Model Cationic Dye Research Articles

A Highly Sensitive Chitosan-Based SERS Sensor for the Trace Detection of a Model Cationic Dye.

The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is reported in this study. Grafted chitosan was employed as a matrix support for Ag nanoparticles (NPs) for the surface-enhanced Raman spectroscopy (SERS). Chitosan (CS) was decorated with thiol and carboxylic acid groups by incorporating S-acetyl mercaptosuccinic anhydride (SAMSA) to yield CS-SAMSA. Then, Ag NPs were immobilized onto the CS-SAMSA (Ag@CS-SAMSA) and characterized by spectral methods (IR, Raman, NIR, solid state 13C NMR with CP-MAS, XPS, and TEM). Ag@CS-SAMSA was evaluated as a substrate for SERS, where methylene blue (MB) was used as a model dye adsorbate. The Ag@CS-SAMSA sensor demonstrated a high sensitivity (with an enhancement factor ca. 108) and reusability over three cycles, with acceptable reproducibility and storage stability. The Raman imaging revealed a large SERS effect, whereas the MB detection varied from 1-100 μM. The limits of detection (LOD) and quantitation (LOQ) of the biocomposite sensor were characterized, revealing properties that rival current state-of-the-art systems. The dye adsorption profiles were studied via SERS by fitting the isotherm results with the Hill model to yield the ΔG°ads for the adsorption process. This research demonstrates a sustainable dual-function biocomposite with tailored adsorption and sensing properties suitable for potential utility in advanced water treatment technology and environmental monitoring applications.

Centaurea behen leaf extract mediated green synthesized silver nanoparticles as antibacterial and removing agent of environmental pollutants with blood compatible and hemostatic effects

The present study focused on evaluating the antibacterial properties, radical scavenging, and photocatalytic activities of Centaurea behen-mediated silver nanoparticles (Cb-AgNPs). The formation of Cb-AgNPs was approved by UV–Vis spectrometry, Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy (SEM), energy dispersive X-ray and X-ray diffraction. The results showed that the obtained AgNPs have a maximum absorbance peak at 450 nm with spherical morphology and an average size of 13.03 ± 5.8 nm. The catalytic activity of the Cb-AgNPs was investigated using Safranin O (SO) solution as a cationic dye model. The Cb-AgNPs performed well in the removal of SO. The coupled physical adsorption/photocatalysis reaction calculated about 68% and 98% degradation of SO dye under solar irradiation. The Cb-AgNPs inhibited the growth of gram-negative or positive bacteria strains and had excellent DPPH radicals scavenging ability (100% in a concentration of 200 µg/ml) as well as a good effect on reducing coagulation time (at concentrations of 200 and 500 µg/mL reduced clotting time up to 3 min). Considering the fact that green synthesized Cb-AgNPs have antioxidant and antibacterial properties and have a good ability to reduce coagulation time, they can be used in wound dressings. As well as these NPs with good photocatalytic activity can be a suitable option for degrading organic pollutants.

An outstanding photocatalytic performance of CNTs based nanocomposite of ternary metal oxides towards cationic and anionic dyes and pharmaceutical drug

Currently, hetero-metallic oxides and their nanocomposites with 1D materials have a tremendous role in photocatalytic applications, mainly for the removal of organic effluents, due to their higher potential of electron-hole pair migration and separation than pure metal oxide NPs. The present work reports the fabrication of ternary metal oxides nanostructure (WO3·Ag2O·CuO) and its nanocomposite with carbon nanotubes (WO3·Ag2O·CuO/CNTs) using a facile approach i.e. ultra-sonication. The photocatalytic removal efficacy of fabricated nanocomposite i.e. WO3.Ag2O.CuO/CNTs along its counterpart (WO3·Ag2O·CuO) was evaluated using a model cationic dye (Methylene blue, MB), an anionic dye (Congo red, CR), and an analgesic drug (Paracetamol). The catalytic experiment was performed under natural sunlight upon light irradiation of about 90 min and using 30 mg of photocatalyst for all chosen effluents. The obtained results deduced that WO3·Ag2O·CuO/CNTs nanocomposite showed catalytic efficiency of about 97 % for MB, 87 % for CR, and 93 % for Paracetamol while it was about 80 % for MB, 74 % for CR, and 79 % for drug using WO3·Ag2O·CuO as photocatalyst. The rate constant values of nanocomposite for the removal of MB, CR, and Paracetamol are 0.037 min−1, 0.023 min−1, and 0.027 min−1 respectively. The remarkable degradation performance of WO3·Ag2O·CuO/CNTs nanocomposite as compared to ternary metal oxide (WO3·Ag2O·CuO) was due to its high charge separation, high surface area, and availability of large number of active sites for the adsorption of pollutant molecules. Hence, WO3·Ag2O·CuO/CNTs nanocomposite could be a competent photocatalyst for the removal of variety of industrial effluents i.e. organic dyes and pharmaceutical drugs etc.

Charge-Selective Photocatalytic Degradation of Organic Dyes Driven by Naturally Occurring Halloysite Nanotubes

This study explores the use of Halloysite NanoTubes (HNTs) as photocatalysts capable of decomposing organic dyes under exposure to visible or ultraviolet light. Through a systematic series of photocatalytic experiments, we unveil that the photodegradation of Rhodamine B, used as a model cationic dye, is significantly accelerated in the presence of HNTs. We observe that the extent of RhB photocatalytic degradation in 100 min in the presence of the HNTs is ~four times higher compared to that of bare RhB. Moreover, under optimized conditions, the as-extracted photodegradation rate of RhB (~0.0022 min−1) is comparable to that of the previously reported work on the photodegradation of RhB in the presence of tubular nanostructures. A parallel effect is observed for anionic Coumarin photodegradation, albeit less efficiently. Our analysis attributes this discrepancy to the distinct charge states of the two dyes, influencing their attachment sites on HNTs. Cationic Rhodamine B molecules preferentially attach to the outer surface of HNTs, while anionic Coumarin molecules tend to attach to the inner surface. By leveraging the unique properties of HNTs, a family of naturally occurring nanotube structures, this research offers valuable insights for optimizing photocatalytic systems in the pursuit of effective and eco-friendly solutions for environmental remediation.

Efficient Adsorption of Methylene Blue Using a Hierarchically Structured Metal-Organic Framework Derived from Layered Double Hydroxide.

The growing concerns about environmental pollution, particularly water pollution, are causing an increasing alarm in modern society. One promising approach to address this issue involves engineering existing materials to enhance their effectiveness. A one-step solvothermal reconstruction approach was used to build an eco-friendly two-dimensional (2D) AlNiZn-LDH/BDC MOF composite. The characterizations confirm the formation of a metal-organic framework (MOF) at the layered double hydroxide (LDH) surface. The resulting synthesized material, 2D AlNiZn-LDH/BDC MOF, demonstrated remarkable efficacy in decontaminating methylene blue (MB), a model cationic dye found in water systems. The removal performance of 2D AlNiZn-LDH/BDC MOF was significantly higher than that of pristine 2D AlNiZn-LDH. This improvement shows the potential to increase the adsorption capabilities of nanoporous LDH materials by incorporating organic ligands and integrating meso-/microporosity through MOF formation on their surfaces. Furthermore, their kinetic, isothermal, and thermodynamic studies elucidated the adsorption behavior of this composite material. The results of synthesized MOF showed excellent removal efficiency (92.27%) of 10 ppm of MB aqueous solution as compared to pristine LDH. Additionally, the as-synthesized adsorbent could be regenerated for six successive cycles. This method holds promise for the synthesis of novel and highly effective materials to combat water pollution, laying the groundwork for potential advancements in diverse applications.

Preperation of sodium alginate-based SA-g-poly(ITA-co-VBS)/RC hydrogel nanocomposites: And their application towards dye adsorption

A superabsorbent polymer, Sodium Alginate-g-Poly (Itaconic acid-co-Sodium 4-vinyl benzenesulfonate)/ Ricinus communis (SA-g-P(ITA-co-VBS)/ RC) hydrogel, was prepared by free-radical graft co-polymerization for sequestration of toxic malachite green (MG) dye as a cationic dye model. The surface morphological of shape and composition of the prepared hydrogel used have been characterized by FESEM, EDX, TEM, FTIR, X-ray diffraction XRD, and TGA. Optimizing the synthesis conditions for prepared a hydrogel with the highest swelling ratio have been studied, the results show that employing 0.08 g KPS and 0.09 g MBA, 1.0 g ITA, 2.0 g VBS, 1.0 g SA, and 1.0 g RC, the composites greatest swelling capacity in distilled water was 3400 %. It was discovered that the dye adsorption capacity of the polymer was greatly impacted by the monomer VBS level in the hydrogel, which gives it a better ability to swell. The porosity of the hydrogel spheres, thus significantly enhancing the MG adsorption capacity with the rate-limiting controlled by chemical adsorption, intraparticle diffusion, and film diffusion. Study the influence of different reaction conditions on the removal of MG dye from aqueous solution are adsorbent dose, pH, zero-point charge, temperature, thermodynamic adsorption, adsorption isotherm, and kinetic models have been done. Additionally, (SA-g-P(ITA-co-VBS)/RC) demonstrated strong MG dye adsorption capabilities and reusability in at least four adsorption-desorption cycles this process indicating its considerable potential for use as the adsorbent for dye removals from aqueous solution.

Comparative study of physicochemical properties of geopolymers prepared by four Moroccan natural clays

The present work concerns the development of geopolymer materials based on natural clays rich in kaolinite, muscovite and pyrophyllite. The aim was to study the effect of the nature and fraction of the clay minerals composing the raw sample on the physico-chemical properties of the prepared geopolymers, viz., the matrix geopolymer phase fraction, particle size distribution, density, compressive strength and the adsorption capacity of methylene blue (MB) as a cationic dye model. The raw starting clays, their meta-clay phases calcined at 800 °C, and the prepared geopolymers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), particle size distribution (PSD) via laser diffraction method, and scanning electron microscopy (SEM). The matrix geopolymer fraction phase in the samples was qualitatively determined by the analysis of the spectra obtained by 27Al and 29Si solid-state NMR. The results showed that kaolinite-rich clay produced more geopolymer than clays with high phase fractions of muscovite or pyrophyllite and low kaolinite. The highest compressive strength was given by the clay that contained 26.7 % of calcite due to formation of calcium silicate hydrate phase. The maximum adsorption capacity of MB was obtained by the samples have a more heterogeneous surface morphology due to presence of unreacted muscovite and/or pyrophyllite in raw starting clay.

Facile and green construction of carboxymethyl cellulose-based aerogel to efficiently and selectively adsorb cationic dyes

With sodium p-styrene sulfonate (SSS) and acrylic acid (AA) as the organic monomers, a carboxymethyl cellulose (CMC)-based aerogel (named as CMC/PSA) was successfully synthesized by a facile and green method as evidenced by a series of characterizations. The adsorption behaviors of the resulting aerogel were systematically investigated with methylene blue (MB) as the cationic dye model. CMC/PSA aerogel exhibited excellent adsorption performance toward MB with a maximum theoretical adsorption capacity of 925.9 mg/g at 323 K, and the adsorption process could be well simulated by quasi-secondary kinetic model as well as Langmuir model. The aerogel possessed better efficient adsorption capacity toward MB under neutral and alkaline conditions than under acidic environment. In addition, the CMC-based aerogel could achieve the selective removal of cationic dye from a mixture of cationic and anionic dyes. Adsorption capacity of the aerogel decreased only by 3.25 % compared to the initial one even after 6 adsorption-desorption cycles, indicating the excellent recyclable performance. At the practical application level, the dynamic adsorption revealed that the aerogel was highly effective in treating wastewater at the operating time of 2250 min when flow rate of the wastewater was 0.4 L/h. In conclusion, CMC/PSA aerogel could be considered as an ideal adsorbent with green, efficient, selective, and regenerative properties.

Development of carboxymethyl cellulose-graphene oxide biobased composite for the removal of methylene blue cationic dye model contaminate from wastewater

Utilizing Glutaraldehyde crosslinked sodium carboxymethyl cellulose (CMC-GA) hydrogel and its nanographene oxide composite (CMC-GA-GOx), an effective carboxymethyl cellulose-graphene oxide biobased composites adsorbent was developed for the adsorption removal of methylene blue (MB) cationic dye contaminate from industrial wastewater. The CMC-GA-GOx composites developed were characterized using FTIR, RAMAN, TGA, SEM, and EDX analysis instruments. Through batch experiments, several variables affecting the removal of MB dye, including the biocomposites GO:CMC composition, adsorption time, pH and temperature, initial MB concentration, adsorbent dosage, and NaCl concentration, were investigated under different conditions. The maximum dye removal percentages ranged between 93 and 98%. They were obtained using biocomposites CMC-GA-GO102 with 20% GO weight percent, adsorption time 25 min, adsorption temperature 25 °C, MB concentrations 10–30 ppm, adsorption pH 7.0, and 0.2 g adsorbent dose. The experimental data of the adsorption process suit the Langmuir isotherm more closely with a maximal monolayer adsorption capacity of 76.92 mg/g. The adsorption process followed the kinetic model of pseudo-second order. The removal of MB was exothermic and spontaneous from a thermodynamic standpoint. In addition, thermodynamic results demonstrated that adsorption operates most effectively at low temperatures. Finally, the reusability of the developed CMC-GA-GO102 has been proved through 10 successive cycles where only 14% of the MB dye removal percentage was lost. These results suggest that the developed CMC-GA-GO102 composite may be an inexpensive and reusable adsorbent for removing organic cationic dyes from industrial wastewater.

Propensity of a low-cost adsorbent derived from agricultural wastes to interact with cationic dyes in aqueous solutions.

Ash collected from thrown-away by-products while preparing a popular traditional food additive, kolakhar of the Assamese community of North East, India, was used as an alternate cost-effective, porous bioadsorbent option from the conventional activated carbon for the purification of carcinogenic dyes laden water. The base material for kolakhar preparation was taken from the discarded banana stem waste to stimulate agricultural waste management. Methylene blue (MB) and basic fuchsin (BF) dyes were used as model cationic dyes. Characterization techniques like CHN, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), and Brunauer-Emmett-Teller (BET) analysis of the prepared banana stem ash (BSA) reveal the presence of high inorganic contents and functional groups in the irregular, porous bioadsorbent with surface area 55.534 m2g-1. Various regulating parameters studied to optimize the adsorption capacity of BSA were bioadsorbent dose (0.1-3g/L), temperature (298-318K), contact time (0-150min), pH (2-9), and initial dye concentrations (10-40mg/L). Non-linear kinetic models suggested Elovich for both MB and BF adsorption, while the non-linear isotherm model suggested Langmuir and Temkin for MB and BF adsorption, respectively, as best-fitted curves. The monolayer adsorption capacity (qm) for MB and BF was 15.22mg/g and 24.08mg/g at 318K, respectively, with more than 95% removal efficiency for both dyes. The thermodynamic parameters studied indicated that the adsorption is spontaneous. The ∆H0 values of MB and BF adsorptions were 2.303kJ/mol (endothermic) and - 29.238kJ/mol (exothermic), respectively.

High surface area activated carbon from a pineapple (ananas comosus) crown via microwave-ZnCl2 activation for crystal violet and methylene blue dye removal: adsorption optimization and mechanism

In this investigation, microwave irradiation assisted by ZnCl2 was used to transform pineapple crown (PN) waste into mesoporous activated carbon (PNAC). Complementary techniques were employed to examine the physicochemical characteristics of PNAC, including BET, FTIR, SEM-EDX, XRD, and pH at the point-of-zero-charge (pHpzc). PNAC is mesoporous adsorbent with a surface area of 1070 m2/g. The statistical optimization for the adsorption process of two model cationic dyes (methylene blue: MB and, crystal violet: CV) was conducted using the response surface methodology-Box-Behnken design (RSM-BBD). The parameters include solution pH (4–10), contact time (2–12) min, and PNAC dosage (0.02–0.1 g/100 mL). The Freundlich and Langmuir models adequately described the dye adsorption isotherm results for the MB and CV systems, whereas the pseudo-second order kinetic model accounted for the time dependent adsorption results. The maximum adsorption capacity (qmax ) for PNAC with the two tested dyes are listed: 263.9 mg/g for CV and 274.8 mg/g for MB. The unique adsorption mechanism of MB and CV dyes by PNAC implicates multiple contributions to the adsorption process such as pore filling, electrostatic forces, H-bonding, and π-π interactions. This study illustrates the possibility of transforming PN into activated carbon (PNAC) with the potential to remove two cationic dyes from aqueous media.

Adsorption Kinetics of Methyl Orange from Model Polluted Water onto N-Doped Activated Carbons Prepared from N-Containing Polymers.

This study aimed to assess the role of polymeric sources (polypyrrole, polyaniline, and their copolymer) of nitrogen (N)-doped activated carbons (indexed as PAnAC, PPyAC, and PnyAC, respectively) on their adsorption efficiency to remove methyl orange (MO) as a model cationic dye. The adsorbents were characterized using FTIR, SEM, TGA, elemental analysis, and surface area. The kinetic experiments were performed in batches at different MO concentrations (C0) and adsorbent dosages. The adsorption kinetic profiles of pseudo-first-order, pseudo-second-order (PSO), Elovich, intraparticle diffusion, and liquid film diffusion models were compared. The results showed a better fit to the PSO model, suggesting a chemisorption process. The adsorption capacity (qe, mg/g) was found to have increased as MO C0 increased, yet decreased as the adsorbent quantity increased. At the adsorption operating condition, including MO C0 (200 ppm) and adsorbent dose (40 mg), the calculated qe values were in the order of PAnAC (405 mg/g) > PPyAC (204 mg/g) > PnyAC (182 mg/g). This trend proved the carbon precursor's importance in the final properties of the intended carbons; elemental analysis confirmed that the more nitrogen atoms are in the activated carbon, the greater the number of active sites in the adsorbent for accommodating adsorbates. The diffusion mechanism also assumed a rate-limiting step controlled by the film and intraparticle diffusion. Therefore, such an efficient performance may support the target route's usefulness in converting nitrogenous-species waste into valuable materials.

Coal-Based Activated Carbon via Microwave-Assisted ZnCl2 Activation for Methyl Violet 2B Dye Removal: Optimization, Desirability Function, and Adsorption Mechanism

In this work, activated carbon (referred to as MCAC) was produced by microwave radiation assisted ZnCl2 activation using Malaysian coal (MC) as a precursor. The Brunauer–Emmett–Teller findings indicate that the MCAC has a relatively large surface area (798.18 m2/g) and a mesoporous structure (average pore diameter of 3.67 nm). The removal of Methylene Violet (MV 2B) a cationic dye model, was employed to investigate the adsorption properties of MCAC. A numerical desirability function in the Box–Behnken design (BBD) was employed to optimize the independent crucial adsorption variables as follows: A: MCAC dose (0.02–0.1 g); B: pH (4–10); and C: time (5–25 min). The results of equilibrium and dynamic adsorption showed that the adsorption of MV 2B followed Freundlich and pseudo-second order models, respectively. The maximum amount of MV 2B dye that the MCAC could adsorb (qmax) was 134.1 mg/g. Electrostatic interactions, π-π stacking, H-bonding, and pore diffusion contribute to the adsorption of MV 2B dye onto the MCAC surface. This study demonstrates the potential to utilize MC as a low-cost precursor for the efficient synthesis of MAC and its utility for the removal of pollutants.

Chromochloris zofingiensis microalgae as a potential dye adsorbent: Adsorption thermo-kinetic, isothermal, and process optimization

In this study, the microalgae Chromochloris zofingiensis (ChZ) was harvested and used as a biosorbent for the removal of methylene blue (MB) as a model cationic dye from water. The ChZ was characterized via FTIR, FESEM-EDX, XRD and BET analyses. Response Surface Methodology, based on Central Composite Design was employed to optimize the batch adsorption process, including independent variables of biosorbent dosage, initial MB concentration and pH of the solution to maximize the MB removal percentage. The maximum removal of 97 % was obtained at the optimal conditions i.e., biosorbent dosage of 0.72 g/L, pH of 10 and initial MB concentration of 15.12 mg/L, with >97 % confidence limit. Pareto sensitivity analysis uncovered that the biosorbent dosage has the greatest impact (50 %) on MB removal. The adsorption kinetic was better described by the pseudo-second-order model among the different kinetic models applied i.e., pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models. The adsorption equilibrium was also modeled using the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin isotherms. The Langmuir model provided the best fit and the maximum sorption capacity of 135.42 mg/g was recorded. Principle thermodynamic criteria including ΔGo, ΔHo and ΔSo were computed for the biosorption. The results uncovered that the biosorption of MB using ChZ is spontaneous and exothermic. Generally, the results indicated that ChZ microalga can be considered an effective biosorbent for dye-contaminated water remediation.

Synthesis and Characterization of Orange Peel Modified Hydrogels as Efficient Adsorbents for Methylene Blue (MB)

In recent years, due to the developments in the textile industry, water contaminated with synthetic dyes such as methylene blue (MB) has become an environmental threat based on the possible impacts in terms of chemical and biochemical demand, which leads to disturbance in aquatic plants photosynthesis, besides their possible toxicity and carcinogenicity for humans. In this work, an adsorbent hydrogel is prepared via free radical polymerization comprising acrylic acid (PAA) as a monomer and orange peel (OP) as a natural modifier rich in OH and COOH present in its cellulose and pectin content. The resulting hydrogels were optimized in terms of the content of OP and the number of cross-linkers and characterized morphologically using Scanning electron microscopy. Furthermore, BET analysis was used to follow the variation in the porosity and in terms of the surface area of the modified hydrogel. The adsorption behavior was found to follow pseudo-second-order as a kinetic model, and Langmuir, Freundlich, and Temkin isotherm models. The combination of OP and PAA has sharply enhanced the adsorption percent of the hydrogel to reach 84% at the first 10 min of incubation with an adsorption capacity of more than 1.93 gm/gm. Due to its low value of pHPZc, the desorption of MB was efficiently performed at pH 2 using HCl, and the desorbed OP-PAA were found to be reusable up to ten times without a decrease in their efficiency. Accordingly, OP-PAA hydrogel represents a promising efficient, cost-effective, and environmentally friendly adsorbent for MB as a model cationic dye that can be applied for the treatment of contaminated waters.

Design of [BmIm]3PW12O40 Ionic Liquid Encapsulated-ZIF-8 Nanocomposite for Cationic Dye Adsorptive Removal: Modeling by Response Surface Methodology

In this study, the modification of metal–organic frameworks with polyoxometalate-based ionic liquids was assessed and their efficient role in the improvement of their adsorption performance was studied. Metal–organic framework ZIF-8 was encapsulated with [BmIm]3PW12O40, a polyoxometalate-based ionic liquid, through reaction with the ZIF-8 imidazolate groups. The novel ZIF-8-[BmIm]3PW12O40 nanocomposite was characterized using XRD, FTIR, SEM, EDX, and BET analyses, which confirmed the successful insertion of [BmIm]3PW12O40 on the surface of the ZIF-8 structure. It was used to study the adsorptive removal of a methylene blue (MB) cationic dye model and showed high adsorption performance between pH 2 and 11 with an optimum sorbent dosage of 4 g/L. The adsorption kinetics corresponded well to the pseudo-second-order kinetic model. Moreover, response surface methodology was used to optimize experimental conditions and determine the highest MB removal percentage. The correlation between variables (time, pH, and sorbent dosage) and responses (removal percentage) were well fitted to the second-order polynomial model (R2 = 0.949, Adj. R2 = 0.9032, and pred. R2 = 0.6129). The optimal conditions were found to be adsorbent amount = 0.04 g/L, pH = 11, and contact time = 45 min. Under these conditions, the highest removal percentage and amount of desirability were found to be 95.75% and 0.9, respectively.

Mesoporous activated carbon produced from mixed wastes of oil palm frond and palm kernel shell using microwave radiation-assisted K2CO3 activation for methylene blue dye removal: Optimization by response surface methodology

Employing agricultural waste to develop activated carbon through convenient and environment friendly procedures is an excellent approach to conducting green and sustainable development. In this work, a mesoporous activated carbon (hereinafter, abbreviated as OPFPKSAC) was developed by microwave radiation-assisted K2CO3 activation of agricultural wastes including oil palm frond (OPF) and palm kernel shell (PKS). Evaluation of the adsorptive performance of OPFPKSAC was obtained by the removal of a model cationic dye (methylene blue, MB). Box-Behnken design (BBD) was implemented for optimizing the critical adsorption factors including OPFPKSAC dosage, [MB] dye, pH, and time. The BBD model found that the maximum MB removal (99.6 %) occurred under the circumstances of the OPFPKSAC dosage (0.06 g), [MB] dye (10 mg/L), pH (10), and time (20 min). The adsorption equilibrium data is consistent with the Freundlich model, and both the pseudo-first-order and pseudo-second-order models could adequately explain the kinetic data. OPFPKSAC exhibited an outstanding adsorption capability of 331.6 mg/g. Multiple mechanisms like electrostatic forces, pore filling, H-bonding, and π-π stacking, are involved in the MB dye adsorption on the OPFPKSAC's surface. This research demonstrates that the OPFPKSAC, with its environmentally benign synthesizing, low cost, high efficiency, and ease of use, is a promising adsorbent for the removal of toxic pollutants.

Adsorptive Removal of Methylene Blue Dye Using Biowaste Materials: Barley Bran and Enset Midrib Leaf

In this study, several biowaste materials are screened for adsorptive removal of methylene blue (MB) from synthetic water. Among the tested adsorbents, barley (Hordeum vulgare) bran (BB) and enset (Ensete ventricosum midrib leaf, EVML) were selected for further evaluation of MB (a model cationic dye) adsorption. Batch MB adsorption performance of BB and EVML adsorbents was significantly high in a wide pH range (4-9). The well fitting of experimental data with pseudosecond-order kinetic model suggests a monolayer adsorption of MB. The MB adsorption onto both adsorbents was fit well with the Langmuir isotherm model with maximum MB adsorption capacities of 63.2 mg/g (BB) and 35.5 mg/g (EVML). The biowaste materials exhibit considerable adsorption capacity for cationic dye (MB), perform well under acidic and basic conditions, and are reusable. Therefore, the use of these materials as adsorbents may have an environmental benefit in terms of the conversion of wastes into valuable materials. Further studies are suggested to investigate the performance of these adsorbents in a continuous mode using real wastewater.

Black wattle tannin‐immobilized mesostructured collagen as a promising adsorbent for cationic organic dyes (methylene blue) removal in batch and continuous fixed‐bed systems

AbstractBlack wattle tannin‐immobilized mesostructured collagen (TC) was synthesized by using exfoliated mesostructured collagen as carriers. The structure of TC was characterized by scanning electron microscope, Fourier transform infrared spectroscopy and zeta potential test. Methylene blue (MB) as a cationic dye model was applied to evaluate the adsorption ability of TC through batch and continuous fixed‐bed system experiments. Results of batch adsorption experiment indicated that the adsorption behaviors of TC conformed to the Freundlich isotherm model and the pseudo‐second‐order kinetic model as well as the intraparticle diffusion model. The maximum adsorption amount (Qmax) of TC was 46.5 mg/g at 303 K. Fixed‐bed adsorption experiments revealed that the initial concentration, flow rate, and column height significantly influenced the removal of MB, and all breakthrough curves were well fitted by Thomas and Yoon‐Nelson models. Adsorption–desorption experiments demonstrated that TC possessed excellent stability and reusable ability. The removal efficiency of MB was still above 80% after five adsorption–desorption cycles. The excellent adsorption capacity of TC owed to the immobilized tannins as binding sites to MB and support of mesostructured collagen with hierarchical structure. This work developed a novel collagen‐based adsorption material for efficient removal of cationic dye.

Rapid adsorption of dyes from aqueous solutions by modified lignin derived superparamagnetic composites

In recent years, lignin has gotten a lot of press as an adsorbent for treating organic dyes. However, lignin adsorption has problems such as low adsorption capacity, slow adsorption and difficult recovery. In this study, a simple method was used to prepare superparamagnetic composites by self-assembly of enzymatic lignin (EL) or its modification products with γ-Fe2O3 nanoparticles under electrostatic interactions. Then the effect of the adsorbents in removing the methylene blue (MB, as a model cationic dye) and Congo red (CR, as a model anionic dye) from aqueous solutions was investigated by detailed characterization and experiments. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibration sample magnetometer (VSM). In the process of adsorption, the effects of the initial pH and inorganic ions concentration of the dyes were discussed. And the adsorption mechanisms such as kinetics, isotherm were explored. The results showed that the synthesized magnetic acetylated modified lignin (MADL) has a well-defined spherical structure. In the adsorption kinetics study, MADL demonstrated a fast adsorption capacity. it took less than 50 min to reach the equilibrium. MADL maintained a stable adsorption capacity at a wide pH range and showed >90% removal efficiency in higher concentration (0.5 mol/L) of inorganic ions solutions. Moreover, MADL has good recyclability, can be separated from water quickly by the action of the applied magnetic field and still has >94% regeneration efficiency after three times of desorption and regeneration. In summary, the novel magnetic lignin-based adsorbent material prepared in this study has the advantages of simple preparation process, rapid adsorption, stability and good recyclability, which provides a new way for the removal of dyes in practical applications.