Simultaneous Immobilization Research Articles

High-Pressure Freezing Followed by Freeze Substitution: An Optimal Electron Microscope Technique to Study Golgi Apparatus Organization and Membrane Trafficking.

A major goal of structural biologists is to preserve samples as close to their living state as possible. High-pressure freezing (HPF) is a state-of-art technique that freezes the samples at high pressure (~2100bar) and low temperature (-196°C) within milliseconds. This ultrarapid fixation enables simultaneous immobilization of all cellular components and preserves the samples in a near-native state. This facilitates the study of dynamic processes in Golgi apparatus organization and membrane trafficking. The work in our laboratory shows that high-pressure freezing followed by freeze substitution (FS), the introduction of organic solvents at low temperature prior to plastic embedding, can better preserve the structure of Golgi apparatus and Golgi-associated vesicles. Here, we present a protocol for freezing monolayer cell cultures on sapphire disks followed by freeze substitution. We were able to use this protocol to successfully study Golgi organization and membrane trafficking in HeLa cells. The protocol gives decidedly better preservation of Golgi apparatus and associated vesicles than conventional chemically fixed preparation and as a plastic embedded preparation can be readily extended to 3D electron microscopy imaging through sequential block face-scanning electron microscopy. The 3D imaging of a multi-micron thick organelle such as the Golgi apparatus located near the cell nucleus is greatly facilitated relative to hydrated sample imaging techniques such as cryo-electron microscopy.

Simultaneous lipase production and immobilization: morphology and physiology study of Penicillium simplicissimum in submerged and solid-state fermentation with polypropylene as an inert support.

The influence of different carbon sources (glucose (G), olive oil (O), and a combination of both (GO)) in the physiology (biomass and lipase production) and morphology (light and environmental and scanning electron microscopy) of the fungus Penicillium simplicissimum by applying submerged (SmF) and solid-state (SSF) fermentations was investigated. The cultivation was carried out using polypropylene as hydrophobic inert support in SmF and SSF to understand better the influence of a support for the fungus growth and also provides the immobilization of lipases during its production. Micrographs show different morphologies: in SSF, the fungus grows on and inside the inert support independent of the media; in SmF, the formation of high-density spherical pellets obtained in medium GO leads to the best productivity and specific product yield Yp/x..Conidiation is observed mainly in SSF, a few in SmF with polypropylene as inert support and not in SmF, which may indicate a stress condition in SSF. Possibly, the morphology acquired by the fungus under stressful conditions may be the key to the higher biomass and lipase productivity at SSF. The developed process with simultaneous production and immobilization of lipase leads to a new promissory biocatalyst once it can be directly applied with no need for downstream processes.

Simultaneous immobilization of arsenic, lead, and cadmium in soil by magnesium-aluminum modified biochar: Influences of organic acids, aging, and rainfall

Magnesium-aluminum modified biochar (MABs) has an outstanding effect on the simultaneous immobilization of arsenic (As), lead (Pb), and cadmium (Cd) in soil, but the stability of remediation effect of MAB under various natural conditions is still unknown. In this study, we investigated the effects of organic acids, dry-wet cycles (DW), freeze-thaw cycles (FT), and rainfall (pH 4, 7, and 8) on the immobilization of As, Pb, and Cd by MAB. The results showed that oxalic acid decreased the immobilization efficiencies of As, Pb, and Cd by 15.5%–38.5%; meanwhile, humic acid reduced the immobilization efficiency of Pb by 89.7%, but elevated that of Cd by 19.5%. The immobilization mechanisms of MAB-5 on three metals were mainly involved in ion exchange and surface-complexation. Compared with the 7th round, the immobilization efficiencies of As, Pb, and Cd by MAB in the 28th round was decreased by 17%–28% in DW, but was increased by 11%–18% in FT. In addition, MAB was transformed into hydrotalcite after FT and DW. After experiencing simulated rainfall, MAB caused more As, Pb, and Cd to be retained in the upper soil layer, and the immobilization effect of MBA was more significant under the stimulated rainfall with higher pH. The study provides a more theoretical basis for the application of MAB in the actual site remediation.

Constructing the active surface soil layer with ZVI-biochar amendment for simultaneous immobilization of As and Zn in both contaminated soil and groundwater: Continuous versus intermittent infiltration mode

In this study, the zero valent iron-biochar composite (ZVI-BC) was applied to construct an active surface soil layer for the simultaneous remediation of As-Zn contaminated soil and groundwater, focusing on the influence of the infiltration mode of pumped-up groundwater into soil. The active surface soil treated more contaminated groundwater for As (4.45-5.46 L kg-1 soil) than that for Zn (2.52-3.13 L kg-1 soil) under both continuous and intermittent infiltration modes, with about 98% As and 95% Zn removed from groundwater and retained in the soil. As(V) precipitated with Fe(III) due to ZVI oxidation, which was responsible for the As immobilization. The soil under the intermittent infiltration mode was enriched by the Sphingomonas with arsenate reductase gene, which promoted more reduction of As(V) into As(III) and facilitated coprecipitation of As(III) with Fe(III). The Mn oxide determined the sorption of Zn in the active soil layer, where the Hyphomicrobium, one type of manganese oxidizing bacteria, was much higher under the continuous infiltration mode, which accounted for the more Zn immobilization. After the remediation, both As and Zn immobilized in the active surface soil showed high stability, with the average downward migration rate of only 0.207-0.368 cm year-1 within 20-year rainfall exposure. Our findings indicate that this active surface soil layer is applicable for simultaneous immobilization of As and Zn in both contaminated soil and groundwater, and the groundwater intermittent infiltration could be a better option considering the remediation effectiveness, the immobilization mechanism, the long-term stability, and the energetic efficiency.

Submicron tourmaline enhanced the solidification of municipal solid waste incineration fly ash by chemical structure reorganization and stabilized heavy metals

Municipal solid waste incineration fly ash (MSWIFA) exsits in large quantitities and contains pollutants such as heavy metal. While solidification is one of the most effective methods for treating MSWIFA, this application is limited by cost, subsequent treatment, and simultaneous immobilization of anions and cations. This research demonstrated that under a certain initial pressure (20 MPa), a gelation reaction involving ball milling-modified tourmaline powder, a small amount of cement clinker, and MSWIFA forms a stable consolidated body and significantly reduces the risk of heavy metal dissolution. The consolidated MSWIFA can easily be formed into unfired bricks in large-scale pilot production, and a response surface model was used to optimize the experimental parameters. When the mass ratio of tourmaline: cement clinker: MSWIFA was 15:15:200 (mixed with a moisture content of 13 to 15 %), the compressive strength of the consolidated body reached 13 MPa, and the amounts of Cr and Pb leached decreased from 12 mg/L to 0.1 mg/L and 25 mg/L to 0.3 mg/L, respectively. The consolidated form contained a new mineral phase (Ca3Si2O7·3H2O, Ca10Mg0.8(SiO4)0.6O2Cl, and CaCl2∙Ca(OH)2·H2O) with a high compressive strength. Notably, the soluble PbSO4 in the MSWIFA was converted into relatively stable PbSiO3, and Cr(VI) was lattice-wrapped. This study was the first to demonstrate that tourmaline synchronously passivates Pb(II) and Cr(VI) in fly ash in the solid phase, with a low cost and requires no subsequent treatment. This study provided a novel technical path for recycling MSWIFA. Eventually, leaching of the heavy metals Pb, Cr, Cu, Cd, and Zn from the solids achieved concentrations less than 0.25, 1.5, 0.5, 0.15, and 100 mg/L.

Simultaneous Production and Immobilization of Lipase Using Pomegranate-Seed Residue: A New Biocatalyst for Hydrolysis Reactions and Structured Lipids Synthesis

Pomegranate-seed residue (PSR) was used in a new strategy for the simultaneous production of Yarrowia lipolytica lipase by submerged fermentation and its immobilization by adsorption. This biocatalyst—the fermented solid residue containing the adsorbed lipase (fermPSR)—was evaluated in hydrolysis reactions and in structured lipid synthesis. In shake flasks, yeast extract and urea were the best nitrogen sources for lipase production with PSR and their simultaneous use increased the lipase production even further. This result was confirmed in a 3.5-liter bioreactor, with lipase activity in an extracellular medium of 40 U/mL. A maximum reaction rate (Vmax) of 49.5 µmol/min/g, a Michaelis–Menten constant (Km) of 207 µmol/L, and a turnover number (Kcat) of 130 s−1 were determined for the new biocatalyst, fermPSR, for the hydrolysis of p-nitrophenyl laurate (p-NPL) into p-nitrophenol. The conversion of p-NPL into p-nitrophenol in subsequent reactions confirmed fermPSR’s potential for industrial hydrolytic reactions. The production of structured lipids from vegetable oil and free fatty acids by fermPSR evidences the versatility of this new biocatalyst.

Using ammonia solution to fabricate highly active Au/ uncalcined TS‑1 catalyst for gas-phase epoxidation of propylene

Reducing the Au particle size and increasing the number of defective Ti4+ species have been considered effective strategies to boost the catalytic performance of Au–Ti bifunctional catalysts used for propylene epoxidation utilizing H2 and O2. Consequently, the development of an effective method that can simultaneously achieve these goals is of significant scientific and industrial importance. Herein, we demonstrate, for the first time, that the simultaneous immobilization of small Au particles (approximately 1.6 nm) onto uncalcined titanium silicate-1 (i.e., TS-1-B) and facilitation of the formation of defective Ti4+ species can be achieved using a modified deposition–precipitation (DP) method utilizing ammonia solution as the precipitant. The as-synthesized catalyst exhibits a significantly enhanced propylene oxide (PO) formation rate combined with fascinating PO selectivity and hydrogen efficiency, which were better than the reference catalyst prepared via the DP urea (DPU) method and other reported Au/uncalcined TS-1 catalysts. The catalyst structure–performance relationship was established using multiple characterization studies. the ammonia treatment facilitates the hydrolysis of some of the ≡Ti-O-Si≡ bonds into defective Ti4+ species (i.e., Ti(OSi)3OH), which not only provides more active Ti4+ sites but also favors the uniform deposition of Au. This methodology and the insights stated herein may also be applicable for enhancing the dispersion of Au in a variety of zeolite-supported catalysts.

Porous hydrogel scaffolds integrating Prussian Blue nanoparticles: A versatile strategy for electrochemical (bio)sensing

Hydrogels have emerged as promising porous soft materials from which to develop a wide range of biosensing platforms due to the possibility to easily engineer their properties and to effectively immobilize enzymes and nanomaterials in their matrix. Despite their attractive properties, the ability to form stable hydrogel films integrating well–dispersed catalytic nanomaterials and enzymes on electrode surfaces is still required to enable their implementation into electrochemical biosensors. Here, we report a facile approach to prepare hydrogel films embedding Prussian Blue nanoparticles (PBNPs) and different enzymes on electrode surfaces for electrochemical biosensing. A one-pot strategy was employed for the synthesis, under mild conditions, of PBNPs and the simultaneous immobilization of enzymes in a highly functionalized carboxymethyl cellulose matrix, yielding homogeneous hydrogel composites. Highly porous hydrogel films were successfully prepared by drop casting the hydrogel composites on the surface of flexible screen–printed electrodes (SPEs). Due to the high loading of well–dispersed PBNPs, the hydrogel films demonstrated good electrocatalytic activity for both the oxidation of NADH and the reduction of hydrogen peroxide resulting in high detection sensitivity. Two amperometric biosensors for the rapid detection of glucose and ethanol in serum were realized by employing hydrogel composites integrating glucose oxidase and alcohol dehydrogenase. By combining the unique features of hydrogels on flexible electrochemical strips, our approach holds great promise for the development of portable electrochemical (bio)sensors, which are easy to fabricate and versatile for the detection of a variety of analytes.

Alkaline modification on schwertmannite promoted the simultaneous immobilization of arsenite and cadmium

Arsenic (As) and cadmium (Cd) co-contamination is of most concern in the environment. Schwertmannite (Sch), a poorly crystalline Fe(III) oxyhydroxy-sulfate mineral, is extremely efficient for As immobilization owing to its unique structure, but ineffective against cationic Cd (Cd(II)) due to the acidic pH after Sch addition. In this study, an alkaline modification method was proposed to improve the treatment efficiency of schwertmannite for As(III)-Cd(II) co-contamination. Results showed that alkali soaking had no obvious effect on mineral phase, and schwertmannite was the main mineral component. Alkali-modified Sch (Sch-OH) consisted of a large number of nanoparticles superimposed on each other, with specific surface area drastically increasing from 69.7 m2/g (Sch) to 261.9 m2/g. The sulfate content in Sch-OH structure decreased by 71.5%, which contributed to the reduction of maximum adsorption capacity for As(III) (from 116.09 to 81.06 mg/g at pH 6.5). The co-existing As(III) enhanced Cd(II) adsorption onto Sch-OH by forming ternary Fe-As-Cd complexes, corresponding to an increase in adsorbed amount from 8.8 to 11.3 mg/g (in 20 mg/L Cd(II) solution). Sch-OH exhibited a higher mineral stability than Sch under flooded condition at 40°C, and its retaining ability for As(III) was stronger. In a Cd-As polluted soil, the content of KH2PO4-extractable As decreased from 6.3 to 4.8 mg/kg after 10 days-incubation with 5% Sch-OH, and the immobilization efficiency of Cd reached 49.1%. It is necessary to explore more modification methods of schwertmannite to broaden its application in metal(loid)s remediation.

Coupling and environmental implications of in situ formed biogenic Fe–Mn minerals induced by indigenous bacteria and oxygen perturbations for As(III) immobilization in groundwater

Iron (Fe)–manganese (Mn) minerals formed in situ can be used for the natural remediation of the primary poor-quality groundwater with coexistence of arsenite [As(III)], Mn(II), and Fe(II) (PGAMF). However, the underlying mechanisms of immobilization and coupling of As, Mn, and Fe during in-situ formation of Fe–Mn minerals in PGAMF remains unclear. The simultaneous immobilization and coupling of arsenic (As), Mn, and Fe in PGAMF during in-situ formation of biogenic Fe–Mn minerals induced by O2 perturbations and indigenous bacteria (Comamonas sp. RM6) were investigated at the different molar ratios of Fe(II):Mn(II) (1:1, 2:1, and 3:1). Compared with systems without Fe(II) in the presence of Mn(II), the coexisted Fe(II) significantly enhanced Mn(II) bio-oxidation and mineral precipitation, resulting in As immobilization increased by 5, 7, and 7 times at initial Fe(II) concentration of 0.3, 0.6, and 0.9 mM, respectively. Moreover, the As(III) immobilization efficiencies in Mn(II) and Fe(II) mixed system at initial Fe(II) concentration of 0.3, 0.6, and 0.9 mM were 73%, 91%, and 92%, respectively, that were significantly higher than those of single Fe(II) system (30%, 59%, and 74%) and those of single Mn(II) system (12%), indicating that Fe(II) and Mn(II) oxidation synergically enhanced As(III) immobilization. This was mainly attributed to the formation and As adsorption capacity of biogenic Fe–Mn minerals (BFMM). The formed BFMM significantly facilitated simultaneous immobilization of Fe, Mn, and As in PGAMF by oxidation, adsorption, and precipitation/coprecipitation, a coupling of biological, physical, and chemical processes. Fe component was mainly responsible for As fixation, and Mn component dominated As(III) oxidation. Based on the results from this work, biostimulation and bioaugmentation techniques can be developed for in-situ purification and remediation of PGAMF. This work provides insights into the simultaneous immobilization of pollutants in PGAMF, as well as promising strategies for in-situ purification and remediation of PGAMF.

Facile synthesis of calcium peroxide modified mesoporous silica for enhanced uranium extraction from uranium tailings leachate

Herein, calcium peroxide modified mesoporous silica (CPMS) was successfully synthesized by a facile strategy and used for simultaneous adsorption and immobilization of U(VI) from uranium-containing wastewater. The batch uranium adsorption experiments reveal excellent adsorption performance of CPMS over a wide pH value. In comparison to calcium peroxide and mesoporous silica, the CPMS showed a great improvement in the removal capacity of uranium. As well, the pseudo-second-order model and Langmuir isotherm model provided a well description of adsorption kinetics and isotherm, respectively, which suggested the monolayer chemisorption governed the adsorption of CPMS for U(VI). In addition, the Langmuir isotherm model calculated the maximum adsorption capacity of CPMS for U(VI) up to 613.50 mg/g. Based on mechanistic studies of XPS, FT-IR, TEM and XRD, U(VI) is predominantly removed through synergistic adsorption of U(VI) by mesoporous silicon and immobilization of U(VI) by calcium peroxide as (UO2)O2•2 H2O (metastudtite). Furthermore, the efficient removal ability of CPMS for U(VI) in uranium tailings leachate was confirmed by column test, the U(VI) concentration of uranium tailings leachate can be reduced from 180.4 μg/L to 2.3 μg/L in 1895.2-bed volumes, which was well lower than the standard limit of WHO for U(VI) concentration in drinking water. This research provides a feasible approach and new idea for the efficient treatment of radioactive wastewater.

One-dimensional hierarchical ZnCo-NCNT/Mo2C nanostructure as a high-efficiency bifunctional catalyst for rechargeable Zn-air batteries

Herein, a catalyst precursor is prepared by depositing bimetallic zeolitic imidazolate frameworks (BMZIFs) on a polypyrrole (PPy)-coated MoO3 nanobelt (NB). Next, BMZIFs (ZIF-8/ZIF-67), PPy and MoO3 are calcined into Co nanoparticles (NPs) dotted/Zn, Co doped carbon, nitrogen doped carbon nanotube (NCNT) and Mo2C NPs at 800 °C, respectively, to produce a one-dimensional (1D) hierarchical nano-catalyst. The 1D nano-catalyst with porous surface, large specific area and abundant defects maximumly exposes the catalytic active sites. Furthermore, the entire encapsulation of Mo2C NPs by NCNTs effectively restrains their agglomeration during the pyrolysis, and volume change in electrochemical reaction. Moreover, the simultaneous immobilization of bimetallic ZIFs on PPy is more likely to form small-sized Zn/Co NPs on NCNT than single ZIF. Accordingly, the nano-catalyst exhibits a small ΔE value of 0.791 V and the Zn-air battery based on this catalyst achieves an excellent peak power density of 231.6 mW cm−2 at 5 mA cm−2, and a much higher energy round-trip efficiency than Pt/C + RuO2 in the long-term (400 h) cycling experiment. The excellent ORR/OER behaviors of the catalyst is mainly attributed to the synergy between CoN4-graphene and Mo2C, which is verified by both experimental and density function theory (DFT) calculation results.

Addition of water hyacinth and attapulgite during hydrothermal carbonization of sewage sludge: Migration behavior of heavy metals and fuel characteristics of hydrochar

The treatment of sewage sludge (SS) presents challenges in terms of the effective simultaneous immobilization of heavy metals (HMs). This study analyzed the heavy metal migration behavior and fuel characteristics of hydrochar generated by co-hydrothermal carbonization (co-HTC) of SS and water hyacinth (WH) under the addition of attapulgite. The results showed that the co-HTC treatment facilitated the conversion of Cu, Cr, and Ni from the bioavailable fraction to the relatively stable fraction, with little effect on Mn and Pb. At 20% attapulgite of co-HTC, not only did the total concentration of HMs decreased significantly but the bioavailability of all measured metals decreased, reducing the potential ecological risk of the hydrochars. Moreover, the fuel ratio of co-HTC hydrochars was found to be improved (0.03─0.29), and an increase in the higher heating values (3.16─12.44 MJ/kg) compared to hydrochar from SS. The results of TG, FTIR spectra, and kinetic analysis further indicate that co-HTC promotes the aromaticity of the hydrochars and improves the fuel grade. From the perspectives of HMs immobilization and clean fuel production, co-HTC with SS and WH and the addition of attapulgite is an effective SS treatment method.

Surfactant-assisted synthesis of colloidosomes for positional assembly of a bienzyme system

In this study, using sorbitan monooleate (Span-80), we developed a new strategy to achieve the positional assembly of a horse radish peroxidase/glucose oxidase bienzyme system within the zeolitic imidazolate framework-8 (ZIF-8)-based colloidosomes. Span-80 with self-adsorption property, was used as an auxiliary stabilizer to endow the enzyme-loaded ZIF-8 (enzyme@ZIF-8) with proper wettability in the formation of water–in–oil Pickering emulsion templates. Benefited from this, simultaneous immobilization of the bienzymes in the lumen and shell of the colloidosomes could be achieved. Meanwhile, Span-80 was found to act as a mediator to induce and control the overgrowth of the ZIF-8 crystallites on the enzyme@ZIF-8 layers, by which a “bricklaying” solidification protocol was established for the shell preparation. The resulting colloidosomes enabled the flexible positional change of the bienzymes, its shell exhibited the monolayer structure with increased compactness and homogenized micropores. Furthermore, the multi-enzyme cascade reaction was exemplified with the oxidization of o-phenylenediamine. An in-depth investigation showed that the assembly strategies of the bienzymes significantly affected their biocatalytic efficiency by influencing the utilization efficiency of the H2O2 intermediate between the step reactions. This study provides an insight towards a facile synthetic route for constructing multi-enzyme biocatalyst.

Microwave-enhanced simultaneous immobilization of lead and arsenic in a field soil using ferrous sulfate

Remediation of soil contaminated by mixed heavy metals and metalloids has been a major challenge in the global environmental field. To address this critical issue, we tested a new technology for simultaneous immobilization of lead (Pb) and arsenic (As) in a field contaminated soil using a microwave-assisted FeSO4·7H2O treatment process. The process was able to rapidly reduce the TCLP-based leachability of Pb from 12.74 to 0.1 mg L−1 and As from 2.704 to 0.002 mg L−1 (MW power = 800 W, Irradiation time = 20 min, and FeSO4·7H2O = 4 wt%). The effects of FeSO4·7H2O dosage, microwave power, and irradiation time were determined and optimized. After 365 days of curing under atmospheric conditions, the TCLP-leached concentration of Pb and As in the treated soil remained below the regulatory limits of 0.1 and 0.002 mg L−1, respectively. The microwave irradiation promoted the formation of insoluble PbSO4(s) and Fe3(AsO4)2·8H2O(s), resulting in the long-term stability of Pb and As in the soil. The technology offers an effective alternative for remediation of Pb- and/or As-contaminated soil and groundwater.

Green clinker-free binders: Simultaneous immobilization and carbonation of ferrous metallurgical residues activated by sulfur wastes

In this work, green clinker-free binders (GCFBs), an alternative cement, were fabricated by recycling sulfur wastes to activate ferrous metallurgical residues for immobilization of solid wastes and carbonation of carbon dioxide synchronously. The results of compressive strength revealed that GCFB-2 activated by thenardite has the highest strength (36.74 MPa) in 3–28 days, and the GCFB-3 activated by ardealite retains a positive growth rate, as well reaches the maximum strength (38.51 MPa) in 120 days. The mineral compositions of GCFBs hardened paste disclosed that ettringite, CSH gels, and portlandite are the main hydrates, which are the strength source of immobilized solid wastes. After the carbonation of carbon dioxide, the compressive strength declines, calcite was the main mineral product, and the net carbonation capacity of carbon dioxide is 2.86–4.75 g/Kg for GCFBs. GCFBs have offered the double benefits of CO2 emission reduction and waste management, and the hardened pastes are a well better alternative aggregate due to the extremely high compressive strength. This study could provide a new perspective on the full resource utilization of industrial solid wastes, while GCFBs are an excellent alternative to cement in the field of environmental immobilization, with outstanding carbon capture and storage capacity in terms of CO2 carbonation.

Insight into UV-LED/PS/Fe(Ⅲ) and UV-LED/PMS/Fe(Ⅲ) for p-arsanilic acid degradation and simultaneous arsenate immobilization

As a feed additive, p-arsanilic acid (p-ASA) is hardly metabolized in animal bodies and is excreted chemically unchanged via feces and urine, which can be transformed into more toxic inorganic arsenic species and other organic by-products upon degradation in the aquatic environment. In this study, UV-LED/persulfate (PS)/Fe(Ⅲ) and UV-LED/peroxymonosulfate (PMS)/Fe(Ⅲ) processes were developed to remove p-ASA and immobilize the formed inorganic arsenic via tuning solution pH. UV-LED/PMS/Fe(Ⅲ) (90.8%) presented the best performance for p-ASA degradation at pH 3.0, and the p-ASA degradation in these processes both followed the pseudo-first-order kinetics. The ∙OH played the major role in UV-LED/PS/Fe(Ⅲ) and UV-LED/PMS/Fe(Ⅲ) systems. Solution pH greatly affected the p-ASA degradation and the maximum removal can be achieved at pH 3.0 due to the presence of more Fe(OH)(H2O)52+. The dosages of Fe(III) and PMS (PS), SO42− and HCO3− significantly influenced the performance of p-ASA oxidation, while HA, Cl− and NO3− slightly affected the p-ASA degradation. According to quantum chemical calculation, radical addition on the C atom in the C-As bond of p-ASA was corroborated to be the dominant reaction pathway by SO4∙− and ∙OH. Additionally, the reactive sites and reasonable degradation pathways of p-ASA were proposed based on DFT calculation and HPLC/MS analysis. The release of inorganic arsenic in both processes can be effectively immobilized and the toxicity of the reaction solution dramatically reduced by adjusting solution pH to 6.0. UV-LED/PMS/Fe(Ⅲ) process was found to be more cost-effective than UV-LED/PS/Fe(Ⅲ) process at the low oxidant dosages.

Immobilization of Cs and Sr within perovskite-type Ba0.7-ySry(La, Cs)0.3ZrO3 glass/ceramic composite waste forms

The disposal of radioactive Cs and Sr in high-level radioactive waste is a problem that needs to be considered in the nuclear industry. Currently, it is difficult to immobilize Cs and Sr simultaneously into a durable host phase, especially at low temperatures to avoid volatilization of Cs. Thus, perovskite-type Ba0.7-ySry(La, Cs)0.3ZrO3 (y ≤ 0.6) polycrystalline was synthesized by sol-gel technique at low temperatures and developed as a host to immobilize Cs and Sr. The polycrystalline powders were further fixed in glass matrix to form the glass/ceramic composite waste forms. The results show that Cs and Sr can be immobilized effectively in the lattice positions of Ba0.7-ySry(La, Cs)0.3ZrO3 at a low temperature (900 °C), without volatilization of Cs during the immobilization process. The glass/ceramic composite waste forms with a crystalline-amorphous phase inlaid structure, prepared with glass content of 40 wt% and sintering temperature of 800 °C, have low porosity, good compactness, and high hardness. The leaching rates of Cs and Sr in the waste forms can reach the order of 10−3 - 10−4 g m−2 d−1 after 14 days. This result provides an ideal host of Ba0.7-ySry(La, Cs)0.3ZrO3 for simultaneous immobilization of Cs and Sr at low temperatures, and combines the advantages of traditional glass solidification and promising ceramic solidification.

Simultaneous reduction of available arsenic and cadmium in contaminated soil by iron-modified fly ash

ABSTRACT Arsenic (As) and cadmium (Cd) co-contamination in the soil is a serious global health concern. Three iron-modified fly ash (FA) composites were synthesised, including FA-supported nanoscale zero-valent iron (FA-nZVI), FA-supported FeCl3 (FA-FeCl3) and FA-supported Fe-oxyhydroxide sulphate (FA-FeOS) for remediation of As and Cd co-contaminated soil. Soil incubation experiments were conducted to evaluate the effects of iron-modified FA on the soil pH, availability and geochemical fractions of As and Cd. The results showed that FA and FA-nZVI significantly (P < 0.05) increased the soil pH, but FA-FeCl3 and FA-FeOS decreased the soil pH in general. FA, FA-nZVI, FA-FeCl3 and FA-FeOS decreased the concentration of available As by 15.13∼21.22%, 46.20∼46.66%, 30.02∼38.09% and 12.05∼30.50%, respectively. However, only FA and FA-nZVI decreased the concentration of available Cd by 4.85∼26.09% and 37.74∼52.18%, respectively. The results showed that FA-nZVI was the most effective amendment for simultaneous immobilisation of As and Cd. Besides, FA-nZVI stimulated the transformation of As and Cd from reactive states to less reachable states to decrease the toxicity of As and Cd in soil. In conclusion, FA-nZVI is a potential amendment for soil remediation in As and Cd co-contaminated soil.

Nanozyme–Cellulose Hydrogel Composites Enabling Cascade Catalysis for the Colorimetric Detection of Glucose

Catalytic cascades obtained from the combination of nanozymes, which are nanomaterials with enzyme-like activity, and natural enzymes have drawn much attention for biosensing and biomedical applications. A key consideration in the development of cascade reaction systems is the integration of nanozymes with enzymes to boost the overall catalytic performance. Here, we report an efficient one-pot approach for the preparation of an enzyme–nanozyme hydrogel composite for cascade catalysis. Prussian blue (PB) nanoparticles (NPs) were prepared by using mild synthetic conditions in a cellulose-based hydrogel network in the presence of glucose oxidase (GOx), resulting in the simultaneous immobilization of PB NPs and active GOx in the hydrogel. This integrated system not only displays peroxidase-like activity relative to the PB NPs but also reveals an enhanced cascade catalytic performance for the colorimetric detection of glucose due to the proximity effect of the enzyme–nanozyme system within the hydrogel matrix. Compared to the analogue mixture with GOx in solution, the composite hydrogel shows enhanced glucose detection and improved stability. The developed colorimetric assay was successfully applied for the analysis of glucose in human serum samples, demonstrating its potential in clinical diagnosis. The versatility of this one-pot protocol holds promise for the development of different multienzyme systems, leading to efficient cascade catalysis for sensing applications.