Capacity For Metal Ions Research Articles

Adsorption characteristics and mechanisms of individual and a quinary mixture of heavy metal ions on novel CoFe2O4-BiFeO3 nanosorbents in water

Application of CoFe2O4-BiFeO3 nanocomposites (CFO-BFO NCs) in highly adsorptive removal of heavy metal ions (Pb(II), Co(II), Cu(II), Cd(II) and Zn(II)) by individual and simultanoeous adsorption were investigated for the first time in the present study. The characterization of CFO-BFO NCs were analyzed by using XRD, VSM, SEM, TEM and BET techniques. The CFO-BFO NCs powder consists of characteristic peaks of BFO and CFO without any trace of other crystalline phases; they were uniformly dispersed with a size of about 3–5 nm, much smaller than single – phase CFO (10–25 nm) and BFO (5–10 µm) with the surface area of 84.93 m2/g; remanence and coercivity were 14.33 emu/g, 1.99 emu/g and 195 Oe, respectively, significantly decreased compared to CFO but significantly increased compared to BFO. The single or simultaneous adsorption of a quinary mixture of Pb(II), Co(II), Cu(II), Cd(II) and Zn(II) on CFO-BFO NCs followed the Freundlich isotherm model and the pseudo-second-order kinetic model. Adsorption capacity of single heavy metal ions were in the order Pb(II) > Co(II) > Cu(II) > Cd(II) > Zn(II) while the simultaneous adsorption was in the order Pb(II) > Cu(II) > Co(II) > Zn(II) > Cd(II). The maximum adsorption capacities (qmax) of each ion in the case of simultaneous adsorption were smaller than that for cases of the single adsorption but the total qmax of ions mixture was much higher than the highest qmax of single adsorption. The simultaneous adsorption of heavy metal ions is the competition, the best selectivity is Pb(II) and the strongest competition is Cd(II), the adsorption ability reduces as the charge and radius of interfering cation increase and the ionic strength increases. The regeneration and reuse ability were good, while the adsorption efficiency slightly decreased over three recycles. The adsorption increased slightly as temperature increased. The adsorption process was spontaneous and endothermic. Adsorption of heavy metal ions on CFO-BFO NCs consists of both electrostatic and chemisorption. The applicability for real sample is good. Our results demonstrate that the CFO-BFO NCs is a prospective adsorbent to remove Pb(II), Co(II), Cu(II), Cd(II) and Zn(II) from aqueous environment.

Enhanced peroxidase-like activity based on electron transfer between platinum nanoparticles and Ti3C2TX MXene nanoribbons coupled smartphone-assisted hydrogel platform for detecting mercury ions

BackgroundHeavy metal pollution poses a serious threat to the ecological environment. Mercury ion (Hg2+) is a class of highly toxic heavy metal ions, which is bioaccumulative, difficult to breakdown, and has a significant affinity with sulfur and thiol-containing proteins, which seriously affects environmental safety and human health. Nanozyme-based sensing methods are expected to be used to detect toxic heavy metal ions. However, the application of precious metal nanozymes to develop portable sensors with simplicity, high stability, and high sensitivity has not been explored to a large extent. ResultsIn this paper, based on MXene's unique adsorption capacity for certain precious metal ions, PtNPs/Ti3C2TXNR composites were successfully prepared by in-situ growth of Pt nanoparticles (PtNPs) on the surface of Ti3C2TX MXene nanoribbons (Ti3C2TXNR) using the hydrothermal technique. Experimental data revealed PtNPs/Ti3C2TXNR exhibited superior peroxidase-like activity, attributed to the synergistic effect of well-dispersed ultrasmall PtNPs and electron transfer effect. Hg2+ can significantly inhibit enzyme-like activity of PtNPs/Ti3C2TXNR due to specific capture and partial in-situ reduction of PtNPs, so a colorimetric sensor was constructed for ultra-trace detection of Hg2+ with a linear range of 0.2 nM and 400 nM. Furthermore, using the portable detecting capabilities of smartphones and hydrogel, a smartphone-assisted hydrogel sensing platform of Hg2+ was constructed. Notably, the two-mode sensing platforms exhibited outstanding detection performance with LOD values as low as 15 pM (colorimetric) and 26 pM (hydrogel), respectively, superior to recently reported nanozyme-based Hg2+ sensors. SignificanceCompared with other methods, the PtNPs/Ti3C2TXNR-based dual-mode sensor designed in this paper has superior sensitivity, high selectivity, simple operation and portability. In particular, the dual-output sensing strategy enables self-confirmation of detection results, greatly improving the reliability of the sensor, and is expected to be used for the on-site determination of trace mercury ions.

A facile fabricated electrochemical sensor based on dual-shell Sn4CoO9.3 microspheres for simultaneous detection of Pb2+ and Hg2+

The presence of heavy metal ions poses significant health hazards to humans, necessitating an urgent demand for a rapid and efficient detection method. Electrochemical sensing offers a promising approach that enables high sensitivity and selectivity in detecting heavy metal ions. In this study, a novel bimetallic oxide, Sn4CoO9.3, with dual shells and multiple pores was developed by a simple template-free method. The unique dual-shell structure and multiple pores greatly enhance its adsorption capacity for heavy metal ions, while the mesoporous pores facilitate electrolyte and ion diffusion. A sensor based on Sn4CoO9.3/CS-ERGO with the excellent electroactive properties and outstanding absorption capacity was fabricated for the simultaneous detection of different heavy metal ions (Pb2+ and Hg2+). By harnessing the benefits of Sn4CoO9.3 and graphene sheets, the sensors that were created exhibited exceptional sensitivity, stability, and minimal interference when detecting Pb2+ and Hg2+ in real samples. These results suggest promising prospects for utilizing the sensor in environmental water quality monitoring applications.

A novel COP adsorbent built up by thiophene group: Rapid and selective adsorption toward trace hazardous Hg(II)

Mercury is one of the most toxic heavy metals to humans. Developing highly efficient adsorbent for removing mercury is of great significance. Herein, two thiophene-based COPs were synthesized through Schiff base reaction by rationally selecting thiophene group as COP building block and functional component simultaneously, avoiding the drawbacks of functionalization strategy such as sacrificing the porous structure and blocking the active sites. The high S/N content in the COPs structure enables robust adsorption towards Hg(II), with maximum adsorption capacity up to 468.8 mg g−1. Notably, even in the presence of 12 interfering ions, the resulting COP-BTTS effectively reduced trace Hg(II) at 1000 μg L−1 to 33 μg L−1 within 30 s, achieving a removal rate up to 97 %, and below the regulatory discharge limit of 10 μg L−1 for wastewater in 15 min. Moreover, the temperature of COP-BTTS can rise to 140 °C-150 °C under xenon light due to its exceptional photothermal property, which can facilitate the efficient desorption of Hg2+. And the COP-BTTS maintains its exceptional recoverability after the successive repeated 5 cycles. This work sheds light on the feasible strategy for designing and synthesizing COP adsorbent with high adsorption capacity, selectivity, and irradiation-assisted desorption of metal ions.

A comparative study of calcium oxide nanoparticle and its ferrite (CaO/Fe2O3) nanocomposite for removal of zinc and nickel from electroplating effluent

Electroplating effluent contains many heavy metals including Zinc (Zn) and Nickel (Ni) are some of the crucial metals which exist in high concentrations. Calcium Oxide nanoparticles (CaONPs) and CaO/Fe2O3 nanocomposite (CaO/Fe2O3NC) were synthesized to evaluate the feasibility of Zn (II) and Ni (II) removal from wastewater. CaO NPs were successfully synthesized from waste eggshells by the sol–gel process while the chemical precipitation method was used for the synthesis of CaO NC. The morphology of the prepared material was characterized by X-ray diffraction (XRD), DLS, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analysis. Batch studies were performed to assess the effect of pH, time, and adsorbent dose on the adsorption efficiency of the nanoparticle and nanocomposite for Zn (II) and Ni (II) removal. Inductively coupled plasma mass spectroscopy (ICP-MS) was used to monitor the amount of Zn (II) and Ni (II) ions in the aqueous solutions. The adsorption capacity of both metal ions increases with an increase in pH, with maximum adsorption occurring at pH 8. An optimum dose of 75 mg/L was observed with both CaO nanoparticle and CaO/Fe2O3 nanocomposite to remove Zn (II) and Ni (II) while equilibrium was achieved after 1 h. The high adsorption capacity makes these adsorbents a promising candidate for removal of metal ions from electroplating effluent.

Antibacterial, antioxidant, Cr(VI) adsorption and dye adsorption effects of biochar-based silver nanoparticles‑sodium alginate-tannic acid composite gel beads

Ultrasonic extraction of Osmanthus fragrans was used for reducing Ag+ to prepare AgNPs, which were further loaded on barley distiller's grains shell biochar. By supplementary of sodium alginate and tannic acid, composite gel beads were prepared. The physical properties of biochar-based AgNPs‑sodium alginate-tannic acid composite gel beads (C-Ag/SA/TA) were characterized. SEM, FTIR, and XRD showed that biochar-based AgNPs were compatible with sodium alginate-tannic acid. CAg greatly improved the dissolution, swelling, and expansion of gel beads. Through the analysis by the agar diffusion method, C-Ag/SA/TA gel beads had high antibacterial activity (inhibition zone: 22 mm against Escherichia coli and 20 mm against Staphylococcus aureus). It was observed that C-Ag/SA/TA composite gel beads had high antioxidant capacity and the free radical scavenging rate reached 89.0 %. The dye adsorption performance of gel beads was studied by establishing a kinetic model. The maximum adsorption capacities of C-Ag/SA/TA gel beads for methylene blue and Congo red were 166.57 and 318.06 mg/g, respectively. The removal rate of Cr(VI) reached 96.4 %. These results indicated that the prepared composite gel beads had a high adsorption capacity for dyes and metal ions. Overall, C-Ag/SA/TA composite gel beads were biocompatible and had potential applications in environmental pollution treatment.

Cellulose-Based Hydrogels for Wastewater Treatment: A Focus on Metal Ions Removal.

The rapid worldwide industrial growth in recent years has made water contamination by heavy metals a problem that requires an immediate solution. Several strategies have been proposed for the decontamination of wastewater in terms of heavy metal ions. Among these, methods utilizing adsorbent materials are preferred due to their cost-effectiveness, simplicity, effectiveness, and scalability for treating large volumes of contaminated water. In this context, heavy metal removal by hydrogels based on naturally occurring polymers is an attractive approach for industrial wastewater remediation as they offer significant advantages, such as an optimal safety profile, good biodegradability, and simple and low-cost procedures for their preparation. Hydrogels have the ability to absorb significant volumes of water, allowing for the effective removal of the dissolved pollutants. Furthermore, they can undergo surface chemical modifications which can further improve their ability to retain different environmental pollutants. This review aims to summarize recent advances in the application of hydrogels in the treatment of heavy metal-contaminated wastewater, particularly focusing on hydrogels based on cellulose and cellulose derivatives. The reported studies highlight how the adsorption properties of these materials can be widely modified, with a wide range of adsorption capacity for different heavy metal ions varying between 2.3 and 2240 mg/g. The possibility of developing new hydrogels with improved sorption performances is also discussed in the review, with the aim of improving their effective application in real scenarios, indicating future directions in the field.

Ultrafast and highly efficient Cd(II) and Pb(II) removal by magnetic adsorbents derived from gypsum and corncob: Performances and mechanisms

The utilization of gypsum and biomass in environmental remediation has become a novel approach to promote waste recycling. Generally, raw waste materials exhibit limited adsorption capacity for heavy metal ions (HMIs) and often result in poor solid–liquid separation. In this study, through co-pyrolysis with corncob waste, titanium gypsum (TiG) was transformed into magnetic adsorbents (GCx, where x denotes the proportion of corncob in the gypsum–corncob mixture) for the removal of Cd(II) and Pb(II). GC10, the optimal adsorbent, which was composed primarily of anhydrite, calcium sulfide, and magnetic Fe3O4, exhibited significantly faster adsorption kinetics (rate constant k1 was 218 times and 9 times of raw TiG for Cd(II) and Pb(II)) and higher adsorption capacity (Qe exceeded 200 mg/g for Cd(II) and 400 mg/g for Pb(II)) than raw TiG and previous adsorbents. Cd(II) removal was more profoundly inhibited in a Cd(II) + Pb(II) binary system, suggesting that GC10 showed better selectivity for Pb(II). Moreover, GC10 could be easily separated from purified water for further recovery, due to its high saturation magnetization value (6.3 emu/g). The superior removal capabilities of GC10 were due to adsorption and surface precipitation of metal sulfides and metal sulfates on the adsorbent surface. Overall, these waste-derived magnetic adsorbents provide a novel and sustainable approach to waste recycling and the deep purification of multiple HMIs.

Porous Silicon Nanoparticles Conjugated Magnetite‐Chitosan Graphene Oxide Nanoparticles for Effective Removal of Complex Pollutants

AbstractThe effective removal of complex pollutants is extremely challenging for environmental and material science, especially pollutants including detergents and pesticides do not decompose or degrade in the aquatic environment which cannot be easily removed. Here, a novel biocompatible superparamagnetic nanocomposite integrating the advantages of porous silicon nanoparticles is developed, the chelation ability of chitosan, and graphene‐oxide‐iron that can simultaneously adsorb complex hydrophobic and hydrophilic pollutants on their internal and external surfaces which have significantly improved pollutant removal efficiency over the current existing methods. A porous silicon nanoparticle (PSi) conjugated magnetite‐chitosan‐reduced graphene oxide (MCRGO) nanoparticles (PSi‐MCRGO) are synthesized for complete removal of detergent, pesticide, and toxic heavy metals cadmium and lead ions from water at a favorable room temperature. The adsorption behavior of the nanocomposites fits well with the Freundlich isotherm and pseudo‐second‐order kinetics model by adsorption mechanism. Moreover, the fresh and recycled nanocomposites are easily separated by an external magnetic field for reusability due to super magnetite response and show high binding capacity for toxic heavy metal ions. Furthermore, the nanocomposites are biocompatible and reusable, and for the fourth time, recycled nanocomposites can completely remove toxic heavy metals. Overall, the novel nanocomposites completely remove complex pollutants which hold great potential for real water treatment.

Sulu Çözeltilerden Civa(II) İyonlarının Adsorpsiyonunda Hidroklorik Asit İle Modifiye Edilmiş Kilin Kullanılması

With their natural abundance and minimal processing requirements, clays hold the potential to serve as economical adsorbents for various heavy metals. In this research, the adsorption capacity of hydrochloric acid (HCl) modified clay to adsorb mercury(II) (Hg2+) ions from aqueous solutions was investigated. The parameters affecting the adsorption capacity were determined by studying the initial metal ion concentration, contact time, and temperature effects. For natural clay, an optimal initial concentration of 400 mg/L and a contact time of 50 minutes were identified. Meanwhile, modified clay showed best results with an initial concentration of 400 mg/L and a contact time of 60 minutes for Hg2+ ions. The analysis of isotherm data revealed that the Langmuir isotherm model exhibited the best fit for both materials in Hg2+ ion adsorption. At temperatures of 298 K, 308 K, and 318 K, the adsorption capacity for natural clay and Hg2+ ions were found to be 4.56, 5.01, and 5.08 mg/g, respectively. Meanwhile, the modified clay displayed adsorption capacities of 11.12, 11.37, and 12.30 mg/g for Hg2+ ions at the same temperatures. Additionally, the kinetic analysis determined that the pseudo-second-order kinetic model was the best fit for both materials in Hg2+ ion adsorption. The adsorption experiments investigated the adsorption mechanisms of Hg2+ metal ions on both natural clay and modified clay, with results indicating that the modified clay had a higher adsorption capacity for metal ions compared to the raw clay.

A trifecta membrane modified by multifunctional superhydrophilic coating for Oil/Water separation and simultaneous absorption of dyes and heavy metal

Adsorption and separation are the most important chemical engineering processes for wastewater treatment. Exerting microfiltration membranes as the central separation technology and decorating them with absorption property, forming absorptive membranes, result in the separation and purification of diverse wastewaters in an energy-efficient manner. Herein, a versatile polyanionic coating with superhydrophilicity/underwater superoleophobicity, superior anti-oil-fouling, and efficient charges is acquired through mussel-inspired co-deposition, followed by b-PEI functionalization, N-alkylation, and anionization. Thanks to the superhydrophilicity/underwater superoleophobicity, the as-prepared microfiltration membrane achieves selective separation of oil/water emulsions. Meanwhile, the functional membranes exhibited excellent selective and efficient adsorption capacity for organic dyes and heavy metal ions due to the abundant surface charges. Interestingly, benefiting from superhydrophilicity and considerable surface charges, the as-designed microfiltration membrane can realize selective and efficient simultaneous adsorption and separation of wastewaters with complicated components, including oil/water emulsions, organic dyes, and heavy metal ions by the concept of “achieving three things at one stroke”. Such a versatile and feasible strategy could pave a new path for constructing multifunctional membranes for complex wastewater treatment and purification.

Blend of polyvinylpyrrolidone/thermally reduced graphene for adsorption of heavy metal ions in water

This paper presents the preparation of a modified polyvinylpyrrolidone (PVP)/graphene mixture and evaluates its adsorption capacity for heavy metal ions in water. Graphene with a high specific surface area of about 362 m2 g−1 was obtained through the thermal separation of graphite oxide (GO), which had been synthesised from graphite by the Hummer method. The graphene-PVP blend was prepared by dispersing the graphene into a PVP solution and then crosslinking it to prevent washout by water. This crosslinking ensured a well-dispersed and stable graphene-PVP blend. The maximum adsorption capacity of graphene-PVP for Cu2+ and Cd2+ ions was found to be 158 mg g−1 and 134 mg g−1, respectively, at pH 3 and a contact time of 30 min. The experimental results were found to be consistent with Langmuir and pseudo-second-order kinetic models. The study further reveals that the adsorption mechanism of Cu2+ and Cd2+ ions on graphene-PVP follows an ion exchange mechanism, driven by strong interactions between PVP and metal ions. The study provides an easy, low-cost, and eco-friendly method to produce highly adsorptive graphene-PVP materials.

Mild and recyclable ethylenediamine pretreatment for bacterial cellulose fermentation and lignin valorization

In this study, a novel mild and recyclable ethylenediamine (EDA) pretreatment method was developed. This pretreatment process efficiently eliminated lignin and facilitated the recovery of pretreatment reagents. Under optimized conditions at 70 °C, more than half of lignin was removed from the corn stover (CS). Consequently, the enzymatic hydrolysis of glucose and xylose achieved yields of 82.1% and 50.4%, respectively. Notably, the recovered EDA was efficiently reused and maintained comparable pretreatment efficiency even after five rounds of recovery. The pretreated CS was effectively used for bacterial cellulose fermentation without requiring additional detoxification steps. Furthermore, the analysis of EDA lignin (EL) revealed the presence of numerous amino groups introduced into the lignin structure. Subsequently, EL was used in the polyurethane (PU) foam preparation. The results revealed that EL-based PU foam featured higher compressive strength, density, thermal stability, and adsorption capacity for dyes and heavy metal ions compared with alkali lignin-based PU foam.

Preparation of mussel-inspired polydopamine-functionalized TEMPO-oxidized cellulose nanofiber-based composite aerogel as reusable adsorbent for water treatment

Water pollution is an ongoing trouble that is of significant urgency to resolve worldwide. However, traditional materials used in the process of water purification are costly and energy intensive. The preparation of low-cost, green and sustainable aerogels with low density, high porosity and high specific surface area (SSA) is a great challenge. In this paper, a mussel-inspired, low-cost, polydopamine (PDA)-functionalized TEMPO-oxidized cellulose nanofiber (TOCNF) PDA/TOCNF composite aerogel has been rationally designed and fabricated with low-density, high porosity and high SSA. The PDA/TOCNF composite aerogel shows low density (18.2 mg/cm3), high porosity (98.7 %), and large surface areas (41.3 m2/g). The resulting PDA/TOCNF composite aerogel could adsorb a maximum of 314.6 mg/g of methylene blue (MB). The recycle experiment for reusing of adsorbent showed that after five consecutive cycles, the removal ability of MB by the PDA/TOCNF composite aerogel still maintained higher than 90 %. In addition, the PDA/TOCNF composite aerogel also had a high adsorption capacity of heavy metal ions, for example, it adsorbs 446.0 mg/g of Cu2+, 222.0 mg/g of Pb2+, 267.0 mg/g of Cd2+, and 600.0 mg/g of Fe3+, respectively. The possible adsorption mechanisms imply that the PDA/TOCNF composite aerogel adsorbs MB due to the synergistic binding interactions, such as electrostatic attraction, π-π stacking interaction, Vander waals force, and hydrogen bonding. Similarly, the PDA/TOCNF composite aerogel adsorbs metal ions due to the electrostatic attraction and chelation of metal ions with the PDA/TOCNF aerogel. Therefore, PDA/TOCNF composite aerogels may have potential applications in wastewater treatment because of their sustainability and low energy consumption.

Cellulose phosphonate/polyethyleneimine nano-porous composite remove toxic Pb(II) and Cu(II) from water in a short time

Current cellulose-based adsorbents suffer from the drawbacks of low adsorption capacity or slow adsorption rate for heavy metal ions. It is imperative to prepare new cellulose-based materials to improve the adsorption ability. In this work, we aim to introduce phosphonate groups to improve the adsorption ability of cellulose and select polyethyleneimine (PEI) for synergistic adsorption. A novel cellulose phosphonate/polyethyleneimine composite (MCCP-PEI) is prepared via the Mannich reaction. The structure and composition of MCCP-PEI are characterized by various advanced microscopy and spectroscopy techniques, and the results show that MCCP-PEI possesses abundant nano-porous structure, strong chelating sites, and excellent hydrophilicity. Besides, the adsorption behavior of MCCP-PEI for heavy metals has been systematically investigated. The results show that the adsorbent can quickly remove toxic Cu(II) and Pb(II) from water within 15 min and 20 min, respectively. The saturated adsorption capacity for Cu(II) and Pb(II) is 250.0 and 534.7 mg·g−1, respectively. X-ray photoelectron spectroscopy analysis combined with Density Functional Theory calculations reveal that the adsorption mechanism is chemical complexation and electrostatic attraction, and the phosphonate group plays a key role in the adsorption process.

Selective adsorption of heavy metal ions by different composite-modified semi-carbonized fibers

Highly efficient remediation materials can treat wastewater contaminated by heavy metals. In this study, semi-carbonized plant fiber (Spf) and chemical fiber (Spf) were prepared as the research material. Dodecyl dimethyl betaine and chitosan were used to singly modify semi-carbonized fibers (Sfs). Then, the single-modified Sfs were remodified by sodiumalginate to produce composite-modified Sfs. The microscopic morphology of the tested materials was studied by using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, energy dispersion spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and specific surface area (SBET) detection. The selective adsorption effect of the tested materials on water polluted by multiple heavy metals was studied, and the effects of temperature, pH, and ionic strength were compared. SEM, FTIR, and TG results proved that single and composite modifiers were modified on the surface and changed the surface properties of Spf and Scf. The metal ion adsorption capacity of modified Spfs was higher than that of modified Scfs. The maximal adsorption capacity of metal ions on test materials presented the trend of Zn(II) > Cd(II) > Pb(II). The optimum adsorption conditions were 30 °C, pH = 6, and ionic strength of 0.1 mol/L, and the adsorption process was a spontaneous, endothermic, and entropy-increasing reaction. Electrostatic adsorption, precipitation, complexation, and ion exchange were the forms of adsorption for heavy metal ions. SBET and cation exchange capacity of the modified Sfs were the key factors that determine the adsorption capacity of heavy metal ions.

Tuning surface functionalizations of UiO-66 towards high adsorption capacity and selectivity eliminations for heavy metal ions

Zr-based metal-organic frameworks (MOFs), especially the UiO-66 family, present a huge application potential for the sorptive eliminations of heavy metal ions, still most of the studies often focus on only one type of adsorbent, thus lacking in some in-depth comparisons on the microstructure produced by the organic ligands. Herein, three kinds of Zr-based MOFs (UiO-66, UiO-66-(OH)2, and UiO-66-NH2) are prepared, and their adsorption capacities for Ni2+, Fe3+ and Cr6+ are systematically investigated and compared. Results suggest that, due to a higher specific surface area of 1569.2 m2 g-1 and a larger pore volume of 0.61 cm3 g-1, the UiO-66 depicts a better adsorption performance for Ni2+ and Fe3+ with larger capacities of 6.8 and 14.1 mg g-1, respectively. The UiO-66-(OH)2 presents a specific surface area of 785.5 m2 g-1, which is a little lower than UiO-66 and UiO-66-NH2, but shows the maximum adsorption capacity of 39.0 mg g-1 for Cr6+, obviously surpassing two other counterparts. In addition, for a multi-ion aqueous solution, UiO-66-(OH)2 still has an excellent Cr6+/Ni2+adsorption selectivity of 21.7. The adsorption isotherm of Cr6+ belongs to monomolecular layer Langmuir model, further verifying -OH2+ of the UiO-66-(OH)2 surface acted as the chemical adsorption sites and attracted electronegative Cr6+-containing ions. This study dramatically highlights the importance of the organic ligands for MOFs sorbents, which may facilitate achieving their large-scale applications in wastewater treatment.

Porosint‐Supported PVDF Derivatives with Good Adsorption Performance and Recyclability for the Removal of Aqueous Heavy Metal Ions

AbstractHeavy metal ions in water can affect human health. Taking Pb2+ for an example, it can lead to kidney failure and tumor infection. Polyvinylidene fluoride (PVDF) has been widely used as filter membranes in wastewater treatment. This paper uses citric acid (CA) as the connecting arm to graft carboxymethyl chitosan (CMCS) onto PVDF and prepare a novel granular molecular sieve‐supported PVDF derivative (s‐PVDF‐CA‐CMCS). The structure was characterized and the adsorption capacity for heavy metal ions was investigated. The results indicate that s‐PVDF‐CA‐CMCS has good adsorption performance for aqueous heavy metal ions, especially for Pb2+, with a removal rate of 99.39 % and an adsorption capacity of 198.41 μg/g. The adsorption data fits the pseudo‐second‐order kinetic model (R2=0.9992), and the removal rate of Pb2+ was 78.48 % after 5 cycles of adsorptions, indicating that s‐PVDF‐CA‐CMCS may be potential applications for removing heavy metal ions in water treatment.

Silanized fiberglass modified by carbon dots as novel and impressive adsorbent for aqueous heavy metal ion removal.

This work discusses the application of a silanized fiberglass (SFG) modified by carbon dots (CDs) as an effective adsorbent for up-taking some heavy metal ions including lead (Pb2+), chromium (Cr3+), cadmium (Cd2+), cobalt (Co2+), and nickel (Ni2+) as pollutant in the aqueous solution by batch method. Removal tests were carried out after optimization of pH, contact time, initial concentration of metal ions, and CDs amount. The SFG modified with CDs (CDs-SFG) was applied for the removal of 10 ppm of each metal ion solution after 100 min and the corresponding results showed the removal efficiencies of 100, 93.2, 91.8, 90, and 88.3% for Pb2+, Cd2+, Cr3+, Co2+, and Ni2+, respectively. The adsorption capacity of CDs-SFG in the metal ion mixed solution was also evaluated, and the results indicated the same trend in the adsorption capacity for metal ions in the mixed solution, though with lower absolute values compared to the single metal solutions. Moreover, the selectivity of this adsorbent for the adsorption of Pb2+ was almost twice of other tested metal ions. The regeneration of the CDs-SFG showed that its adsorption capacity after five cycles was reduced about 3.9, 6.0, 6.8, 6.7, and 8.0% for Pb2+, Cd2+, Cr3+, Co2+, and Ni2+, respectively. Finally, the applicability of the CDs-SFG adsorbent was examined with the analysis of the metal ions in water and wastewater samples.

A Study on the Impermeability of Nanodispersible Modified Bentonite Based on Colloidal Osmotic Pressure Mechanisms and the Adsorption of Harmful Substances

With the growing demands of human beings, sanitary landfill, along with the increase in landfill depth and leachate water pressure, has put forward new and higher requirements for the impermeable layer. In particular, it is required to have a certain adsorption capacity of harmful substances from the perspective of environmental protection. Hence, the impermeability of polymer bentonite–sand mixtures (PBTS) at different water pressure and the adsorption properties of polymer bentonite (PBT) on contaminants were investigated through the modification of PBT using betaine compounded with sodium polyacrylate (SPA). It was found that the composite modification of betaine and SPA could reduce the average particle size of PBT dispersed in water (reduced to 106 nm from 201 nm) and enhance the swelling properties. As the content of SPA increased, the hydraulic conductivity of PBTS system decreases and the permeability resistance improves, while the resistance to external water pressure increases. It is proposed a concept of the potential of osmotic pressure in a constrained space to explain the impermeability mechanism of PBTS. The potential of osmotic pressure obtained by linear extrapolation of the trendline of colloidal osmotic pressure versus mass content of PBT could represent the external water pressure that the PBT resist. Additionally, the PBT also has a high adsorption capacity for both organic pollutants and heavy metal ions. The adsorption rate of PBT was up to 99.36% for phenol; up to 99.9% for methylene blue; and 99.89%, 99.9%, and 95.7% for low concentrations of Pb2+, Cd2+, and Hg+, respectively. This work is expected to provide strong technical support for the future development in the field of impermeability and removal of hazardous substances (organic and heavy metals).