Enhancing Methylene Blue Removal through Adsorption and Photocatalysis-A Study on the GO/ZnTiO3/TiO2 Composite.

This study focuses on synthesizing and characterizing a graphene oxide/ZnTiO3/TiO2 (GO/ZTO/TO) composite to efficiently remove methylene blue (MB) from water, presenting a novel solution to address industrial dye pollution. GO and ZTO/TO were synthesized by the modified Hummers and sol-gel methods, respectively, while GO/ZTO/TO was prepared using a hydrothermal process. The structural and surface properties of the composite were characterized using various analytical techniques confirming the integration of the constituent materials and suitability for dye adsorption. The study revealed that GO/ZTO/TO exhibits an adsorption capacity of 78 mg g-1 for MB, with only a 15% reduction in adsorption efficiency until the fifth reuse cycle. Furthermore, the study suggests optimal adsorption near neutral pH and enhanced performance at elevated temperatures, indicating an endothermic reaction. The adsorption behavior fits the Langmuir isotherm, implying monolayer adsorption on homogeneous surfaces, and follows pseudo-second-order kinetics, highlighting chemical interactions at the surface as the rate-limiting step. The photocatalytic degradation of MB by GO/ZTO/TO follows pseudo-first-order kinetics, with a higher rate constant than that of GO alone, demonstrating the enhanced photocatalytic activity of the composite. In conclusion, GO/ZTO/TO emerges as a promising and sustainable approach for water purification, through an adsorption process and subsequent photocatalytic degradation.

Easy Preparation of Liposome@PDA Microspheres for Fast and Highly Efficient Removal of Methylene Blue from Water.

Mussel-inspired chemistry was usefully exploited here with the aim of developing a high-efficiency, environmentally friendly material for water remediation. A micro-structured material based on polydopamine (PDA) was obtained by using liposomes as templating agents and was used for the first time as an adsorbent material for the removal of methylene blue (MB) dye from aqueous solutions. Phospholipid liposomes were made by extrusion and coated with PDA by self-polymerization of dopamine under simple and mild conditions. The obtained Liposome@PDA microspheres were characterized by DLS and Zeta potential analysis, TEM microscopy, and FTIR spectroscopy. The effects of pH, temperature, MB concentration, amount of Liposome@PDA, and contact time on the adsorption process were investigated. Results showed that the highest adsorption capacity was obtained in weakly alkaline conditions (pH = 8.0) and that it could reach up to 395.4 mg g-1 at 298 K. In addition, adsorption kinetics showed that the adsorption behavior fits a pseudo-second-order kinetic model well. The equilibrium adsorption data, instead, were well described by Langmuir isotherm. Thermodynamic analysis demonstrated that the adsorption process was endothermic and spontaneous (ΔG0 = -12.55 kJ mol-1, ΔH0 = 13.37 kJ mol-1) in the investigated experimental conditions. Finally, the applicability of Liposome@PDA microspheres to model wastewater and the excellent reusability after regeneration by removing MB were demonstrated.

Highly Efficient Methylene Blue Dye Removal by Nickel Molybdate Nanosorbent.

Removing methylene blue (MB) dye from aqueous solutions was examined by the use of nickel molybdate (α-NiMoO4) as an adsorbent produced by an uncomplicated, rapid, and cost-effective method. Different results were produced by varying different parameters such as the pH, the adsorbent dose, the temperature, the contact time, and the initial dye concentration. Adsorbent dose and pH had a major removal effect on MB. Interestingly, a lower amount of adsorbent dose caused greater MB removal. The amount of removal gained was efficient and reached a 99% level with an initial methylene blue solution concentration of ≤160 ppm at pH 11. The kinetic studies indicated that the pseudo-second-order kinetic model relates very well with that of the obtained experimental results. The thermodynamic studies showed that removing the MB dye was favorable, spontaneous, and endothermic. Impressively, the highest quantity of removal amount of MB dye was 16,863 mg/g, as shown by the Langmuir model. The thermal regeneration tests revealed that the efficiency of removing MB (11,608 mg/g) was retained following three continuous rounds of recycled adsorbents. Adsorption of MB onto α-NiMoO4 nanoparticles and its regeneration were confirmed by Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) analysis. The results indicated that α-NiMoO4 nanosorbent is an outstanding and strong candidate that can be used for removing the maximum capacity of MB dye in wastewater.

Experimental and Theoretical Insights on Methylene Blue Removal from Wastewater Using an Adsorbent Obtained from the Residues of the Orange Industry.

Chemical and thermochemical transformations were performed on orange peel to obtain materials that were characterized and further tested to explore their potential as adsorbents for the removal of methylene blue (MB) from aqueous solutions. The results show the high potential of some of these materials for MB adsorption not only due to the surface area of the resulting substrate but also to the chemistry of the corresponding surface functional groups. Fitting of the kinetic as well as the equilibrium experimental data to different models suggests that a variety of interactions are involved in MB adsorption. The overall capacities for these substrates (larger than 192.31 mg g-1) were found to compare well with those reported for activated carbon and other adsorbents of agro-industrial origin. According to these results and complementary with theoretical study using Density Functional Theory (DFT) approximations, it was found that the most important adsorption mechanisms of MB correspond to: (i) electrostatic interactions, (ii) H-bonding, and (iii) π (MB)-π (biochar) interactions. In view of these findings, it can be concluded that adsorbent materials obtained from orange peel, constitute a good alternative for the removal of MB dye from aqueous solutions.

Synthesis of Fe2SiO4-Fe7Co3 Nanocomposite Dispersed in the Mesoporous SBA-15: Application as Magnetically Separable Adsorbent.

The mixture containing alloy and oxide with iron-based phases has shown interesting properties compared to the isolated species and the synergy between the phases has shown positive effect on dye adsorption. This paper describes the synthesis of Fe2SiO4-Fe7Co3-based nanocomposite dispersed in Santa Barbara Amorphous (SBA)-15 and its application in dye adsorption followed by magnetic separation. Thus, it was studied the variation of reduction temperature and amount of hydrogen used in synthesis and the effect of these parameters on the physicochemical properties of the iron and cobalt based oxide/alloy mixture, as well as the methylene blue adsorption capacity. The XRD and Mössbauer results, along with the temperature-programmed reduction (TPR) profiles, confirmed the formation of Fe2SiO4-Fe7Co3-based nanocomposites. Low-angle XRD, N2 isotherms, and TEM images show the formation of the SBA-15 based mesoporous support with a high surface area (640 m2/g). Adsorption tests confirmed that the material reduced at 700 °C using 2% of H2 presented the highest adsorption capacity (49 mg/g). The nanocomposites can be easily separated from the dispersion by applying an external magnetic field. The interaction between the dye and the nanocomposite occurs mainly by π-π interactions and the mixture of the Fe2SiO4 and Fe7Co3 leads to a synergistic effect, which favor the adsorption.

Stepwise Ethanol-Water Fractionation of Enzymatic Hydrolysis Lignin to Improve Its Performance as a Cationic Dye Adsorbent.

In this work, lignin fractionation is proposed as an effective approach to reduce the heterogeneity of lignin and improve the adsorption and recycle performances of lignin as a cationic dye adsorbent. By stepwise dissolution of enzymatic hydrolysis lignin in 95% and 80% ethanol solutions, three lignin subdivisions (95% ethanol-soluble subdivision, 80% ethanol-soluble subdivision, and 80% ethanol-insoluble subdivision) were obtained. The three lignin subdivisions were characterized by gel permeation chromatography (GPC), FTIR, 2D-NMR and scanning electron microscopy (SEM), and their adsorption capacities for methylene blue were compared. The results showed that the 80% ethanol-insoluble subdivision exhibited the highest adsorption capacity and its value (396.85 mg/g) was over 0.4 times higher than that of the unfractionated lignin (281.54 mg/g). The increased adsorption capacity was caused by the enhancement of both specific surface area and negative Zeta potential. The maximum monolayer adsorption capacity of 80% ethanol-insoluble subdivision by adsorption kinetics and isotherm studies was found to be 431.1 mg/g, which was much higher than most of reported lignin-based adsorbents. Moreover, the 80% ethanol-insoluble subdivision had much higher regeneration yield (over 90% after 5 recycles) compared with the other two subdivisions. Consequently, the proposed fractionation method is proved to be a novel and efficient non-chemical modification approach that significantly improves adsorption capacity and recyclability of lignin.

Application of EDTA modified Fe3O4/sawdust carbon nanocomposites to ameliorate methylene blue and brilliant green dye laden water.

This work explored the potential of magnetic sawdust carbon nanocomposites for cationic dyes removal from aqueous medium. EDTA modified magnetic sawdust carbon nanocomposites (EDTA@Fe3O4/SC ncs) were prepared by biogenic green reduction and precipitation approach. The surface properties, structure and composition of nanocomposites were characterized by HRTEM, FESEM, XRD, EDX, BET, FTIR etc. The Fe3O4 nanoparticles were 10-20 nm in diameters and having 14 m2/g surface area. Removal of Methylene blue (MB) and Brilliant green (BG) dyes from aqueous medium was studied in batch mode experiments. The maximum removal was achieved at neutral pH 7.0 with in 30 min. Adsorption capacity of EDTA@Fe3O4/SC for MB and BG dyes was 227.3 mg/g and 285.7 mg/g, respectively. Dye adsorption behaviour is well explained by Freundlich model. The rate of cationic dye adsorption is explained by pseudo-second order model. The value of thermodynamic parameters confirmed that adsorption process was spontaneous and favourable. Desorption and reusable efficiency of nanocomposites was also evaluated.

Nitrogen Self-Doped Activated Carbons Derived from Bamboo Shoots as Adsorbent for Methylene Blue Adsorption.

Bamboo shoots, a promising renewable biomass, mainly consist of carbohydrates and other nitrogen-related compounds, such as proteins, amino acids and nucleotides. In this work, nitrogen self-doped activated carbons derived from bamboo shoots were prepared via a simultaneous carbonization and activation process. The adsorption properties of the prepared samples were evaluated by removing methylene blue from waste water. The factors that affect the adsorption process were examined, including initial concentration, contact time and pH of methylene blue solution. The resulting that BSNC-800-4 performed better in methylene blue removal from waste water, due to its high specific surface area (2270.9 m2 g-1), proper pore size (2.19 nm) and relatively high nitrogen content (1.06%). Its equilibrium data were well fitted to Langmuir isotherm model with a maximum monolayer adsorption capacity of 458 mg g-1 and a removal efficiency of 91.7% at methylene blue concentration of 500 mg L-1. The pseudo-second-order kinetic model could be used to accurately estimate the carbon material's (BSNC-800-4) adsorption process. The adsorption mechanism between methylene blue solution and BSNC-800-4 was controlled by film diffusion. This study provides an alternative way to develop nitrogen self-doped activated carbons to better meet the needs of the adsorption applications.

A novel system of MnO2-mullite-cordierite composite particle with NaClO for Methylene blue decolorization.

The MnO2-mullite-cordierite composite particle (MnO2-MCP) was prepared and firstly was applied as catalyst with sodium hypochlorite (NaOCl) as oxidant in heterogeneous Fenton-like system for methylene blue (MB) decolorization. The MnO2-MCP was characterized by XRD, SEM, EDS and BET analysis. The decolorization efficiencies of MB/MnO2-MCP, MB/NaClO, (MB after filtrating MnO2-MCP)/NaClO and MB/MnO2-MCP/NaClO were compared, which confirmed the interaction ability between MnO2-MCP and NaClO. After evaluating the role of adsorption of MB by MnO2-MCP, the catalytic oxidation effects of MnO2-MCP with NaClO on MB were exploited. The adsorption results showed that the new porous catalyst had certain adsorption capacity for MB and the adsorption fit best with Langmuir model. The central composite rotatable design (CCD) of response surface methodology (RSM) was used to design catalytic oxidation experiments of MB/MnO2-MCP/NaClO system, with influencing factors of catalyst dose, NaClO concentration, pH and initial MB concentration. The optimum conditions were 5.97 mM of NaClO, 37.9 g/L of catalyst dose, 5.74 of pH value and 100.71 mg/L of initial MB concentration, which could ensure nearly 100% MB decolorization. The effect of radical scavengers elucidated that superoxide anion (O2-) was the main species to decolorize MB. Then the possible degradation mechanism and pathway of MB were proposed in this MnO2-MCP/NaClO system.

Synchronized methylene blue removal using Fenton-like reaction induced by phosphorous oxoanion and submerged plasma irradiation process.

In this study, a combination of phosphorus (PP) oxoanions in a submerged plasma irradiation (SPI) system was used to enhance the removal efficiency of dyes from wastewater. The SPI system showed synergistic methylene blue removal efficiency, due to the plasma irradiation and Fenton-like oxidation. The ferrous ions released from the iron electrode in the SPI system under plasmonic conditions form complexes with the PP anions, which can then react with dissolved oxygen (O2) or hydrogen peroxide (H2O2) via Fenton-like reactions. The experimental results revealed that a sodium triphosphate (TPP) combined SPI system has a higher dye removal efficiency than a tetrasodium pyrophosphate (DP) or a sodium hexametaphosphate (HMP) combined SPI system under similar dissolved iron ion concentrations. To confirm the accuracy of the proposed removal mechanism via Fenton-like oxidation, it was compared to SPI systems under an oxygen environment (TPP/SPI/O2 (k = 0.0182 s-1)) and a nitrogen environment (TPP/SPI/N2 (k = 0.0062 s-1)). The results indicate that the hydroxyl radical (OH) in the TPP/SPI/O2 system is the major oxidant in methylene blue removal, because the dye degradation rates dramatically decreased with the addition of radical scavengers such as tert-butanol (k = 0.0023 s-1) and methanol (k = 0.0021 s-1). On the other hand, no change was observed in the methylene blue removal efficiency of the TPP/SPI/O2 system when it was subjected to a wide range of pHs (3-9). In addition, it was proved that this system could be used to eliminate six different commercial dyes. The results of this study indicated that the TPP/SPI/O2 system is a promising advanced oxidation approach for dye wastewater treatment.

Facilitative capture of As(V), Pb(II) and methylene blue from aqueous solutions with MgO hybrid sponge-like carbonaceous composite derived from sugarcane leafy trash.

Enhancing the contaminant adsorption capacity is a key factor affecting utilization of carbon-based adsorbents in wastewater treatment and encouraging development of biomass thermo-disposal. In this study, a novel MgO hybrid sponge-like carbonaceous composite (HSC) derived from sugarcane leafy trash was prepared through an integrated adsorption-pyrolysis method. The resulted HSC composite was characterized and employed as adsorbent for the removal of negatively charged arsenate (As(V)), positively charged Pb(II), and the organic pollutant methylene blue (MB) from aqueous solutions in batch experiments. The effects of solution pH, contact time, initial concentration, temperature, and ionic strength on As(V), Pb(II) and MB adsorption were investigated. HSC was composed of nano-size MgO flakes and nanotube-like carbon sponge. Hybridization significantly improved As(V), Pb(II) and methylene blue (MB) adsorption when compared with the material without hybridization. The maximum As(V), Pb(II) and MB adsorption capacities obtained from Langmuir model were 157 mg/g, 103 mg/g and 297 mg/g, respectively. As(V) adsorption onto HSC was best fit by the pseudo-second-order model, and Pb(II) and MB with the intraparticle diffusion model. Increased temperature and ionic strength decreased Pb(II) and MB adsorption onto HSC more than As(V). Further FT-IR, XRD and XPS analysis demonstrated that the removal of As(V) by HSC was mainly dominated by surface deposition of MgHAsO4 and Mg(H2AsO4)2 crystals on the HSC composite, while carbon π-π* transition and carbon π-electron played key roles in Pb(II) and MB adsorption. The interaction of Pb(II) with carbon matrix carboxylate was also evident. Overall, MgO hybridization improves the preparation of the nanotube-like carbon sponge composite and provides a potential agricultual residue-based adsorbent for As(V), Pb(II) and MB removal.

Evaluation of the effectiveness and mechanisms of acetaminophen and methylene blue dye adsorption on activated biochar derived from municipal solid wastes.

The adsorption potential and governing mechanisms of emerging contaminants, i.e. acetaminophen or acetyl-para-aminophenol (APAP) and methylene blue (MB) dye, on activated carbon derived from municipal solid waste were investigated in this work. Results showed that MB adsorption was significantly more effective, with a maximum removal of 99.9%, than APAP adsorption (%Rmax = 63.7%). MB adsorption was found to be unaffected by pH change, while the adsorption capacity of APAP drastically dropped by about 89% when the pH was adjusted from pH 2 to 12. Surface reactions during APAP adsorption was dominated by both physical and chemical interactions, with the kinetic data showing good fit in both pseudo-first order (R2 = 0.986-0.997) and pseudo-second order (R2>0.998) models. On the other hand, MB adsorption was best described by the pseudo-second order model, with R2>0.981, denoting that chemisorption controlled the process. Electrostatic attractions and chemical reactions with oxygenated surface functional groups (i.e., -OH and -COOH) govern the adsorption of APAP and MB on the activated biochar. Thermodynamic study showed that APAP and MB adsorption were endothermic with positive ΔH° values of 16.5 and 74.7 kJ mol-1, respectively. Negative ΔG° values obtained for APAP (-3.7 to -5.1 kJ mol-1) and MB (-11.4 to -17.1 kJ mol-1) implied that the adsorption onto the activated biochar was spontaneous and feasible. Overall, the study demonstrates the effectiveness of activated biochar from municipal solid wastes as alternative adsorbent for the removal of acetaminophen and methylene blue dye from contaminated waters.

Adsorptive performance of MOF nanocomposite for methylene blue and malachite green dyes: Kinetics, isotherm and mechanism.

In the present study, Fe3O4@AMCA-MIL-53(Al) nanocomposite was utilized for the adsorptive removal of highly toxic MB and MG dyes from aqueous environment. The batch adsorption tests were performed at different contact time, pH, Fe3O4@AMCA-MIL-53(Al) dose, initial concentration of dyes and temperature. The maximum adsorption capacity of MB and MG dyes onto of Fe3O4@AMCA-MIL-53(Al) using Langmuir equation was 1.02 and 0.90 m mol/g, respectively. The isotherm and kinetic studies revealed that adsorption data were well fitted to Langmuir isotherm and pseudo-first-order kinetics models. Various thermodynamic parameters were also calculated and interpreted. The positive and negative values of ΔH° and ΔG° indicated that the adsorption was endothermic and spontaneous, respectively. The adsorptive binding of MB and MG on Fe3O4@AMCA-MIL53(Al) nanocomposite was directed by carboxylate and amide groups through electrostatic interaction, π-π interaction and hydrogen bonding. The desorption of both dyes from Fe3O4@AMCA-MIL-53(Al) was also performed using mixed solution of 0.01 M HCl/ethanol. Thus, we conclude that the Fe3O4@AMCA-MIL-53(Al) was an outstanding material for the removal of dyes from aqueous environment.

Fabrication of novel sandwich nanocomposite as an efficient and regenerable adsorbent for methylene blue and Pb (II) ion removal.

An adsorbent, which is easy to be separated and reused after adsorption, is very important for the removal of pollutants in aqueous solution. Hence, a novel nanofibrous sandwich structured adsorbent of silica nanofiber/magnetite nanoparticles/porous silica (SNF/MNP/PS) was designed and synthesized for the first time. The magnetite nanoparticles with diameter less than 10 nm were evenly distributed on the surface of silica nanofiber, which was subsequently fully covered by a layer of porous silica. The novel adsorbent was proved possessing good adsorption capacity for both methylene blue (MB) and Pb (II) ion (Pb2+), and the adsorption equilibrium could be well described by the Langmuir-isotherm model with the maximum adsorption capacity of 103.1 mg/g for MB and 243.9 mg/g for Pb2+ at 288 K. Moreover, in MB-Pb2+ mixed system the measured adsorption capacity reached 74.5 mg/g for MB and 202.4 mg/g for Pb2+, respectively. The saturated adsorbent could be readily magnetically separated from the solution and then efficiently regenerated by heterogeneous Fenton-like reaction (for MB) or acidic desorption process (for Pb2+), respectively. After 5 cycles of adsorption-regeneration, the adsorption capacity of the reused adsorbent still reached 81.0% (for MB) and 70.9% (for Pb2+) of the initial value. The SNF/MNP/PS behaves good adsorption properties for different types of pollutants, high magnetic recoverability and regeneration efficiency, which make it applicable to different contaminants removal.

Effect of hydrophobic and hydrophilic nanoparticles loaded in D2EHPA/M2EHPA - PTFE supported liquid membrane for simultaneous cationic dyes pertraction.

Cationic dyes mixture pertraction experiments of Rhodamine B (RhB) and Methylene Blue (MB) using a flat sheet supported liquid membrane (SLM) were performed. Mono-(2-etylhexyl) ester of phosphoric acid (M2EHPA) and bis-(2-etylhexyl) ester of phosphoric acid (D2EHPA) mixture was used as carrier and Sesame oil to dilute the carrier due to its very high viscosity. Acetic acid (AA) was also used as stripper phase. Influences of hydrophobic and hydrophilic nanoparticles were loaded in a carrier at different loadings (from 0 to 6 mg mL-1) on dyes pertraction at constant operating conditions were investigated. It was found that hydrophilic nanoparticles, including ZnO and TiO2 decrease dyes pertraction, while hydrophobic nanoparticles, including ZIF-8 and Fe3O4 favorably increase this parameter. ZIF-8 was found as the most effective nanoparticles on increasing dyes pertraction and the optimum loading was 2 mg mL-1. Also, the important process parameters that influence on the dyes mixture pertraction efficiency such as feed concentration, carrier concentration, feed pH and strip concentration were studied. In order to investigate the effects of operating parameters, all experiments were performed at a constant 2 mg mL-1 ZIF-8 loading. Optimum pertraction efficiency of RhB and MB were 90.6 and 79.4%, respectively. They were obtained after 10 h pertraction at optimum experimental conditions with feed concentration of 100 mg L-1, carrier concentration of 35% (vol), strip concentration of 0.5 mol L-1, and feed pH of 6. Effect of time on pertraction efficiencies at the optimum conditions were also studied.

Pomelo Peel Modified with Citrate as a Sustainable Adsorbent for Removal of Methylene Blue from Aqueous Solution.

An anionic adsorbent was prepared by grafting citrate onto pomelo peel (PPL) to remove methylene blue (MB) from aqueous solution. The PPL and modified pomelo peel (MPPL) were analyzed by Fourier transform infrared spectroscopy (FTIR) and observed by scanning electron microscopy (SEM). The effects of dye concentration, contact time, and pH on adsorption were studied. The FTIR results confirmed that the carboxyl groups were successfully bound to cellulose molecules in PPL via modification with citrate. SEM indicated that the surface of PPL became clean and the porous structure was well maintained after modification. The adsorption capacities of MB onto PPL and MPPL were 81.7 mg/g and 199.2 mg/g, respectively, thus indicating that the addition of anionic groups significantly improved the adsorption performance. The increase in the initial dye concentration and pH of the dye solution promoted the adsorption process. The adsorption equilibrium on MPPL required approximately 3 h. The adsorption of MB on MPPL was well described by a pseudo-second order kinetic model and Langmuir isotherm model. The thermodynamic parameters indicated spontaneous and exothermic adsorption. This study suggests that PPL modified with citrate can be used as a sustainable adsorbent in wastewater purification.

Zero-valent iron nanoparticles for methylene blue removal from aqueous solutions and textile wastewater treatment, with cost estimation.

Nanoscale zero-valent iron (nZVI) particles were investigated for the removal of methylene blue (MB) from aqueous solutions and the treatment of textile industry effluents. The nZVI material was characterized by XRD, TEM, EDS, FTIR, and SEM. It was demonstrated that several functional groups such as C-H, C = C, C-C, and C-O contributed to MB reduction. At initial MB concentration of 70 mg/L, the optimum pH was 6, achieving a removal efficiency of 72.1% using an nZVI dosage of 10 g/L, stirring rate of 150 rpm, and temperature of 30 °C within 30 min. The adsorption isotherm was described by the Langmuir model with monolayer coverage of 5.53 mg/g, and the Freundlich equation with multilayer adsorption capacity of 1.59 (mg/g)·(L/mg)1/n. The removal mechanisms of MB included reduction into colorless leuco-MB, precipitation as Fe(II)-MB, adsorption as ZVI-MB or FeOOH-MB, and/or degradation using •OH radicals. The synthesized nZVI particles were applied to reduce various organic and inorganic compounds, as well as heavy metal ions from real textile wastewater samples. The removal efficiencies of COD, BOD, TN, TP, Cu2+, Zn2+, and Pb2+ reached up to 91.9%, 87.5%, 65.2%, 78.1%, 100.0%, 29.6%, and 99.0%, respectively. The treatment cost of 1 m3 of textile wastewater was estimated as 1.66 $USD.

Graphene oxide edge grafting of polyaniline nanocomposite: an efficient adsorbent for methylene blue and methyl orange.

Polyaniline (PANI) chains were grafted at the edge of graphene oxide (GO) sheets by in-situ chemical oxidation polymerization. The obtained GO-PANI composite was used for the adsorption of cationic methylene blue (MB) and anionic methyl orange (MO) dyes from aqueous solutions. The structure of the GO-PANI composite was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electronic micrograph (SEM), X-ray photoelectron spectroscopy (XPS) and zeta potentials. GO-PANI exhibited a high adsorption capacity for MB (962 mg/g) and MO (885 mg/g) compared with other reported absorbents, which was due to adsorption through strong π-π stacking and anion-cation interactions. The nanocomposite could be recycled five times without significant loss in removal abilities for MB (87.8%) and MO (75.0%), respectively. GO-PANI composite is a promising adsorbent for the adsorption of anionic and cationic dyes from aqueous solutions.

Utilization of two agrowastes for adsorption and removal of methylene blue: kinetics and isotherm studies.

Fresh water streams contaminated with synthetic dye-containing effluents pose a threat to aquatic and human life either by preventing aquatic photosynthesis or by entering into the food chain. Adsorptive removal of such dyes with potent biosorbents is an important technique to reduce bioaccumulation and biomagnifications of the dyes in human life. We report use of betel nut (BN) husk and banana peel (BP), two most abundant ligno-cellulosic wastes, as efficient adsorbents for the removal of the basic dye methylene blue (MB). The adsorption by BN and BP was consistently high over wide ranges of pH and temperature, suggesting their dye removal potential in diverse conditions. Physico-chemical studies, e.g. scanning electron microscopy and Fourier transform-infrared spectroscopy studies, revealed changes in surface topology and functional moieties of BN and BP post adsorption, implying dye interaction with the biomass surface. The dye adsorption in both cases followed pseudo-second-order kinetics. While adsorption of MB by BN was better fitted with the Temkin isotherm model, adsorption with BP followed both Langmuir and Freundlich isotherm models. Our studies concluded that both adsorbents efficiently remove MB from its aqueous solution with BP proved to be marginally superior to BN.

Study of the effect of an acid treatment of a natural Moroccan bentonite on its physicochemical and adsorption properties.

In this study, a natural bentonite taken from a deposit in the Northeast of Morocco has been purified (PB) and treated with various HCl molarities (xHPB) in order to obtain an HCl/Bentonite weight ratio equal to 0.2, 0.4 and 0.6. The obtained physicochemical characterization results indicated that the PB sample is composed mainly of the montmorillonite phase. The impact of acid treatment was investigated by identifying changes in the chemical composition, cation exchange capacity, infrared absorption bands, crystalline structure, morphology of the particles and specific surface area. The adsorption behavior of methylene blue (MB) and methyl orange (MO) in aqueous solution onto PB and xHPB samples was investigated by varying the initial concentration of dyes, the contact time and the temperature. The obtained results showed that the experimental data best fit the Langmuir model and the pseudo-second-order kinetic model. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies carried out after MB and MO adsorption onto PB samples indicated that MB cations were intercalated, in the form of monomers and dimers, with a large amount of monomers, slightly tilted against the plane of the clay surface. While MO molecules adsorb, with a near perpendicular alignment, with their SO3- group and O- atoms facing the mineral surface plane.