Depleting aquifers, lack of planning and low socioeconomic status of Pakistani farmers have led them to use wastewater (WW) for irrigating their crops causing food contamination with heavy metals and ...ultimately negative effects on human health. This study evaluates the effects of chitosan (CH) and biochar (BC) on growth and nutritional quality of brinjal plant together with in situ immobilization of heavy metals in a soil polluted with heavy metals due to irrigation with wastewater (SPHIW) and further irrigated with the same WW. Both CH and BC were applied at three different rates i.e. low rate (LR), BC0.5%, CH0.5% and BC0.25%+CH0.25%, medium rate (MR), BC1%, CH1% and BC0.5%+CH0.5% and high rate (HR), BC1.5%, CH1.5% and BC0.75%+CH0.75%. Result revealed that brinjal growth, antioxidant enzymes, and fruit nutritional quality significantly improved from LR to HR for each amendment, relative to control. However, these results were more prominent with BC alone and BC+CH, compared with CH alone at each rate. Similarly, with few exceptions, significant reduction in Ni, Cd, Co, Cr and Pb concentrations in the root, shoot and fruit were found in sole CH treatment both at LR and MR but in both CH and BC+CH treatments at HR, relative to control. Interestingly, the concentrations of Fe in the roots, shoots and fruit were more pronounced at BC treatments relative to CH and BC+CH treatments at each rate, compared to control. Overall, the BC+CH treatment at HR was the most effective treatment for in situ immobilization of heavy metals in SPHIW and further irrigated with the same WW, compared to rest of the treatments. This study indicates that BC0.75%+CH0.75% treatment can be used to reduce mobility and bioavailability of heavy metals in SPHIW and facilitates plant growth by improving the antioxidant system. However, the feasibility of BC0.75%+CH0.75% treatment should also be tested at the field scale.
•Increasing biochar and biochar + chitosan doses improved brinjal growth and quality.•The concentrations of heavy metals in plant were reduced by increasing chitosan dose.•Higher concentrations of Fe in the plant were found with biochar than chitosan.•Biochar + chitosan at a higher rate can remediate soil polluted with wastewater.
Biocatalysis has widened its scope and relevance since new molecular tools, including improved expression systems for proteins, protein and metabolic engineering, and rational techniques for ...immobilization, have become available. However, applications are still sometimes hampered by low productivity and difficulties in scaling up. A practical and reasonable step to improve the performances of biocatalysts (including both enzymes and whole-cell systems) is to use them in flow reactors. This review describes the state of the art on the design and use of biocatalysis in flow reactors. The encouraging successes of this enabling technology are critically discussed, highlighting new opportunities, problems to be solved and technological advances.
Biocatalyzed reactions with different classes of enzymes can be implemented with the integration of flow reactor technology, potentially leading to sustainable and highly productive continuous processes.
The combination of biocatalysis and flow chemistry opens the door to extensive application in cascade reactions.
Biocatalyzed flow reactions can occur either in monophasic flow or in segmented (slug) flow, where two or more immiscible phases are present.
Limitation of substrate/product inhibition effects, in-line purification with easy recovery of the product, and no mechanical mixing are among the most distinctive advantages of flow-based biocatalysis.
Automated machines and devices for in-line product recovery are now available at relatively low prices, making flow-based biocatalysis an easy-to-use technology.
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•Synergy of MgO cement and Si-rich minerals generated magnesium silicate hydrate (M-S-H).•Characteristics of Si-rich minerals determined the formation and polymerisation of M-S-H ...gel.•M-S-H gel enhanced the mechanical strength and water resistance of MgO-based products.•M-S-H gel had an excellent sequestration of toxic elements for stabilisation/solidification.
Disposal of significant amounts of dredged contaminated sediment poses an economic and environmental problem worldwide. Transforming contaminated sediment into value-added construction materials using low-carbon MgO cement is a sustainable option; however, the weak mechanical strength and unreliable water-solubility of MgO cement restrict its practical engineering applications. This study elucidates the potential role of industrial Si-rich minerals in the performance enhancement of MgO-based products via the promotion of magnesium silicate hydrate (M-S-H) gel formation. Quantitative X-ray diffraction and 29Si nuclear magnetic resonance analyses indicated that compositions and crystallinities of the Si-rich minerals significantly influence the formation and polymerisation of the M-S-H gel. Pulverised fly ash was found to be a promising Si-rich mineral for generating polymeric M-S-H gel, whereas incinerated sewage sludge ash samples demonstrated a low degree of polymerisation, and the use of glass powder samples gave a low yield of M-S-H. The formation of M-S-H gel enhanced the compressive strength and water resistance (strength retention after water immersion). Further experiments demonstrated that Si-modified MgO cement can transform dredged sediment into fill materials with satisfactory mechanical properties and contaminant immobilisation. Therefore, the synergy between reactive MgO and Si-rich industrial waste is a novel option for sustainable remediation and environmental applications.
In this study, carrageenase immobilization was evaluated with a concise and efficient strategy. Pomelo peel cellulose (PPC) modified by polyethyleneimine (PEI) using the physical absorption method ...was used as a carrier to immobilize carrageenase and achieved repeated batch catalysis. In addition, various immobilization and reaction parameters were scrutinized to enhance the immobilization efficiency. Under the optimized conditions, the enzyme activity recovery rate was more than 50% and 4.1 times higher than immobilization with non-modified pomelo peels. The optimum temperature and pH of carrageenase after immobilization by PEI-modified pomelo peel, at 60°C and 7.5 respectively, were in line with the free enzyme. The temperature resistance was reduced, inconsistent with free enzyme, and pH resistance was increased. A significant loss of activity (46.8%) was observed after reusing it thrice under optimal reaction conditions. In terms of stability, the immobilized enzyme conserved 76.0% of the initial enzyme activity after 98 days of storage. Furthermore, a modest decrease in the kinetic constant (K m ) value was observed, indicating the improved substrate affinity of the immobilized enzyme. Therefore, modified pomelo peel is a verified and promising enzyme immobilization system for the synthesis of inorganic solvents.
Direct knitting of nucleophilic arene monomers in the presence of electrophilic cross‐linker, like formaldehyde dimethyl acetal, is proven to be a cost‐effective and versatile method for the ...synthesis of porous organic polymers. The resulting hypercrosslinked polymers (HCPs) are featured by hierarchical porous structure, high surface area, and pore volume. Coordinating functional groups can be easily installed with this method into the rigid aryl network. Direct knitting to HCPs has therefore been widely used in preparing heterogeneous solid catalysts. Wise selection of monomers with rational design of 3D structure and the synergy between the HCP support and the catalytically active species often lead to high efficiency of tailor‐made catalysts without sophisticated operations. On account of all these excellent properties, enthusiasm of researchers to use HCPs in catalysis is increasing rapidly. This review documents the necessity, feasibility, and the great contributions of using HCPs as invaluable tools for catalysis research, and summarizes state of the art of this chemistry. Similar type catalysts obtained by one‐step Scholl reaction are also included in this review.
Heterogeneous catalysts can be prepared via a one‐step knitting method using simple arene monomer and cross‐linker, which enable the formation of rigid porous hypercrosslinked polymers through Friedel–Crafts alkylation. This review summarizes state of the art of this straightforward route for the preparation of heterogeneous catalysts.
The Cover Feature shows a photoreforming process that cleans up waste (plastic, biomass, food, mixed) to provide a cleaner, hydrogen‐powered world. This process operates in flow and uses only ...sunlight and a photocatalyst panel to continuously generate hydrogen fuel from waste and water. More information can be found in the Full Paper by T. Uekert et al.
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•Aspartic acid functionalized graphene oxide (GO-Asp) was prepared.•l-Asparaginase was immobilized on GO-Asp either physically or covalently.•100% immobilization efficiency was ...achieved through chemical conjugation.•The covalently immobilized l-asparaginase showed an enhanced thermal and pH stability.•The covalently immobilized l-asparaginase on GO-Asp showed an acceptable reusability.
There is an increasing interest in using l-asparaginase in medical fields and food processing industries. Enzyme immobilization is an attractive field to improve l-asparaginase activity and stability. Graphene oxide (GO) is a promising candidate for enzyme immobilization due to its large specific surface area. In this study, GO was first functionalized with l-aspartic acid (GO-Asp), and then l-asparaginase was immobilized on the GO-Asp either physically or through chemical conjugation. A significant enzyme loading was achieved through covalent immobilization (100% immobilization efficiency). Stability of free and the immobilized l-asparaginase was examined at various temperatures (20–60 °C) and pH (5–9). The covalently immobilized l-asparaginase showed higher enzyme activity than free enzyme at pH 8 with the maximum recovered activity of 100%, 90.5% and 40.6% after 24 h of incubation at 20 °C, 40 °C and 60 °C, respectively. In addition, the covalently immobilized l-asparaginase on GO-Asp showed 42% recovered activity after eight continuous reaction cycles at 60 °C. The kinetic parameters of the immobilized and free enzyme were also calculated, indicating no significant changes in the enzyme affinity through covalent conjugation. The results clearly reflect the suitability of GO-Asp as a nanosheet support for l-asparaginase loading as well as its usage in future industrial applications.
•Geopolymers formed by alkali-activation of metakaolin can host Sr2+ and Ca2+.•The main reaction product identified is a fully polymerised Al-rich (N,K)-A-S-H gel.•Faujasite-Na & partially ...Sr-substituted zeolite Na-A form within gels cured at 80 °C.•Sr2+ or Ca2+ incorporation displaces some alkalis from gel charge-balancing sites.•Ca2+ and Sr2+ induce essentially the same structural changes in the gels.
Radioactive waste streams containing 90Sr, from nuclear power generation and environmental cleanup operations, are often immobilised in cements to limit radionuclide leaching. Due to poor compatibility of certain wastes with Portland cement, alternatives such as alkali aluminosilicate ‘geopolymers’ are being investigated. Here, we show that the disordered geopolymers ((N,K)-A-S-H gels) formed by alkali-activation of metakaolin can readily accommodate the alkaline earth cations Sr2+ and Ca2+ into their aluminosilicate framework structure. The main reaction product identified in gels cured at both 20 °C and 80 °C is a fully polymerised Al-rich (N,K)-A-S-H gel comprising Al and Si in tetrahedral coordination, with Si in Q4(4Al) and Q4(3Al) sites, and Na+ and K+ balancing the negative charge resulting from Al3+ in tetrahedral coordination. Faujasite-Na and partially Sr-substituted zeolite Na-A form within the gels cured at 80 °C. Incorporation of Sr2+ or Ca2+ displaces some Na+ and K+ from the charge-balancing sites, with a slight decrease in the Si/Al ratio of the (N,K)-A-S-H gel. Ca2+ and Sr2+ induce essentially the same structural changes in the gels. This is important for understanding the mechanism of incorporation of Sr2+ and Ca2+ in geopolymer cements, and suggests that geopolymer gels are excellent candidates for immobilisation of radioactive waste containing 90Sr.
Zirconolite wasteforms were designed for the co-immobilisation of CeO2 (as a PuO2 surrogate) and metallic iron, chromium, and aluminum, simulating contaminated FeCrAl alloy cladding. Zirconolite ...ceramics with the target composition Ca(1-3.87x)Ce3.87xZrTi(2-7.73x)Fe5.73xCrxAlxO7 (x = 0–0.11), were synthesised via solid state reaction sintering at 1400 °C. Phase and microstructural evolution were investigated to ensure the oxidation of the metals, formation of zirconolite phase and densification of the final ceramics. It was found that both oxidation and solid-state reaction could be accomplished by processing at 900 °C and 1400 °C under ambient atmosphere, accompanied by the overall yield of zirconolite in the range 92.4–94.0 wt % between x = 0.01–0.07 f.u., with a dense microstructure observed. Polytype transitions from zirconolite-2M to -3T were evidenced, where the solubility limit was reached at substitution level of x = 0.11 and precipitation of CeO2 was apparent. XPS analysis confirmed that an elevation in dopant concentration resulted in the partial reduction of Ce4+ to Ce3+, whereas Fe, Cr and Al metals were oxidised to the trivalent state. This study demonstrated the feasibility for designing advanced ceramic wasteforms for the co-immobilisation of actinides and metallic cladding residues.
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•Ti3+-doped brookite-type TiO2 crystal (Ti3+-TiO2) was prepared by NaBH4 thermal reduction method;•Immobilised Ti3+-TiO2/C was prepared by the thermal carbonisation treatment;•The ...performance of Ti3+-TiO2/C photocatalytic N2/H2O to ammonia was investigated;•The addition of carbon carrier greatly improved the efficiency of Ti3+-TiO2 photocatalysis for N2/H2O synthesis of ammonia.
In this work, a Ti3+-doped brookite-type TiO2 crystal (Ti3+–TiO2) was prepared using a NaBH4 thermal reduction method. A composite photocatalyst Ti3+–TiO2/C was obtained on a glass plate by heat treatment to remove organic substances. The structure of the as-prepared photocatalyst was characterised, and the immobilisation conditions were optimised. Furthermore, photocatalytic ammonia synthesis from N2/H2O was investigated. The results show that the introduction of the carbon carrier not only can enhance the ability of Ti3+–TiO2/C to transport photogenerated electrons but also can prevent the recombination of photogenerated electrons and holes through the transfer of electrons by the carbon substrate. Meanwhile, the oxygen-containing groups linked to the carbon carrier can improve the N2 adsorption and activation ability of the photocatalyst, which improved the photocatalytic ammonia synthesis activity of Ti3+–TiO2/C. The ammonia yield on the Ti3+–TiO2/C composite photocatalyst reached 0.313 µmol/(L·cm2) after 4 h of photocatalytic ammonia synthesis reaction from N2/H2O, which is 2.51 times higher than that on pure Ti3+–TiO2 under the same conditions. In addition, in this work, we used immobilised Ti3+–TiO2/C as a photocatalyst, which simplifies the method of recycling the catalyst and provides an idea for the industrialisation of the photocatalytic reaction.
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