Adsorption Capacity For Methyl Orange Research Articles

Adsorptive removal of synthetic dye from its aqueous solution by using chitosan-bentonite composite: DFT and experimental studies

AbstractThis research investigates the adsorption efficiency of a chitosan-bentonite (Ch–B) composite in removing methyl orange (MO), a common textile dye, from aqueous solutions. The study integrates experimental and theoretical analyses, employing density functional theory (DFT) to gain insights into the molecular interactions between the composite material and MO molecules. The Ch–B composite was characterized using various techniques, including FT-IR spectroscopy, XRD, and SEM–EDX. The experimental results indicate that the Ch–B composite exhibits a high adsorption capacity for MO, with optimal conditions identified for efficient removal. The Langmuir model was found to best fit the experimental data and the adsorption capacity was 117 mg g−1. Adsorption thermodynamics showed that the adsorption process was spontaneous, feasible, and exothermic. DFT calculation results are correlated with experimental findings to confirm theoretical predictions and improve the overall understanding of the adsorption process. Electronic structure calculations reveal the nature of the interactions between the Ch–B composite and MO molecules, including hydrogen bonds and electrostatic forces.

Magnetic Magnetite-Graphene Oxide (Fe3O4-GO) Nanocomposites for Removal of Dyes from Aqueous Solution

AbstractMagnetic magnetite-graphene oxide (Fe3O4-GO) was synthesized using an in-situ precipitation technique and applied in the adsorption of cationic rhodamine B (RhB) and anionic methyl orange (MO) dyes from aqueous solution. The nanocomposite was characterized by different techniques including FTIR, XRD, Raman, XPS, PPMS, BET, SEM and TEM techniques. Batch adsorption studies were conducted to investigate the effect of solution pH, initial metal ion concentration, adsorbent dosage and contact time. The synthesized Fe3O4-GO exhibited characteristic magnetic properties (saturation magnetization of 34 emu/g) and it separated from aqueous solution with ease through the application of an external magnetic field. The adsorption equilibrium time on the adsorption of RhB and MO onto Fe3O4-GO showed best removal of 99.12% for RhB after 60 min, while MO was removed efficiently after 120 min with a removal efficiency of 97.60%. The adsorption of the azo dyes followed the pseudo-second-order kinetics model with high correlation coefficients (0.99995) for RhB and (0.99925) for MO. Maximum removal of the dye pollutants by occurred at pH 8 for RhB and pH 4 for MO, while the optimal adsorbent dosage was 30 mg. The results showed that adsorption equilibrium data were fitted to Langmuir isotherm model and maximum monolayer adsorption capacities for RhB and MO at 70.64 and 15.94 mgg−1, respectively. The magnetic adsorbents were reused for a maximum of 7 cycles and showed reasonable stability and reproducibility. Furthermore, the results showed that Fe3O4-GO nanocomposite can be used as an effective material in the removal of dyes from wastewater.

Enhanced Adsorption of Methyl Orange from Aqueous Phase Using Chitosan-Palmer Amaranth Biochar Composite Microspheres.

To develop valuable applications for the invasive weed Palmer amaranth, we utilized it as a novel biochar source and explored its potential for methyl orange adsorption through the synthesis of chitosan-encapsulated Palmer amaranth biochar composite microspheres. Firstly, the prepared microspheres were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy and were demonstrated to have a surface area of 19.6 m2/g, a total pore volume of 0.0664 cm3/g and an average pore diameter of 10.6 nm. Then, the influences of pH, dosage and salt type and concentration on the adsorption efficiency were systematically investigated alongside the adsorption kinetics, isotherms, and thermodynamics. The results reveal that the highest adsorption capacity of methyl orange was obtained at pH 4.0. The adsorption process was well fitted by a pseudo-second-order kinetic model and the Langmuir isotherm model, and was spontaneous and endothermic. Through the Langmuir model, the maximal adsorption capacities of methyl orange were calculated as 495.0, 537.1 and 554.3 mg/g at 25.0, 35.0 and 45.0 °C, respectively. Subsequently, the adsorption mechanisms were elucidated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy investigations. It is indicated that electrostatic interactions, hydrogen bonding, π-π interactions and hydrophobic interactions between methyl orange and the composite microspheres were pivotal for the adsorption process. Finally, the regeneration studies demonstrated that after five adsorption-desorption cycles, the microspheres still maintained 93.6% of their initial adsorption capacity for methyl orange. This work not only presents a promising method for mitigating methyl orange pollution but also offers a sustainable approach to managing Palmer amaranth invasion.

Adsorption of anionic dyes from aqueous solutions by a novel CTAB/MXene/carbon nanotube composite: Characterization, experiments, and theoretical analysis

A novel three-dimensional composite was prepared by the self-assembly of MXene nanosheets and carbon nanotubes (CNTs) with the assistance of cetyltrimethylammonium bromide (CTAB), which was named as CMC composite. Adsorption of three anionic dyes, including Acid orange (AO7), Methyl orange (MO) and Congo red (CR), from aqueous solutions on the composite and the mechanisms were investigated in this study. Compared with MXene and CNTs, the CMC composite exhibited superior adsorption performance for AO7, MO and CR with maximum adsorption capacities of 367.9, 294.2, and 628.5 mg/g, respectively. The adsorption capacities of AO7 and MO on the CMC composite decreased, while that of CR increased with increasing temperatures. Quantum chemical calculations indicated that electrostatic interactions, π-π electron-donor-acceptor interactions and hydrogen bonding played important roles on the adsorption. The approximate site energy distribution analysis demonstrated that more adsorption active sites existed on the CMC composite than on MXene and CNTs, which endowed the CMC composite with higher adsorption capacities for these anionic dyes. The differences of adsorption behaviors for three anionic dyes could be ascribed to the number of available adsorption sites and the change of the site heterogeneity on the CMC surface.

Facile synthesis of lignin-based Fe-MOF for fast adsorption of methyl orange

To rapidly remove dyes from wastewater, iron-based metal–organic frameworks modified with phenolated lignin (NH2-MIL@L) were prepared by a one-step hydrothermal method. Analyses of the chemical structure and adsorption mechanism of the NH2-MIL@L proved the successful introduction of lignin and the enhancement of its adsorption sites. Compared with NH2-MIL-101-Fe without phenolated lignin, the modification with lignin increased the methyl orange (MO) adsorption rate of NH2-MIL@L. For the best adsorbent, NH2-MIL@L4, the MO adsorption efficiency in MO solution reached 95.09% within 5 min. NH2-MIL@L4 reached adsorption equilibrium within 90 min, exhibiting an MO adsorption capacity of 195.31 mg/g. The process followed pseudo-second-order kinetics and the Dubinin-Radushkevich model. MO adsorption efficiency of NH2-MIL@L4 was maintained at 89.87% after six adsorption-desorption cycles. In mixed solutions of MO and methylene blue (MB), NH2-MIL@L4 achieved an MO adsorption of 94.02% at 5 min and reached MO adsorption equilibrium within 15 min with an MO adsorption capacity of 438.6 mg/g, while the MB adsorption equilibrium was established at 90 min with an MB adsorption rate and capacity of 95.60% and 481.34 mg/g, respectively. NH2-MIL@L4 sustained its excellent adsorption efficiency after six adsorption-desorption cycles (91.2% for MO and 93.4% for MB). The process of MO adsorption by NH2-MIL@L4 followed the Temkin model and pseudo-second-order kinetics, while MB adsorption followed the Dubinin-Radushkevich model and pseudo-second-order kinetics. Electrostatic interactions, π-π interactions, hydrogen bonding, and synergistic interactions affected the MO adsorption process of NH2-MIL@L4.

Ferrocene crosslinked and functionalized chitosan microspheres towards bio-based Fenton-like system for the removal of organic pollutants

Dye-containing wastewater treatment has been a major long-term global challenge. For this purpose, a novel bio-based microspheres (CS-FC) with high specific surface area (63.24 m2·g−1) and nano-channels (17.95 nm) was prepared using chitosan as the framework and ferrocene as a crosslinking active group. CS-FC not only has the ability to rapidly enrich methyl orange (MO) through hydrogen-bonding and electrostatic attraction, but also almost completely degrades it in the presence of H2O2/K2S2O8 through a synergistic radical/non-radical mechanism under the activating effect of ferrocene. Without H2O2/K2S2O8, the maximum MO adsorption capacity of CS-FC is in the range 871–1050 mg·g−1, and conforms to a Langmuir isothermal model with pseudo-second-order kinetics. In the presence of H2O2/K2S2O8, the removal of MO dramatically increased from 32 % to nearly 100 % after incubation for 60 min, due to the simultaneous formation of highly reactive 1O2 and ·OH. The significant contribution from 1O2 endowed CS-FC/H2O2/K2S2O8 with high universality for degrading various organic pollutants (including azo dyes and antibiotics), a wide pH window (2–8), and low sensitivity to co-existing ions. Such cost-effective, recyclable porous bio-based microspheres are suitable for heterogeneous Fenton-like catalysis in organic wastewater treatment that rely on synergistic radical/non-radical reaction pathways.

Adsorptive removal of organic pollutants from aqueous solutions using novel GO/bentonite/MgFeAl-LTH nanocomposite

The contamination of water with organic pollutants such as dyes and phenols is a serious environmental problem, requiring effective treatment methods. In the present study, a novel nanocomposite was synthesized by intercalating graphene oxide and bentonite clay into MgFeAl-layered triple hydroxide (GO/BENT/LTH), which was characterized using different techniques. The adsorption efficacy of the GO/BENT/LTH nanocomposite was assessed via the removal of two harmful organic water pollutants, namely methyl orange (MO) and 2-nitrophenol (2NP). The obtained results revealed that the maximum adsorption capacities (qmax) of MO and 2NP reached 3106.3 and 2063.5 mg/g, respectively, demonstrating the excellent adsorption performance of the nanocomposite. Furthermore, this study examined the effects of contact time, initial MO and 2NP concentrations, pH, and temperature of the wastewater samples on the adsorptive removal of MO and 2NP by the GO/BENT/LTH nanocomposite. The pH, zeta potential, and FTIR investigations suggested the presence of more than one adsorption mechanism. Thermodynamic investigations elucidated the exothermic nature of the adsorption of MO and 2NP onto the GO/BENT/LTH nanocomposite, with MO adsorption being more sensitive to temperature change. Additionally, regeneration studies revealed a marginal loss in the MO and 2NP removal with the repetitive use of the GO/BENT/LTH nanocomposite, demonstrating its reusability. Overall, the findings of this study reveal the promise of the GO/BENT/LTH nanocomposite for effective water decontamination.

Adsorption of anionic and cationic azo dyes from wastewater using novel and effective multicomponent adsorbent

Water pollution is rising worldwide, necessitating innovative and effective treatment solutions. This study introduces a multicomponent/multifunctional novel nanocomposite synthesized from polyethyleneimine (PEI), graphene oxide (GO), bentonite clay, and MgFeAl-layered triple hydroxide (LTH), termed as AGO/Bentonite/LTH. In this study, the synthesized AGO/Bentonite/LTH nanocomposite was utilized to remove azo dyes (methyl orange and crystal violet) from contaminated water samples. The novel AGO/Bentonite/LTH nanocomposite was benchmarked against its pristine materials and their binary combinations. The results indicated the superior adsorption performance of the AGO/Bentonite/LTH nanocomposite relative to all other adsorbents synthesized and examined herein. All the synthesized adsorbents were characterized using different techniques in order to reveal their textural properties, functional groups, morphology, thermal stability, and crystallinity before applying them to decontaminate wastewater samples contaminated with methyl orange (MO) and crystal violet (CV). The Langmuir adsorption isotherm model predicted that the maximum adsorption capacities of CV and MO onto the AGO/Bentonite/LTH nanocomposite are 1705.1 and 1171.8 mg/g, respectively. On the other hand, zeta potential, pH, and FTIR studies suggested the existence of multiple mechanisms governing the adsorption of CV and MO onto the AGO/Bentonite/LTH nanocomposite. Thermodynamic results indicated the endothermicity and exothermicity of CV and MO adsorption, respectively. Another interesting finding reported herein is the high reusability of this nanocomposite as demonstrated by the minimal reduction in the removal of these two pollutants with the repetitive use of the nanocomposite. Additionally, the nanocomposite can also be easily and cheaply regenerated via a few rinses with a diluted NaOH aqueous solution. These interesting observations suggest that the synthesized AGO/Bentonite/LTH nanocomposite is a potent material for efficient dye removal from contaminated water bodies.

Preparation of cationic surfactant modified two-dimensional (2D) multi-layered Ti3C2Tx MXene for methyl orange removal from aqueous solution: Kinetic, equilibrium, and adsorption mechanisms

In this study, cetyltrimethylammonium bromide-modified multi-layered Ti3C2Tx MXene (CMM) was produced using a Ti3AlC2 precursor, and its capacity to remove the anionic dye, methyl orange (MO), was investigated in detail. An electrostatic combination between negatively charged Ti3C2Tx nanosheets and cationic surfactant solution (CTAB) produced this adsorbent. This triggered an exposure of the accessible active sites to further boost adsorption effectiveness by increasing the distance between the MXene nanosheets. Prepared adsorbents were characterized using some analytical techniques, including TGA, FESEM, EDX, FTIR, XRD, and N2 adsorption-desorption. Furthermore, some influencing parameters such as contact time, solution of pH, loading adsorbent, and initial dye concentration were evaluated, with findings showing that MO could adsorb CMM to its maximum capacity at an adsorbent dosage of 0.83 g/L, a contact time of 90 min, and a solution pH of 3. Adsorption results were found to be highly linked with both Langmuir isotherm (R2 = 0.9990) and the pseudo-second-order kinetic model (R2 = 0.9924). The maximum adsorption capacity of MO was obtained at approximately 213.00 mg/g. Also, hydrogen bonding, π-cation interactions, and electrostatic adsorption can all be implicated in the mechanism of MO adsorption on CMM. The fabricated CMM is presented as a prospective adsorbent for the removal of dyes from polluted water, demonstrating robust recyclability for up to the fifth iteration. All these outstanding properties indicate that cetyltrimethylammonium bromide-modified multi-layered Ti3C2Tx MXene can be considered as applicable adsorbents for textile pollutants.

Gemini Quaternary Ammonium Surfactants with Different Counterions-modified Montmorillonite for Efficient Removal of Methyl Orange.

Organic Na-montmorillonite (OMt-12-2-12·2Y - , Y=CH 3 CO 3 - , C 6 H 5 COO - and Br - ) modified by a series of Gemini quaternary ammonium surfactants with different counterions was prepared for enhancing the adsorption capacity of methyl orange. Compared with the initial adsorption capacity of 5.251 mg/g of Na-Mt, the adsorption effect of OMts under the optimal conditions increased by about 31~34 times. The adsorption isotherms and kinetics of all adsorption processes were respectively described by Langmuir and pseudo-second-order models. The structure, hydrophobicity and hydration of the counterions, as well as the affinity of the counterions with the long aliphatic chains, had a certain influence on the adsorption performance of OMts for methyl orange.

Selective separation of methylene blue from aqueous solution using Mn/Pd decorated chemically modified MoS2 nanocomposites

The presence of dyes in wastewater is posing as serious threat to human health. There are a huge number of physical, chemical, biological and hybrid methods available for the removal of colorants (dyes) from aqueous environment. In this work, we demonstrate the fabrication of new nanocomposites, MoS2-COOH/gly@M (M= Mn, Pd), with high adsorption property fabricated by chemically immobilizing manganese and palladium metallic centers onto the glycine- modified molybdenum disulfide (MoS2) material. The chemical and physical properties of adsorbents were analyzed using Fourier transform infrared spectrometer (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) companied by energy dispersive X-ray and mapping (EDAX & MAP) analyses. Zeta potential (ξ) technique was also used to measure the surface charge of adsorbents. Performances of nanocomposites were investigated on the sewage as adsorbent for dye removal. Synthesized nanocomposites revealed selective adsorption of methylene blue (MB) dye from aqueous mixture of MB and methyl orange (MO). Results displayed the equivalent high adsorption capacity for MB and MO up to 553 and 619 mg/g, respectively (green reaction condition= 120 min contact time, ,25 °C, pH 2.0 and pH 7.0, in the presence of 2 mg adsorbent and 50 mg/L (30 mL) initial concentration of MO and MB). The remarkable adsorption capacity of dye by MoS2-COOH/gly@M (M= Mn, Pd) nanocomposites can be attributed to the intermolecular interactions due to the presence of the amine, hydroxyl, and carboxyl functionalities. To describe the adsorption mechanism of MO and MB dye by synthesized nanomaterials, the pseudo-first-order and pseudo-second-order kinetics were further studied. Isotherm models displayed that the adsorption of MB and MO onto the MoS2-COOH/gly@M (M= Mn, Pd) nanocomposites is more correspondent with the Freundlich model with high-correlation coefficients. The results showed that the electrostatic attraction and H-bonding interaction were the basic cause of the adsorption of these anionic and cationic dyes on the surface of the nanocomposites. One of the distinguished properties of adsorbents is their capability to selectively adsorb MB from an admixture of MO and MB. The adsorption selectively has expanded in the following order: MoS2 < MoS2-COOH/gly@Mn < MoS2-COOH/gly@Pd. Based on the results, this new type of nanocomposites has potential to act as an effective and affordable adsorbent material for dye removal from an industrial sewage.

N-halamine modified poly(amidoxime) nanofibrous antibacterial adsorbents for the extraction of copper ions and dyes from aqueous medium

Wastewater with contaminants such as heavy ions, organic dyes, and bacteria is extremely damaging to the environment and human life. In this study, N-halamine modified poly(amidoxime) nanofibrous membranes (PAO-Cl) were prepared using amidoxime-modified polyacrylonitrile (PAN), followed by chlorination. The amidoxime conditions of PAN were investigated, and the micromorphologies of each sample were examined. The durability, water release properties, antibacterial activities, and adsorption properties of the Cu2+ ions and methyl orange(MO) were investigated. The results demonstrated that PAO and PAO-Cl exhibited an adsorption capacity toward Cu2+ ions and MO, respectively. Chlorination of PAO resulted in the loss of Cu2+ ion adsorption properties of PAO-Cl. Nevertheless, PAO-Cl presented a higher MO adsorption capacity than poly(amidoxime) nanofibrous membranes (PAO). When the pH value less than 4, the adsorption properties of PAO-Cl was significantly enhanced, and the adsorption process was optimal, as described by the pseudo-second-order kinetic and Langmuir models. For PAO-Cl, the chemical structure changes and adsorption mechanism toward MO were thoroughly studied. After 5 min of contact time, the chlorinated sample displayed excellent antimicrobial capacities against 100 % of S. aureus (6.2 log) and E. coli O157:H7 (6.0 log), making it a promising candidate for use in water disinfection fields.

Effect of Bark Biochars on Properties of Steam-Activated Carbons

Bark is a heterogeneous solid material comprising mainly of phloem and cork fractions. These fractions differ in chemical composition and anatomical structure, and value-added activated carbons produced from these fractions have different surface properties. Low-temperature pyrolysis was shown to be a promising method for producing activated carbon precursors from bark fractions at higher yields than conventional slow pyrolysis. Here, we produced mesoporous activated carbons (ACs) from cork and phloem fractions of Quercus cerris bark by low-temperature pyrolysis followed by steam activation at 900 °C. The results showed steam-activation of biochars from Q. cerris bark fractions yielded ACs with acceptable surface properties. The ACs contained 9.9% and 23.3% ash content, and specific surface areas of 201 m2 g−1 and 512 m2 g−1 for cork and phloem fractions, respectively. Calcium was the principal inorganic component of ACs, followed by potassium, silicon, and iron. Surface functional groups of bark fractions and biochars were lost during steam activation, as evidenced by FT-IR spectroscopy. The burnout temperatures of cork and phloem ACs were 726 °C and 736 °C, respectively. The ACs showed a high methylene blue and methyl orange adsorption capacity, with the removal of 80% and 90% of methylene blue and 58% and 68% of methyl orange after 48 h for cork and phloem ACs, respectively.

Adsorption mechanism of different dyes on chemical activated carbon as quantitative assessment for wastewater treatment: Comparative study between ZnCl2 and its eutectic

A recent development in the field of activated carbon is chemical activation via physical mixing using molten salts. Previous research discussed the differences in characteristics of activated carbons from pinewood created by pure ZnCl2 and its eutectic mixture of ZnCl2-KCl-NaCl (60:20:20 mol %). Herein a contrast in mesoporous pore size distribution and its corresponding surface area was discovered. ZnCl2 generates a higher surface area over a broad pore range whereas the eutectic creates lower surface area but with a distinctive narrow peak in the larger mesopores. The question remains whether this difference in pore distribution and surface area has an impact on the adsorption mechanism. For this instance, the effect of varying pH on adsorption was tested for methylene blue (cationic), neutral red (neutral) and methyl orange (anionic). Next to that, the adsorption kinetics and equilibrium were investigated using methyl orange and brilliant blue FCF. The latter is also anionic but larger in size and molecular weight compared to the former. A variety of adsorption models were compared to the obtained adsorption data. The pseudo-second-order model provided the best description of adsorption kinetics with both dyes. Highest adsorption in this case was noted for carbons activated with the eutectic mixture, amounting to 229.6 mg/g for methyl orange and 121.8 mg/g for brilliant blue FCF. Regarding the adsorption equilibrium, adsorption of methyl orange obtained the best fit with the Langmuir model. Adsorption of brilliant blue on the other hand had the best correlation with the Fowler-Guggenheim model, which accounts for lateral interactions between adsorbate molecules. Again, the eutectic treated carbons showed the most promising results, amounting to 447.5 mg/g and 146.4 mg/g for methyl orange and brilliant blue FCF, respectively. Furthermore, removal efficiency was determined and mass transfer resistance that might have occurred during adsorption, were investigated for both anionic dyes. Finally, regeneration of the carbons was examined. After 3 cycles, the carbons treated with the eutectic mixture maintained 60.7 and 49.1 % of their original adsorption capacity of methyl orange and brilliant blue, respectively, while this amounted to 65.9 and 46.3 % for the ZnCl2 activated carbons. This research shows that adsorption capacity not solely relies on the adsorbents surface area but is also dependent on the pore distribution. Bearing this in mind, it can be stated that eutectic salt mixtures can serve as useful activating agents for tailor-made activated carbons suitable for wastewater treatment.

Ensemble meta machine learning for predicting the adsorption of anionic and cationic dyes from aqueous solutions using Polymer/graphene/clay/MgFeAl-LTH nanocomposite

Adsorption is one of the most promising wastewater treatment methods due to its simplicity and efficacy at ambient temperature and pressure. However, the technical and economic feasibility of this process largely depends on the performance of the utilized adsorbents. In this study, a promising adsorbent made of polyethyleneimine, graphene oxide (GO), bentonite, and MgFeAl-layered triple hydroxide (MgFeAl-LTH) has been synthesized and characterized. The results revealed that the synthesized nanocomposite (abbreviated as PGB-LTH) possesses good porosity and crystallinity. The adsorption performance of the PGB-LTH nanocomposite towards two harmful water pollutants (i.e., methyl orange (MO) and crystal violet (CV)) was investigated, and the results revealed that the nanocomposite outperforms its parental materials (i.e., GO, bentonite, and MgFeAl-LTH). The maximum adsorption capacity (qmax) of MO and CV onto the nanocomposite could reach 1666.7 and 1250.0 mg/g, respectively, as predicted using the Langmuir adsorption isotherm. Additionally, the PGB-LTH nanocomposite is highly reusable with an insignificant decline in performance upon repetitive use. In terms of thermodynamics, MO adsorption onto the nanocomposite is exothermic while CV adsorption is endothermic despite that both dyes adsorb spontaneously as revealed by the negative values of the Gibbs free energy change at all the examined temperatures. The generated adsorption data were utilized for constructing and assessing ensemble meta-machine learning techniques aimed at cost-effective simulation and prediction of the proposed adsorption method. Bagging and boosting methods were developed and evaluated intensively using the obtained adsorption data. The Extra Trees model achieved promising results as evidenced by the high correlation coefficient of 99% as well as low computed RMSE and MAE errors of 11.42 and 5.11, respectively, during the testing phase. These results demonstrate the model strong capability to effectively simulate and predict the adsorption process in question.

Biochar obtained from alkaline earth metal-treated mushroom residue: Thermal behavior and methyl orange adsorption capability

To achieve the resource utilization of edible fungi residue and obtain efficient adsorbents for treating dyeing wastewater, biochars were prepared from mushroom residue (MR) with the introduction of alkaline-earth metals (AEMs) and used for methyl orange (MO) wastewater treatment. The thermal behavior of the AEM-treated MR was analyzed using thermogravimetric analysis. The physicochemical properties of the biochars obtained from AEM-treated MR (MRCs) were characterized using Fourier transform infrared spectroscopy, laser particle size analyzer, N2 adsorption/desorption, and scanning electron microscopy. The adsorption performance of MRCs on MO was also investigated. The involvement of AEMs was found to obviously move the main pyrolysis zone of MR to a low temperature region and reduce the temperature corresponding to the maximum weight loss rate and activation energy, which is highly dependent on the concentration of AEMs, the anion and cationic species of the AEMs. Moreover, the addition of AEMs resulted in a decrease in oxygen-containing functional groups (-OH, CO, or C–O), a weakening of surface negative charges, an enhancement in aromatic functional groups, and an increase in specific surface area of the MRCs. The adsorption performance of MO on MRCs was significantly improved with the introduction of AEMs as well. Among them, MR pre-treated with 5 mmol/g MgCl2 (MR-MgCl2-5) shows the lowest temperature corresponding to the maximum weight loss rate and the lowest activation energy of 278.52 °C and 4.28 kJ/mol, respectively. The biochar prepared from MR-MgCl2-5 under 400 °C (MR-MgCl2-5-400C) has the weakest surface negative charge and the highest adsorption capacity for MO. The adsorption isotherms, adsorption kinetics, and thermodynamic analysis results showed that the adsorption of MO on MR-MgCl2-5-400C was a spontaneous, chemically dominant monolayer adsorption, with a theoretical maximum adsorption capacity of 81.30 mg/g. This study suggests that AEMs treatment, especially with 5 mmol/g MgCl2, can readily transform edible fungi residue into a low-cost, high-efficient dyeing wastewater adsorbent.

Adsorbent effectiveness of α-cellulose/humatic acid with epichlorohydrin cross-linking agent on methyl orange dye

Adsorption of methyl orange (MO) using epichlorohydrin cross-linked humic acid/cellulose composite has been carried out. This study aims to synthesize epichlorohydrin cross-linked humic acid/cellulose composites, determine the optimum pH, contact time, and initial concentration and study MO desorption. The adsorbent production begins with the isolation of cellulose from empty palm oil bunches (EFB) obtained from North Sumatra and the isolation of humic acid from peat soil obtained from Rawa Pening. Then humic acid was cross-linked to cellulose in an alkaline solution (NaOH), then epichlorohydrin was added as a cross-linking agent while heating at 600C for 2 hours. Epichlorohydrin cross-linked humic acid/cellulose adsorbents (AH/Cell-ECH) were further characterized using FTIR, XRD and SEM spectroscopy. MO solutions before and after adsorption were analyzed using UV-Vis spectrophotometry. MO desorption studies used HCl pH 4, 0.1 and 1.0 M NaCl and 40% and 60% ethanol. FTIR characterization showed that the AH/Sel-ECH adsorbents had active groups, including –OH, -C=O, and –COOH. Characterization using XRD showed diffraction peaks in the 2θ region around 11.41, 20.25, 22.55, and 42.66o, indicating the presence of galactose, xylose, glucose and polysaccharide phases. The SEM-EDX results showed that the surface of the adsorbent had non-uniform pore sizes, and the surface morphology tended to be clean and free of debris. It indicated the presence of C, O, and N elements in AH/ECH-cells and S, N elements after MO adsorption. The optimum interaction of AH/Sel-ECH with MO occurred at pH 2 with 150 mg/L MO, and a contact time of 120 minutes was obtained. MO adsorption by AH/ECH-cells followed a pseudo-second-order kinetics model and the Freundlich isotherm with an MO adsorption capacity of 9.84 x 10-5 mmol/g, respectively. Desorption studies showed that 60% ethanol was the most effective solution for desorption of MO.

Adsorptive properties of Flamboyant seed pod activated carbon for the removal of anionic dye in wastewater

Flamboyant seed pods were used as a sustainable and cost-effective adsorbent for the removal of anionic dyes from wastewater. The activated carbon was obtained via Carbonization and subsequent chemical activation with Sodium Hydroxide at 600 o C for 60 minutes. The adsorbent was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Optimization of adsorption parameters, including dosage, contact time, and initial concentration were performed to determine the optimum adsorption performance of the activated carbon. It is evident from the result that, there were good enhancements in pores of the absorbent FS-AC due to alkali impregnation in addition the several functional groups that took part in the adsorption process. The adsorption capacity of methyl orange increased with contact time until it reaches the saturation limit and later decrease, indicating that the adsorbent can no longer adsorbed more dye beyond it saturation limit. There was a decrease in the dye uptake with increase in dosage of the FS-AC. The amount of methyl orange adsorbed onto FS-AC increased with time and subsequently decreased at some point in time with maximum uptake at 100 mg/L.

Regenerated cellulose/polyethyleneimine composite aerogel for efficient and selective adsorption of anionic dyes

With the requirement of sustainable development in modern society, it is urgent to develop the environmentally friendly adsorbents for selective filtration and separation of toxic dyes from hazardous wastewater. Herein, a stable, reusable, and highly compressible three-dimensional regenerated cellulose/polyethyleneimine composite aerogel (RC/PCA) was successfully prepared directly using cheap cotton pulp as raw material and N-methyl morpholine-N-oxide (NMMO) as the “green” solvent, in which the regenerated cellulose (RC) with hydroxyl groups converted from cotton can interact with polyethyleneimine (PEI) with amine groups. After further crosslinking of RC, PEI and glutaraldehyde (GA), the RC/PCA can be used to selectively absorb anionic dyes from the ternary mixed dye system, which maximal adsorption capacity for methyl orange (MO) can be up to 980.39 mg/g. Moreover, the obtained stable RC/PCA can be repeatedly used at least 50 times for the removal of MO (20 mg/L) with a high filtration efficiency of 99.8 %. The kinetics and isothermal adsorption data were described via the pseudo-second-order kinetic model and Langmuir model. Therefore, this research proposes a novel strategy for developing low-cost, highly efficient, regenerated cellulose-based adsorbents to extract organic dyes from wastewater for potential practical applications.

Magnetic Ni@C nanoadsorbents for methyl orange removal from water.

In this study, Ni@C nanoparticles were produced and used as an adsorbent for removing methyl orange (MO) from an aqueous solution. The sol-gel method was utilized for the preparation of the particles. The X-ray diffraction pattern and transmission electron microscopy (TEM) were utilized to determine the phase, morphology, and size. The electron micrograph indicated the coating of carbon over Ni having size between 43 and 94nm, and the Raman spectrum supported it. Among three, the maximum specific magnetization of the Ni@C nanocomposite was 55.78emu/g for the N7 sample. From the BET approach, specific surface areas of 2.29 × 105, 3.66 × 105, and 5.48 × 105 cm2/g as well as average pore size of 49.30, 37.25, and 35.27nm were observed for N5, N6, and N7, respectively. The Ni@C nanoparticles were magnetically separable and exhibited rapid adsorption of MO of different concentrations from their aqueous solutions. The N7 adsorbent displayed the highest MO adsorption capacity (~ 32mg·g-1) along with maintaining an adsorption capacity of 81% even after 5 cycles. Adsorption isotherm and kinetic analysis gave critical inputs toward the possible adsorption mechanism.