Competitive Adsorption Experiments Research Articles

Research on Mechanism and Effect of Enhancing Gas Recovery by CO2 Huff-n-Puff in Shale Gas Reservoir.

The technology of CO2-enhanced gas recovery (CO2-EGR) plays a pivotal role in the CCUS (Carbon Capture, Utilization, and Storage) industry, which helps to achieve a win-win situation of economic benefit and environmental benefit for gas fields. Shale gas reservoirs, with their unique geological and surface engineering advantages, are one of the most promising options for CCUS implementation. Focusing on shale formations within the mid-deep blocks of the Sichuan Basin, this study conducted competitive adsorption experiments using multicomponent gases. Through physical simulations and single-well numerical modeling, factors such as injection volume, timing, shut-in time, and huff-n-puff rounds were examined for their impact on recovery. The results show that the higher the CO2 content in the injected medium, the more pronounced advantage in gas adsorption on shale surfaces. Optimal performance was achieved with a CO2 content in the injection medium of 80% to 100%, an injection volume of 0.2-0.3 PV, a shut-in time exceeding 6 h, and a relatively delayed injection timing. The recovery in the first round of huff-n-puff was increased by 24.2% to 47.8%, which gave a full play to the role of huff-n-puff and achieved favorable benefits. Based on the middle-deep geological parameters, a single-well numerical simulation was established, which demonstrates that single-well EUR (estimated ultimate recovery) can be increased by 14.2% to 19.8% compared to gas wells without CO2 injection. This study provides essential guidance for the enhanced recovery in shale gas reservoirs through CO2 huff-n-puff.

Rapid eco-friendly selective dye removal using modified chitosan-based sponges: Synthesis, characterization, and application

The ongoing challenge of water scarcity persists alongside a concerning rise in water pollution driven by population expansion and industrial development. As a result, urgent measures are imperative to address the pressing need for a clean and sustainable water supply. In this study, a sustainable and green approach was utilized to prepare four chitosan-based sponges from a chemically modified chitosan with different alkyl chains in aqueous medium and at room temperature. The resulting sponges displayed excellent stability in water with outstanding dye removal efficiency. The adsorption capacity was associated with the alkyl chain length incorporated to the polymer backbone. All sponges displayed a high adsorption capacity of methyl orange (MO) ranges between 238 and 380 mg g−1, while a low capacity were obtained for methylene blue (MB) and Rhodamine B (RB). Competitive adsorption experiments were conducted on binary and ternary mixtures to assess the selective removal of MO from a mixture of dyes in which the separation factor was found to be ranging between 1.6 and 32. The adsorption kinetics isotherms of all sponges followed the pseudo-second-order, and the Langmuir model was found to be more suitable than the Freundlich for the adsorption of MO on the sponges. The chitosan-based sponges showed stable performance, robustness and reusability over 5 adsorption-desorption cycles, indicating their great potential for water treatment applications.

Polyamide 6 microplastics as carriers led to changes in the fate of bisphenol A and dibutyl phthalate in drinking water distribution systems: The role of adsorption and interfacial partitioning

Microplastics (MPs) co-exist with plastic additives and other emerging pollutants in the drinking water distribution systems (DWDSs). Due to their strong adsorption capacity, MPs may influence the occurrence of additives in DWDSs. The article investigated the occurrence of typical additives bisphenol A (BPA) and dibutyl phthalate (DBP) in DWDSs under the influence of polyamide 6 (PA6) MPs and further discussed the partitioning of BPA/DBP on PA6s, filling a research gap regarding the impact of adsorption between contaminants on their occurrence within DWDSs. In this study, adsorption experiments of BPA/DBP with PA6s and pipe scales were conducted and their interaction mechanisms were investigated. Competitive adsorption experiments of BPA/DBP were also carried out with site energy distribution theory (SEDT) calculations. The results demonstrated that PA6s might contribute to the accumulation of BPA/DBP on pipe scales. The adsorption efficiencies of BPA/DBP with both PA6s and pipe scales were 26.47 and 2.61 times higher than those with only pipe scales. It was noteworthy that BPA had a synergistic effect on the adsorption of DBP on PA6s, resulting in a 26.47 % increase in DBP adsorption. The article provides valuable insights for the compounding effect of different types of additives in water quality monitoring and evaluation.

Fabrication of fluorinated triazine-based covalent organic frameworks for selective extraction of fluoroquinolone in milk

A novel fluorinated triazine-based covalent organic frameworks (F-CTFs) was designed and synthesized by using melamine and 2,3,5,6-tetrafluoroterephthalaldehydeas as organic ligands for selective pipette tip solid-phase extraction (PT-SPE) of amphiphilic fluoroquinolones (FQs). The competitive adsorption experiment and mechanism study were carried out and verified that this F-CTFs possesses favorable adsorption affinity for FQs. The abundant fluorine affinity sites endowed the F-CTFs high selectivity to FQs extraction through F-F interactions. The adsorption capacity of F-CTFs can reach up to 109.1 mg g−1 for enrofloxacin. The detailed characterization of the F-CTFs adsorbent involved the application of various techniques to examine its morphology and structure. Under optimized conditions, a method combining F-CTF-based PT-SPE with high-performance liquid chromatography (PT-SPE-HPLC) was established, which exhibited a broad linear range, excellent precision, and an impressively low limit of detection, and could be used for the determination of six FQs in milk, with LODs as low as 0.0010 μg mL−1. The recovery rates during extraction varied between 92.1% and 111.4%, exhibiting RSDs below 6.8% at different spiked concentrations.

Influence of biochar on the removal of Microcystin-LR and Saxitoxin from aqueous solutions

The present study assessed the effective use of biochar for the adsorption of two potent HAB toxins namely, Microcystin-LR (MCLR) and Saxitoxin (STX) through a combination of dosage, kinetic, equilibrium, initial pH, and competitive adsorption experiments. The adsorption results suggest that biochar has excellent capabilities for removing MCLR and STX, with STX reporting higher adsorption capacities (622.53–3507.46 µg/g). STX removal required a minimal dosage of 0.02 g/L, while MCLR removal needed 0.4 g/L for > 90%. Similarly, a shorter contact time was required for STX removal compared to MCLR for > 90% of toxin removed from water. Initial pH study revealed that for MCLR acidic conditions favored higher uptake while STX favored basic conditions. Kinetic studies revealed that the Elovich model to be most suitable for both toxins, while STX also showed suitable fittings for Pseudo-First Order and Pseudo-Second Order in individual toxin systems. Similarly, for the Elovich model the most suited kinetic model for both toxins in presence of each other. Isotherm studies confirmed the Langmuir–Freundlich model as the best fit for both toxins. These results suggest adsorption mechanisms including pore filling, hydrogen bonding, π–π interactions, hydrophobic interactions, electrostatic attraction, and dispersive interactions.

Ammonium ion removal from aqueous solutions in the presence of organic compounds, using biochar from banana leaves. Competitive isotherm models

BackgroundIndustrial, e.g. food industrial and domestic wastewaters contain huge amount of compounds causing eutrophication, and should be removed with high cost during wastewater treatment. However, these compounds could be utilized as fertilizers too. Biochar can remove a wide range of pollutants from water, such as ammonium, which can be found in relatively high concentration in dairy wastewaters. However, adsorption performance may be affected by the presence of other wastewater pollutants. Thus, this study aims to determine the efficiency of biochar as an adsorbent of ammonium in aqueous solutions in the presence of some selected organic compounds of typical dairy wastewaters such as bovine serum albumin (BSA), lactose, and acetic acid. Methods: The biochar was produced from banana leaves at 300 °C, modified with NaOH, and characterized by Scanning Electron Microscope – Energy Dispersive X-Ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectra (FTIR) analysis, and specific surface area measurements. Batch experiments were carried out to investigate the ammonium adsorption capacity and the ion competitive adsorption mechanism. Significant Findings: Results show that the surface structure of the biochar derived from banana leaves is different from other biochars previously studied; although the specific surface area is not very considerable and despite having nitrogen within the elemental composition, the biochar studied is capable of adsorbing 2.60 mg NH4+/m2, the highest ammonium removal in 2 h occurs at pH 9 and 500 mg biochar dose. Langmuir model in the monolayer phase analysis fits better for all scenarios and the maximum NH4+ adsorption capacity was 0.97 mg/g without organic compounds. In the multilayer adsorption phase, the isotherm model that best fits the data obtained is the Harkins-Jura model without organic compounds. The presence of organic compounds in the aqueous solution significantly impacts the adsorption of ammonium by biochar since it improves the adsorption capacity (1.132 mg/g BSA, 0.975 mg/g lactose, and 1.874 mg/g acetic acid). The Aranovich-Donohue isotherm model fitted the data obtained during ion competitive adsorption experiments well.

Separation of 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene by metal-organic framework Co(aip)(bpy)0.5

BackgroundThe separation of trimethylbenzene isomers is one of the most challenging problems in chemical industry because of their similar boiling points and kinetic diameters. The adsorption performance of 1,3,5-trimethylbenzene (1,3,5-TMS) and 1,2,4-trimethylbenzene (1,2,4-TMS) (1,3,5-TMS/1,2,4-TMS = 1:1) on Co(aip)(bpy)0.5 with cobalt-based columnar lamellae were investigated in this paper. MethodsIn this study, we used competitive adsorption experiments, kinetic and thermodynamic experiments, and regeneration experiments to investigate the adsorption amount and relative selectivity of 1,3,5-TMS and 1,2,4-TMS on Co(aip)(bpy)0.5, adsorption mechanism, and regeneration properties of Co(aip)(bpy)0.5. Significant findingsCompetitive adsorption experiments showed that Co(aip)(bpy)0.5 presented the highest relative selectivity α1,2,4-TMS/1,3,5-TMS among the eight MOFs studied. Both pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models were used to fit the data, which indicated that the PSO model was more compatible. Thermodynamic data was fitted by Langmuir, Freundlich, and Temkin models, from which the Langmuir model was most suitable. Thermodynamic parameters demonstrated that the adsorption was spontaneous and exothermic. The α1,2,4-TMS/1,3,5-TMS could reach 3.5 at 298.15 K. The crystal structure and adsorption experiments suggested that the separation of 1,3,5-TMS from 1,2,4-TMS on Co(aip)(bpy)0.5 was mainly due to π-π interaction, unsaturated metal ions, and Lewis acid-base interaction. After five adsorption-regeneration cycles, the adsorption amount of 1,3,5-TMS and 1,2,4-TMS decreased by 0.12 % and 0.05 %, respectively, and α1,2,4-TMS/1,3,5-TMS remained above 3.0.

Targeted degradation of Bisphenol A with peroxymonosulfate activated by nanoscale zero-valent iron supported on molecularly imprinted polymers

In order to address the limitation of active species being influenced by the complex water environment during the degradation of target pollutants, a catalyst called MIP-nFe0 was prepared. This catalyst consists of nanoscale zero-valent iron (nFe0) supported on molecularly imprinted polymers (MIPs) with specific recognition. It was designed for the targeted degradation of Bisphenol A (BPA) by activating peroxymonosulfate (PMS). Material characterization confirmed that nFe0 was successfully loaded onto MIPs without agglomeration and did not cause significant damage to the MIPs structure. Under specific conditions (50 mg/L BPA and 100 mg/L catalyst), PMS activation with MIP-nFe0 rapidly degraded most BPA in just 0.5 min. Competitive adsorption and degradation experiments revealed that MIP-nFe0 displayed the best adsorption (21.02 mg/g) and degradation (28.89 mg/g) efficiency for BPA compared with the control materials nFe0 and nFe0 supported on non-imprinted polymer (NIP-nFe0). MIP-nFe0 was further applied in the actual water background for BPA removal, MIP-nFe0 maintained efficient BPA removal in both river water as well as sewage plant tail water, which was significantly higher than NIP-nFe0 and nFe0. Free radical capture and quenching experiments demonstrated that active species of SO4−·, ·OH, ·O2−, and 1O2 existed in the system, with SO4−· played a major role.

Removal of Pb(II), Cu(II), and Ag(I) from aqueous solutions using biochar derived by P-enriched water hyacinth

ABSTRACT A new synthesis was developed to prepare engineered biochar derived from phosphorous-rich water hyacinth. The statistical analysis indicated a significant correlation between P content and the removal rates of Pb (II), Cu (II), and Ag (I), revealing the pivotal role of enrich P in the biochar for heavy metals (HM) removal. SEM-EDX, XRD and FTIR analyses validated the presence of P functional groups on the surface of P-biochar. Batch experiments showed that the strong acidic initial solution negatively affected the adsorption of HM ions, and a similar negative impact was observed during Cu (II) adsorption under the high ionic strength conditions. Competitive adsorption experiment confirmed P-biochar’s resilience against competing metal ions during the adsorption of HM ions. Pb (II) and Ag (I) adsorption were primarily governed by precipitation/reduction, along with complexation reactions involving P functional groups. Cu (II) adsorption was dominated by complexation between Cu (II) and P functional groups.

Synthesis and performance of a tetra-branched bicationic liquid demulsifier

The treatment of water-in-oil (W/O) emulsions has always been a challenge in the petroleum industry. In this article, a tetra-branched bicationic liquid demulsifier (PAL-Cl) was prepared. The structure of PAL-Cl was confirmed by Fourier-transform infrared spectrum (FT-IR), Nuclear magnetic resonance spectrum (NMR) and Gel permeation chromatography (GPC). Some factors affecting demulsification efficiency (DE) such as dosage, salinity, pH, temperature, etc. were explored in detail. The DE reached 96.5 % after demulsifying with 50 mg/L of PAL-Cl at 70 °C for 240 min. Especially, a relatively lower temperature of 40 °C could obtain the DE of 94.1 % with 250 mg/L of PAL-Cl for 360 min. Moreover, PAL-Cl has outstanding acid, alkali and salt resistance. In addition, the demulsification mechanism was in detail investigated by surface tension (SFT), interfacial tension (IFT), competitive adsorption experiments, coalescence time of droplets (CT), three-phase contact angle (CA), zeta potential and micrographs.

Study on the adsorption performance of Cu2+ in wastewater by red mud

The treatment of copper-nickel wastewater has consistently posed a challenging problem in the field of environmental protection. In this experimental study, the adsorbent used was prepared from Bayer's method-derived red mud (RM). The adsorption characteristics of RM adsorbent on Cu2+ in copper-nickel wastewater, as well as the impact of Ni2+ on the removal effectcy of Cu2+, were investigated. The adsorption performance of Cu2+ in copper-nickel wastewater by adsorbent dosage, adsorption time and pH were investigated, and the adsorption mechanism was discussed. The adsorption process conformed to the pseudo-second-order kinetic model (R2 =0.986) and the Langmuir model (R2 =0.989), indicating that it was a monolayer chemical adsorption process. The raw materials were characterized using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray fluorescence (XRF). The results indicated that the adsorption process of Cu2+ and Ni2+ on RM was primarily influenced by surface chemical groups such as O-H, C-O-C, Si-C, and Si-O, among others. The adsorption rate of Cu2+ by RM could achieve 100% when the concentration of Cu2+ solution was 100 mg/L, with an optimal dosage of adsorbent at 0.20 mg/L and the best adsorption effect observed after 240 min. The adsorption of Cu2+ and Ni2+ by RM exhibits unidirectional competitive adsorption behavior. Furthermore,in competitive adsorption experiments, RM exhibits good selectivity towards Cu2+, with Ni2+ exhibiting minimal inhibitory effect on Cu2+ when the two elements coexist. Therefore, this paper offers potential research value for the large-scale application of RM in copper-nickel wastewater treatment processes.

Preparation of novel polyvinyl alcohol–carbon nanotubes containing imidazolyl ionic liquid/chitosan hydrogel for highly efficient uranium extraction from seawater

A novel polyvinyl alcohol–carbon nanotube containing an imidazolyl ionic liquid/chitosan composite hydrogel (termed CBCS) was prepared for highly selective uranium adsorption from seawater. The results show that CBCS has good adsorption properties for uranium within the pH range of 5.0–8.0. Kinetics and thermodynamics experiments show that the theoretical maximum adsorption capacity of CBCS to U(VI) is 496.049 mg/g (288 K, pH = 6.0), indicating a spontaneous exothermic reaction. Mechanism analysis shows that the hydroxyl group, amino group, and CN bond on the surface of CBCS directly participate in uranium adsorption and that the dense pores on the surface of CBCS play an important role in uranium adsorption. The competitive adsorption experiment shows that CBCS has excellent uranium adsorption selectivity. In addition, CBCS exhibits good reusability. After five adsorption–desorption cycles, the uranium adsorption rate of CBCS can still reach >98 %. Hence, CBCS has excellent potential for uranium extraction from seawater.

Water-Mediated Hydrogen Bond Network Drives Highly Crystalline Structure Formation of Crown Ether-Based Covalent Organic Framework for Sr Adsorption.

Covalent organic frameworks (COFs) with crown ether units have drawn great attention due to their potential applications in adsorption, catalysis, and sensing. However, employing crown ethers to construct COFs is still challenging in light of the flexible nature of macrocycles. Here, a highly crystalline one-dimensional covalent organic framework (1D-18C6-COF) with crown ether units on the ribbon edge was synthesized. The water-mediated hydrogen bond network and π-π stacking hold the 1D COF ribbons together. The combination of experimental and DFT studies demonstrated that the hydrogen bond network plays a crucial role in the structure crystallinity. The 1D-18C6-COF was applied as an adsorbent for strontium, and it exhibited rapid kinetics with good selectivity. In the competitive adsorption experiment, a separation factor of 1900 was achieved, representing one of the largest values for cesium/strontium separation. This work provides new insights into the design and functional exploration of crystalline COFs with flexible units.

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.

Competitive adsorption law of multi-component gases during CO2 displacement of CH4 in coal seams

The CO2 enhanced coal bed methane recovery technology provides an excellent way to mitigate the greenhouse effect and energy crisis. The features and mechanism of CO2/CH4 competitive adsorption in the coal rock matrix have a critical impact on the production of CBM. For CO2/CH4 competitive adsorption process components and pressure changes, a multi-component gases competitive adsorption experiment was carried out with CO2 and CH4 binary gases as the study objects, and a multi-component adsorption model was developed by the expanded Langmuir equation. Based on the principles of molecular dynamics and thermodynamics, important parameters such as the average free range of gas molecules and adsorption potential are introduced to explain the competitive adsorption behavior from multiple perspectives and explore the competitive adsorption law of CH4 and CO2 under multiple component conditions, so as to provide some theoretical basis and field guidance for improving the extraction effect of CH4 in coal seams. The results show that: Under two critical conditions (100%CO2 +0%CH4 and 0%CO2 +100%CH4), the Langmuir volumes of CO2 for HN 1/3 coking coal and HL weakly caking coal respectively are 2.21 and 3.01 times higher than those of CH4; the overall adsorption capacity of binary gas is in between the adsorption capacities of both critical conditions and increases with increasing CO2 concentration in the gas source ratio; using E-L equation for binary gas component partitioning, the CH4 partition curves were all below CO2, the concentration of free-phase CH4 was always higher than that in the adsorbed phase, and coal samples had stronger adsorption ability for CO2 than CH4. CO2 has a stronger adsorption potential at the surface for HL weakly caking coal. CH4 has a slightly stronger adsorption potential at the surface for HN 1/3 coking coal. The higher coalification degree of the coal sample, the stronger the adsorption ability for CH4 and the weaker the adsorption ability for CO2. The slope of the overall adsorption curve of multi-component gases is analogous to the slope of the component with a high ratio of gas or strong adsorption capacity; the capacity of one-component adsorption for dual gas is closely related to the partial pressure of the free-phase gas and the separation factor α21. When the concentration ratio of CH4/CO2 in free phase is y2/y1 =α21, the concentration of both gases in adsorption phase is 50%, and α21 correlation is weakened, then the free phase gas partial pressure is dominant and there is a threshold value makes CH4 and CO2 adsorption capacity equal; when y2/y1 <α21, the coal preferentially adsorbs CO2 in the binary gas; when y2/y1 >α21, the coal preferentially adsorbs CH4 in the binary gas.

Production of imprinted polystyrene resins for copper ions removal from wastewater

Imprinted resins have attracted much attention for their high contaminant removal and reuse performance. Chloroacetylated polystyrene resins, polyethyleneimine, epichlorohydrin, and Cu(II) were used as support, functional monomer, cross-linker and template, respectively. The ion-imprinted resins (PS-PEI@SIP) and non-imprinted resins (PS-PEI@NIP) were prepared by the combination of amination reactions and surface ion-imprinting technique. The adsorption processes of Cu(II) with PS-PEI@SIP and PS-PEI@NIP followed pseudo-second-order kinetics. The langmuir isothermal adsorption model was consistent with the adsorption curve, indicating that Cu(II) were uniformly adsorbed on the PS-PEI@SIP surface. Thermodynamic experiments showed that the adsorption of Cu(II) by PS-PEI@SIP was a spontaneous process, and high temperature was favorable for adsorption. In addition, the selectivity of PS-PEI@SIP to Cu(II) was confirmed by multi-component competitive adsorption experiments. When Cu(II) mixed with Ni(II), Zn(II) and Cd(II), the selection coefficients of PS-PEI@SIP for Cu(II) were 31.98, 37.19 and 64.27. The results showed that PS-PEI@SIP had high adsorption capacity and good selectivity for Cu(II) ions in mixed ionic solution, and the adsorption capacity was 89.4 mg·g–1. The simulation wastewater dynamic adsorption experiment showed that the PS-PEI@SIP adsorption column could treat 52.8 BV Cu(II) concentration (C＜7.5 mg·g–1), when the influent Cu(II) concentration was 150 mg∙L−1. When 1 mol∙L−1 HCl solution was used for dynamic desorption of PS-PEI@SIP, the desorption rate was more than 92%, indicated that PS-PEI@SIP had good regeneration performance. These results provided basic information for the production of imprinted adsorbent resins.

Theoretical calculation guided molecularly imprinted polymer for selective adsorption of phloroglucinol

Effective adsorption of phloroglucinol (PG) is a method that kills two birds with one stone, which can not only reduce the harm of phenolic wastewater to the environment but also bring considerable economic benefits. In this work, the optimal functional monomer N-Vinyl imidazole (VIM) that possesses the strongest affinity with PG among 11 phenolic monomers was quantitatively selected by DFT calculation. The key factors that influence the adsorption capacity (Qe) and imprinting effect (α) were systematically researched. And the physicochemical property and morphology of the obtained VIM-MIP with the best adsorption performance were explored by a series of characterization methods. The adsorption tests were carried out, indicating that the VIM-MIP exhibited a large adsorption capability (Qe = 81.34 mg/g), which exceeded 78.97 % of the existing optimal absorbents for PG. What’s more, the adsorption data for PG fit in with the Freundlich model (R2 > 0.99). More notably, the excellent PG selectivity of the VIM-MIP was confirmed by competitive adsorption experiments under binary systems (relative selectivity coefficient, 2.014), which was attributed to the existence of imprinted cavities. The molecular simulation, X-ray photoelectron spectroscopy (XPS) analysis, and Zeta potential analysis were employed to reveal the adsorption mechanism, indicating the hydrogen bond was the main driving force.

Adsorption and enrichment of Ag(I) from industrial wastewater using woody biomass-based biosorbent

In this study, a biosorbent prepared by sulphuric acid modified waste biomass was used to adsorb and enrich Ag+ from industrial wastewater. The Ag+ was converted into Ag(NH3)2+ according to the different chemical properties of the ions, as a way to improve the selective adsorption of Ag+ on the biosorbent. Response surface methodology was used to obtain the optimised modification conditions as follows: modification time was 4 h, modification temperature was 368.15 K and sulphuric acid concentration was 85 mass %. Porous structure and chemical functional groups of biosorbent were studied. The analysis of adsorption isotherms indicates that the adsorption process may be an irreversible heterogeneous chemical adsorption process, and the adsorption kinetics of biosorbent on Ag(NH3)2+ conform to the pseudo-second-order kinetic model. The redox mechanism of Ag(NH3)2+ adsorption was postulated based on characterisation analysis. The competitive adsorption experiments showed that the biosorbent had selective adsorption for Ag(NH3)2+ due to redox reaction, and the adsorption capacity of the biosorbent on Ag(NH3)2+ was 1285 mg g−1, which indicates that it has good prospects for application in recovery of Ag(I) from liquid waste resources in the future.

Competitive adsorption of sulfamethoxazole and bisphenol A on magnetic biochar: Mechanism and site energy distribution

Competitive adsorption and complementary adsorption between emerging pollutants has been observed in multiple studies. Investigation of the preference of pollutants for different types of adsorption sites can provide a supplementary perspective for understanding complementary adsorption. In this study, the simultaneous adsorption of two typical emerging pollutants, sulfamethoxazole (SMX) and bisphenol A (BPA), on magnetic biochar (MBC-1) was investigated. The results showed that the modification with ferric chloride optimized the surface properties of biochar (aromaticity, hydrophobicity, and oxygen-containing functional groups, etc.), and helped to remove SMX and BPA through various interactions. The equilibrium adsorption capacity of the two adsorbents was inhibited by competitive adsorption in the mixed solute systems, which was due to the same adsorption mechanism. When pH = 7, the SMX and BPA adsorption mainly involved pore filling, hydrophobic effect, π-π EDA, and hydrogen bonding. In addition, electrostatic force, surface coordination, and ion exchange have also been proven to be related to the adsorption of SMX and BPA. In the co-adsorption system, BPA's competitive advantage might be due to its superior hydrophobicity, charge property, and molecular diameter. In the competitive adsorption experiment, the total adsorption capacity (Qi) of the competitive solute exceeded the adsorption inhibition (△Qi) of the main solute, indicating that the two solutes occupied their preferred adsorption sites, which confirmed the complementary adsorption phenomenon. Complementary adsorption can be explained by the preference of SMX and BPA for different types of adsorption sites. BPA preferentially occupied high-energy sites in the co-adsorption system, such as π-π EDA interaction, ion exchange, and surface coordination. At the same time, SMX tended to be removed by hydrophobic interaction and hydrogen bonding.

A novel strategy of post defect modification (PDM) for synthesizing hydrophobic FA-UiO-66-CF3 with enhanced n-hexane vapor adsorption capacity under humidity

Volatile organic compounds (VOCs) are hard to recover due to the existence of large amounts of water vapor in practical conditions by adsorption method. Given the abundant functional groups of metal-organic frameworks (MOFs), especially –NH2 group, which can be easily functionalized to solve this problem. However, their pore apertures of the modified MOFs are constricted after post synthesis modification (PSM), leading to unsatisfied adsorption capacity under high humidity. In this work, we proposed a novel strategy of post defect modification (PDM) to synthesize high-performance hydrophobic MOFs for improving adsorption performance under humidity. Originally, the defect-rich UiO-66-NH2 was prepared by using different monocarboxylic acids (MA). In particular, the sample FA-UiO-66-NH2, obtained by the addition of formic acid (FA), exhibited strong n-hexane vapor adsorption ability (198 mg·g−1), which was 97% larger than the non-defective UiO-66-NH2. Afterwards, the defect-engineered FA-UiO-66-NH2 was decorated with –CF3 groups for improving its hydrophobicity, which showed superhydrophobicity with a water contact angle (WCA) of 151.6° and decreased (60%) water vapor adsorption capacity. Dynamic competitive adsorption experiments also indicated that the FA-UiO-66-CF3 sample is more superior competitive adsorption performances for n-hexane vapor than water vapor. Furthermore, we provide a novel strategy for constructing defect-engineered and functionalized MOFs, which will expand their application fields.