Adsorption Of Methylene Blue Dye Research Articles

Production and Characterization of Activated Carbon Derived from Costus Afer Leaves (C. afer) for the Adsorption of Methylene Blue Dye from an Aqueous Solution

In this work, Costus afer leaves (C. after) was utilized as an agricultural waste material for the synthesis of activated carbon (AC) used for the adsorption of methylene blue dye from its aqueous solution. The raw material was prepared, chemically activated using KHCO3 with an impregnation ratio of 1:3, and later carbonized at a temperature of 700℃ in an inert N2 atmosphere for 1hour to produce activated carbon. The proximate analysis of the biomass revealed the percentage of ash content, moisture content, volatile matter, and fixed carbon present in the waste biomass. The raw and activated carbon produced were characterized using various tests such as: Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX), Fourier Transform Infrared-(FTIR) Spectrometry, X-Ray Fluorescence (XRF), and Brunauer-Emmett-Teller (BET). The results revealed that the SBET of the biomass increased from 400m2/g to 600m2/g after activation. Adsorption studies were carried out in batch mode to determine the influencing factors of adsorption with varying adsorbent dosage, contact time, and pH values. The adsorption experiment revealed high adsorption efficiency at an optimum parameter of dosage (0.2g), contact time (10 min), and pH (8) with a 70.58% removal of methylene blue dye. An increase in dosage, contact time, and pH above the optimum parameter leads to a decrease in percentage removal. The adsorption capacity was achieved using adsorption isotherm models like Langmuir and Freundlich. Adsorption of methylene blue validated the Langmuir model with an R2 of 0.999 and a Qm of 11.83 mg/g. These results show that activated carbon prepared from Costus afer leaves constitutes an effective low-cost material for the adsorption of Methylene dye from wastewater.

Kinetic study of adsorption and photocatalytic degradation of methylene blue dye using TiO2 nanoparticles with activated carbon

Abstract Activated carbon (AC) exhibits limited adsorption capacity for pollutants. Conversely, titanium dioxide (TiO2) demonstrates excellent photocatalytic performance, making it a popular choice for pollutant removal. This study investigates the removal of methylene blue (MB) dye from wastewater using AC, TiO2@AC-2, and TiO2@AC-10 samples via adsorption and photocatalysis. The Energy Dispersive analysis of X-rays (EDAX) has confirmed the presence of Ti, C and O in the prepared samples without any impurities. All the diffraction peaks in X-ray diffractograms indicated the presence of pure anatase TiO2 (tetragonal phase) with no evidence of any other phase. Fourier transform infrared spectroscopy (FTIR) analysis identified a peak around 545 cm⁻¹ in the TiO2@AC-2 sample, indicative of O-Ti-O stretching vibrations. This peak shifted to 602 cm⁻¹ in the TiO2@AC-10 sample. Raman spectroscopy confirmed the presence of carbon (D and G bands) at 1310-1347 cm⁻¹ and 1582-1597 cm⁻¹. Additionally, characteristic Raman active bands for anatase TiO2 were observed at 154 cm⁻¹ (Eg), 204 cm⁻¹ (Eg), 398 cm⁻¹ (B1g), 508 cm⁻¹ (A1g), and 628 cm⁻¹ (Eg). N2 adsorption-desorption isotherms revealed a mesoporous structure for all samples (AC, TiO2@AC-2, and TiO2@AC-10) with hysteresis loops, indicating pores ranging from 2 nm to 50 nm in diameter. Reflectance spectra of TiO2@AC-2 and TiO2@AC-10 displayed absorption edges at 368 nm and 385 nm, respectively, corresponding to a direct band gap of approximately 3.22 eV. Subsequently, these prepared samples were effectively employed for the removal of methylene blue (MB) dye from wastewater utilizing both adsorption and photocatalysis method. Under dark conditions, 20 mg/L doses of TiO2@AC-2 and TiO2@AC-10 resulted in 60% and 36% dye adsorption within 60 minutes respectively. In the presence of UV radiation, the degradation of dye was observed to be 74% and 95% by TiO2@AC-2 and TiO2@AC-10 respectively. This observation indicates that TiO2 nanoparticles along with AC leads to enhanced photocatalytic activity. The Langmuir-Hinshelwood model reveals lower rate constants for AC compared to the composite samples. This is likely because AC lacks inherent catalytic activity, requiring UV light to trigger adsorption. Conversely, TiO2@AC-10 exhibits the highest rate constants (K1 = 24.25 × 10-3 min⁻¹ and K2 = 82.71 × 10-3 min⁻¹), aligning with its higher TiO2 content confirmed by EDAX analysis. This suggests a significantly faster photocatalytic rate and superior degradation efficiency, even at a low sample concentration (20 mg/L).

Blended Nephelium lappaceum and Durio zibethinus wastes for activated carbon production via microwave-ZnCl2 activation: optimization for methylene blue dye removal

Herein, this work targets to employ the blended fruit wastes including rambutan (Nephelium lappaceum) peel and durian (Durio zibethinus) seed as a promising precursor to produce activated carbon (RPDSAC). The generation of RPDSAC was accomplished through a rapid and practical procedure (microwave-ZnCl2 activation). To evaluate the adsorptive capabilities of RPDSAC, its efficacy in eliminating methylene blue (MB), a simulated cationic dye, was measured. The Box–Behnken design (BBD) was utilized to optimize the crucial adsorption parameters, namely A: RPDSAC dose (0.02–01 g/100 mL), B: pH (4–10), and C: time (2–6 min). The BBD design determined that the highest level of MB removal (79.4%) was achieved with the condition dosage of RPDSAC at 0.1 g/100 mL, contact time (6 min), and pH (10). The adsorption isotherm data is consistent with the Freundlich concept, and the pseudo-second-order versions adequately describe the kinetic data. The monolayer adsorption capacity (qmax ) of RPDSAC reached 120.4 mg/g at 25 °C. Various adsorption mechanisms are involved in the adsorption of MB dye onto the surface of RPDSAC, including π–π stacking, H-bonding, pore filling, and electrostatic forces. This study exhibits the potential of the RPDSAC as an adsorbent for removal of toxic cationic dye (MB) from contaminated wastewater.

Tailoring electrospun nanocomposite fibers of polylactic acid for seamless methylene blue dye adsorption applications.

The introduction of biopolymers, which are sustainable and green materials, desegregated nature's water purification proficiency with science and technology, opens a new sustainable methodology in water reclamation. In order to introduce an efficacious adsorbent system for MB dye-toxic pollutant, adsorption, providing robust mechanical properties and facile processability, a facile system was introduced via electrospinning utilizing polylactic acid (PLA) and Ti3C2Tx, viz., PMX. The addition of 3 wt.% Ti3C2Tx led to a 3-fold substantial augmentation in the uptake capacity of the membrane from 197.28 to 307 mg/g when the adsorbate concentration was 100 ppm. The adsorption followed a PSO behavior, proposing that the rate-limiting stage is chemisorption and data best fitted to Freundlich isotherm, indicating heterogeneous adsorption sites and multi-layer adsorption. Further, biodegradability was studied by simulating natural environmental conditions where the nanofibers exhibited 42-64% degradation after 270 days. Based on the result with PLA, it is anticipated that the prepared fibrous system will introduce a new perspective as a potential candidate for MB removal from wastewater, opening new directions toward the research and development in wastewater treatment with electrospun biopolymer fibers using waste PLA.

Exploring the potential of olive pomace derived activated charcoal as an efficient adsorbent for methylene blue dye: a comprehensive investigation of isotherms, kinetics, and thermodynamics

Methylene blue (MB) is a heterocyclic aromatic chemical compound used as a dye in various dyeing processes. The accumulation of such an organic compound poses a significant threat to both the environment and human health. Therefore, numerous biological, physical, and chemical processes have been established to remove MB dye, with adsorption being the most predominant dye-based treatment technology. In this context, the aim of this work was to evaluate the adsorption properties of activated carbon derived from olive pomace against methylene blue. To this end, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out to confirm the adsorption of MB on carbon structures. In addition, the effect of contact time, pH, initial dye concentration, adsorbent dose, and temperature on the adsorption efficiency of MB was investigated. On the other hand, kinetic and isothermal models were used to further understand the adsorption mechanism, which showed a good correlation with the pseudo-second-order kinetic model and the Langmuir isotherm. Finally, thermodynamic analysis showed favorable conditions for physisorption, with the process being both endothermic and spontaneous.

Enhanced adsorption capacity of phosphoric acid-modified montmorillonite clay and ground coffee waste-derived carbon-based functional composite beads for the effective removal of methylene blue

Clays, valued for their versatility, serve as economical adsorbents. Recent studies show that physical, thermal, and chemical modifications can enhance their adsorption capacity. In this study, the synthesis of a functional bead comprising phosphoric acid-modified montmorillonite (PMMT) and coffee waste carbon (CWC) and its application for the efficient adsorption of methylene blue (MeB) dye is investigated. A highly flexible and low-cost phyllosilicate, montmorillonite clay, MMT was treated with phosphoric acid to enhance the ionic density, composited with CWC, resulting in improved surface properties thereafter was transformed into easily recoverable bead form through subsequent cross-linking steps. These functional composite beads were characterized using various characterization techniques. As a result, the existing tetrahedral sheets possessed by the MMT having weak bonds between the layers are improved in a way that they can allow molecule exchange for the efficient enhancement of the adsorption capacity of the composite material. Moreover, after the necessary modifications, the adsorbent was found to be mechanically stable, inhibiting secondary pollutions from the use in powder forms while allowing the interlayers favorable for not just cationic but also anionic exchange whilst increasing the specific surface area and pore volume. The surface area was enhanced to 9.93 m2 /g. Following this, maximum adsorption capacity of 489.9mg/g was attained showing a superior removal efficiency for methylene blue dye (>80%). The adsorption equilibrium was analyzed using Freundlich and Langmuir models. The adsorption mechanism aligns with the Langmuir model which encompasses a monolayer adsorption. All in all, this study is anticipated to play a crucial role in the search for adsorbents with multiple functionalities and good structural stability during and after use.

Potential of easily available low-cost raw cotton for the elimination of methylene blue dye from polluted water

This study centered on exploring the adsorptive potential of the raw cotton for methylene blue dye adsorption. Several laboratory experiments conducted to optimize operational factors like pH, concentration of dye, adsorbent dose, contact time, and temperature. Optimized conditions of the study include an adsorbent dose of 0.35 g, pH of 7, an initial dye concentration of 20 ppm with contact time of 30 min at 20 ºC wherein 83% of adsorption take place. The mean values ± standard deviation from triplicate experiments were used to express the results with P < 0.05. The investigational data fit well with the Langmuir isotherm model having R2 of 0.9477 and pseudo second order kinetic model having R2 = 1. The values obtained for adsorption capacities through non-linear models exhibit a significant degree of similarity with those derived from linear models. Thermodynamic study showed a negative ∆G, positive ∆H and increased ∆S values revealing that the reaction was spontaneous and endothermic in nature. The developed method was also tested with tap water which showed 72% of dye removal and subsequent regeneration of the system led to nearly 79% desorption of the dye. Results of the study revealed that additive salts had a minimum effect on the adsorption process. The originality of this study is that no research has been reported till yet, for adsorption of methylene blue by using low-cost raw cotton specifically in its non-modified form.

Decolourization of Methylene Blue by using Eucalyptus Globulus Leaf Powder as a Adsorbent

In the present study, the feasibility of using low-cost adsorbent Eucalyptus Globulus leaf powder for the cationic dyes adsorption from aqueous solutions have been investigated. Batch adsorption studies are conducted to study conducted to the different parameters are adsorbent dosage of 2-20 g/L, initial dye concentration of 50-250 mg /L, Temperature of 293oK, 303 oK and 313 oK on adsorption of methylene blue dye at equilibrium time of 80 minutes respectively and optimal pH of 5.0. The equilibrium data is analysed with isotherm models are Langmuir and Freundlich and kinetic models are Pseudo-first order, Pseudo-second order model. The adsorption equilibrium and kinetic data fitted well to Freundlich isotherm model for methylene blue dye and Pseudo-second order model for methylene blue dyes. The adsorption is an Endothermic and it is energetically favourable adsorption. The result demonstrates that Eucalyptus Globulus leaf powder could be employed as effective and low-cost adsorbent for the removal of methylene blue and from aqueous solutions.

Effect of the Photoreduction Process on the Self-Cleaning and Antibacterial Activity of Au-Doped TiO2 Colloids on Cotton Fabric.

This study aims at understanding the effect of the photoreduction process during the synthesis of gold (Au)-doped TiO2 colloids on the conferred functionalities on cotton fabrics. TiO2/Au and TiO2/Au/SiO2 colloids were synthesized through the sol-gel method with and without undergoing the photoreduction step based on different molar ratios of Au:Ti (0.001 and 0.01) and TiO2/SiO2 (1:1 and 1:2.3). The colloids were applied to cotton fabrics, and the obtained photocatalytic self-cleaning, wet photocatalytic activity, UV protection, and antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria were investigated. The obtained results demonstrated that the photoreduction of Au weakened the self-cleaning effect and reduced the photocatalytic activity of coated fabrics. Also, an excess amount of Au deteriorated the photocatalytic activity under both UV and visible light. The most efficient self-cleaning effect was obtained on fabrics coated with a ternary TiO2/Au/SiO2 colloid containing ionic Au, where it decomposed coffee and red-wine stains after 3 h of illumination. Adding silica (SiO2) made the fabrics superhydrophilic and led to greater methylene blue (MB) dye adsorption, a faster dye degradation pace, and more efficient stain removal. Moreover, the photoreduction process affected the size of Au nanoparticles (NPs), weakened the antibacterial activity of fabrics against both types of tested bacteria, and modestly increased the UV protection. In general, the photoactivity of Au-doped colloids was influenced by the synthesis method, the ionic and metallic states of the Au dopant, the concentration of the Au dopant, and the presence and concentration of silica.

By-product Eucalyptus leaves valorization in the basic dye adsorption: kinetic equilibrium and thermodynamic study

Abstract Algerian Eucalyptus Leaves (AEL), a natural biodegradable adsorbent abundantly available, was used for the removal of methylene blue (MB) dye. The AEL properties for the removal of MB were investigated under different conditions by varying the AEL amount, MB concentration, pH of the solution and the reaction temperature. Scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) techniques have been used to characterize AEL biosorbent. Experimental results showed that the adsorption of MB dye at the concentration of 50 mg L−1 reached to 91 % at pH 10 with a stirring speed of 200 rpm and after 180 min of reaction time. The experimental data were analyzed using the linear forms of different kinetic models (pseudo-first order kinetic model, pseudo-second order kinetic model, and intra-particle diffusion models). The results demonstrated that the adsorption kinetics of MB was consistent with the pseudo-second order model with R 2 value of 0.9969. The isotherm models Langmuir, Freundlich, Dubinin, Elovich, Brunaut Emmet Teller and Temkin models were also investigated to describe the adsorption equilibrium. The results show that the AEL adsorption is in accordance with Temkin isotherm. The thermodynamic study revealed that the adsorption is spontaneous and exothermic. Therefore, as a cheap green adsorbent with high MB adsorption performance, AEL is expected to become one of the best candidate materials for future industrial wastewater treatment.

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.

Carbon encapsulated ZnO nanoplates for efficient removal of organic dyes from aqueous medium by adsorption: Role of organic ligand and calcination temperature

Water pollution by organic dyes poses great challenge to the environment as well as living organisms. Herein, we have fabricated nanoplates of ZnO in carbon matrix by controlled calcination of zinc-metal organic frameworks (Zn-MOFs) and used as adsorbents for efficient removal of organic dyes from water. Zn-MOF of phthalic acid and 5-nitrophthalic acid produced nanoplates of ZnO (ZnO-C and ZnO-NC) in carbon matrix without and with nitrogen doping. The fabricated hybrid nanostructures were characterized using PXRD, FTIR, BET, TGA, HR-SEM, HR-TEM and XPS analysis. Both ZnO-C and ZnO-NC showed high adsorption of cationic dyes (crystal violet (CV), methylene blue (MB) and Rhodamine B (Rh B)) compared to anionic dyes (methyl orange (MO) and Eosin yellow (EY)). Nitrogen doped ZnO-NC exhibited relatively higher percentage of dyes removal (99 %) compared to ZnO-C. Interestingly, ZnO-NC showed high adsorption of MB dye across the pH range from acidic (pH = 3.0) to alkaline (pH = 11.0). The zero-point charge indicated the negative surface charge for ZnO-NC/ZnO-C that facilitated electrostatic interactions between dyes and adsorbents. Adsorption kinetics suggested a pseudo second order model and adsorption isotherm fitted well with the Freundlich model, suggesting heterogenous adsorption with multilayer coverage of dye molecules. The reusability of ZnO-NC showed only slight reduction of adsorption in three successive cycles. Further, ZnO-NC was used as column packing materials for the successful removal of both cationic as well as anionic dyes upon filtration. Thus, the present studies provided insight on the organic ligand structure and calcination temperature of MOFs for transforming them into effective organic dye adsorbent.

Premise setting for sustainable developing adsorption in environmental remediation using graphitic carbon nitride@agar-derived porous carbon composite

In the adsorption process for wastewater treatment, the adsorbent plays an important role. A composite adsorptive material composed of graphitic carbon nitride and agar-derived porous carbon (CNPC) was fabricated from simple precursors (melamine, thiourea, and agar) and through a facile procedure with different melamine and thiourea ratios. Characterization of CNPC proved a successful formation of a porous structure consisting of mesopores and macropores, wherein CNPC holds distinctive electrochemical (lowered resistance and higher specific capacity) and photochemical properties (lowered bandgap to 2.33 eV) thanks to the combination of graphitic carbon nitride (CN) and agar-derived porous carbon (PC). Inheriting the immanent nature, CNPC was subjected to the adsorption of methylene blue (MB) dye in an aqueous solution. The highest adsorption capacity was 133 mg/g for CNPC-4 which was prepared using a melamine to thiourea ratio of 4:4 – equivalent to the removal rate of 53.2 % and following the pseudo-I-order reaction rate. The effect of pH points out that pH 7 and 9 were susceptible to maximum removal and pretreatment is not required while the optimal ratio of 7.5 mg of MB and 30 mg of material was also determined to yield the highest performance. Furthermore, the reusability of the material for three consecutive cycles was evaluated based on two methods pyrolysis at 200 °C and photocatalytic degradation by irradiation under visible light. In general, the photocatalytic regeneration pathway is more ample and efficient than pyrolysis in terms of energy efficiency (saving energy over 10 times) and adsorption capacity stability. As a whole, the construction of accessible regenerative and stable adsorbent could be a venturing step into the sustainable development spearhead for industries.

Theoretical and Experimental Analysis of Hydroxyl and Epoxy Group Effects on Graphene Oxide Properties.

In this study, we analyzed the impact of hydroxyl and epoxy groups on the properties of graphene oxide (GO) for the adsorption of methylene blue (MB) dye from water, addressing the urgent need for effective water purification methods due to industrial pollution. Employing a dual approach, we integrated experimental techniques with theoretical modeling via density functional theory (DFT) to examine the atomic structure of GO and its adsorption capabilities. The methodology encompasses a series of experiments to evaluate the performance of GO in MB dye adsorption under different conditions, including differences in pH, dye concentration, reaction temperature, and contact time, providing a comprehensive view of its effectiveness. Theoretical DFT calculations provide insights into how hydroxyl and epoxy modifications alter the electronic properties of GO, improving adsorption efficiency. The results demonstrate a significant improvement in the dye adsorption capacity of GO, attributed to the interaction between the functional groups and MB molecules. This study not only confirms the potential of GO as a superior adsorbent for water treatment, but also contributes to the optimization of GO-based materials for environmental remediation, highlighting the synergy between experimental observations and theoretical predictions in advances in materials science to improve sustainability.

Investigating the adsorption potential of char derived from waste latex for methylene blue removal

This study presents the adsorption of methylene blue (MB) dye using latex char derived from pyrolysis of latex gloves. The adsorption process was investigated systematically using Response Surface Methodology (RSM) with a Central Composite Design (CCD). The effects of four key variables, namely pH, time, temperature, and adsorbent dosage, were studied using a factorial design enriched with center points and axial points. Experimental data were analyzed using a second-order polynomial regression model to construct a response surface model, which elucidated the relationship between the variables and MB removal efficiency. The study found that the char obtained at 800 °C exhibited the highest adsorption capacity due to its increased carbonization, expanded surface area, and diverse pore structure. Analysis of Variance (ANOVA) confirmed the significance of the quadratic model, with remarkable agreement between predicted and experimental outcomes. Diagnostic plots validated the model's reliability, while 3D contour graphs illustrated the combined effects of variables on MB removal efficiency. Optimization using DoE software identified optimal conditions resulting in a 99% removal efficiency, which closely matched experimental results. Additionally, adsorption isotherms revealed that the Freundlich model best described the adsorption behavior, indicating heterogeneous surface adsorption with multilayer adsorption. This comprehensive study provides valuable insights into the adsorption process of MB dye using latex char, with implications for wastewater treatment and environmental remediation.

Low energy synthesis of crystalline mesoporous aluminosilicate consisting of Na-P1 zeolite derived from coal fly ash

Worldwide every year massive amount of coal fly ash is being generated as by product in the power plants which creates economic, environmental and most importantly health problems. Usually coal fly ash is used in cement production worldwide. At present, in Bangladesh, about 95 % of fly ash remains still unutilized. The alkali activation of fly ash has become a top research topic as it is possible to synthesize low cost and ecologically sound mesoporous zeolite type materials. In the present work, to the best of our knowledge, for the first time in Bangladesh, synthesis and characterization of crystalline mesoporous (H3 type hysteresis) aluminosilicate consisting of Na-P1 zeolite with a high BET specific surface area and a high pore volume from coal fly ash based on hydrothermal alkali activation technique have been successfully done. This product has versatile applications like catalysis, gas separation, water softening, water purification, gas sensing etc. The variable of alkali concentration was studied which has the notable influence on the development of the framework of the pores. The untreated coal fly ash (CFA) and the synthesized modified fly ashes (MFAs) were tested by WDS-XRF, XRD, N2 physisorption, FE-SEM, FT-IR, XPS, EDAX-mapping, particle size analysis and other technologies. The BET specific surface area, total pore volume and average pore diameter of the CFA were only 3 m2/g, 0.01 cc/g and 6.3 nm respectively based on nitrogen gas physisorption technique, whereas, after alkali activation at a specific temperature and time, and then curing, significant and promising increased values of the said parameters of 45 m2/g, 0.11 cc/g and 9.8 nm were obtained respectively. In methylene blue dye adsorption experiment, MFA showed higher adsorption capacity (23.87 mg/g).

Novel Ganga-sand-encapsulated polyaniline granules for effective remediation of textile and pharmaceutical wastewater

ABSTRACT This study presents the use of novel Ganga-sand-encapsulated polyaniline granules for effective remediation of textile and pharmaceutical wastewater. The prepared Ganga-sand-encapsulated polyaniline granules were characterised using scanning electron microscope (morphology) and Fourier transform infrared techniques. The effect of adsorbent dose, contact time, pH and concentration influence on the adsorption performance of Ganga-sand-encapsulated polyaniline granules for the removal of methylene blue dye (textile waste) and doxycycline antibiotic (pharmaceutical waste) was studied. Kinetic and isotherm studies were also carried out to investigate the adsorption process further. The maximum adsorptive removal efficacy of methylene blue and doxycycline was found as 98.2% and 85.1%, respectively, at the optimised condition of adsorbent dose: 8 g/L, time: 120 min, pH: 12 and concentration: 50 ppm. From adsorption kinetics, it was established that the adsorption process followed pseudo-second-order (PSO) rather than pseudo-first-order (PFO). The correlation coefficient values for PFO and PSO models were 0.9012 and 0.9992, respectively, for methylene blue dye adsorption on Ganga-sand-encapsulated polyaniline granules. The adsorption isotherm study established that the adsorption process followed the Langmuir model rather than the Freundlich model. This study found that Ganga-sand-encapsulated polyaniline granules can be a promising adsorbent for textile and pharmaceutical wastewater treatment.

Application of Acid Activated Ouw’s Natural Clay (ONC) on Adsorption of Methylene Blue Dye

The application of natural clay as an adsorbent has been widely used. This is supported by the porous surface texture of the clay. However, some treatments are needed to remove impurities in natural clay before using it as an adsorbent. The common effort is to activate it with acid. This research studied the effect of hydrochloric acid concentration on the adsorption capacity of methylene blue dye. The concentrations of hydrochloric acid used were 2, 3, and 4 M. Characterization was carried out with IR, XRD, and SEM-EDX spectroscopy to see the differences in ONC characters before and after adding hydrochloric acid. The characterization results showed that ONC contained montmorillonite and quartz, and an increase in base distance was directly proportional to the increase in the concentration of hydrochloric acid used. High concentrations of hydrochloric acid caused excessive dealumination and deionization. The dealumination process was supported by IR data where there was a shift in wavenumber in the Al-O stretching vibration region from 796 cm–1 to 794 cm–1; the sharper the vibration in the Si-O region (488-468 cm–1); there was also an increase in the Si/Al ratio of pure ONC from 1.7497 to 2.2970 for 3 M ONC-HCl. The concentration of hydrochloric acid did not significantly affect the capacity of ONC as an adsorbent for methylene blue. The adsorption capacity of pure ONC obtained was 4.97215 mg/g, while for ONC-HCl 3 M was 4.97746 mg/g.

Computational investigations on the performance of transition metal carbide (MXene) for methylene blue dye adsorption and remediation from wastewater

MXenes are receiving a lot of attention as adsorbents for environmental contaminants, due to their distinct characteristics, and the adsorption abilities were toughly influenced by the surface terminal groups. In this research the adsorption ability of free-standing Ti3C2 for methylene blue (MB) dye as a major hazardous contaminant in the watery environment is investigated and compared with the O and OH terminated MXene counterparts using computational material tools. DFT simulations are carried out to explore the structural properties and electronic structures, thermodynamic stability, and adsorption behavior of MB on the considered MXenes surface. The Ti3C2 monolayer is observed to behave as superior adsorbent for MB with strong interaction characteristic which is typical for the chemisorption followed by the Ti3C2(OH)2 and Ti3C2O2 MXenes with hydrogen bonding (strong physisorption) and electrostatics attractions, respectively. Meanwhile the DFTB-MD simulation of MB/MXene in ambient conditions reveals a strong ability of Ti3C2 monolayer in MB adsorption by chemical bond formation between N/C atom of MB and surface Ti atom followed by hydrogen bond formation in MB/Ti3C2(OH)2 system. The superior adsorption behavior of free-standing Ti3C2 monolayer in aqueous solution, make this novel monolayer a promising adsorbent for MB adsorption and removal from watery contaminants. The present findings will be beneficial for the design of suitable nanoadsorbents for remediation of hazardous organic contaminants from wastewater.

Novel mint-stalks derived biochar for the adsorption of methylene blue dye: Effect of operating parameters, adsorption mechanism, kinetics, isotherms, and thermodynamics

The pyrolysis of mint stalks and lemon peels was performed to synthesize mint-stalks (MBC) and lemon-peels (LBC) derived biochars for adsorbing methylene blue (MB). The preparation, characterization, and application of MBC in adsorption have not been reported in the literature. MBC showed higher surface area and carbon content than that of LBC. The removal ratios of MB were 87.5% and 60% within 90 min for MBC and LBC, respectively at pH 7, temperature of 30oC, adsorbent dose of 0.5 g/L, and MB concentration of 5 mg/L. The optimal MBC dose was 1 g/L achieving a removal efficiency of 93.6% at pH 7, temperature of 30oC, contact time of 90 min, and initial dye concentration of 5.0 mg/L. The adsorption efficiency decreased from 98.6% to 31.33% by raising the dye concentration from 3.0 mg/L to 30 mg/L. Further, the increase of adsorbent dose to 10 g/L could achieve 94.2%, 90.3%, 87.6%, and 84.1% removal efficiencies of MB in the case of initial concentrations of 200 mg/L, 300 mg/L, 400 mg/L, and 500 mg/L, respectively. MBC showed high stability in adsorbing MB under five cycles, and the performed analyses after adsorption reaffirmed the stability of MBC. The adsorption mechanism indicated that the adsorption of MB molecules on the biochar's surface was mainly because of the electrostatic interaction, hydrogen bonding, and π-π stacking. Pseudo-second-order and Langmuir models could efficiently describe the adsorption of MB on the prepared biochar. The adsorption process is endothermic and spontaneous based on the adsorption thermodynamics. The proposed adsorption system is promising and can be implemented on a bigger scale. Moreover, the prepared biochar can be implemented in other applications such as photocatalysis, periodate, and persulfate activation-based advanced oxidation processes.