Monomolecular Layer Adsorption Research Articles

A green and low-cost preparation of polyacrylonitrile fibers with imine dioxime and amidoxime groups for efficient and selective gold recovery

The preparation of adsorbents with low cost, efficient adsorption and high profitability for gold recovery has important practical applications. In this work, synergistic poly (imine dioxime and amidoxime) (PDA) adsorbents were successfully prepared for gold recovery. An inexpensive engineering polyacrylonitrile (PAN) fiber is selected as the adsorbent substrate covalent binding with hydroxylamine hydrochloride to obtain PDA. The PDA surface with imine dioxime and amidoxime groups has a rich charge density and is more easily combined with gold ions through electrostatic interactions. The adsorption process of gold on PDA is a spontaneous endothermic process with monomolecular layer adsorption and the adsorption capacity increases with the increasing temperature under acidic conditions. The maximum adsorption capacity of PDA can reach 2937 mg g−1 at 25 °C and pH = 2 with an equilibrium time of 168 h. Meanwhile, excellent gold adsorption performance is also observed for PDA in simulated water treatment filler and water circulation reactor as well as interference conditions with other metal ions. Surprisingly, PDA has an ultra-low preparation cost ($ 2.54 × 102 kg−1), yet enables high-value gold (2.9 kg) for every kilogram of PDA with significant economic benefits. Therefore, this work will provide new ideas for the development of inexpensive, highly efficient, and specialized adsorbent preparation for gold recovery.

Ultra-cheap and ultra-stable adsorption materials based on nylon and removal performance of copper ion

A novel adsorbent material, nylon@Fe3O4, was prepared by co-precipitation of nylon and FeSO4/FeCl3/NaOH solution. The structure of the composite was characterized using FTIR and TG methods. The results of FTIR and TG indicated that nylon@Fe3O4 was successfully synthesized. The adsorption effect of nylon@Fe3O4 on Cu(II) was explored under different experimental conditions. The optimum adsorption conditions of nylon@Fe3O4 on Cu(II) were reached when the amount of composite was 12.50 mg, the concentration of Cu(II) was 15.36 mg/L, the reaction temperature was 50 °C, and the pH value was 9. Under the above conditions, the optimum adsorption efficiency was 94.67 % and the optimum adsorption capacity was 11.57 mg/g. The kinetic modeling indicated that the adsorption of nylon@Fe3O4 belonged to chemisorption, and the initial adsorption rate (h = 69.92 mg/g/min) was larger, which indicated that the nylon@Fe3O4 adsorption rate was faster. The adsorption isotherm experiments showed that the nylon@Fe3O4 adsorption process occurred in the monomolecular layer adsorption, and the separation coefficients 0 < RL = 0.322/0.300/0.287 < 1, which indicated that the adsorption process of nylon@Fe3O4 for Cu(II) was favorable adsorption. The adsorption thermodynamics showed that ΔG0 < 0, ΔS0 = 118 J/mol/K > 0, and ΔH0 = 31.14 kJ/mol > 0, indicating that the adsorption process of nylon@Fe3O4 on Cu(II) was spontaneous and favorable adsorption. Through 8 cycle experiments, the adsorption efficiency decreased from 94.67 % to 61.55 %, so nylon@Fe3O4 had good regenerative performance. In conclusion, nylon@Fe3O4 has potential applications in the adsorption of heavy metal ions.

A method for the efficient removal of Pb(II) by D001 resin in a rotating packed bed

The treatment of Pb(II) is a challenging problem. In this study, a new approach for removal of Pb(II) using D001 resin in a rotating packed bed (RPB) is proposed, and the adsorption behaviors and mechanisms are investigated. The results reveal that under optimal conditions (initial Pb(II) concentration c0 = 100 mg L−1, high-gravity factor β = 36.33, liquid flow rate QL = 60 L h−1, initial solution pH = 5.0, and temperature T = 303 K), the removal rate of Pb(II) in RPB is 95.54 % at 120 min, which is 12.18 % and 9.81 % higher than that in thermostatic shaker (TS) and stirred tank reactor (STR). The adsorption of Pb(II) by D001 resin can be well described by the Langmuir adsorption isotherm and the adsorption heat is 13.24 kJ mol−1, and it is a typical monomolecular layer adsorption. It is also found that the adsorption mechanism of Pb(II) by D001 resin in RPB follows the pseudo-first-order kinetics, and the rate constant k1 is 1.72 and 1.64 times that in TS and STR. The R-SO3Na is the dominant group and Na+ undergoes ion exchange with Pb (II) on the surface of D001 resin. This study provides a new method for the treatment of Pb(II).

Effect of Modified Biochar Prepared by Co-pyrolysis of MgO on Phosphate Adsorption Performance and Seed Germination.

Biochar is currently used as a phosphate adsorbent in water and subsequently as a soil amendment. In this study, modified biochar was prepared directly by co-pyrolysis of MgO and rice straw, and a preliminary ecotoxicological assessment was performed before the application of modified biochar to soil. The effects of single factors, such as pyrolysis temperature, dosage, pH, and coexisting ions, on phosphate adsorption performance were investigated. In addition, after phosphate adsorption, the effects of modified biochar leachate on the germination of corn and rice seeds were examined. The results showed that phosphate adsorption by the modified biochar first increased and then decreased as the pyrolysis temperature increased, with modified biochar prepared at 800 °C showing the greatest adsorption. In addition, a comprehensive cost analysis showed that the best phosphate adsorption effect of modified biochar was achieved at a dosage of 0.10 g and a solution pH of 3. In contrast, the presence of competitive coexisting ions, Cl- , NO3 - , CO3 2- , and SO4 2- , reduced the phosphate adsorption capacity of the modified biochar. The adsorption kinetics results revealed that the process of phosphate adsorption by the modified biochar was more in line with the pseudo-second-order model and dominated by chemisorption. Moreover, the adsorption isotherm results indicated that the process was more in line with the Langmuir model and dominated by monomolecular layer adsorption, with a maximum adsorption of 217.54 mg/g. Subsequent seed germination tests showed that phosphate-adsorbed modified biochar leachate had no significant effect on the germination rate of corn seeds, whereas it improved the germination rate of rice seeds. Together, these results provide guidance for the application of modified biochar firstly as an adsorbent of phosphate and subsequently as a soil remediator.

Modeling of Supercritical CO2 Adsorption for Low-Permeability Coal Seam of Huainan-Huaibei Coalfield, China.

Investigating the coal adsorption behavior on supercritical CO2 (ScCO2) is crucial for long-term CO2 geological storage. In this paper, low-permeability coal samples from the Huainan-Huaibei coalfields in China were selected. The high-pressure isothermal adsorption of CO2 was carried out at 36, 42, and 48 °C. The results of adsorption experiments were analyzed by fitting 9 types of modified adsorption models, including three different adsorption theories. Considering that different adsorption mechanisms may exist for CO2 in coal, 14 mixed adsorption models were established. The accuracy of the coefficient of determination (R2) and root-mean-square error (RMSE) for ScCO2 excess adsorption capacity was analyzed, mainly focusing on the accuracy of the key model parameters such as the adsorption phase density and the theoretical adsorption capacity. These parameters were discussed, combined with the predicted adsorption phase density of CO2 based on the intercept method. The results indicate that among the 9 types of modified adsorption considered, based on the adsorption phase density screening, the deviation of the predicted adsorption capacity from the experimental value was then considered. The Dubinin-Radushkevich (DR) model can effectively fit the adsorption behavior of CO2 at low pressure (<7.5 MPa). The Langmuir (L), Langmuir-Freundlich (LF), Extended-Langmuir (EL), and TOTH models can effectively fit the adsorption behavior of CO2 at high pressure (7.5-20 MPa), while the multimolecular layer models were unsuitable for fitting ScCO2 adsorption. The model fitting results showed that only the monomolecular layer and micropore-filled adsorption models were suitable for fitting the ScCO2 adsorption capacity. The DR-LF model best fits the adsorption data based on its key parameters of adsorption phase density and theoretical adsorption capacity. The established mixed model DR-LF fitting results showed that the CO2 in coal was dominated by microporous filling adsorption. The higher the temperature, the greater the contribution of microporous filling adsorption to the total adsorption. There still exists deviation in the adsorption phase density and theoretical adsorption capacity. The contribution percentage of different adsorption mechanisms of CO2 in coal needs to be further investigated.

Fabrication of boronic acid-functionalized covalent organic framework for the selective adsorption of cis-diol-containing compounds

In this work, we report a post-synthetic modification strategy to synthesize a boronic acid-functionalized porphyrin-based covalent organic framework (denoted as BA-COF) via the Suzuki-Miyaura cross-coupling reaction. Interestingly, BA-COF exhibits excellent selectivity in adsorbing cis-diol-containing compounds (CDC). The selective adsorption mechanism was addressed in detail, which is probably due to the boronate affinity from boronic acid group, hydrophilic interaction from the nitrogen-rich framework as well as “host–guest” interaction from the unique “trap” structure of porphyrin-based COF. The characterized results demonstrated its uniform morphology, large specific surface area, and excellent thermal stability. The adsorption kinetics demonstrated that the adenosine adsorption onto BA-COF conformed to the pseudo-second-order kinetic model and belonged to chemisorption. Based on the fitting of adsorption isotherms and thermodynamic analysis, the adenosine adsorption onto BA-COF was monomolecular layer adsorption and was a spontaneous endothermic reaction. Moreover, the reuse performance of BA-COF was investigated through consecutive adsorption–desorption cycle experiments. This work also demonstrates the potential of BA-COF for effective and selective adsorption of CDC in real sample.

Surface Structure Analysis and Formaldehyde Removal Mechanism of Lotus Shell Biochar: An Experimental and Theoretical Perspective.

The adsorption of gaseous HCHO by raw lotus shell biochar carbonized at 500, 700, and 900 °C from the perspective of its internal crystal structure and surface functional groups was investigated by an integrated approach of experiments and density functional theory calculations. The results showed that lotus shell biochar carbonized at 700 °C had the best adsorption effect at a HCHO concentration of 10.50 ± 0.30 mg/m3, with an adsorption removal rate of 87.64%. The HCHO removal efficiency by lotus shell biochar carbonized at 500 and 900 °C was determined to be 80.96 and 83.07%, respectively. The HCHO adsorption on lotus shell biochar carbonized at 700 °C conformed to pseudo-second-order kinetics and was predominantly controlled by chemical adsorption. The Langmuir isotherm was the underlying mechanism for the monomolecular layer adsorption with a maximum adsorption capacity of 0.329 mg/g. The density functional theory calculations revealed that the adsorption of HCHO on the surface of CaCO3 and KCl in lotus shell biochar carbonized at 700 °C was a chemical adsorption process, with adsorption energies ranging from -64.375 to -87.554 kJ/mol. The strong interaction between HCHO and the surface was attributed to the electron transfer from HCHO to the surface, facilitated by metal atoms (Ca or K) and the oxygen atoms of HCHO. The carboxyl group on the surface of lotus shell biochar carbonized at 700 °C was identified as the key functional group responsible for HCHO adsorption. This study advanced our understanding of the environmental functions of inorganic crystals and surface functional groups in raw biochar and will enable the further development of biochar materials in environmental applications.

Adsorption and catalytic degradation of bisphenol A and p-chlorophenol by magnetic carbon nanotubes

Phenolic compounds are common industrial pollutants that seriously endangers water ecology and human health. Therefore, the development of efficient and recyclable adsorbents is of importance for wastewater treatment. In this research, HCNTs/Fe3O4 composites were constructed using co-precipitation way by loading magnetic Fe3O4 particles onto hydroxylated multi-walled carbon nanotubes (MWCNTs), showing excellent adsorption capacity for Bisphenol A (BPA) and p-chlorophenol (p-CP), and excellent catalytic ability of activating potassium persulphate (KPS) for degradation of BPA and p-CP. The adsorption capacity and catalytic degradation potential were evaluated for the removal of BPA and p-CP from solutions. The results showed that the adsorption took only 1 h to reach equilibrium and HCNTs/Fe3O4 had maximum adsorption capacities of 113 mg g−1 for BPA and 41.6 mg g−1 for p-CP at 303 K, respectively. The adsorption of BPA fitted well using the Langmuir, Temkin and Freundlich models while the adsorption of p-CP fitted well using the Freundlich and Temkin models. BPA adsorption on HCNTs/Fe3O4 was dominated by π-π stacking and hydrogen bonding forces. The adsorption included both the mono-molecular layer adsorption on the adsorbent surface and the multi-molecular layer adsorption on the non-uniform surface. The adsorption of p-CP on HCNTs/Fe3O4 was a multi-molecular layer adsorption on a dissimilar surface. The adsorption was controlled by forces such as π-π stacking, hydrogen bonding, partition effect and molecular sieve effect. Moreover, KPS was added to the adsorption system to initiate a heterogeneous Fenton-like catalytic degradation. Over a wide pH range (4–10), 90% of the aqueous BPA solution and 88% of the p-CP solution were degraded in 3 and 2 h, respectively. After three adsorption-regeneration or degradation cycles, the removal of BPA and p-CP remained up to 88% and 66%, indicating that HCNTs/Fe3O4 composite is cost-effective, stable and highly efficient to remove BPA and p-CP from solution.

Green synthesis of 2-hydroxypropyl-β-cyclodextrin polymers crosslinked by citric acid for highly efficient removal of methylene blue

Herein, a new type of citric-acid-crosslinked 2-hydroxypropyl-β-cyclodextrin (HPCD-CA) adsorbents were synthesized, and their applications to the removal of the cationic dye—methylene blue (MB) from the water were thoroughly investigated. The HPCD-CA materials were fully characterized and analyzed by SEM, FT-IR, XRD, TGA, BET and XPS. Influence factors affecting the adsorption efficiency of the HPCD-CA materials were investigated separately, including contact time, adsorbent dosage, the concentration of MB, initial pH of the solution, and temperature. The Langmuir adsorption isotherm and pseudo-second-order kinetic model performed better, indicating that the adsorption process is more consistent with chemisorption and monomolecular layer adsorption. The maximum theoretical absorption capacity of HPCD-CA-0.25 for MB was 497.72 mg g−1, much better than most of the previously reported materials. After four adsorption-desorption cycles, HPCD-CA-0.25 maintained a high removal efficiency of MB with good recoverability and stability. In addition, FT-IR and XPS analyses showed that electrostatic interaction, host-guest and hydrogen bonding interactions existed between HPCD-CA-0.25 and MB. Density functional theory (DFT) calculations further verified the above adsorption mechanism, indicating that the synergistic interaction between CA and HPCD enhanced the removal ability of MB by HPCD-CA-0.25. We believe that the current study here provides a feasible way to design wastewater treatment purification materials.

Functional Bimetal/Carbon Composites Co/Zr@AC for Pesticide Atrazine Removal from Water

Atrazine is a toxic and refractory herbicide that poses threats to human health and the ecological environment. In order to efficiently remove atrazine from water, a novel material, Co/Zr@AC, was developed. This novel material is prepared by loading two metal elements, cobalt and zirconium, onto activated carbon (AC) through solution impregnation and high-temperature calcination. The morphology and structure of the modified material were characterized, and its ability to remove atrazine was evaluated. The results showed that Co/Zr@AC had a large specific surface area and formed new adsorption functional groups when the mass fraction ratio of Co2+:Zr4+ in the impregnating solution was 1:2, the immersion time was 5.0 h, the calcination temperature was 500 °C, and the calcination time was 4.0 h. During the adsorption experiment on 10 mg/L atrazine, the maximum adsorption capacity of Co/Zr@AC was shown to be 112.75 mg/g and the maximum removal rate was shown to be 97.5% after 90 min of the reaction at a solution pH of 4.0, temperature of 25 °C, and Co/Zr@AC concentration of 60.0 mg/L. In the kinetic study, the adsorption followed the pseudo-second-order kinetic model (R2 = 0.999). The fitting effects of Langmuir and Freundlich isotherms were excellent, indicating that the process of Co/Zr@AC adsorbing atrazine also conformed to two isotherm models, so the adsorption of atrazine by Co/Zr@AC had multiple effects including chemical adsorption, mono-molecular layer adsorption, and multi-molecular layer adsorption. After five experimental cycles, the atrazine removal rate was 93.9%, indicating that Co/Zr@AC is stable in water and is an excellent novel material that can be used repeatedly.

Schiff base functionalized silica aerogels for enhanced removal of Pb (II) and Cu (II): Performances, DFT calculations and LCA analysis

Schiff base silica aerogels (SCA-X) were synthesized using amino-containing organosilanes and salicylic aldehyde as functional monomers with ethyl orthosilicate hydrolysis condensation as carrier. The influence of SCA-X on the adsorption of Pb (II) and Cu (II) under different adsorption conditions was evaluated, including the effect of solution pH, isotherm, kinetics, thermodynamics and adsorption mechanism. The batch adsorption experiments showed that SCA2 had the optimum adsorption capacity for Pb (II) (357.1 mg/g) and Cu (II) (243.9 mg/g), leading to adsorption equilibrium within 120 min and 360 min, respectively. After six adsorption–desorption cycles, SCA2 still possessed satisfactory adsorption for Pb (II) and Cu (II), demonstrating the reusability of the SCA2 adsorbent material. Kinetic studies indicated that the adsorption process could be described by a pseudo-second-order kinetic model, adsorption isotherms were in accordance with the Langmuir model, indicative of monomolecular layer adsorption. Thermodynamics evaluation revealed the nature of the adsorption process was an endothermic spontaneous process. XPS analysis combined with DFT calculations confirmed that the interaction mechanism between SCA2 and Pb (II) occurred through the coordination between the nitrogen atom donor in the Schiff base and the oxygen atom donor in the benzene ring, while the interaction between SCA2 and Cu (II) occurred mainly through the coordination between the nitrogen atom in the Schiff base and Cu (II). Life Cycle Assessment (LCA) was introduced to analyze the environmental impact of the SCA2 fabrication process and eco-friendly approaches were provided, which eventually provided theoretical evidence for the application of as-prepared material in the handling of heavy metal effluents.

A novel bidisperse diffusion model for coal particles considering micropores as the major sites of CH4 adsorption

Pores in coal have the characteristic of double peaks, and the bidisperse diffusion model is an effective method to describe the diffusion behavior in coal. At present, the traditional bidisperse diffusion models can be divided into “independent” mode and “dependent” mode, which have three main deficiencies as follows. Firstly, since the percentage of adsorbed CH4 in micropores or macropores cannot be accurately determined, the bidisperse diffusion model consists of two equations with three unknown parameters. It is impossible to get a unique solution only based on satisfying a high R2, which brings uncertainty to the solution of the model. Secondly, the ratio of macropore adsorption mass to the total adsorption mass β in some cases shows that CH4 is mainly stored in macropores, which is inconsistent with the physical phenomenon. Thirdly, the independent model is based on the assumption that the macropore diffusion and micropore diffusion are separate from each other, which is not consistent with the pore structure characteristics of coal. To solve the above problems, we put forward a novel two-stage diffusion mode via insightful analysis of the CH4 adsorption form, and the newly-established bidisperse diffusion model can better describe the CH4 diffusion behavior in coal. By using the novel model to analysis the CH4 diffusion behavior, we obtained the following results: (1) The CH4 adsorption form presents the characteristics of micropore filling and a monomolecular layer adsorption. Micropores are the main sites of CH4 adsorption. This adsorption form makes the desorption and diffusion resistance of CH4 vary in different pores, which leads to the CH4 source dynamic evolution during diffusion. (2) The novel model has been proved by experimental validation to have good applicability and can accurately describe the whole process of CH4 diffusion. Meanwhile, the obtained parameters by the new model not only with clear physical significance but also can explain the adsorption-diffusion mechanism of CH4 in multi-scale pores. (3) The traditional dependent model may degenerate into the unipore diffusion model under the condition of satisfying the CH4 occurrence characteristics and fitting accuracy, which results in losing the physical significance of the bidisperse diffusion model.

Simultaneous Fe(OH)3 formation and silicon adsorption removal from reverse osmosis brine wastewater

The reduce of the silicon concentration to low level (<5 mg·L−1) from the reverse osmosis brine wastewater is challenging and desirable for the maintain the membrane life and performance, as well as the wastewater treatment costs. This work focuses on the removal of silicon from the reverse osmosis brine wastewater by adding FeCl3 into the plant wastewater for simultaneous Fe(OH)3 formation and silicon adsorption. The effects of pH, FeCl3 dosing concentration, reaction time, and temperature on the silicon removal ratio were investigated. It was demonstrated that the silicon removal ratio could reach up to 94% and its residual concentration was 3.2 mg·L−1, which met the require of water quality in the reverse osmosis system. These results showed that Fe(OH)3 could effectively be formed by adding FeCl3 and realize the efficient silicon removal from the reverse osmosis brine wastewater, even when chloride ion (Cl-), sulfate anion (SO42-) and nitrate ion (NO3-) were present. Moreover, the adsorption thermodynamics, kinetics and isotherms during the process of the adsorption of silicon from the wastewater by Fe(OH)3 were studied. The calculated adsorption capacity of silicon could reach 612.74 mg·g−1, which was much larger than those of reported adsorbents. These results showed that the silicon removal process was spontaneously exothermic and mainly controlled by the physical adsorption and the monomolecular layer adsorption. This simple and cost-effective method could be used for the silicon removal from different kinds of Si-containing wastewater.

Molecular Simulation Analysis of Methane Adsorption Micromechanisms and the Impact of Water Saturation on Methane Adsorption in Transitional Shale

Abstract Adsorption of gas is one of the ways that shale gas exists in the transitional shale (TS). The adsorption mechanism and the impact of water saturation on methane adsorption affect the estimated accuracy of the gas in place (GIP). This work constructs a TS molecular model comprising type III kerogen, kaolinite, illite, and quartz by using the molecular simulation (MS) according to the physical properties of the TS components. This is verified by the gas adsorption experiments of the TS and its components. The study establishes the methane adsorption model on the TS surface, the impact of the TS with varying water saturation on methane adsorption, and microscopic mechanisms of the TS methane adsorption. The experimental and simulated results show that it is feasible to construct a TS molecular model based on TS’s realistic porosity and density. Methane molecules in different mineral components of the TS are not characterized by monomolecular layer adsorption, mainly including micropore filling, transitional phase adsorption, and monomolecular layer adsorption. The transitional phase layer includes the strong adsorption layer (SAL), adsorption layer trough (ALT), and weak adsorption layer (WAL). Micropore filling and transitional phase adsorption coexist in the kerogen of the TS, and transitional phase adsorption primarily occurs in the illite of the TS. Kaolinite and quartz of the TS are featured with monomolecular layer adsorption. Moreover, quartz does not increase the pore space under high pressure because of stable silicon-oxygen chemical bonds. The chemical bonds in the kerogen and clay of the TS are relatively plastic, yielding the larger pore space under high pressure. Moreover, when water saturation exceeds 30% in the TS, water molecules cover the TS pore surface, affording the minimal methane adsorption capacity (MAC). In short, the micromechanisms of methane adsorption are determined by the TOC, adsorption model, water saturation, pressure, and isosteric heat of the TS components. The TS model can improve the accuracy of methane adsorption simulation and better understand the micromechanisms of methane adsorption. The establishment of the TS model and the impact of water saturation on methane adsorption also improves the estimated accuracy of the GIP.

Type I Collagen Adsorption Behavior on the Control and Modified Surface of Polylactide Coating

Knowledge of the bio-macromolecules adsorption on polylactide (PLA) was essential to the application of PLA-based biomedical materials. This study presented the adsorption behavior of type I collagen on control (CH3-enriched) and modified (introduced COOH– and CONH2– respectively) PLA surfaces by quartz crystal microbalance with energy dissipation measurements (QCM-D) and atomic force microscopy (AFM). The results showed that the Langmuir adsorption isotherms were obtained, indicating a monomolecular layer adsorption of collagen on PLA coatings. Adsorption of collagen could reach equilibrium more quickly on the modified surfaces than on the control. Large amounts of collagen (1522.2 ng·cm−2) was assembled tightly on the COOH-enriched surface of PLA, owing to the electrostatic attracting. However it was inhibited on the CONH2-enriched surface because of its increasing hydrophilicity. A netlike structure was formed on the control and COOH-enriched surfaces, while only a few of braching fibril was found on the CONH2-enriched surface. The behaviour of protein adsorption on the surfaces with different groups might effect the next stage of cell adhesion on scaffold.

Ethylenediamine and Pentaethylene Hexamine Modified Bamboo Sawdust by Radiation Grafting and Their Adsorption Behavior for Phosphate

Phosphate is an important component for the growth of plants and microorganisms; however, excess phosphate causes serious eutrophication in natural waters. New potential low-loss adsorbents from natural biomass for phosphate removal are desired. Bamboo is one of the most abundant renewable cellulose resources; however, the pure bamboo cellulose is poor to adsorb phosphate. To enhance the adsorption capacity, in this work, bamboo sawdust (BS) was chemically modified by two kinds of amines. First, glycidyl methacrylate (GMA) was grafted on BS using radiation induced graft polymerization. Then, the GMA-grafted BS was further modified by a ring-opening reaction with amines, including ethylenediamine (EDA) and pentaethylene hexamine (PEHA). The amine groups were then quaternized to prepare the BS-GMA-EDA-Q and BS-GMA-PEHA-Q adsorbents. The adsorbents were characterized by FTIR, SEM, TG, and XPS analysis. The adsorption performances of the adsorbents for phosphate were evaluated through batch experiments. The adsorption by BS-GMA-EDA-Q and BS-GMA-PEHA-Q both well obeyed the pseudo-second-order kinetic model and the Langmuir isotherm model, indicating that the adsorption process was chemical monomolecular layer adsorption. The maximum adsorption capacities for BS-GMA-EDA-Q and BS-GMA-PEHA-Q calculated by the Langmuir model were 85.25 and 152.21 mg/g, respectively. A total of 1 mol/L HCl was used to elute the saturated adsorbents. A negligible decrease in adsorption capacity was found after five adsorption–desorption cycles.

Adsorption Performances and Electrochemical Properties of Methyl Blue onto CoFe₂O₄ Nanoparticles.

Magnetic CoFe₂O₄ nanoparticles were successfully manufactured through the process of nitrate combustion using anhydrous ethanol as fuel, they together with their intermediate were characterized by thermo gravimetric (TG) analysis, selected area electron diffraction (SAED), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), and X-ray diffraction (XRD). These results indicated a phenomenon that the magnetic CoFe₂O₄ nanoparticles could be formed at 400 °C, the average grain size, the specific magnetization, and the specific surface area of magnetic CoFe₂O₄ nanoparticles fabricated at 400 °C for 2 h with 30 mL anhydrous ethanol were corresponding 20 nm, 78.0 Am²/kg and 83.2 m²/kg. Magnetic CoFe₂O₄ nanoparticles were in application to adsorb methyl blue (MB) of wastewater, and their adsorption performances and electrochemical properties were investigated, the adsorption process data well agreed with the pseudo-second-order kinetics model in concentration ranging from 100 mg/L to 400 mg/L of MB. Compared with Freundlich model, Langmuir model (correlation coefficient R² = 0.9976) could evaluate the adsorption equilibrium state of MB onto CoFe₂O₄ nanoparticles at indoor temperature, so the monomolecular layer adsorption mechanism was demonstrated to be the mechanism of the MB molecules' adsorption onto CoFe₂O₄ nanoparticles.

Removal of Zn2+ from polyethylene terephthalate (PET) glycolytic monomers by sulfonic acid cation exchange resin

Glycolysis of polyethylene terephthalate (PET) has always been a research hotspot in PET waste recovery due to its high efficiency and sustainability. Zinc acetate (ZnAc2•2H2O) and urea/(ZnAc2•2H2O) are usually regarded as the most promising catalysts for the glycolysis of PET, while the residue of Zn2+ in glycolytic monomers (bis(hydroxyalkyl) terephthalate (BHET)) was identified as a big hassle, which caused the detrimental effect on the chromaticity of down-stream product. However, the removal of Zn2+ from BHET has almost not been reported previously. In the present work, ion exchange was adopted as effective measure to eliminate trace Zn2+ from BHET and more than 99% of Zn2+ can be removed by 001*7 sulfonic acid resin with resin dosage of 1.6 g/L at 298.15 K, 160 rpm for 120 min. Additionally, based on prevailing adsorption kinetics, isotherms, thermodynamic models and various precise instruments, comprehensive adsorption mechanism were exploited. Pseudo-second-order model (R2 > 0.999) and Langmuir model (R2 > 0.999) were found to match well with the experimental data, indicating the sorption of Zn2+ on 001*7 was homogeneous monomolecular layer adsorption and dominated by chemisorption. The thermodynamic model revealed the sorption was thermodynamically spontaneous. Fourier-Transform Infrared Spectroscopy (FTIR) illuminated the sulfonic acid groups on 001*7 resin were the main binding sites for Zn2+. X-ray Photoelectron Spectroscopy (XPS) elucidated ion exchange and electrostatic interaction between the sulfonic acid groups and Zn2+ were responsible for the sorption of Zn2+. All the results obtained can prove 001*7 sulfonic acid resin is an efficient material for removal of Zn2+ from BHET.

Effect of Electric Potential and Chain Length on Tribological Performances of Ionic Liquids as Additives for Aqueous Systems and Molecular Dynamics Simulations.

As pure lubricants, ILs performed very well by forming the classical self-assembly bilayer at the sliding interface. The interface mechanism is still not clear in a very polar, e.g., water-based lubricating system. In this work, the interfacial absorption and tribological behavior of carboxylic alkanolamine ionic liquids (CAILs) serving as aqueous lubricating additives were studied by applying positive and negative potentials on the friction pair, accompanied by the comprehensive discussion of data from critical micelle concentration, quartz crystal microbalance, ECR, and MD results. The results reveal that the adsorption behavior, unexpectedly, was affected by the high polarity of H2O, where a less dense double-layer structure is observed at the interface by model imitation. Conversely, the monomolecular adsorption layer constructed electrostatically between the polar head (-COO-) and the positive base dominates the tribofilm. Meanwhile, the cations are partially accumulating around anions in the presence of static electricity, which does not form a neat and dense one-to-one corresponding cation-anion pair. In the solution, the IL maintains a state of dissociation and minor agglomeration. Furthermore, an increase in alkyl chains contributes to the thickness of the protective film generated by CAILs on the sliding asperity. Eventually, the synergistic effect from physical adsorption and the tribochemical reaction is responsible for excellent lubricity and antiwear performance of CAILs.

Superior Adsorption Property of a Novel Green Biosorbent Yttrium/Alginate Gel Beads for Dyes from Aqueous Solution

A novel biosorbent yttrium/sodium alginate (Y/SA) hydrogel was prepared by the crosslinking of sodium alginate (SA) and yttrium (Y) ions and characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Fourier Transform-Infrared (FTIR), UV visible diffuse reflectance spectroscopy (UV–Vis DRS) and Thermogravimetric Analysis (TGA), respectively. The important parameters affecting the adsorption of Congo Red (CR) and Weak Acid Brilliant Blue RAW (WABB RAW) onto Y/SA were investigated systematically, respectively. The results show that Y/SA gel beads have super-strong adsorption performance for CR and WABB RAW dyes in a wide pH range of 2.0–10.0. The equilibrium data fitted by Langmuir and Freundlich models were found to completely follow Langmuir model where the obtained maximum adsorption capacities of 1567 and 1087 mg/g for CR and WABB RAW were very close to the experimental adsorption capacities, respectively, showing the adsorption of monomolecular layer. The adsorption kinetic data of two dyes by Y/SA fully accorded with the pseudo-second-order rate equation and adsorption processes were mainly controlled by intraparticle diffusion. The results of thermodynamic study indicate the feasible, spontaneous and exothermic nature of adsorption reaction. The further study revealed that electrostatic adsorption, hydrogen bonding and ion exchange reaction were the predominant adsorption for dye removal from aqueous solution by Y/SA gel beads. As a highly efficient, green and conducive to solid–liquid separation biosorbent, Y/SA hydrogel has great potential-application prospects for the purification of high-concentration dyestuff effluent.