Adsorption Performance Research Articles

Preparation and characterization of high-ash coal slime-based soil amendment as well as investigations of its adsorption performance and mechanisms towards heavy metals in soil

In this study, high-ash coal slime-based mineral soil amendment (MSA) was prepared via the hydrothermal method using high-ash coal slime as raw material, supplemented with activator calcium oxide and additive KOH solution. After hydrothermal treatment at 230 °C for 5 h, the original crystalline phase (quartz and kaolinite) of the high-ash slime was completely transformed into hydrotalcite zeolite, tobermorite, and silicate of potassium aluminosilicate, which has the largest specific surface area. The adsorption of Pb2+ and Cd2+ was adherent to the kinetic equation of secondary adsorption and Freundlich models, and the removal of Pb2+ and Cd2+ reached up to 362.58 mg g-1 and 64.67 mg g-1. The successive releases of SiO2 and CaO from MSA conformed to the Elovich equation, whereas the releases of SiO2 in Cd-containing environments and CaO in Pb- and Cd-containing environments more closely conformed to the power function; the releases of K2O all conformed to the first-order kinetic equation. The presence of Pb2+ and Cd2+ in the environment promotes the release of potassium and calcium elements with MSA’s ion-exchange ability, and attenuates the release of silicon elements. Combining Pb2+ and Cd2+ with silicon resulted in the intolerant precipitation of 3PbO·2SiO2 and Cd2SiO4. The mineral precipitation mechanism is the most important mechanism of MSA in immobilizing heavy metals, accounting for 72.7% to 80.5% of the total adsorption. Further contaminated soil immobilization experiments also showed that the application of MSA significantly reduced the bioavailability of soil heavy metals. When the MSA addition amount was 1.6%, the residual state increased by 63.58%. In conclusion, preparing MSA may effectively utilize coal-based solid waste with high added value.

A novel design of copper selenide/zinc selenide/Nitrogen-doped carbon derived from MOF for sulfadiazine adsorption: Performance and mechanism

Herein, a novel copper selenide/zinc selenide/Nitrogen-doped carbon (Cu2Se/ZnSe/NC) sphere was constructed via a combination of cation exchange, selenization and carbonization approaches with zinc-based metal–organic frameworks (ZIF-8) as precursor for sulfadiazine (SDZ) removal. Compared with the ZnSe/NC, the defective Cu2Se/ZnSe interface in the optimizing Cu-ZnSe/NC2 sample caused a remarkably improved adsorption performance. Notably, the adsorption capacity of 129.32 mg/g was better than that of mostly reported adsorbents for SDZ. And the adsorption referred to multiple-layer physical–chemical process that was spontaneous and exothermic. Besides, the Cu-ZnSe/NC2 displayed fast adsorption equilibrium of about 20 min and significant anti-interference ability for inorganic ions. Specially, the adsorbent possessed excellent stability and reusability, which could also be applied for rhodamine B (RhB), methylene blue (MB), and methyl orange (MO) dyes removal. Ultimately, the charge redistribution of Cu2Se/ZnSe interface greatly contributes the superior adsorption performance for SDZ, in which electrostatic attraction occupied extremely crucial status as compared to π-π electron-donor–acceptor (π-π EDA) interaction and hydrogen bonding (H-bonding), as revealed by the density function theory (DFT) calculations and experimental results. This study can provide a guideline for design of high-efficient adsorbent with interfacial charge redistribution.

Scalable, acid-resistant polyaniline deposited amidoxime PAN nanofibers for efficient adsorption and detoxification of Cr(VI) wastewater

Chromium (Cr(VI)) metal ions used in industries pose a serious threat to the health of humanity due to the challenge of removal from wastewater and high biotoxicity. Herein, a novel stable and scalable amidoxime modified polyacrylonitrile/polyaniline (AOPAN/PANI) nanofibers membrane (NFM) was prepared via a combined facile electrospinning and interfacial polymerization strategy, and investigated Cr(VI) adsorption performances by batch experiments. The adsorption kinetics, influencing factors, and removal mechanism of Cr(VI) through the scalable AOPAN/PANI NFM was systematically analyzed. The results indicated that the scalable AOPAN/PANI NFM was successfully prepared, and exhibited excellent Cr(VI) absorption capacity (299.56mg/g), moreover, the prepared NFM exhibits good acid-resistance(pH=2). The pseudo-second-order model conformed to the adsorption kinetics, and the results from batch experiments were matched by the Langmuir adsorption isothermal model. The adsorption of Cr(VI) by the scalable AOPAN/PANI-16 NFM is a non-spontaneous exothermic process. The adsorption mechanism includes electrostatic interaction of Cr(VI) and the scalable AOPAN/PANI NFM, and convert Cr(VI) into low toxicity Cr(III) and chelate. In addition, the scalable AOPAN/PANI nanofibers membrane has good reusable performance. More importantly, this work fully demonstrates the great technical advantages of the industrial application of preparing adsorbent by electrospinning, and provides a novel stable, simple and efficient treatment method for the detoxification treatment of Cr(VI) in acid wastewater.

Metal oxide modified MCM-41 on simultaneous removal of HF and HCl: Experimental and theoretical studies

To address the issue of harmful gases Hydrogen fluoride (HF) and hydrogen chloride (HCl) in metallurgical waste gas, this study utilized metal oxide modified molecular sieve (MCM-41) for their simultaneous removal. The adsorption and removal of HF and HCl are mainly influenced by alkaline sites and pore structure, with alkaline sites having a greater impact. MgO affects the alkaline site strength and pore structure, thereby facilitating the removal of HF and HCl. On the surface of the adsorbent, HF and HCl react to form MgF2 and MgCl2, which gradually reduces the adsorbent's performance. HF and HCl have a higher adsorption strength on the MgO surface, and the H…O interaction causes a more stable adsorption configuration. There is a competitive adsorption effect between HF and HCl, with HF having a preference for adsorbing on the MgO surface over HCl. The adsorption energies of HF and HCl are unlimited by adsorption effects. When the O atom in MgO is replaced by HF and HCl, Mg-F bonds, Mg-Cl bonds, and H-O bonds are formed, resulting in the formation of MgF2, MgCl2, and H2O. HF is easier to prioritize removal than HCl

A novel loofah-like chitosan/alginate composite aerogels prepared for efficient removal of perchlorate: Experimental and DFT study

Perchlorate, an emerging contaminant in drinking water, has attracted global attention. In this study, a novel loofah-like porous chitosan/alginate composite aerogel (CTS/SA-m) was fabricated using ionotropic pregelation and freeze-dried technology to effectively adsorb perchlorate. The performance, isotherms, thermodynamics, and kinetics of perchlorate adsorption by CTS/SA-m were systematically discussed. The results showed that the loofah-like CTS/SA-m with high hydrophilicity exhibited excellent adsorption properties. Over 95 % of the removal rate in 10 min can be achieved, with initial concentration of perchlorate and CTS/SA-m dosage of 10 mg/L and 2 g/L, respectively. And 70.15 mg/g of equilibrium adsorption capacity of perchlorate could be reached at pH 5 and 298 K. pH had little effect on the removal rate of perchlorate, the removal rate surpassed 85 % over a wide pH range of 3.0–11.0. Multilayer adsorption (MLA), intraparticle diffusion (IPD), and adsorption on the active site (AOAS) models were employed to discuss the adsorption mechanism of perchlorate. It was confirmed that double-layer chemisorption played a dominant role. Density functional theory (DFT) analysis of binding energy revealed the effect of functional groups on the ClO4− adsorption strength in the order of –NH3+ > –COOH > –NH2 > –OH. Furthermore, electrostatic potential and the independent gradient model confirmed that electrostatic interactions, hydrogen bonding, and van der Waals forces contributed to the highly efficient adsorption of perchlorate. These findings have a vital promoting effect on perchlorate removal technology in water treatment. Moreover, the loofah-like CTS/SA-m aerogel material, exhibiting outstanding performance, shows great potential in effectively in trapping perchlorate anions from aquatic systems.

Effective microwave regeneration of natural sepiolite and montmorillonite as adsorbents for tetracycline removal and mechanism insight

Natural clay minerals such as sepiolite (Sep) and montmorillonite (Mt) are used as low-cost adsorbents to remove tetracycline (TC) in water, and the spent adsorbents saturated with TC are regenerated under microwave (MW) irradiation. The adsorption and regeneration properties of Sep and Mt are compared. The possible adsorption and MW regeneration mechanisms are proposed. The results show that 11.25 mg·g−1 and 20.74 mg·g−1 adsorption capacities of Sep and Mt are obtained, respectively, within 120.0 min at 298 K. Mt has higher adsorption capacity, faster adsorption rate and shorter adsorption time for TC than that of Sep. The adsorption processes using Sep and Mt are well-fitted to pseudo-second-order kinetics and Langmuir models. The two adsorption reactions are spontaneous and endothermic, with increased randomness at solid–liquid interfaces. Moreover, 89.76 % and 114.45 % maximum regeneration ratios are obtained for Sep and Mt, respectively. Mt exhibits superior regeneration performance than Sep. After eight adsorption-regeneration cycles, the two adsorbents can maintain excellent adsorption and regeneration performance. This work provides new perspectives on the adsorption technology using natural clay minerals to remove antibiotics and the MW regeneration technology to regenerate spent natural clay minerals saturated with organic pollutants in organic wastewater treatment.

Preparation of silver nitroprusside nanoparticles for enhanced acid red 94 removal from effluent: A study on synergistic adsorption and photocatalytic processes, with toxicological assessment

Toxic dye pollution in water is an urgent global environmental issue. The synergistic action of adsorption and degradation has shown great removal effects for treating toxic dyes in aqueous environments. Silver ions and nitroprusside salts exhibit excellent antimicrobial, anticancer, and biocompatibility properties and are widely used in the pharmaceutical field; however, their application in environmental treatment has not been extensively explored. Hence, we prepared novel and highly efficient silver nitroprusside nanoparticles (Ag2[Fe(CN)5NO] NPs) through a one-pot reaction using sodium nitroprusside and silver nitrate for the first removal of acid red dye (AR 94). Furthermore, Ag2[Fe(CN)5NO] NPs were characterized using various analytical techniques. The Ag2[Fe(CN)5NO] NPs have both cubic and rod-like structures with a size of 107.46 ± 34.54 d.nm, the PDI is 0.263 ± 0.018 and the zeta potential is −46.9 ± 0.026 mV. In addition, the synergistic adsorption and degradation performance of Ag2[Fe(CN)5NO] NPs was evaluated. The removal efficiencies of Ag2[Fe(CN)5NO] NPs on AR 94 can reach more than 95 % under natural light irradiation and optimal reaction conditions of 60 mg/L AR 94 dye concentration, pH 6, temperature 45 °C, and time 6 h. After 5 cycles of recycling, the removal efficiency remained above 90 %. The aqueous solution obtained after removing AR 94 demonstrated no adverse effects on Zea mays L. seed growth. It also exhibited low toxicity to Artemia salina. These results emphasize the potential of Ag2[Fe(CN)5NO] NPs as an efficient and environmentally friendly material for the removal of dyes from aqueous environments.

New insights on antimony removal and recovery from water and wastewater using iron-coated cork granulates: Desorption on batch and fixed-bed column systems

This work investigated Sb adsorption–desorption using iron-coated cork granulates (ICG) in both batch and continuous modes to evaluate the materiaĺs adsorption and regeneration performance, as well as the possibility of antimony recovery. A fixed-bed column filled with ICG, demonstrated maximum adsorption capacities of 13 ± 2 mg g−1 and 10 ± 1 mg g−1 for Sb(III) and Sb(V), respectively, at pH 3. ICG was able to remove Sb within the WHO guideline of 20 μg/L at pH 6. Among the different classes of eluents tested for Sb(V) desorption, the acids achieved the highest desorption rates − 81 ± 9 % and 66 ± 8 % for HCl 1 M and ascorbic acid 0.1 M, respectively. The desorption kinetics showed that HCl 1 M reached equilibrium in 4 h, but ascorbic acid 0.1 M took 16 h. This work presents an ecological emerging solution for antimony removal and recovery from water and wastewater

Novel alkali intercalated and acid-exfoliated biochars with enhanced surface areas for contaminant adsorption applications

Cost-effective and eco-friendly adsorbents are essential in environmental engineering and biochar is a promising material from the perspective. A novel and efficient surface modification approach involving alkali intercalation and acid exfoliation was designed in this study to enhance the physicochemical properties of biochar. The alkali intercalation process utilizes potassium hydroxide (KOH), while acid exfoliation involves varying HNO3, H2SO4, and H3PO4 concentrations. A simple two-stage pyrolysis process was employed to facilitate the intercalation-exfoliation modification. The modified biochars were characterized using BET, SEM, XRD, etc., to understand physicochemical properties. To quantify the effectiveness of the modifications, adsorption of malachite green dye as a model moiety was investigated. Dye removal sorption rates exceeding 99 % were recorded in the case of the biochars modified through a two-step process using KOH and 0.1MH3PO4. Specifically, the highest contaminant removal of 99.9 % was recorded when 60 mg of the KOH-0.1MH3PO4 biochar was employed, which is significantly higher than unmodified biochar’s 45.41 % removal at a higher dosage of 100 mg. Moreover, the adsorption kinetics revealed that all the modified biochars attained the maximum removal concentrations (∼99 % removal) in a mere 300 min, indicating a tenfold improvement in adsorption rate from unmodified biochar's requirement of over 5000 min. The results achieved through this study provide a cost-effective, fast, and environment-friendly technology for enhancing the adsorption characteristics and performance of biochars toward contaminant removal.

Treatment of Water Contaminated by Ship Oil: Study of Adsorption in a Fixed-Bed Column

Aquatic macrophytes like Salvinia sp. have rapid proliferation and a great capacity for ecological adaptation. In addition to these characteristics, this study points to their ability to adsorb contaminants such as dyes, metals, and oils. This work aims, through an adsorption study, to propose an alternative treatment using chemically modified Salvinia sp. (SOH) biomass to remove oil from water. Batch adsorption experiments were performed to observe the effects of concentration, pH, time, temperature, desorption, and reuse of the biomass. The adsorption mechanisms, performance, kinetics, isotherm, thermodynamics, and reusability of biomass were evaluated. Both adsorbents were well-defined by the Freundlich model isotherm. According to the results obtained, the qmax was 898.0 mg g−1 for SOH in oil-in-salt water emulsion in 15 min and 930.59 mg g−1 for Salvinia sp. in natura (SS) in the oil-in-water emulsion. In the fixed-bed column adsorption, the adsorption capacity was 2.99 g g−1 for SS and 3.49 g g−1 for SOH, and the saturation capacity was 42.89 g g−1 SS and 42.99 g g−1 SOH. According to the adsorption models, the Bohart–Adams model best fits the experimental data of this study. The SOH adsorbed oil recovery test was successful, with 100% oil recovery.

Hydrophobic CHA-ZIFs with a junctional trap between cha and d6r cages for adsorption of 2,3-butanediol in aqueous solution

The adsorption and separation of diols from dilute aqueous solution using hydrophobic materials is very challenging due to the strong diol–water hydrogen-bonding interactions. Herein, we screened hydrophobic zeolitic imidazolate frameworks (ZIFs) with chabazite (CHA) topology for separation of 2,3-butanediol (2,3-BDO) and 1,3-propanediol (1,3-PDO), which had junctional and hydrophobic traps matching the two end methyl groups of the 2,3-BDO molecule. Based on CHA-ZIFs with the same small-sized ligand 2-methylimidazole (mIm) and different large-sized ligand benzimidazole derivatives (RbIm), CHA-ZIFs with larger surface areas were obtained by the addition of excess small-sized ligand mIm in the synthesis process. We showed that all of the hydrophobic CHA-ZIFs preferentially adsorbed 2,3-BDO over 1,3-PDO by static batch adsorption and dynamic column adsorption experiments. But ZIF-301 and ZIF-300 with halogen groups exhibited better adsorptive separation performance for 2,3-BDO/1,3-PDO than ZIF-302 with methyl groups. For a typical ZIF-301, its adsorption capacity for 2,3-BDO was 116.4 mg·g–1 and selectivity for 2,3-BDO/1,3-PDO was 3.8 in dynamic column adsorption of the binary-component system (2,3-BDO/1,3-PDO: 50/50 g·L–1). Computational simulations revealed that 2,3-BDO preferentially adsorbed in a trap at the junction between the cha and d6r cages of CHA-ZIFs, meaning the strong host–guest interactions. Therefore, the hydrophobic CHA-ZIFs with a junctional trap were promising candidate materials for adsorbing 2,3-BDO, which also provided a new perspective for separating diols in dilute aqueous solutions.

Development of energy efficient flower-shaped defective TiO2 materials for wastewater remediation of agro-industries and oil refineries

Wastewater containing high concentrations of phenolic compounds (PhCs), produced in large quantities by the world's expanding agro-industries and oil refineries, is one of the main polluters of rivers and streams. It is economically and technically reasonable to treat such wastewater using TiO2-based photocatalysis. But in order for photocatalysis to be used on a large scale, it must degrade PhCs efficiently while using less electrical energy (EE) and treating them at lower costs (t-cost). In this study, a modified hydrothermal method was used to produce the flower-shaped defective black TiO2 (BTNFs) from pre-prepared black TiO2 nanoparticles (BTNPs) as an energy saving strategy in wastewater remediation. The adsorption and photocatalytic performance, energy needs, and t-costs for both materials were examined for photodegradation of PhCs from simulated oil refinery wastewater (ORW), palm oil mill wastewater (POW), and olive oil mill wastewater (OMW). The findings revealed that BTNFs have improved properties which made them more effective in adsorption of PhCs and photocatalyzing their degradation. Combining photocatalysis and adsorption based on BTNFs led to an improved removal (49.75–98.40%) of PhCs depending on the wastewater matrix and reduced the EE consumption and t-cost by 8.96–23.86% for treating OMW, POW, and ORW.

Zirconium‑cerium modified polyvinyl alcohol/NaCMC biocomposite film: Synthesis of films through high-speed shear assisted technique and removal fluoride from water

A new zirconium and cerium-modified polyvinyl alcohol (PVA) sodium carboxymethyl cellulose (NaCMC) film (PVA/CMC-Zr-Ce) was synthesized thru a high-speed shear-assisted method and its adsorption for the removal of fluoride was studied, in which the NaCMC provided –COONa for ion exchange between Na and Zr-Ce, thus the loading amount of Zr-Ce on films was accordingly increased. The morphology and structure of PVA/CMC-Zr-Ce were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Besides, the mechanical properties, water contact angle, and swelling ratio of film were also evaluated. The addition of high-speed shear improved the dispersion of the emulsion system, and PVA/CMC-Zr-Ce film with good adsorption performance and film stability was prepared. While, it was found that the adsorption capacity could reach 67.25 mg/g and equilibrium time could reach 20 min. The adsorption mechanism of PVA/CMC-Zr-Ce revealed that ion exchange between hydroxide and fluoride, electrostatic interactions and complexation were the dominating influencing factors. Based on these findings, it can be concluded that PVA/CMC-Zr-Ce film- synthesized with high-speed shear assistance technique is a promising adsorbent for fluoride removal from water.

Nanocrystalline sodium mordenite as an efficient low-concentration CO2 adsorbent

Systematic control of the crystal size and morphology of zeolites to enhance their CO2 adsorption performance is of great importance from both environmental and economic perspectives. Here we report the seeded synthesis of sodium mordenite (Na-MOR) with a Si/Al ratio of 4.9 and an average crystal length and width of 70 and 40 nm, respectively, using γ-aminobutyric acid as a crystal growth inhibitor in the absence of any organic structure-directing agent (OSDA). This nanozeolite shows an unprecedented CO2 capacity of 1.58 mmol g−1 under dynamic direct air capture (DAC) conditions at 25 °C, which is approximately 40 % greater than the value (1.15 mmol g−1) of the best zeolite adsorbent (an unidentified OSDA-directed Na-MOR (Si/Al = 5.0) zeolite with Na+ enrichment in 8-ring side pockets), mainly due to its nanocrystalline nature. It has also been characterized by much faster CO2 adsorption kinetics (ca. 5 vs. 50 min equilibration time) compared to a commercial Na-MOR zeolite with Si/Al = 5.0. Our study paves the way for developing a more efficient zeolite-based DAC adsorbent.

Self-sacrificing template synthesis of ultralight porous hydroxyapatite microtube-based ceramics for hemoglobin adsorption

Strong and porous hydroxyapatite ceramics are highly desired for biomedical materials. However, 1D hydroxyapatite crystals with enhanced bioactivity, densification, and sinterability are limited in practical application for self-agglomeration and unfavorable 3D morphology. Herein, a sacrificed template approach is developed to prepare ultralight porous hydroxyapatite microtube-based ceramics (HMTC). First, hydroxyapatite microtubes (HMTs) are self-assembled proceeding from nanowires to microtubes through a solvothermal reaction. Then, HMTs are shaped into 3D columns by using chitosan aerogel as a template and sintered at 1300 °C to obtain ultralight porous ceramics. The chitosan template considerably contributes to constructing the macro-meso-microporous architecture of HMTC, thereby benefiting the loading capacity, biomolecule migration, cell proliferation, and other biomedical applications. HMTC exhibits ultralight weight but excellent compressive resistance to bear objects weighing hundreds of times more. HMTC exhibits a high adsorption capacity (311 mg g−1) towards bovine hemoglobin (BHb) at the pH near pI by the driving force of ionic interaction and hydrophobic interaction. The adsorption kinetics and fixed-bed adsorption confirm that the physisorption process is controlled by the intraparticle diffusion of BHb. The excellent protein adsorption performance and good recyclability demonstrate the biological availability of HMTC.

Highly adsorptive removal of heavy metal, dye, and antibiotic pollutants using functionalized graphene nanosheets sono-electrochemically derived from graphitic waste

The development of highly adsorptive materials at low cost is critically important for efficient treatment of industrial wastewater. We herein report a one-step sonoelectrochemical strategy to synthesize functionalized graphene (FG) nanosheets as an effective adsorptive material using graphite waste from spent household batteries. Scanning/transmission electron and Raman microscopy studies reveal that the as-synthesized nanosheets are composed of few (2–6) graphene layers. Additionally, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses imply the presence of oxygen functional groups on the nanosheets (C=O and -COOH, oxygen content of 4.29%), which are immensely beneficial for the electrostatic adsorption with heavy metals, dyes, and antibiotics in aqueous solutions. As expected, FG nanosheets exhibit potent capabilities of handling a wide range of pollutants, such as methylene blue, methyl orange, enrofloxacin, and Pb2+, with high adsorption performances (99.95% and 21.21mg/g for Enrofloxacin, 98.93% and 119.3mg/g for methylene blue, 95.82% and 25.67mg/g for methyl orange, 95.56% and 86.10mg/g for Pb2+). These findings therefore show a great promise for practical uses of the FG material as efficient adsorbents in eliminating metallic, organic, and antibiotic pollutants in water.

Cellulose-based adsorbent using in mercury detection and removal from water via an efficient grafting strategy of fluorometric sensors by click reaction

Mercury pollution in waters attracts lots of attention due to its serious toxicity and high bioenrichment and many efforts have been devoted in the development of adsorbents for mercury detection and removal. Herein, a cellulose-based adsorbent Cell-TriA-HQ is functionalized with quinoline fluorophore by covalent immobilization through “Click reaction” with high yield. In addition to the admirable adsorptive performance, the prepared adsorbent exhibits excellent selectivity and sensitivity towards Hg (II) in water that the detection limit for Hg (II) is determined to be as low as 1.92 × 10−7 M. The sensitive fluorescence enhancement response is considered to be resulted from the inhibition of photo-induced electron transfer between triazole and quinoline groups and the reinforcement of structural rigidity. The easy manipulation along with excellent performance of adsorption capacity, detective ability and reusability for the multifunctional adsorbent makes it potential in mercury monitoring and removal from aqueous solutions in the field of water treatment.

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.

Ultra-high capacity and anti-interference for Cr(VI) removal by tannin-polyvinylimine modified graphite carbon nitride

To combat the increasingly serious water pollution caused by heavy metal ions, the development of efficient adsorbents is of great significance. In this study, a novel composite adsorbent for Cr(VI) removal was smartly designed using environmentally friendly materials such as tannic acid (TA) and polyethyleneimine (PEI) for surface modification of g-C3N4 nanosheets through covalent assembly of polyphenols and amines. The obtained (PEI-TA)-g-C3N4 composite was capable of efficiently and quickly adsorbing Cr(VI) in water, with a maximum adsorption capacity of 769.23mg/g at 308K (35 °C), which was much higher than most reported Cr(VI) adsorbents. Notably, (PEI-TA)-g-C3N4 could reduce highly toxic Cr(VI) to low toxic Cr(III) and effectively adsorb it. The Cr(VI) adsorption process was a spontaneous thermal adsorption process that conformed to the pseudo-second-order kinetic model and Langmuir isotherm model. In addition, the excellent photothermal performance of (PEI-TA)-g-C3N4 further accelerated the adsorption of Cr(VI). Moreover, the strong anti-interference ability of (PEI-TA)-g-C3N4 composite against anions and other metal ions enabled it to effectively remove Cr(VI) in complex environments, expanding its practical application scenarios. The polymer coatings rich in phenolic hydroxyl- and amine-rich formed on the large surface area of g-C3N4 and the protonation of the amino groups are the keys for (PEI-TA)-g-C3N4 composite to have ultra-high adsorption performance and strong anti-interference ability towards Cr(VI). The designed strategy of this metal-free and environmentally friendly composite with ultra-high removal of Cr(VI) capability from wastewater provides new ideas for developing green, inexpensive, and efficient adsorbents.

Determination of structure stability and adsorption performance of Li1.33Mn1.67O4 adsorbents

Adsorbents based on lithium manganese double oxides Li1.33Mn1.67O4 with a spinel structure were synthesized using the sol–gel method. The influence of temperature during synthesis and conversion to the H-form, as well as the conditions of the adsorption experiment, on the adsorption capacity of the resulting adsorbents was investigated. It was found that increasing the synthesis temperature of Li1.33Mn1.67O4 oxides from 500 to 600 °C leads to a decrease in the adsorption capacity for Li+ ions from 6.60 to 1.62 mmol g−1 at an adsorption temperature of 50 °C.