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Fluoride contamination in groundwater is a major concern in many parts of India and all over the world. Researches paying attention for the removal of fluoride through the application of biosorbents prepared from different parts of plants are finding greater scope and importance. The present research work focuses on Senna auriculata L., flower petal biomass as biosorbent, and evaluated its feasibility for fluoride ion elimination from aqueous solutions. Batch experiments were conducted to remove fluoride under different experimental conditions have been optimized for the maximum removal of fluoride; 80% removal was observed at pH: 6, sorbent dosage: 0.25 g/100 mL, time of agitation: 90 min, and initial concentration of the fluoride ions: 5 mg/L. Characterization studies of the biosorbent revealed its favorability towards the sorption of fluoride. In the isothermal modeling studies, Langmuir isotherm model was obeyed by the biosorption process with R2 value of 0.98 and from a kinetic perspective, the biosorption of fluoride onto the biosorbent observed the pseudo-second-order reaction with R2 value of 0.98. The developed biosorbent has been applied to real field fluoride-contaminated water samples and found to be successful.

Recently heavy metal pollution is consider among the most essential environmental issues. Due to their impact, the removing of heavy metals from the environment is a high demanding concern. Heavy metals adsorption is a new technology for wastewater treatment that contain different selected heavy metals types. This study aim to adopted adsorbents with low cost application, in this technique a pine cones used as plant wastes adsorbents in Industrial wastewater treatment by implemented batch technique adsorbent dosage and adsorbate initial concentration). The plant waste sample of (pine cone) was used to test its efficiency which that provide the optimum performance in removing heavy metals and other pollutants (Turbidity, TSS and TDS). Activated carbon produced from Pine cones Turkish Pine (ACPC) was adopted as an adsorbent for the Zinc ions removal from wastewater with industrial pollutants. Surface analysis was preform to measure the pore size distribution and specific surface area of the activated carbon produced from pine cone. Optimal parameters, pH, equilibrium time, adsorbent dosage, temperature and mix speed were investigated. Using Langmuir, Freundlech and Elvich isotherm models, equilibrium data were evaluated. Langmuir isotherm model provided the highest fit to the equilibrium data.

Glycine functionalized activated carbon adsorption material (NOPAC-GLY-X) was successfully prepared by one-step thermal decomposition using agricultural waste navel orange peel as a precursor. Through batch adsorption experiments, it is found that the adsorption performance of Gd(III) on activated carbon can be significantly enhanced by glycine modification. The adsorption isotherms of the NOPACs conformed to the Langmuir isotherm model, and the maximum adsorption capacity of the activated carbon sample NOPAC-Gly-60 is approximately 48.5 mg/g. The Gd(III) adsorption capacity of navel orange peel activated carbon can be doubled after glycine modification, and the adsorption efficiency of gadolinium can reach 99% at pH=7. The physicochemical properties of the prepared adsorbents were characterized by BET, FTIR, EA, and XPS. The characterization test shows that the specific surface area of the sample increases from 1121 to 1523 m2/g, and the ratio of (N+O)/C increases from 10.8% to 30.0% by the glycine modification. After five cycles of adsorption-desorption, the adsorption capacity can still be maintained at 88% of the initial capacity. NOPAC-GLY-60 has excellent adsorption selectivity for Gd(III). With the obvious advantages of simple synthesis steps and low cost, the activated carbon modification method adopted in this study has great application value in the field of rare earth adsorption and recovery.

In the study, the layered double hydroxide (LDH) of NiZnFe and its composites with date-palm biochar (LDH-DPb) and carbon nanotubes (LDH-cnt) were synthesized for adsorbing reactive black 5 (RB5) dye from aqueous solutions. In the first 5 min, rapid adsorption was followed by a gradual increase in both dye uptake and removal efficiency of up to 60 min of starting time. In the investigated pH range (3.0–8.0), the removal efficiency linearly decreased while the sorption capacity linearly increased for all three adsorbents as their doses increased to 0.3 or 0.4 g following a decreasing trend up to 0.6 g. By increasing the initial RB5 concentration from 10 to 100 mg L−1, the removal efficiency linearly decreased. A nearly perfect fitting of the pseudo-second-order kinetic model to the adsorption data was observed; however, the Elovich kinetic model showed the heterogeneous surface of adsorbents with chemisorption. At the solid–liquid interface, from a thermodynamics point of view, we obtained the nonspontaneous nature of the adsorption of RB5 dye of the studied adsorbents with an increased disorder, which supported the endothermic nature onto the studied adsorption process. Furthermore, a nearly perfect fitting of the Langmuir model was obtained to the adsorption data, thereby suggesting the monolayer adsorption of RB5 dye onto the studied adsorbents. In the Dubinin–Radushkevich model, a good agreement of the calculated adsorption capacities to the experimental values were observed and the chemical adsorption of RB5 dye on to the studied adsorbents was proposed based on E (8 – 16 kJ mol−1).

Rare earth elements (REE) are strategic resources and the recycling of REE in alternative resources is urgent and gets increasingly attention. However, the separation of REE in these alternative resources is still a challenge due to the low concentration of REE and multi coexisted ions in acidic system. In this study, the species distribution of REE within the pH 0 to 8.0 was calculated. The SBA-15 originated from coal fly ash was modified by two steps with (3-Aminopropyl) triethoxysilane (APTES) and diethylenetriaminepentaacetic dianhydride (DTPADA) to obtain DTPADA-SBA-15 adsorbent, which was applied to the selective adsorption of REE. The results showed that DTPADA-SBA-15 possessed excellent adsorption performance on the selective adsorption of REE, including Eu, Gd, Tb, Nd and Sm, in acidic solution (pH 2) with multi competing ions. The FT-IR and Zeta potential characterization verified that the chemical adsorption through the coordination of O in DTPADA-SBA-15 with REE was dominant at lower pH value. The study of adsorption kinetics indicated that the adsorption of rare earth metal ions followed pseudo-second-order kinetic, of which the adsorption process followed the Langmuir isotherm model.

Magnetite nanoparticles@Fe-BTC composite material was synthesized by a solvothermal method, where magnetite nanoparticles were added during the synthesis and was characterized by different analytical techniques analytical such as XRD, Raman and FTIR spectroscopy, and nitrogen physisorption at 77 K. Magnetite nanoparticles into Fe-BTC composite material was used in the adsorption of metals ions such as copper (Cu(II)), mercury (Hg (II)), arsenic (As (III)), and lead (Pb (II)). The experimental data of the adsorption of Cu(II), As (III), and Pb (II) metals ions showed a better fit to Langmuir isotherm model, while for the Hg (II) ion adsorption was observed a better adjusts to Temkin isotherm model. The kinetic pseudo-second-order model is the one that better describes the experimental data in all metal ions. The composite material showed a maximum adsorption capacity of 55 mg/g, 57 mg/g, 147 mg/g, and 155 mg/g for Cu (II), As (III), Pb (II), and Hg (II), respectively which was considerable. The adsorption selective for composite material in the mixed metal solution followed the order of Cu (II)> Pb (II) > Hg (II) > As (III). Therefore, composite material could be a good alternative as adsorbent material for the remediation of contaminated water by heavy metals.

The utilization of coal fly ash derived from circulating fluidized bed combustion (CFBFA) still faces great challenges because of its unique characteristics. In this study, a zeolitic material with Na-P1 zeolite as the main phase was successfully synthesized via a hydrothermal method by using CFBFA as the raw material. The effects of hydrothermal temperature, time, and added CTAB amount on the characterizations of synthesized materials were investigated by XRD, SEM, and XPS. The properties of the optimal zeolitic material and its adsorption performance for Pb2+ in aqueous solution were evaluated. The influences of pH, initial concentration, dosage, and temperature on Pb2+ adsorption were also examined. Results revealed the following optimal parameters for the synthesis of zeolitic material: NaOH concentration of 2 mol·L-1, solid-to-liquid ratio of 1:10 g·ml-1, hydrothermal temperature of 110 °C, hydrothermal time of 9 h, and CTAB amount of 1 g (per 100 ml solution). The adsorption capacities of the zeolitic material reached 329.67, 424.69, and 542.22 mg·g-1 when the pH values of aqueous solution were 5, 6, and 7, respectively. The Pb2+removal efficiency can reach more than 99% in aqueous solution with the initial concentrations of 100–300 mg·L-1 under pH 6 and suitable adsorbent dosage. The adsorption and kinetics of Pb2+ on the zeolitic material can be described by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The ion exchange between Pb2+ and Na+ and chemisorption are the main adsorption mechanism. All these findings imply that the synthesis of low-cost adsorbent for Pb2+ removal from weak acid and neutral aqueous solution provides a highly effective method to utilize CFBFA.

Salidroside (8-O-β- d -glucoside of tyrosol), a plant-derived natural product, is used for treatment of hypoxia, fatigue and aging diseases. The availability of salidroside is restricted since it is extracted from 3-5 years old Rhodiola roots, which grow very slowly in the cold region of northern hemisphere of Earth. Our laboratory has constructed an engineered Escherichia coli and established a fermentation process to produce salidroside from glucose. In this article, nine macroporous resins from polarity to non-polarity, including NKA-9, S-8, AB-8, SP825, D101, LSA-8, LX-12, LX-18 and LX-68 resins, were tested to separate salidroside from fermentation broth. After static and dynamic experiments, the weakly polar SP825 resin had a better separation efficiency among nine resins. The adsorption kinetic and isotherm of salidroside on the SP825 resin were determined, and the pseudo-second-order kinetic model and Langmuir model could be fitted well. The effects of the pH on adsorption and ethanol concentration on desorption were investigated, and an optimal separation process was established. The adsorption for salidroside in the SP825 resin column was conducted with loading 150 ml at pH 7, and desorpted by washing 50 ml of 80% ethanol solution. Under the best process conditions, the purity and yield of salidroside in the final product were 91.6% and 74.0%, respectively. The results showed that the macroporous SP825 resin would be feasible and effective to prepare salidroside and has promising application in the downstream process of microbial fermentation. © 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd.. All rights reserved.

Adsorbents with simple preparation and high surface area have become increasingly prevalent for the removal of organic contaminants. Herein, a carbon nanoplate codoped by Co and N elements with abundant ordered mesoporous (Co/N-MCs) was applied as an adsorbent for tetracycline removal. Taking integrated advantages of ordered mesopores on carbon-based structures and N-doping inducing the strengthened π–π dispersion and generation of pyridinic N, as well as cobaltic nanoparticles embedded in carbon nanoplates, the Co/N-MCs was tailored for high efficiently absorbing tetracycline via π-π interaction, Lewis acid-base interaction, metal complexation and electrostatic attraction. The Co/N-MCs had the advantages of high surface area, porous structure, plenty adsorption sites, and easy separation. As such, the as-prepared Co/N-MCs adsorbents significantly enhanced tetracycline removal performance with a maximum adsorption capacity of 344.83 mg·g-1 at pH 6 and good reusability, which was finally applied to removal tetracycline from tap water sample. Furthermore, the adsorption process towards tetracycline hydrochloride could be well attributed to the pseudo-second-order kinetic and Langmuir isotherm models. Compared with traditional carbon-based adsorbents, it owns a simpler synthesis method and a higher adsorption capacity, as well as it is a promising candidate for water purification.

In the present study, composites of Polyaniline and some fruit peels were synthesized in various conditions and used for lead removal from aqueous solutions. Adsorption tests were conducted in batch mode using the most efficient adsorbent, and the effects of medium pH, initial lead concentration, contact time, adsorbent dosage, and adsorption isotherms were investigated. The results showed that all composites were more efficient in lead removal compared to the fruit peels alone. The highest removal percentage was related to the composite of banana peel and Polyaniline that synthesized in the aqueous solution in the presence of 2 g·L−1 Poly ethylene glycol. This composite showed 95.96% lead adsorption at pH=6, the contact time of 90 min, the initial lead concentration of 25 mg·L−1, and an adsorbent concentration of 8 g·L−1. Adsorption isotherm study showed that adsorption of lead by synthesized composite could be fitted by both Langmuir and Freundlich models, but the Langmuir model was more fitted than Freundlich. Besides, some characteristics of the composites, such as chemical composition (XRD analysis), structure, and morphology (SEM analysis) and functional groups (FTIR analysis), were studied.

In this study, three kinds of amide functional group modified hyper-cross-linked adsorption resin were synthesized by alternating radical copolymerization in simple one-step and applied for 5-hydroxymethylfurfural (5-HMF) adsorption. The successful synthesis and properties of adsorbents were evaluated with Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, and elemental analysis. Poly (N, N’-4,4’-diphenylmethane-bismaleimide-alt-divinylbenzene) (poly (BDM-alt-DVB)) resin exhibited highest adsorption capacity for 5-HMF (64.0 mg·g–1 wet resin) and excellent adsorption selectivity (α5-HMF/LA=2.71±0.12, α5-HMF/FA=13.88±0.15, α5-HMF/Glucose=11.91±1.11) in the multi-component solution at 25 °C. Langmuir isotherm model well fitted the equilibrium adsorption data within the initial 5-HMF concentration range of 0.5–10.0 g·L–1 with highest correlation coefficient. Furthermore, the thermodynamic parameters demonstrated that the adsorption of 5-HMF onto poly (BDM-alt-DVB) resin was spontaneous and exothermic. Kinetic study revealed that the adsorption process was fast, reaching equilibrium within 12 min. Importantly, the poly (BDM-alt-DVB) resin also demonstrated excellent reusability. In summary, the poly (BDM-alt-DVB) resin will be useful in 5-HMF hydrolysate separation applications.

Adsorption is a simple and efficient phosphorus removal method used to control the eutrophication of water bodies. A simple and gentle atmospheric pressure hydrothermal method by adjusting the dosage of ammonium chloride and sodium hydroxide was used to synthesize amorphous, monoclinic, and tetragonal zirconia nano-powders with high specific surface areas (383.91 m2/g, 330.01 m2/g, and 234.36 m2/g) and particle size of about 40 nm for phosphate adsorption. When pH = 6.3, the phosphate adsorption capacity of the amorphous monoclinic phase and the tetragonal phase respectively reached 102.58 mg P/g, 68.11 mg P/g, and 37.25 mg P/g and the adsorption process of the three crystal forms of zirconia powders conformed to the Langmuir adsorption model. In the first 2 min of rapid adsorption, amorphous zirconia completed 76.23% of the adsorption process and the monoclinic phase also completed more than 60%. The adsorption process of the three crystal forms of zirconia was completed within 240 min and conformed to the pseudo-second-order kinetic model. Their adsorption characteristics of the three crystal forms of zirconia decreased with the increase in pH. While the pH was above than the isoelectric point of the solution, the adsorption capacity was significantly reduced. The large specific surface area and high hydroxyl content of the zirconia nano-powder made a great contribution to the adsorption process.

Facile fabrication of the ultra-high-performance adsorbent can effectively ameliorate the Cr(VI)-pollution elimination in sewage control. Herein, a simple synthesis strategy is proposed to tap a versatile chelating resin poly(pyrogallol-tetraethylene pentamine) (PPTA) with respect to Cr(VI) removal from solution. Multiple changing factors which affect the adsorption behavior of PPTA are explored sequentially, such as initial pH, adsorbate concentration, adsorbent dosage, temperature, foreign ions etc. The microstructure and functional mechanism of synthetic adsorbent are investigated systematically by means of various characterizations including TEM, EDS, FT-IR, XPS, etc. Consequently, as-prepared PPTA-3 microsphere by the reactant ratio of 1: 1 represents a brilliant synergistic adsorption and reduction result for Cr(VI) by the drastic electrostatic interaction of -NH3+ and -OH2+ groups, including satisfactory removal efficiency which closes to 100 % in low concentration, favorable specificity for the influence from coexistent ions (Mo(VI), Mn(VII), Cl-, Cr(III), etc), and passable recyclability. Following the surpassingly fitting with Langmuir isotherm model, its maximum capacity reaches 714.29 mg g-1 at 30 °C. The removal performance is essentially in agreement with the pseudo-second-order kinetics, simultaneously, suffers the rate-limiting impact depending on intra-particle diffusion process. In brief, this newly developed chelating resin presents an effective means with regard to the Cr(VI)-wastewater treatment or other uses in the future.

This study developed a method to fabricate a surface-oxidized rigid carbon foam (ORCF) with hierarchical macro-nanoporous structure via KOH activation of the carbon foam with two kinds of macropores followed by HNO3 hydrothermal oxidation. The structures of the prepared ORCF were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy, and N2 adsorption-desorption analyzer. Results demonstrate that the ORCF possesses a fluffy and porous structure with rich oxygen-containing groups. There are numerous through-holes on its pore surfaces connected with two-level macropores forming hierarchical macroporous channels. Meanwhile, the ORCF remains a good bulk structure with a compression strength of 0.74 MPa at a bulk density of 0.09 g cm−3. Batch adsorption experiments for malachite green (MG) and Pb2+ were studied through the single variable method to investigate the effects of different initial conditions on its adsorption process. The ORCF has maximum adsorption capacities for MG and Pb2+ of 587.68 mg g−1 and 157.80 mg g−1 with high partition coefficients of 17.41 mg g−1 µM−1 and 14.86 mg g−1 µM−1, respectively. The experimental data are suitable for Langmuir isotherm and Pseudo-second-order kinetic models, which correspond to monolayer chemisorption. Thermodynamic analysis indicates that the adsorption process is spontaneous and endothermic. Moreover, the removal percentages of MG and Pb2+ by the ORCF could remain above 90% after five cycles, implying that the ORCF is an efficient adsorbent with good adsorption ability and cycling stability.

Textile wastewater contains highly toxic, nondegradable, carcinogenic organic pollutants, causing severe damage to the ecological environment. In this work, β-cyclodextrin carbon-sphere-based nanocomposite (CS/SiO2@β-CD) with a core–shell–shell configuration was prepared by hydrothermal synthesis and subsequent sedimentation-azeotropic distillation with SiO2 as intermediate layer for the removal of crystal violet (CV) and bisphenol A (BPA). The chemical structure and morphology of the CS/SiO2@β-CD were characterized by FT-IR, SEM and TEM. The effects of contact time, pH, temperature and initial concentration of the absorbates on the adsorption property were explored. The CS/SiO2@β-CD showed excellent adsorption capacity on CV and BPA, and the maximum adsorption capacity was 87.873 mg g–1 and 165.095 mg g–1, respectively. Their adsorption process was in line with the pseudo-second-order and pseudo-first-order kinetic models, respectively. The adsorption thermodynamics could be better fitted by Langmuir model than by Freundlich model. The calculated thermodynamic parameters (–ΔG0, ΔS0 and ΔH0) illustrated the adsorption of CV was endothermic, in contrast, the adsorption of BPA was exothermic process. Furthermore, the CS/SiO2@β-CD showed excellent recovery performance, making it a potential adsorbent for the practical treatment of textile wastewater.

Development of polymeric magnetic adsorbents is a promising approach to obtain efficient treatment of contaminated water. However, the synthesis of magnetic composites involving multiple components frequently involves tedious preparation steps. In the present study, a magnetic chitosan-palygorskite (MCP) nanocomposite was prepared through a straight-forward one pot synthesis approach to evaluate its lead (Pb2+) removal capacity from aqueous solution. The nano-architectural and physicochemical properties of the newly-developed MCP composite were described via micro- and nano-morphological analyses, and crystallinity, surface porosity and magnetic susceptibility measurements. The MCP nanocomposite was capable to remove up to 58.5 mg Pb2+ g−1 of MCP from water with a good agreement of experimental data to the Langmuir isotherm model (R2 = 0.98). The Pb2+ adsorption process on MCP was a multistep diffusion-controlled phenomenon evidenced by the well-fitting of kinetic adsorption data to the intra-particle diffusion model (R2 = 0.96). Thermodynamic analysis suggested that the adsorption process at low Pb2+ concentration was controlled by chemisorption, whereas that at high Pb2+ concentration was dominated by physical adsorption. X-ray photoelectron and Fourier transform infrared spectroscopy results suggested that the Pb adsorption on MCP was governed by surface complexation and chemical reduction mechanisms. During regeneration, the MCP retained 82% Pb2+ adsorption capacity following four adsorption–desorption cycles with ease to recover the adsorbent using its strong magnetic property. These findings highlight the enhanced structural properties of the easily-prepared nanocomposite which holds outstanding potential to be used as an inexpensive and green adsorbent for remediating Pb2+ contaminated water. Refereed/Peer-reviewed

Polymers of intrinsic microporosity (PIM-1) has demonstrated great potential in adsorption and separation fields. In this study, PIM-1 was structured into an applicable and efficient adsorbent using a facile way. PIM-1 was first modified by amidoxime, and then the amidoxime modified PIM-1 (AOPIM-1) was mingled into alginate (Alg) hydrogel to obtain composite hydrogel beads. The AOPIM-1/Alg composite beads were further employed for removal of malachite green (MG) from aqueous solution and the effects of doped ratio, adsorbent dosage, contact time, and initial dye concentration on the MG adsorption performance were systematically investigated. The MG adsorption capacity of pure Alg beads was substantially enhanced after incorporating AOPIM-1. Furthermore, isothermal, kinetic and thermodynamic studies were performed to explore the fundamental adsorption behavior. Both Freundlich isotherm and Langmuir isotherm models can fit the adsorption isotherm data well, and the adsorption kinetics is well described by Pseudo-second-order. The adsorption process is feasible, spontaneous and endothermic. In addition, mixed dyes adsorption measurements indicate that AOPIM-1/Alg beads are highly selective to adsorb cationic dyes from anionic/cationic mixed dyes solution. The regeneration test shows that above 90% of the adsorption capacity of the composite beads can be maintained after 10 cycles of MG adsorption/desorption. These findings point that AOPIM-1/Alg composite hydrogel beads are an efficient, up-and-coming and recyclable adsorbent for cationic dyes adsorption from aqueous solution.

The MnO2@ZIF-8 core–shell nanoparticles for highly efficient dye degradation have been synthesized with a green method. ZIF-8 crystals with controlled morphology and size are first synthesized by using peptide to modulate the crystal growth. MnO2 is then coated on ZIF-8 via in situ reaction. The surface MnO2 density can be controlled by the dosage of KMnO4. The MnO2@ZIF-8 nanoparticles work as photocatalyst to degrade rhodamine B in a Fenton-like process, giving a degradation ratio of > 96.0%. The degradation kinetics comply well with the Pseudo-second-order model and the experimental equilibrium data meet the Langmuir model best. The specific hierarchical structure of MnO2@ZIF-8 assures a synergistic enhancement of the catalytic degradation performance from several aspects. First, anchoring of the MnO2 nanoparticles on ZIF-8 allows their well disperse to provide more active surface area. Second, highly porous ZIF-8 can adsorb dye molecules to accumulate them at the surface reactive sites. Third, the MnO2/ZIF-8 nano-heterojunctions enhance charge carrier transfer and accelerate the production of free oxidative radicals. The study demonstrates a green method for fabrication of hierarchical hybrid structures, paving the way for designing novel photocatalysts with potential applications for wastewater treatment.

A novel copper-based MOFs adsorbent (Cu-BTC-Th) was prepared using an one-step method by introducing a new organic ligand of 4-thioureidobenzoicacid (Th) with active groups for selectively adsorbing Pb(II) from aqueous solutions. The chemical composition and structure of the prepared MOFs materials were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS ), Brunner−Emmet−Teller (BET) analysis, and zeta potential measurements. The adsorption capability of the prepared Cu-MOFs was significantly enhanced by introducing the new organic ligand of Th in the materials. The maximum adsorption capacity of the Cu-BTC-Th for Pb(II) attains 732.86 mg/g under the optimal conditions. In addition, the adsorption kinetics and adsorption isotherm analysis showed that the adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption model, indicating that the adsorption of Pb(II) by Cu-BTC-Th was a monolayer chemisorption. The adsorption mechanism of Cu-BTC-Th for Pb(II) was discussed and revealed. On one hand, the adsorption of Pb(II) is mainly through ion exchange with the Cu(II). On the other hand, the −NH2 and −C=S functional groups introduced in the Cu-BTC-Th materials have stronger coordination ability with the Pb(II) ions to enhance the adsorption capability.

Excess fluoride in water poses a threat to ecology and human health, which has attracted global attention. In this study, a series of lanthanum-based metal–organic frameworks (La-MOFs) were synthesized by varying the organic ligands (i.e., terephthalic acid (BDC), trimesic acid (BTC), biphenyl-4,4-dicarboxylic acid (BPDC), 2,5-dihydroxyterephthalic acid (BHTA), and 1,2,4,5-benzenetetracarboxylic acid (PMA)) to control the microscopic structure of the MOFs and subsequently apply them for the removal of fluoride in water. The maximum capture capacities of La-BTC, La-BPDC, La-BHTA, La-PMA, and La-BDC at 298 K are 105.2, 125.9, 145.5, 158.9, and 171.7 mg g−1, respectively. The adsorption capacity is greater than most reported adsorbents. The adsorption isotherms of La-MOFs for fluoride are well fit to the Langmuir isotherm model. In addition, the adsorption kinetics of La-BTC, La-BPDC, La-BHTA, La-PMA, and La-BDC follows the pseudo-second-order kinetic model, and the kinetic rate-limiting step of adsorption is chemical adsorption. Thermodynamics revealed that temperature is favorable for the adsorption of fluoride. Meanwhile, La-BTC, La-BPDC, La-BHTA, La-PMA, and La-BDC are suitable for the removal of fluoride in a relatively wide pH range (4.0–9.0). Simultaneously, from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis, electrostatic attraction and ligand exchange are identified as the main action mechanisms for the adsorption of fluoride of La-MOFs. The prepared La-MOFs are used as efficient adsorbents for removal of fluoride in actual water, indicating that they have great potential in removing fluoride in real and complex environmental water. This work provides a new strategy for designing adsorbents with adjustable microstructure and expected function to effectively recover fluorosis in water.

To efficiently remove high concentrations of hexavalent chromium (Cr(VI)), calcium–aluminum-layered double hydroxide (CaAl-LDH, denoted as CAL), and polypyrrole-modified CAL (CAL-PPy) were prepared by hydrothermal and in situ polymerization methods, respectively. The chemical structure, morphology, and elemental results indicated that the chain-like polypyrrole was decorated with hexagonal CAL. The specific surface area of CAL-PPy increased from 8.746 m2/g to 24.24 m2/g. The adsorption performances of CAL and CAL-PPy for aqueous Cr(VI) were investigated using batch equilibrium experiments. The decontamination process of aqueous Cr(VI) (100 mg/L) reached the equilibrium state within 50 min, and the kinetic data met the pseudo-second-order kinetic equation. The Langmuir model described the isothermal data properly, and the obtained theoretical adsorption capacity of CAL for Cr(VI) at 318 K was 34.06 mg/g, while that of CAL-PPy was 66.14 mg/g. The removal mechanisms involved electrostatic attraction, surface complexation, anion exchange, and reduction to low-toxicity Cr(III). Therefore, CAL and CAL-PPy have underlying applications in treating real wastewater containing Cr(VI).

Efficient adsorption of Ba ions was achieved using Sn@TiO2 nanocomposite generated by ultrasonication process with subsequent calcination at 300 °C. X-ray diffraction, nitrogen adsorption-desorption isotherm, X-ray photoelectron spectroscopy, Fourier transformer infra-red, and scanning/transmission electron microscopy analyses were performed to probe the structural and textural features of the adsorbent powder. The XPS, FTIR, and EDX analyses confirmed the Sn doping into TiO2 host lattice. Some interesting features, including the increase of crystallite size and lattice parameters, were attained due to the successful Sn incorporation into the TiO2 host, as indicated further by XRD analysis. The sorption results fitted the Langmuir isotherm model and the kinetic data complied with the pseudo-second-order kinetics. The adsorption process improved markedly above the pHzc due to the electrostatic attraction between the negatively charged Sn@TiO2 particles’ surface and the positively charged Ba ions. The achieved high-performance mesoporous Sn@TiO2 nanostructures for the adsorption of Ba2+ could be potentially utilized to remove other toxic metal cations.

A novel Fe/Co metal organic complex nanosheet modified by 1,4-dicarboxybenzene (BDC), i.e., FeCo@BDC, was prepared, and highly efficient removal performance for trace lead (II) (Pb2+) was demonstrated in the neutral aqueous solutions. The removal rates were higher than 95% and the adsorption was equilibrated in 15 min. The isotherms and kinetics for the adsorption Pb2+ by the FeCo@BDC adsorbents followed Langmuir model and pseudo-second-order model, respectively. The maximum adsorption capacity was 220.48 mg•g−1. The FeCo@BDC adsorbents also own a prominent regeneration performance. The prominent performance of in the removal of trace Pb2+ makes FeCo@BDC an ideal candidate as commercial adsorbent materials.

Fluoride removal techniques have been studied for several years. In recent years various fluoride removal techniques have been developed in order to curb the health hazards from fluoride. Adsorption is the most widely used and researched method due to its advantages like economy, highly efficient, simplicity of application etc., over all other available defluoridation methods. This paper deals with the study of adsorption of fluoride using black mustard husk ash as an adsorbing material. The process parameters like pH, adsorbent dose, contact time and stirring rate were optimized using a three- level, four-factor, Box–Behnken design. The regression analysis of the experimental data acquired from 27 runs aided to develop a second order mathematical model in order to predict the fluoride removal efficiency. Using the response optimization, the optimum fluoride removal efficiency was found to be around 87%. The surface response graphs for the different process parameters were plotted and analyzed for studying their effect on adsorption phenomenon. The p-value obtained from the Analysis of Variance model suggested that the model was significant (p-value less than 0.005). The optimum values of pH, contact time, stirring rate and adsorbent dose were found to be 5, 75 min, 200 rpm and 2 g respectively. The predicted and adjusted R2 values were found to be 0.9177 and 0.9264 respectively. Adsorption models like Freundlich and Langmuir were used to validate the results. Langmuir model was seen best fiiting with the results having a R2 value equal to 0.9029. Pseudo first order kinetics and pseudo second order kinetic modelling was studied. The kinetic models showed the influence of physisorption as well as some amount of chemisorption in the adsorption process. From the results obtained it was concluded that the black mustard husk can be efficiently utilized for adsorption of fluoride from water.

The three organic residuals of pistachio, peanut, and almond were investigated for the removal capacity and removal mechanism of cadmium ion from aqueous. Adsorption efficiency on reducing cadmium was evaluated with batch experiment parameters, contact time, sorbent dose, pH, and Cd2+ amount. The sorption process of metal ions was defined well with the pseudo-second order kinetic, and Langmuir isotherm model having an adsorption capacity (qe(max)) of 51.28 mg g(-1) of pistachio, 62.11 mg g(-1) of peanut, 78.74 mg g(-1) of almond. The adsorbent was characterized by SEM, FTIR, and elemental analysis. The characterization study revealed that recycled lignocelluloses are composed of rough and porous surfaces with many active sites, contribute to metal ions removal in many ways, such as electrostatic interaction, ion exchange, complex formation, and physical adsorption. These findings highlighted that the shells can be effectively applied removal of divalent metal from aquatic solution. (C) 2021 THE AUTHOR. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.

A study of corrosion inhibition of mild steel by Rhoeo discolors plant extract in 0.5 M HCl solution was carried out by potentiodynamic polarization and electrochemical impedance methods. The different concentration of inhibitor was used ranging between 0.2 g/L−2 g/L in the electrolyte. To determine the efficiency and rate of corrosion at different temperatures say 308 K, 313 K, 318 K. A consequence drop in the rate of corrosion is observed when a higher the concentration of plant extract was used at a higher temperature. It is also observed that a rate of corrosion was increased on concentration of inhibitor with rising in temperature. The use of 2.0 g/L plant extract in the potentiodynamic study shows inhibition efficiency 87.72% (308 K), 79.78% (313 K) and 74.84% (318 K). For electrochemical impedance shows 82.23% (308 K), 79.22%(313 K), 71.20% (318 K).The graph plotted by using log I on x-axis P on y-axis indicates inhibitor controls both anodic and cathodic reactions. It is also observed the value of Ea for inhibited solution ranging from 16.8 kJ/mol to 72.95 kJ/mol, these results interpret physical adsorption of inhibitor over the metal surface leading to the formation of adsorbate film of electrostatic character The positive values of entropy ranging from 26.93 kJ/mol to 73.01 kJ/mol indicates the endothermic nature of physical adsorption and disordering of adsorbent film over the metal surface. At finally it obeys the Langmuir adsorption isotherm.

An Environmentally friendly method is reported for the synthesis of nanoscale CadmiumOxide using plant extract as a reducing agent. Cadmium oxide was synthesised by a simple solution combustion method using Cadmium Chloride monohydrate and Phyllantus Emblica extract and calcined at elevated temperatures. Biosynthesised CadmiumOxide Nanoparticles (CdONPs) was calcinated at different temperatures like 70, 200, 400 and 600 °C. CdONPs calcined at higher temperature was appraised for the removal of Rhodamine B (RhB) from aqueous solution. The developed adsorbent was characterized by TGA, DTA, FTIR, XRD, FESEM, EDAX and TEM. XRD revealed that Cd(OH)2 nanoparticles with hexagonal structure transform into CdONPs with cubic structure. The adsorption ability of the CdONPs was systematically investigated using batch experiments. The factors investigated include initial concentration, adsorbent dosage, contact time and pH. The CdONPs, calcined at 600 °C exhibit good nanomaterial for the removal of RhB (93% degradation of RhB for 0.1 g dosage within 80 min). Adsorption follows Langmuir isotherm and ΔG° = −79.55 KJ/mol indicates that the adsorption is chemisorption and spontaneous. The kinetic data for the adsorption process obeyed a pseudo-second-order kinetic model with R2 of 0.99. Present work has proved that CdONP is a novel low-cost nanomaterial and plays an important role in environmental protection.

In this study, an iron(III)-loaded magnetic chitosan/graphene oxide composite (Fe-MCG) was synthesized and applied for the adsorptive removal of sulfosalicylic acid (SSA) in aqueous solution. The results obtained from the application of various characterization techniques such as scanning electron microscopy (SEM), vibrating-sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS) prove the successful formation of the composite with enhanced microstructure and superparamagnetic properties. The adsorption capacity of Fe-MCG towards SSA via batch mode reaches up to 135 mg/g at 293 K. The adsorption of SSA onto Fe-MCG is driven by monolayer adsorption with the chemical and physical adsorption processes both playing active roles. The Langmuir isotherm and pseudo-second-order kinetic models were observed to best describe the equilibrium adsorption and kinetic processes, respectively. The values obtained for the associated thermodynamic parameters confirm that the adsorptive process is spontaneous, exothermic and entropy-increasing. The efficacy and reusability of the spent Fe-MCG was studied using 0.01 mol/L NaOH solution. The kinetic process for the desorption of SSA from Fe-MCG is well described by the pseudo-second-order kinetic model. Based on the experimental results and XPS analysis, the underlying mechanisms for the uptake of SSA onto Fe-MCG involve electrostatic forces, complexation, π-π stacking, and hydrogen bonding. Overall, the excellent features of Fe-MCG enhance its potential as an adsorbent for the sequestration of SSA in environmental media.

In the present study biopolymers were used as adsorbents to treat Cr (VI) ions from the aqueous solutions. Chitin prepared using sea shells (CS) and commercially available chitin (CC) was used for the adsorption studies on Chromium VI removal from the synthetic waste water. Chitin was extracted from sea shells by two step procedure and was characterized for the composition, functional groups, surface morphology and the yield. Sorption tests were done at room temperature by varying the metrics like initial metal ion concentration, contact time, pH, and adsorbent dosage. The optimized parameters were: pH 2, 50 ppm Cr (VI) concentration, and 4 g/L of adsorbent dosage and contact time of 60 min. Isotherm and kinetic studies were carried out, the sorption capacities of CS and CC for Langmuir isotherm were 9.52 and 5.62 mg/g and that of the Freundlich isotherm was 0.542 and 3.68 mg/g. The intensity of adsorption was better for CS than CC suggesting the feasibility of adsorption. Both CC and CS exhibited better rate constant for a pseudo II order model which suggests that pseudo II order model best described the Cr (VI) adsorption kinetics on biopolymers.

Present communication reports on the synthesis, characterization and application of Fe3O4-chitosan composite (MCC). The magnetic chitosan composite are crafted by mixing Fe3O4 nanoparticles solution to chitosan solution. Fe3O4 nanoparticles have been synthesized by co-precipitation method. The synthesized composite have been extensively characterized using various techniques such as FTIR, TEM, XRD and BET analysis. The surface area analysis suggested that the materials synthesized is mesoporous in nature. Incorporation of chitosan crosslinked actively with Fe3O4 nanoparticles that results in reduction of surface area and narrower pore size distribution of the composite than pure Fe3O4 nanoparticles. TEM study demonstrated that Fe3O4 nanoparticles were found in the range of 20–25 nm. The synthesized composite is able to capture more than 89% Cd(II) from synthetic Cd(II) solution within 80 min of contact time. The adsorption equilibrium data better conformed with the Langmuir isotherm. The maximum capacity determined from Langmuir isotherm was 149.92 mg/g at 323 K. Adsorption kinetics of cadmium on MCC could be well analyzed with pseudo-second-order kinetic model. Thermodynamics investigation reveals that with the increase of solution temperature 303 K, 313 K and 323 K the ΔGo values decreases correspondingly to −87.76, −90.36 and -93.36 KJ/mol, suggesting endothermic nature of the adsorption process. The adsorbent could be successfully reused for more than five cycles. Thus, MCC can be serves as a reliable and sustainable material for efficient sequestration of Cd(II) species from aqueous environment.

A novel polystyrene-poly(hydroxamic acid) interpenetrating network resin (PS-PHA IPNs) was successfully synthesized by suspension polymerization and interpenetrating network technology. The effects of various experimental parameters, including pH, contact time and initial concentrations of rare earth ions on the adsorption capacity were discussed in detail. Under the condition of pH 4.0 (La3+), 1.0 (Ce3+) and 3.0 (Y3+), respectively, PS-PHA IPNs can reach equilibrium adsorption in 6 h and get maximum adsorption capacities (1.08, 1.43 and 1.36 mmol/g). The adsorption process of PS-PHA IPNs for La(III), Ce(III) and Y(III) ions can be described by liquid membrane diffusion, particle diffusion and chemical reaction. The adsorption process is a spontaneous and endothermic process and can be better simulated by Langmuir adsorption isotherm. The studies of SEM-EDS indicate that rare earth ions are adsorbed on the surface of PS-PHA IPNs. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis further prove that rare earth ions are chemisorbed on the surface of PS-PHA IPNs. These results reveal that the as-prepared PS-PHA IPNs is a promising adsorbent for adsorption of rare earth ions due to their higher adsorption capacity than other adsorbents.

Textile dyes are considered to be hazardous waste for the environment. Treatment with eco-friendly way is the only solution to protect the environment from this hazardous material. The present research focused on the removal of textile dyes with bio adsorbents. This research work aims to extract fibers from waste groundnut shells (GNS) as a bio adsorbent. The efficiency of the obtained fiber mass as an adsorbent was examined over a dye to gauge its adsorbing potential and expulsion. For the purpose stated, Methylene Blue Dye (MBD) was selected as a model dye. The potential capacity of the obtained groundnut shell fibers (GNSF) was studied by optimizing various parameters such as pH, temperature, initial dye concentration, adsorbent dosage, agitation, and contact time in the batch study. The percentage removal of dye achieved by the fibers obtained from the groundnut shell was 99.5% at mixing speed 150 RPM; temperature 25 °C; dye concentration 10 mg/L; adsorbent dosage: 5 mg/L and time 24 h. The extracted fibers and adsorbed fibers were characterized using FTIR, XRD, and SEM analysis to study various properties such as functional group, chemical characteristics, and morphological studies. The obtained results were well fitted in Langmuir isotherm, Freundlich isotherm, and Temkin isotherm models. The Freundlich model fits the best.

Recently, metal-based carbon materials have been verified to be an effective persulfate activator, but secondary pollution caused by metal leaching is inevitable. Hence, a green metal-free 3D macroscopic N-doped porous carbon nanosheets (NPCN) was synthesized successfully. The obtained NPCN showed high adsorption capacity of tetracycline (TC) and excellent persulfate (PS) activation ability, especially when calcined at 700 °C (NPCN-700). The maximum adsorption capacity of NPCN-700 was 121.51 mg/g by H-bonds interactions. Moreover, the adsorption process followed pseudo-second-order kinetics model and Langmuir adsorption isotherm. The large specific surface area (365.27 mg/g) and hierarchical porous structure of NPCN-700 reduced the mass transfer resistance and increased the adsorption capacity. About 96.39% of TC was removed after adding PS. The effective adsorption of the catalyst greatly shortened the time for the target organic molecules to migrate to the catalyst. Moreover, the NPCN-700 demonstrated high reusability with the TC removal rate of 80.23% after 4 cycles. Quenching experiment and electron paramagnetic resonance (EPR) test confirmed the non-radical mechanism dominated by 1O2. More importantly, the C = O groups, defects and Graphitic N acted as active sites to generate 1O2. Correspondingly, electrochemical measurement revealed the direct electron transfer pathway of TC degradation. Finally, multiple degradation intermediates were recognized by the LC-MS measurement and three possible degradation pathways were proposed. Overall, the prepared NPCN had excellent application prospects for removal of antibiotics due to its remarkable adsorption and catalytic degradation capabilities.

Recently, biochar-related phosphate sorbents have been extensively investigated and achieved significant progress; however, there is still much room for enhancement on capturing performance and recovery of powdery ones after sorption. Herein, a new kind of adsorbent, in which biochar/Mg-Al spinel encapsulated in carboxymethyl cellulose-La hydrogels with cationic polymeric layers, was fabricated, aiming for integrating multi-advantages of each component for enhanced phosphate capture. Batch static experiments were correlated to the phosphate adsorption performance of the adsorbent. The maximum phosphate adsorption capacity of the adsorbent was 89.65 mg P/g at pH = 3. The Langmuir isotherm model and the pseudo-second-order kinetic model fitted well with the adsorption behavior of the adsorbent. More importantly, this composite adsorbent that integrated with biochar, Mg-Al spinel, cationic polymeric components exhibited favorable selectivity over coexisting anions (Cl-, SO42-, HCO3– and NO3–) and performed good reusability after five consecutive cycles. By virtue of the bead-like feature, fixed-bed column experiments demonstrated that the Thomas model fitted the breakthrough curves well under varied experimental conditions. The adsorption mechanism of phosphate on the designed composite adsorbent with multi-components could be described as the electrostatic attraction, ligand exchange and inner-sphere complexation, which might account for the efficient phosphate capturing performance.

Polymer/composite materials have been commonly used as corrosion inhibitors in different fields such as marine, oil field, and engineering industry due to their self-healing and thermal stability features. Herein, novel polythiadiazole, namely poly[(2,6-dicarbonylpyridine)(2,5-dihydrazinyl-1,3,4-thiadiazole)] (AMTP) via the interaction of 2,5-dihydrazinyl-1,3,4-thiadiazole with pyridine-2,6-dicarbonyl dichloride and its composite with α-Al(OH)3-gel were designed in a good yield. The structures of the fabricated materials are characterized by FT-IR, NMR, SEM, and UV–Vis analyses. The protective action of AMTP and α-Al(OH)3@AMTP on the C1018-steel corrosion in molar-sulphuric acid was evaluated by potentiodynamic-polarization (PDP) and electrochemical impedance spectroscopic (EIS) methods. PDP findings presented that the AMTP polymer and α-Al(OH)3@AMTP composite performed as mixed-type inhibitors. The protection capacities of 90.3 and 97.6% were obtained in the presence of optimum dose 100 mg/L of AMTP polymer and α-Al(OH)3@AMTP composite, respectively. The compound's adsorption on C1018-steel follows the Langmuir isotherm model. The SEM/EDX outcomes reveal that the C1018-steel interface is inhibited by AMTP polymer and α-Al(OH)3@AMTP composite. DFT calculations exhibited that the efficiency of the prepared materials correlates well with their electron contributing capability, whereas simulations of Monte Carlo exposed that the favorability and extent of adsorption of additive molecules metal interface establish their corrosion protection routines.

Chitosan capped Fe0-based Fe-Pd-Ir (Chi-Fe-Pd-Ir) tri-metallic nanoparticles were fabricated using metal displacement method in presence of sodium borohydride. The preliminary indications of Fe0 production were the appearance of pale yellow color with ferric nitrate, NaBH4, and chitosan. Chitosan was detected by using ninhydrin color test, thermal gravimetric analysis and measurement of relative viscosity. The average molecular weight of chitosan and Chi-Fe-Pd-Ir decreased with increased potassium persulfate concentration. Chi-Fe-Pd-Ir used as an adsorbent for the removal of Congo red. The sorption equilibrium data were fitted into Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms (DRK). The maximum monolayer adsorption capacity (Q0max), and sorption intensity (n) were estimated to be 93.4 mg/g and 2.0, respectively, from Langmuir and Freundlich adsorption isotherm models. The mean free energy was calculated by using DRK isotherm to be 0.15 kJ/mol. Sorption parameters indicate that the Congo red adsorbed on the surface of Chi-Fe-Pd-Ir through monolayer formation via physisorption process. The adsorption of CR on Chi-Fe-Pd-Ir was in good agreement with the Langmuir adsorption isotherm and pseudo-second-order kinetic model. Protonated amino group of chitosan was also responsible for the adsorption of anionic CR along with the Fe-Pd-Ir NPs.

In this study, organo-funtionalization of sodium-alginate has been carried out using phenylsemicarbazide as modifier to graft N, O-donor atoms containing functional groups (amino-carbamate moieties) to offer novel support for TiO2 immobilization. Hybrid composite made of aminocarbamated alginate, carboxymethyl chitosan (CMC) and titanium oxide TiO2 (MCA-TiO2) was prepared for the promising adsorptive remediation of Ni(II). FT-IR, SEM-EDX were employed to characterize MCA-TiO2. The optimization of TiO2 to modified alginate mass ratio was carried out and hydrogel beads with TiO2/MCA mass ratio of 10.0% (2MCA-TiO2) revealed highest sorption efficiency. The produced sorbents were adapted in the form of hydrogel beads for operation. Organic functionalization based on aminocarbamate ( O CO NHNH2) moieties on linear chains of alginate embedded additional chelating functional sites which enhanced sorption and selectivity. Batch mode experiments were conducted for optimization of pH and sorbent dose. Equilibrium sorption, kinetic and thermodynamic studies were performed to pattern the nature of sorption. Kinetic data was found in close agreement with pseudo-second order rate expression (PSORE). Isothermal equilibrium sorption data was well fitted with Langmuir adsorption model. Maximum sorption capacity was evaluated as 229 mg/g at 298 K and pH = 6.0.

Nano-bentonite was prepared from Iraqi bentonite clay by the co-precipitation method and the adsorption technique was used under many factors to determine the adsorption capacity (q) and removal% of arsenic ions (As) from the hospital's wastewater. The optimization process was conducted to choose the optimal parameters for adsorption and removal of arsenic by applying the central composite design (CCD) to form a surface response with three levels and three central points. Three operational factors were optimized of pH (5.5), bentonite dose (100 mg/L), and contact time (5 min), as well as developing the regression quadratic equations to assess the important models for the arsenate adsorbing and removing which dependent on the correlation factor (R2) that was (q = 0.9998) and (removal% = 0.9709), the adsorption isotherm results were fit well with the Langmuir model (R2 = 0.972), and the adsorption kinetics results were perfect with the second model (R2 = 0.951). We conclude that bentonite clay is a good adsorbent that can be used in the processes of removing toxic ions from water.

Adsorption represents an attractive method to remove pesticide from contaminated water given its relatively low cost and simple process. This work evaluates the adsorption isotherms and kinetics of 2,4-dichlorophenoxyacetic acid (2,4-D) onto oil palm trunk-derived activated carbon (OPT-AC). Batch adsorption was performed to determine the effects of pH, temperature, initial adsorbate concentration, and contact time. The highest removal efficiency was obtained at pH 2 due to the absence of electrostatic repulsion between the adsorbent and the adsorbate as indicated by the point of zero charge ( p H pzc ) of 4.8 for OPT-AC and a p K a of 2.73 for 2,4-D. The adsorption isotherm data at 25, 35, and 45 °C and pH of 2 can be fitted better by the non-linear Langmuir model relative to the non-linear Freundlich model. Langmuir monolayer maximum adsorption capacity was found to be 420.43 mg g−1, which lies among the highest reported values for activated carbon materials used for 2,4-D removal. Adsorption kinetic data at 35 °C and pH of 2, on the other hand, can be better correlated by pseudo-second order (PSO) kinetic model compared to pseudo-first order (PFO) model, which implies the more dominant presence of chemisorption relative to physisorption. The high adsorption uptake of 2,4-D by OPT-AC highlights its potential as an attractive alternative to commercial AC particularly for medium to large scale 2,4-D removal from acidic wastewater.

A new approach for the treatment of effluent streams has been developed by synthesizing an innovative chitosan based terpolymer composite gaining a considerable attention in the wastewater treatment community. The present research article reports on the synthesis of terpolymer composite from 4,4′ – oxydianiline, carbohydrazide with formaldehyde and chitosan for the recovery of toxic and heavy metals from aqueous solutions. The synthesized adsorbents have been characterized by elemental analysis, spectral studies and surface morphology by scanning electron microscopy. Batch separation technique has been used in the ion-exchange process for the removal of selective metal ions like Co2+, Cd2+, Pb2+, Hg2+ by terpolymer and its composite. The results revealed that both the adsorbents are good ion-exchanger however, the composite act as better ion exchanger than the terpolymer. It may be due to the more active sets of amine and carbonyl groups present in terpolymer ligand and the size of particle, high porous and greater surface area, this result investigated by SEM analysis. The results of recovery of toxic metals were matched with the earlier reported terpolymer resins. The adsorption isotherm models were investigated and the results were found well fitted with Langmuir isotherm compared to Freundlich isotherm and follows first order kinetics.

Water pollution with copper (Cu) has a significant impact on the environment and human health. Within this context, the present study aims to synthesize a composite bead based on Moroccan natural clay from Chaouia (CH) and sodium alginate (Na-AL) as adsorbents to remove copper ions from aqueous solution. The adsorbents were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX) and Thermogravimetric Analysis (TGA). The effect of adsorbent dose, kinetic time, initial concentration of copper ions and temperature were investigated. Nonlinear regression was applied to fit the isothermal and kinetic models. The results showed that the clay is composed of kaolinite and quartz and the SEM confirmed the successful incorporation of sodium alginate into the clay. The adsorption process follows the Langmuir isotherm with a maximum adsorption capacity of 48.24 and 92.44 mg.g−1 for the clay (CH) and the beads composite designated as (CH@AL), respectively. Pseudo-second-order model best described the kinetic data. Moreover, the thermodynamics of the adsorption was spontaneous and endothermic. All of these results proved that the used adsorbents are eco-friendly and efficient for the adsorption of Cu(II) ions.

A new type of magnetic chitosan nanocomposites modified with graphene oxide and polyethyleneimine (MCS/GO-PEI) was synthesized, which was used as an adsorbent to remove the toxic heavy metals of As and Hg as well as anionic azo dyes of congo red and amaranth in environmental water. In this experiment, MCS/GO-PEI was first synthesized and the structure and morphology characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrometry (FT-IR), X-ray diffractometer (XRD), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS). The adsorption performance of the material for four analytes was investigated through adsorption experiments. The kinetic and isothermal results showed that the adsorption process was well described by pseudo-second-order kinetic and Langmuir isotherm model. Besides, the important parameter pH in the adsorption process was investigated and optimized. The maximum adsorption capacities of the nanocomposites for arsenic, mercury ions, congo red, amaranth were 220.26, 124.84, 162.07, 93.81 mg g−1 under optimum adsorption conditions, respectively. The adsorption-desorption showed that the adsorbents were presented adequate reusability. The as-prepared MCS/GO-PEI nanocomposite could serve as promising adsorbent for arsenic, mercury, congo red and amaranth in environmental water samples treatment technology.

Dyestuff in industrial wastewater continues to entail environmental pollution and thus developing an adsorbent with superior adsorption performance is urgently required for the survival of future generations. In this work, a novel Co– and H4dbp based metal-organic framework (MOF, denoted as Co-MOF) adsorbent was developed for the removal of methylene blue (MB) from aqueous solution. Hydrothermal synthesis was employed for the fabrication of the Co-MOF with phosphonic acid organic ligand. X-ray diffraction, Fourier-transform infrared spectroscopy, field emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption-desorption isothermal analysis were utilized for Co-MOF characterization. MB adsorption by as-prepared adsorbent obeys pseudo-second-order adsorption kinetics and follows Langmuir isotherm model with the maximum adsorption capacity of 147.99 mg g−1, which is superior to other analogies. Furthermore, the recoverability of this adsorbent material was astonishing with an excellent MB removal capacity of 89.34 % of initial dye concentration after the fifth cycle. The thermodynamic parameters affirm that this adsorption process exhibits a spontaneous endothermic process with sufficient molecular randomness due to the adsorbent-adsorbate interaction suggesting a great potentiality as an adsorbent to be used for industrial wastewater treatment to mitigate the environment.

Today, a variety of pesticides are used to fight plant pests in the world. The entry of these resistant pollutants into water resources can have devastating effects on human health and the environment, hence their removal from the environment is a vital task. In the present work, the magnetic iron-based metal-organic framework (Fe3O4/MIL-101 (Fe)) was synthesized by a simple and feasible method and characterized by FT-IR, XRD, BET, FESEM, TEM, TGA, and VSM techniques. The synthesized nanocomposite was successfully applied for the removal of fenitrothion (FEN) pesticide from the aqueous solutions. The isothermal and kinetic models were also investigated. The Langmuir isotherm model (type I) and pseudo-second-order kinetic model were more consistent in the adsorption process. The thermodynamic parameters of fenitrothion sorption were also calculated. The results revealed that the adsorption of fenitrothion onto Fe3O4/MIL-101 (Fe) was spontaneous and endothermic under optimized conditions. Moreover, the removal efficiency of FEN was predicted using the developed fuzzy logic model. Four input variables including the initial concentration of FEN (mg·L−1), pH of the solution, adsorbent dosage (mg), and contact time (min) versus removal efficiency as output were fuzzified by the usage of an artificial intelligence-based method. The fuzzy subsets consisted of Triangular and Trapezoidal membership functions (MFs) with six levels and a total of 23 rules in IF-THEN format which was applied on a Mamdani inference system. The obtained coefficient of determination value ( R pred 2 = 0.98205) proved the excellent accuracy of the fuzzy logic model as a powerful tool for the prediction of FEN removal efficiency.

Presence of toxic dyes in industrial wastewaters deteriorates the environment. Wastewater pollution control using locally obtainable agricultural by-products could be an eco-friendly and sustainable strategy. Efficiencies of activated carbons (AC) developed from empty fruit bunches (EFB) and mesocarp fibers (MF) of oil palm were evaluated in methylene blue (MB) and Acid orange 10 (AO10) dyes removal. Impacts of operational parameters including adsorbent dose, pH, initial concentration of dyes, and contact time were examined on dyes adsorption. Maximum adsorption values of MB (24.00 mg/g) and AO10 (18.76 mg/g) were achieved at pH 2 and 3, respectively, 50 mg/L initial dyes concentration, adsorbents dosage of 5 g/L, and 90 min contact time. Evaluation of adsorption isotherms revealed that the Freundlich model provided the best fit to the empirical data (R2 ≥ 0.692). MB isotherm through MF, however, was better represented by Langmuir model (R2 = 0.979). MF activated carbon showed higher capacity in immobilization of both dyes probably due to its larger surface area (552.72 m2/g) and porosity (0.4458 cm3/g). Dye adsorption on to the activated carbons go along with pseudo-second order kinetic model.

In this research, copper(II)-alginate (Cu(II)-A) beads containing polyethyleneterephthalate derived activated carbon (PET-AC) with porous structure were prepared by a feasible cross-linking technology. The composition and structure of the beads were thoroughly analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, scanning electron microscopy and energy dispersive X-ray methods. The desulfurization activity of the adsorbent for dibenzothiophene (DBT) in the model oil was investigated. The influence of mass ratio of PET-AC on the features of the prepared Cu(II)-A beads was studied. According to experimental results, higher adsorption capacity was acquired from PET-AC/Cu(II)-A at 4:1 mass ratio due to its high porosity and available Cu(II) adsorption centers. The adsorption isotherms could be correlated by the Langmuir isotherm and the maximum adsorption capacity reached up to 62.9 mg g−1. The adsorption data showed better fitting (R2 greater than 0.99) to the pseudo-second-order rate equation. Lewis acid-base and π–π interactions might be the driving force of the DBT adsorption. The adsorbent could be also reused for 4 successive runs with negligible loss in desulfurization capability. All of these features make the PET-AC/Cu(II)-A as a potential adsorbent towards desulfurization from fuels.

Nanomaterials have recently come to the fore as potential adsorbents due to their high surface, high efficiency, and adsorption capacity. This study the performance of polypyrrole nanotube incorporated sodium alginate (SA/PPyNT) on the adsorptive removal of methylene blue dye from an aqueous solution was investigated. Firstly, polypyrrole nanotubes were synthesized by oxidative chemical polymerization. Then, polypyrrole nanotubes were added to the sodium alginate gel and the composite beads were prepared by a crosslinking process in a 3% CaCl2 solution. The composite beads were characterized using Fourier transform infrared-attenuated total reflectance (FTIR-ATR), scanning electron microscope (SEM), and atomic force microscopy analyzes. In the adsorption studies, to determine the optimum conditions, experiments were carried out at different conditions namely temperature (25–45 °C), contact time, initial pH (2–12), adsorbent dosage (1–5 g/L), dye concentrations (10–50 mg/L). The studies indicated that the removal percentage of MB reached up to 90.5% at pH = 7 and 25 °C. Furthermore, different isotherm models such as Freundlich, Langmuir, D-R, and Harkins-Jura were applied. Considering the correlation coefficients, the Langmuir isotherm model was found to be the most suitable model (r2 = 0.9974). The adsorption capacity showed the maximum at 666.7 mg/g in pH = 7 at 25 °C. As a result of the kinetic studies, it was seen that adsorption followed the pseudo-second-order kinetic model (r2 = 0.9976). When thermodynamic parameters were examined, it was seen that the adsorption occurred exothermically (∆HA = − 68.1 kJ/mol) and spontaneously (∆GA298 = − 27.4 kJ/mol). From the data obtained, it was concluded that the SA/PPyNT composites are promising material as an adsorbent.

Phosphorylated chitosan (P-CS) was successfully synthesized using a facile experimental setup of hydrothermal method that was applied to the adsorption of anionic Acid Red 88 (AR88) from aqueous media. The adsorption process obeyed the pseudo-second-order (PSO) kinetic model. In contrast, the adsorption isotherm conformed to the Langmuir model, with the maximum adsorption capacity (qm = 230 mg g−1) at 303 K. Both external and intraparticle diffusion strongly influenced the rate of adsorption. The insights from this study reveal that P-CS could be easily prepared and regenerated for reusability applications. The adsorption mechanism and intermolecular interaction between P-CS and AR 88 were investigated using Fourier transform infrared (FTIR) spectroscopy and calculations via Density Functional Theory (DFT). The key modes of adsorption for the P-CS/AR 88 system are driven by electrostatic attractions, H-bonding, and n-π interactions. The findings herein reveal that P-CS is a promising adsorbent for the removal of anionic dyes such as AR88 or similar pollutants from water.

The chemically crosslinked silver titanium dioxide embedded Arabic gum grafted polyacrylamide-polyacrylonitrile nanocomposite AgTiO2@AG-g-P(AM-co-AN) was successfully synthesized and investigated by ATR-IR, XRD, and SEM. The synthesis optimization parameters of AG-g-P(AM-co-AN(were 5% AG, 1/0.5 AM/AN monomer molar ratio, 0.5 mg MBA cross-linker, and AgTiO2 content (1%) gives AgTiO2@AG-g-P(AM-co-AN) nanocomposite. While adsorption studies for AgTiO2@AG-g-P(AM-co-AN) were appear the maximum adsorption capacity (104.50 ± 3.02 mg/g) at concentration (150 mg/L), MB concentration (15 mg/L) and pH (8.0). The adsorption nonlinear kinetics models were used. Pseudo-second order governs the adsorption process, and the Langmuir model is more suited than Freundlich and Temkin.

Background This work aims at developing some environmental-friendly corrosion inhibitors for copper in neutral solution. Methods A glucose-based functionalized carbon dots (FCDs) was synthesized through a facile one-pot hydrothermal method. The inhibition performance of FCDs was firstly researched systematically on copper in neutral 3.5 wt% NaCl solution by potentiodynamic polarization curves, electrochemical impedance spectroscopy and scanning vibrating electrode technique. The above electrochemical results show that FCDs is an effective corrosion inhibitor for copper in neutral solution, and its optimal corrosion inhibition efficiency exceeds to 88% at 70 ppm. The protective performance of FCDs depends on the coverage of adsorption film on copper surface. Its adsorption isotherm is in accordance with Langmuir adsorption model, involving both physisorption and chemisorption. Atomic force-distance curve directly quantifies the adhesion force between the adsorption film and copper surface. Significant finds The adsorption and anticorrosion mechanism of FCDs in neutral solution is proposed, which could provide theoretical guidance for design and synthesis of nanomaterial corrosion inhibitor.