Efficient removal of cationic dyes from aqueous solutions using a modified poly(ethylene terephthalate) fibers adsorbent

ABSTRACT

A novel adsorbent was synthesized through functionalization of glycidyl methacrylate-g-poly(ethylene terephthalate) (GMA-g-PET) fibers with iminodiacetic acid (IDA) to give IDA-GMA-g-PET fibers. This adsorbent was then exploited for the removal of Malachite Green (MG) and Rhodamine B (RB) dyes. MG has shown faster adsorption kinetics and equilibrium was attained in 15 mins. and 90 mins. for MG and RB, respectively. IDA-GMA-g-PET fibers showed 100% removal efficiency for MG and RB dyes from the solutions having initial concentrations of 300 mg L^?1and 200 mg L^?1, respectively. Desorption conditions of dyes and reusability of the fibers were also investigated.     

Green synthesis of nickel nanoparticles using Ocimum sanctum and their application in dye and pollutant adsorption

Nickel nanoparticles as an eco-friendly adsorbent was biosynthesized using Ocimum sanctum leaf extract. The phys-iochemical properties of green synthesized nickel nanoparticles (NiGs) were characterized by UV–Vis spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). NiGs were used as adsorbent for the removal of dyes such as crystal violet (CV), eosin Y (EY), orange I (OR) and anionic pol utant nitrate (NO3?), sulfate (SO42?) from aqueous solution. Adsorption capacity of NiGs was examined in batch modes at different pH, contact time, NiG dosage, initial dye and pol utant concentration. The adsorption process was pH dependent and the adsorption capacity increased with increase in contact time and with that of NiG dosage, whereas the adsorption capacity decreased at higher con-centrations of dyes and pol utants. Maximum percentage removal of dyes and pol utants were observed at 40, 20, 30, 10 and 10 mg·L?1 initial concentration of CV, EY, OR, NO3?and SO42?respectively. The maximum adsorption capacities in Langmuir isotherm were found to be 0.454, 0.615, 0.273, 0.795 and 0.645 mg·g?1 at pH 8, 3, 3, 7 and 7 for CV, EY, OR, NO3?and SO42?respectively. The higher coefficients of correlation in Langmuir isotherm sug-gested monolayer adsorption. The mean energies (E), 2.23, 3.53, 2.50, 5.00 and 3.16 kJ·mol?1 for CV, EY, OR, NO3?and SO42?respectively, calculated from the Dubinin–Radushkevich isotherm showed physical adsorption of adsor-bate onto NiGs. Adsorption kinetics data was better fitted to pseudo-second-order kinetics with R2 N 0.870 for al dyes and pol utants. NiGs were found to be an effective adsorbent for the removal of dyes and pol utants from aque-ous solution and can be applied to treat textile and tannery effluents.     

Magnetic nanocomposite of multi-walled carbon nanotube as effective adsorbent for methyl violet removal from aqueous solutions: Response surface modeling and kinetic study

Magnetic nanocomposite of multi-walled carbon nanotube (m-MWCNT) was synthesized for adsorptive removal of methyl violet (MV) from aqueous solutions. The experiments were conducted using a central composite design (CCD) with the variables of adsorbent dosage (0.4-1.2 g/L), solution pH (3-9), contact time (10-42 min) and ionic strength (0.02-0.1mol L^?1). Regression analysis showed good fit of the experimental data to a quadratic response surface model whose statistical significance was verified by analysis of variance. By applying the desirability functions, optimum conditions of the process were predicted as adsorbent dosage of 0.99g/L, pH=4.92, contact time of 40.98 minutes and ionic strength of 0.04 mol L^?1 to achieve MV removal percentage of 101.19. Experimental removal efficiency of 99.51% indicated that CCD along with the desirability functions can be effectively applied for optimizing MV removal by m-MWCNT. Based on the study, the adsorption process followed Langmuir isotherm model and pseudo-second-order kinetic model could realistically describe the dye adsorption onto m-MWCNT.     

Removal of methylene blue from aqueous solution by adsorption onto zeolite synthesized from coal fly ash and its thermal regeneration

BACKGROUND: The removal of cationic dyes from wastewater is of great importance. Three zeolites synthesized from coal fly ashes (ZFAs) were investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. Experiments were conducted using the batch adsorption technique under different conditions of initial dye concentration, adsorbent dose, solution pH, and salt concentration. RESULTS: The adsorption isotherm data of MB on ZFAs were fitted well to the Langmuir model. The maximum adsorption capacities of MB by the three ZFAs, calculated using the Langmuir equation, ranged from 23.70 to 50.51 mg g^?1. The adsorption of MB by ZFA was essentially due to electrostatic forces. The measurement of zeta potential indicated that ZFA had a lower surface charge at alkaline pH, resulting in enhanced removal of MB with increasing pH. MB was highly competitive compared with Na⁺, leading to only a < 6% reduction in adsorption in the presence of NaCl up to 1.0 mol L^?1. Regeneration of used ZFA was achieved by thermal treatment. In this study, 90–105% adsorption capacity of fresh ZFA was recovered by heating at 450 °C for 2 h. CONCLUSION: The experimental results suggest that ZFA could be employed as an adsorbent in the removal of cationic dyes from wastewater, and the adsorptive ability of used ZFA can be recovered by thermal treatment. Copyright © 2010 Society of Chemical Industry     

Facile preparation of agaraldehyde chitosan-based composite beads as effectual adsorbent especially towards amido black

Agaraldehyde and chitosan (CHI) functional beads as dye adsorbent were prepared under aqueous medium under ambient temperature and used for removing seven dyes from aqueous solutions. The resulting porous CHI-A_ald (R-A_ald-CHI) bio-beads were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscope. The dye removal efficiency was studied using seven dyes (amido black [AB], bromophenol blue, crystal violet, bismarck brown, cotton blue, methyl orange, methylene blue), but detail study was done on AB. AB adsorption was followed the Langmuir-isotherm and pseudo-second order kinetics. The effects of adsorption parameters were investigated, and maximum AB 1506 mg/g was adsorbed under the optimum conditions. The linear and nonlinear forms of Langmuir and Freundlich isotherms and two kinetic models pseudo-first-order and pseudo-second-order were studied. The results show that adsorption follow both isotherm model while for kinetics of adsorption follow pseudo-second-order. The results of this work showed that R-A_ald-CHI was encouraging adsorbent to remove dyes from wastewater, especially AB.     

Simultaneous multidye biosorption by chemically modified Sargassum glaucescens: Doehlert optimization and kinetic,equilibrium, and thermodynamic study in ternary system

Multidye biosorption of Sunset yellow (SY), Eosin yellow (EY) and Indigo carmine (IC) dyes onto chemically modified biomass of brown alga Sargassum glaucescens was studied. Principal component-wavelet neural network (PC-WNN) was applied for the simultaneous determination of anionic dye concentrations in ternary solutions. Experimental parameters were optimized using response surface methodology (RSM) with a Doehlert design. The optimal biosorption conditions were identified as biosorbent dosage 0.2 g L^?1, pH 3, and time 25 min. The maximum total biosorption capacity was 0.102 mmol g^?1. The Hill isotherm was the most suitable adsorption models in single and ternary systems. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) analysis confirmed possible interactions between biosorbent surface and dye molecules.     

Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g⁻¹ of AG at pH 4 and 81.3 mg g⁻¹ of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.     

One-step hydrothermal synthesis of a green NiCo-LDHs-rGO composite for the treatment of lead ion in aqueous solutions

Herein, we have synthesized a microspherical nickel-cobalt-layered double hydroxides-reduced graphene oxide composite (NiCo-LDHs-rGO) through a one-step hydrothermal method and then used it as an adsorbent for the removal of Pb²⁺ from aqueous solutions. Fourier transform infrared spectrophotometry (FT-IR), field emission scanning electron microscopy (FESEM), mapping elemental analysis, electron dispersive x-ray spectroscopy (EDX), x-ray diffraction analysis (XRD), and the Brunauer–Emmett–Teller (BET) method were used for the characterization of the adsorbent. Factors affecting the adsorption of Pb²⁺ ion such as solution pH, adsorbent dosage, contact time, competing ion, and regeneration were investigated in batch mode by the NiCo-LDHs-rGO. Under optimized conditions based on the Taguchi method (pH = 5.0, adsorbent dosage = 20 mg, and contact time = 30 min), the highest removal percentage was found to be 99.7% for 100 mg L⁻¹ of Pb²⁺. According to the results, NiCo-LDHs-rGO exhibited a high preference for Pb²⁺ over Cu²⁺, Zn²⁺, and Cd²⁺. This adsorbent was regenerated for several cycles (using 0.01 M HCl) with no significant deterioration in performance. Analyses of the adsorption isotherm models revealed that the adsorption of Pb²⁺ follows Freundlich isotherm with a maximum adsorption capacity of 200 mg g⁻¹. Also, the kinetic data confirmed that pseudo second order kinetic equation is the best model for predicting the kinetics. Furthermore, the Simulink modelling illustrated that the adsorption kinetics of Pb²⁺ onto NiCo-LDHs-rGO is done with high accuracy in a continuous stirred-tank reactor. Finally, dual interactions of the effective parameters can be modelled by polynomial equations in MATLAB, and according to the Taguchi model, pH is clearly the most important feature among all effective parameters.     

Poly(PEI-catechol-tetraethylenepentamine) was prepared by “one-pot method” for removing Reactive Red 195

Wastewater containing dyes is frequently discharged by industrial processes and needs separation and recycling. To solve this problem, it is important to research and develop environmentally friendly, efficient adsorbent materials for pollutant separation and recovery. In this study, a poly(PEI-catechol-tetraethylenepentamine) (PPCT) adsorbent was synthesized using a simple catecholamine reaction. This adsorbent exhibited high adsorption capacity and excellent removal efficiency for Reactive Red 195 (RR-195) in wastewater. The material was characterized using SEM, FT-IR, TGA, EA, and XPS. Its performance was optimized by varying the type of polyethyleneimine and the amount added during the preparation process. The effects of temperature, pH, contact time, and salt concentration on the adsorption were systematically investigated. Additionally, the experimental data showed consistency with both the Langmuir and pseudo-second-order kinetic models, simultaneously. The maximum adsorption capacity can reach 1754 mg g⁻¹ at 303 K, with a retention rate of 86.6% after two cycles. The removal rate exceeds 98% at a concentration of 400 mg g⁻¹ or lower. Additionally, the protonated amine group in PPCT carries a positive charge under acidic conditions, enabling selective adsorption of the anionic dye RR-195. Consequently, PPCT exhibits an excellent adsorption effect on RR-195 and holds promising applications in pollutant removal.     

Utilization of waste plastic pet bottles to prepare copper-1,4-benzenedicarboxylate metal-organic framework for methylene blue removal

ABSTRACT

The study aims to use waste plastic PET bottles to recover terephthalic acid for preparing copper-1,4-benzenedicarboxylate, which was then utilized as an adsorbent for removal of methylene blue (MB) from aqueous solutions after carefully characterizing by XRD, FTIR, TGA, SEM, and EDX. The optimum conditions were established as pH = 6, 25°C, adsorbent dose of 1 g L^?1, contact time of 20 min, and agitation speed of 150 rpm. The adsorption process was spontaneous, exothermic, fitting well to Langmuir isotherm model with the maximum adsorption capacity of 41.01 mg g^?1 and more suitable to be described by the pseudo first-order kinetic model. It was indicated that the physical adsorption plays a leading role in the adsorption process. The recycling study was also conducted to confirm the long-term use of the synthesized adsorbent.     

Preparation of a New Adsorbent Based on Wood Pulp for the Removal of Direct Blue 2 from Aqueous Solutions

Wood pulp was used as starting material for preparation of a new adsorbent for removal of Direct Blue (DB 2) from aqueous solutions. The adsorbent material was prepared by the reaction of wood pulp (WP) with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (DMF). The so obtained adsorbent was called with wood pulp adsorbent (WPA). The adsorption of DB 2 onto WPA was investigated. The adsorption data show that the maximum adsorption capacity, Q_max, of DB 2 onto WPA is 102.04 mg/g. The adsorption data also show that the adsorption of DB 2 onto WPA obeys Langmuir and Freundlich isotherms.     

碱性钙基膨润土对亚甲基蓝和刚果红的吸附去除

该文研究了碱性钙基膨润土(ACB)对水体中的亚甲基蓝(MB)和刚果红(CR)染料的吸附性能,考察了吸附剂用量、吸附时间及温度、pH及盐等因素对吸附效果的影响,同时进行了两种染料在碱性钙基膨润土上的吸附等温模型、吸附动力学模型研究。结果表明,ACB对MB、CR的脱色率随着吸附剂用量的增加而增加,在实验条件下,50 mg/L MB和100 mg/L CR的最佳吸附剂质量浓度分别为1.0 g/L和2.0 g/L;升高温度可以加快吸附速率,但对最终的脱色率影响很小;50 mg/L MB的吸附平衡时间在60 min左右,100 mg/L CR的吸附平衡时间在120 min左右;在pH=3～12时,ACB对MB的脱色率都稳定在99%左右,而适宜ACB吸附CR的pH=3～7,对CR的脱色率保持在90%左右;NaCl的加入对MB的吸附效果影响很小,对CR的吸附则有很强的抑制作用;ACB对MB的吸附同时符合Langmuir和Freundlich模型,而ACB对CR的吸附则更符合Langmuir模型;ACB对两种染料的吸附过程均符合准二级动力学模型,颗粒内扩散模型的拟合结果说明吸附过程存在颗粒内扩散作用。     

Self-assembly of thiourea intercalated graphene oxide based dual IIP for the SPE coupled FAAS method development of Cu(II) and Pb(II) determination

A new dual-template surface imprinted polymer for Cu(II) and Pb(II) was synthesized in one pot. Magnetic graphene oxide was self-assembled with low cost and environmentally benign thiourea. Presence of sulfur and nitrogen donor atoms provide hooks for coordination and partial reduction of graphene oxide matrix. It was used as an solid-phase extraction adsorbent for extraction, preconcentration, and coupled with flame atomic absorption spectrometry to manifest performance comparable with inductively coupled plasma atomic emission spectrometry (ICPAES) both in terms of quantification limit as well as interference. The critical experimental parameters such as pH; 4.6, contact time of 15 min and initial concentration of 777 (Q_e; 227 mg g⁻¹) and 800 μg L⁻¹ (Q_e; 273 mg g⁻¹) for Cu(II) and Pb(II), respectively, were optimized using RSM-CCD and artificial neural network. The adsorption process was kinetically faster (50% adsorption in 5 min), following fractal-like-pseudo-second-order (FLPSO) kinetics and Brouers–Sotolongo isotherm model owing to the heterogenous energy landscape. The imprinting factors were in the range of 4–7 in the presence of all coexisting ions. The proposed method was robust in the determination and removal of Cu(II) and Pb(II) from food, ground water, and industry effluents with low limit of detection (Cu(II); 1.03 μg L⁻¹ & Pb(II); 1.79 μgL⁻¹). Spiking and recovery tests were used to assess the method's accuracy. Cu(II)/Pb(II) loaded dual template IIP (DIIP) was utilized to remove anionic dyes with >95% efficiency. Thorough examination of the method and material selectivity (in binary, ternary, and multielement system), multi fold applications of determination, removal of Cu(II), Pb(II), and removal of anionic dyes makes DIIP a promising candidate for environmental remediation.     

Removal of methylene blue and safranin orange pollutants from liquid effluents by soy residue

Methylene blue and safranin orange dyes, which are used in the textile and pharmaceutical industries, can severely damage the environment and human health. This study investigated the use of okara residue as an alternative biosorbent for the removal of methylene blue and safranin orange dyes. Substantial amounts of okara residue are generated daily during the processing of soy milk in the agro-industrial sector. Dye adsorption was not affected by pH. An adsorption study identified the optimal experimental conditions as: 298 K, 0.03 g of adsorbent in 30 mL of dye solution at a concentration of 50 mg L⁻¹, and a contact time of 300 min for methylene blue dye, and 298 K, 0.02 g of adsorbent in 30 mL of dye solution at a concentration of 50 mg L⁻¹, and a contact time of 200 min for safranin orange dye; the maximum adsorption capacities were 93.201 ± 0.01 and 184 592 ± 0.02 mg g⁻¹, respectively. Okara has considerable advantages over other natural materials as an alternative for the treatment of industrial effluents. Because it is easily obtained and does not require any physicochemical treatment, adsorption does not require any specific operation temperature. In addition, okara exhibited a high adsorption capacity compared to other natural materials that require chemical and physical processing for adsorbent preparation.     

Imidazole modified acrylate-containing photocured hydrogels for the efficient removal of malachite green dye from aqueous solutions

In this work, we aimed to prepare a simple and an efficient adsorbent for the removal of toxic, cationic dye; malachite green (MG). We reviewed many previous studies and designed our adsorbent based on the rationale that (1) acidic groups containing monomers which are capable of making hydrogen bonds (or electrostatic interactions) with MG are very effective in adsorption and (2) π-π stacking enhances the adsorption capacity. We first synthesized an imidazole-acrylate adduct and used it for the preparation of photocured hydrogels. The imidazole-acrylate adduct was characterized by H NMR and FTIR spectroscopy. The effect of experimental conditions on the MG adsorption properties of the hydrogels such as the effect of pH, time and MG concentration were also investigated. Under the optimum conditions (pH = 6 and 220 min contact time) at room temperature, the maximum adsorption capacity was found as high as 714.28 mg/g. The results showed that the adsorption process of the optimum hydrogel, which can be used 4 times without a significant loss in its adsorption capacity, fits the Langmuir isotherm model. The hydrogel adsorbent displayed good selectivity and reusability.     

Low cost adsorbents obtained from ash for copper removal

We investigated the utilization of ash and modified ash as a low-cost adsorbent to remove copper ions from aqueous solutions such as wastewater. Batch experiments were conducted to determine the factors affecting adsorption of copper. The influence of pH, adsorbent dose, initial Cu²⁺ concentration, type of adsorbent and contact time on the adsorption capacity of Cu²⁺ from aqueous solution by the batch adsorption technique using ash and modified ash as a low-cost adsorbent were investigated. The optimum pH required for maximum adsorption was found to be 5. The results from the sorption process showed that the maximum adsorption rate was obtained at 300 mg/L when a different dosage of fly ash was added into the solution, and it can be concluded that decreasing the initial concentration of copper ion is beneficial to the adsorption capacity of the adsorbent. With the increase of pH value, the removal rate increased. When the pH was 5, the removal rate reached the maximum of over 99%. When initial copper content was 300 mg/L and the pH value was 5, the adsorption capacity of the zeolite Z 4 sample reached 27.904 mg/g. The main removal mechanisms were assumed to be the adsorption at the surface of the fly ash together with the precipitation from the solution. The adsorption equilibrium was achieved at pH 5 between 1 and 4 hours in function of type of adsorbent. A dose of 1: 25 g/mL of adsorbent was sufficient for the optimum removal of copper ions. For all synthesized adsorbents the predominant mechanism can be described by pseudo-second order kinetics.     

Gemini Surfactant Modified Montmorillonite as Highly Efficient Adsorbent for Anionic Dyes

The adsorption potential of a cheap, eco-friendly, and highly efficient adsorbent was studied as an alternative substitution of activated carbon for removal of organic anionic dyes from wastewater. The adsorbent (BDHP-Mt) prepared from the reaction of 1,3-bis(dodecyldimethylammonio)-2-hydroxypropane dichloride (BDHP) and Na-montmorillonite (Na-Mt) was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetry-derivative thermogravimetry (TG-DTG). Batch adsorption experiments were performed to remove anionic dyes such as Methyl orange (MO) and Congo red (CR) from aqueous solutions, using BDHP-Mt. The effects of pH and contact time under different temperatures on the adsorption capacities of MO and CR onto BDHP-Mt have been investigated. The results showed that the adsorption kinetics of MO and CR onto BDHP-Mt were in good agreement with pseudo-second-order model and the adsorption patterns of MO and CR could be well described by Langmuir isotherm. The comparative adsorption experiments indicated that BDHP-Mt exhibited much higher adsorption capacities (MO 239.11 mg g^?1, CR 192.57 mg g^?1) than active carbon (MO 203.88 mg g^?1, CR 45.26 mg g^?1), which may be due to the electrostatic interaction, partition adsorption and the bigger average pore diameter of BDHP-Mt. Thermodynamic experiments revealed that the two adsorption processes were spontaneous and endothermic. All the results implied that BDHP-Mt could be used as an alternative adsorbent of active carbon or other common adsorption materials for the adsorption of anionic dyes from effluents.     

Preparation and application of glycidyl methacrylate and methacrylic acid monomer mixture‐grafted poly(ethylene terephthalate) fibers for removal of methylene blue from aqueous solution

A novel fibrous adsorbent that grafts glycidyl methacrylate (GMA) and methacrylic acid (MAA) monomer mixture onto poly(ethylene terephthalate) (PET) fibers was used for removal of methylene blue (MB) in aqueous solutions by a batch equilibration technique. The operation parameters investigated included, pH of solution, removal time, graft yield, dye concentration, and reaction temperature. The adsorption rate of MB is much higher on the MAA/GMA‐grafted PET fibers than on the ungrafted PET fibers. MB was removed 99% the initial dye concentration at 10 mg L⁻¹ and 93% at 200 mg L⁻¹ by monomers mixture‐grafted PET fibers. Pseudofirst order and pseudosecond order kinetic equations were used to examine the experimental data of different graft yield. It was found that the pseudosecond order kinetic equation described the data of dye adsorption on fibrous adsorbent very well. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm models. The data was that Freundlich isotherm model fits the data very well for the dyes on the fibers adsorbent. The dye adsorbed was easily desorbed by treating with acetic acid/methanol mixture (50% V/V) at room temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adsorptive removal of fluoride from water by activated carbon derived from CaCl2-modified Crocus sativus leaves: Equilibrium adsorption isotherms,optimization, and influence of anions

A central composite design using response surface methodology was applied for the experimental design and optimization of fluoride adsorption on an activated carbon derived from calcium chloride-modified Crocus sativus leaves (AC-CMCSL). Fluoride removal efficiency as function of independent variables, such as initial fluoride concentration, pH, adsorbent dose, and time has been investigated. The maximum percentage removal of fluoride at optimum conditions (initial fluoride concentration?=?6.5?mg?L^?1, pH?=?4.5, adsorbent dose?=?15?g?L^?1 and time?=?70?min) was 85.43%. By comparing adsorption isotherm, the Freundlich model provided the best correlation (R²?=?0.99) for the adsorption of fluoride on AC-CMCSL. The maximum adsorption capacity from the Langmuir model (q_max) was 2.01?mg?g^?1. The influence of the co-existing anions on fluoride adsorption was in the following order: PO₄^3??>?SO₄^2??>?Cl^??>?NO₃^?. The results of the present study showed that activated carbon derived from the leaves of calcium chloride-modified Crocus sativus has a good potential for fluoride removal from aqueous solution.     

Adsorption removal of Brilliant green and Safranin-O contaminants from water using a hydrogel based on carboxymethyl cellulose and sodium alginate crosslinked by epichlorohydrin

The current study investigates the adsorption properties of a chemically crosslinked hydrogel based on sodium alginate (NaALG) and carboxymethyl cellulose (CMC). The structural characteristics of the investigated hydrogel are described using information from Fourier Transform–infrared spectra, X-ray diffraction patterns and field emission scanning electron microscopy pictures. The NaALG/epichlorohydrin (ECH)/CMC hydrogel was synthesised under optimised conditions with respect to the swelling percentage. Various reaction parameters were varied to obtain the maximum swelling percentage. The synthesised hydrogel was taken as an adsorbent in the decolorisation of Brilliant green (BG) and Safranin-O (SO) dyes from water. According to the kinetic investigations, the decolorisation equilibrium of SO by NaALG/ECH/CMC was discovered in 4 hours (98.98%), while the removal of BG by NaALG/ECH/CMC took 6 hours (97.7%). Chemical processes were used to describe the decolorisation mechanisms, which significantly supported the pseudo-first-order model. NaALG/ECH/CMC hydrogel absorption was indicated to take place in monolayer adsorption form (Langmuir isotherm). The highest adsorption capacity for BG was discovered to be 864.8 mg g⁻¹ and for SO it was 193.1 mg g⁻¹, by synthesised hydrogel, where “mg” refers to the commercial colourant and not to the pure dye. Therefore, the synthesised hydrogel can be considered as a smart device for the adsorption of dye in water purification tasks.