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High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments
Abstract
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. qM 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.
... Notably, the variation in their adsorptive performances is the function of the mode of preparation of the AC, its pore properties, and surface chemistry [61]. In the studies by Amiri et al. [62], Gülen, Arslan [63], and Brito et al. [64], the respective ACs utilized for the adsorption process were obtained via a sequence of carbonization and subsequent activation of the obtained char. Specifically, Amiri et al. [62] carbonized the precursor at 600 • C for 2 h at a heating rate of 10 • C/min and Brito et al. [64] opted for 800 • C for 1 h at a heating rate of 5 • C/min. ...
... In the studies by Amiri et al. [62], Gülen, Arslan [63], and Brito et al. [64], the respective ACs utilized for the adsorption process were obtained via a sequence of carbonization and subsequent activation of the obtained char. Specifically, Amiri et al. [62] carbonized the precursor at 600 • C for 2 h at a heating rate of 10 • C/min and Brito et al. [64] opted for 800 • C for 1 h at a heating rate of 5 • C/min. After obtaining the char, both authors adopted a physical activation approach using steam as the activating agent. ...
... The model describes the equilibrium of adsorption in a broad concentration range applying to both Langmuir an Freundlich features owing to its adaptability [77]. The linear and non-linear form of the Redlich-Peterson isotherm [64,66] and the nonlinear form of Sips model [108] can be represented in Eq. 5-7. ...
Numerous investigations have been conducted to address 2,4-D removal from water via adsorption approach. The present review offers insights into the underlying mechanisms, pinpoint gaps in the knowledge of the process, and offer a perspective for forthcoming inquiries. Notably, the highest adsorption capacity for 2,4-D reaches 556 mg/g, attributed to a metal-organic framework (MOF) based on porous chromium-benzenedicarboxylate. 2,4-D interactions with most adsorbents are usually by electrostatic interactions, hydrogen bonds, van der Waals forces, and π–π interaction. Isotherm modelling for 2,4-D uptake reveals either Langmuir or Freundlich as best-fit depending on whether uptake is monolayer or multilayer. The pseudo-second order kinetic equation effectively modelled the kinetics of uptake, highlighting that the rate of adsorption is contingent upon both the quantity of active sites and the concentration of 2,4-D within the aqueous phase. The thermodynamics modelling reveals that its adsorptive uptake is always spontaneous. Over a wide range of eluents, 2,4-D can be desorbed from the adsorbents back into the aqueous phase and the adsorbents are mostly reusable for over 5 cycles. Future work could explore the economic analysis and scalability of adsorption processes for the removal of 2,4-D.
... A fraction of the pesticides applied to crops can remain in the soil, while a portion can be transported to water resources via drift, runoff, and leaching (Antunes et al., 2010). Therefore, there is a need to develop techniques for the remediation of soil and water contaminated with pesticides, and biochar can be an amendment that potentially reduces the ecotoxicity of these contaminants (Brito et al., 2020;Huang et al., 2018). Biochar is a carbonaceous material produced by the pyrolysis of organic materials at high temperatures (e.g., straw and sugarcane bagasse), whose high surface area increases its sorption potential (Ogura et al., 2021). ...
... In addition to finding high adsorption coefficients (kd = 10.39 L kg −1 ) using 2.5 to 5% (w:w) biochar, the authors, through modeling concluded that biochar decreased the concentrations of studied contaminants in groundwater. Finally, Brito et al. (2020) showed maximum removal of 94.8% when evaluating the sorption of the pesticide 2,4-D using biochar from sugarcane bagasse. The authors pointed out that a high SSA, with a developed micropore structure, are factors that directly influence the sorption of 2,4-D by sugarcane biochar. ...
... In the present study, biochar satisfactorily reduced the availability of pesticides and their metabolites in the soil and decreased their ecotoxicity. Such results agree with those reported by other authors that obtained high sorption efficiency of biochar made from sugarcane (Brito et al., 2020;da Silva et al., 2018da Silva et al., , 2019Huang et al., 2018). These promising results can contribute to future studies that investigate the use of biochar in the remediation of pesticide-contaminated soils, such as (i) the evaluation of different pyrolysis temperatures for the same feedstock that targets an increase in the efficiency of remediation; (ii) the study of the soil profile since pesticides with low mobility can predominantly remain on the topsoil; (iii) tests that consider the analysis of fipronil metabolites, since there is a lack of knowledge regarding their toxic effects on aquatic and terrestrial organisms; and (iv) tests in outdoor mesocosms and field-scale approaches due to the greater complexity of environmental systems and external variables acting in the processes. ...
The intensive use of pesticides causes harmful effects on ecosystems, and remediation techniques can reduce the ecotoxicity of contaminated soils. Sugarcane straw is a feasible feedstock for biochar production, and it is abundant in the ethanol industry. In this sense, this study assessed the application of biochar from sugarcane straw to reduce the ecotoxicity of soils contaminated with the pesticides fipronil and 2,4-D, alone and in a mixture. Tests at the microcosm level (28 days) evaluated the influence of biochar on the terrestrial worm Enchytraeus crypticus and the eudicot plant Eruca sativa L. At the end of the experiment, elutriate solutions were prepared with soil samples to assess responses on E. sativa and on the cladoceran Daphnia similis. Fipronil and 2,4-D decreased the reproduction of E. crypticus in microcosms, particularly on treatments with fipronil. Biochar reduced the ecotoxicity of fipronil in soils, increasing the reproduction of E. crypticus by 43% compared with soils without biochar. However, the control with biochar showed a reproduction reduction of 23% when compared with the control without biochar. In soils with 2,4-D, the germination rates and shoot growth of E. sativa were 2 times greater in biochar-remediated soils compared with untreated soils. Considering the exposure to elutriate, the application of biochar in soils with 2,4-D improved the growth (by 45%) and germination (by 34%) of E. sativa. No effects were identified on D. similis at any exposure scenario. Therefore, sugarcane straw biochar can be a viable alternative for reducing the ecotoxicity of pesticides in soils.
... Estudos voltados para remoção de micropoluentes por meio de técnicas de Adsorção (Nagy et al., 2014;Brito et al., 2020;Thiebault et al., 2016;Mojiri et al., 2019), conforme comentado no Quadro 3, foram identificados, seja por meio de polímero de bagaço-β-ciclodextrina como otimizante, utilização de resíduos de biomassa, GAC, oxidação fotocatalítica utilizando argila montmorilonita SWy-2 como geoabsorvente ou via quitosana magnética reticulada/biochar ativado. Nagy et al. (2014) desenvolveram estudo em escala reduzida por meio de filtro comercial recheado com carvão ativado (tamanho do grão de 0.5-2.4 ...
... mm. Com estudo em batelada, Brito et al. (2020), por meio da utilização de biocarvões ativados produzidos a partir de resíduos de biomassa (bagaço de cana de açúcar, casca de coco e endocarpo de coco babaçu) buscaram remover micropoluentes através de biocarbonos ativados caracterizados por espectroscopia de ressonância magnética nuclear de 13 C no estado sólido, difração de raio-x e microscopia eletrônica de varredura (MEV). Também com experimento em batelada, Thiebault et al. (2016) utilizaram compostos farmacêuticos ativos (PhAC) nas concentrações de 1.0, 0.5 e 0.1 mg/L, para remoção em argilas minerais, para massa total de argila de 50, 200, 300, 500, 700, 800 mg e 1 g, respectivamente, por tempo total de 12 horas, agitadas por 2 horas a 500 rpm em agitador magnético antes e depois de cada adição de argila. ...
... Observou-se que os antibióticos (G08) foram aplicados em 16 técnicas de remoção em estudo de 16 MPE, com registro em 55% desses estudos e taxa de eficiência 90%, com destaque para a ozonização e fotólise (Zhang e Jiang, 2021Pronina et al., 2016Trapido et al.,2014;Petala et al., 2019;Nil et al., 2018;Tiwari et al., 2018;Boucherie et al., 2010;Tomara et al., 2019;Chen et al., 2016;Acero et al., 2010;Liu et al., 2019;Sturini et al., 2015). Sendo estudado em nove artigos do PB, 12 técnicas foram aplicadas para obtenção de eficiência, os herbicidas (G26), englobaram 27 MPE com média 90% em 48.5% das análises e predominância para a técnica de ozonização (Trapido et al., 2014;Brito et al., 2020;Goswami et al., 2019;Stylianou et al., 2015;Boucherie et al., 2010;Chen et al., 2017;Shu et al., 2013;Sanches et al., 2013;Acero et al., 2010). ...
Micropoluentes emergentes (MPE) são substâncias detectadas no meio ambiente, seja água e solo, que podem alterar, de alguma forma, estes sistemas, além da saúde dos ser humano. Os processos de tratamento de água enquadrados como convencionais, geralmente, são ineficientes para remover os contaminantes. Assim, busca-se tecnologias alternativas de remoção efetiva para esse tratamento. Para isso, realizou-se uma revisão sistemática da literatura que objetivou exibir uma perspectiva sobre os MPE considerados elementos dos estudos, assim como técnicas de tratamento aplicadas e eficiências alcançadas, pautada em três plataformas de dados internacionais, com seleção de critérios de aceitação e rejeição fundamentado em protocolo de revisão. O estudo englobou o portifólio bibliográfico composto por 35 artigos primários, com citação de 109 MPE, pertencentes a 39 grupos, expostos a 44 técnicas voltadas ao tratamento. Como resultante dos dados, sintetizou-se estes em um ábaco. Observou-se significativa diversidade de princípios ativos, removidos por múltiplas técnicas de tratamento, necessitando de estudos para incorporação de técnicas que venham atuar associado ao tratamento convencional, de forma viável.
... 2,4-D is the phenoxy or phenoxy-acetic acid herbicide, widely used for controlling broadleaf weeds (Coelho et al., 2020;Ma et al., 2023). Owing to low price, high solubility, high selectivity, and efficiency, 2, 4-D is used to combat weeds in forestry, non-agriculture, and agriculture crops including corn, sugar cane, cotton, soybean, coffee, beans, papaya, and cocoa (Coelho et al., 2020;Ma et al., 2023). ...
... 2,4-D is the phenoxy or phenoxy-acetic acid herbicide, widely used for controlling broadleaf weeds (Coelho et al., 2020;Ma et al., 2023). Owing to low price, high solubility, high selectivity, and efficiency, 2, 4-D is used to combat weeds in forestry, non-agriculture, and agriculture crops including corn, sugar cane, cotton, soybean, coffee, beans, papaya, and cocoa (Coelho et al., 2020;Ma et al., 2023). 2,4-D is a polar molecule, highly soluble in water (900 mg/L) due to the presence of acidic carboxylic acid functional groups (Ma et al., 2023;Mandal et al., 2017). ...
... m 2 /g), Babassu coconut endocarp AC (1068.00 m 2 /g), and mushroom residue AC (798.75 m 2 /g) (Boumaraf et al., 2022;Brito et al., 2020;Fatombi et al., 2020;Herrera-García et al., 2019;Lazarotto et al., 2021;Vinayagam et al., 2023) (Table T1, Supplementary data). In SYP-SAC-15 production, gases emitted through the thermal decomposition of plant biomass penetrate deep inside the cellular structure forming a thinner wall carbonaceous structure with higher surface area and porosity (Smith et al., 2022;Wu et al., 2018). ...
Phenoxyacetic acid herbicides are widely used in agriculture for controlling weeds. These organic compounds are persistent and recalcitrant, often contaminating water and soil. Therefore, we studied five pristine biochars (BCs), and southern yellow pine (SYP) based self-activated carbon (SAC) for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. Among the tested adsorbents, SYP-SAC-15 demonstrated higher (>90%) 2,4-D removal from water. The SYP-SAC-15 was produced using a facile and green route where the biomass pyrolysis gases worked as activating agents creating a highly porous structure with a surface area of 1499.79 m2/g. Different adsorption kinetics and isotherm models were assessed for 2,4-D adsorption on SYP-SAC-15, where the data fitted best to pseudo-second order (R2 > 0.999) and Langmuir (R2 > 0.991) models, respectively. Consequently, the adsorption process was mainly dominated by the chemisorption mechanism with monolayer coverage of SYP-SAC-15 surface with 2,4-D molecules. At the optimum pH of 2, the maximum 2,4-D adsorption capacity of SYP-SAC-15 reached 471.70 mg/g. Furthermore, an increase in the water salinity demonstrated a positive influence on 2,4-D adsorption, whereas humic acid (HA) showed a negative impact on 2,4-D adsorption. The regeneration ability of SYP-SAC-15 showed excellent performance by retaining 71.09% adsorption capability at the seventh adsorption-desorption cycle. Based on the operating pH, surface area, spectroscopic data, kinetics, and isotherm modeling, the adsorption mechanism was speculated. The 2,4-D adsorption on SYP-SAC-15 was mainly governed by pore filling, electrostatic interactions, hydrogen bonding, hydrophobic and π-π interactions.
... The amount of adsorbed pesticide (C s ) was calculated by using the following formula: Cs = (C 0 -C t )⋅V/m, where C 0 is the initial concentration and C t is the pesticide concentrations (mg/L) at a given time; m is the mass of the adsorbent (480 g of modified bentonite or activated carbon; 1200 g in the case of tests performed only with anthracite) and V is the volume of treated water (40 L). Kinetics first-order and second-order models were used to fit the obtained results, as described by Maia Brito et al. [47] and Guo et al. [48]. ...
... Kinetic analysis of the adsorption process was also evaluated by adjusting the values reported using first and second order kinetic models, as described in [47,48]. The results fitted properly to the second order kinetics (Fig.S3), indicating that adsorption rates were controlled by chemical interactions. ...
A low cost bentonite was modified with Fe³⁺ and hexadecyltrimethylammonium (HDTMA) cations and subsequently optimized to be used in small-scale water filter systems. Two types of formulations were assessed: immobilization of modified clays on anthracite particles and their extrusion as pellets using the natural binders, colophony resin and carnauba and bee waxes. The innovation of this work was to assess which clay formulation showed better performance for the adsorption of the pesticides MCPA, tebuconazole and terbuthylazine in a pilot or pre-commercial water filter system. A commercial organoclay (Cloisite 10A®) and activated carbon were also assayed for comparison purposes. The characterization studies showed that the disintegration in water of the formulated clay adsorbents behaved better when formulated with carnauba wax as binder. The adsorption study was performed in a semi-pilot system by treating 40 L of contaminated water with pesticides in a closed circuit for 24 h at 0.8 bar where the formulated clays were placed in a fixed bed configuration with anthracite particles. Pesticide removal varied depending on the type of formulation, the highest removal efficiency (90–100 %) was reached for the immobilized HDTMA-clay on anthracite particles, which showed better pore distribution according to scanning electron microscopy. The values were similar to those rendered by the commercial Cloisite10A® and activated carbon. The outcomes from this work suggested the convenience of using the new formulated adsorbents based on low-cost raw materials in water purification systems, which may open economic possibilities and employment opportunities for rural areas.
... It can be applied either directly to the soil or sprayed on plantations, which facilitates its entry into surface and groundwater, resulting in severe ecological impacts, including plants and fish mortality, drinking water contamination, and bioaccumulation. The presence of 2,4-D in water bodies also poses significant health risks to humans and animals due to its mutagenic and toxic properties, contributing to congenital, respiratory, and kidney diseases, and disrupted urinary and endocrine functions [6,12,13]. ...
Global development has led to the generation of substantial levels of hazardous contaminants, including pesticides, which pose significant environmental risks. Effective elimination of these pollutants is essential, and innovative materials and techniques offer promising solutions. This study examines the modification of natural zeolite (clinoptilolite) and fly ash-based NaA and NaX zeolites with hexadecyltrimethylammonium bromide (CTAB) to create inexpensive adsorbents for removing 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide from water. Detailed characterization of these materials was performed, along with an evaluation of the effects of pH, contact time, temperature, and initial 2,4-D concentration on their sorption capacities. The modified samples exhibited significant changes in elemental composition (e.g., reduced SiO2 and Al2O3 content, presence of Br) and textural properties. The adsorption of the pesticide was found to be an exothermic, spontaneous process of pseudo-second-order kinetics and was consistent with the Langmuir model. The highest sorption capacities were observed for samples modified with 0.05 mol L−1 CTAB, particularly for CliCTAB-0.05.
... Furthermore, the adsorption capacity depends on the compatibility in the size of the ions that will be exchanged and the availability of the biochar cation linked to the surface functional groups. 59,60 Surface precipitation is one of the main mechanisms used to remove inorganic contaminants. The process involves the formation of insoluble mineral precipitates in the solution or on the surface of the adsorbent. ...
Metals, pharmaceuticals, personal care products, pesticides, and dyes constitute contaminants widely detected in aquatic ecosystems. Adsorption is an important technology for addressing these noxious contaminants in water systems. Its widespread employment stems from its uncomplicated design, environmentally benign nature, heightened sensitivity to contaminants, and mechanical robustness. These inherent advantages render it a highly promising solution for such challenges. Within this framework, biochar embodies key physicochemical properties akin to activated carbon, the foremost adsorbent globally recognized for its efficacy in water contaminant removal. Moreover, biochar derives from the repurposing of biomass waste, thereby presenting an opportunity to enhance the value chain of numerous agricultural byproducts across Brazil. Therefore, this review article aims to present the most commonly studied lignocellulosic residues from Brazil as adsorbents, the methods used to convert them into biochar, the factors influencing the adsorption of contaminants on biochar, and their environmental applications. The main results related to lignocellulosic biomass were presented, including sugarcane, soybean, corn, rice, cotton, coffee, açaí, tucumã, coconut, Brazil nut, cupuaçu, nuts, murumuru, orange, cassava, banana, malt, macaúba, and guava. It was concluded that chemical activation is more common than physical activation, especially using ZnCl2. Finally, the materials have been employed for the removal of metals and a few organic contaminants, mainly dyes, from synthetic solutions.
... El uso de coberturas para el control de arvenses es una práctica que genera aportes positivos al suelo, que pueden verse reflejados en el crecimiento del cultivo, además disminuyen el riesgo a incendios, ataque de plagas y/o enfermedades, y reemplazan o disminuyen el uso de herbicidas y agroquímicos (Maia-Brito et al., 2020). ...
Los sistemas de manejo de las arvenses han tenido una importancia capital para la agricultura. Se puede realizar de diversas maneras, lo importante es obtener un buen control con aquellas medidas que resulten más económicas y a su vez practicables. Se realizó un estudio con el objetivo de evaluar el impacto ambiental y económico de dos métodos de control de malezas, el cual fue conducido en áreas de producción comercial de la Unidad Básica de Producción Cañera "Vitalio Acuña" perteneciente a la Unidad Empresarial de Base Dos Ríos de la provincia Santiago de Cuba. Se estudiaron la aplicación total de herbicida preemergente y cobertura inalterada de residuos de cosecha, sobre un diseño en franjas con tres réplicas. La cobertura de arvenses se determinó a los 30, 60 y 90 días después de realizado, fueron calculados los gastos económicos incurridos y se determinó la carga contaminante hacia la atmósfera. A los 90 días los menores porcentaje de cobertura de malezas se obtuvieron en el área de cobertura inalterada de residuos con diferencias significativas. El método de control de arvenses que tuvo el mejor comportamiento desde el punto de vista de control, ambiental y económico fue, la cobertura inalterada de residuos de cosecha. impacto ambiental, malezas, métodos de control. Weed management systems have been of great importance for agriculture. These can be carried out in various ways, the important thing is to obtain a good control with those measures that are most economical and at the same time practicable. A study was carried out to evaluate the environmental and economic impact of two weed control methods. It was conducted in commercial production areas of the sugar cane farm "Vitalio Acuña" belonging to the sugar mill Dos Ríos, of the Santiago de Cuba province. The total application of pre-emergent herbicide and mulching with sugarcane trash were studied in a split-plot design with three replications. Weed coverage was determined 30, 60 and 90 days after the treatments were carried out, in addition, the economic expenses incurred were calculated and the pollutant load into the atmosphere was determined. At 90 days, the lowest percentage of weed coverage was obtained in the area of mulching with sugarcane trash with significant differences. The weed control method that had the best performance from the control, environmental and economic point of view was the mulching with sugarcane trash. Environmental impact, weeds, control methods. INTRODUCCIÓN Los rendimientos agrícolas en la caña de azúcar se ven seriamente afectados por la presencia de las arvenses, que influyen en el desarrollo de las plantas. Los daños pueden ser desde imperceptibles a muy severos y según su biología, distribución, dispersión y persistencia, pueden convertirse en un verdadero problema. Las pérdidas que ocasionan a la producción de caña mundial varían de 35 al 60% y entre el 30 y 40% para plantaciones de planta y soca respectivamente, por lo que constituyen, la segunda causa de los bajos rendimientos agrícolas en Cuba. Su control debe iniciar inmediatamente después de la plantación o la cosecha, para evitar las mayores reducciones de los rendimientos de caña y azúcar (Arboleda-Escobar, 2019).La situación actual de la agricultura cañera en Cuba, requiere de sistemas cada vez más efectivos y económicos, que permita resolver los problemas existentes con un marcado https://cu-id.com/2284/v14n1e05 RESUMEN: Palabras clave: ABSTRACT:
... Brito et al. [77] evaluated the removal efficiency of 2,4-D from water by three ACs from agricultural biomass waste. These materials were prepared using the one-step carbonization/physical activation route, using steam at 800 • C under an argon atmosphere, from sugarcane bagasse, coconut shell, and endocarp from babassu coconut. ...
An overview of different adsorbents, based on agricultural and household waste, for chlorophenoxy herbicides removal from water is presented. Several groups of adsorbents are discussed, taking into account the modification method used on the initial material and the type of final product obtained. The adsorbent characteristics and the conditions of the adsorption measurements are given, and a discussion on the obtained results is presented, along with a theoretical description, following the application of various equations and models. A group of the most effective adsorbents is indicated, based on the analysis of the adsorption capacity, towards 2,4-D and/or MCPA, and the adsorption rate. Some important problems connected with adsorbent utility are discussed, taking into account economic and ecological aspects. Moreover, the effectiveness of the analyzed materials is observed through the analysis of its interactions with other components present in real systems.
... These three models were successfully applied to several adsorption processes [52,53]. Figure 7A shows the equilibrium adsorption isotherm of 2,4-D on AC conducted under optimum operating conditions (AC dosage: 0.5 g L −1 , stirring speed: 300 rpm, equilibrium time: 90 min) at room temperature. ...
This research deals with the elimination of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions by nanofiltration membrane and activated carbon (AC) synthesized from Elaeagnus angustifolia to identify the most effective and sustainable treatment technique. To optimize the adsorption operating parameters, the AC dose, contact time, stirring speed, and initial pH were investigated, and the obtained results were modeled by examining isotherms, kinetics, and thermodynamics. To optimize the nanofiltration treatment, recirculation flow rate, initial pH, initial concentration of 2,4-D, and presence of monovalent and divalent salts were examined. It was found that 2,4-D can be successfully eliminated by AC with a removal efficiency of 96%, an AC dose equal to 0.5 g L⁻¹, a stirring speed of 300 rpm, and a contact time of 90 min. Moreover, the adsorption process fitted well with the Langmuir isotherm and pseudo-second-order models. On the other hand, the nanofiltration treatment shows a high removal efficiency of 97% with a recirculation flow rate of 750 mL min⁻¹, under a transmembrane pressure equal to 6 bar. By comparing the two processes applied in this work, it is clear that nanofiltration is the most suitable treatment technique.
Graphical Abstract
... Moreover, Weber-Morris model was also applied to investigate the adsorption kinetic of 2,4-D with a view to control the nature of the adsorption process. It is evident that the rate limiting step can be considered by both film and intra-particle diffusion for the removal of 2,4-D [43,51]. ...
In this study, a novel binary grafted polydopamine/polyacrylamide onto magnetic sporopollenin (PDA/PAAm@Fe3O4@SP) was synthesized in one step polymerization strategy to investigate its removal performance of 2,4-dichlorophenoxyacetic acid (2,4-D). The response surface methodology (RSM) was applied to evaluate the effects of the process factors including pH (2–8), adsorbent concentration (0.5-2 g/L), initial 2,4-D concentration (Co) (20–80 mg/L), and contact time (30–180 min) for the 2,4-D removal performance. The central composite design (CCD) through RSM was utilized to design the experiments as well as to optimize and model the 2,4-D adsorption process. The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of 2,4-D (R2 = 0.99). The optimum conditions for the maximum 2,4-D removal (88.31%) was achieved at pH of 3.51, adsorbent concentration of 0.75 g/L, Co of 52.85 mg/L, and contact time of 148.53 min. The adsorption kinetic was represented by both Weber-Morris (R2 = 0.99) and pseudo-second-order models (R2 = 0.99). The isotherm for 2,4-D completely fitted the Dubinin-Radushkevich (D-R) and Langmuir models with R2 values of 0.98. The obtained outcomes indicated that the prepared material may be utilized as an alternative adsorbent for the removal of 2,4-D from waterbodies and the RSM method can be utilized as an eco-friendly and low-cost statistical approach for the elimination of 2,4-D.
... In these equations, q e (mg.g-1 ) corresponds to the amount of 2,4-D adsorbed per mass unit of the adsorbent at equilibrium, V (L) is the volume of the solution, m (g) is the adsorbent mass, C o (mg.L À1 ) is the initial concentration of 2,4-D in solution, C e (mg.L À1 ) is the equilibrium concentration of 2,4-D in solution and R (%) is the percentage of removal of 2,4-D. [22] ...
The presence of microcontaminants in the water supply system offers adverse impacts. This study analyzed the performance of two powdered activated carbons (PAC1 and PAC2) in the removal of 2,4-D herbicide in ultrapure water (UW) and natural water (NW) to verify the influence of natural organic matter (NOM) on the adsorptive process. The properties of PAC1 and PAC2 were analyzed by textural analysis, FTIR, TG, pH, XDR, NMR. The specific surface area of PAC2 was lower than PAC1 and PAC2 showed better adsorption capacity in UW (37.04 mg.g-1) and in NW (8.06 mg.g-1). The results of experiments performed in natural water showed that both activated carbons had reduced 2,4-D adsorption capacity in the presence of NOM, since it may compete for the same adsorption sites or block the access of the 2,4-D molecule to the pores of the activated carbon. PAC2 showed a higher mesopores percentage, decreasing the effects caused by NOM in 2,4-D adsorption. The use of activated carbons with varying pore sizes for the removal of microcontaminants is recommended, especially in NW. This result contributes to the choice of the adsorbent type to be applied in water treatment plants.
... High percentages of 2,4-D, glyphosate, trifluralin, and butachlor were removed using chemical oxidation (graphene oxide/TiO) followed by adsorption (Hosseini and Toosi, 2019). Similarly, 83.4% of trifluralin was removed by ozonation after 20 min (Milhome et al., 2018), and 2, 4-D residues were removed using bioadsorbents (Brito et al., 2020). ...
The application of pesticides in agricultural and public health sectors has resulted in substantially contaminated water resources with residues in many countries. Almost no reviews have addressed pesticide residues in drinking water globally; calculated hazard indices for adults, children, and infants; or discussed the potential health risk of pesticides to the human population. The objectives of this article were to summarize advances in research related to pesticide residues in drinking water; conduct health risk assessments by estimating the daily intake of pesticide residues consumed only from drinking water by adults, children, and infants; and summarize options for pesticide removal from water systems. Approximately 113 pesticide residues were found in drinking water samples from 31 countries worldwide. There were 61, 31, and 21 insecticide, herbicide, and fungicide residues, respectively. Four residues were in toxicity class IA, 14 residues were in toxicity class IB, 55 residues were in toxicity class II, 17 residues were in toxicity class III, and 23 residues were in toxicity class IV. The calculated hazard indices (HIs) exceeded the value of one in many cases. The lowest HI value (0.0001) for children was found in Canada, and the highest HI value (30.97) was found in Egypt, suggesting a high potential health risk to adults, children, and infants. The application of advanced oxidation processes (AOPs) showed efficient removal of many pesticide classes. The combination of adsorption followed by biodegradation was shown to be an effective and efficient purification option. In conclusion, the consumption of water contaminated with pesticide residues may pose risks to human health in exposed populations.
In this study, the adsorption of phenoxyacetic acid (PAA) and its chlorinated derivatives, including 4-chlorophenoxyacetic acid (4CPA) and 2,4-dichlorophenoxyacetic acid (2,4-D), on activated carbons (ACs) from corn kernels (AC-K), corn leaves (AC-L), and corn silk (AC-S) were investigated. The adsorption kinetics followed the pseudo-second-order model, and the film diffusion was the rate-limiting step. The adsorption rate increased in the order PAA < 4CPA < 2,4-D and was correlated with the porous structure (mesopore volume) of these ACs. The Langmuir isotherm models best fit the experimental data; PAA was adsorbed least and 2,4-D most preferentially. The observed trend (PAA < 4CPA < 2,4-D) was positively correlated with the molecular weight of the adsorbates and their hydrophobicity while being inversely correlated with their solubility in water. The adsorption for 2,4-D, according to the Langmuir equation, is equal to 2.078, 2.135, and 2.467 mmol/g and SBET 1600, 1720, and 1965 m2/g, respectively. The results for other herbicides showed a similar correlation. The adsorption of phenoxy herbicides was strongly pH-dependent. The ACs produced from corn biomass can be an eco-friendly choice, offering sustainable products that could be used as efficient adsorbents for removing phenoxyacetic herbicides from water.
Five different biomass wastes—orange peel, coffee grounds, cork, almond shell, and peanut shell—were transformed into biochars (BCs) or activated carbons (ACs) to serve as adsorbents and/or ozone catalysts for the removal of recalcitrant water treatment products. Oxalic acid (OXL) was used as a model pollutant due to its known refractory character towards ozone. The obtained materials were characterized by different techniques, namely thermogravimetric analysis, specific surface area measurement by nitrogen adsorption, and elemental analysis. In adsorption experiments, BCs generally outperformed ACs, except for cork-derived materials. Orange peel BC revealed the highest adsorption capacity (Qe = 40 mg g⁻¹), while almond shell BC showed the best cost–benefit ratio at €0.0096 per mg of OXL adsorbed. In terms of catalytic ozonation, only ACs made from cork and coffee grounds presented significant catalytic activity, achieving pollutant removal rates of 72 and 64%, respectively. Among these materials, ACs made from coffee grounds reveal the best cost/benefit ratio with €0.02 per mg of OXL degraded. Despite the cost analysis showing that these materials are not the cheapest options, other aspects rather than the price alone must be considered in the decision-making process for implementation. This study highlights the promising role of biomass wastes as precursors for efficient and eco-friendly water treatment processes, whether as adsorbents following ozone water treatment or as catalysts in the ozonation reaction itself.
Emerging pollutants are a widespread environmental concern, andadsorption represents one of the choices available for the removal of suchcompounds from polluted waters. However, the set‐up of a new adsorption system requiresthe experimental determination of adsorption isotherms and their thoroughmodelling, for the sake of a convenient optimization. In this work, the Campomanesia guazumifolia biomass is adopted as precursor for the synthesis of anew adsorbent and then tested for the adsorption of KTP and 2,4‐D. Theadsorption performances of this biomass are significantly improved through atreatment with sulfuric acid, which allows obtaining higher removal efficiency ofthe target organic molecules. The experimental isotherms are measured at 298 – 328 K and pH 2. An ETAM model is employed for amodeling analysis of the experimental data, for the comprehension of theoccurring adsorption mechanism. Results demonstrated that adsorption of KTP isendothermic and occurs in multilayer with a multimolecular process, in whichthe molecular aggregation can be predicted. On the contrary, the adsorption of 2,4‐D on this functionalized biomass is exothermic. The adsorption energiesresulted to be < 40 kJ mol⁻¹, indicating that physical adsorption forces are involved inthe removal of these organic molecules.
Babassu is a tropical palm native in South and Central America that produces high‐quality oil from its fruit. The babassu oil extraction results in the production of babassu coconut by‐products (BCBs) – epicarp, mesocarp, endocarp, and almond cake. In this study, we utilised bibliometric analysis and literature review to understand and evaluate their potential for food applications. Our analysis revealed a total of 165 studies published between 1945 and 2022 in the Web of Science database. Notably, Brazil emerged as a prominent contributor to research in this field. The babassu epicarp and endocarp were identified as lignocellulosic materials. Although they are not directly consumable, they possess the potential to serve as sustainable sources of bioactive compounds. In contrast, the babassu mesocarp primarily consists of starch, while the babassu cake exhibits a high protein content. These ingredients play pivotal roles in bakery products and plant‐based formulations, respectively. Despite these findings, our investigation uncovered a knowledge gap regarding the assessment of these fractions in the context of food science and nutrition. By addressing this research gap, we aspire to contribute to the exploration and use of the full potential of BCBs, promoting their integration into the food sector.
Several plant residues can be generated during the stages of industrial processing, such as fruit peel, seeds and bagasse, and these can give rise to high-value products. The management and use of this waste is of global interest. The aim of this study was to evaluate the spatio-temporal evolution of scientific knowledge on the reuse of agroindustrial waste generated in Brazil through a scientometric analysis. To this end, a search was performed in the databases Scopus, Scielo, and Web of Science between the years 1991and 2021. The words used as indexers were agribusiness waste, vegetable waste, fruit waste, biomass waste, plant residue, and chemical characterization. The following selection criteria were adopted: search of indexers by title, scientific articles, articles in English and Portuguese, and articles on plant waste generated in Brazil. There was an increase in publications over the years, with a greater number of studies (21.46%) in the chemistry area, addressing mainly the physical-chemical characterization of materials. In Brazil, sugarcane (Saccharum officinarum L.) was the most studied species with a view to reusing its residues. We identified species from highly threatened Brazilian biomes, such as the Atlantic Forest and Cerrado, with the potential for transformation into new materials. The gaps in knowledge, evidenced in this analysis, suggest that more studies should be carried out on residues of native plant species which impact local communities. In particular, studies could focus on applicability in health and cosmetics, which are promising areas for plant materials and still little investigated.
Currently, in different regions of the world, there is a growth on the rate of produced water for each barrel of oil extracted. Among the compounds observed in this water are naphthenic acids (NAs). Efforts to remove NAs from produced water must comply with local legislation and avoid damage to the environment since NAs have great toxicity. This study aimed to investigate the ability of activated carbon from the pericarp of babassu coconut (Atallea speciosa Mart. ex Spreng.) to act as an absorbent of NAs in commercial and natural (offshore) produced waters. The activated carbon was physically and chemically characterized. The maximum adsorption capacity of commercial NAs at equilibrium obtained experimentally was 25 mg g⁻¹. The activated carbon removed both NAs and other contaminants for produced water, as revealed by infrared and NMR techniques. In high-resolution mass spectrometry analysis, the abundance of the acids in the produced water was in the C9 and C10 range, being favorable for the adsorbent with a microporous structure. For the produced water kinetics experiments a maximum amount of adsorbed compounds of 17.91 mg g⁻¹ was reached, and the time to achieve equilibrium was approximately 180 min. Thus, the results show that activated charcoal from babassu coconut pericarp can be used as an adsorbent and can potentially compete with other adsorbents to remove NAs in an aqueous solution. Also, the separation process can be adopted at a low cost on platforms, complementing the operations of hydrocyclones and flotation.
The engineering of a novel biocomposite based on Cerastoderma edule shells doped with copper and alginate (Ce–[email protected]) forming hydrogel beads was used for batch and dynamic adsorption thiabendazole (TBZ) pesticide from water. The prepared biosorbent was analyzed by various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller analysis (BET), and energy dispersive spectroscopy (EDS), thermogravimetric and differential analysis (TGA-DTA). The results of the TBZ batch biosorption by Ce–[email protected] composite showed that the Langmuir model was the most adequate to describe the adsorption process, with a maximum adsorption capacity value of 21.98 mg/g. Moreover, the adsorption kinetics were adjusted by the pseudo-second-order model. The optimal conditions determined by the RSM approach coupled with the CCD design were 100 ppm of initial TBZ concentration, a Ce–[email protected] beads dose of 6 g/L and a contact time of 180 min for maximum removal of 83.42%. On the other hand, the TBZ sorption on a fixed bed of Ce–[email protected] beads was effective at high column height, low effluent flow and low solution concentration. The Thomas model was best fitted to the kinetic data. This study shows the possibility of using this new hybrid biocomposite in the industrial sector to treat large effluent volumes.
In this work, the transformation of soybean industrial bio-residue with limited practical applications, into a multifunctional carbonaceous adsorbent (SBAC) via one-step microwave-irradiation has been succeeded. The surface porosity, chemical compositions, functionalities and surface chemistry were featured by microscopic pore-textural analysis, elemental constitution analysis, morphological characterization and Fourier transform infra-red spectroscopy. The adsorptive performance of SBAC was evaluated in a batch experiment by adopting different classes of water pollutants, specifically methylene blue (MB), acetaminophen and 2,4-dichlorophenoxyacetic acid (2,4-D). The equilibrium uptakes were analyzed with respect to the non-linearized Langmuir, Freundlich and Temkin isotherm equations. The unique features of SBAC, specifically the antimicrobial and antifungal efficacies were examined against gram-positive/negative bacteria and fungi species. An ordered microporous-mesoporous structure of SBAC, with the BET surface area and total pore volume of 1696 m²/g and 0.94 m³/g, respectively, has been achieved. The equilibrium data of MB and acetaminophen were found to be in good agreement with the Langmuir isotherm model, with the monolayer adsorption capacities (Qo) of 434.57 mg/g and 393.31 mg/g, respectively. The adsorptive experiment of 2,4-D was best fitted to the Freundlich isotherm equation, with the Qo of 253.17 mg/g. The regeneration performance of the spent SBAC under microwave-irradiation could maintain at 69.42–79.31%, even after five (5) adsorption-regeneration cycles. SBAC exhibited excellent inhibition efficiencies against gram-positive/negative bacteria and fungi species, with the inhibition zones at 14.0–28.0 mm. This newly developed SBAC appears to be a new powerful candidate for the remediation of different classes of water contaminants, and novel antibacterial and antifungal agents against biological contaminations. The novel concept of “turn waste into wealth” in a cost-effective and energy saving manner for environmental preservation has been successfully accomplished.
The major challenge in utilizing pesticides lies in identifying the precise application that would improve the efficiency of these pesticides and decline their environmental and health hazards at the same time. Such application requires the development of specific formulations that enable controlled, stimuli-responsive release of the pesticides. Gelatin is a relatively cheap material characterized by temperature-sensitivity and abundant amino acid groups, which makes it suitable for the storage and controlled release of pesticides. In this study, gelatin microspheres were prepared by emulsion and cross-linking, then they were loaded with 2,4-dichlorophenoxyacetic acid sodium (2,4-D Na) as a model herbicide. To achieve temperature-tunable release of 2,4-D Na from the microspheres, NH4HCO3 was added to the formulations at different concentrations. The prepared formulations were characterized by SEM, FTIR, and size distribution analyzes, and their drug loading capacities were determined. Based on bioassay experiments, the 2,4-D Na-NH4HCO3-loaded gelatin microspheres can effectively control the spread of dicotyledonous weeds. Therefore, the strategy proposed herein can be used to develop novel, effective herbicide formulations.
The major challenge in utilizing pesticides lies in identifying the precise application that would improve the efficiency of these pesticides and reduce their environmental and health hazards at the same time. Such application requires the development of specific formulations that enable controlled, stimuli-responsive release of the pesticides. Gelatin is a relatively cheap material characterized by temperature-sensitivity and abundant amino acid groups, which makes it suitable for the storage and controlled release of pesticides. In this study, gelatin microspheres were prepared by emulsion and cross-linking, then they were loaded with 2,4-dichlorophenoxyacetic acid sodium (2,4-D Na) as a model herbicide. To achieve temperature-tunable release of 2,4-D Na from the microspheres, NH4HCO3 was added to the formulations at different concentrations. The prepared formulations were characterized by SEM, FTIR, and size distribution analyses, and their drug loading capacities were determined. Based on bioassay experiments, the 2,4-D Na-NH4HCO3-loaded gelatin microspheres can effectively control the spread of dicotyledonous weeds. Therefore, the strategy proposed herein can be used to develop novel, effective herbicide formulations.
The worldwide development of agriculture and industry has resulted in contamination of water bodies by pharmaceuticals, pesticides and other xenobiotics. Even at trace levels of few micrograms per liter in waters, these contaminants induce public health and environmental issues, thus calling for efficient removal methods such as adsorption. Recent adsorption techniques for wastewater treatment involve metal oxide compounds, e.g. Fe2O3, ZnO, Al2O3 and ZnO-MgO, and carbon-based materials such as graphene oxide, activated carbon, carbon nanotubes, and carbon/graphene quantum dots. Here, the small size of metal oxides and the presence various functional groups has allowed higher adsorption efficiencies. Moreover, carbon-based adsorbents exhibit unique properties such as high surface area, high porosity, easy functionalization, low price, and high surface reactivity. Here we review the cytotoxic effects of pharmaceutical drugs and pesticides in terms of human risk and ecotoxicology. We also present remediation techniques involving adsorption on metal oxides and carbon-based materials.
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.
Alternatives for the use of açaí seed have been investigated to remove caffeine from aqueous solutions. The pyrolytic process was conducted under two temperatures and heating rates (400 °C, 10 °C min⁻¹ and 600 ° C, 50 °C min⁻¹), with a vacuum pump coupled operating at 20 kPa and the biochar was activated with K2CO3, resulting in CA-SA 400/10 and CA-SA 600/50. Density, moisture, volatile and ash content were evaluated for biomass, as well as their activated carbons were characterized through elemental, thermogravimetric (TGA) analysis, N2 adsorption and desorption isotherms (BET / BJH), infra red spectroscopy with Fourier transform (FTIR), X-ray diffraction (DRX), scanning electron microscopy (SEM), dispersive energy spectroscopy (EDS) and by the pHZPC method. CA-SA 400/10 and CA-SA 600/50 showed high values of specific area (1150.4 and 929.3 mg L⁻¹), average similar pore diameter (2.55 and 2.66 nm) and a mixture in the structure between amorphous phase and graphitic. The adsorptive study showed that the pseudo-second order model adjusted better to the kinetic data and that intraparticle diffusion is not the only step that limits the process. Quantum chemical parameters were evaluated for caffeine, based on the Density Functional Theory (DFT) calculations, in order to understand its chemical reactivity at the atomic level. The results showed that the use of activated charcoal from açaí seed is a promising material for removing caffeine, and emerges as an inovation for using the tailings.
Scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction were successfully used to observe the location and morphology of the silica phytoliths in biomass-derived carbons and their transformation into SiC and SiO2 particles at high heat treatment temperatures (HTT). The analyses were conducted in chars derived from the endocarp of babassu coconut (EBC), which naturally contains 1.6 wt% of silica in its mineral matter. It was observed that EBC chars with 500–1200 °C HTT present globular echinate SiO2 phytoliths with sizes of 12–16 μm; these phytoliths are mostly concentrated around the surface of the submillimeter char fibers and also in the carbonaceous char matrix. No phytoliths are found in the interior of the char fibers. At 1200 °C HTT, the phytoliths begin to be rounded, and above 1300 °C HTT, most phytoliths decompose and silicon reacts with carbon-forming nanocrystalline β-SiC particles (~ 35 nm crystallite size). Numerous (tens to hundreds) micro- and sub-micro-amorphous or nanostructured SiO2 particles (with sizes predominantly below 2 µm) are then observed at the sites previously occupied by the phytoliths. Few rounded phytoliths survive at 1400 °C HTT, but disappear at higher HTTs (1600–2000 °C). It is likely that the ensembles of micro- and sub-micro-SiO2 particles observed in many sites correspond to the inner remaining part of the original phytoliths, whose most external SiO2 structures (at and near the surface) decompose and take part in the carbothermal reaction for the formation of SiC.
The work highlights preparation of adsorbents using a common agricultural waste, wheat straw (WS) its characterization and adsorption efficacy. After separation of wheat seeds, whole stem and leaves remain as a waste. WS is used for the preparation of two adsorbents by distinct methods [ash by combustion Wheat straw ash (WSA), biochar by pyrolysis i.e. Wheat straw char (WSC)]. The synthesized adsorbents (WSA and WSC) are characterized by scanning electron microscopy, X-ray fluorescence, CHNS (ultimate analysis), Brunauer, Emmett and Teller (BET) surface area technique and Fourier transform infrared technique. XRF analysis confirmed presence of SiO2 (58%), K2O (6.85%), CaO (4.16 %) and P2O5 (1.65 %) in WPA which act as micronutrients to plants, whereas CPC contains carbon along with SiO2 (15%) as major constituent. A progressive increase in BET surface area was noted by change in preparation methods: WSA (37 m2/g) and WSC (96m2/g). In this manuscript, adsorbents prepared using WS were characterized in detail and their adsorptive abilities were investigated using a commonly used herbicide, 2, 4-dichlorophenoxyacetic acid (2,4-D),as a representative. Batch experiments were conducted to study the effect of different operational parameters such as adsorbent dose, initial 2,4-D concentration, contact time and pH. Experimental data were analyzed with Freundlich, Langmuir, and Temkin isotherm models, among which the Langmuir isotherm model showed the best fit. Pseudo-first-order kinetics and pseudo-second-order kinetics were applied to experimental data and pseudo-second-order kinetics showed the best fit. The adsorption capacity of WSA and WSC was found to be 1.89 and 3.02 mg/g, respectively, whereas equilibrium time was found to be 120, and 240 min, respectively. On the basis of adsorption capacity per hectare dose of WSA is recommended for removal of 2,4-D.
Activated carbon adsorbents were produced from particleboard and medium-density fiberboard, industry originated wastes, without value added applications. These materials were characterized, showing a well-developed microporous structure reaching 0.58 cm³/g, and afterwards, their potential application for the removal of phenoxy acetic acids and substituted urea herbicide was evaluated. Studies in liquid phase were conducted in 2,4-dichlorophenoxy acetic acid (2,4-D), 4-chloro-2-methylphenoxy acetic acid (MCPA) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), being the obtained data linearized using the Langmuir and Freundlich equations. Results indicated high removal capabilities for the adsorptives in study, reaching 0.97, 1.37 and 1.87 mmol/g for diuron, 2,4-D, and MCPA respectively, allowing the conclusion that these materials should be studied further, having in mind real life applications.
Adsorption by carbon materials is one of the relatively fast methods in present research, which is widely used in emergency events. The features of this study were mainly involved modification of adsorbent and analysis of the effect of surface structure for the removal of contaminant. Activated carbon fiber (ACF) modified by nitric acid (N-ACF) was studied to determine the adsorption performance for 2,4-dichlorophenoxyacetic acid (2,4-D). Subsequently, influence factors, adsorption isotherm models, kinetics and thermodynamics were investigated in a batch system. Experimental results showed that activated carbon fiber modified by 0.1M nitric acid had a better removal ability to 2,4-D with the removal rate reached 90% at 40mg/L initial concentration. Removal rate of 2,4-D by N-ACF was greatly influenced by pH with the optimum pH at 2, and the adsorption rate was decreased with the increase of pH. The superiority of Langmuir isotherm model in describing adsorption equilibrium was revealed by correlation coefficients R(2) (R(2)≥0.997). Furthermore, adsorption kinetics was well described by pseudo-second-order model. Activation energy (Ea) for adsorption was calculated to be 11.38kJ/mol. The results of thermodynamic showed that ΔG<0, ΔH>0, ΔS>0, indicating adsorption was a spontaneous, endothermic process with randomness increasing. Additionally, surface structure properties of adsorbent were characterized by Scanning Electron Microscope (SEM), Fourier Transform infrared spectroscopy (FTIR), Specific surface area analysis (BET) and Boehm's titration respectively. It turned out that the micropore structure and functional groups on N-ACF all can contribute to the removal of 2,4-D.
Cotton is a common Indian crop grown on a considerable portion of farmland across the country. After separating the useful product (cotton fibers), the other parts of the plant (stalks, leaves, etc.) are discarded as a waste. In most cases, these plant materials are used as source of fuels in boilers or households. Cotton waste when ignited in the presence and absence of air produces cotton plant ash (CPA) and cotton plant char (CPC), respectively. However, CPA and CPC produced pose environmental problems such as safe disposal. Thus, there is an urgent need to characterize the physical and chemical properties of these derivatives and to identify their potential uses. This study highlights the potential utilization of CPA and CPC as adsorbents of 2,4-D. The main components in CPA, namely, CaO and K2O, provide micronutrients to the soil and are thus useful as a biofertilizer. Moreover, low manufacturing cost and higher availability favor the use of CPA as an efficient, low-cost adsorbent as well as a potential source of vital micronutrients. The adsorption capacity of CPA and CPC was tested using 2,4 dichlorophenoxyacetic acid (2,4-D) as the representative herbicide. Experimental data were analyzed by Freundlich and Langmuir adsorption isotherms, and these fitted well with the Langmuir model. The adsorption capacity q0 was found to be 0.64 mg/g for CPA and 3.93 mg/g for CPC. Pseudo-first-order pseudo-second-order and intraparticle diffusion kinetic models were applied to experimental data, and the pseudo second order kinetics model showed best fit for the adsorption of 2,4-D on CPA and CPC. Both CPA and CPC were characterized using proximate analysis, SEM images, BET surface area, XRF, FTIR, and CHNS. The BET surface area was found to be 2 and 109 m2/g, respectively, for CPA and CPC. Adsorption study results indicated that both CPA and CPC are very effective cheap adsorbent for 2,4-D removal.
This work highlights the preparation of adsorbents using a common agricultural waste [groundnut shell (GS)] and their characterization and adsorption efficacy. The study investigates the chemical, physical, mineralogical, and morphological characteristics of three types of adsorbents produced using groundnut shell (GS),according to three distinct methods[ash by combustion (GSA), biochar by pyrolysis (GSC),and activated carbon by chemical activation (GSAC)of bio char (KOH : bio char: 2.5:1)]. The synthesized adsorbents (GSA, GSC, and GSAC) were characterized by scanning electron microscopy (SEM), X-ray fluorescence (XRF), CHNS (ultimate analysis), BET (Benner–Emmer–Teller), and Fourier transform infrared (FTIR) techniques. A progressive increase in BET surface area was noted with the change in preparation methods: GSA (8 m2/g), GSC (43m2/g), and GSAC (709 m2/g).To the best of our knowledge, for the first time ever, adsorbents prepared using GS were characterized in detail and their adsorptive abilities were investigated using a commonly used herbicide, 2, 4-dichlorophenoxyacetic acid (2,4-D),as a representative. Batch experiments were conducted to study the effect of different operational parameters such as adsorbent dose, initial 2,4-D concentration, and contact time. The adsorption capacity of GSA, GSC, and GSAC was found to be 0.87, 3.02, and 250 mg/g, respectively, whereas the equilibrium time was found to be 60, 120, and 240 min, respectively. The adsorption capacity of GSAC (250 mg/g) was found to be comparable with the highest reported values in the literature [langsat empty fruit bunch activated carbon (LEFBAC; 261 mg/g) and pumpkin seed hull (260 mg/g)].
Weed resistance to glyphosate and development of new GM crops tolerant to 2,4-dichlorophenoxyacetic acid (2,4-D) and dicamba is expected to lead to increased use of these herbicides in cropland. The lady beetle, Coleomegilla maculata is an important beneficial insect in cropland that is commonly used as an indicator species in safety evaluations of pesticides. Here, we examined the lethal and non-lethal effects of 2,4-D and dicamba active ingredients and commercial formulations to this lady beetle species, and tested for synergistic effects of the herbicides. Second instars of lady beetles were exposed to an experimental treatment, and their mortality, development, weight, sex ratio, fecundity, and mobility was evaluated. Using similar methods, a dose–response study was conducted on 2,4-D with and without dicamba. The commercial formulation of 2,4-D was highly lethal to lady beetle larvae; the LC90 of this herbicide was 13 % of the label rate. In this case, the “inactive” ingredients were a key driver of the toxicity. Dicamba active ingredient significantly increased lady beetle mortality and reduced their body weight. The commercial formulations of both herbicides reduced the proportion of males in the lady beetle population. The herbicides when used together did not act synergistically in their toxicity toward lady beetles versus when the chemistries were used independently. Our work shows that herbicide formulations can cause both lethal and sublethal effects on non-target, beneficial insects, and these effects are sometimes driven by the “inactive” ingredients. The field-level implications of shifts in weed management practices on insect management programs should receive further attention.
To use an advanced oxidation process system for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), a series of experiments were performed in which the effects of microwave and UV irradiation were evaluated. The decomposition rate of 2,4-D increased with increasing microwave intensity, UV intensity, and the auxiliary oxidant dosage. Excessive addition of some oxidants (H2O2 and O2), however, resulted in the reduction of the decomposition rate. The effect of addition of microwave irradiation was not significant unless the ozone addition was applied together. The decomposition rate constant obtained with microwave irradiation combined with ozone addition was considerably higher than those obtained with the combinations of UV and O3, of UV and photocatalyst, or of microwave, UV and photocatalyst. The rate constant obtained with the combination of microwave, UV, photocatalyst, and ozone was the highest, being 4.5 times that obtained with the microwave, UV and photocatalyst combination and more than 6 times that obtained injection of ozone only. This result suggests that there is a synergy effect when the constituent techniques, i.e., microwave irradiation, UV irradiation, ozone, and photocatalysis are applied together and that the irradiation of microwave can play an important role in the O3-assisted photocatalysis of organic pollutants in water.
This research article presents an in-situ electrosynthesis of aluminum hydroxides by anodic dissolution of sacrificial aluminum anode and their application towards the adsorption of herbicide 2-(2,4-dichloro phenoxy) propanoic acid (2,4-DP) from aqueous solution. Different sacrificial anode material like iron, magnesium, zinc and aluminum are tested and stainless steel is used as the cathode. The optimization of different experimental parameters like current density, pH, temperature and inter-electrode distance on the adsorption of 2,4-DP was carried out. The results showed that the maximum removal efficiency of 93.0 % was achieved with aluminum as sacrificial anode at a current density of 0.10 A.dm-2 and pH of 7.0. The adsorption of 2,4-DP preferably followed the Langmuir adsorption isotherm. The adsorption kinetic studies showed that the adsorption of 2,4-DP was best described using the second-order kinetic model. Thermodynamic parameters indicates that the adsorption of 2,4-DP on aluminum hydroxides was feasible, spontaneous and endothermic.
Laboratory investigations show that rates of adsorption of persistent organic compounds on granular carbon are quite low. Intraparticle diffusion of solute appears to control the rate of uptake, thus the rate is partially a function of the pore size distribution of the adsorbent, of the molecular size and configuration of the solute, and of the relative electrokinetic properties of adsorbate and adsorbent. Systemic factors such as temperature and pH will influence the rates of adsorption; rates increase with increasing temperature and decrease with increasing pH. The effect of initial concentration of solute is of considerable significance, the rate of uptake being a linear function of the square-root of concentration within the range of experimentation. Relative reaction rates also vary reciprocally with the square of the diameter of individual carbon particle for a given weight of carbon. Based on the findings of the research, fluidized-bed operation is suggested as an efficient means of using adsorption for treatment of waters and waste waters.
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.
Syngas was acquired at 500 °C by the combination of hydrothermal pretreatment (HP) and activated carbon catalyst (ACC) in this work. It's found that HP process removed AAEMs and hemicellulose from biomass, which significantly elevated volatiles release and made sugars and mono-phenols as main components in volatiles. Through the reforming via ACC, oxygen-containing groups in sugars and mono-phenols were deprived and contributed to syngas formation. Top-quality syngas was obtained at HRH150 with CO of 66.68% and syngas purity of 71.17%. More importantly, owing to low enough reforming temperature, phenol was the only dominant organic of tar in this study. In addition, HP process endowed bio-chars with elevated porosity. After NaOH activation, activated bio-char (AC) with highest meso-pore ratio was also obtained at AC-HRH150 (BET of 2366.8 m 2 /g). All in all, results above provided a brand-new angle for further poly-generation of biomass resources .
2,4-dichlorophenoxyacetic acid (2,4-D) is a herbicide that is used worldwide in agricultural and urban activities to control pests, reaching natural environments directly or indirectly. The research on 2,4-D toxicology and mutagenicity has advanced rapidly, and for this reason, this review summarizes the available data in Web of Science (WoS) to provide insights into the specific characteristics of 2,4-D toxicity and mutagenicity. Contrary to traditional reviews, this study uses a new method to quantitatively visualize and summarize information about the development of this field. Among all countries, the USA was the most active contributor with the largest publication and centrality, followed by Canada and China. The WoS categories 'Toxicology' and 'Biochemical and Molecular Biology' were the areas of greatest influence. 2,4-D research was strongly related to the keywords glyphosate, atrazine, water and gene expression. The studies trended to be focused on occupational risk, neurotoxicity, resistance or tolerance to herbicides, and to non-target species (especially aquatic ones) and molecular imprinting. In general, the authors have worked collaboratively, with concentrated efforts, allowing important advances in this field. Future research on 2,4-D toxicology and mutagenicity should probably focus on molecular biology, especially gene expression, assessment of exposure in human or other vertebrate bioindicators, and pesticide degradation studies. In summary, this scientometric analysis allowed us to make inferences about global trends in 2,4-D toxicology and mutagenicity, in order to identify tendencies and gaps and thus contribute to future research efforts.
Activated biocarbons (ABs) with high specific surface area were prepared by the one-step methodology using three different agricultural biomass wastes: sugarcane bagasse (SB), coconut shell (CS) and endocarp of babassu coconut (EB). These lignocellulosic precursors are generated in large quantities in Brazil (among other countries) and, due to inappropriate disposal, they can cause several damages to the environment. From these precursors, ABs samples were prepared by a single step carbonization/physical activation (with steam) heat treatment and free of chemicals. This methodology was conducted inside a horizontal furnace under a rigorous argon flow, controlled heating program and water injection rate. The results of textural analysis revealed that the ABs products were mostly microporous with some mesopores, with BET specific surface area values of 547, 991 and 1068 m ² g ⁻¹ for the products derived from SB, CS and EB, respectively. These values were superior when compared with a number of commercial ABs and to other materials prepared using similar precursors and activation methodology reported in the literature. Among the samples investigated in this work, EB was the precursor that originated the best AB in terms of porosity (BET), pointing out to promising applications of this material as a cheap precursor of highly porous adsorbents.
In this study, commercial activated carbons (GAB and CBP) were successfully used for the removal of two phenoxy acetic class-herbicides, 4-chloro-2-methyl phenoxy acetic acid and 2.4-dichlorophenoxy acetic acid (MCPA and 2.4-D) from aqueous solution. The adsorbent materials were characterized, and their equilibrium adsorption capacity was evaluated. The results suggest that the microporous properties of GAB activated carbon enhanced the adsorption capacity, in comparison to CBP carbon. Thus, the increasing in the ionic strength favored the adsorption removal of both pesticides, indicating that electrostatic interactions between the pollutant and the adsorbate surface are governing the adsorption mechanism, but increasing pH values decreased adsorption capacity. Experimental data for equilibrium was analyzed by two models: Langmuir and Freundlich. Finally, computational simulation studies were used to explore both the geometry and energy of the pesticides adsorption.
In recent years, the growth of environmental protection policies has generated an increase in the global demand for activated carbon, the most widely used adsorbent in many industrial sectors, and with good prospects of implementation in others such as energy storage (electrodes in supercapacitors) and agriculture (fertilizer production). This demand is driving by the search for renewable, abundant and low-cost precursor materials, as an alternative to traditional fossil sources. This study investigates the production of activated carbon from barley straw using physical activation method with two different activating agents, carbon dioxide and steam. Experimental tests under different conditions at each stage of the process, carbonization and activation, have been conducted in order to maximize the BET surface area and microporosity of the final product. During the carbonization stage, temperature and heating rate have been found to be the most relevant factors, while activation temperature and hold time played this role during activation. Optimal conditions for the activation stage were obtained at 800 °C and a hold time of 1 h in the case of activation with carbon dioxide and at 700 °C and a hold time of 1 h in the case of activation with steam. The maximum BET surface area and micropore volume achieved by carbon dioxide activation were of 789 m²/g and 0.3268 cm³/g while for steam activation were 552 m²/g and 0.2304 cm³/g, which represent respectively an increase of more than 43% and 42% for the case of activation with carbon dioxide.
This study presents the orange peel activated carbon (OPAC), derived from biowaste precursor (orange peel) by single step pyrolysis method and its application for the adsorption of chlorophenoxyacetic acid herbicides from the water. The OPAC exhibited the surface area of 592.471 m2 g-1, pore volume and pore diameter of 0.242 cc g-1 and 1.301 nm respectively. The adsorption kinetics and thermodynamic equilibrium modelling for all chlorophenoxyacetic acid herbicides were investigated. The various parametric effects such as pH and temperature were evaluated. A pseudo-second-order kinetic model was well fitted for all the herbicides. The Langmuir isotherm was obeyed for all the herbicides and the maximum Langmuir capacity of 574.71 mg g-1 was achieved. The thermodynamic studies revealed that the adsorption increases with increase in temperature. The results shows that the orange peel derived carbon (OPAC) as effective and efficient adsorbent material for the removal of chlorophenoxyacid herbicides from the water.
This present research work investigates the adsorption of hazardous 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP) from water using electrochemically synthesized zinc hydroxide material. In order to compute the conditions of higher adsorption efficiency, the various parameters such as pH, temperature, current density and the concentration of the contaminant, and inter-electrode distance were studied. The obtained results were analysed by modeling studies viz. Langmuir, Freundlich, D-R isotherm, and Temkin isotherms. The Langmuir isotherm confirms that the monolayer adsorption of 2-(2-methyl-4-chlorophenoxy) propionic acid molecule on the surface of zinc hydroxide. The adsorption mechanism was studied by pseudo-first order, second-order, Elovich model Weber and Morris intraparticle diffusion models. The adsorption of MCPP on zinc hydroxide follows the second-order kinetic model. Based on the heat effect of adsorption, the thermodynamic parameter via enthalpy, entropy, and free energy was evaluated. The calculated thermodynamic parameters endorse that the adsorption was endothermic, spontaneous and thermodynamically feasible.
The objective of this study was to synthesize a novel, efficient and economical bio-adsorbent with three dimensions (3D) structure using a direct assembly method for removal of methylene blue (MB) from aqueous solution. The raw materials were corn straw core (CSC) and graphene oxide (GO). The variables that affected adsorption capacity were tested. GO loading could facilitate the removal rate. When 5 wt% GO was added (CSC-5GO), the removal rate was increased by 21.62% compared to pure CSC (64.58%). Furthermore, the adsorption by CSC-5GO fitted pseudo-second-order kinetic model (R² > 0.998) and Temkin model (R² > 0.955). The maximum adsorption capacity was 414.03 mg g⁻¹ for MB at pH = 12, 298 K and MB concentration of 1000 mg L⁻¹. The adsorption thermodynamic test results suggested that the adsorption was a spontaneous, exothermic and randomness decrease process. Furthermore, after five cycles of adsorption-desorption test, the adsorbent removal rate was >90%, which implied that CSC-5GO had an excellent reproducibility.
Herbicides are widely used in farmlands worldwide. However, after their application on farmlands, they accumulate in high amounts in continental and marine waters. Herbicides are endocrine disruptors, and are known to cause toxicity, carcinogenicity and mutagenicity. Besides, they also spoil the taste and odor of water bodies. To prevent these effects, it is necessary to perform an in-depth study on various herbicide removal methods. This review discusses the various methods of herbicide removal from aqueous body, using a commonly used herbicide (2,4-dichlorophenoxyacetic acid) as a representative chemical. This paper includes a systematic tabulated review of all reported removal methods with important parameters and their mechanism. Adsorption, biological degradation, electrochemical treatment, Fenton degradation, oxidation, ozonation and photocatalytic degradation are investigated and compared for removal of 2,4-D. The advantages and disadvantages and the factors influencing selection of the aforementioned processes are discussed.
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.
Activated carbons with well-developed microporosity and containing dispersed nanostructured phosphorus compounds were produced by the chemical activation with H3PO4 of an abundant Brazilian lignocellulosic residue (endocarp of babassu coconut). The chemical nature of the phosphorus-containing species in the produced materials was studied by ¹H, ¹³C and ³¹P solid-state NMR spectroscopy, including 2D ¹H-³¹P correlation experiments and the use of ¹H homonuclear decoupling. With this approach, it was possible to detect the formation of different phosphorus compounds (mostly containing phosphate groups) embedded into the porous carbon network and exhibiting strong dipolar coupling between ³¹P nuclei and ¹H nuclei in hydrogen atoms bonded to aromatic carbons. The chemical activation with H3PO4 was found to be noticeably effective when starting from the raw lignocellulosic precursor, leading to the achievement of activated carbons with large surface area (up to 1900 m²/g). Due to the natural occurrence of silicon compounds in the endocarp of babassu coconut, the chemical activation with H3PO4 was found to produce silicon pyrophosphate nanocrystals in addition to phosphate groups in non-crystalline clusters dispersed into the porous structure of the activated carbons, suggesting that these materials can be useful for applications as solid phosphoric acid catalysts.
The past decades have seen increasing interest in developing pyrolysis pathways to produce biofuels and bio-based chemicals from lignocellulosic biomass. Pyrolysis is a key stage in other thermochemical conversion processes, such as combustion and gasification. Understanding the reaction mechanisms of biomass pyrolysis will facilitate the process optimization and reactor design of commercial-scale biorefineries. However, the multiscale complexity of the biomass structures and reactions involved in pyrolysis make it challenging to elucidate the mechanism. This article provides a broad review of the state-of-art biomass pyrolysis research. Considering the complexity of the biomass structure, the pyrolysis characteristics of its three major individual components (cellulose, hemicellulose and lignin) are discussed in detail. Recently developed experimental technologies, such as Py-GC–MS/FID, TG-MS/TG-FTIR, in situ spectroscopy, 2D-PCIS, isotopic labeling method, in situ EPR and PIMS have been employed for biomass pyrolysis research, including online monitoring of the evolution of key intermediate products and the qualitative and quantitative measurement of the pyrolysis products. Based on experimental results, many macroscopic kinetic modeling methods with comprehensive mechanism schemes, such as the distributed activation energy model (DAEM), isoconversional method, detailed lumped kinetic model, kinetic Monte Carlo model, have been developed to simulate the mass loss behavior during biomass pyrolysis and to predict the resulting product distribution. Combined with molecular simulations of the elemental reaction routes, an in-depth understanding of the biomass pyrolysis mechanism may be obtained. Aiming to further improve the quality of pyrolysis products, the effects of various catalytic methods and feedstock pretreatment technologies on the pyrolysis behavior are also reviewed. At last, a brief conclusion for the challenge and perspectives of biomass pyrolysis is provided.
This study explores the removal of cephalosporins based antibiotics (CBA) like Cefepime, Cefaclor, Cefuroxime, Cefazolin, Cefixime, Cefalexin and Ceftobiprole from water using Mg(OH)2 synthesised in a facile one-pot process by an electrodissolution method. This process is a novel process, where the adsorbents are generated by in situ, efficient and cost-effective for removing organic pollutants. The adsorption performance of CBA onto the Mg(OH)2 were systematically investigated and experimental results indicated that the Mg(OH)2 showed an excellent adsorption capacity towards CBA due to high specific surface area (60.703 m2g-1) of Mg(OH)2. To optimise the removal efficiency, the effects of contact time, concentration, pH and current density were studied. The adsorption kinetics was modelled by pseudo first and second order kinetics, Elovich and Weber and Morris intraparticle diffusion models. The rate constants for all these kinetic models were calculated and the results show that the second order kinetic models were best fitted to model the kinetic adsorption of CBA. The Langmuir, Freundlich, D–R isotherm and Temkin models were applied to describe the equilibrium isotherm models and the isotherm constants were determined. The adsorption was studied thermodynamically, and the Gibbs free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were calculated. The pilot scale study shows that the process was technologically feasible. The adsorbed Mg(OH)2 were characterized by different techniques, such as FESEM, EDAX, XRD, BET and FTIR measurement.
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.
Graphene oxide (GO) was prepared from commercially available graphite powder. Porous iron oxide ribbons were grown on the surface of GO by solvothermal process. The prepared GO-Fe3O4 nanocomposites are characterized by FT-IR, XRD, VSM, SEM, TEM, Raman spectroscopy, surface functionality and zero point charge studies. The morphology of the iron oxide ribbons grown on GO is demonstrated with TEM at various magnifications. The presence of magnetite nanoparticles is evident from XRD peaks and the magnetization value is found to be 37.28 emu/g. The ratio of intensity of D-peak to G-peak from Raman spectrum is 0.995. The synthesized Graphene oxide-Fe3O4 nanocomposites (GO-Fe3O4) were explored for its surface adsorptive properties by using a model organic compound, 2,4-Dichlorophenoxy acetic acid (2,4-D) from aqueous solution. Batch adsorption studies were performed and the equilibrium data are modelled with Langmuir, Freundlich and Temkin isotherms. The maximum monolayer capacity from Langmuir isotherm is 67.26 mg/g. Kinetic studies were also carried out and the studied adsorption process followed pseudo second-order rate equation. Mechanism of the adsorption process is studied by fitting the data with intraparticle diffusion model and Boyd plot. The studied adsorption process is both by film diffusion and intraparticle diffusion.
Magnetic Fe3O4@graphene nanocomposite (FGN) was synthesized by co-precipitation method. The ability and mechanism of FGN to remove 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution were evaluated. Results showed that the adsorption of 2,4-D on FGN exhibited a strong pH dependence and optimal pH value was 3. Based on density functional theory, π-electron density was enhanced when 2,4-D molecule dissociated into 2,4-D anion, which was beneficial to π-π interaction. The decreased 2,4-D adsorption uptake with increasing pH was mainly caused by electrostatic repulsion. The presence of NaCl (1–20 mmol/L) exerted ignorable influence on 2,4-D removal. Adsorption kinetics and isotherms could be better represented by pseudo-second kinetic and Langmuir adsorption isotherm, respectively. The maximum adsorption capacity was calculated to be 32.31 mg/g at 303.15 K according to Langmuir model. Thermodynamic parameters revealed that the adsorption was an exothermic and spontaneous process. The adsorption of FGN for 2,4-D was mainly driven by π-π interaction between benzene ring of 2,4-D and graphene, which was demonstrated by FTIR spectrums. Fe3O4 contributed to the removal of 2,4-D through electrostatic attraction at low pH. Moreover, FGN still remained certain adsorption capacity following four desorption/regeneration cycles.
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.
In the present study, the adsorptive behaviour of 2,4-D on to nanosized rice husk was evaluated for its effective usage as herbicide carrier. The rice husk waste which is known to cause serious environmental problem, was reduced to nanosize (n-RH) via a mechanical method and was loaded with 2,4-D to serve the purpose. The resulting nanosized rice husk was characterized before and after 2,4-D sorption by scanning electron microscopy (SEM), Fourier transform infrared analysis (FT-IR), dynamic light scattering (DLS) and zeta potential analyser. A series of sorption experiments were conducted for optimizing the n-RH to 2,4-D loading concentration where the weight ratio of 1:0.10 and contact time of 90. min was optimised. The mechanism of 2,4-D sorption onto the n-RH carrier was evaluated using isotherm and kinetic models and was found to be a monolayer mode of sorption following chemisorption process. The sustained release and reduced leaching property of the DnRH nanoformulation was also checked and was found to exhibit better herbicidal activity against the tested target plant (Brassica sp.) compared with that of the commercial 2,4-D, along with increased sustained release of 2,4-D in both water and soil. Based on the environmental friendliness of the carrier, sustained release and enhanced herbicidal activity, the current nanoformulation could be a boon for effective herbicide usage with reduced consumption rate.
Adsorptive removal of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and humic acid (HA) from their single- and binary solutions was investigated using powdered activated carbon. Both pore- and film diffusion coefficients for 2,4-D calculated based on two resistance diffusion kinetics were higher than those found for HA both single- and binary component systems. Similar trend was also observed for the rate constants calculated by applying pseudo-second-order kinetic model. The L-shaped isotherm curves converted into H shaped with an increase in the temperature from 288 to 318 K indicating the complete removal of both solutes in dilute solutions. A synergetic effect was observed in low-concentration region in binary systems; however, the combined action of 2,4-D and HA was found to be antagonistic in concentrated solutions. The experimental equilibrium results in single-component systems were better predicted by the Freundlich than the Langmuir isotherm equation. The extended Freundlich isotherm model fit also quite well to the data obtained from binary solutions. The effects of medium acidity and salinity on 2,4-D and HA adsorption process were also examined. Analysis of the pH-dependent adsorption results using Kurbatov approximation suggested that 2,4-D and HA were mainly adsorbed in molecular form on carbon surfaces rather than in their anionic forms.
This study deals with the removal of nitrate from water by electrocoagulation process using zinc and stainless steel as anode and cathode respectively. The optimizations of various experimental operating parameters like effect of electrolyte pH, current density, temperature, and inter-electrode distance on the removal of nitrate were carried out. The effect of co-existing anions such as carbonate, phosphate, silicate and phosphate was studied on the removal efficiency of nitrate. The results showed that the optimum removal efficiency of 69% was achieved. The maximum removal efficiency was achieved at a current density of 0.1 A dm- 2 and pH of 7.0. First and second-order rate equations were applied to study adsorption kinetics and the adsorption process follows second order kinetics model with good correlation. The Langmuir adsorption isotherm favors monolayer coverage of adsorbed molecules for adsorption nitrate. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the adsorption of nitrate on zinc hydroxide was feasible, spontaneous and endothermic.
We report the preparation and characterization of NaOH-activated carbon of high surface area produced from guava seeds (AC-GS) and its application for amoxicillin (AMX) adsorption. The AC-GS was fully characterized from the N2 adsorption and desorption isotherms, scanning electron microscopy (SEM), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), Boehm titration and pHPZC. Additionally, the kinetics, equilibrium and thermodynamic parameters on the adsorption of AMX onto AC-GS were evaluated. The AC-GS showed BET surface area of 2573.6m2g-1 and microporous features (85%), presenting average pore diameter of 1.96nm, which are suitable for AMX adsorption. The experimental adsorption data were modelled using several kinetic (pseudo-first order, pseudo-second order and Elovich) and isotherm (Freundlich, Langmuir, Redlich-Peterson and Dubinin-Radushkevich) models, which suggested that the adsorption of AMX onto AC-GS occurs predominantly by chemisorption showing a maximum monolayer adsorption capacity of 570.48mgg-1 (pH=4.0; T=25°C), which stands out compared to various adsorbents found in literature. Additionally, the thermodynamic parameters revealed the spontaneity of AMX adsorption (ΔG°=-1.915kJmol-1 at 298K) and its endothermic characteristic (ΔH°=21.33kJmol-1), evidencing the high-efficiency of AC-GS for AMX adsorption and its great potential for organic pollutants removal.
Facilely synthesized zinc hydroxide nanoparticles by electro-dissolution of zinc sacrificial anodes were investigated for the adsorption of thorium (Th4+), uranium (U4+) and cerium (Ce4+) from aqueous solution. Various operating parameters such as effect of pH, current density, temperature, electrode configuration, and electrode spacing on the adsorption efficiency of Th4+, U4+ and Ce4+ were studied. The results showed that the maximum removal efficiency was achieved for Th4+, U4+ and Ce4+ with zinc as anode and stainless steel as cathode at a current density of 0.2 A/dm2 and pH of 7.0. First- and second-order rate equations were applied to study the adsorption kinetics. The adsorption process follows second order kinetics model with good correlation. The Langmuir, Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The experimental adsorption data were fitted to the Langmuir adsorption model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°), and entropy changes (ΔS°) for the adsorption of Th4+, U4+ and Ce4+ were computed to predict the nature of adsorption process. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.
This study demonstrates the use of few-layered graphene oxide nanosheets (GO) as efficient adsorbents for the removal of 17β-Estradiol (E2) from aqueous solutions via strong adsorptive interactions. The adsorption performance of GO was investigated by batch adsorption experiments. Further, adsorption experiments were carried out in the presence of other environmental pollutants to understand external influence on the adsorption of E2 by GO. The result indicated that the maximum adsorption capacity (qm) of GO for E2 obtained from the Langmuir isotherm was 149.4mg/g at 298K and it was the highest values of E2 adsorption compared to that of other adsorbents reported before. Thermodynamic study indicated that the adsorption was a spontaneous process. In addition, the result showed that E2 adsorption on GO was slight affected by the solution pH. The presence of NaCl in the solution facilitated the E2 adsorption and the optimum adsorption capacity was obtained when the NaCl concentration was 0.001M. Moreover, the effect of background electrolyte divalent cations (Mg2+ and Ca2+) was not similar with the monovalent cations (Na+ and K+). While the influence of background electrolyte anions (Cl-, NO3-, SO42-, and PO43-) were not significantly different. The presence of humic acid reduced E2 adsorption on GO at pH 7.0. GO still exhibited excellent adsorption capacity following numerous desorption/adsorption cycles. Besides, both π-π interactions and hydrogen bonds might be responsible for the adsorption of E2 onto GO.
Alizarin red-S-modified amberlite IRA-400 resin (ARSA) was applied for Hg2+ removal from
the aqueous medium which is a highly toxic metal ion. The adsorption process which was
pH dependent, showed maximum adsorption of Hg2+ in the pH range 6–8. ARSA exhibited
good monolayer adsorption capacity for Hg2+ (303.03 mg g−1
) at 25˚C and the isotherm was
well fitted by the Langmuir model. Moreover, the adsorption was evaluated thermodynamically
and the negative values of Gibbs free energy revealed the spontaneity of adsorption
process. The practical applicability of ARSA was explored for the adsorption of Hg2+ metal
ion from a real water sample. The values of ΔH and ΔS were found to be 79.87 kJ mol−1
and 0.26 J mol−1 K−1
, respectively.
The aim of this paper is to give an impression of the work of the recently disbanded IUPAC Sub-Committee on the Characterization of Porous Solids. It provides a brief description of the development, content and philosophy of the Recommendations of the Sub-Committee, to be published in Pure and Applied Chemistry. An outline is given of the terminology required to define a porous solid and of the proposed general guidelines for the selection of the most appropriate methods of characterization.
This chapter describes the various aspects of chemisorption and physical adsorption. The role of surface heterogeneity in chemisorption is still a controversial one; all the data so far analyzed can be explained equally well on the basis of interaction between adsorbed molecules. Physical adsorption, however, represents the scene of a mariage de convenance, because both attractive interaction and heterogeneity are needed to explain the usual isotherm. The Freundlich isotherm, which preceded it, is in general more successful from the empirical standpoint but owing to its lack of a direct derivation from simple principles it is employed rather reluctantly. The Freundlich isotherm has no definite maximum adsorption or saturation value, therefore, when θ approaches a monolayer, the Freundlich equation necessarily breaks down. The whole energy of liquefaction is available, when one isolated molecule is adsorbed on another isolated molecule, and that this energy is unchanged, when the approximately 11 more contacts of the liquid phase are established.
Cu doped Fe3O4 (Fe3O4:Cu) particles were synthesized and applied for arsenic adsorption. As the copper ions increase, the adsorption capacity of Fe3O4:Cu towards As(V) and As(III) increase from 7.32 to 42.90 mg g-1 and from 8.12 to 37.97 mg g-1, respectively. The incorporation of copper decreased the particle size, increased the surface area, porosity and zeta potential, leading to the increase of the adsorption sites and affinity toward negative As(V) species. More importantly, the doped copper ions catalyzed the efficient oxidation of As(III) to As(V) by O2 followed by As(V) adsorption. The Fe3O4:Cu particles also exhibited good performance toward low level arsenic removal, excellent separation, and satisfactory regeneration property. The results indicate Fe3O4:Cu particles possess great potential for both As(III) and As(V) adsorption.
