Smart Adsorbents Research Articles

Developments and Applications of Molecularly Imprinted Polymer-Based In-Tube Solid Phase Microextraction Technique for Efficient Sample Preparation.

Despite advancements in the sensitivity and performance of analytical instruments, sample preparation remains a bottleneck in the analytical process. Currently, solid-phase extraction is more widely used than traditional organic solvent extraction due to its ease of use and lower solvent requirements. Moreover, various microextraction techniques such as micro solid-phase extraction, dispersive micro solid-phase extraction, solid-phase microextraction, stir bar sorptive extraction, liquid-phase microextraction, and magnetic bead extraction have been developed to minimize sample size, reduce solvent usage, and enable automation. Among these, in-tube solid-phase microextraction (IT-SPME) using capillaries as extraction devices has gained attention as an advanced "green extraction technique" that combines miniaturization, on-line automation, and reduced solvent consumption. Capillary tubes in IT-SPME are categorized into configurations: inner-wall-coated, particle-packed, fiber-packed, and rod monolith, operating either in a draw/eject system or a flow-through system. Additionally, the developments of novel adsorbents such as monoliths, ionic liquids, restricted-access materials, molecularly imprinted polymers (MIPs), graphene, carbon nanotubes, inorganic nanoparticles, and organometallic frameworks have improved extraction efficiency and selectivity. MIPs, in particular, are stable, custom-made polymers with molecular recognition capabilities formed during synthesis, making them exceptional "smart adsorbents" for selective sample preparation. The MIP fabrication process involves three main stages: pre-arrangement for recognition capability, polymerization, and template removal. After forming the template-monomer complex, polymerization creates a polymer network where the template molecules are anchored, and the final step involves removing the template to produce an MIP with cavities complementary to the template molecules. This review is the first paper to focus on advanced MIP-based IT-SPME, which integrates the selectivity of MIPs into efficient IT-SPME, and summarizes its recent developments and applications.

Hydrogen bonds-based flexible regulation of acetaminophen adsorption/desorption behavior in aqueous system: Role of the smart thermoresponsive graphene oxide

Adsorption and regeneration techniques are crucial for the treatment of pharmaceuticals in drinking water. However, adsorbents with strong adsorption binding force and simple regeneration have been a challenging issue in the adsorption area that has not been successfully resolved. In this study, a thermos-responsive smart adsorbent, poly (N-isopropylacrylamide) modified graphene oxide (GO-g-PNIPAM) was successfully synthesized using a “graft from” surface-initiated atom-transfer radical polymerization (Si-ATRP) technology. Acetaminophen (Acet) has an excellent efficient adsorption/desorption behavior (107.40/83.9 mg/g) that is potentially flexible controlled by the modified adsorbent only by adjusting the temperature. This exceptional property is primarily caused by the phenomenon that PNIPAM cooperated with GO to undergo hydrophilic transformation in response to temperature changes, allowing for the free construction and deconstruction of hydrogen bonds between PNIPAM and contaminants. More importantly, as external factors (NaCl and urea) are mediated, the development of hydrogen bonds would be further encouraged to further stabilized the efficiency, and the desorption temperature would continue decrease by 2 and 6 °C, respectively, to promote the regeneration process. This outstanding work provides novel perspectives for subsequent smart sensitive materials to flexibly regulate the treatment efficiency of pollutants.

Innovative Solid-Phase Extraction Strategies for Improving the Advanced Chromatographic Determination of Drugs in Challenging Biological Samples.

In the past few decades, considerable scientific strides have been made in the subject of drug analysis in human biological samples. However, the risk caused by incorrect drug plasma levels in patients still remains an important concern. This review paper attempts to investigate the advances made over the last ten years in common sample preparation techniques (SPT) for biological samples based on solid sorbents, including solid-phase extraction (SPE) and solid-phase micro-extraction (SPME), and in particular in the field of molecularly imprinted polymers (MIPs), including non-stimuli-responsive and stimuli-responsive adsorbents. This class of materials is known as 'smart adsorbents', exhibiting tailored responses to various stimuli such as magnetic fields, pH, temperature, and light. Details are provided on how these advanced SPT are changing the landscape of modern drug analysis in their coupling with liquid chromatography-mass spectrometry (LC-MS) analytical techniques, a general term that includes high-performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography (UHPLC), as well as any variation of MS, such as tandem (MS/MS), multiple-stage (MSn), and high-resolution (HRMS) mass spectrometry. Some notes are also provided on coupling with less-performing techniques, such as high-performance liquid chromatography with ultraviolet (HPLC-UV) and diode array detection (HPLC-DAD) detection. Finally, we provide a general review of the difficulties and benefits of the proposed approaches and the future prospects of this research area.

Multifunctional 2D hemin-bridged MOF for the efficient removal and dual-mode detection of organophosphorus pesticides.

The high-residual and bioaccumulation property of organophosphorus pesticides (OPs) creates enormous risks towards the ecological environment and human health, promoting the research for smart adsorbents and detection methods. Herein, 2D hemin-bridged MOF nanozyme (2D-ZHM) was fabricated and applied tothe efficient removal and ultrasensitive dual-mode aptasensing of OPs. On the one hand, the prepared 2D-ZHM contained Zr-OH groups with high affinity for phosphate groups, endowing it with selective recognition and high adsorption capacity for OPs (285.7mgg-1 for glyphosate). On the other hand, the enhanced peroxidase-mimicking biocatalytic property of 2D-ZHM allowed rapid H2O2-directed transformation of 3,3',5,5'-tetramethylbenzidine to oxidic product, producing detectable colorimetric or photothermal signals. Using aptamers of specific recognition capacity, the rapid quantification of two typical OPs, glyphosate and omethoate, was realized with remarkable sensitivity and selectivity. The limit of detections (LODs) of glyphosate were 0.004nM and 0.02nM for colorimetric and photothermal methods, respectively, and the LODs of omethoate were 0.005nM and 0.04nM for colorimetric and photothermal methods, respectively. Theconstructed dual-mode aptasensing platform exhibited outstanding performance for monitoring OPs in water and fruit samples. This work provides a novel pathway to develop MOF-based artificial peroxidase and integrated platform for pollutant removal and multi-mode aptasensing.

Imidazolium-Functionalized Conjugated Polymer for On-Site Visual and Ultrasensitive Detection of Toxic Hexavalent Chromium.

Hexavalent chromium [Cr(VI)] is considered a serious environmental pollutant that possesses a hazardous effect on humans even at low concentrations. Thus, the development of a bifunctional material for ultratrace-selective detection and effective elimination of Cr(VI) from the environment remains highly desirable and scarcely reported. In this work, we explore an imidazolium-appended polyfluorene derivative PF-DBT-Im as a highly sensitive/selective optical probe and a smart adsorbent for Cr(VI) ions with an ultralow detection limit of 1.77 nM and removal efficiency up to 93.7%. In an aqueous medium, PF-DBT-Im displays obvious transformation in its emission color from blue to magenta on exclusively introducing Cr(VI), facilitating naked-eye colorimetric detection. Consequently, a portable sensory device integrated with a smartphone is fabricated for realizing real-time and on-site visual detection of Cr(VI). Besides, the imidazolium groups attached onto side chains of PF-DBT-Im are found to be highly beneficial for achieving selective and efficient elimination of Cr(VI) with capacity as high as 128.71 mg g-1. More interestingly, PF-DBT-Im could be easily regenerated following treatment with KBr and can be recycled at least five times in a row. The main factor behind ultrasensitive response and excellent removal efficiency is found to be anion-exchange-induced formation of a unique ground-state complex between PF-DBT-Im and Cr(VI), as evident by FT-IR, XPS, and simulation studies. Thus, taking advantage of the excellent signal amplification property and rich ion-exchange sites, a dual-functional-conjugated polymer PF-DBT-Im is presented for the concurrent recognition and elimination of Cr(VI) ions proficiently and promptly with great prospects in environmental monitoring and water decontamination.

Profile of the Adsorption Ability of Sulfonate-Modified Lignocellulose Based on Bagasse Waste to Some Batik Textile Dyes

The presence of synthetic dye contamination produced from the batik industry encourages research to overcome it through the adsorption method using a smart adsorbent, in this case an adsorbent that has several active groups. This study aims to examine the adsorbent of lignocellulose sulfonate based on bagasse waste for some textile dyes used in the batik industry. The synthesis of lignocellulose sulfonate was carried out through several steps such as extraction and activation using Na2SO3 and NaHCO3. The resulting products were then characterized using FTIR and SEM apparatures and applied them as an adsorbent for Remazol Red RB and Indanthrene Blue RS dyes. The adsorption test was carried out using bagasse, lignocellulose, and lignocellulose sulfonate adsorbents at a solution concentration of 50 ppm with variations in contact time of 5, 10, 20, 40, 80, and 160 minutes. The remaining dye content in the solution was then tested using a UV-Vis Spectrophotometer. From the experimental results, it is known that lignocellulose sulfonate, lignocellulose, and bagasse are able to absorb Remazol Red RB dye, respectively, by 84.41%, 63.87% and 61.52%. While for Indanthrene Blue RS dye, the largest absorption was found in lignocellulose sulfonate adsorbents of 56.35%, lignocellulose 50.72%, and baggase 45.93%. The highest adsorption capacity was found in the lignocellulosic sulfonate adsorbent, namely 42.2081 ppm for Remazol Red RB adsorption and 28.1771 ppm for Indanthrene Blue RS dye.

Aptamer-thrombin loaded magnetic microspheres for bio-specific extraction and precise detection of hirudin

Hirudin, that is naturally occurring in leeches (Hirudo medicinalis) and known as the most potent natural inhibitor of thrombin, exerts double-edged effects in clinic application. It can be used as a therapeutic ingredient for cardiovascular disease, while it can be regarded as a toxic polypeptide with bleeding risk. Effective detection of hirudin in biological samples contributes greatly to reasonable therapy. In this study, we proposed a smart adsorbent based on affinity magnetic microspheres, where thrombin was immobilized for capturing hirudin in the animal serum. Aptamer was introduced as a ligand for linking the magnetic agarose microspheres and thrombin, thereby avoiding loss of biological activity of the enzyme to hirudin. Taken recombinant hirudin variant 2-Lys47 (rHV2) as a model, we established a rapid and bio-specific extraction method coupled with liquid chromatography and quadrupole-time-of-flight mass spectrometry (LC-QTOF/MS) for determination of hirudin in the serum. Owing to this strategy, a low limit of detection (LOD) of rHV2 (0.5 nM), a good linearity with correlation coefficient of 0.9975, an acceptable precision with relative standard deviation (RSD) below 3.6% (n = 6) and acceptable recoveries ranging from 85.7% to 90.2% were achieved. Moreover, the functionalized magnetic composite could be reused for at least nine cycles. Our work combined the merits of affinity separation and advanced instrument analysis for hirudin, providing a new vision to precise determination of hirudin in medical and pharmaceutical fields.

A crescent-shaped imprinted microgel adsorbent with near-infrared light-responsive performance for selective adsorption of Lead(II)

Smart hydrogel adsorbent with high selectivity and“on–off”switching ability is vital for the effective elimination of heavy metal pollution, but its simple fabrication remains a serious task. To address this, a facile strategy via an oil-in-water-in-oil (O1/W/O2) droplet microreactor was proposed to prepare polydopamine-coated imprinted microgel adsorbents (DMHIIPs) with crescent shape, and then as-prepared smart adsorbent with near-infrared (NIR) light-responsive performance was used to selectively remove lead ions (Pb(II)) from aqueous solution. The critical solution temperature (LCST) of DMHIIPs is 44.2 °C, resulting from the increase of thermal change and decrease of entropy change during swelling. DMHIIPs have high photothermal conversion efficiency and stability, and the temperature of DMHIIPs dispersion (0.5 mg/L) can be rapidly heated to above 50 °C under NIR (808 nm, 1.0 W cm−2) irradiation for 10 min. The adsorption capacity of Pb(II) on DMHIIPs elevates from 128.0 mg g−1 to 135.2 mg g−1, when the solution temperature increases from 20 °C to 40 °C, but this value significantly reduces to 59.2 mg g−1 at 60 °C. Pseudo-second-order can be well described the kinetic results of DMHIIPs, confirming chemisorption is the rate-limiting step. Desorption ratio of DMHIIPs is 36.5% in 30 min under NIR irradiation, and it can be increased to 63.2% When combining NIR irradiation with the using of elution agent. In addition, the obtained DMHIIPs has excellent selectivity coefficient (k) for competitive Cu(II) (7.20), Cd(II) (23.31), and Ni(II) (39.33), respectively. This work demonstrates a new strategy to NIR-responsive imprinted microgel adsorbent provides a new perspective for controlling the adsorption process of heavy metal pollution.

Adsorption of Phenol from Both Acidic and Basic Industrial Waste via Newly Synthesized Metal Organic Framework Hybrid Smart Adsorbents

Newly prepared pH-responsive metal organic frameworks (MOFs) having a specific surface area of 1400 m2/g could be exploited in the total removal of pollutants from wastewaters in this work. Smart core–shell structures of COP-150@ZIF-8 and NPC@ZIF-8 were successfully synthesized in large scales through internal extended growth under polyvinylpyrrolidone (PVP) regulation and used in phenol removal from aqueous media. The essential factors on the removal, namely pH, initial concentration of phenol, contact time, adsorbent dosage, and temperature, were studied and optimized. The experimental data were investigated by different kinetic and isotherm models, in which the removal of phenol by these smart sorbents is correlated with the Freundlich isotherm model and was found to follow the pseudo-second-order kinetic model. Excellent adsorption capacity of 1670 mg·g–1 and high efficiency were achieved in phenol removal (mixing time of only 20 min) that suggest the application of smart NPC@ZIF-8 core–shell in water filtration. Also, the optimal concentration of smart NPC@ZIF-8 and smart COP@ZIF-8 core–shell adsorbents was obtained as 300 and 250 mg·L–1, respectively. On the other hand, more than 94% removal of phenol was observed at pH = 3 for both smart nanosorbents (mere use of 0.1 g adsorbent). The results of thermodynamics confirm that the process of adsorption is exothermic and spontaneous. Moreover, having simulated the atomistic investigation of phenol removal via molecular dynamics, it was concluded that the different designed adsorbents in this work have a high capacity to remove phenol, specifically NPC@ZIF-8.

Development of poly(vinyl alcohol)/β-cyclodextrin/P(MVE-MA) composite nanofibers as effective and selective adsorbent and filtration material for the removal and separation of cationic dyes from water

The preparation of new smart adsorbent and filtration materials has a great importance for the adsorption and filtration studies. In this study, for the effective adsorption of cationic Basic Yellow 2 (BY2) dye from water and for the selective separation of anionic dye from the anionic and cationic dye mixture solution, a new water-insoluble negatively charged poly(vinyl alcohol) (PVA)/β-cyclodextrin/poly(methyl vinyl ether-alt-maleic anhydride) (P(MVE-MA)) nanofiber membrane was fabricated by using simple electrospinning technique and thermal cross-linking process. The obtained nanofiber composite membrane material was characterized by FTIR, water solubility, mechanical property, SEM, BET specific surface area and pore size distribution measurements. After cross-linking process, maximum tensile stress and Young's modulus of membrane material showed an enhancement from 1.59 MPa to 2.58 MPa and from 66.67 MPa to 146.75 MPa, respectively. For cationic BY2 dye, membrane material exhibited an excellent adsorption capacity value of 2.554 × 10−3 mol g−1 or 775.98 mg g−1. In addition, it did not adsorb anionic Acid Blue 74 (AB74) dye. Kinetic and isotherm data of BY2 followed the pseudo second order and Langmuir models, respectively. For BY2 dye, membrane material displayed a good regeneration performance during the five adsorption/desorption cycles. In the filtration of anionic and cationic dye mixture, PVA/β-cyclodextrin/P(MVE-MA) nanofiber membrane material exhibited a remarkable separation efficiency (99.33%) and showed selective adsorption ability toward cationic BY2 dye. In brief, the fabricated membrane material is of a promising application in the water treatments and separation studies.

Thermoresponsive MXene composite system with high adsorption capacity for quick and simple removal of toxic metal ions from aqueous environment

High-performance adsorption and easy-to-recycle property of adsorbents are desirable in wastewater treatment, and a suitably smart adsorbent with responsive phase separation capacity is promising in this regard. Herein, a thermoresponsive composite system is designed through the combination of transition metal carbides (MXene) and poly(N-isopropylacrylamide) (PNIPAM) for removal of toxic metal ions from water. As a thermoresponsive switch, the PNIPAM endows such composite system with superior thermoresponsiveness (i.e., gel-water phase separation) in water, which facilitates to the control of adsorption. The gel phase triggered by an elevated temperature (e.g., 40 °C) quickly adsorbs toxic metal ions, and then a solid-liquid extraction way is used to conveniently separated the gel phase from water phase for simple removal of toxic metal ions. A very high adsorption capacity (e.g., ~224 mg·g−1 for Cu2+) can be achieved due to the synergistic effects of the composite system. Moreover, the separated gel can be back to a redispersed state at low temperature (e.g., 20 °C), enabling its effective regeneration and recovery. Notably, the PNIPAM as a protective agent prevents the oxidation of MXene so as to retain good stability during the multiple adsorption/desorption cycles. This simple and smart adsorption strategy is great promising for water purification application.

Superhydrophobic starch-based cryogels modified with silylated magnetic nanoparticles for oil spill cleanup

Superhydrophobic smart adsorbents have attracted wide attention for the cleanup of oil spill that endangers the aquatic ecosystem. Herein, a super-water-repellent coating (HOS/Fe3O4) was achieved through hydrolytic condensation of hexadecyltrimethoxysilane and tetraethyl orthosilicate in the presence of Fe3O4 nanoparticles. The coating was then introduced onto the surface of starch cryogel (SC) by spray-coating technique to fabricate the superhydrophobic and magnetic starch-based adsorbent (HOS/Fe3O4@SC). The surface chemical composition and hierarchical micro/nanostructures that contribute to the high water contact angle (>151°) and low sliding angle (<5°) of the as-obtained material were characterized in detail. The HOS/Fe3O4@SC exhibited excellent water repellent, self-cleaning, and anti-fouling properties. The structural support and stable chemical bonding endow the material with good mechanical and chemical durability. The HOS/Fe3O4@SC also possessed reasonable adsorption capacities to various organic solvents, and its oil absorption kinetics was also comprehensively studied. The HOS/Fe3O4@SC can be applied for heavy oil absorption underwater and magnetically guided oil slick cleaning. This novel starch-based absorbent exhibits promising application in tackling oil contamination in complex environments.

Fast-thermoresponsive carboxylated carbon nanotube/chitosan aerogels with switchable wettability for oil/water separation

The use of aerogels to selectively recover oil from oily wastewater is effective but challenging. In this study, a new carboxylated carbon nanotube/chitosan aerogel (CCNT/CA) with switchable wettability was developed as a smart adsorbent for fast oil absorption and oil recovery. Vinyltrimethoxysilane and thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted onto the surface of the CCNT/CA skeleton, and the resulting smart aerogel (PNI-Si@CCNT/CA) exhibited temperature responsiveness. PNI-Si@CCNT/CA exhibited an excellent reversible conversion between hydrophilicity and hydrophobicity when the temperature was changed to below or above the lower critical solution temperature (LCST) of PNIPAAm (~32 °C). Most importantly, CCNT significantly increased the oil absorption capacity, improved the mechanical properties, accelerated phonon conduction, enhanced thermal conductivity (80.57 mW m−1 K−1), improved the temperature response rate, shortened the oil desorption time (15 min), and improved the oil/water separation efficiency of PNI-Si@CCNT/CA because a strong interface interaction occurred between CCNT and chitosan. Moreover, PNI-Si@CCNT/CA absorbed oil at 45 °C and released the absorbed oil at 25 °C. It maintained its good adsorption performance after 15 cycles, and this was ascribed to its excellent mechanical properties and stable structure.

Process-Oriented Smart Adsorbents: Tailoring the Properties Dynamically as Demanded by Adsorption/Desorption.

Adsorptive separation plays a critical role in chemical, food, pharmaceutical, and environmental industries, as well as in many other industrial areas. Adsorbents are most important for adsorptive separation and undergo adsorption and desorption processes to accomplish the specific tasks of separation. In the process of adsorption, adsorbates diffuse into the pore spaces of adsorbents through pore openings, adsorb on active sites via physical or chemical interactions, and subsequently are regenerated by temperature or pressure swings during desorption. In the process of adsorption and desorption, however, the requirements for pore structures and surface properties of adsorbents are different. In general, adsorbents with small pore openings can realize selective adsorption and do not favor desorption; on the other hand, adsorbents with large pore openings are efficient in desorption but at the expense of adsorption selectivity. Remarkably, active sites possessing strong interactions with adsorbates contribute to high selectivity for adsorption, while desorption becomes difficult. The trade-off between adsorption and desorption presents an enormous challenge to develop high-efficiency adsorbents. Restricted by their fixed structures and surface properties, conventional adsorbents are unable to meet the demands of adsorption and desorption processes simultaneously.To confront the obstacles, the development of advanced adsorbents to meet the demand of adsorptive separation are urgent. A key strategy to address such issues lies in dynamically adjusting the pore structures or the surface properties of adsorbents with controllability according to the demands of adsorption/desorption. For instance, pursuant to the requirements of varying pore structures during adsorption/desorption, the pore openings of adsorbents can be customized through dynamic structural change of the decorated stimuli-sensitive motifs by suitable external intervention. In addition, the active sites within the adsorbents can be exposed to enhance the adsorption selectivity or sheltered to accelerate the desorption through stimuli-triggered adsorbent-adsorbate interactions. Hence, we proposed a concept of process-oriented smart adsorbents (POSAs) on the basis of the requirements of the adsorption/desorption processes. The design and development of such POSAs are based on three aspects, namely, pore openings, pore spaces, and adsorption sites of adsorbents.In this Account, we present the progress in the development of POSAs according to the demands of adsorption/desorption processes. A series of POSAs with incorporated stimuli-sensitive motifs were successfully achieved. The versatility of incorporated motifs allows them to tune the pore structures and surface properties of adsorbents dynamically and further to enhance the adsorption and desorption efficiency simultaneously. Based on the concept of POSAs, we hope that this Account could contribute to the development of high-efficiency adsorbents and ultimately promote their applications in practical industrial separation. Moreover, we present an outlook on future trends and challenges on the road toward the development and applications of POSAs.

Design of a Spiropyran-Based Smart Adsorbent with Dual Response: Focusing on Highly Efficient Enrichment of Phosphopeptides.

Smart responsive materials have attractive application prospects due to their tunable behaviors. In this work, we design novel spiropyran (SP)-based magnetic nanoparticles (MNP-SP) with dual response to ultraviolet light and pH and apply them to the enrichment of phosphopeptides. SP is modified on the surface of magnetic nanoparticles through a simple esterification reaction, based on which an MNP-SP-MS phosphopeptide identification platform is established. The capture and release of phosphopeptides are facilely adjusted by changing external light and the pH of the solution. The smart responsive MNP-SP has fast magnetic response performance, high sensitivity (detection limit of 0.4 fmol), and good reusability (6 cycles). In addition, MNP-SP is used for the enrichment of phosphopeptides in skimmed milk, human saliva, and human serum samples, indicating that it is an ideal adsorbent for enriching low-abundance phosphopeptides in complex biological environments.

Copper upcycling by hierarchical porous silica spheres functionalized with branched polyethylenimine: Antimicrobial and catalytic applications

The increment of environmental pollution from heavy metals released by industrial or urban sources drives the development of new smart adsorbents. In particular, copper pollution is a rising concern due to its presence in industrial streams and electronic wastes. Mesoporous silica is a useful adsorbent for copper uptake but it requires the incorporation of specific functionalities to enhance the uptake and selectivity. Branched polyethylenimine (PEI) is a specific copper chelate agent but its bulky structure hinders the loading on mesoporous supports. In this work, the incorporation of PEI on a hierarchical porous silica with wrinkled meso/macroporosity (w-SiO2) resulted in a smart adsorbent with higher copper adsorption capacity. After the uptake, the annealing of the adsorbed PEI-copper complex leads to a w-SiO2/CuO nanocomposite with outstanding antimicrobial properties and catalytic activity due to the enhanced copper bioavailability. The minimum inhibitory concentration of supported copper oxide on silica for E. coli in LB broth medium was 825.5 μg Cu/ml. Oxidation of the electron donor molecule ABTS in the presence of this nanocomposite and H2O2 is a first demonstrator of the potential application as a peroxidase-like nanozyme. The use of adsorbents with hierarchical porosity to support bulky functionalities with high selectivity is a novel strategy for heavy metals upcycling.

Greener approach for fabrication of antibacterial graphene-polypyrrole nanoparticle adsorbent for removal of Mn2+ from aqueous solution

Herein, novel, efficient and multifunctional heavy metals adsorbent is developed. Graphene sheets are facilely prepared using ultrasonication process with the aid of polyethyleneglycol. Then, spherical polypyrrole nanoparticles of an average size of 150 nm are polymerized on the surface of prepared graphene sheets using green method yielding nanocomposite. The developed graphene-polypyrrole nanocomposite is exploited for removal and recovery of Mn2+ from aqueous solution. The developed graphene-based nanocomposite achieved superior adsorption efficiency for removal of Mn2+ ions than polypyrrole nanoparticles of similar particle size. The new adsorbent achieved excellent removal efficiency of Mn2+ ions recording 89%. Additionally, the smart adsorbent shows antibacterial properties toward Staphylococcus aureus bacteria providing a clear bacterial inhibition zone of 10 mm. The influence of various adsorption parameters of adsorbent dose, contact time and initial metal ions concentrations on the adsorption Mn2+ are studied and optimized. The adsorption of Mn2+ ions on the nanocomposite is also evaluated using Langmuir and Freundlich models and the adsorption isotherms of Mn2+ are suitable and described well with the Langmuir model. Therefore, this study presents a new approach for the design and engineering of safe handling and processing of antibacterial adsorbent for efficient removal and recovery of heavy metal ions from wastewater.

Smart Adsorbents for Aquatic Environmental Remediation.

A noticeable interest and steady rise in research studies reporting the design and assessment of smart adsorbents for sequestering aqueous metal ions and xenobiotics has occurred in the last decade. This motivates compiling and reviewing the characteristics, potentials, and performances of this new adsorbent generation's metal ion and xenobiotics sequestration. Herein, stimuli-responsive adsorbents that respond to its media (as internal triggers; e.g., pH and temperature) or external triggers (e.g., magnetic field and light) are highlighted. Readers are then introduced to selective adsorbents that selectively capture materials of interest. This is followed by a discussion of self-healing and self-cleaning adsorbents. Finally, the review ends with research gaps in material designs.

Recent developments of pesticide adsorbents based on cyclodextrins

农药的研发与使用极大地提高了农作物的产量,为解决人类温饱、改善人类生活品质做出了贡献。但是,农药广泛残留于农副产品以及土壤和水体中,造成的污染日趋严重。残留的农药通常具有微量致毒、难生物降解、生物累积等特性,对生物健康与生态系统造成了巨大威胁。高效检测微量农药、减小污染危害是亟待解决的问题。吸附法具有成本低、操作简单、稳定性强、可重复性强的特点,在农药分离预富集领域得到了广泛关注。作为一种常用的农药吸附剂材料,环糊精是一类具有空腔的超分子化合物,能够作为主体通过主客体作用形成包合物;另外,可以通过醚化、酯化、氧化等化学反应对环糊精进行后修饰以提高其吸附性能。疏水作用、静电作用、范德华力、氢键作用、立体效应协同促进对农药的吸附。环糊精在农药吸附领域已经取得了一定进展,但是目前还没有基于环糊精的农药吸附剂的综述。该文针对杀菌剂、杀虫剂、除草剂、植物生长调节剂这4类农药,系统性地评述了基于环糊精的农药吸附剂的制备、吸附机理及应用,目前存在个别吸附剂吸附容量不高、降解机理不明确、降解产物对环境不友好、容易造成二次污染的问题,研发高吸附容量、易回收、易分离、易再生的基于环糊精的农药吸附剂是未来的主要研究方向。

Thermoresponsive PNIPAM-b-PAA block copolymers as “smart” adsorbents of Cu(II) for water restore treatments

Copper(II) as a heavy metal ion is posing risk to aquatic ecosystems including algae, fish, mollusks, and bacteria, negatively affecting human life because of bioaccumulation and non-biodegradability. In this study, two thermoresponsive PNIPAM-b-PAA block copolymers with different characteristics in terms of molecular weight and PAA composition were investigated to remove copper ions from simulated water. We chose to utilize those block copolymers in CuSO4 adsorption experiments in order to comprehend how the combination of the thermoresponsive PNIPAM block and the binding ability that PAA block offers, affects the adsorption of Cu2+ and SO42− and provides eventually their removal from aqueous solutions. The adsorption protocol includes simple mixing of the copolymer and CuSO4 aqueous solutions under stirring. Dynamic and electrophoretic light scattering, pH, UV–vis, turbidity and ICP-OES measurements were conducted to verify the PNIPAM-b-PAA ability as smart adsorbents. The results showed that the PNIPAM-b-PAA_50−50 sample offers the possibility of Cu2+ and SO42- adsorption of greater percentage especially when temperature increases to 60 °C. Therefore, PNIPAM-b-PAA block copolymers comprise efficient and smart Cu2+ and SO42- adsorbents.