Adsorption Kinetics Of Dye Research Articles

Low temperature physical activation of raw charcoal for excellent dye adsorption kinetics

The current work illustrates the physical activation of raw charcoal to produce activated carbon (AC) at low temperatures (300 and 500 °C). Prepared ACs are tested for Methylene blue (MB) adsorption experiments at various adsorption conditions (e.g., pH, temperature) and discussed efficiency, kinetics, isotherm models, and adsorption mechanism to determine the optimal adsorption conditions for the removal of MB dye. The results show that the prepared ACs (AC1, AC2 at 300 and 500 °C) efficiently absorb MB and obtain removal efficiency of ∼100 and 83% in 1 h, respectively. When the pseudo-first-order and pseudo-second-order adsorption kinematic models are used to test the adsorption data, the result fits the pseudo-first-order model better. The Freundlich and Langmuir adsorption isotherms are employed to model the isotherm data to get the maximum adsorption capacity (MAC). The MAC for AC1 and AC2 is found to be 39.14 and 40.98 mg/g, respectively. Additionally, MB adsorption has been analyzed using the Temkin and Dubinin–Radushkevich isotherm models, along with the inter-particle diffusion model. The Dubinin–Radushkevich model suggests that MB adsorption is a physical absorption process. The Temkin model showed that the Temkin constant (B) values are positive indicating that the adsorption is exothermic. The inter-particle diffusion model revealed that AC2 displays greater adsorption kinetics consistency due to its larger pore diameter. The results reveal that the Langmuir model captured the data better, demonstrating that monolayer adsorption dominated the absorption process. Additionally, prepared ACs are examined for reuse, and exhibit three cycles of recyclability. As a result, ACs made from oak wood charcoal are an easy affordable way to get rid of MB dye.

Kinetics of the decomposition of reactive black 5 on carbon nanostructured adsorbents

Textile industry effluents, containing vast quantities of toxic organic pollutants and synthetic dyes like Reactive Black 5 (RB5), pose a significant environmental threat. RB5 contamination can harm ecosystems and human health, necessitating effective treatment for water recycling and compliance with quality standards. Traditional methods like filtration often fall short in removing dye chemicals. This study examines the efficiency of nanocarbon-based adsorbents in removing RB5 from textile industry effluents. RB5 solutions at concentrations of 10 µM, 30 µM, 60 µM and 100 µM were investigated and characterized using scanning electron microscopy (SEM) and UV-Vis spectrophotometry. Activated carbon (AC) demonstrated the highest degree of RB5 decomposition, outperforming graphene nanoplatelets (GNPs) and graphene oxide (GO) and offering a promising solution for mitigating textile wastewater pollution. Kinetic studies revealed that RB5 adsorption follows a pseudo-second-order model for all adsorbents. The rate constants were determined using PSO kinetics and they were comparable with the rate constants of prior studies, indicating the applicability of the model to the study of the kinetics of similar dye adsorption and decomposition processes.

Evaluation of optimized conditions for the adsorption of malachite green by SnO2-modified sugarcane bagasse biochar nanocomposites.

This work deals with the synthesis of SnO2-modified sugarcane bagasse biochar (SnO2-SBB) nanocomposites using an impregnation method. XRD, FTIR, SEM, and EDX analyses were used to characterize the produced nanocomposites. Several factors influencing the removal of malachite green from wastewater via the adsorption process were explored to maximize the effectiveness of this process. These factors included the different doses of nanocomposites, pH, temperature, contact time, etc. Studies on batch adsorption were conducted to examine the impact of operational parameters, such as contact time (5 to 30 minutes), adsorbent dosage (5 to 40 mg), pH (2 to 10), and temperature (303, 323, and 353 K), on the percentage of MG dye removal. The adsorption kinetics of MG dye over SnO2-SBB nanocomposites were evaluated with the aid of the Langmuir adsorption isotherm, which provided a good fit (R 2 = 0.99) for pseudo-second-order kinetics. The thermodynamic parameters revealed spontaneous and exothermic adsorption of MG dye over SnO2-SBB nanocomposites. A maximum adsorption capacity (q max) of 52.64 ± 0.03 for 0.3 SnO2-SBB and 73.86 ± 0.05 for 0.5 SnO2-SBB nanocomposites was observed. The newly synthesized SnO2-SBB nanocomposites showed negative zeta potential, which facilitated the adsorption of hydrated cationic dye molecules due to the electrostatic force of attraction.

Remediation of cationic dye from aqueous solution through adsorption utilizing natural Haloxylon salicornicum: An integrated experimental, physical statistics and molecular modeling investigation

Wastewater emanating from declining industrial processes often presents a vexing challenge due to its intricate composition replete with hazardous chemicals. The quest for environmentally sustainable methods to remediate such wastewater has led to the exploration of biomaterials as adsorbents and co-substrates within diverse treatment systems. In this study, we harnessed the abundant and cost-effective adsorbent, Haloxylon salicornicum (HS), as a potent agent for the removal of the pernicious triphenylmethane dye, crystal violet, from aqueous mediums. The adsorbent was characterised using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), while Brunauer-Emmett-Teller (BET) analysis yielded a specific surface area (SBET) of 85.23 m2 g−1, highlighting its advantageous mesoporous structure for adsorption. Comprehensive investigations were conducted across various operational parameters, encompassing initial dye concentration, contact time, HS adsorbent dosage, initial pH, and temperature, with a keen focus on their influence on dye removal efficiency. The results unveiled several key trends, demonstrating that elevated initial dye concentration, prolonged contact time, and higher initial pH levels substantially enhanced the efficiency of dye removal, while ionic strength and temperature exhibited comparatively modest impacts. The kinetics of dye adsorption were rigorously examined, revealing a closer adherence to the pseudo-second-order model in comparison to the PFO model, thereby offering deeper insights into the adsorption dynamics. To further unravel the intricate mechanism underpinning the adsorption of CV on HS, we employed a single-layer model linked to SLMRG. In conjunction, DFT calculations, encompassing COSMO-RS, NCI, Molecular Dynamics (MD) simulations and QTAIM calculations, were applied to probe the interactions between adsorbed CV and the adsorbent-molecules, providing compelling evidence of robust binding interactions. These theoretical insights were subsequently aligned with empirical observations, affirming a significant relation between the theoretical and experimental data. This multifaceted study not only advances our understanding of CV removal using HS but also underscores the robustness of this adsorbent within the context of wastewater treatment. Furthermore, it demonstrates the synergy of empirical investigations and theoretical modeling in unraveling the intricacies of adsorption processes.

Hibiscus leaf petiole derived activated carbon as a potential sorbent for basic green 4 and reactive yellow 15 dye exclusion from aqueous solution

In this study, hibiscus leaf petiole powder is used as a source of carbon to prepare bio-adsorbent. This bio-adsorbent is carbonized by heating and activated thereafter by means of KOH and employed as an alternative adsorbent for Basic Green 4 (BG4) and Reactive Yellow 15 (RY15) dyes. Microstructural features observed from scanning electron microscope (SEM) shows the presence of openings/voids before adsorption and their disappearance after dye adsorption. Fourier transform infrared (FTIR) spectrum shows the shift in peak positions of prominent functional moieties post adsorption endorsing the contact between bio-adsorbent and the dye molecules. The dye adsorption performance of as prepared bio-adsorbent on both the dyes were evaluated by varying the solution pH value between 3 and 9, initial dye concentration, Co between 30–90 mg/L, interaction time, t between 10 and 60 min and adsorbent dose, m between 0.1 and 0.6 g/50 ml. The optimal condition investigated for dye exclusion is computed to be Co = 30 mg/L, t = 40 min, m = 0.3 g for both the dyes. However, the pH values of 9 and 3 respectively were found to be optimum for the removal of BG4 and RY15. Maximum adsorption capacity (qm) for RY15 and BG4 were found to be 41.23 and 61.38 mg/g respectively revealing hibiscus leaf derived activated carbon as an excellent bio-adsorbent. The adsorption kinetics of both dyes followed pseudo-second-order model and the adsorption isotherms is best suited to Langmuir model. These findings confirm that the as prepared bio-adsorbent can be successfully employed as an unconventional adsorbent to remove the toxic dyes from aqueous solutions.

Synthesis and Characterization of Ni based Metal Organic Framework for Enhancing the Removal of Typical Organic Dyes

In this report we present a simple synthesis of a nickel-based metal organic framework (MOF-Ni) at the room temperature using a solution of dimethylformamide (DMF), ethanol and distilled water. The MOF-Ni synthesized in various solvents displayed numerous different properties and advantages over other materials including easy synthesis procedure, good crystallinity, rigidity, and robust chemical stability. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA) were employed to analyze the as-synthesized MOF-Ni. The as-obtained MOF-Ni was used to investigate its adsorption kinetics of red telon dye (RTL) molecules. The effects of time (30–270 min), initial RTL concentration (20–300 mg/L), adsorbent dose (2–50 mg), solution pH (2–12), and temperature (10–80 °C) were investigated. The pseudo-first order rate equation was able to provide the best description of the adsorption kinetics data in the studied time scale. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms, and the isotherm constants were also determined. Dye adsorption turned out to strongly depend on pH, and a low pH was found to increase the amount of adsorbed dyestuff. Compared with other samples, MOF-Ni synthesized in (DMF ​+ ​C2H5OH ​+ ​H2O) had a significantly enhanced adsorption ability for RTL dye. The MOF-Ni high adsorption capacity for RTL dye was attributed to the electrostatic attraction/repulsion phenomena. Moreover, MOF-Ni showed an improved stability at 370, 417, and 423 °C temperatures. The results obtained through our experiments suggested that our porous MOF-Ni microstructures synthesized in DMF ​+ ​C2H5OH ​+ ​H2O have potential applications for treating wastewaters containing RTL dyes.

Mandarin biochar-CO-TETA was utilized for Acid Red 73 dye adsorption from water, and its isotherm and kinetic studies were investigated

Environmental pollution is a major issue today due to the release of dyestuff waste into the environment through industrial wastewater. There is a need for affordable and effective adsorbents to remove harmful dyes from industrial waste. In this study, Mandarin biochar-CO-TETA (MBCOT) adsorbent was prepared and used to remove Acid Red 73 (AR73) dye from aqueous solutions. The efficiency of dye removal was influenced by various factors such as solution pH, contact time, initial AR73 dye concentration, and MBCOT dosage. All experiments were conducted at 25 ± 2 °C, and the optimal pH was determined to be 1.5. The optimal conditions for dye removal were found to be an AR73 dye concentration of 100 mg/L, an MBCOT dosage of 1.5 g/L, and a contact time of 150 min, resulting in a 98.08% removal rate. Various models such as pseudo-first-order (PFO), pseudo-second-order (PSO), film diffusion (FD), and intraparticle diffusion (IPD) were used to determine the adsorption kinetics of AR73 dye onto MBCOT. The results showed that the PSO model best explains the AR73 dye adsorption. Furthermore, Langmuir and Freundlich's isotherm models were studied to explain the adsorption mechanism using experimental data. The adsorption capacities at equilibrium (qe) in eliminating AR73 dye varied from 92.05 to 32.15, 128.9 to 65.39, 129.25 to 91.69, 123.73 to 111.77, and 130.54 to 125.01 mg/g. The maximum adsorption capacity (Qm) was found to be 140.85 mg/g. In conclusion, this study demonstrates that biochar produced from mandarin peels has the potential to be an effective and promising adsorbent for removing AR73 dye from water.

Diffusion and chemical kinetics of methylene blue dye adsorption on silica doped with iron (III) ions

Silica are widely used in catalysis, adsorption, and chromatography. In the last decade, they have been increasingly used in medicine, however, to ensure their biocompatibility, silica need to be modified and the simplest way of such a modification is doping them with iron cations. The article presents a study of the sorption characteristics of silica doped with iron cations. The purpose of the study was to assess the effect of doping silica with iron ions on the kinetics of their adsorption of model sorbate of methylene blue dye. Doped silica were synthesised by the alkoxide sol-gel method at pH=1.5 and pH=5.0 with the introduction of iron cations into the reaction mixture during the hydrolysis of tetraethoxysilane. The iron content in the samples was 1.5, 2.3, and 3.8 at. %. According to the results of X-ray phase analysis, all samples were X-ray amorphous. According to the shape of the isotherms of low-temperature nitrogen adsorption, all samples were classified as microporous. The specific surface area of the samples and the total pore volume decreased slightly with an increase in the iron content in the samples. The adsorption of methylene blue dye was carried out at temperatures of 25, 30, and 35 °C. The kinetic adsorption curves were analysed using the following diffusion kinetics models: Boyd model (external diffusion process) and Weber-Morris model (internal diffusion process). Also, the kinetic data were analysed using kinetic models of pseudo first-order (Lagergren model) and pseudo second-order (Ho and McKay's model). It was established that all samples were characterised by a mixed-diffusion regime of the sorption process. Adsorption kinetics was adequately described by the model of pseudo-second-order.

Cationic Europium-Organic Framework for Chromatographic Column Separation of Ionic Dyes and Stimuli-Responsive Chromic Properties.

A novel 3D europium-based cationic framework (Eu-CMOF) has been constructed solvothermally by employing a viologen derivative as an organic functional building unit. Notably, Eu-CMOF demonstrates its capability as a proficient aqueous-phase ion-exchange host, facilitating the remarkable rapid chromatographic column separation of new coccine and malachite green (NC3-/MG+), as well as new coccine and methylene blue (NC3-/MLB+), in mere 2 to 4 min. Adsorption thermodynamics and kinetics of anionic dyes demonstrate that Eu-CMOF exhibits a higher adsorption capacity for NC3-, as evaluated by the Langmuir model, reaching a value of 173 mg·g-1. The pseudo-second-order rate constant is determined to be 3.84 × 10-3 mg-1·g·min-1. Additionally, Eu-CMOF displays reversible photochromic and amine- and ammonia-induced vapochromic behaviors. Further mechanistic studies reveal that these chromic behaviors are primarily attributed to the generation of free viologen radical stimulated by Xe-light or electron-rich amine/ammonia. This research contributes to the development of advanced materials with applications in rapid chromatographic separation and stimuli-responsive chromic properties, showcasing the potential of Eu-CMOF as a versatile platform for practical applications.

Ultrasonic-Assisted Nitrate Anion Incorporation in Triaminoguanidium Chloride Based Covalent Organic Polymer for Methylene Blue Dye Adsorption.

Terephthalaldehyde-triaminoguanidium chloride covalent organic polymer, Te-TGCl COP can facilely be incorporated with NaNO3 by sonication. Te-TGCl COP incorporated with NaNO3 via ultrasonication adsorbs Methylene Blue (MB) dye. Te-TGCl COP alone shows negligible adsorption capacity for MB, however, when treated with NaNO3, its adsorption capacity emerges slightly. Moreover, ultrasonication of the NaNO3 treated COP, Te-TG-NaNO3 COP shows dramatic increase in its adsorption capacity for MB (qe for Te-TGCl COP ≈0 mg g-1; for Te-TG-NaNO3=17.65 mg g-1). Emergence of MB dye adsorption property in Te-TG-NaNO3 COP composite may be attributed primarily to the electrostatic interaction of MB dye molecules with nitrate anions and the sonochemical effect caused fibrous morphological structure of the adsorbent material. The kinetics of MB dye adsorption onto Te-TG-NaNO3 COP composite exhibits an excellent fit for the pseudo-second order model, suggesting the rate-determining step to be chemisorption. Homogeneous monolayer adsorption of MB dye onto Te-TG-NaNO3 COP composite can be suggested as the Langmuir isotherm model seemed to be fitted well.

Removal of Anionic Methyl Orange Dye from Water by Poly[2-methyl-1H-indole] Derivatives: Investigation of Kinetics and Isotherms of Adsorption.

The adsorption properties toward methyl orange (MO) were evaluated for poly[2-methyl-1H-indole] and its derivatives. The influence of pH, ionic strength of solution, composition, and amount of sorbent on the adsorption of MO dye was investigated; the kinetics of dye adsorption was studied. The adsorption isotherms were analyzed using different models of sorption equilibrium. The presence of chemical interaction between polyindoles and dye was proved by IR and UV spectroscopy methods. The sorption of MO with polymers is realized mainly due to the formation of electrostatic interactions between the sulfogroup of the dye and the imino group of the sorbent. Microphotographs demonstrate the change in the morphology of polyindoles after adsorption, which further confirms the structural changes in the polymers. It was found that the main factors affecting the sorption capacity of the studied materials are the position and nature of substituents in the polymers and the sorption conditions. For example, polyindoles containing a methoxy group in their structure (o-OMePIn and m-OMePIn) have the best sorption activity. These polymers are effective in adsorbing dyes, which means that they can be used in wastewater treatment.

Magnetic, Biocompatible and Biodegradable Carboxymethyl Cellulose‐Based Hydrogel for Cationic Dye Adsorption

AbstractEnsuring the availability of water resources that are both clean and safe is crucial for the preservation of environmental health and the well‐being of humans. Here, we fabricated carboxymethyl cellulose‐based hydrogel nanocomposite using acrylic acid (AA) and 2‐acrylamido‐2‐methylpropane sulfuric acid (AMPS) monomers and Fe3O4 nanoparticles through a free radical crosslinking process for adsorption of dyes from contaminated water. The synthesized nanocomposite hydrogel was characterized using various techniques, including TEM, XRD, FTIR, SEM‐EDS, TGA, and AFM analysis. The swelling capacity of samples in an aqueous medium at multiple pH levels and the presence of different salts were investigated. The adsorption efficiency of methylene blue (MB) and crystal violet (CV), emphasizing the effect of hydrogel concentration and the medium's pH, was studied. It was concluded that the hydrogel sample containing 17 % AMPS and 51 % AA had better swelling capacity and dye removal efficiency. The dye adsorption kinetics data were fitted to pseudo‐first and second‐order kinetic models and the Langmuir and Temkin isotherm models. The maximum adsorption capacity for MB and CV was 53.97 and 53.57 mg/g, respectively. It was revealed that the pseudo‐second‐order kinetic model could best describe adsorption (qe=79.2 mg/g for MB and qe=65.8 mg/g for CV). The intra‐particle diffusion model was found to be the rate‐limiting mechanism of dye adsorption. Thermodynamic studies proposed that the adsorption of MB and CV was spontaneous and endothermic. Additionally, magnetic nanocomposite hydrogel‘s reusability up to four successive cycles further determines its probability of adsorption of dyes from wastewater.

Cyanobacterial pigment adsorbed on TiO2 thin films

The rise in toxicity related to cyanobacterial bloom in freshwater is a current problem that perturbs the trophic chain and risks the ecosystems and human health. Currently, the use of biomass as a potential source of value-added bio-products is an important goal to be achieved in the scope of a sustainable bio-economy. Thus, taking advantage of such bacteria is needed. In the present work, we studied the use of cyanobacterial biomass coming from the Malambo swamp in Colombia as a source of Phycocyanobilin (C-PC) and Chlorophyll-a (Chla) which were used as natural pigments for TiO2 thin films. The concentration obtained of C-PC and Chla extracted were 215 μg/mL and 0.417 μg/mL, respectively. We modeled the natural dye adsorption kinetics on TiO2 thin films through three different models. The Langmuir model showed the best fitting, indicating that the pigment extracted from cyanobacterial biomass can sensitize thin TiO2 film through the formation of a monolayer. Furthermore, the TiO2 films present higher adsorption of C-PC (25.8 mg/g) than Chla (23.3 mg/g). Finally, the adsorption modes were assessed using periodic DFT approximations, which is a remarkable method for studying the structure and properties of solid materials. In terms of binding energies, it was found that the dye shows the strongest interaction with TiO2 through the titanium atom. Thus, the main contribution of this work is directed to explore in deep the natural dye adsorption on TiO2 from both experimental and computational point of view.

Carbon-derived Black Soldier Fly (BSF) Larvae for Adsorption of Methylene Blue Dye: Characterization, Kinetic and Thermodynamic Studies

The most effective substance for effectively adsorbing organic dyes is activated carbon (AC). We looked at the possibility of using Black Soldier Fly (BSF) larvae (Hermetia illucens Genome, MG) as a source for AC in this study. The two unique materials known as MG(300) and MG(500) were produced as a result of the larvae being heated for two hours at 300 and 500°C, respectively. These MG materials were further activated (MGO) using hydrogen peroxide (H2O2), and subsequently utilized for the adsorption of methylene blue (MB) dye. The objectives of this research include: (1) Investigation of the cabonization temperature and activation effects of the MG and MGO towards adsorption capacity; (2) Study of the physico-chemical properties of the adsorbents; (3) Exploration of the adsorptivity of MG and MGO in different parameters, including initial dye concentration, contact time, and temperature; (4) Examination of the kinetic and thermodynamic findings for the MG and MGO towards adsorption capacity. To analyze the obtained carbon, various analytical methods, including FTIR, WDXRF, SEM, and BET, were used. The equilibrium and kinetics of MB dye's adsorption behaviour on the AC were carefully investigated. It's interesting to note that within the first 10 minutes of contact time, all adsorbents demonstrated quick MB adsorption. The dye removal percentage (%) and adsorption capacities (mg×g-1) were measured at 65.7% and 6.33 mg×g⁻¹ for MG(300), 76.5% and 11.07 mg×g⁻¹ for MG(500), 91.1% and 16.41 mg×g⁻¹ for MGO(300), and 96.1% and 17.13 mg×g⁻¹ for MGO(500). Furthermore, the kinetics of dye adsorption using the pseudo-first-order (PFO) and pseudo-second-order (PSO) models were conducted, whereby PSO is the best fit with R2 in the range of 0.949 to 0.999.

Isotherms, kinetics and thermodynamic mechanism of methylene blue dye adsorption on synthesized activated carbon

The treatment of methylene blue (MB) dye wastewater through the adsorption process has been a subject of extensive research. However, a comprehensive understanding of the thermodynamic aspects of dye solution adsorption is lacking. Previous studies have primarily focused on enhancing the adsorption capacity of methylene blue dye. This study aimed to develop an environmentally friendly and cost-effective method for treating methylene blue dye wastewater and to gain insights into the thermodynamics and kinetics of the adsorption process for optimization. An adsorbent with selective methylene blue dye adsorption capabilities was synthesized using rice straw as the precursor. Experimental studies were conducted to investigate the adsorption isotherms and models under various process conditions, aiming to bridge gaps in previous research and enhance the understanding of adsorption mechanisms. Several adsorption isotherm models, including Langmuir, Temkin, Freundlich, and Langmuir–Freundlich, were applied to theoretically describe the adsorption mechanism. Equilibrium thermodynamic results demonstrated that the calculated equilibrium adsorption capacity (qe) aligned well with the experimentally obtained data. These findings of the study provide valuable insights into the thermodynamics and kinetics of methylene blue dye adsorption, with potential applications beyond this specific dye type. The utilization of rice straw as an adsorbent material presents a novel and cost-effective approach for MB dye removal from wastewater.

Surfactant-Assisted synthesis of α-and β-Ag2WO4 modified with Sulphur, Phosphorous, and boron and their applications in wastewater elimination

The surfactant cetyltrimethylammonium bromide (CTAB) was utilized to synthesize a combination of α and β-Ag2WO4 phases, which were accordingly doped with 20 % nonmetallic moieties including phosphorous (p), boron (B), and sulphur (S) via a mild precipitation route. Through characterization tools, information was obtained on surface and elemental concentration distribution, vibration, optical, morphological, and electronic properties. These materials were used as nanoadsorbents and photocatalysts. The S doped Ag2WO4 adsorbent (SAgW) has the best removal results (98.7 %) and it follows the Freundlich model of adsorption isotherm. The kinetics of dye adsorption follow the pseudo-second-order kinetic model. It was shown to achieve removal percentages of 98.6 % for indigo carmine dye (IC) and 98.8 % for methyl red dye (MR), demonstrating that the presence of other dyes has no effect on the removal percentage. AgW (CTAB-assisted synthesis) demonstrated high photocatalytic oxidation of IC at 20 mg/L in only 40 min with first-order kinetics of 0.12 min−1, exceeding that of PAgW by 6 times.

A mechanochemically synthesized Schiff-base engineered 2D mixed-linker MOF for CO2 capture and cationic dye removal.

Developing synthetic strategies for smart materials for the adsorption and separation of toxic chemicals is of great importance. Metal-organic frameworks (MOFs) have been proven to be outstanding adsorbent materials that possess excellent pollutant removal performances in wastewater treatment, including dye recycling. In this work, a neutral Cd(II) based 2D framework with a dual ligand strategy involving -OH functionalized 5-hydroxyisophthalic acid (5-OH-H2IPA) and the amide decorated Schiff base ligand (E)-N'-(pyridin-4-ylmethylene)isonicotinohydrazide (L) has been synthesized by different synthetic routes and characterized by various analytical methods. Thus, crystals of {[Cd(5-OH-IPA)(L)]·CH3OH}n synthesized via diffusion (ADES-7D) and the phase pure bulk product synthesized by conventional reflux (ADES-7C) and the mechanochemical grinding method (ADES-7M) have been established using PXRD data of the respective product showing identical simulated SXRD data to those of ADES-7D. The mechanochemically synthesized ADES-7M possesses a better surface area and CO2 adsorption capability compared to ADES-7C, which is also supported by electron microscopy and particle size measurements. Furthermore, ADES-7 can be used as an efficient adsorbent material for the reversible, selective adsorption (42-99%) and separation of the cationic dyes malachite green (MG), methyl violet (MV), methylene blue (MB), and rhodamine B (RhB) from the mixture of cationic/anionic dyes (methyl orange (MO) and bromocresol green (BCG)) in the aqueous phase. Specifically, ADES-7M possesses better dye capture capability compared to ADES-7C, even in the case of the bigger dye RhB with adsorption differences of 2.38 to 1.01 mg g-1, respectively. The dye adsorption kinetics follows pseudo-second-order kinetics, and the dye adsorption isotherm fits well with the Langmuir/Freundlich adsorption isotherm models. The probable mechanism of adsorption involving the supramolecular interaction between the host MOF and the guest dye has also been proposed.

Controlling Dye Adsorption Kinetics of Graphene Oxide Nano-Sheets via Optimized Oxidation Treatment

Graphene derivatives have demonstrated high potential for various applications, including environmental ones. In this work, graphene oxide nano-sheets were obtained by utilizing a simple chemical method and were tested for water treatment applications. The pollutant adsorption ability of the produced GO was adjusted through a proper oxidation treatment of the graphene nano-sheets. The GO treatment time was systematically varied to control the oxidation level of the graphene nano-sheets and was found to considerably affect the GO’s properties and performance in removing methylene blue. The microscopic studies showed well-exfoliated, few-layer GO nano-sheets. EDS and FTIR techniques were used to probe the presence of oxygen functional groups on the GO surface. The XRD investigations revealed various crystallinity levels of the prepared GO nano-sheets depending on the treatment time. The MB degradation efficiency was maximized by optimizing the GO treatment time. The results showed that the oxidation treatment parameters of GO play a major role in adjusting its properties and can be effectively utilized to boost its performance for water purification applications.

Removal and adsorption kinetics of methylene blue dye by pristine cotton husk bracts (Gossypium hirsutum L.) from agroindustrial waste

In the present study, pristine cotton husk bracts (CHk), an agricultural waste, were successfully employed as an adsorbent for the removal of methylene blue (MB). Batch adsorption experiments were performed as a function of contact time, pH, adsorbent dosage, and initial dye concentration (1–100 mg/L). The experimental results indicate that 20 mg of CHk removed 94% of 20 mg/L dye. Adsorption dye kinetic was analyzed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Furthermore, adsorption data were modeled using the Langmuir, Freundlich, and Temkin isotherms. The kinetic study reveals that the present adsorption process followed a pseudo-second-order, with a qe= 96.56 mg/g and, k2 = 0.109 min−1 at pH 7. Adsorption followed the Langmuir isotherm; the adsorption equilibrium results show a qm = 458.72 mg/g and kL= 0.1622 L/mg, using 20 mg of CHk. The equilibrium parameter value (RL) was observed to be in the interval of 0.0580 to 0.8604. Thermodynamic results indicate that the adsorption mechanism between CHk and MB is spontaneous, exothermic, and with a decrease in the disorder of the adsorbate molecules on the adsorbent surface; at all the temperatures studied (293, 313, 333 K). The use of CHk agroindustrial waste is an ideal option for the treatment of industrial textile effluent in environmental cleansing.

Removal of Methylene Blue by adsorption onto natural and purified clays: Kinetic and thermodynamic study

The present work explores the optimization of experimental conditions for the adsorption of the organic cationic dye methylene blue (MB) by natural and purified clays. The adsorption capacities of samples were determinate to evaluate the efficiency of the purification process. At first, we performed mineralogical and textural analysis of the clay minerals, namely, smooth clay (SC), rigorous clay (RC) and bentonite clay (BC), using various techniques, particularly, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). The characterizations data showed that SC and RC are mainly composed of smectite associated with kaolinite, illite and chlorite. While BC is considered a mesoporous and swelling clay with smectite as the major component. The cation exchange capacity (CEC) was determinate as a 6.30 meq/100 g, 10.69 meq/100 g and 32.64 meq/100 g for SC, RC and RC natural samples respectively. It was noticed that the CEC as well as the specific surface area increase once the impurities associated with the clay are removed. A preliminary study was carried out to elucidate the influence of different parameters; such as contact time, exchangeable cation, solute concentration, temperature and pH on MB adsorption in aqueous solution by clays. The adsorption equilibrium data were analyzed by the linear and nonlinear forms of the Langmuir and Freundlich isotherm models. The Langmuir isotherm fitted well with the experimental data, and the pseudo-second-order kinetic model represented appropriately the adsorption kinetics of MB dye. Moreover, purified clays showed improved adsorption capacity for MB compared to pristine ones: 147.64; 257.69 and 1383 mg/g versus 128.75; 193.4 and 681.85 mg/g for SC, RC and BC respectively. This is attributed to a suitable specific surface, ion exchange capacity and electrostatic interactions as result of a more adequate texture and composition of our treated clays. The thermodynamic studies reveled negative Gibbs free energy change (ΔG) values (from -6.293 to -18.608 KJ.mol−1), positive enthalpy change (ΔH) values, exceeding 40 kJ/mol and positive entropy change (ΔS) values confirming the spontaneous, endothermic and chemisorption nature of the MB adsorption process. The results show that the tested purified clays are efficient in MB removal and can be used as an alternative to the commercial adsorbents, which are often relatively expensive.