Entire Adsorption Process Research Articles

Exploration of adsorption properties of organic corrosion inhibitors on layered double hydroxide nanosheet: A molecular dynamics simulation study

Understanding the adsorption of organic corrosion inhibitors with different functional groups on layered double hydroxide (LDH) nanosheet is crucial for the synthesis of these protective materials. In this study, the adsorption process of five deprotonated organic corrosion inhibitors—lactate (Lc), 2-hydroxybenzothiazole (2-OH-BTH), 2-mercaptoethanesulfonic acid (MS), N,N-dimethylethanolamine (DMEA), and eugenol (EG)—on LDH nanosheets was simulated. The adsorption rate, adsorption configuration, and adsorption stability between LDH nanosheet and organic corrosion inhibitors were investigated throughout the entire adsorption process. The study observed consistency in the adsorption rate and stability of these organic corrosion inhibitors in the following order: Lc > 2-OH-BTH > MS > DMEA > EG. Additionally, hydrogen bonds between the organic corrosion inhibitors and the LDH nanosheet is the primary mechanism driving adsorption. The number and stability of hydrogen bonds influenced both the adsorption rate and stability. It is noteworthy that 2-OH-BTH and DMEA have not previously been incorporated into LDH. There is potential for these two organic corrosion inhibitors to be modified for LDH, suggesting significant prospects for future research.

Adsorption studies of methylene blue on cation-modified graphene oxide and graphene oxide/MXene membranes

Membranes prepared from graphene oxide (GO) have greater advantages over traditional materials for water treatment, while MXene is a good candidate for pollutant removal. However, the effect of different cations introduced into the prepared GO membranes on their adsorption performance must be further explored. In this study, a series of cation-modified GO and GO/MXene membranes were prepared based on the self-assembly of GO. Na+-modified membranes were found to be more effective at removing methylene blue (MB) than multivalent cation-modified GO membranes. However, the cation-modified GO/MXene membranes improved the MB adsorption efficiency, and the higher the ionic valence, the more pronounced the effect. In addition, the effects of the pH, temperature, contact time and initial concentration of MB on the adsorption performance of the membranes were investigated. The best removal of MB was achieved under neutral conditions, and the adsorption process was consistent with quasi-secondary kinetics and Langmuir isotherm models. The fitting results of the Langmuir isotherm model showed that the maximum adsorption capacities of the cation-modified GO membranes for MB were 654.9, 319.8, and 246.3 mg/g, respectively. The maximum adsorption capacities of the cation-modified GO/MXene membranes for MB were 687.3, 497.6, and 772.4 mg/g, respectively. Furthermore, the results of the intraparticle diffusion model revealed that the entire adsorption process was controlled by both external and internal diffusion. The thermodynamic analysis results indicated that the entire adsorption process was a heat-absorbing process and could proceed spontaneously. That the findings suggest that the Na+-modified GO and Al3+-modified GO/MXene membranes demonstrate the best adsorption effects and are promising adsorbents for MB removal.

Preparation of carboxymethyl cellulose/graphene oxide/ZIF-8 aerogels for efficient methylene blue adsorption

Despite the promising potential of zeolitic imidazole framework-8 (ZIF-8) for dye adsorption, addressing challenges such as aggregation and recycling difficulties remains essential. Herein，a novel three dimensional (3D) carboxymethyl cellulose (CMC), graphene oxide (GO) and ZIF-8 hybrid aerogel (CGZ-3) was prepared via blending ZIF-8 into the CMC-GO matrix. The structure and composition of CGZ-3 were characterized by SEM, FT-IR, TG and XPS. Adsorption experiments were conducted to optimize various parameters affecting the behavior of methylene blue (MB) adsorption. The composite aerogel exhibited an obvious lamellar network structure, with a surface rich in oxygen-containing functional groups such as -OH and -COOH. CGZ-3 demonstrated a rapid adsorption rate for MB, achieving a removal efficiency of 96% within 15 minutes. The entire adsorption process was spontaneous and endothermic, consistent with the pseudo-first-order kinetic model and Langmuir adsorption isotherm model. The maximum theoretical adsorption capacity was 427.35 mg/g at 298 K. Selective adsorptions tests demonstrated high selectivity of the composite aerogel for MB, and dynamic adsorption further confirmed the exceptional adsorption capacity of CGZ-3. After five cycles of adsorption-desorption, the MB removal rate remained above 95%, with an adsorption capacity exceeding 240 mg/g, highlighting the stability and reusability of CGZ-3. Collectively, the CGZ-3 would be a potential material for the adsorptive removal of MB in practical water treatment.

Agarose‐sodium alginate hydrogel beads enhanced with zeolitic imidazolate frameworks/multiwalled carbon nanotubes nanoparticles for efficient adsorption and selective separation of methylene blue

AbstractThe urgent problem to solve is how to design a kind of green and porous adsorbent that can effectively remove dye pollutants in the field of the sewage treatment. The objectives of this investigation are to incorporate zeolitic imidazolate frameworks‐8 (ZIF‐8) particles in situ onto the surface of multiwalled carbon tubes (MWCNTs) and integrate them into an agarose‐sodium alginate (ASA) double network hydrogel. The resulting composite hydrogel beads, denoted as MWCNTs/ZIF‐8/ASA (MZASA), are synthesized using calcium ion crosslinking. The addition of agarose is employed to create a dual‐crosslinked hydrogel, thereby enhancing the mechanical properties of the ASA hydrogel. By incorporating MWCNTs/ZIF‐8 nanoparticles, the surface area of the MZASA hydrogel is augmented, leading to an enhancement in dye adsorption capacity. In batch sorption mode, the maximum absorbency of the resulting hydrogel beads for methylene blue (MB) is 493.799 mg/g, which was a third greater than that of pure SA beads. Absorption of MB obeys the pseudo‐second‐order kinetic model and Langmuir isotherm model, suggesting monolayer chemisorption adsorption. Analysis of the thermodynamics proves that the entire adsorption process is exothermic and spontaneous. Moreover, the MZASA hydrogel beads show high selectivity for cationic dyes in the mixed dye test. Hence, the synthesized MZASA hydrogel beads serve as a highly effective, innovative, and reusable adsorbent for eliminating cationic dyes from water‐based solutions.

Theoretical prediction of stable WB4 monolayer as a high-capacity anode material for alkali-metal ion batteries

As a rapidly evolving 2D monolayer material, tungsten tetraboride MBene exhibits innate advantages in electrochemical applications because of its unique graphene-like structure and metallic properties. In this study, we utilized first-principles calculations to identify the potential applications of WB4 as an anode material in rechargeable alkali-metal-ion batteries. The findings imply that the Li, Na, and K adsorption on the WB4 surface results in exceptionally high conductivity, and the WB4 monolayer can effectively adsorb these ions with significant adsorption energies of −2.516 eV, −2.356 eV, and −2.941 eV for Li, Na, and K ions, respectively. The results indicate that WB4 exhibits excellent stability during lithiation, sodiation, and potassiation. Notably, we propose high storage capacities for LIBs (708mAh/g), SIBs (472mAh/g), and KIBs (177 mAh/g), with maintained structural stability for the adsorption of these metal ions. The measured average open circuit voltages for WB4 were found to be 0.77 V (Li), 0.73 V (Na), and 0.80 V (K), and metallicity remain good maintained within the entire adsorption process. The calculated migration energy barriers for Li, Na, and K were 0.47 eV,0.21 eV and 0.13 eV respectively. The notable properties of WB4 make it an advantageous electrode material for alkali-metal ion batteries.

Preparation of mixed-mode weak cation exchange magnetic solid-phase extraction sorbent and its application in the extraction of 21 illicit drugs from wastewater

The detection of illicit drugs in wastewater can effectively monitor and evaluate the trend of illicit drug abuse. A novel mixed-mode cation exchange magnetic sorbent Fe3O4 @poly(ST/DVB/MA-COOH) was prepared and firstly applied as magnetically dispersed solid phase extraction material to efficiently, rapidly, and selectively extract 21 illicit drugs from wastewater. The selectivity of the sorbent was mainly attributed to the electrostatic interaction. The effects of Fe3O4 @poly(ST/DVB/MA-COOH) preparation and extraction conditions on the adsorption performance were thoroughly discussed. Among the 21 illicit drugs, the absolute extraction recovery values for 19 illicit drugs were greater than 80 % and the entire adsorption process could be achieved in one minute. Subsequently, the Fe3O4 @poly(ST/DVB/MA-COOH) sorbent combined with UHPLC-MS/MS was used to establish a quantitative method for the effectively extracted 19 illicit drugs in wastewater. The method had a good determination coefficient in the range of 0.2–200 ng/L and the limits of detection of the method were 0.03–0.67 ng/L. The spiked recovery values were in the range of 87.0–119.6 %. Finally, the method was successfully applied to the detection of 19 illicit drugs in wastewater samples and also compared with the commonly used SPE method. The obtained results indicate that Fe3O4 @poly(ST/DVB/MA-COOH) has great advantages in the detection of illicit drugs in wastewater.

Alginate Modified Magnetic Polypyrrole Nanocomposite for the Adsorptive Removal of Heavy Metal.

The presence of heavy metals with high acute toxicity in wastewater poses a substantial risk to both the environment and human health. To address this issue, we developed a nanocomposite of alginate-encapsulated polypyrrole (PPy) decorated with α-Fe2O3 nanoparticles (Alg@Mag/PPy NCs), fabricated for the removal of mercury(II) from synthetic wastewater. In the adsorption experiments, various parameters were examined to identify the ideal conditions. These parameters included temperature (ranging from 298 to 323 K), initial pH levels (ranging from two to nine), interaction time, amount of adsorbent (from 8 to 80 mg/40 mL), and initial concentrations (from 10 to 200 mg/L). The results of these studies demonstrated that the removal efficiency of mercury(II) was obtained to be 95.58% at the optimum pH of 7 and a temperature of 303 K. The analysis of adsorption kinetics demonstrated that the removal of mercury(II) adhered closely to the pseudo-second-order model. Additionally, it displayed a three-stage intraparticle diffusion model throughout the entire adsorption process. The Langmuir model most accurately represented equilibrium data. The Alg@Mag/PPy NCs exhibited an estimated maximum adsorption capacity of 213.72 mg/g at 303 K, surpassing the capacities of most of the other polymer-based adsorbents previously reported. The thermodynamic analysis indicates that the removal of mercury(II) from the Alg@Mag/PPy NCs was endothermic and spontaneous in nature. In summary, this study suggests that Alg@Mag/PPy NCs could serve as a promising choice for confiscating toxic heavy metal ions from wastewater through adsorption.

Deposition freezing, pore condensation freezing and adsorption: three processes, one description?

Abstract. Heterogeneous ice nucleation impacts the hydrological cycle and climate through affecting cloud microphysical state and radiative properties. Despite decades of research, a quantitative description and understanding of heterogeneous ice nucleation remains elusive. Parameterizations are either fully empirical or heavily rely on classical nucleation theory (CNT), which does not consider molecular-level properties of the ice-nucleating particles – which can alter ice nucleation rates by orders of magnitude through impacting pre-critical stages of ice nucleation. The adsorption nucleation theory (ANT) of heterogeneous droplet nucleation has the potential to remedy this fundamental limitation and provide quantitative expressions in particular for heterogeneous freezing in the deposition mode (the existence of which has even been questioned recently). In this paper we use molecular simulations to understand the mechanism of deposition freezing and compare it with pore condensation freezing and adsorption. Based on the results of our case study, we put forward the plausibility of extending the ANT framework to ice nucleation (using black carbon as a case study) based on the following findings: (i) the quasi-liquid layer at the free surface of the adsorbed droplet remains practically intact throughout the entire adsorption and freezing process; therefore, the attachment of further water vapor to the growing ice particles occurs through a disordered phase, similar to liquid water adsorption. (ii) The interaction energies that determine the input parameters of ANT (the parameters of the adsorption isotherm) are not strongly impacted by the phase state of the adsorbed phase. Thus, not only is the extension of ANT to the treatment of ice nucleation possible, but the input parameters are also potentially transferable across phase states of the nucleating phase at least for the case of the graphite/water model system.

Sensing properties of SF6 decomposition gas sensor based on Rh doped α-AsP monolayer

The detection of decomposition components of SF6 insulating gas in gas-insulated switchgear (GIS) is of great significance to evaluating GIS's operating state and ensuring the equipment's safety. In order to detect and diagnose the main decomposition gases SO2, SOF2, and SO2F2 of SF6, this work systematically analyses the intrinsic α-AsP monolayer and two Rh-modified α-AsP monolayers. Specifically, the adsorption structure, energy, charge transfer and deformed charge density, the total density of states, the partial density of states, and recovery time were discussed and calculated in detail, and the internal mechanism of the entire adsorption process was clarified. Meanwhile, the results show that Rh adsorbed on α-AsP monolayer (Rh-AsP-O) has a good adsorption effect on SO2, SOF2, and SO2F2 gases. From the sensor's perspective, the Rh-AsP-O monolayer has potential applications in the gas-sensing field of SO2, SOF2, and SO2F2.

Interactive adsorption mechanism and product distribution of impurity gases on CO2 adsorption over amine-grafted ZSM-5/SBA-16 adsorbent

Solid amine adsorbents hold promising application prospects in the realm of industrial flue gas decarbonization. Nevertheless, there remains a need for substantial improvement in the cycling stability of solid amine adsorbents. Additionally, the competitive adsorption mechanism of solid amine adsorbents pertaining to flue gas components lacks thorough verification. In this study, amine-grafted micro-mesoporous ZSM-5/SBA-16 adsorbents were synthesized to improve the CO2 adsorption capacity and investigate the effect of impurity gases on CO2 adsorption. Various characterization techniques, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption, and elemental analysis, were employed to analyze the properties of the adsorbents. The loading analysis of the micro-mesoporous molecular sieve revealed that ZS-A-2.0 exhibited the highest CO2 adsorption capacity of 41.39 mg/g. Mass spectrometry was utilized to evaluate the co-adsorption experimentation involving multicomponent gases. The breakthrough curves of CO2 displayed dual stages at low concentrations, suggesting the simultaneous occurrence of physical and chemical adsorption throughout the entire adsorption process. Based on temperature programming desorption (TPD) and in situ Fourier transform infrared spectroscopy (FTIR), the results indicated a notable enhancement in CO2 adsorption due to the presence of H2O. Conversely, the presence of SO2 and NO exhibited adverse effects on CO2 adsorption, consequently hindering the formation of carbamate and (RNH3)2CO3 adsorption products. This study presents, for the first time, a comprehensive investigation into the interactive adsorption mechanism and product distribution between CO2 and impurity gases. The findings presented herein provide valuable insights and essential support for practical flue gas applications.

Construction of carboxylated-GO and MOFs composites for efficient removal of heavy metal ions

Two-dimensional graphene oxide (GO) and metal–organic frameworks (MOFs) have great potential applications as high-performance adsorption materials. In this work, carboxylated-GO and MOFs have been successfully integrated to form nanocomposites (GO-COOH/MOF-808) with the combination of advantages of both and then demonstrated the excellent adsorption properties of heavy metal ions. The adsorption capacity of GO-COOH/MOF-808 and the influencing factors of the adsorption process are explored. The analysis shows that the adsorption equilibrium of heavy metal ions Pb(II), Cd(II), Co(II), Ni(II), and Cu(II) by GO-COOH/MOF-808 composites can be reached in 20 min under condition of the initial concentration of 100 mg/L and pH value of 5.5. Pb(II), Cd(II), Co(II), Ni(II), and Cu(II) have higher adsorption efficiencies, which are 157.78 mg/g, 135.96 mg/g, 82.35 mg/g, 90.99 mg/g, and 91.49 mg/g, respectively. Furthermore, the entire adsorption process followed the Langmuir isotherm model and the pseudo-second-order rate equation, suggesting that ion exchange and chemical adsorption are dominant. The synergistic effect of ion exchange, electrostatic adsorption, chemisorption, π-π interactions, and coordination complexation is attributed to the possible mechanisms of heavy metal ion adsorption. This research suggests that GO-COOH/MOF-808 is a promising and efficient adsorbent for heavy metal ion removal.

Monitoring the Molecular Structure of Fibrinogen during the Adsorption Process at the Buried Silicone Oil Interface In Situ in Real Time

Interfacial proteins play important roles in many research fields and applications, such as biosensors, biomedical implants, nonfouling coatings, etc. Directly probing interfacial protein behavior at buried solid/liquid and liquid/liquid interfaces is challenging. We used sum frequency generation vibrational spectroscopy and a Hamiltonian data analysis method to monitor the molecular structure of fibrinogen on silicone oil during the adsorption process in situ in real time. The results showed that the adsorbed fibrinogen molecules tend to adopt a bent structure throughout the entire adsorption process with the same orientation. This is different from the case of adsorbed fibrinogen on CaF2 with a linear structure or on polystyrene with a bent structure but a different orientation. The method introduced herein is generally applicable for following time-dependent molecular structures of many other proteins and peptides at interfaces in situ in real time at the molecular level.

Determination of the surface properties and adsorption states of nanoporous materials using the zeta adsorption isotherm.

The adsorption process of porous materials has always been a popular field of research in interfacial physics, and the surface physical parameters of materials can be obtained from their adsorption characteristics, which has a great influence on the performance of materials. Based on the zeta adsorption isotherm, we propose a method based on the zeta adsorption isotherm to predict the entire adsorption process of porous materials and determine material surface properties from the measured isotherm data in the heterogeneity-free range. We applied the zeta constants of the silica adsorption system to the corresponding adsorption isotherm of the porous material. The results showed that the predicted adsorption isotherms are in good agreement with the experimental measurements before pore filling and can effectively identify the pressure ratios at the beginning and end of pore filling. In the region of high-pressure ratios, the Kelvin equation was utilized to calculate the pressure ratio at a contact angle of 0°. The surface parameters of the materials were determined by geometrically calculating the variation of the adsorption amount and the desorption isotherms in the high-pressure ratio range were calculated from these surface parameters. The predicted desorption isotherms can well reflect the adsorption process of silica porous materials in the region of a high-pressure ratio. In addition, for the surface parameters of the materials, the specific surface area calculated from the adsorption and desorption isotherms, respectively, differed by less than 7.9%, and the reliability of the method was verified by comparing the results with those of the argon adsorption systems.

Water adsorption kinetics of silica based porous desiccants by volumetric method

The adsorption kinetics of solid desiccants is critical for the design and optimal operation of air-conditioning systems. However, owing to the complex combination of diffusion processes in the interparticle layer and intraparticle mesopores/micropores, adequately illustrating the adsorption kinetics of solid desiccants is difficult. In this study, the adsorption kinetics of a microsphere silica gel bead was investigated using the volumetric method in a limited batch adsorption system. An analytical solution was adopted for the biporous diffusion model to obtain the effective mesopore diffusivity. A comprehensive diffusion model was developed based on the initial estimation by the analytical solution. The model, i.e., the triple diffusion resistance model that includes three transport resistances, viz., interparticle, mesopore, and micropore resistance was subsequently validated through an experiment. The results show that the rate-limiting step in the entire diffusion and adsorption process changes from intraparticle to interparticle diffusion with increasing sample mass. The proposed model considering the effect of interparticle diffusion successfully determines the effective mesopore diffusivity for each sample mass.

Adsorption characteristics of six bisphenol compounds on magnetic three-dimensional nitrogen-doped carbon nanomaterials and their use in effervescent reaction-assisted dispersive microextraction

Herein, we successfully prepared magnetic Co/Ni-based N-doped 3D carbon nanotubes and graphene nanocomposites (CoNi@NGC) using a simple high-temperature calcination method. The CoNi@NGC nanocomposites were used as adsorbents to study their adsorption performances and underlying kinetic mechanisms for six types of bisphenol compounds (BPs) in water. They were also used as extractants, and acid-base effervescent tablets were used to enhance extractant dispersion with the aid of vigorous CO2 bubbling. Thus, a novel pretreatment method was developed, denoted effervescent reaction-assisted dispersive solid-phase microextraction (ER-DSM), which was combined with high performance liquid chromatography-fluorescence detection (HPLC-FLD) to rapidly quantify trace-level BPs in several drinks. The morphology and structure of the CoNi@NGC adsorbent were characterized in detail using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption and desorption (BET-BJH), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The CoNi@NGC nanocomposites were successfully doped with N and exhibited large specific surface areas (109.42 m2/g), abundant pores, and strong magnetic properties (17.98 emu/g).Key parameters were rigorously optimized to maximize the adsorption performance of CoNi@NGC, including adsorbent dosage, solution pH, temperature, and time. Under the constant conditions of pH=7, 5 mg of CoNi@NGC, initial BP concentrations of 5 mg/L, and 5 min of shaking at 298 K, the adsorption percentages of bisphenol M (BPM) and bisphenol A (BPA) reached respective maxima of 99.01% and 98.21%. Remarkably, those of bisphenol Z (BPZ), BPA, and BPM reached almost 100% after 90 min. The adsorption between the BPs and CoNi@NGC was mainly governed by hydrogen bonds, electrostatic interactions, and π-π conjugation. The entire adsorption process was consistent with Freundlich adsorption and a quasi-second-order kinetic equation, representing spontaneous adsorption. Via integration with HPLC-FLD, ER-DSM was used to rapidly extract and analyze trace-level BPs in six types of boxed drinks. Critical factors were optimized individually, including the type of eluent and elution time and volume, which influenced the enrichment effect. Under the optimized extraction conditions (pH=7, 5 mg CoNi@NGC, elution with 2 mL acetone for 6 min), the limits of detection and quantification of the novel extraction method were 0.06-0.20 and 0.20-0.66 μg/L, respectively. The intra- and inter-day precisions spanned the ranges 1.44%-4.76% and 1.69%-5.36%, respectively, and the recoveries in the actual samples were in the range 82.4%-103.7%. Moreover, the respective residual levels of BPA and BPB in peach juice samples were 2.09 and 1.37 μg/L. Regeneration studies revealed that the CoNi@NGC adsorbent could be reused at least five times, which significantly reduced the cost of evaluation. In summary, compared to other methods, this method displays the advantages of a high sensitivity, rapid extraction, and environmental friendliness, thereby exhibiting considerable potential for use in conventional monitoring of trace-level BPs in food matrices.

Ziziphus Jujube Seeds derived Biomass as Cost-Effective Biosorbent for the removal of Cr6+ from Aqueous solutions: Isotherm and Kinetic Studies

<p>Biosorption of hexavalent chromium ions from the synthetic solution was performed using activated Ziziphus jujube seeds powder as an adsorbent material. A chemical synthesis process prepared the adsorbent, and various methods have evaluated its characteristics. FTIR, SEM and EDX analysis was conducted to check the ability of hexavalent chromium uptake from the synthetic solutions. Batch mode of adsorption process was performed and the adsorption parameters of pH, concentration, dose, contact time and temperature were found in various operating conditions. The entire adsorption process was evaluated by isotherm and kinetic models to check the nature of the adsorption process and its chemical reactions. Thermodynamic studies were conducted, desorption studies were used to recover the spent adsorbent using concentrated hydrochloric acid.</p>

Mass transfer analysis of total nitrogen adsorption from river water onto tea waste (Camellia Sinensis)

Natural lignocellulosic materials have becoming a popular trend in removing heavy metal ions. However, these materials have limited usage in organic and nutrient adsorption with the mass transfer analysis of the adsorption process remains uncommon. Hence, this study proposes the application of different pretreated tea wastes (untreated tea waste and acid treated tea waste) in total nitrogen adsorption to evaluate the mass transfer of the adsorption process. The experiment was conducted in a prototype where naturally contaminated water was collected and circulated through the different pretreated tea waste for five consecutive days. Total nitrogen in the water was tested every day according to the APHA method for which results collected are further evaluated using empirical mathematical models. The result indicated that acid treated tea waste (4.864 mg/g) possessed higher adsorption capacity than untreated tea waste (4.293 mg/g) in total nitrogen adsorption. Further evaluation identified the global mass transfer rate for acid treated tea waste (14.37422 d−1) was greater than untreated tea waste (2.980625 d−1) in 5% outflow of total nitrogen, primarily believed to be of higher initial concentration in the solution. Besides, porous diffusion mass transfer is seemingly the key factor that contributed to the entire adsorption process due to the porosity and surface area of the adsorbents. Finally, it can be concluded that tea waste is a good alternative adsorbent for total nitrogen removal from naturally contaminated water.

Adsorption and accumulation mechanism of N2 on groove-type rough surfaces: A molecular simulation study

Flotation is an effective method for mineral separation based on differences in surface physicochemical properties, in which the adsorption and accumulation of gas on the mineral surface is the key process. In this study, molecular dynamics (MD) simulations were employed to clarify the mechanism of adsorption and accumulation of gas on rough surfaces during flotation. A variety of three-phase initial gas–liquid–solid models were constructed by adding grooves of various widths and heights on the base model, which represents the differences in substrate roughness. The results showed that N2 molecules were adsorbed and accumulated at the bottom of the rough substrate and solid–liquid interface by expelling H2O molecules from the bottom of the groove. Gas adsorption gradually increased with increasing substrate roughness for a set groove width. Meanwhile, the gas molecules were adsorbed and accumulated in the largest amount at the bottom of the medium-roughness substrate when the height was kept fixed because of the limitation of the channel size and the interaction energies between the substrate and N2 molecules. From the perspective of force, the van der Waals force plays a leading role throughout the entire adsorption process. Revealing the adsorption and accumulation behavior of gas on rough substrates and the effect of substrates with various roughness values on gas adsorption, which will help to strengthen the understanding of the gas–liquid–solid interaction mechanism in the flotation process.

Simultaneous adsorption of phosphate and tetracycline by calcium modified corn stover biochar: Performance and mechanism

It is important to solve the problems of biomass treatment and combined contaminants removal in environmental remediation. In this study, a calcium (Ca) modified biochar (CaBC800) was fabricated using corn stover (CS) as a raw material to remove phosphate and tetracycline (TC). The experimental results indicate that CaBC800 can adsorb both inorganic phosphate and organic TC. The entire adsorption process corresponds to pseudo-second-order kinetics and Langmuir adsorption isotherm. The maximum adsorption capacities of phosphate and TC were 33.944 and 33.534 mg/g, respectively. The phosphate adsorption was demonstrated to mainly depend on the chemical precipitation by Ca2+ and ligand exchange by hydroxyl groups from CaBC800. Meanwhile, hydrogen bonding from oxygen functional groups and π-π interactions from aromatic rings are the main adsorption mechanisms of TC. This study provides a new adsorbent to efficiently remove phosphate and TC, and the simultaneous adsorption indicates the application potential of CaBC800 in wastewater remediation.

Construction of stable beta-cyclodextrin grafted polypropylene nonwoven fabrics for the adsorption of bisphenol A

Herein, a convenient and environment-friendly grafting strategy was used to anchor beta-cyclodextrin (β-CD) on polypropylene (PP) fabric, which includes grafting of GMA onto PP nonwoven fabric via 60Co γ-ray and introduction of β-CD by the ring-opening reaction between the hydroxyl group of β-CD and the epoxy group of GMA. The as-prepared fabric composite (PP-g-GMA-βCD) showed a bisphenol A (BPA) adsorption amount of 27.72 mg/g in the single BPA solution (75 ppm). The BPA adsorption amount by PP-g-GMA-βCD was not sensitive to pH condition, and the anti-interference ability to ions was also strong. The Langmuir isotherm model was found to be suitable for the adsorption of BPA, and the entire adsorption process followed the pseudo-second-order kinetics. PP-g-GMA-βCD showed excellent stability and reusability that the BPA adsorption amount remained almost unchanged after 10 successive recycles. In the BPA and methyl orange (MO) mixed solution (BPA: 75 ppm; MO: 50 ppm), the adsorption amounts of BPA and MO by PP-g-GMA-βCD were 23.88 and 20.83 mg/g, respectively. The presence of MO resulted in a little decrease in the adsorption amount of BPA, as β-CD can also form host–guest complexes with MO, and there would also be π-π and H-bond interactions between BPA and MO.