Adsorbent For Removal Of Dyes Research Articles

Defects-rich MgFe LDH: A high-capacity adsorbent for methyl orange wastewater

Dye pollution is a common pollutant in wastewater that poses a serious threat to human health. Layered double hydroxide (LDH) is a commonly used adsorbent for dye removal. However, its adsorption efficiency is significantly limited by the limited adsorption active sites of the adsorbent. In this paper, a defects-rich MgFe LDH adsorbent for anionic dye wastewater was synthesized by a simple hydrothermal method and alkaline etching. Different analytical techniques, such as XRD, FT-IR, SEM, TEM, XPS, and N2 adsorption-desorption isotherm, were used to verify the chemical composition and surface characteristics of the materials, and the effects of pH, temperature, and contact time on the adsorption effect of methyl orange and the adsorption mechanism were analyzed. Alkaline etching of Al and Zn in the laminate generated defects that expose unsaturated coordination centers and create abundant adsorption sites, which can electrostatically attract and coordinate with dye ions. At 25°C, the adsorption capacity of MgFe LDH with Al etched and MgFe LDH with Zn etched for methyl orange dye reached 1722 mg/g and 1685 mg/g, respectively, much higher than that of MgFe LDH (544 mg/g). This work provides a promising method for the removal of dye wastewater by adsorption and a new idea for the design and development of high-performance dye wastewater adsorbents.

Preparation of metal organic framework by strategy of ligand premodification coupling with dual ligands and adsorption behaviors for organic dyes

The method of ligand premodification coupling with dual ligands to introduce several functional groups can regulate the pore structure of the porous materials to meet different demands and to maintain the integrity of the framework. Amino groups was introduced into organic ligand by reacting with polyethyleneimine and then it was applied as one of the ligands to prepare porous materials. A series of porous materials were synthesized through varying the additional amount of modified ligand and characterized by several techniques such as BET, FTIR, XRD, XPS, SEM and EDS. The prepared materials were then used to remove organic dyes methyl orange (MO), methylene blue (MB) and Congo red (CR) from aqueous solution. The porous materials exhibited larger adsorption capacities and fast adsorption rate for MO and MB as certain modified ligand introduced. Due to steric hindrance of introduced amino chain, the adsorption capacities for CR decreased. The results of adsorption kinetics and adsorption isotherm studies showed that the adsorption process was more in line with pseudo-second kinetic model and Langmuir isotherm. The adsorption selectivity of the material for MB compared to MO could be controlled by altering the amount of modified ligand The prepared porous materials can be used as fascinating adsorbents for removal of dyes from aqueous solution in a wide pH range, and it was attractive and useful from practical viewpoint.

Cellulose-Based Waste in a Close Loop as an Adsorbent for Removing Dyes from Textile Industry Wastewater

In an attempt to reuse fibrous textile waste and, at the same time, to address dye pollution in textile wastewater, waste cotton-based yarn was utilized as a cheap and sustainable adsorbent, as well as a row material for carbon adsorbent production. Unmodified yarn and cotton-based carbon adsorbents were used as adsorbents for dye removal from water. Cotton and cotton/polyester yarn samples underwent thermal modification through carbonization followed by chemical activation with KOH. Various techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, and surface charge determination, were employed to analyze the morphological and surface characteristics of the cotton-based adsorbents. Adsorption properties were evaluated by testing the removal of selected cationic and anionic dyes from water. The impact of temperature, initial pH and concentration of the dye solution, and contact time on adsorption were investigated, and experimentally obtained data were analyzed using theoretical models. While carbonization alone did not significantly enhance adsorption properties, activated samples exhibited high efficacy in removing both cationic and anionic dyes from water. Despite the negative influence of the polyester component in the carbon precursor on the efficiency of activated samples in removing methyl orange, the results indicated that activated cotton and cotton/polyester yarn could be used to prepare highly efficient adsorbents for the rapid removal of methylene blue from real wastewater samples.

Chitosan‐nTiO2 Nanocomposite Synthesis and its Adsorptive Removal Capacity for Methylene Blue from its Aqueous Solution: Batch Adsorption Study and Modeling

AbstractThe current work used chitosan (CS)‐nTiO2 nanocomposites (CTNCs) prepared with different CS:nTiO2 mass ratios toward the MB dye removal from an aqueous medium in batch method at variable experimental conditions. The stability and competence of the nanocomposites were checked through characterization by SEM, FTIR, XRD, TGA, and BET. The highest removal of MB was 78 % with the adsorbent CS without nTiO2 (CWT), 94.5 % with CS:nTiO2=1 : 1 weight ratio (CTNC1‐1) and 80 % with CS:nTiO2=2 : 1 weight ratio (CTNC2‐1) with 10 mgL−1of MB and 5 gL−1 adsorbent dosages. The experimental observations obeyed the pseudo‐2nd‐order model, and rate‐limiting steps were film diffusions for CWT, CTNC1‐1 and intraparticle diffusion for CTNC2‐1. Monolayer adsorption was established from the isotherm model. Langmuir adsorption capacities for MB were presented as CTNC1‐1 (qL=34.31)>CTNC2‐1 (qL=32.87)>CWT (qL=21.32). The sorption energy, as derived from Dubinin–Radushkevich isotherm model, showed physisorption for all three adsorbents. The scale‐up design is reported. The statistical (R2>0.98) and GA modeling (R2>0.98) successfully predicted the percentage elimination of MB. Thus, CS‐nTiO2 nanocomposites are prepared as novel and environment‐friendly adsorbents for dye removal.

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.

A comprehensive review on the sequestration of dyes from aqueous media using maize-/corn-based adsorbents

Abstract Corn or maize (Zea mays L.) is the most significant grain crop worldwide after wheat and rice. It is widely cultivated and consumed as food, feed, and industrial raw material, along with the emission of a large quantity of corn waste. Such abundant, renewable, and cheap wastes with unique chemical compositions can be efficiently converted into adsorbents for the elimination of dye-contaminated water. This article represents an extensive review of the use of corn/maize waste-derived adsorbents for the sequestration of dyes from aqueous media. This study addressed the utilization of corn residues, including cob, stalk, straw, husk, and silk, as precursors for adsorbents. The adsorption behaviour, mechanism, and regeneration of the studied corn adsorbent/dye systems were identified. It was observed that the most common forms of corn/maize-derived adsorbents that have been utilized for the sequestration of dyes include biosorbents, biochars, activated carbons, and composites. The highest adsorption capacity (1,682.7 mg/g) for dye (methylene blue) sequestration was obtained using a corn husk composite-based adsorbent. Important findings and future ideas are finally mentioned for the corn/maize-based materials and their application as adsorbents for dye removal.

Obtaining bio-oil and activated carbon from waste pomegranate peels by pyrolysis.

This study aims to produce beneficial products with pomegranate peel waste through pyrolysis. For this purpose, the usability of the liquid product as a biofuel and the solid product as an adsorbent for dye removal was investigated. To characterize the bio-oil and biochar produced under the best pyrolysis conditions, Fourier transforms infrared spectroscopy (FT-IR), Gas chromatography-mass spectrometry (GC-MS), calorific value, Brunauer-Emmett-Teller (BET), and Scanning electron microscopy (SEM) analyses were conducted. When we examine the FT-IR spectrum of the bio-oil, the presence of phenol, alcohol, ketone, and aldehyde groups is seen in the structure. The GC-MS analysis demonstrated that phenol content was 27.9%, aldehyde content was 19%, acid compound content was 18.28%, ketone content was 8.7%, and aromatic compound content was 8.4%. The lower calorific value of bio-oil was determined as 27.33MJ/kg. It was observed that activated carbon produced from biochar at a 3:1 KOH/biochar impregnation ratio and a carbonization temperature of 800°C exhibited the highest surface area (1307 m2/g). In adsorption analysis, it was observed that the adsorption efficiency was higher at pH 9 and 35°C and with 150ppm initial concentration. Langmuir and Freundlich adsorption isotherms were determined, and the high R2 (0.99) was consistent with the Langmuir methylene blue (MB) adsorption model.

The effectiveness of natural adsorbent for removal of dye using two isotherm models

The low-cost and more efficient adsorbents of Azadirachta Indica (Neem) are charcoal, bark; leave and root were investigated for its optimistic de-colorization of wastewater containing a dye. The effect of various parameters such as contact time, pH, temperature and adsorbent dosage has been carried out in this study. Two isotherm models were developed for compliance with Langmuir and Freundlich isotherm. The results of the goodness fit test based on Root Mean Square Error (RMSE), R2 for Langmuir and Freundlich models were given as, for pH (0.9745 – 0.99919), (0.4831 – 0.9999) for Adsorbent Dose is (0.9034 – 0.9221), (0.4689 – 0.9884) for contact time (0.9494 – 0.9513), (0.4677 – 0.9990) and temperature (0.9264 – 0.9349), (0.3755 – 0.5849) respectively. Both models were found to be best fit on decolorization of dye with contact time, pH, temperature and adsorbent dosage. pH 5 value indicated that adsorbent was effective in the removal of dye.

A novel mesoporous carbon nanospheres-based adsorbent material with desirable performances for dyes removal

Nowadays, the reduction of dye contaminants in the aquatic environment has attracted widespread research attention. In this work, a novel mesoporous carbon nanospheres (MCNs)-based material as an adsorbent for dye removal was achieved by the carbonization of a composite of sucrose and aluminum sulfate without involving any hazardous activators. The as-obtained MCNs were analyzed by TG, XRD, FESEM, TEM, Raman, BET and XPS, meanwhile the batch experiments of Congo red (CR), Malachite green (MG) and Methylene blue (MB) on the MCNs were conducted to explore the impact of adsorption conditions on the adsorption process, respectively. Results show that the MCNs exhibit a uniform spherical morphology as well as partially graphitic structure with a large surface area of 449.25 m2/g, a relatively narrow pore size distribution and a high pore volume of 0.57 cm3 g−1. The unique porous structure of the MCNs endows it with high adsorption capabilities for dyes, including CR (1726.60 mg g−1), MG (980.55 mg g−1) and MB (708.82 mg g−1), suggesting its high adsorption capability for both anionic and cationic dyes. Meanwhile, the adsorption process is demonstrated to follow the Langmuir model and pseudo-second-order kinetic model, respectively, and the main adsorption mechanisms may involve pore filling, π-π conjugation, electrostatic attraction and hydrogen bonding. Furthermore, the as-synthesized adsorbent displays good recyclability performance for remaining relatively high sorption performance even after five regeneration cycles.

Boosted capture ability of Rhodamine B by a core-shell composite equipped with spherical porous carbon and copper-based metal-organic framework

Copper-based metal-organic framework (e.g. Cu-BTC) suffer from water instability issue, restricting its practical applications in the adsorptive removal of dyes from aqueous solution. In this exploration, a innovative core-shell porous composite with spherical porous carbon (SPC) and Cu-BTC units, boosting its water stability and Rhodamine B (RhB) uptake capacity. Those novel Cu-BTC@SPC composites have undergone comprehensive characterization, and their structural features have been further evaluated through various analytical techniques, including N2 adsorption-desorption tests, X-ray diffraction analysis, scanning electron microscopy image, Fourier transform infrared spectroscopy analysis, X-ray photoelectron spectroscopy, etc. Remarkably, the structural integrity of the Cu-BTC@SPC composite remained intact even after being immersed in water for a duration of 7 days or subjected to boiling water for 6 h. Through a series of batch tests, we observed that the Cu-BTC@SPC composite exhibited a high capacity for RhB adsorption. The observed phenomenon can be ascribed to the synergistic effects of π-complexation and acid-base interactions present within the SPC and Cu-BTC components. The maximum RhB uptakes over Cu-BTC@SPC can reach 81 mg/g, exceeding some other adsorbents prior publications. Especially, the RhB uptakes capacity of Cu-BTC@SPC decreased by less than 10% after the fifth cycle. The distinctive core-shell structure of Cu-BTC@SPC might be a hopeful adsorbent for dye (e.g. RhB) removal from water.

KMnO4-oxidized whole pine needle based adsorbent for selective and efficient removal of cationic dyes

In the present study, we report the chemical modification of the dried and fallen pine needles (PNs) via a simple protocol using KMnO4 oxidation. The oxidized PNs (OPNs) were evaluated as adsorbents using some cationic and anionic dyes. The successful synthesis of OPNs adsorbent was characterized by various techniques to ascertain its structural attributes. The adsorbent showed selectivity for the cationic dyes with 96.11% removal (P r) for malachite green (MG) and 89.68% P r for methylene blue (MB) in 120 min. Kinetic models namely, pseudo-first order, pseudo-second order, and Elovich were applied to have insight into adsorption. Additionally, three adsorption isotherms, i.e., Langmuir, Freundlich, and Temkin were also applied. The dye adsorption followed a pseudo-second-order kinetic model with R 2 > 0.99912 for MG and R 2 > 0.9998 for MB. The adsorbent followed the Langmuir model with a maximum adsorption capacity (q m) of 223.2 mg/g and 156.9 mg/g for MG and MB, respectively. Furthermore, the OPNs showed remarkable regeneration and recyclability up to nine adsorption-desorption cycles with appreciable adsorption for both the dyes. The use of OPNs as an adsorbent for the removal of dyes from wastewater, therefore, provides an ecologically benign, low-cost, and sustainable solution.

Adsorptive Removal of Dye (Methylene Blue) Organic Pollutant from Water by Pine Tree Leaf Biomass Adsorbent

In this laboratory batch adsorption study, the raw pine tree leaf biomass solid waste adsorbent material was used for the removal of methylene blue (MB) dye from water at different physicochemical process conditions. The characteristics of adsorbents were determined for particle size, surface area, the existence of functional group identification, and the morphology of the adsorbent surface. The adsorption was performed at different process conditions, which include solution pH, dye concentrations, adsorbent doses, and temperature, respectively. In this study, it was found that MB dye adsorption increased with increases in solution pH and adsorbate MB dye concentration but decreased with adsorbent doses and temperature at fixed process conditions. The Langmuir isotherm model was best fitted with the experimental equilibrium data, with a higher linear regression coefficient (R2) value of 99.9% among the two widely used Langmuir and Freundlich adsorption isotherm model equations. The maximum Langmuir monolayer adsorption capacity of raw pine leaf was found to be 36.88 mg/g, which was comparable with other reported adsorbent capacities towards methylene blue (MB) dye adsorption. The value of the separation factor, RL, from the Langmuir isotherm model equation gives an indication of favorable adsorption. Thermodynamic parameters such as standard Gibbs free energy change (ΔG0), standard enthalpy change (ΔH0), and standard entropy change (ΔS0) indicated that the methylene blue (MB) dye adsorption by pine tree leaf biomass was spontaneous and exothermic in nature and that the mechanism of adsorption was mainly physical adsorption. Finally, limitations and future studies are also discussed here. The outcome of this batch adsorption study may result in the valorization of locally available large pine tree leaf residue waste, which could be used in water purification.

Preparation and characterization of PSF porous composite nanofibers via solution-blowing as adsorbent for dye removal

Preparation and characterization of PSF porous composite nanofibers via solution-blowing as adsorbent for dye removal

Effective utilization of discarded reverse osmosis post-carbon for adsorption of dyes from wastewater

In this study, the deployment of post Reverse Osmosis (RO)-carbon as a adsorbent for dye removal from water has been investigated. The post RO-carbon was thermally activated (RO900), and the material thus obtained exhibited high surface area viz. 753 m2/g. In the batch system, the efficient Methylene Blue (MB) and Methyl Orange (MO) removal was obtained by using 0.08 g and 0.13 g/50 mL adsorbent dosage respectively. Moreover, 420 min was the optimized equilibration time for both the dyes. The maximum adsorption capacities of RO900 for MB and MO dyes were 223.29 and 158.14 mg/g, respectively. The comparatively higher MB adsorption was attributed to the electrostatic attraction between adsorbent and MB. The thermodynamic findings revealed the process as spontaneous, endothermic, and accompanied by entropy increment. Additionally, simulated effluent was treated, and >99% dye removal efficiency was achieved. To mimic an industrial perspective, MB adsorption onto RO900 was also carried out in continuous mode. The initial dye concentration and effluent flow rate were among the process parameters that were optimized using the continuous mode of operation. Further, the experimental data of continuous mode was fitted with Clark, Yan, and Yoon-Nelson models. Py-GC/MS investigation revealed that dye-loaded adsorbents could be pyrolyzed to produce valuable chemicals. The cost and low toxicity associated benefits of discarded RO-carbon over other adsorbents reveal the significance of the present study.

Exploring the reusability of cuttlefish bones in sustainable waste management by green synthesis method for methylene blue dye removal

ABSTRACT The use of solid wastes as an adsorbent for dye removal from wastewater is one of the leading steps of sustainable waste management. In this research, the removal of Methylene Blue dye by cuttlefish bone waste was examined by using peppermint extract. Zn-doped cuttlefish bone was prepared by the green synthesis method in laboratory conditions for the comparison of cuttlefish bone in adsorption and ultrasonically-assisted adsorption processes. The results of this study exhibited that Methylene Blue removal with Zn-doped cuttlefish bone was higher than that with cuttlefish bone at all pH values. The qmax values obtained from the Langmuir isotherm model were calculated as 8.96 mg/g and 12.74 mg/g in the adsorption process with cuttlefish bone and Zn-doped cuttlefish bone, respectively. The qmax value relatively improved to 18.05 mg/g in the ultrasonically-assisted adsorption with Zn-doped cuttlefish bone. With the green synthesis, the qmax increased by 1.42 times, while this increase was 2.01 times with the application of the ultrasonically-assisted adsorption process using Zn-doped cuttlefish bone compared to the adsorption process using cuttlefish bone.

Conversion of cassava rhizome into efficient carbonaceous adsorbents for removal of dye in water

The development of sustainable adsorbent materials for removing pollutants from water is of great interest for environmental remediation and human safety. This work presents the beneficial use of cassava rhizome (CR) to produce economical and efficient carbonaceous adsorbents for dye removal. CR derived activated carbons (AC) and magnetic AC were fabricated by one-pot hydrothermal carbonization in the presence of ZnCl2 and ZnCl2/FeCl3 respectively, followed by pyrolysis at 800 °C. Porosity tuning and degree of magnetization of as-prepared carbons were achieved by varying the amount of ZnCl2 and FeCl3 as an activating agent and source of magnetic particles respectively. The result indicated that the optimal condition to obtain ACs with a high SBET (1405 m2/g) and the largest mesopore volume (0.54 cm3/g) was using the weight ratio of ZnCl2 to CR of 3 (3AC). While, the magnetic mesoporous carbon with the highest SBET (554 m2/g) was yielded when addition of FeCl3 into the reaction mixture with a FeCl3 to ZnCl2 weight ratio of 1(3AC-1M). 3AC and 3AC-1M were tested as adsorbents to investigate the adsorption efficiency of methylene blue (MB) in water. The adsorption behavior of MB on 3AC and 3AC-1M were monolayer adsorption based on the Langmuir isotherm model with R2 of 0.9993 and 0.9953, respectively. 3AC showed the MB adsorption capacity of 274 mg/g which is comparable to that of commercial ACs. 3AC-1M that adsorbs MB with the maximum capacity of 102 mg/g, was separated from aqueous solution easily using an external magnet. This study demonstrates that the carbon precursors from biomass waste as CR can be conveniently converted into efficient carbonaceous adsorbents and functionalized for example by adding magnetic properties into the carbon structure to enable manipulations in industrial operations.

A new strategy to synthesis of porous polymers from plastic waste for highly efficient adsorption of rhodamine B, malachite green and I2 vapor

Plastic waste has been becoming a severe environmental issue. Developing low-cost and facile strategy to converse them into the high value-added materials for remediation of ecosystem is a big challenge. In this manuscript, Polystyrene foam waste (PSF) was employed as starting material to react with the different mass ratio of cyanuric chloride (CC) to synthesize a series of hyper-cross-linked polymers (HPPCs). HPPCs were porous polymers and mainly composed of micro-pores and meso-pores. Their apparent surface areas (SBET) and pore volumes were in range of 622.9 ± 11 and 719.2 ± 15 m2 g−1, 0.87 and 1.01 cm3 g−1, respectively. The SBET and pore volume could be tuned by the mass ratio of PSF and CC. Adsorption experiments revealed that HPPC-3 showed high adsorption quantities of rhodamine B (RhB) and malachite green (MG) with the maximum adsorption capacities of 2354.0 ± 60.8 and 1331.9 ± 30.6 mg g−1, respectively. The adsorption isotherm and kinetics data suggested that the adsorption behaviors of RhB and MG on HPPC-3 followed the Langmuir models and pseudo-second-order models. Additionally, HPPC-3 displayed high adsorption capacity of iodine vapor up to 188 ± 3.2 wt%. Therefore, this work suggested a new approach for converting plastic waste into the promising adsorbent for removal of dyes and radioactive iodine vapor from contaminated ecosystem.

Bioinspiration synthesis of hydroxyapatite nanoparticles using eggshells as a calcium source: Evaluation of Congo red dye adsorption potential

Hydroxyapatite nanoparticles (HAp NPs) were synthesized with Muntingia calabura leaf extract as solvent and eggshell waste as a calcium source. The synthesized nanoparticles were irregular rod-like, as visualized by FESEM, while EDX and XPS studies confirmed the formation of hydroxyapatite. The synthesized HAp NPs were polycrystalline and highly thermostable as per XRD and TGA studies respectively. FTIR confirmed the stable coating of plant phytochemicals onto the HAp NPs. Congo red adsorption using HAp NPs nanoadsorbent was optimized by central composite design, wherein 89.96% of 33.18 mg/L dye was adsorbed in 137 min at 180 RPM. The adsorption process was in line with pseudo-second-order model and the Freundlich isotherm indicated chemical adsorption. The adsorption process was feasible, exothermic, and spontaneous as indicated by the thermodynamic studies. The adsorption capacity of HAp NPs stood at a maximum of 217 mg/g, indicating its superiority among other adsorbents reported earlier. It is evident from the convincing results that the HAp NPs synthesized in the present investigation may have a major role in developing novel adsorbents for dye removal out of wastewater streams.

On the applicability of triazine-based covalent organic polymer as adsorbent for dye removal from aqueous solution

Triazine-based covalent organic polymer, TCOP, is synthesized via the reaction between cyanuric chloride and piperazine in 1,4-dioxane, and is characterized with FT-IR, EDX, elemental mapping, XRD, SEM, TEM and N2 adsorption/desorption techniques. The capability of TCOP in the removal of different types of dye pollutants is studied and it was found that the removal efficiency is more than 70% for all of them. The kinetics and equilibrium adsorption of Rhodamine B (RhB) was studied at different conditions. Most of the adsorption takes place in less than 20 min and the maximum adsorption capacity is 153 mg/g. The adsorption isotherm can be well described by the modified Langmuir-Freundlich equation and the adsorption kinetics follows the fractal-like pseudo-first order kinetics model. Both of the fitted models reveal the heterogeneity of adsorbent. The adsorption thermodynamics parameters were calculated and interpreted. Finally, it was shown that the prepared TCOP can be used for the removal of dye mixture from aqueous solution.

Thiacalix[4]arene-functionalized magnetic xanthan gum (TC4As-XG@Fe3O4) as a hydrogel adsorbent for removal of dye and pesticide from water medium

A novel thiacalixarene-functionalized biopolymer nanocomposite hydrogel was designed and prepared as an efficient adsorbent system to elimination of aquatic areas from chlorpyrifos (CPF) and crystal violet (CV). This adsorbent system was conducted by multi-step including; preparation of Fe3O4@XG hydrogel through in-situ magnetization of XG, amine modification of Fe3O4@XG hydrogel by using 3-aminopropyltriethoxysilane (APTES) to get Fe3O4@XG-NH2, the synthesis of TC4As supramolecule, its functionalization with epichlorohydrin (ECH) and eventually covalently attachment of ECH-modified TC4As onto as-prepared Fe3O4@XG-NH2 to obtain the TC4As-XG@Fe3O4 nanocomposite hydrogel. Several characterization techniques including FTIR, XRD, FESEM, VSM, TGA, and BET demonstrated the successful synthesis of TC4As-functionalized XG nanocomposite hydrogel. The result of characterization demonstrated that the TC4As-XG@Fe3O4 adsorbent system showed superparamagnetic property with magnetic saturation (Ms) of 9.10 emu/g and high thermal stability with 73 % char yields. The XRD pattern of TC4As-XG@Fe3O4 nanocomposite showed characteristic peaks of Fe3O4 MNPs and XG, but with enhanced crystallinity in compared to neat XG as result of in-situ magnetization of XG as well as its functionalization with TC4As. The BET surface area of Fe3O4@XG and TC4As-XG@Fe3O4 hydrogels was measured approximately 45.32 and 17.30 m2/g, which was higher than neat XG. Then, the constructed adsorbent system was assessed for removing a CPF as an organophosphorus pesticide and CV as cationic dye from aqueous. The batch adsorption experiments were conducted to optimize the effective adsorption parameter i.e., solution pH, adsorbent dosage, contact time, CPF and CV initial concentration. Furthermore, Freundlich isotherm mode was well-fitted model and by utilizing prepared adsorbent, and the maximum adsorption capacities of CPF and CV (at optimum conditions: 298 K, pH 7.0 and 9.0) were found to be about 769.230 and 833.33 mg/g, respectively. The adsorption kinetic study revealed that experimental data were well-fitted by the pseudo-second-order model. Based on proposed mechanism, the CPF and CV were adsorbed onto hydrogel nanocomposite mainly through π–π interactions, electrostatic interaction and hydrogen bonding. The regeneration experiments up to three cycles were best achieved for two studied pollutants.