Competitive Adsorption Studies Research Articles

Interfacial self-assembled of covalent organic framework onto MXenes for efficient enrichment and recovery of Au(III) and Pd(II) from aqueous solution

Recovery of precious metal ions in wastewater could not only improve resource utilization, but also could reduce environmental pollution. Herein, a composite of TpPa@Nb2C was constructed by an interfacial self-assembled method and explored the synergistic adsorption effects for precious metals. The structure and morphology of the composites were analyzed by advanced characterization techniques, followed by parametric analysis of Au(III)/Pd(II) adsorption from the simulated wastewater. The results showed that the grafting of COFs with abundant reducing active sites on the MXenes could significantly improve the selectivity and adsorption capacity. Meanwhile, the interaction was found as monolayer way and controlled by chemistry process, and the maximum equilibrium Au(III) and Pd(II) uptake reached up to 910.1 and 386.2 mg/g, respectively. The competitive adsorption study showed that the co-existence of impurities had little effect on the removal rate. The mechanism analysis demonstrated that the precious metal ions were reduced to elemental gold/palladium on the network of TpPa@Nb2C, and they got three electrons or two electrons from the hydroxyl groups through redox reaction, respectively. Thus, this study provided an excellent material for enrichment and recovery of precious metals in waste liquid and the treatment of e-waste.

Tuning the pore chemistry of Zr-MOFs for efficient metal ion capture from complex streams.

Metal-organic frameworks (MOFs) have shown promise for adsorptive separations of metal ions. Herein, MOFs based on highly stable Zr(IV) building units were systematically functionalized with targeted metal binding groups. Through competitive adsorption studies, it was shown that the selectivity for different metal ions was directly tunable through functional group chemistry.

Evaluation of the photocatalytic degradation mechanism of methylene blue using nascent and Ag+ ions-modified TiO2.

In photocatalytic removal of organic pollutants, adsorption and degradation are two important processes that take place. Various instrumental techniques and trapping experiments have been used to identify the reactive species and the mechanism of photodegradation. The present work focuses on investigating the mechanism of photo-induced degradation from the comparative characterization of fresh and used samples, isotherm models, competitive adsorption, and desorption studies of pure and Ag+-modified TiO2 NPs. The comparative characterizations of fresh and used NPs were carried out with FT-IR, EDX, and XRF analyses after methylene blue (MB) degradation. The Ag+ doped TiO2 used in this study was fabricated using simple impregnation technique. The prepared NPs were characterized using techniques including XPS, XRD, SEM/EDX, XRF, UV-DRS, and pH point-zero charge analyses (pHPZC). The Ag+-modified TiO2 NPs showed improved efficiency compared to pure TiO2 NPs using normal compact fluorescent light (CFL). The Langmuir and Freundlich isotherm models were applied to test the adsorption behavior on the surface photocatalysts. The investigational data finest fitted to the Langmuir isotherms model compared to Freundlich model, suggesting the homogeneous monolayer adsorption followed by degradations. The competitive removal of MB in the presence of a photo-generated electrons trapper (Cd2+) was enhanced almost 3-folds (115mg/L) compared to the removal from a single MB solution (40mg/L). The characterization of the used samples as well as adsorption in the dark and negligible desorption of used samples support the involvement of the proposed photo-induced degradation mechanism.

Development of a Multicomponent Adsorption Isotherm Equation and Its Validation by Modeling.

Researchers have made significant efforts over the past few decades to understand adsorption by developing various simple adsorption isotherm models. However, though many contaminants usually occur as multicomponent mixtures in nature, multicomponent adsorption isotherms have received limited attention and remain an area of inadequate research. We have presented here in a new multicomponent adsorption isotherm model, named the Jeppu Amrutha Manipal Multicomponent (JAMM) isotherm, that can alleviate this problem. We first developed the JAMM multicomponent isotherm using our experimental data sets of arsenic and fluoride competitive adsorption on activated carbon. We then tested the JAMM multicomponent isotherm for a case study of cadmium and zinc competitive adsorption. Next, we further assessed the JAMM isotherm using another competitive adsorption case study of copper and chromium. Through extensive validation studies and error analysis, the JAMM isotherm was able to demonstrate its efficacy in predicting the adsorption behavior in several multicomponent adsorption systems accurately. The main advantage of JAMM isotherm over other multicomponent isotherms is that it utilizes and leverages the single-component adsorption parameters to simulate multicomponent isotherms. The proposed JAMM analytical isotherm model furthermore incorporates the interaction between the components, a mole fraction parameter, and a heterogeneity index, providing a more comprehensive modeling framework for multicomponent adsorption. The mole fraction term was introduced for the distribution of adsorption sites based on the relative number of molecules of each component. An additional term for interaction coefficient was introduced for the representation of interactions. During the validation of JAMM with three experimental case studies with negligible, small, and high competition systems of adsorbates, impressive predictions were exhibited, with the average normalized absolute percentage error as 6.05% and average R2 as 0.86, highlighting the model's robustness, versatility, and reliability. We propose that the new JAMM isotherm modeling framework might profoundly help in chemical engineering, environmental engineering, and materials science applications by providing a potent tool for analyzing and predicting multicomponent adsorption systems.

Pine needle–derived biochar adsorbents for removal of Sm(III) and competitive toxic metals from model aqueous matrices.

Pine needle–derived biochars have been prepared and investigated as adsorbent materials for the removal of trivalent samarium (Sm(III)) from aqueous systems. The biochars, which were previously oxidized and magnetized), have been characterized prior and after Sm(III) adsorption by Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray diffraction (XRD). The effect of various parameters such as metal ion concentration, pH and contact time on the adsorption efficiency has been investigated. In addition, competitive adsorption experiments have been carried out (competition between Sm3+, Cu2+ and UO22+ ions) by means of batch type experiments. The results showed better adsorptive properties for magnetized oxidized pine needle biochar (PNCOM), particularly at pH 6 (qmax = 691.7mg·g-1), while at pH 3 the oxidized biochar (PNCO) (qmax = 285.7mg·g-1) presented the highest adsorption capacity. The experimental data were better fitted by the Langmuir adsorption and pseudo-second order kinetic model. On the other hand, the competitive adsorption studies have shown that generally PNCOM presents remarkably higher affinity for U(VI) than its non-magnetized counterpart (PNCO). However, despite the fact that the sorption capacity is the highest for U(VI), the affinity of the biochar materials for the studied metal ions is higher for Sm(III), followed by U(VI) and Cu(II). This indicates that the net charge of the metal ion is a key parameter regarding the stability of the complexes formed on the oxidized biochar materials prior and after magnetization.

Cryptands on a Solid Support for the Separation of Europium from Gadolinium.

With the great demand for europium in green-energy technologies comes the need for innovative methods to isolate the elements. We introduce a solid-liquid extraction method using a 2.2.2-cryptand-modified solid support to separate europium from gadolinium using their differences in electrochemical potential. The method overcomes challenges associated with the separation of those two ions that have similar coordination chemistry in the +3 oxidation state. A competitive adsorption study in the cryptand system between EuII/EuIII and GdIII shows greater affinity for EuII relative to GdIII. After separation from GdIII, Eu was released by oxidizing EuII to EuIII with 99.3% purity. The purity of separated Eu is unaffected by pH between pH 3.0 and 5.5. Overall, we demonstrate that by modifying a solid support with 2.2.2-cryptand, divalent europium can be separated from trivalent gadolinium based on the differences of affinities of 2.2.2-cryptand for the two ions.

Recovery of binary-component textile wastewater contaminated by reactive dyes through adsorption onto magnetic separable MgO nanoparticles produced from solid waste of ductile cast iron industry, process identifications, characterization and regeneration

A new magnetic separable Mg-based adsorbent was produced from a waste collected from cast ductile iron industry for removing reactive dyes from the industrial textile wastewater. The magnetic coreshells were prepared based on one step gel-combustion approach. Mg2+ ions were extracted from the gray solid waste through the acid leaching. The coreshells were added to the prepared solution under sonication, and then Mg(OH)2 particles were decorated onto magnetic nanoparticles via precipitation followed with calcination at 500 °C. The reusable adsorbent was utilized for the uptake of R Blue 222, and R Red 195 dyes from single, and binary-component effluents. The adsorption studies were conducted at a variety of dye concentrations by adding different dosage of adsorbents. The competitive adsorption studies demonstrated that the capacity for the dye uptake from the binary-component wastewaters is greater than those for single-component systems, promoting the adsorptive performance. With decoration of MgO nanoparticles over the coreshells, the growth of crystallites was limited as identified from XRD patterns. An increase in pore volume, and average pore diameter, ∼ 14 nm, are the main reasons for the promotion of active site numbers which is beneficial to prevent the efficient loss in capacity due to magnetization.

Designing novel perlite-Fe3O4@SiO2@8-HQ-5-SA as a promising magnetic nanoadsorbent for competitive adsorption of multicomponent VOCs

Volatile organic compounds (VOCs), which emerge as multicomponent pollutants through many industrial processes, pose a serious threat to human health and the eco-environment due to their volatility, toxicity and dispersion. Hence, the study of competitive adsorption of multicomponent VOCs is of practical and scientific importance. Herein, the perlite-supported Fe3O4@SiO2@8-hydroxyquinoline-5-sulfonic acid (perlite-Fe3O4@SiO2@8-HQ-5-SA) was designed as a novel magnetic nanoadsorbent by a simple strategy and employed for the competitive adsorption of multicomponent toluene, ethylbenzene and xylene in the vapor-phase targeted as VOCs. The successfully prepared perlite-Fe3O4@SiO2@8-HQ-5-SA was characterized by means of SEM, EDX, FT-IR, VSM and BET analyses. Adsorption capacities of 558 mg/g, 680 mg/g and 716 mg/g were achieved for single component toluene, ethylbenzene and xylene, respectively. It was concluded that the adsorption capacities for both binary and ternary components were significantly decreased compared to single component adsorption. The competitive adsorption capacity order of the binary and ternary component VOCs was xylene > ethylbenzene > toluene due to their competitive dominance. The rate-limiting kinetic analysis indicated that the adsorption rates were determined by both the film diffusion and intraparticle diffusion. The analysis of the error metrics demonstrated that the three-parameter isotherm models better described the adsorption data compared to the two-parameter models. In particular, the Toth model provided the closest fit to the experimental equilibrium data. The thermodynamic analysis indicated the spontaneous nature and probability (ΔG° <0), exothermic (ΔH° <0), physical (ΔH° <20 kJ/mol) and a declination in the degree of randomness (ΔS° <0) of the adsorption processes. The reuse efficiency of perlite-Fe3O4@SiO2@8-HQ-5-SA for toluene, ethylbenzene and xylene decreased to only by 88.91%, 88.07% and 87.16% after five recycles. The perlite-Fe3O4@SiO2@8-HQ-5-SA has a significant adsorptive potential compared to other adsorbents reported in the literature, thus it could be recommended as a promising nanoadsorbent for VOCs in industrial processes.

Studies on competitive adsorption characteristics of bisphenol A and 17α-ethinylestradiol on thermoplastic polyurethane by site energy distribution theory.

Compound pollution of microplastics and estrogens is a growing ecotoxicological problem in aquatic environments. The adsorption isothermal properties of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) on polyamide (TPU) in monosolute and bisolute systems were studied. Under the same adsorption concentration (1-4mg L-1), EE2 had a greater adsorption capacity than BPA in the monsolute system. Compared to the energy distribution features of the adsorption sites of EE2 and BPA, the BPA adsorption sites were located in the higher energy area and were more evenly distributed than those of EE2, while the quantity of BPA adsorption sites was less than that of EE2. In the bisolute system, the average site energy, site energy inhomogeneity, and adsorption site numbers of BPA increased by 1.674, -17.166, and 16.793%, respectively. In comparison, the average site energy, site energy inhomogeneity, and adsorption sites numbers of EE2 increased by 2.267, 4.416, and 8.585%, respectively. The results showed that BPA and EE2 had a cooperative effect on the competitive adsorption of TPU. XPS analysis showed that BPA and EE2 had electron transfer on TPU, although the chemisorption effects and hydrogen bonds between BPA and TPU were more significant. Comparing the changes in the relative functional group content of TPU in monosolute and bisolute systems, BPA and EE2 were synergistically absorbed on TPU. This study can provide a theoretical reference for the study of competitive adsorption between coexisting organic pollutants.

Lignin based microspheres for effective dyes removal: Design, synthesis and adsorption mechanism supported with theoretical study

Multifunctional lignin bio-based adsorbent, b-LMS, was obtained via inverse copolymerization in the suspension of acryloyl modified kraft lignin (KfL-AA) and bio-based trimethylolpropane triacrylate (bio-TMPTA). Morphological and structural characterization of KfL-AA and b-LMS was performed using BET, FTIR, Raman, NMR, TGA, SEM, and XPS techniques. The b-LMS microspheres with 253 ± 42 μm diameters, 69.4 m2 g−1 surface area, and 59% porosity efficiently adsorb Malachite Green (MG), Tartrazine (T), and Methyl Red (MR) dye. The influence of pH, pollutant concentration, temperature, and time on the removal efficiency was studied in a batch mode. Favorable and spontaneous processes with high adsorption capacities e.g. 116.8 mg g−1 for MG, 86.8 mg g−1 for T, and 68.6 mg g−1 for MR indicate the significant adsorptive potential of b-LMS. Results from diffusional and single mass transfer resistance studies indicate that pore diffusion is a rate-limiting step. Theoretical calculations confirmed a higher affinity of b-LMS to cationic dye MG compared with an anionic and neutral one, i.e. T and MR, respectively. The data fitting from a flow system, using semi-empirical equations and Pore Surface Diffusion Modelling (PSDM) provided breakthrough point determination. The results from the desorption and competitive adsorption study proved the exceptional performance of b-LMS. Moreover, sulfation of b-LMS, i.e.production of b-LMS-OSO3H, introduced high-affinity sulfate groups with respect to cationic dye and cations. Developed methodology implements the principle of sustainable development and offers concept whose results contribute to the minimization of environmental pollution.

Efficient extraction of radionuclides with MXenes/persimmon tannin functionalized cellulose nanofibers: Performance and mechanism

A bio-adsorbent (DACNF-MXenes-NH2-PT) was facilely prepared by introducing persimmon tannin (PT) and amino-functionalized MXenes (MXenes-NH2) into dialdehyde cellulose nano-fibres (DACNF) through cross-linking reaction. The advanced spectroscopy techniques confirmed that the bio-adsorbent possessed fibrousstructure, abundant active groups (TiOH, ArOH and NH2) and high chemical stability. Batch experiments showed that water environmental condition played a vital roles in elimination process, and DACNF-MXenes-NH2-PT possessed a high uptake amounts towards U(VI) (105.7 mg/g) and Th(IV) (95.1 mg/g). Meanwhile, the equilibrium studies specified that adsorption data followed the Langmuir and Pseudo-second-order models, which implied that extraction process mainly depended on sharing of electrons between bio-adsorbents and adsorbates. More importantly, the competitive adsorption studies found that DACNF-MXenes-NH2-PT had a selective affinity for U(VI)/Th(IV), while its removalefficiency exhibited slightly decrease after three adsorption–desorption cycles. The characterizationanalysis revealed that the elimination of radionuclides mainly depended on the strong coordination, complexation and the synergetic effect of surface adsorption and intercalation adsorption. Thus, the unique bifunctional ability of DACNF-MXenes-NH2-PT would provide a new way for the treatment of radioactive wastewater in the future.

Enhanced photoactivity and selectivity over BiOI-decorated Bi2WO6 microflower for selective oxidation of benzylamine: Role of BiOI and mechanism

The importance of developing effective and selective photocatalytic materials to realize efficient renewable energy-based organic synthetic processes, such as selective oxidation of benzylamines and its derivatives to the corresponding imines has become more apparent in recent years. Here we present the first reported BiOI/Bi2WO6 (BI/BW) microflower heterostructure as a visible-light-driven photocatalyst for such reactions. By decorating the hydrothermally prepared BW with BI via successive ionic layer adsorption and reaction (SILAR) method, benzylamine conversion is improved from 68 % to 92 % as compared to undecorated. Furthermore, selectivity to desired imine product is substantially increased from 59 % to 95 %. These outstanding performances are attributed to enhanced electron-hole separation and transfer efficiency as well as a greater preference for adsorption of benzylamine compared to the imine products and extended visible-light absorption range inherited from BI component as supported by competitive adsorption studies, ultraviolet–visible diffuse reflectance spectroscopy, and photoelectrochemical experiments. Possible mechanisms, band energy diagram, and decisive roles of O2− and h+ in the selective transformation of benzylamine were proposed based on Mott-Schottky, scavenging, and electron paramagnetic resonance radical trapping experiments. This work highlights a simple approach for improving photocatalytic activity and selectivity which are highly desirable in renewable energy-based chemical synthetic processes.

Insight into adsorptive removal of methylene blue, malachite green, and rhodamine B dyes by cassava peel biochar (Manihot esculenta Crantz) in single, binary, and ternary systems: competitive adsorption study and theoretical calculations

Insight into adsorptive removal of methylene blue, malachite green, and rhodamine B dyes by cassava peel biochar (Manihot esculenta Crantz) in single, binary, and ternary systems: competitive adsorption study and theoretical calculations

Effects of Chelating Surfactants on Competitive Adsorption of Lead and Zinc on Loess Soil

The study of competitive adsorption of heavy metals on soil is important for heavy metals contaminated soil remediation. However, there have been few studies on the impact of desorption reagents on heavy metal adsorption in soil. Batch adsorption studies were used to investigate the competitive adsorption mechanism of two heavy metals, Pb and Zn, on a loess soil in the presence of a new chelating surfactant, sodium N-lauroyl ethylenediamine triacetate (LED3A). Results showed that competitive adsorption equilibria of Pb and Zn were reached at 3 and 10 h, respectively. The maximum equilibrium adsorption capacities were 19.55 and 18.35 g.kg-1, respectively. LED3A affected the competitive adsorption kinetics of Pb and Zn by increasing the change in external mass transfer and reducing the change in internal mass transfer. LED3A reduced Pb and Zn adsorption capacities onto the soil through competitive chelation of the heavy metals. The heavy metal chelating ability of LED3A was higher for Zn than for Pb. When its concentration was larger than 5 g.L-1, LED3A showed a significant effect on the competitive adsorption of Pb and Zn. In the competitive system, the effect of Pb concentration on the Zn adsorption capacity was greater than the effect of Zn concentration on the Pb adsorption capacity. LED3A weakened the effect of Pb concentration and enhanced the effect of Zn concentration. LED3A showed a significant potential for efficiently leaching remediation of Pb and Zn co-contaminated soil.

Understanding competitive adsorption of SF6 and its decomposed components on α-Fe2O3

Airborne mineral dusts make a big contribution to atmospheric particulate matter, and they can provide reactive surfaces to promote heterogeneous reactions. Atmospheric sulfur hexafluoride (SF6) and its decomposed products are unique pollutants, but little is known about the heterogeneous fate of these gas molecules. This paper presents a preliminary study of the competitive adsorption of SF6 and its decomposed components (SF2O2, SF2O, SO2, H2S, HF) on one of the most common atmospheric mineral surfaces (α-Fe2O3). First-principles calculations were carried out to examine the adsorption mechanism of SF6 and its decomposed gases on the α-Fe2O3(0001) surface, and analyzed in terms of the corresponding adsorption energy, geometrical structure, and charge transfer. It is found that these gas molecules are adsorbed on the α-Fe2O3(0001) mineral surface by chemisorption except SF6. By comparing the adsorption parameters of the six gas molecules, it can be inferred that the adsorption strength of the α-Fe2O3(0001) mineral surface to gases is H2S > HF > SO2 > SF2O > SF2O2 >> SF6. Meanwhile, a competitive adsorption study was also carried out in clean air (N2, O2, H2O). The pollutants (SO2, H2S, HF) would be more easily adsorbed on the α-Fe2O3 surface. This study reveals the nature of the first step (adsorption) of the atmospheric heterogenous reaction at the molecular electronic level, and helps to understand the mechanism of pollution.

Preparation of magnetic nanoparticle-cholesterol imprinted polymer using semi-covalent imprinting approach for ultra-effective and highly selective cholesterol adsorption

In the present study, a magnetic nanoparticle-cholesterol imprinted polymer for cholesterol (CHO) adsorption exploring semi-covalent imprinting approach was proposed. The Fe3O4/SiO2/MIP synthesis was carried out by using surface imprinting polymerization technique on the silica-coated magnetite, using 3-(triethoxysilyl)propyl isocyanate (ICPTES) as functional monomer and CHO as template, where occurs a covalent bond between them, and TEOS as a cross-linking reagent. The Fe3O4/SiO2/MIP material was characterized by X-ray diffractometry (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray fluorescence (XRF), values of specific surface area, pore size, and pore volume through nitrogen adsorption/desorption isotherms and vibrating sample magnetometry (VSM). The surface area of Fe3O4/SiO2/MIP (151.04 m2 g−1) was significantly higher compared to Fe3O4/SiO2/NIP (66.09 m2 g−1) and based on relative selectivity coefficient (k´), Fe3O4/SiO2/MIP showed higher selectivity towards CHO in competitive adsorption studies CHO/5-α-cholestane, CHO/7-dehydrocholesterol and CHO/estradiol in chloroform. From the kinetic study, the adsorption equilibrium for Fe3O4/SiO2/MIP was quickly achieved at 60 s in a vortex mixer and described by the second-order kinetic model. High adsorption capacity for Fe3O4/SiO2/MIP (314.1 mg g−1) was obtained from the isotherm studies, and it was adjusted to dual-site Langmuir–Freundlich isotherm model. The obtained outcomes in terms of selectivity, maximum adsorption capacity, and fast kinetic make the magnetic nanoparticle-cholesterol imprinted polymer an outstanding material for future application in magnetic dispersive solid-phase extraction for analytical purposes.

Preparation of Pomelo Peel-Based Biomass Carbon Aerogel-MnO2 Composite Electrode and its Adsorption Performance of Rb+ and Cs+

Electrosorption can be used for both desalination of seawater and high value element ions enrichment, which has attracted more and more attentions because of its merits of low energy consumption, no pollution and inexpensive. The research focuses on the preparation of novel electrodes and selective electrosorption properties. In this paper, biomass carbon aerogel was prepared by hydrothermal-freeze drying- carbonization method using pomelo peel as raw material. A composite electrosorption electrode was obtained using pomelo peel-based carbon aerogel (PCA) as main component. The surface morphology, crystal structure, specific surface area and functional groups were characterized by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Brunauer Emmett Teller (BET) and Fourier Transform Infrared Spectroscopy (FTIR). Then the effects of coexisted alkali/alkaline earth metal ions on the adsorption of Rb+ and Cs+ were studied. The pomelo peel-based carbon aerogel-manganese dioxide (PCA-MnO2) composite electrode shows good adsorption performance on Rb+ and Cs+. When alkali and alkaline earth metal ions coexist, PCA-MnO2 composite electrode exhibits the highest adsorption selectivity of Mg2+. The research content in this work broadens the source of electrosorption electrode and provides a reference for the study of competitive adsorption of alkali/alkaline earth metal ions.

The removal of Cu(II) and Pb(II) ions from aqueous solutions by temperature-sensitive hydrogels based on N-isopropylacrylamide and itaconic acid

This study deals with the potential use of poly(N-isopropylacrylamide-co-itaconic acid) temperature-sensitive hydrogels as an adsorbent for the removal of Cu(II) and Pb(II) ions from aqueous solutions. For this aim, the adsorption properties of hydrogels were examined by adsorption capacities, adsorption isotherm, and adsorption kinetics experiments. To describe the adsorption characteristics of hydrogels, the obtained experimental data were evaluated by Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich isotherm models. Adsorption kinetics experiments were carried out not only in single systems but also in binary systems where both ions were at equal initial concentrations for competitive adsorption studies. To predict the behaviors of the competitive and non-competitive adsorption process of ions onto hydrogels, the experimental adsorption data were analyzed by the pseudo-first-order model and the pseudo-second-order model. According to non-competitive ion removal findings, the adsorption capacities followed order Cu(II) &gt; Pb(II) for all hydrogels, and the pseudo-second-order kinetic model explained the adsorption properties of the hydrogels. Competitive ion removal studies showed that all hydrogels were selective to Cu(II) ion. Furthermore, in the case of comparative investigations both of competitive Cu(II) and competitive Pb(II) removal by hydrogels, the metal ion removal capacity of N10 hydrogel was found as a bit higher than that of N7.5 and N5 in 48 h. That is, as the acidic group content increased in the hydrogel network, the adsorption capacity values also increased. In addition, the reusability of temperature-sensitive hydrogels seems possible without regeneration or after regenerating with acid, in case the temperature is increased above the LCST. Furthermore, even if it cannot be reused, these hydrogels that retain metal ions reach very small volumes by shrinking when the LSCT is exceeded, and thus they can be eliminated more easily than other conventional gels due to their small size. As a result, this temperature-sensitive hydrogel may propose as an alternative environmentally friendly adsorbent candidate for can be used for water purification and wastewater treatment.

Chitosan Versus Chitosan-Vanillin Modified: An Evaluation of the Competitive Adsorption of Five Emerging Contaminants

Emerging contaminants (ECs) have been studied extensively because of the various damages they can cause to the environment, especially due to the non-treated domestic effluents, which contaminate the water bodies. Therefore, it is important to evaluate alternatives to remove these compounds. The objective of this work was to evaluate the potential of a new biosorbent from chitosan modified with vanillin (CTSV) to remove isoniazid, cortisol, bisphenol A, 17α-ethinylestradiol, and triclosan by competitive adsorption studies. Structural characterization of the biosorbents was performed by Fourier transform infrared spectroscopy, thermogravimetry, Brunauer-Emmett-Teller, zeta potential, scanning electron microscopy, and 1H nuclear magnetic resonance. The adsorption for ECs were carried out in an aqueous medium, and quantitative analyzes were performed by HPLC. The effect of pH was evaluated in the pH range 5 to 10 and indicated that better results were found in pH 9 and 8 for CTS and CTSV, respectively. The salt concentrations effect was evaluated in 0.0 to 1.0 mol L−1 and revealed better adsorption conditions in 0.7 mol L−1 of NaCl. The adsorption kinetics pointed to an equilibrium condition reached quickly (with adjustment of data R2 > 0.969) with adequacy to pseudo–second-order model for both biosorbents and ECs. The linear isothermal model was suitable for the adsorption isothermal data and distribution constant (KD) showed the highest values for 17α-ethinylestradiol (0.067 L g−1) and triclosan (0.197 L g−1) in CTSV adsorption. Thus, the results indicated that CTSV performed well in removal for the tested ECs, being an interesting alternative, due to the ease of obtaining and abundance of reagents employed in its preparation.

Utilisation of Biomass and Hybrid Biochar from Elephant Grass and Low Density Polyethylene for the Competitive Adsorption of Pb(II), Cu(II), Fe(II) and Zn(II) from Aqueous Media

Background: There are different types of pollutants in water hence they are constantly in competition for active sites during the adsorption process. A key advantage of competitive adsorption studies is that these inform regarding the adsorbent’s performance in real water treatment applications. Objective: This study aims to investigate the competitive adsorption of Pb(II), Cu(II), Fe(II) and Zn(II) using elephant grass (Pennisetum purpureum) biochar and hybrid biochar from LDPE. Method: The produced biochar was characterised by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The adsorption parameters, equilibrium isotherm modelling and parametric studies were conducted based on data from the batch adsorption experiments. Results: For both adsorbents, the removal efficiency was &gt;99% over the entire investigation for dosage and contact time, suggesting that they are very efficient for removing multiple heavy metals from aqueous media. It was observed that removal efficiency was optimal at 2 g/l dosage and contact time was 20 minutes for both adsorbent types. The Elovich isotherm and the pseudo-second order kinetic models were best-fit for the competitive adsorption process. Conclusion: The study was able to successfully reveal that biomass biochar from elephant grass and hybrid biochar from LDPE can be used as effective adsorbent material for the removal of heavy metals from aqueous media. This study bears a positive implication for environmental protection and solid waste management.