Initial Methylene Blue Dye Concentration Research Articles

Box-Behnken design optimization of 2D Ti3C2Tx MXene nanosheets as a microwave-absorbing catalyst for methylene blue dye degradation

The 2D MXene Ti3C2Tx was synthesized from the precursor MAX phase Ti3AlC2 by etching the Al layer using hydrofluoric acid. Different Characterization techniques were employed to investigate the properties of the synthesized Ti3C2Tx. The degradation of methylene blue (MB) dye under microwave irradiation in the presence of the prepared 2D MXene was studied. It was found that the synthesized Ti3C2Tx was an excellent microwave catalyst for MB dye degradation, and results obtained were promising. Using this approach, the dye was almost wholly degraded with a degradation efficiency of 99.85 % in only 10 min without adding any oxidant. The degradation was found to follow the pseudo-first-order kinetic model, and the rate constants obtained varied from 0.10 and reached up to 0.67 min−1. The effect of pH, initial MB concentration and catalyst dosage on the MB dye degradation rate has been studied. It was found that carrying out the reaction at pH values ranging from 2 to 10 did not obviously affect its rate. On the other hand, lower initial MB dye concentrations and higher catalyst dosages significantly increased the degradation rate. The high degradation efficiency was found to be maintained for up to five successive catalytic cycles, ensuring the high stability of the synthesized 2D MXene Ti3C2Tx as a catalyst. Optimization of parameters affecting the degradation process was studied using response surface methodology (RSM). According to the Box-Behnken design, the optimal degradation efficiency (99.92 %) could be achieved by adding 21.24 mg of 2D Ti3C2Tx MXene catalyst and using an initial MB dye concentration of 53.06 ppm (mg/L) during a reaction time of 11.93 min.

Effectiveness of Porous Durian Shell-based Activated Carbon for Methylene Blue Adsorption

In this study, durian shell-based activated carbon (DAC) was produced via chemical activation method by utilising durian shell and sulphuric acid (H2SO4) as the starting material and activating agent, respectively. The incorporation of H2SO4 in the DAC production process resulted an improvement in the surface properties and adsorption capacity of the produced DAC adsorbent. Field emission scanning electron microscopy analysis further showed that the produced DAC possessed a porous structure which was beneficial for dye adsorption application. Under operating conditions of 500°C and 3 hours carbonisation temperature and time, the Brunauer–Emmett–Teller (BET) surface area, total pore volume and BET average pore diameter were measured to be 242.03 m2/g, 0.028 cm3/g and 2.28 nm, respectively. The adsorption performance of the produced DAC was then investigated using methylene blue (MB) as the model adsorbate. The optimum MB dye removal and adsorption capacity were found to be 92.05% and 0.767 mg/g, respectively, with 0.6 g of DAC dosage, 10 ppm of initial MB dye concentration and 15 min of contact time.

Synthesis of iron loaded jackfruit peel biochar through microwave heating as a stable and active heterogenous Fenton catalyst for dye degradation

Iron-loaded biochar derived from jackfruit peels (Fe-JP) was synthesised by pyrolysis in a microwave furnace and iron was loaded onto the peels prior to pyrolysis, facilitated by sonication. The primary objective of the investigation was to examine the degradation process of methylene blue (MB) dye and Acid Red 1 (AR1) dye by the using Fe-JP biochar as a heterogeneous Fenton catalyst. The investigation encompassed an examination of the impact of different operating parameters, such as pH, catalyst dosage, and H2O2 concentration. The synthesised Fenton catalyst underwent characterization using Field Emission scanning electron microscopy (FESEM), Energy Dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques, Fourier transform infrared (FTIR) spectra analysis, Raman spectroscopy, Brunauer-Emmet-Teller (BET) analysis. At a pH of 3, using an initial MB dye concentration of 20 mg/L and initial AR1 dye concentration of 50 mg/L, an 8 mM H2O2 concentration, and a catalyst dose of 2 g/L, the maximum dye removal efficiency reached 96.5 % and 98 % respectively, while the total organic carbon (TOC) removal efficiency reached 68.5 % and 75 % respectively. The observed reaction time under the given experimental conditions was 120 min. The thermal stability of the biochar catalyst was found to be excellent based on the Thermogravimetric analysis (TGA) and Differential Scanning Calorimeter (DSC) studies. The catalysts that were developed demonstrated remarkable durability and negligible leaching of iron, hence enabling their repeated usage in subsequent cycles. The findings of the investigation suggest that the primary mechanism responsible for the degradation of the dye was the surface-based heterogeneous Fenton activity. Additionally, the effect of adsorption on the elimination of colour under varying pH conditions was examined, which had a very low influence in dye degradation (<30 %). The conducted scavenging investigations in the research have indicated the major involvement of hydroxyl radicals (OH) in the degradation process, followed by surface-bound hydroxyl radicals (OHsurface), superoxide radicals (O2−) and ultimately by singlet oxygen radicals (1O2). The study's economic analysis demonstrated that using microwave mode of heating for catalyst synthesis is both green and cost-effective. This observation suggests the possibility of practical implications in the domain of dye degradation.

Green algae Ulva lactuca-derived biochar-sulfur improves the adsorption of methylene blue from water

The present investigation explores the efficacy of green algae Ulva lactuca biochar-sulfur (GABS) modified with H2SO4 and NaHCO3 in adsorbing methylene blue (MB) dye from aqueous solutions. The impact of solution pH, contact duration, GABS dosage, and initial MB dye concentration on the adsorption process are all methodically investigated in this work. To obtain a thorough understanding of the adsorption dynamics, the study makes use of several kinetic models, including pseudo-first order and pseudo-second order models, in addition to isotherm models like Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich. The findings of the study reveal that the adsorption capacity at equilibrium (qe) reaches 303.78 mg/g for a GABS dose of 0.5 g/L and an initial MB dye concentration of 200 mg/L. Notably, the Langmuir isotherm model consistently fits the experimental data across different GABS doses, suggesting homogeneous adsorption onto a monolayer surface. The potential of GABS as an efficient adsorbent for the extraction of MB dye from aqueous solutions is highlighted by this discovery. The study’s use of kinetic and isotherm models provides a robust framework for understanding the intricacies of MB adsorption onto GABS. By elucidating the impact of various variables on the adsorption process, the research contributes valuable insights that can inform the design of efficient wastewater treatment solutions. The comprehensive analysis presented in this study serves as a solid foundation for further research and development in the field of adsorption-based water treatment technologies.

Biosorption of methylene blue by lentil shell on activation with sulfuric acid, formaldehyde, and calcination: kinetic, isotherm, and thermodynamic study

Lentil shell (LS) on modification with sulfuric acid (LSAC), formaldehyde (LSFM), and on calcination (LSCL) were used for the adsorption of methylene blue dye in the present study. The sulfuric acid treated LS adsorbent has shown maximum adsorption. The batch adsorption experiments were studied with the effect of adsorbent dose (10–60 mg), pH (4–10), dye concentration (10–80 mg/L), contact time (10–60 minutes), and temperature (303–333 K). The maximum removal of methylene blue was found at pH 10 with adsorption time 60 minutes. The maximum adsorption capacity is measured for LSAC, LSCL, LSFM, and LS untreated (LSUN) are 49.56, 45.79, 42.24, and 42.09 mg/g respectively for 60 mg adsorbent dose with 60 mg/L of initial methylene blue dye concentration. The biosorbents were characterized with Fourier Transform Infrared spectra, Scanning Electron Microscopy, Transmission Electron Microscopy, BET-N2 adsorption, and Energy Dispersive X-ray analysis. The adsorption isotherm was studied at the temperature of 303, 313, 323, and 333 K. It was found that the higher temperature suitable for maximum adsorption. Langmuir model and Freundlich model were studied from the obtained results for adsorption mechanism. The pseudo second order kinetic model was found suitable for the present adsorption study in comparison with pseudo first order model and intraparticle diffusion model. The data obtained from the present work showed that LS could be employed as an efficient adsorbent for the adsorption of the dye.

Chemically Activated Carbon Synthesized from Rice Husk for Adsorption of Methylene Blue in Polluted Water

Rice husk (RH)-based activated carbons (ACs) were successfully manufactured and used as an adsorbent for the removal of methylene blue (MB) dye from polluted water. ACs were created by impregnating RH char with sodium hydroxide and then activating it for 1 h in a nitrogen environment at various activation temperatures. The characteristics of the obtained ACs were confirmed using Brunauer-Emmett-Teller analysis, scanning electron microscopy, X-ray diffraction analysis, and Fourier-transform infrared spectroscopy. The prepared ACs' pore volume and surface area increased with increasing temperature. The maximum specific surface area of the ACs sample was 729.4 m2/g at 900°C activation temperature. Adsorption was used to remove MB dye from polluted water using the obtained product. The effect of experimental parameters like adsorbent dosage, initial MB dye concentration, contact time, temperature, and pH of the MB dye solution was studied. The synthesized ACs were found to remove 80% of the MB dye under optimal conditions of pH (8), initial concentration (50 mg/L), and contact time (120 min). To represent the fitness of the adsorption data, the Langmuir and Freundlich isotherm models were used. The Langmuir model was found to be the best fit to equilibrium data, with R2 = 0.9972. Similarly, using pseudo first-order and pseudo second-order kinetic models, MB dye adsorption on ACs followed the pseudo-second order with an R2 value of 0.99719. The results show that synthesized RH-based ACs have a high potential for use as an effective adsorbent for removing dye from polluted water.

Sol-Gel Synthesis of ZnO Nanoparticles Using Different Chitosan Sources: Effects on Antibacterial Activity and Photocatalytic Degradation of AZO Dye

Chitosan was used in the sol-gel synthesis of zinc oxide nanoparticles (ZnO NPs) as a capping agent in order to control the size, morphology, optical bandgap, photocatalytic efficiency, and antimicrobial activity. Different chitosan sources were used for the sol-gel synthesis of ZnO NPs, namely chitosan of shrimp shells, crab shells, and Streptomyces griseus bacteria. The photocatalytic efficiency was studied by using the methylene blue (MB) photodegradation test, and the antibacterial activity of the different types of ZnO NPs was investigated by the agar well diffusion technique. The particle size of ZnO NPs varied between 20 and 80 nm, and the band gap energy ranged between 2.7 and 3.2 eV. Due to the different chitosan sources, the ZnO NPs showed different antibacterial activity against Listeria innocua, Bacillus Subtiliis, Staphylococcus Aureus, Salmonella Typhimurium and Pseudomonas Aeruginosa. The ZnO NPs with lower band gap values showed better antibacterial results compared to ZnO NPs with higher band gap values. The MB dye removal of ZnO (shrimp shells), ZnO (crab shells), and ZnO (Streptomyces griseus) reached 60%, 56%, and 44%, respectively, at a contact time of 60 min, a low initial MB dye concentration of 6 × 10−5 M, a solution temperature of 25 °C, and a pH = 7.

Modeling of Batch Organic Dye Adsorption Using Modified Metal‐Organic Framework‐5

AbstractModeling and simulation of batch adsorption of the organic dye methylene blue (MB) by modified metal‐organic framework‐5 (MOF‐5) were investigated. The reported data on the adsorption of MB dye onto Wells‐Dawson acids (H6P2W18O62)‐immobilized MOF‐5 were employed. The film‐pore diffusion model was developed based on external mass transfer coefficient and pore diffusion coefficient that govern the mass transfer process in batch organic dye adsorption. Applying the estimated parameters, the MB adsorption by using modified MOF‐5 was examined to evaluate the effects of MOF‐5 modification, initial dye concentration, temperature, and the dosage of adsorbent. The adsorption capacity of modified MOF‐5 (H6P2W18O62/MOF‐5) was higher than pure MOF‐5. Besides, a lower initial MB dye concentration, higher temperature, and lower adsorbent dosage resulted in higher MB dye adsorption capacity.

Visible Light Photocatalytic Degradation of Methylene Blue Using Polypyrrole-Coated Molybdenum-Based Magnetic Photocatalyst

In this study, Ppy@MoO3@Fe3O4 photocatalyst was used to degrade methylene blue (MB) under visible light irradiation. The optimum catalyst loading, initial MB dye concentration, and solution pH was found to be 500 ppm, 40 ppm, and pH 5, respectively, and resulted to 94.1% MB dye degradation within 90 min irradiation. The mineralization of MB obtained 93% TOC removal. Pseudo-first order kinetic model governed the degradation of MB having a rate constant of 0.027 min-1. Furthermore, it was demonstrated that h+ and O2 species played a critical role in the visible light photocatalytic degradation of MB. The Ppy@MoO3@Fe3O4 photocatalyst also showed better photocatalytic performance on MB dye degradation compared to MoO3@Fe3O4 and controls. Finally, the Ppy@MoO3@Fe3O4 photocatalyst exhibited consistently high performance even after 4 cycles, proving that the as-prepared nanomaterial can be considered as a promising photocatalyst with good photocatalytic activity, stability, and reusability.

Surface Characteristics of Electrospun p-Sulphonated Calix[4]Arene Functionalized Cellulose Acetate Nanofiber and Its Behaviour towards Methylene Blue Adsorption

p-sulphonated calix[4]arene ( p-SOCX) functionalized cellulose acetate/graphene oxide (CA/GO) nanofibers were successfully prepared via the electrospinning technique. The presence of p-SOCX within the fiber matrix was ascertained using Fourier Transform Infrared spectroscopy and Carbon-Hydrogen-Nitrogen-Sulphur elemental analyses. Apparent changes in morphology of the samples were observed under scanning electron microscope where fiber diameters increased with increasing p-SOCX content. Preliminary dye removal test at different pH, dosage, and temperature of functionalized CA/GO nanofiber demonstrates enhanced adsorption capacity of methylene blue in presence of p-SOCX compared to pristine CA nanofiber and CA/GO nanofiber at an optimum pH 8. The highest removal efficiency obtained was 88.84% with initial methylene blue dye concentration of 10 mg/L, adsorbent dosage of 20 mg/10 mL, contact time of 30 min at room temperature ca. 293 K.

Enhanced adsorption capacity of low-cost magnetic clinoptilolite powders/beads for the effective removal of methylene blue: Adsorption and desorption studies

Clinoptilolite/Fe3O4 (Clin/Fe3O4) nanocomposite powders and Alginate/Clinoptilolite/Fe3O4 (Alg/Clin/Fe3O4) nanocomposite beads were prepared and used for methylene blue (MB) cationic dye removal from aqueous solution. The properties of the synthesized adsorbents were characterized by XRD, FTIR, SEM-EDX, dot mapping, VSM and BET analyses. Results confirmed that Fe3O4 nanoparticles were successfully placed in the structure of Clin/Fe3O4 nanocomposite powders and sodium alginate gelation method was effectively used to encapsulate the powders to Alg/Clin/Fe3O4 beads. The impacts of various parameters including pH, temperature, contact time, adsorbent dose, and initial MB dye concentration were investigated on the adsorbents’ performance towards MB dye removal. The maximum MB adsorption efficiency using Clin/Fe3O4 (97.57%) and Alg/Clin/Fe3O4 (93.62%) were obtained at an initial pH of 10. The results of the equilibrium study showed that the adsorption of MB using Clin/Fe3O4 and Alg/Clin/Fe3O4 followed the Langmuir isotherm model. The amount of monolayer adsorption capacity (qm) for Clin/Fe3O4 and Alg/Clin/Fe3O4 were determined as 45.662 mg/g and 12.484 mg/g, respectively. In addition, the values of n, RL, and E parameters derived from isotherm modeling showed that the MB dye adsorption process using both adsorbents was physically desirable. The kinetic data followed a pseudo-second order (PSO) kinetic model indicating that chemical mechanism was also effective in the adsorption process. The thermodynamic results showed that the adsorption process using both types of adsorbents was exothermic and spontaneous. Regeneration experiments performed in ethanol +0.5 M CaCl2 solution showed that the adsorption capacity of Clin/Fe3O4 and Alg/Clin/Fe3O4 was only decreased 7.92% and 9.76%, respectively after five cycles. This study demonstrated that Alg/Clin/Fe3O4 beads are efficient, very low-cost, environmentally friendly and fairly regenerable adsorbents for the removal of MB dye from the aquatic environment.

Methylene blue adsorption from an aqueous solution by a magnetic graphene oxide/humic acid composite

A novel adsorbent called magnetic humic acid/graphene oxide composite (MHAGO) adsorbent was prepared for treating methylene blue (MB) from wastewater. The structure and morphology of MHAGO were characterized by FTIR, XRD, SEM and XPS. The response surface method was used to optimize the quality feeding ratio for the raw materials, and the best graphene oxide: humic acid: ferroferric oxide feeding ratio was determined to be 0.25:0.50:1.66. Batch adsorption experiments were performed with variation in the initial MB dye concentration, pH of the solution, adsorbent dosage and contact time. The results showed that the adsorption reaction occurred at 45 °C with 30 mg adsorbent to adsorb 5.0 mg/L MB in 100 mL solution, with a maximum MB adsorption capacity of approximately 59.00 mg/g for MHAGO. The adsorption kinetics and adsorption isotherms were found to be in accordance with the Elovich equation and Langmuir model, respectively. Moreover, the thermodynamic parameters showed that the adsorption is spontaneously endothermic. The mechanisms for MB adsorption onto the MHAGO surface was mainly electrostatic attraction, π-π interaction and hydrogen bonding. In addition, the MHAGO shows good feasibility for the removal of pollutants from real factory dyeing wastewater.

Adsorption of Methylene blue (MB) dye Using NiO-SiO2NPs Synthesized from Aqueous Solutions: Optimization, kinetic and equilibrium studies

The applicability of the synthesized NiO-SiO2NPs as a novel adsorbent for eliminating Methylene Blue (MB) dye from aqueous media was investigated. Various techniques including BET, FT-IR, XRD, SEM and EDS were used to characterize this novel adsorbent. The investigation showed the applicability of NiO-SiO2NPs as an available, suitable and low-cost adsorbent for proper removing of MB dye from aqueous media. The effect of pH, adsorbent dosage (dose), initial MB dye concentration (C0) contact time (tc) and temperature (T) on the removal percentage (Ad%) of MB dye onto NiO-SiO2NPs was studied and the optimum value of each factor was determined (pH=7, dose=0.1g, C0=30 mg/L, tc=15 min and T=298.0 K). The experimental equilibrium data was fitted to the conventional isotherm models and accordingly Langmuir isotherm has good applicability for the explanation of experimental data with maximum adsorption capacity of the MB dye for SiO2 and NiO-SiO2NPs were roughly 117.0 and 140.0 mg/g respectively. Kinetics experiments were performed to investigate the adsorption kinetics, the pseudo-second-order kinetics coincided quite with the kinetic results. The thermodynamic behavior of the adsorption process was studied by considering the effect of temperature on the adsorption capacity, where the results showed that the process is spontaneous (∆G, Ad 0<0) at used temperature range and exothermic (∆H, Ad 0<0) with ∆S, Ad 0<0. Based on the magnitude of ∆H, Ad 0<0, it was concluded that the studied adsorption process is a physisorption one.

Optimization and batch studies on adsorption of Methylene blue dye using pomegranate fruit peel based adsorbent

Abstract Pomegranate fruit peel activated carbon (PFPAC) was prepared using potassium hydroxide impregnation and carbon (IV) oxide gasification methods for the remediation of Methylene blue (MB) from aqueous solution. The design of experiment for the optimization of variables for preparing activated carbon sourced from pomegranate fruit peel was carried out using response surface methodology (RSM). The adsorbent was characterized using BET, SEM, FTIR, and elemental analysis respectively. The BET analysis showed an improved surface area from raw PFP (1.01 m2/g) to PFPAC (845.96 m2/g). The optimum conditions for the adsorption of MB dye are 375 W, 0.9, and 4.5 min for radiation power, impregnation ratio, and activation time respectively. These resulted in high percentage of MB dye removal and PFPAC yield of 83.4% and 30.8% respectively. For batch equilibrium studies, the adsorption of MB dye onto the optimized PFPAC showed a strong dependence on the temperature, contact time, and initial MB dye concentration. Kinetic studies revealed rapid MB dye uptake at the initial stages of 0 – 3 h and attained equilibrium at 6 h for initial concentrations of 25 – 300 mg/L. Langmuir maximum monolayer adsorption capacities, q o ( max ) , at temperatures of 303, 318, and 333 K are 250.00, 239.05, and 235.58 mg/g respectively, thus suggesting a favourable adsorption at low temperature. Modeling of the adsorption data using three kinetic models, revealed that pseudo first order (PFO) model best explained the adsorption process of MB dye onto PFPAC indicating a physisorption process. Chemically activated PFPAC was found to be valuable and effective for sequestrating MB dye from the aqueous solutions. Procedure Experimental design (central composite design)

Degradation and mineralization of methylene blue dye by peroxymonosulfate/[formula omitted] nanoparticles using central composite design: Kinetic study

In this study, the Mn3O4 nanoparticles (Mn3O4 NPs) were synthesized by chemical precipitation for peroxymonosulfate (PMS) activation. The physicochemical properties of the synthesized Mn3O4 catalysts were measured by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). To investigate the parameters affecting the methylene blue (MB) decolorization process (pH, dye concentration, Mn3O4 dosage, and PMS concentration), and optimization of them, response surface methodology (RSM) with central composite design (CCD) was used. In order to evaluate the efficiency of the studied process in removing organic matter and intermediate products, chemical oxygen demand (COD) and total organic carbon (TOC) analyzes were performed in optimal conditions, respectively. Maximum MB decolorization (86.71%) was achieved at optimal condition, pH = 4, Mn3O4 = 0.12 g, PMS = 0.94 g, initial MB dye concentration = 62 mg/L at a fixed time 20 min. Experiment results showed that PMS generates sulfate radicals (SO4∙-) in the presence of Mn3O4 NPs, which has a high ability to decompose refractor organic contaminants. According to the results, the highest catalytic performance of the MB decolorization mechanism is typically related to the synergistic effects of Mn3O4 and PMS.

Evaluation of Cationic Methylene Blue Dye Removal by High Surface Area Mesoporous Activated Carbon Derived from Ulva lactuca

Mesoporous nano-activated carbon was prepared from green algae Ulva lactuca using zinc chloride impregnation as the activation process. The obtained activated carbon was tested as a cationic dye adsorbent which is the aim of this research work. Prepared activated carbon was characterized by FTIR, BET, t-plot, BJH, TGA, SEM, TEM and EDAX. The obtained activated carbon has 84.37% carbon content, 1486 m2/g specific surface area, 0.8891 cm3/g total pore volume, and 2.32 nm average pore diameter. The adsorption properties of the prepared activated carbon were tested using Methylene blue (MB) dye. Batch experiments were applied under different adsorption parameters like pH, adsorbent dose, initial MB dye concentration, and agitation time. Different known isotherms and kinetics models were applied to the batch experimental data of MB dye removal. It was found that the adsorption data was well fitted by Langmuir model showing a monolayer adsorption capacity of 344.83 mg/g of MB dye. Kinetic studies revealed that the MB dye adsorption by Ulva lactuca activated carbon followed pseudo-second-order model with very high correlation coefficient (R2 > 0.998). The prepared activated carbon was subjected to a total of five adsorption-desorption regeneration cycles with very small loss of its dye-adsorption capacities.

Adsorption of methylene blue from aqueous solution by peanut shell based activated carbon

Peanut shell-based activated carbon (PSAC) was used to study the removal of methylene blue (MB) dye from aqueous solution. Chemical agent of sodium hydroxide (NaOH) and gasification agent of carbon dioxide (CO2) were used to prepare PSAC via physicochemical activation. In batch studies, several effects namely, initial MB dye concentration, solution temperature, and solution pH were evaluated. Isotherm and kinetic study revealed that the adsorption system of MB-PSAC was fitted the finest by Freundlich and pseudo-second-order models, respectively. Thermodynamic studies certified that MB adsorption onto PSAC was physically controlled and was endothermic in nature.

Removal of methylene blue from aqueous solution by ozone microbubbles

In this work, ozone microbubbles (OMBs) technique was used to remove methylene blue dye (MB) from water in a semi- batch reactor. The removal efficiency of methylene blue dye were investigated under various reaction conditions such as effect of initial solution pH, ozone generation rate, initial methylene blue dye concentration and determination of mass transfer coefficient. The removal of methylene blue by Ozonation microbubbles were very high at the acidic media and upon increasing ozone generation rate from 0.498 to 0.83 mg s−1, the removal efficiency dramatically increased from 8 to 98%.The overall rate of the oxidation reaction fitted well a second order kinetic model. The results demonstrated that ozone microbubbles were effective in terms of the elimination of methylene blue concentration and its complete mineralization.

Green synthesis of reduced graphene oxide grafted Ag/ZnO for photocatalytic abatement of methylene blue and antibacterial activities

We have reported a facile, green synthesis of reduced graphene oxide (RGO) grafted Ag/ZnO (RGO-Ag/ZnO) nanocomposite in the presence of L-Methionine (L-Met) for synergetic photocatalytic degradation of methylene blue (MB) and antibacterial activities. L-Met shows an excellent efficiency as stabilizing and reducing agents for the synthesis of both Ag NPs and RGO. The successful synthesis of pure phase L-Met-RGO-Ag/ZnO was confirmed by XRD. According to UV-DRS analysis, the doping of Ag resulted in a decrease bandgap energy of ZnO from 3.34 eV to 3.18 eV. The mixed morphologies of the nanocomposite were studied by SEM and TEM. The photocatalytic degradation efficiency of L-Met-RGO-Ag/ZnO towards MB dye was investigated at varying initial concentrations of MB dye, H2O2, and ultrasonication. The optimum degradation efficiency of the nanocomposite (50 mg) at room temperature (25 °C) was found to be 99% with an initial MB dye concentration of 10 mg/L and 120 min contact time. The fast degradation of MB dye was observed in the presence of H2O2. The ultrasonication of the catalyst vanishes the synergetic interface of the nanocomposite, as a result, poor photocatalytic performance (85%) was observed even at a long period of contact time (210 min). Moreover, RGO-Ag/ZnO nanocomposites have shown strong antibacterial activity against both Gram-positive bacteria (B. Subtilis) and Gram-negative bacteria (E. coli). In conclusion, RGO-Ag/ZnO nanocomposite shows a promising photocatalyst for the degradation of organic dyes and antibacterial activities.

Comprehensive kinetic and mass transfer modeling for methylene blue dye adsorption onto CuO nanoparticles loaded on nanoporous activated carbon prepared from waste coconut shell

Abstract The waste coconut shell (WCS) was used for the preparation of nanoporous activated carbon (NPAC) by chemical and physical activation method. The synthesized CuO nanoparticles were successfully loaded on the NPAC by the physical adsorption method. Different characterization techniques such as XRD, FT-IR, BET surface area, point of zero charge (pHpzc), SEM, TEM, SADE pattern, particle size distribution, and XPS were used to determine the physical-chemical properties of the CuO-NPAC nanocomposite. Thus, the prepared nanocomposites were used for methylene blue (MB) dye adsorption from aqueous solution by varying batch experimental parameters, such as initial MB dye concentration, initial pH, contact time, temperature, SDS concentration and amount of nanocomposite. In this work, a kinetic model was developed, and the developed kinetic equation was fitted with experimental data, and compared with several traditional models, such as the pseudo-second-order and Elovich models. The mass transfer mechanism was described by four diffusion models, such as Weber-Morris, liquid diffusion, Bangham's and Burt, and McKay et al. models. Adsorption equilibrium data were fitted to non-linear form of conventional isotherm models such as Langmuir, Freundlich, and Sips models, and according to high R2 values, the Sips model was best fitted followed by Langmuir and Freundlich. The possible reaction mechanism for the adsorption of MB onto the CuO-NPAC nanocomposite has also been suggested. The thermodynamic studies confirmed spontaneous adsorption of MB onto CuO-NPAC nanocomposites and showed suitability at high temperatures. The regeneration study of nanocomposite was accomplished by HCl, H2SO4, ethanol, double distilled water, and NaOH to determine the suitable reagent for the same.