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Nowadays, numerous studies have focused on the newly developed technologies for the thorough removal of tetracyclines (TCs). The efficient removal of trace-amount pollutants requires the development of improved materials with higher adsorption capacity and increased adsorption selectivity. Zn(II)-mediated chitosan nonwoven fabric (Zn-CSNW) adsorbent with coordination capability was explored for the effective and selective removal of TC. The adsorption of TC to Zn-CSNW could reach equilibrium in about 30 min with a maximum adsorption capacity of 195.9 mg/g. It exhibited high anti-interference performance for TC adsorption at low concentrations, with good regeneration and effective reuse. Except for citrate, organic materials similar in structure to TC or common ions in aqueous solutions did not show obvious competition for the adsorption of low concentrations of TC. Additionally, the inherent fluorescence of chitosan and the fluorescence sensitization effect of Zn2+ for TC enabled function of Zn-CSNW as an indicator of the adsorption of TC by changes in fluorescence color and intensity under UV light (365 nm). It can indicate the saturation state of the Zn-CSNW, which will bring convenience to the use of the adsorbent. The Zn(II)-mediated coordination interaction plays a vital role in both the selective recognition of TC and the fluorescence sensing of adsorption amount, demonstrating an affordable and effective strategy for the treatment of water containing low amounts of antibiotics.

This study aimed to develop a highly selective extraction protocol for gold (AuIII) ions from electronic urban waste (EUW) using simple, low-cost Inorganic-organic mesoporous hybrid segregators. The unique features of mesoporous hybrid segregator architectures are of particular to ensure effective adsorption system in terms of selective and sensitive recovery of AuIII ions from EUW. The segregator platform featured 3D micrometric, mesocage double-serrated plant-leaf-like γ-Al2O3 sheets with hierarchy surfaces containing tri-modal mesopores interiorly and uniformly arranged toothed edges of ~20–40 and ~15 nm groove width and depth at the exterior surfaces, respectively. Rational incorporation of actively organic chelates into hierarchical γ-Al2O3 sheet platforms leads to the production of a couple of selective segregators 1 and 2 (namely, SC1 and SC2) for AuIII ions at specific conditions by applying batch and fixed-bed columnar techniques. The mesocage SC segregators offer a selective extraction approach of AuIII ions from mixed element contents released from a computer motherboard (CMB). Our finding indicated that the textural and hierarchal features of the mesocage SC segregators played key roles in the selective adsorption/recovery of AuIII ions at pH 2–2.5 with high capacity (136–141 mg/g range) and effective reusability ≫10 consecutive cycles. In general, the developed SCs could be utilized as a real extractor of AuIII recovery from spent CMBs.

Antibiotic residues from animal wastes enter underground and surface water streams, posing high risks to public health. Novel technologies capable of removing the residues from the matrix of concern such as animal waste should be developed. This research investigates the development of nanofiber absorbent for removing tetracycline (TC) antibiotic residues from liquid streams of dairy manure produced in a typical dairy farm. Hierarchically structured nanofibrous adsorbent was developed through growing a uniform polyaniline (PAni) nanodots on poly (vinyl alcohol-co-ethylene) (EVOH) nanofiber membrane (NFM). Moreover, Cu2+ ions were chelated on the developed EVOH/PAni-Cl NFM to improve TC adsorption efficiency and selectivity. The TC adsorption capacities of EVOH/PAni-Cl-Cu2+ and EVOH/PAni-Cl) NFM were 1100 mg g−1 and 600 mg g−1 within 120 min., respectively. The NFMs adsorption efficiency was investigated using dairy wastewater. Initial TC concentrations in dairy wastewater sample varied between 20 and 50 ppm. The EVOH/PAni-Cl-Cu2+ NFM showed TC removal of 86% from dairy manure samples at 25 ppm initial TC concentration within 60 min. during batch mode treatment. Results showed that the dynamic binding efficiency of 450 mg g−1 can be achieved at an initial TC concentration of 50 ppm. Furthermore, the NFM displayed efficient chemical and physical stability even after 8 cycles of reusing without significant changes in its performance or hazardous Cu2+ leaching.

Organic dye-containing wastewater has become an increasingly serious environmental problem due to the rapid development of the printing and dyeing industry. Hydrogel is a promising adsorbent for organic dyes because of its unique three-dimension network structure and versatile functional groups. Though many efforts have been made in hydrogel adsorbents recently, there is still a critical challenge to fabricate hydrogel adsorbent with high adsorption capacity and high efficiency at the same time. To address this concern, we developed a calcium hydroxide nano-spherulites/poly(acrylic acid -[2-(Methacryloxy)ethyl]trimethyl ammonium chloride) hydrogel adsorbent with novel villi-like structure. The hydrogels were prepared through a simple free radical copolymerization method using calcium hydroxide nano-spherulites as crosslinker. The resultant hydrogel adsorbents showed a maximum adsorption capacity of 2249 mg/g in a 400 mg/L methylene blue solution and a high removal ratio of 98% in 1 h for a 50 mg/L methylene blue solution. In addition, the adsorption behaviors of our hydrogel adsorbents could be well described by pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Furthermore, this kind of hydrogel adsorbent showed selective adsorption behavior for methylene blue. Altogether, the hydrogel adsorbent developed in this work has a high capacity and high efficiency in organic dye removing and promised a great potential in wastewater treatment application.

Hypothesis The construction of novel functional cyclomatrix polyphosphazenes (CPPs) hybrid, which with diverse decorating groups, is a challenging task due to the structural limitation of available reaction substrates (phenols and amines). Experiments Herein, a phenolic hydroxyl ( OH) modified ployamide derivative (P2) was successfully prepared via novel benzoxazine-isocyanide chemistry (BIC). A kind of CPP hybrid (P3), which with abundant functional groups (amide, tertiary amine, benzoxazine and phenolic hydroxyl) was prepared subsequently by the condensation between P2 and hexachlorocyclotriphosphazene (HCCP). Chemical structure, elemental composition, morphology, porous properties and crystallinity of P3 were systematically analyzed here. The electrochemical detection of lead ion (Pb2+) was realized by using P3-modified glassy carbon electrode (GCE/Nafion/P3) as the working electrode. Besides this, given the unique chemical structure and morphology of P3, the selective adsorption of methylene blue (MB) by P3 was also studied here. Findings Experimental results indicated that that P3 can act as bifunctional hybrid material to solve environmental issues.

This research focused on the adsorption features and depression mechanism of 1-hydroxyethylene-1,1-diphosphonic acid (HEDP) used as a novel dolomite depressant on dolomite and magnesite surfaces, to extend the application of HEDP for the selective flotation of magnesite from dolomite. The depression impacts of HEDP on the flotation behaviors of the two minerals were investigated through micro-flotation tests. The flotation results indicated that, when sodium oleate (NaOl) was used as the collector, HEDP displayed an outstanding depression effect on the dolomite flotation, whereas it had only a slight influence on the magnesite flotation. Dolomite and magnesite could be efficiently separated at approximately pH 10 with a reagent scheme of 200 mg/L HEDP and 120 mg/L NaOl. The selective depression mechanism of HEDP for dolomite was revealed using contact angle, X-ray photoelectron spectroscopy (XPS), zeta potential, and infrared spectrum (IR) analyses. The results from the contact angle tests indicated that HEDP selectively reduced the surface hydrophobicity of dolomite in the NaOl system. Besides, zeta-potential measurements and IR analyses revealed that the addition of HEDP prior to NaOl had no significant impact on the adsorption of NaOl onto magnesite; however, this addition strongly prevented NaOl from being adsorbed onto dolomite, resulting in a significant difference in the flotation performances of the two minerals. Furthermore, crystal chemistry calculations and XPS analyses confirmed that the strong adsorption of HEDP on the dolomite surface could be attributed to the interaction between the HEDP electron-rich groups and the calcium species exposed to dolomite. Thus, HEDP could be used as a high-performance depressant for the dolomite flotation to realize the decalcification of the magnesite flotation.

Linear polyimides of intrinsic microporosity have been intensively investigated for gas separation due to their microporous structure and high surface area. The microporous structure in the linear polyimides of intrinsic microporosity comes from their contorted structure. Therefore, most linear polyimides without contorted structure do not have micropores. In this work, the microporous polyimides are constructed through the condensation of a cross-linkable dianhydride monomer with two novel nitrogen-rich diamine monomers and post crosslinking reaction. The linear polyimide precursors without contorted structure have the same main-chain structure. The introduction of crosslinked structure endow the crosslinked polyimides (PI-CLs) with microporous structure. The microporous structure in PI-CLs can be tuned by changing the substituents of the linear polyimide precursors. The PI-CLs have competitive CO2 uptake capacity (7.3–9.4 wt%) at 273 K and 1 bar. Particularly, the crosslinked polyimide containing trifluoromethyl groups (CF3-PI-CL) shows high CO2/N2 and CO2/CH4 selectivity (72 and 22) at 273 K, which are among the best results for reported porous materials. This work reveals that the introduction of crosslinked structure and changing substituents is an efficient method for constructing microporous polyimides with abundant micropores and excellent CO2 selective adsorption capacity. This method also has great potential for fabricating high-performance microporous polymers based on other linear polymers without rigid contorted structure.

Conventional techniques like electrodialysis, evaporation concentration cannot efficiently and selectively separate valuable heavy metals ions (VHMI) from electroplating rinse wastewater due to VHMI’s low concentration and other ions’ competitive adsorption. To realize the separation, a coupling technology was proposed which combines capacitive deionization (CDI) technique suitable for separating low-concentration ions and the few-layer molybdenum disulfide/N-doped carbon spheres (FL-MoS2/NCS) composite capable of selectively adsorbing copper ions (Cu2+), a representative VHMI. The FL-MoS2/NCS composite was successfully prepared by one-pot method and used as the cathode and anode in a CDI cell. Electrosorption experiments in the CDI cell showed that the FL-MoS2/NCS electrode (cathode) can efficiently adsorb low-concentration Cu2+ (23.63 mg/L) with a saturated adsorption capacity of 1199.63 mg/g at 0.8 V. In the competitive environment (Cu2+/Na+/Fe3+), the FL-MoS2/NCS electrode can selectively adsorb Cu2+ still with a high adsorption capacity of 1071.6 mg/g greatly outnumbering that of Na+ (199.2 mg/g) and Fe3+ (262.8 mg/g), despite the high concentrations of both NaCl (500 mg/L) and FeCl3 (80 mg/L). Furthermore, the XPS test and competitive adsorption results proved that the efficient and selective adsorption of the FL-MoS2/NCS electrode for Cu2+ was synergistically promoted by electrical double layer (EDL) and complexation of Cu2+ with FL-MoS2/NCS.

Although adsorbents can effectively remove phosphate from water, most are difficult to separate from water and their phosphate removal efficiencies are adversely affected by coexisting anions or humic acid. Here, a magnetic core–shell composite with Fe3O4 as the core and carbon as the shell (denoted as MFC) was functionalized with a metal–organic framework, UiO-66, and its phosphate adsorption ability was studied. The composite (denoted as MFC@UiO-66) was effectively separated from water within 1 min under an external magnetic field. The kinetics of phosphate adsorption onto MFC@UiO-66 was controlled by the intraparticle diffusion process, suggesting that the Zr in UiO-66 played an important role in phosphate adsorption. The isotherm for phosphate adsorption onto MFC@UiO-66 was well described by the Freundlich model. The adsorbent exhibited higher affinity toward phosphate than toward coexisting anions (e.g., Cl−, NO3−, and SO42−), reflecting high phosphate adsorption selectivity. The adsorption affinity of MFC@UiO-66 to phosphate increased with the increasing temperature, but decreased with increasing pH. The presence of dissolved humic acid negligibly affected phosphate adsorption onto MFC@UiO-66 because of its size-exclusion effects. The used adsorbent was easily regenerated with NaOH solution, and the sorbent displayed stable phosphate adsorption behavior after five regeneration cycles.

The combination of the molecular imprinting technology and porous materials is a promising way to obtain high-efficient selective adsorption and separation materials for bioactive macromolecules. In this work, we developed a novel approach to prepare near-infrared (NIR)-light-response inverse-opal lysozyme (Lyz)-imprinted polydopamine/polypyrrole (IO-PDA/PPy-MIP) composite microspheres using micron-sized SiO2 colloidal crystal microspheres as the sacrificed template. The pore size of the IO-PDA/PPy-MIP microspheres can be tuned from 200 to 800 nm by the size of silica nanoparticles which self-assemble to form the template SiO2 colloidal crystal microspheres. The IO-PDA/PPy-MIP microspheres show a rapid selective adsorption ability for Lyz due to the inverse-opal macroporous structure. The adsorption capacity exceeds 800 mg/g within 20 min, and the imprinting factor is as high as 24. The bound Lyz molecules can be released rapidly from IO-PDA/PPy-MIP microspheres triggered by the irradiation of NIR laser and remain enough bioactivity to decompose Escherichia coli efficiently. The prepared IO-PDA/PPy-MIP microspheres also exhibit excellent structure stability and good recyclability. The adsorption capacity can remain up to 90% of the initial value after 5 times recycle. This work provides not only a method to prepare novel NIR-light-response inverse-opal macroporous molecularly imprinted microspheres, but also a new perspective on the design of selectively separation materials for the fast, high-efficient recognition and separation of biomacromolecules.

The linear O-carboxymethyl-β-cyclodextrin polymer functionalized-amino single walled carbon nanotubes (LCMP-β-CD-ASWCNTs) supramolecular carbon nanofiber was prepared via amidation reaction. Surprisingly, AFM analysis indicated the width of the prepared well-defined supramolecular carbon nanofibers (SCNFs) was over 120 nm. Meanwhile, the height of the LCMP-β-CD-ASWCNTs supramolecular carbon nanofiber is within 26.5 nm, which is 1.36 times higher than that of pristine ASWCNTs. Additionally, SEM and HRTEM analysis indicated that the linear O-carboxymethyl-β-cyclodextrin polymer (LCMP-β-CD) molecules were anchored on amino single walled carbon nanotubes (ASWCNTs) and fully cover its surface. We observed that the specific surface area of LCMP-β-CD-ASWCNTs supramolecular carbon nanofibers was 679.3 m2/g, while that of pristine ASWCNTs was 113.5 m2/g. As expected, the specific surface area of LCMP-β-CD-ASWCNTs supramolecular carbon nanofibers was 6-fold larger compared with that of the pristine ASWCNTs. More importantly, LCMP-β-CD-ASWCNTs supramolecular carbon nanofiber possesses selective adsorption capacity for organic pollutants. Besides, the regeneration sorption and desorption experiments showed that the LCMP-β-CD-ASWCNTs supramolecular carbon nanofibers possessed good reproducibility and durability. Overall, these results indicated that the LCMP-β-CD-ASWCNTs supramolecular carbon nanofibers could potentially serve as selective adsorption material.

Core-shell structured NH2-functionalized UiO-66 magnetic composites (γ-Fe2O3@C@UiO-66-NH2) were fabricated via a simple, facile and green approach to investigate their adsorption behaviors towards different organic dyes (methylene blue, malachite green, acid fuchsin and acid orange II). Different characterization methods containing XRD, TEM, EDXA, FTIR, BET and XPS were used to indicate that the as-prepared γ-Fe2O3@C@UiO-66-NH2 material exhibited core-shell structure and excellent surface performance. Adsorption experiments showed that γ-Fe2O3@C@UiO-66-NH2 could selectively adsorb anionic dyes and effectively separate the mixture, which might be mainly ascribed to the negatively-charged anionic dyes as opposite to the positively-charged Zr metal sites in γ-Fe2O3@C@UiO-66-NH2. The kinetics and adsorption isotherm of acid orange II and acid fuchsin adsorption in γ-Fe2O3@C@UiO-66-NH2 were also investigated. For acid orange II and acid fuchsin, the maximum adsorption capacity obtained from the Langmuir isotherm model was 48.12 mg/g and 31.54 mg/g, respectively. Moreover, γ-Fe2O3@C@UiO-66-NH2 exhibited good structural stability and reusability, which suggesting that γ-Fe2O3@C@ UiO-66-NH2 as an easy-prepared adsorbent material exhibited great application potential in the selective removal of dyes from water systems.

Mg/Fe layered double hydroxide loaded with Magnetic(Fe3O4) carbon spheres (MCs@Mg/Fe-LDHs) was firstly synthesized by a facile in-situ co-precipitation method to remove Pb(II) and Cu(II) pollution. To search the adsorption mechanism, MCs@Mg/Fe-LDHs was characterized by XRD, FTIR, XPS, TEM, and BET. There may exist surface complexation, precipitation, isomorphic substitution and physical adsorption in MCs@Mg/Fe-LDHs. The combination of those four types of reactions/interactions of metal ions with composite could improve the removal of Pb(II) and Cu(II). And the surface complexation was the main factor leading to the difference maximum adsorption capacity of Pb(II) (3.66 mmol/g) and Cu(II) (5.33 mmol/g). The adsorption kinetics and adsorption thermodynamics of MCs@Mg/Fe-LDHs for Pb(II) and Cu(II) could be better described by pseudo-second-order model and Langmuir model, respectively. The adsorption reaction was a spontaneous and endothermic process. Moreover, there existed competitive effect between Pb(II) and Cu(II) on the co-adsorption by MCs@Mg/Fe-LDHs. And the selectivity adsorption order of MCs@Mg/Fe-LDHs is as follows: Cu(II) > Pb(II) > Zn(II) > Ni(II) > Cd(II). Besides, in the real river water, the MCs@Mg/Fe-LDHs also exhibited stable adsorption capacity for Pb(II). In general, the MCs@Mg/Fe-LDHs has the potential for purification of water contaminated by Pb(II) and Cu(II).

The removal of acetylene from ethylene is of vital significance in the petroleum and chemical industry, the presence of trace acetylene impurities in ethylene polymerization process could lead to the interruption of ethylene polymerization. Herein, we construct a new anionic porous organic polymer using potassium tetraphenylborate via Friedel-Crafts alkylation reaction under mild conditions. The resulting material, APOP, possesses good thermal stability and a decent BET surface area, as exemplified by thermogravimetric analysis measurement and nitrogen gas sorption experiment. Acetylene and ethylene adsorption isotherms reveal that APOP has a higher adsorption capacity of acetylene than that of ethylene under same conditions. Ideal adsorbed solution theory calculations and breakthrough experiments both demonstrate that APOP is capable of selective adsorption of acetylene over ethylene. To the best of our knowledge, APOP represents the first anionic porous organic polymer material capable of selective adsorption of acetylene over ethylene, and the exploration of APOP may provide a new way for these key gas separations using ionic porous organic polymer materials.

Hypothesis: Salivary pellicles i.e., thin films formed upon selective adsorption of saliva, protect oral surfaces against chemical and mechanical insults. Pellicles are also excellent aqueous lubricants. It is generally accepted that reconstituted pellicles have a two-layer structure, where the outer layer is mainly composed of MUC5B mucins. We hypothesized that by comparing the effect of ionic strength on reconstituted pellicles and MUC5B films we could gain further insight into the pellicle structure.\ud \ud Experiments: Salivary pellicles and MUC5B films reconstituted on solid surfaces were investigated at different ionic strengths by Force Spectroscopy, Quartz Crystal Microbalance with Dissipation, Null Ellipsometry and Neutron Reflectometry.\ud \ud Findings: Our results support the two-layer structure for reconstituted salivary pellicles. The outer layer swelled when ionic strength decreased, indicating a weak polyelectrolyte behavior. While initially the MUC5B films exhibited a similar tendency, this was followed by a drastic collapse indicating an interaction between exposed hydrophobic domains. This suggests that mucins in the pellicle outer layer form complexes with other salivary components that prevent this interaction. Lowering ionic strength below physiological values also led to a partial removal of the pellicle inner layer. Overall, our results highlight the importance that the interactions of mucins with other pellicle components play on their structure.

Bacterial anchoring to limestone rocks is thought to occur by selective adsorption of biomolecules found in the extracellular matrix, such as polysaccharides. Here we study the adsorbed structure of a model matrix polysaccharide, sodium alginate, at the calcite/water interface using neutron reflection (NR). Sodium alginate was found to form highly hydrated layers extending up to 350 angstrom into solution at concentrations up to 2.5 ppm (the inflection point of the adsorption isotherm). The adsorption of alginate was driven by dissolution of the calcite surface through complexation of free calcium ions. This was shown using two alginates with differing ratios of sugar residues. Alginates with a higher proportion of guluronic acid (G) have a higher affinity for calcium ions and were found to cause the surface to dissolve to a greater extent and to adsorb more at the surface when compared to alginates with a higher proportion of mannuronic acid (M). Adding magnesium to the high G alginate solution reduced dissolution of the surface and the adsorbed amount. In this work, we have shown that polysaccharide adsorption to sparingly soluble calcite interfaces is closely related to polymer conformation and affinity for free calcium ions in solution. (C) 2020 Published by Elsevier Inc.

In this work, we applied a novel dithiocarbamate-grafted star-like polymer for efficient reclamation of cationic dyes. This material is highly selective towards cationic dyes and almost completely rejective to anionic dyes. The adsorption kinetics, isotherms, and thermodynamics were systematically investigated to analyze the adsorption behavior of cationic dyes onto the material. As compared with other reported adsorbents, this cheap and facilely-prepared material has exceptional adsorption capacities for industrial cationic dyes, e.g., methylene blue (MB, 2624 mg/g), crystal violet (CV, 2553 mg/g), basic fuchsin (BF, 1729 mg/g), and methylene violet 3RAX (MV, 1239 mg/g), being 5–11 times of that reported in literatures. Based on the effects of pH and ionic strength on adsorption, competitive adsorption of the cationic dyes, and FTIR characterization, mechanisms for the adsorption and desorption of cationic dyes were proposed. The adsorbed dyes can be recovered over 95% just by immersing into diluted HCl solution (0.01 M) for 10 min, thus avoiding organic solvent extraction. Over 98% of the adsorption capacity was maintained during consecutive reclamation operation. Due to the high selectivity, high adsorption capacity and the ease of efficient regeneration, this material is potentially applicable for targeted reclamation of cationic dyes from dyeing wastewater.

The treatment of organic pigments has gained significant attention worldwide owing to the large amounts of pollutants emitted during the process. The main purpose of this study is to prepare an environmentally friendly, low-cost adsorbent with high efficiency with selective adsorption for water purification. An inorganically modified mesoporous biochar derived from sorghum straw was synthesized in one step, and three typical organic pigments including methyl blue (MB), acid orange 7 (AO7), and alizarin red (AR) were selected as cationic, azo, and anionic pigments, respectively. The characterization results demonstrated that Fe3O4 particles successfully attached to the surface of biochar after modification. Although the enhanced adsorption behaviors of the three pigments on the modified biochar were described effectively by the Langmuir isotherm, the as-prepared materials showed a better selective adsorption effect on the cationic pigments. Moreover, the adsorption processes of all targeted pigments were endothermic and governed by entropy. Smaller molecular dimensions, lighter molecular weight, and the low molecular electrostatic potential of MB are responsible for its selective adsorption; however, the enhanced adsorption affinity is attributed to the hydrogen bond and n-π interaction with the benzene ring of the pigment molecules.

Hydrogels induced by two-component gelator isomers based on the different amine/acid interactions were investigated. Scanning electron microscopy and atomic force microscopy images of the xerogel obtained from the two hydrogels revealed different assembly morphologies. While left-handed helical fibers were observed for the amine-acid based xerogel, acid-amine underwent self-assembly to afford smooth fibers. Fourier transform infrared spectroscopy, fluorescence, and X-ray diffraction measurements combined with density functional theory calculations suggested that the different self-assembly patterns of gelators resulted in opposite electric charges on the xerogel surfaces, in line with Zeta potential measurements. Based on these opposite charges resulting from their different self-assemblies, both xerogels demonstrated efficient dye adsorption abilities with different selectivities. Interestingly, the adsorption performance was not influenced by the salt in the dye solution. Furthermore, the xerogels still showed high dye adsorption efficiency after four cycles. These results provide a two-component hydrogel method for the purification of dye-polluted water systems, while also paving the way for future design of functionalized supramolecular self-assembly systems.

To address the pollution problem of organic dyes, monodispersed anionic silver nanoparticles (AgNPs) with an average size of 6 nm were prepared in water media via chemical reduction method from oleic acid and n-butyl amine. The aqueous solution of the resultant AgNPs was utilized as a photocatalyst to investigate the adsorption and photodegradation behaviors of organic dyes under different light irradiation. The morphology and surface characteristics of the synthesized AgNPs were probed using TEM, XRD, FTIR and zeta potential analysis. The adsorption and degradation process of organic dyes on the AgNPs were characterized in details by UV–Vis spectrophotometer. The results showed that the AgNPs exhibited a characteristic charge- and size-selective adsorption of dyes owing to the profoundly negative charged surface, which enables the AgNPs to possess high selective degradation of Methylene Blue. More still, due to the surface plasmon resonance (SPR) effect of AgNPs, the obtained AgNPs presented a higher photocatalytic activity to Methylene Blue under UV light, visible light, and solar light compared with commercial photocatalysts. The 5 cyclic reactions revealed its high stability and reusability. In a nutshell, the proposed mechanism systematically combined the selective adsorption and the SPR effect to explain the detailed photocatalytic process of the obtained AgNPs.

Yolk-shell structured C@Li4Ti5O12 microspheres composed of carbon core (ca. 500 nm) and sea urchin-like Li4Ti5O12 shell (ca. 400–500 nm) are formed by hydrothermally treating the core–shell structured C@TiO2 in the EtOH/H2O solution of LiOH and calcining it in N2 atmosphere. Yolk-shell structured TiO2-type lithium ion sieve is further transformed from C@Li4Ti5O12 through the acid treatment, which have a high specific surface area of 201.74 m2/g. The composite shows adsorption capacity towards Li+ proportional to the pH value in the range of 7–13. The adsorption reaches equilibrium within 2 h with a high equilibrium adsorption capacity of 28.46 mg/g under alkaline conditions, which is ca. 8 times the value of ordinary TiO2 lithium ion sieve with comparable size and surface area, demonstrating the enhanced adsorption is attributed to the generation of more accessible surficial voids by replacing internal part with light carbon core. The adsorption follows Freundlich and pseudo-second-order kinetic models with a high rate constant of 0.015 g/(mg·min). The selective adsorption to Li+ is verified in the presence of K+, Na+, Ca2+ and Mg2+.

Selective adsorption of tannic acid (TA) on calcite surfaces and the implications of this process for the separation of fluorite ore were studied by microflotation tests, surface adsorption experiments, zeta potential measurements, UV-vis analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The microflotation tests indicated that TA, when added before sodium oleate (NaOl), could selectively depress calcite from fluorite at pH 7. Surface adsorption experiments revealed that TA hinders the interaction of NaOl with calcite. The zeta potential of calcite became more negative with TA than with NaOl. However, the characteristic features of TA adsorption were not observed on fluorite, suggesting that the dominant adsorption sites are dissimilar on the fluorite and calcite surfaces in the pulp. UV-vis spectroscopy, XPS, and solution chemistry analysis were utilized to obtain a better understanding of the mechanism for selective adsorption of TA as well as the key factors determined by the Ca2+ and Ca(OH)+ components on the mineral surfaces. A possible adsorption mechanism along with an adsorption mode is proposed for the surface interaction between TA and calcite.

Zeolitic imidazolate frameworks-67 (ZIF-67) was prepared via electrochemical deposition, which was used to conduct adsorptive removal of various organic dyes. The results revealed that ZIF-67 displayed good adsorption performance towards some dyes due to its positive Zeta potential at wide pH range or some special functional groups like SO3 of dyes. Also, ZIF-67 could separate some dyes from the matrix subjected to its preferential uptake towards certain dyes. The possible adsorption mechanism including electrostatic interactions, coordination interactions and hydrogen bonding interactions was proposed and tested.

In this work, a novel method for the quantitative determination of defects on graphene surfaces has been presented in order to provide accurate, reliable and quantitative information for the defects on graphene products. It was based on the selective adsorption of a specific polar organic ion (Sodium benzenesulfonate) on the edges and defects on graphene surfaces, and the atomic force microscopy (AFM) imaging of the adsorption. By means of an image processing software, the AFM images could be analyzed and the areas as well as area percentages of the defects on the graphene surfaces could be determined.

Graphene oxide (GO) has great potential in metal recovery and water purification owing to their high surface area, abundant hydroxyl ( OH) and carboxyl ( COOH) groups. To fully understand the influence of the dispersity of GO on the adsorption capacity of metal ions, a series of polyacrylic acid (PAA) functionalized GO (PAA/GO) composites with different dispersity were prepared. The charge density of the PAA/GO composites were much higher than that of the untreated GO in acidic conditions, demonstrating a significant improvement of dispersibility by introducing PAA on the surfaces. Moreover, recovery of gallium by employing the PAA/GO composites as adsorbent were studied. The maximum adsorption capacity towards gallium ions of the adsorbent can reach 196.84 mg·g−1, much higher than that of other commercially available resins (CL-P204, P507). This superiority could be attributed to the abundant COOH groups on the surfaces and the good dispersity of the PAA/GO composites. These results revealed that the PAA/GO composites could be promising adsorbents for selective adsorption and efficient recovery of Ga(III).

Organic dye pollution in the water environment is a problem of global concern. Adsorption is demonstrated as a promising technology to remove organic dyes from wastewater, in which the development of highly-efficient adsorbents is still the challenging task. Herein, we reported the facile fabrication of polyamine-based cyclophosphazene hybrid (PCP-NH2) hollow microcapsules with cross-linked structure, generated by one-step precipitation polymerization between hexachlorocyclotriphosphazene and branched polyethyleneimine, and subsequent acetone treatment. Their morphology, composition and structure were confirmed by SEM, TEM, FTIR, TGA, and XPS. The endowment of hollow PCP-NH2 microcapsules as potential adsorbents were thoroughly evaluated using eight organic dyes with different surface charges. The adsorption action of hollow PCP-NH2 microcapsules highly depends on the surfaces charges, exhibiting highly-efficient and selective adsorption behavior towards anionic dyes. Especially, The adsorption capacity of the hollow PCP-NH2 microcapsules towards anionic dyes of EY, ACBK, MO and EB reaches up to 1196.36, 1190.65, 1142.77 and 1040.92 mg/g at 25 °C, respectively. The adsorption kinetics shows a better fit to pseudo second-order kinetic model, compared to pseudo-first-order kinetic and Weber’s intraparticle diffusion models. The adsorption equilibrium data followed the Langmuir isotherm well. The adsorption thermodynamic experiments demonstrated that adsorption was a physisorption process with endothermic and spontaneous characteristic.

Selective adsorption and regeneration of adsorbents are great challenges for fluoride removal in drinking water. In this study, a NiAl-layered metal oxide (NiAl-LMO) electrode was successfully prepared and used as an electro-adsorption electrode. With its structural memory effect for anions and high specific capacitance of 575 F·g−1, the NiAl-LMO electrode exhibits capacitive deionization performance. The maximum adsorption capacity of F− by the electrode reached 49.28 mg/g, which was 4 times that of Cl− and 2 times that of SO42−, respectively. The good selectivity for F− electrosorption was ascribed to the high electronegativity of F− and the complexation between F− and hydroxyl aluminum groups. The electrode material has good stability and can be regenerated easily by applying a reverse voltage. After 10 cycles, the F− adsorption rate by the NiAl-LMO electrode was 94. 4% of the initial adsorption rate. The applied voltage enhanced the selectivity of F− adsorption by the NiAl-LMO electrode, and this electrosorption process was mainly dominated by electrical double layer adsorption. Under the conditions of 1.0 V and pH 7, the electrode showed a maximum adsorption efficiency of 73.5%.

Aluminum hydroxide and oxide have been widely used for decontamination due to their environmentally friendly nature and cost effectiveness. Aluminum (hydro) oxides are the main phases of aluminum-derived environment materials. Herein, the solvent-free hydrothermal synthesis of gamma-aluminum oxide (γ-Al2O3) nanoparticles and phase transformation of AlOOH into γ-Al2O3 are reported. Hydrothermal treatment of NH3·H2O-induced aluminum precipitate resulted in the formation of AlOOH, which was an intermediate product of γ-Al2O3. AlOOH was transformed into highly crystalline 20-nm γ-Al2O3 particles through calcination at 500 °C due to dehydration. The transformation was confirmed through X-ray diffraction (XRD) and thermogravimetric (TG) analyses. The resulting γ-Al2O3 had superior adsorption ability for the anionic Congo red (CR) dye than for the cationic methylene blue (MB) and malachite green (MG) dyes. The selective adsorption ability of CR instead of MB was attributed to the electrostatic attraction and hydrogen bonds between the amino group and azo double bond of CR, and between the amino group and hydroxyl group in γ-Al2O3. Thus, this study investigated crystalline phase transformation into γ-Al2O3 and selective adsorption capacity of CR, which provides important information regarding the synthesis of crystalline γ-Al2O3 adsorbent, with selective adsorption ability for decontamination applications.

The adsorbents with high adsorption capacity are in urgent demand for water treatment because of the global freshwater crisis. In this work, the copolymer of acrylic acid and methyl methacrylate was synthesized at first, and subsequently blended with polyethersulfone (PES) with different mass ratios to prepare functionalized PES nanofibrous membranes via one-step electrospinning method. Benefiting from the abundant carboxyl groups, as well as the large specific surface area and high porosity, the nanofibrous membranes exhibited a maximum adsorption capacity of 2257.88 mg g−1 for methylene blue (MB) dyes, which was among the largest adsorption amount of those previously reported adsorbents. In addition, the adsorption process was systematically investigated under various conditions, including pH, initial MB concentrations and contact time. Meanwhile, the pseudo-second-order model and Langmuir isotherm model was very suitable to describe the adsorption kinetics and isotherm, respectively. Moreover, the nanofibrous membranes also exhibited excellent recyclability (81.45% after 5 cycles), high filtration-purification efficiency (above 99%, at a high flux of 100 mL min−1) and selective adsorption and separation abilities. These excellent performances endow the nanofibrous membranes with promising potential applications for dye wastewater treatment.

Synthesis of adsorbents that simultaneously possess high adsorption performance and convenient separation characteristic remains a big challenge. Herein, we report a viable strategy to prepare hyperbranched polyglycerol (HPG)-based multi-carboxylic magnetic gel (MMG) based on the thiol-ene click chemistry. The obtained HPG-based MMG adsorbent with porous structure and multiple carboxylic groups not only exhibited fast adsorption rate, superior adsorption capacity, and favorable adsorption selectivity towards cationic dyes (e.g., methylene blue (MB) and methyl violet (MV)) but also presented convenient magnetic separation characteristic. The adsorption data showed nice correlation with pseudo-second-order kinetic model and Langmuir isotherm. The optimal adsorption capacity of HPG-based MMG for MB and MV can reach as high as 458.7 and 400.0 mg g−1, respectively. Moreover, the dye-adsorbed HPG-based MMG could be regenerated in ethanol for reuse without obvious decline of removal efficiency. On the basis of the superior adsorption property of HPG-based MMG, this work offers an effective strategy to prepare advanced adsorbent for dye removal from wastewater.

In spite of recent progress in developing hollow micro/nanostructures, the synthesis of three-dimensional adsorbents with high adsorption efficiency and capability on the basis of these structures still remains a great challenge. Herein, we demonstrate a facile hydrothermal strategy to synthesize uniformly dispersed hollow CuWO4 spheres. The as-prepared CuWO4 spheres with unique mesoporous structure show favorable selective adsorption for cationic dyes and good recyclability. The adsorption capacity of hollow CuWO4 towards methylene blue (MB) reaches 59.82 mg g−1. Furthermore, the hollow CuWO4 spheres present enhanced photoelectrochemical performance under visible light illumination. This strategy of acquiring specifically functionalized materials from smart design and simple chemical process has opened up wide opportunities on the fabrication of alternative absorbents and photoelectrodes based on CuWO4 substrate.

Titanate-based materials are attractive inorganic adsorbents for wastewater treatment. In this study, hierarchical hollow sodium titanate microspheres (HHSTMs) were successfully synthesized via a template-assisted method. Silica microspheres were selected as hard templates, with a uniformly smooth TiO2 shell first grown onto the surface of the SiO2 cores. Then, through an alkaline hydrothermal process, the silica core was removed and the TiO2 shell gradually converted into a sodium titanate shell with a preserved morphology. The as-synthesized HHSTMs are constructed from twined nanobelts, with a high surface area of 308 m2 g−1. A typical organic dye, methylene blue, was employed to investigate the adsorption properties of the HHSTMs. The adsorption process matched well with the Langmuir isothermal model, with the maximum adsorption capacity of methylene blue reaching 443 mg g−1. Moreover, the resulting HHSTMs can be used to selectively capture of methylene blue from a cationic-anionic dye binary system due to their negatively charged surface. All adsorption processes were very fast and could complete in ten minutes.

A variety of quaternary ammonium salts with different carbon chain lengths were used to modify and convert montmorillonite clay to organoclays. The surface modification attributing to the wettability was investigated using various techniques. The zeta-potential values of all clays showed pH dependency. The prepared organoclays were utilized for phenol (protic) and nitrobenzene (aprotic) adsorption in a batch system, with pH and contact time as variables. The optimized removal for phenol and nitrobenzene within 30 min of equilibrium observed at pH 9.0 and 5.0, respectively. Observed equilibrium data followed the Langmuir monolayer adsorption kinetics with two adsorption sites (outer-layer and interlayer) for purified clay, and third additional sites for organoclays. Kinetic studies revealed that the adsorption of phenol was in the order of mono- > tetra- > di- > benzyl-substituted organoclays, which is similar to the hydrophilicity order. However, the exact opposite trend of adsorption was observed for nitrobenzene. From the performed quantitative study, it is inferred that –OH functional phenol and –NO2 functional nitrobenzene have an affinity towards the hydrophilic clay surface and hydrophobic surfaces of quaternary ammonium salts as its first preference, respectively. This study brings promising observations and implications to the vital structural-property relationship for selective adsorption of pollutants from aqueous solutions.

In the present study, capability of nanodiamond (ND) for the adsorption of anionic (methyl orange, MO) and cationic (methylene blue, MB) dyes from aqueous solution was investigated. Employing fourier transform infrared (FTIR) spectroscopy, Boehm titration method and zeta potential, it was found that the simple thermal oxidation of ND at 425 °C, increased the content of carboxylic acid of ND and accordingly the zeta potential of ND decreased considerably. Therefore, a series of oxidized NDs (OND) at various oxidation times and as-received untreated ND (UND) was used as adsorbents of MO and MB. The adsorption experiments exhibited that UND had large adsorption capacity, very fast adsorption kinetics and excellent selectivity for MO over MB. These results suggested that the adsorption tendency of UND toward anionic MO dye followed not only by electrostatic interactions but also via the chemical interaction caused by the strong hydrogen bond between the sulfonate groups of MO and the oxygen containing groups on the surface of UND. In contrast, ONDs exhibited higher adsorption capacity for cationic MB whose tendency toward MB increased by increasing the thermal oxidation time due to the promotion of the negative charge on the surface of OND leading to the higher electrostatic attraction. The adsorption rate of MB on ONDs was also very high. Kinetics data was well fitted with the pseudo- second-order model for most of the adsorbents. The adsorption selectivity analysis revealed that ONDs displayed more adsorption capacity for MB compared with MO which was also attributed to high electrostatic interactions of cationic dye with negative charges of ONDs. Finally, the release behavior of NDs was also demonstrated after soaking in ethanol and acetone.

In this study, POM@UiO-66 nanoparticles were fabricated by encapsulation of POM (K6P2W18O62 polyoxometalate) into mesoporous UiO-66 metal organic framework through a solvothermal method with trichloroacetic acid as a modulator to promote the defects formation of UiO-66. The as-prepared samples were characterized by TEM, SEM, PXRD, TG, XPS, and EDX elemental mapping, and the successful combination of POM and UiO-66 was confirmed. Two cationic dyes, rhodamine B and malachite green, and one anionic dye orange G were employed to investigate the adsorption performance of POM@UiO-66. The adsorption data showed that the removal process of cationic dyes by POM@UiO-66 matched well with the pseudo-second-order model and Langmuir isothermal model. The resulting POM@UiO-66 nanoparticles exhibited high adsorption to cationic dyes but low adsorption to anionic dyes, and the adsorption capacities of rhodamine B, malachite green, and anionic dye orange G were 222.6, 190.6 and 40 mg g−1, respectively. Furthermore, the cationic dyes could be selectively removed from a cationic-anionic dye binary system. These results suggested that the novel polyoxometalate-based UiO-66 material is a promising candidate for the adsorption of cationic dyes from effluent.

Two silver-based coordination polymers, [Ag2(bpy)2(cbda)] (BUC-51) and [Ag3(bpy)3(cpda)]·(NO3)·9H2O (BUC-52), have been successfully prepared by slow evaporation at room temperature. These coordination polymers exhibited good adsorptive performances toward series organic dyes with sulfonic groups, which could be ascribed to the Ag cdots O interaction between the silver(I) atoms in CPs and the oxygen atoms from sulfonic groups attached to organic dyes. Both BUC-51 and BUC-52 favoured slow release of Ag+ ions resulting into outstanding long-term antibacterial abilities toward Gram-negative bacteria, Escherichia coli (E. coli), which was tested by a minimal inhibition concentration (MIC) benchmark and an inhibition zone testing method. Both scanning electron microscope (SEM) and transmission electron microscope (TEM) images demonstrated that these two Ag-based coordination polymers could destroy the bacterial membrane and further cause death. Additionally, the excellent stability in common solvents and good optical stability under UV–visible light facilitated their adsorptive and antibacterial applications.

The polar modified hyper-cross-linked resins were synthesized by the suspension polymerization and Friedel-Crafts alkylation reaction, and the effect of the feeding amount of the monomers (N-vinylimidazole and p-vinylbenzyl chloride) on the porosity and polarity were clarified. As the feeding amount of p-vinylbenzyl chloride decreased from 75% to 50% (w/w), the Brunauer-Emmett-Teller surface area of the resins lowered from 1306 to 436 m2/g, and the pore size distribution showed a large population of pores in micropores stretching to a higher percentage of mesopores. As the feeding amount of N-vinylimidazole increased from 5% to 30% (w/w), the nitrogen content of the resins rose from 0.005% to 3.06% (w/w), and the contact angle decreased from 97±4.2° to 28±2.0°. As a result, the porosity and polarity of the resins could be accurately tuned by adjusting the feeding amount of the monomers, and the different porosity and polarity of these resins endowed them with selective adsorption to benzoic acid and Rhodamine B.

In this work, a novel engineered biochar prepared through modification with chitosan and pyromellitic dianhydride (PMDA) was investigated as an adsorbent for the removal of heavy metal ions from single metal and mixed-metal solutions (Cd, Cu and Pb). Characterization experiments with FTIR and XPS suggested that the novel modified biochar had more surface functional groups compare to the pristine biochar. Adsorption experiments indicated that the initial pH of the solution influenced the ability of biochars to adsorb heavy metals in single- and multi-metal systems. Moreover, the chitosan-PMDA modified biochar had strong selective adsorption of Cu(II). Mechanism studies showed that chemisorption was the major mechanism for heavy metal removal by the chitosan-PMDA modified biochar. Furthermore, the types of effective functional group for these heavy metal removal were different. The NCO group played a dominant role in the process of Pb(II) removal, while several N-containing functional groups and CC groups participated in the adsorption of Cd(II). The novel engineered biochar had selective adsorption capacity for copper due to the N-containing functional groups, meanwhile abundant carbonyl groups also participated in the removal of copper, and may reduce Cu(II) to Cu(I).

UiO-66 was modulated by addition of acetic acid or HCl in the precursor solution. The resulting acetic acid-promoted UiO-66 has more regular octahedral structures and high surface areas of 892–1090 m2/g. Anionic dyes (methyl orange (MO) and Congo red (CR)) and cationic dyes (methylene blue (MB) and rhodamine B (RhB)) were examined for the selective dye adsorption on various UiO-66. The acid-promoted UiO-66 exhibits an excellent selective adsorption to anionic dyes, where the adsorption capacities of MO and MB are 84.8 and 13.2 mg/g, respectively. However, UiO-66 prepared without acid shows similar adsorption to both anionic dye MO (70.4 mg/g) and cationic dye MB (67.5 mg/g). Mixed dyes (MO/MB and MO/RhB) adsorption on acid-promoted UiO-66 further proves the selective adsorption to anionic dyes. The adsorption mechanism was studied by testing the Zeta potential of acid-promoted UiO-66, and more positive Zeta potential (hydrogen ions) of UiO-66 is beneficial to the anionic dye adsorption.

BiFeO3/α-Fe2O3 core/shell composite particles featuring fast removal, selective adsorption, and magnetic recycle capability on anionic methyl orange (MO) dye in water was synthesized by a two-step chemical route. A discontinuous and rough shell consisting of the α-Fe2O3 nanoparticles was deposited on the BiFeO3 core surface preferentially, forming raspberry-like core/shell particle morphology. The core/shell particles demonstrated a pronounced adsorption to the MO molecules when compared with particulate mixtures of the same molar ratio. At an initial MO concentration of 2.5 × 10−5 M, nearly 80% of the dye molecules were captured by the core/shell particles within 5 min at an acidic pH of 5.2. Desorption of the MO dye could be made easily when the solution pH was adjusted to 9.5. This together with a minute adsorption capacity (

With various functionalities in the framework and high thermal stability, metal-organic frameworks (MOFs) have been extensively studied for the applications in adsorption and separation. In last decade, synthesizing new MOFs with desired structures and improved chemical stability to meet these applications has drawn great attention. In this report, by using an organic ligand with azolate moiety, benzo-bis(imidazole) (H2BBI), we synthesized two new 2D layered MOF structures with distinct topologies. Framework 1 {[Zn2Cl2(BBI)(MSM)2]n, MSM=methylsulfonylmethane}, constructed from tetrahedral Zn(II) and BBI, maintains its structure in organic solvents, such as methanol and benzene, and even in water. Meanwhile, framework 2 {[Cd2Cl2(BBI)(DMSO)2]n, DMSO=dimethyl sulfoxide} differs from framework 1, and is assembled from trigonal bipyramidal Cd(II) and square planar BBI. By removing the DMSO molecules coordinated to Cd(II) (25 weight% of the structure), 2 could transform to 3 {[Cd2Cl2(BBI)]n}, which was further characterized by high-resolution powder X-ray diffraction. The solvent-free 3 retains the original connectivity within each layer, and is capable of reversible and selective adsorption of DMSO molecules. The bistable four- and five-coordinated geometry exchange of Cd(II) is the origin of this adsorption with improved selectivity and capacity.