzc = 6. The dosage of 0.9 g L^-1 was considered ideal, obtaining satisfactory indications of removal and capacity. The kinetic curves were well represented by the general order model, with the equilibrium reached quickly in the first 30 min for all concentrations. Adsorption isotherm studies showed that the increase in temperature negatively affected the herbicide adsorption, obtaining a maximum capacity of 246.72 mg g^-1, by the Langmuir isotherm at 298 K. The remarkable adsorption efficiency presented by the adsorbent can be associated with the presence of new functional groups on the adsorbent surface generated after the acid treatment. Thermodynamic parameters confirmed the exothermic nature of the adsorptive system. In the treatment of synthetic wastewater consisting of a mixture of herbicides and salts, a high removal efficiency (72%) of herbicides was obtained. Therefore, the development of an adsorbent derived from peanut (Arachis hypogaea) skin treated with sulfuric acid is an excellent alternative, generating remarkable removal results towards 2,4-D herbicide.

Prospective application of diethylaminoethyl cellulose (DEAE-cellulose) with a high adsorption capacity toward the detoxification of 2,4-dichlorophenoxyacetic acid (2,4-D) from water

Detoxification of pesticide residues requires effective methods. In this regard, the adsorption efficiency of diethylaminoethyl cellulose (DEAE-cellulose) as an adsorbent material for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from water at different concentrations, times, pH and temperature was evaluated comprehensively. The obtained results showed that DEAE-cellulose has greater efficacy to eliminate 2,4-D from water with a high Langmuir maximum adsorption capacity of 429.18 mg g^-1 at pH 7.0. Kinetic models and thermodynamics were investigated at length. The adsorption mechanism was understood by way of electrostatic, hydrogen bonding, and Lewis acid-base type interactions. Extensive analytical characterization of the DEAE-cellulose adsorbent before and after 2,4-D adsorption was performed and liquid chromatography with a tandem mass spectrometer (LC-MS/MS) was used for the quantification of 2,4-D. The regeneration of DEAE-cellulose was achievable using dilute formic acid and the DEAE-cellulose adsorbent showed high ability in the removal of 2,4-D from the agriculture run-off water.

Adsorptive and Electrochemical Properties of Carbon Nanotubes, Activated Carbon, and Graphene Oxide with Relatively Similar Specific Surface Area

Three carbon materials with a highly diversified structure and at the same time much less different porosity were selected for the study: single-walled carbon nanotubes, heat-treated activated carbon, and reduced graphene oxide. These materials were used for the adsorption of 2,4-D herbicide from aqueous solutions and in its electroanalytical determination. Both the detection of this type of contamination and its removal from the water are important environmental issues. It is important to identify which properties of carbon materials play a significant role. The specific surface area is the major factor. On the other hand, the presence of oxygen bound to the carbon surface in the case of contact with an organochlorine compound had a negative effect. The observed regularities concerned both adsorption and electroanalysis with the use of the carbon materials applied.

High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments

Activated biocarbons were prepared using biomass wastes: sugarcane bagasse, coconut shell and endocarp of babassu coconut; as a renewable source of low-cost raw materials and without prior treatments. These activated biocarbons were characterized by textural analysis, solid-state ¹³C nuclear magnetic resonance spectroscopy, X-ray diffraction and scanning electronic microscopy. Textural analysis results revealed that those activated biocarbons were microporous, with specific surface area values of 547, 991 and 1,068 m² g^-1 from sugarcane bagasse, coconut shell and endocarp of babassu coconut, respectively. The innovation of this work was to evaluate which biomass residue was able to offer the best performance in removing 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from water by adsorption. Adsorption process of 2,4-D was investigated and the Langmuir and Redlich-Peterson models described best the adsorption process, with R² values within 0.96-0.99. The 2,4-D removal performance were 97% and 99% for the coconut and babassu biocarbons, respectively. q_M parameter values obtained from Langmuir model were 153.9, 233.0 and 235.5 mg g^-1 using sugarcane bagasse, coconut shell and endocarp of babassu, respectively. In addition, the adsorption kinetics were described nicely by the second-order model and the Gibbs free energy parameter values were negative, pointing to a spontaneous adsorption, as well.

2,4-dichlorophenoxyacetic acid (2,4-D) micropollutant herbicide removing from water using granular and powdered activated carbons: a comparison applied for water treatment and health safety

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.

Adsorption kinetic and thermodynamic studies of the 2, 4 - dichlorophenoxyacetate (2,4-D) by the [Co-Al-Cl] layered double hydroxide

[Co-Al-Cl] layered double hydroxide (LDH) obtained by co-precipitation at constant pH 8 presented a single phase in a hexagonal unit cell parameters similar to the hydrotalcite (JCPDS 14-191) belonging to the rhombohedral crystal system and space group R (-3)m . The adsorption kinetics of 2,4-D onto [Co-Al-Cl] LDH was better described by the Pseudo Second-Order (best adjust R2 = 0.9998 for 60 mg L-1 2,4-D adsorption). Intra-particle diffusion model was not the sole rate-controlling factor, indicating the adsorption of 2,4-D by the [Co-Al-Cl] LDH is a complex process for the experimental conditions performed, involving both boundary layer and intra-particle diffusion. The adsorption isotherm adjusted better to the Freundlich model (R2 = 0.9845) and the ΔH° value of - 51.18 kJ mol-1 indicated the predominance of the physical adsorption. The FT-IR spectrum of LDH after adsorption presented 2,4-D bands together with those of LDH and XRD showed an increase in the interlamellar distance (d 003) due to the intercalation of 2,4-D in the interlayer structure of the [Co-Al-Cl] LDH, corroborating inter and intra-particle adsorption data. Thus, [Co-Al-Cl] LDH, commonly used as electrodes in supercapacitors, can be effectively used as an adsorbent for the removal of 2,4-D from contaminated waters.

Preparation of magnetic polyimide@ Mg-Fe layered double hydroxides core-shell composite for effective removal of various organic contaminants from aqueous solution

In this work, a novel core-shell structured magnetic polyimide@layered double oxides (LDO) composites coating a porous polyimide (PI)-coated Fe3O4 magnetic core and layered double hydroxide (LDH) has been successfully synthesized by solve-thermal synthesis and co-precipitation process. The magnetic PI@LDO composites were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and magnetic properties analysis. The composite materials displayed core-shell structure with flower-like morphology. The magnetic PI@LDO composites were applied to remove tetracycline (TC), 2,4-dichlorophenol (2,4-DCP) and glyphosate (GP) from aqueous solution. The action pH value was ranged from 5 to 9 for TC and GP and 3 to 7 for 2,4-DCP, respectively. Cl- showed a weak competitive adsorption effect to TC, 2, 4-DCP and GP. In addition, the presence of humic acid (HA) could slightly reduce the adsorption capacity of magnetic PI@LDO composites. The adsorption process could be well described by pseudo-second-order model for TC and GP, while pseudo-first-order model for 2,4-DCP. The experimental data of TC and 2,4-DCP could be fitted better with Freundlich model, while that of GP were fitted better with Langmuir model. The adsorptions of TC, 2,4-DCP and GP were both spontaneous and endothermic. The adsorption capacity decreased slightly after adsorption-desorption cycles repeated five times. This study demonstrated that magnetic PI@LDO exhibited great potential to be a mild and cost-effective adsorbent for the removal of various organic contaminants from wastewater.

Enhanced degradation of 2,4-dichlorophenoxyacetic acid by pre-magnetization Fe-C activated persulfate: Influential factors, mechanism and degradation pathway

2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most applicable herbicides in the world, its residue in aquatic environment threatens the human health and ecosystems. In this study, for the first time, inexpensive Fe-C after pre-magnetization (Pre-Fe-C) was used as the heterogeneous catalyst to activate persulfate (PS) for 2,4-D degradation, proving that Pre-Fe-C could significantly improve the degradation and dechlorination. The results indicated the stability and reusability of Pre-Fe-C were much better than pre-magnetization Fe⁰ (Pre-Fe⁰), while the leaching iron ion was lower, indicating that using Pre-Fe-C not only reduced the post-treatment cost, but also enhanced the removal and dechlorination efficiency of 2,4-D. Several important parameters including initial pH, Fe-C dosage, PS concentration affecting 2,4-D degradation and dechlorination by Pre-Fe-C/PS were investigated and compared with that of Fe-C/PS, observing a 1.2-2.7 fold enhancement in the degradation rate of 2,4-D. The Fe-C and Pre-Fe-C were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and SEM-EDX-mapping, suggesting that the content of Fe and O changed more obviously after magnetization. The degradation intermediates, such as chloroquinol, 2-chlorophenol, were identified by a gas chromatography mass spectrometry (GC/MS) and an ion chromatography (IC), and a possible degradation pathway was proposed.

Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-metylphenoxyacetic acid onto activated carbons derived from various lignocellulosic materials

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.

Comparative study on 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol removal from aqueous solutions via ozonation, photocatalysis and non-thermal plasma using a planar falling film reactor

Ozonation and advanced oxidation processes based on photocatalysis (P.C.) and non-thermal plasma generated in a dielectric barrier discharge (DBD) in different gas atmospheres were compared for the degradation and mineralization of 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) in aqueous solutions, using a planar falling film reactor with comparable design. The energetic yields (G₅₀) as measure of the efficiencies of the different methods are for 2,4-D in the order DBD/Ar-Fenton>ozonation>DBD/Ar>P.C.ozonation>DBD/Ar:O₂≫DBD/Air>P.C.oxidation. For 2,4-DCP the order is ozonation≫DBD/Ar-Fenton>P.C.ozonation>DBD/Ar>DBD/Ar:O₂≫P.C.oxidation>DBD/Air. The degradation by using ozone is very effective, but it should be noted that the mineralization measured by the total organic carbon (TOC) removal is low. The reason is the formation of stable towards ozone intermediates, especially low chain carboxylic acids. The fate of these intermediates during the degradation with the different methods has been followed and discussed.

Green preparation of a novel red mud@carbon composite and its application for adsorption of 2,4-dichlorophenoxyacetic acid from aqueous solution

This study reports the eco-friendly preparation of a novel composite material consisting of red mud and carbon spheres, denoted as red mud@C composite, and its application for the removal of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from aqueous solution. The preparation route has a green approach because it follows the low-energy consuming one-step hydrothermal process by using starch as a renewable carbon precursor and red mud as a waste from aluminum production industry. Characterization of the red mud@C composite was performed by FT-IR, TGA, SEM, TEM, BET, XRD, and Raman microscopy analyses. The batch adsorption studies revealed that the red mud@C composite has higher 2,4-D adsorption efficiency than those of the red mud and the naked carbon spheres. The maximum removal at initial pH of 3.0 is explained by considering the pKa of 2,4-D and pH of point of zero charge (pH_pzc) of the composite material. The adsorption equilibrium time was 60 min, which followed the pseudo-second-order kinetic model together with intra-particle diffusion model. The isotherm analysis indicated that Freundlich isotherm model better represented the adsorption data, with isotherm parameters of k [15.849 (mg/g) (mg/L)^-1/n ] and n (2.985). The prepared composite is reusable at least 5 cycles of adsorption-desorption with no significant decrease in the adsorption capacity.