Reactive kinetics coupled with population balance model (PBM) and computational fluid dynamics (CFD) was implemented to simulate silver nanoparticles (AgNPs) formation in a microtubular reactor. The quadrature method of moments, multiphase model theory, and kinetic theory of granular flow were employed to solve the model, and the particle size distributions (PSD) were calculated. The simulation results were validated by synthesizing AgNPs experimentally in an actual microtubular reactor for comparison with the PSD. The results confirmed the effectiveness of the model and its applicability in predicting AgNPs formation and its PSD evolution in the microtubular system. Finally, benefiting from its superiority, in that the influence of reactive kinetics and fluid dynamics on particle evolution could be considered separately, the model was employed to verify predictions and inferred conclusions in our previous works, which were difficult to verify through experiment.

•Plant-mediated synthesis of porous Pd-Pt alloy NFs with dominant (111) planes.•The biogenic Pd-Pt NFs were used directly in ethanol oxidation without special treatment.•The PdPt3 NFs is 4.1, and 9.1 more active than commercial Pd and Pt–black toward ethanol oxidation.•Electrocatalytic activity increased with Pt content, and stability with Pd additionBimetallic Pd-Pt nanoflowers (Pd-Pt NFs) of varying sizes (20–60 nm) were synthesized through the concurrent reduction of Pd(NO3)2 and K2PtCl4 using Cinnamomum camphora (C. camphora) leaf extract assisted by ascorbic acid (AA). C.Camphora acted as both a co-reducing agent and a green template in the synthesis protocol providing a fast, simple, green and cost-effective means of producing the Pd-Pt NFs. Characterization techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to confirm the Pd-Pt NFs formation. FT-IR analysis showed that biomolecules such as polyphenols and flavonoids were responsible for the reduction while stretching vibration bands from CH, CC, OH, and CO O acted as capping agents. The as-formed Pd-Pt NFs showed excellent performance and stability in the electro-oxidation of ethanol in alkaline media. Electro-catalytic performance increased with Pt content, while addition of Pd increased stability. The PdPt3 NFs presented the best performance with a mass activity of 1.43 A mg−1metal, 5.72, 4.93, 2.27, 1.27, 11 and 4.6% higher than the Pd, Pt, Pd3Pt, and PdPt NFs, and commercial Pt and Pd-black respectively. However, it was more prone to poisoning, with an If/Ir value of 0.78 compared to 1.37 for Pd3Pt NFs.

AbstractThe biosynthesized gold/activated carbon catalysts for glucose oxidation were prepared with Cacumen platycladi leaves extract, and activated carbon (AC) was modified with hydrochloric acid and nitric acid to modify its surface chemistry and used as supports. The catalysts with acid-treated AC exhibited improving activity for the selective oxidation of glucose, when compared to that with untreated one. In order to investigate the influence of the acid treatment for the catalysts performance, the surface chemical properties of AC were characterized by Brunauer- Emmett-Teller surface area characterization, Boehm titration, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, respectively. The dispersion of AuNPs on AC was observed by transmission electron microscopy and X-ray diffraction. The results indicated that the catalysts with acid treated supports showed improved dispersion than that of untreated one, which may be the result that the supports significantly increase the surface functional groups and remove the ash after acid treatment.

•The dewatering of digestate performance was effectively improved by conditioning jointly with CTAB and coal fly ash.•The relationship between dewaterability of digestates and the extracellular polymeric substances, particle size, and surface charge was obtained.•The mechanism of the in-depth digestate dewatering was inferred and the factors were determined to be critical.In this study, the effects and mechanism of pretreating digestates with cetyltrimethylammonium bromide (CTAB) and coal fly ash (CFA) were investigated. The water content (WC) and specific resistance of filtration (SRF) of the digestates were measured to evaluate the digestate dewaterability. The protein (PN) content, polysaccharide (PS) content, zeta potential and particle size of the digestates were measured to probe the mechanism of pretreatment. The results indicated that the digestate dewatering performance was effectively improved by joint conditioning with CTAB and CFA. For straw digestate (St-digestate), pig manure digestate (PM-digestate), cow dung digestate (CD-digestate) and kitchen waste digestate (KW-digestate), the optimum dosage of CTAB was 50%, 30%, 20% and 50% dry solid (DS) of digestate, respectively, and the optimum dosage of CFA was 100% DS of digestate. Co-conditioning with CTAB and CFA resulted in clear advantages compared to CTAB or CFA conditioning alone for decreasing the WC of digestates. The proposed mechanism is the synergistic effect of CTAB and CFA. CTAB releases extracellular polymeric substances (EPS) and neutralizes charge, and CFA acts as a skeleton builder in the dewatering process to enhance dewaterability. Finally, a green degree method for the environmental assessment of chemical processes was adopted to evaluate digestate dewatering.

In this study, artificial-neural-network- (ANN-) based models were explored and validated to predict the fates of carbon (C) and nitrogen (N) under 84 types of digesters in treating different blends of seven substrates (corn straw, rice straw, wheat straw, swine manure with fed feedstuff and foodstuff, cattle manure, and chicken manure) under changing volatile solids (VS) loadings. ANN models based on principal component analysis (PC-ANN) were developed for estimating the fate of C (CH4 yields and COD concentrations in the supernatant), showing higher prediction accuracies than the original ANN models. The fate of N (NH4+-N concentrations in the supernatant) was well predicted by the ANN model with two inputs, namely, total Kjeldahl nitrogen (TKN) and total ammonium nitrogen (TAN) in the substrates. The models were also developed for wide applications to validate the CH4 yields and NH4+-N concentrations for new databases outside the established data range obtained from the literature, with regression coefficient (R2) values of 0.705 and 0.791, respectively. This study can provide guidance for future process optimization and nutrient recycling in anaerobic digestion (AD).

This critical review focuses on recent advances in the bio-inspired synthesis of metal nanomaterials (MNMs) using microorganisms, viruses, plants, proteins and DNA molecules as well as their applications in various fields. Prospects in the design of bio-inspired MNMs for novel applications are also discussed.

•Green synthesis of gold nanoparticles by the extract of Cacumen Platycladi leaf.•Shape separation of nanoparticles was achieved.•The mechanism for shape separation of gold nanoplates by agarose gel electrophoresis was discussed.A mixture of nanospheres and nanoplates was synthesized through bioreduction of HAuCl4 with Cacumen Platycladi leaf extract. In this work, shape separation of the nanospheres and nanoplates was achieved via agarose gel electrophoresis (AGE). Furthermore, the separation mechanism and the effects of parameters, including the agarose gel concentration, electrophoresis voltage and TBE buffer concentration, on the separation performance were investigated. The optimum conditions were found to be 1.2% gel concentration, 100 V voltage, and 1 × TBE buffer solution. Gold nanoparticles (NPs) prepared via a biological method were compared with those synthesized using a chemical method in the electrophoresis process with different characteristics. The results showed that the particles prepared via the biological method had good stability in a buffered solution without further modification.

Herein, we reported the green synthesis of Ag–Pd alloy nanoparticles (NPs) using the aqueous extract of the Cacumen platycladi leaves as well as their application as catalyst for hydrogenation of 1,3-butadiene. The biosynthetic NPs were characterized to confirm the nature of alloy by UV–vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The possible functional groups responsible for the reduction and protection of NPs were identified through Fourier transform infrared spectroscopy (FTIR). The results revealed that biomolecules like saccharides, polyphenols, or carbonyl compounds were related to the reduction process, and the (NH)C═O groups were responsible for the stabilization of the NPs. Furthermore, the as-formed Ag–Pd bimetallic-supported catalysts especially Ag1Pd3/γ-Al2O3 was found to possess excellent catalytic performance toward hydrogenation of 1,3-butadiene. A butene yield of 84.9% was obtained, which was remarkably enhanced when compared with monometallic counterparts. Moreover, the activity of it maintained stability within 12 h of durable experiments.Keywords: Ag−Pd Nanoparticles; Alloy; Biosynthesis; Cacumen platycladi

Microcosm experiments were conducted to investigate the mechanism of microbial-mediated As mobilization from high arsenic tailing sediments amended with nanoparticles (NPs). The addition of SiO2 NPs could substantially stimulate arsenic mobilization in the sodium acetate amendment sediments. However, the addition of Fe2O3 and Fe3O4 NPs restrained arsenic release because these NPs resulted in Fe–As coprecipiate. Moreover, NP additions in sediments amended with sodium acetate as the electron donor clearly promoted microbial dissimilatory iron reduction. Nearly 4 times the Fe(II) (11.67–12.87 mg·L–1) from sediments amended with NPs and sodium acetate was released compared to sediments amended with only sodium acetate (3.49 mg·L–1). Based on molecular fingerprinting and sequencing analyses, the NP additions could potentially change the sediment bacterial community composition and increase the abundance of Fe(III) and As(V) reduction bacteria. Several potential NP-stimulated bacteria were related to Geobacter, Anaeromyxobacter, Clostridium, and Alicyclobacillus. The findings offer a relatively comprehensive assessment of NP (e.g., Fe2O3, Fe3O4, and SiO2) effects on sediment bacterial communities and As mobilization.

•The adsorption rate of Pd (II) by P. pastoris increased after proper pretreatment.•The Pd NP/P. pastoris catalysts after pretreatment showed enhanced stability.•Slow reduction in Pd (II) with P. pastoris was essential for enhanced stability.Based on rapid adsorption and incomplete reduction in Pd (II) ions by yeast, Pichia pastoris (P. pastoris) GS115, the effects of pretreatment on adsorption and reduction of Pd (II) ions and the catalytic properties of Pd NP/P. pastoris catalysts were studied. Interestingly, the results showed that the adsorption ability of the cells for Pd (II) ions was greatly enhanced after they were pretreated with aqueous HCl, aqueous NaOH and methylation of amino group. For the reduction in the adsorbed Pd (II) ions, more slow reduction rates by pretreated P. pastoris cells were displayed compared with the cells without pretreatment. Using the reduction of 4-nitrophenol as a model reaction, the Pd NP/P. pastoris catalysts based on the cells after pretreatment with aqueous HCl, aqueous NaOH and methylation of amino group exhibited higher stability than the unpretreated cells. The enhanced stability of the Pd catalysts can be attributed to smaller Pd NPs, better dispersion of the Pd NPs, and stronger binding forces of the pretreated P. pastoris for preparing the Pd NPs. This work exemplifies enhancing the stability of Pd catalysts through pretreatments.

•Alkaline sodium phosphate buffer was used to extract phenolic compounds.•Phenolic-rich precipitate formed during the acidification of the extracts.•Proteins and carbohydrates contented in the precipitates were determined.•The simple preparation process indicated prospective industrial potential.The alkaline extraction and acid precipitation of longan seed phenolic compounds were investigated to develop a more practical process than currently exists to isolate these chemicals. By using an alkaline buffer as the extraction solvent, the yield of total phenols reached 46.86±0.43 mg/g after conventional solid–liquid extraction. Because of the benefit achieved from the preconcentration process, an acid precipitation efficiency of 65.29 ± 0.38% was obtained, and the separation yield of phenols reached 22.04 ± 1.95 mg/g. However, the purity of the phenolic extract was influenced by the presence in the precipitate of proteins and carbohydrates, which both moved together in all four precipitation fractions at different pH values. The FRAP assay and the assay of the radical-scavenging activity revealed the strong antioxidant activity possessed by the phenolic compounds in the precipitate extracts. This preparation process for phenolic compounds has obvious advantages, such as easy operation, safe products and low production cost, which indicated its prospective industrial potential.

A series of Au/TiO2 catalysts for CO oxidation with same Au loading but different Au nanoparticles (NPs) sizes were prepared by varying the calcination temperatures and biomass concentration via a biosynthetic approach. The resulting catalysts were characterized by DRUV–vis, TEM, and TG techniques. The experimental results showed that the activity of the gold catalysts for CO oxidation was very sensitive to the particle size. Among the tested catalysts, the one with mean size of 3.8 nm was the most active. As determined by TEM, the contact boundary between the Au NPs and the TiO2 support was related to the size of the Au NPs. For the most active catalyst, hemispherical Au NPs (3.8 ± 0.6 nm) had the best contact boundary with the TiO2 support, yielding the longest perimeter interface, suggesting that the contact boundary was the most critical factor for the CO oxidation. The in-situ FTIR study of CO adsorption on the catalysts showed that CO was not adsorbed on the Au surface. This might be due to the modification of the Au/TiO2 catalysts by the residual biomass. The intensity of the peak at 2185 cm–1 for the Au/TiO2 catalysts with the longest perimeter interface was highest, demonstrating that the Au–TiO2 contact boundary played an important role in the adsorption of CO.

The synthesis and applications of anisotropic nanostructures have attracted much attention in modern nanotechnology. Recently, biosynthesis has been demonstrated to be a viable green alternative to traditional chemical and physical methods for synthesizing metal nanostructures. Herein, we developed a new, green one-pot synthetic protocol in which silver nanoflowers (Ag NFs) with three-dimensional structures were synthesized by Canarium album foliar broths in the presence of trisodium citrate (TSC) at room temperature. The effects of silver nitrate, TSC, and foliar broths on these synthesis processes were investigated to determine the optimum synthesis conditions. Further exploration of the formation mechanism of Ag NFs showed that both the biomolecules and TSC played very important roles. The improved insight into the specific roles of the bioprotective components and the controlled synthesizing ability are expected to help explain the formation mechanism of this interesting nanostructure that exhibited an excellent performance in surface-enhanced Raman scattering.

Size- and shape-based separation is an effective complementary process to prepare well-defined materials for fundamental studies and applications. However, the separation of nanoparticles polydisperse in both shape and size remains a great challenge. A mixture of gold nanospheres and nanoplates with a wide standard deviation (SD) (21% for the former and 30% for the latter) were synthesized in the same batch using sun-dried Cacumen Platycladi leaf extract. Size-separation of Au nanoparticles was achieved via density gradient centrifugation and the subsequent shape separation was achieved via agarose gel electrophoresis. Transmission electron microscopy (TEM) revealed that, monodispersed nanospheres (SD: 4–5%) and nanoplates (SD: 6–7%) were obtained separately after the two-step separation below.Graphical abstractHighlights► Green synthesis of gold nanoparticles by the extract of Cacumen Platycladi leaf. ► Size separation of nanoparticles was achieved by density-gradients centrifugation. ► Shape separation of nanoparticles was achieved by agrose gel electrophoresis. ► Monodisperse nanoparticles with uniform morphology were obtained via separation.

An effective electrochemical approach for simultaneous silver recovery and cyanide removal from electroplating wastewater was presented. Accordingly, pulse current (PC) electrolysis with parameters including voltage (4.0 V), frequency (800 Hz), and duty cycle (50%) were settled using static cylinder electrodes. Then the influences of technological conditions on the electroplating wastewater treatment process were investigated, which manifested that the concentration of silver ions in electroplating wastewater could be reduced from 221 to 0.4 mg L–1 and cyanide could be simultaneously removed from 157 to 4.9 mg L–1 after 3.0 h of PC electrolysis at pH 9.5 ± 0.5, aeration rate of 100 L h–1, and stirring speed of 1000 rpm with NaCl addition of 0.05 mol L–1 at room temperature. The results of XRD and EDX analysis showed that the silver deposits on the cathode were crystalline in face centered cubic structure and had a high purity.

Here, biosynthesis of silver nanoparticles (AgNPs) in a continuous stirred tank with C. Platycladi extract serving as both reducing and capping agents was investigated, which for the first time provided a successful green protocol for synthesis of AgNPs in a continuous stirred tank. Residence time distributions (RTDs) of the tank for both liquid and the AgNPs were measured experimentally to evaluate the performance of the tank. In addition, the flow behaviors in the tank varied with rotor speed and the performance of the RTD at sufficient rotor speed (360 rpm) was simulated then analyzed using the computational fluid dynamics (CFD) tool. The results showed that the mean and variance of the RTD deviate from the ideal values at low rotor speed, indicating that the rotor speed is a crucial factor for the continuous stirred tank. In addition, the liquid RTD was very close to the granular RTD, and the predicted RTD by CFD was similar to that measured experimentally. Finally, AgNPs with different size distributions were successfully synthesized in the tank by regulating technical parameters such as feeding flow rates of the reaction solutions, the concentration of C. Platycladi extract, and reaction temperature. The present work is anticipated to play an important role toward continuous production and industrialization of AgNPs using biosynthetic technique.

The effects of different biomolecules in Artocarpus heterophyllus Lam leaf extract on the morphology of obtained gold nanoparticles were investigated in this study. The results indicated that reducing sugars, flavones, and polyphenols consisting of about 79.8 % dry weight of the leaf extract were mainly involved in providing the dual function of reduction and the size/shape control during the biosynthesis. The gold nanoparticles present included 64 ± 10 nm nanospheres, 131 ± 18 nm nanoflowers, and 347 ± 136 nm (edge length) nanoplates and they were synthesized using the main content of reducing sugars, flavones, and polyphenols, respectively, after they were desorbed by the AB-8 macroporous adsorption resin column. Particularly, flower-like and triangular/hexagonal gold nanoparticles with a yield more than 80 % were obtained. Possible shape-directed agents for the nucleation and growth were characterized by FTIR, it can be seen that ketones were bound on the surface of the spherical and flower-like GNPs, while both the ketones and carbonyls bound on the Au {111} plane this may have favored the formation of the twin defects, which are very essential for nanoplates’ formation.

The photocatalytic activity for H2 evolution from pure water over Pd loaded TiO2 prepared by gardenia extract (Pd-Gardenia-TiO2) is systematically investigated. The as-prepared photocatalysts are characterized by X-ray diffraction, high resolution transmission electron microscopy, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. Gardenia extract functions as reducing and stabilizing agents simultaneously. The mean size of the as-prepared Pd nanoparticles is in the range of 2.3 ± 0.5 nm based on TEM images. The Pd-Gardenia-TiO2 catalyst exhibits good photocatalytic activity for H2 evolution (93 μmol · h−1 · g−1), which is much higher than that of Pd photodeposited on TiO2. Possible factors for its photocatalytic activity from pure water are also investigated.Highlights► Photoactivity for H2 evolution from pure water over Pd-Gardenia-TiO2 is studied. ► The mean size of the as-prepared Pd nanoparticles is 2.3 ± 0.5 nm. ► The introduction of gardenia extract is beneficial to enhance the photoactivity. ► Pd-Gardenia-TiO2 shows much higher photoactivity than Pd photodeposited on TiO2.

Biosynthesis of Ag nanoparticles (AgNPs) by Cacumen Platycladi extract was investigated. The AgNPs were characterized by ultraviolet–visible absorption spectroscopy (UV–vis), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and X-ray diffraction (XRD). The results showed that increasing the initial AgNO3 concentration at 30 or 60 °C increased the mean size and widened the size distribution of the AgNPs leading to red shift and broadening of the Surface Plasmon Resonance absorption. The conversion of silver ions was determined by atomic absorption spectroscopy (AAS) and to discuss the bioreductive mechanism, the reducing sugar, flavonoid, saccharide, protein contents in the extract, and the antioxidant activity were measured using 3,5-dinitrosalicylic acid colorimetric; Coomassie brilliant blue; phenol-sulfuric acid; rutin-based spectrophotometry method; and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay methods. The results showed that the reducing sugars and flavonoids were mainly responsible for the bioreduction of the silver ions and their reductive capability promoted at 90 °C, leading to the formation of AgNPs (18.4 ± 4.6 nm) with narrow size distribution. Finally, the antibacterial activity of the AgNPs against E. coli and S. aureus was assessed to determine their potential applications in silver-loaded antibacterial materials. This work provides useful technical parameters for industrialization of the biosynthetic technique and further antibacterial application of the AgNPs. Furthermore, the elucidation of bioreductive mechanism of silver ions by measuring the change of the biomolecular concentrations in plant extract exemplifies understanding the formation mechanism of such biogenic AgNPs.

Au/TS-1 catalysts could be prepared by immobilizing the biosynthesized Au sol on TS-1 supports. A variety of techniques, such as N2 physisorption, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectorscopy, UV–visible diffuse reflectance, and thermogravimetric analysis, were employed to characterize both the supports and the bioreduction catalysts. The influence of various parameters (Si/Ti molar ratio, Au loading, immobilization pH, reaction temperature, and space velocity) on the catalytic performance in vapor phase propylene epoxidation with H2/O2 was systematically analyzed. Parameter optimization results manifested that the optimum catalytic activity and stability of bioreduction Au/TS-1 catalysts were obtained under optimum operation conditions of Si/Ti molar ratio of 35, Au loading of 1 wt %, immobilization pH of 2, reaction temperature of 573 K, and space velocity of 4000–8000 mL gcat–1 h–1. Furthermore, efforts were also made to clarify the plausible reaction routes over the bioreduction catalysts.

A facile and eco-friendly method for the preparation of Au–Pd bimetallic nanoparticles (~ 7 nm) has been developed based on simultaneous bioreduction of Au(III) and Pd(II) precursors with Cacumen Platycladi leaf extract in aqueous environment. The morphology, structure, and size were confirmed with the aid of transmission electron microscopy, selected area electron diffraction, UV–vis spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. The results from Fourier transform infrared spectroscopy showed that the CO and CO groups in the plant extract played a critical role in capping the nanoparticles. Importantly, the process can be described as pure “green chemistry” technique since no additional synthetic reagents are used as reductants or stabilizers.Highlights► Au–Pd bimetallic nanoparticles were prepared by single-step bioreduction method. ► Bimetallic nanoparticles showed spherical shape with uniform size of 7.4 ± 0.8 nm. ► Characterization showed that the bimetallic nanoparticles were alloyed in nature. ► The plant extract played as both reductant and stabilizer for the nanoparticles.

Biosynthesized gold nanoparticles (GNPs) were transferred from water to a hydrophobic ionic liquid (IL), [Bmim]PF6, with the assistance of alkyl trimethyl ammonium bromide. The phase transfer mechanism was illustrated through the exemplification of cetyltrimethyl ammonium bromide (CTAB). Interaction between GNPs and CTAB was demonstrated through zeta potential analysis. Moreover, an anion-exchange process was discovered between CTAB and IL. During the process, the hydrophobic CTAPF6 formed in situ on the GNPs led to the hydrophobization and thus phase transfer of the GNPs. The phase transfer efficiency was found to be size-dependent.

Potassium diformate (KDF) has been regarded as an alternative to antibiotic growth promoters for animals. This paper delineates a 100% atom economical process for the preparation of KDF from formic acid and potassium formate. Parametric optimization of the synthesis was conducted with respect to reaction time, reaction temperature, and molar ratio of the reactants by employing orthogonal design of experiment method. The results manifested a molar ratio of HCOOH to HCOOK of 1.3, reaction temperature of 65 °C, and reaction time of 30 min as the optimal conditions with a KDF product yield of 94.0%. Efforts were also made to explore the antimold performance of KDF on animal feed using the plate count method. Compared with sodium diacetate (SDA), the widely used mold inhibitor, KDF exhibited even better antimold performance for animal feed. To our knowledge, this work first proved the applicability of KDF as a mold inhibitor for animal feed.

The development of dependable, environmentally benign processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. In the present study, we report one-pot biogenic fabrication of palladium nanoparticles by a simple procedure using broth of Cinnamomum camphora leaf without extra surfactant, capping agent, and/or template. The mean size of palladium nanoparticles, ranging from 3.2 to 6.0 nm, could be facilely controlled by merely varying the initial concentration of the palladium ions. The polyols components and the heterocyclic components were believed to be responsible for the reduction of palladium ions and the stabilization of palladium nanoparticles, respectively.

With the rapid expansion of the global motor vehicle population, the transportation sector has taken up a growing proportion among all the carbon dioxide emission-related sectors. To contribute to solutions of the carbon dioxide-oriented problem in transportation, this paper proposes the “ALL FREE” concept that applies partial oxidation process instead of the conventional complete oxidation to vehicle engines. In such an engine, the fuels are partially oxidized into corresponding chemical products, which, as a result, enable the process to be theoretically free of CO2, while the heat output of the partial oxidation could drive the vehicle. On the other hand, the resulting products are of great value, which could decrease or even counteract the cost of fuels in transportation. In this paper, the thermodynamic and kinetic data (e.g., the heat output and heat release rate) of five selected partial oxidation reactions were calculated at length to demonstrate and exemplify the theoretical feasibility of the “ALL FREE” concept. It turned out that the partial oxidation of n-butane to maleic anhydride has the most potential to meet the basic requirements of this concept. To sum up, this design concept is of significant application potential for the reduction of CO2 emissions in the transportation industry, although there remain many technical challenges.

Biosynthesis of nanoparticles has arisen as a promising alternative to conventional synthetic methodologies owing to its eco-friendly advantages, and the involved bioprotocol still needs further clarification. This research, for the first time from the standpoint of statistics, confirmed an electrostatic force or ionic bond-based interaction between the chloroauric ions and the involved bioconstituents and manifested that reducing sugars and flavonoids were both important reductants responsible for conversion of Au(III) to Au(0). The result also demonstrated that the proteins were not the reducing agents, yet they might be protection agents in biosynthesis of gold nanoparticles (GNPs). Besides, a significant linear relationship was found between the anti-oxidant ability of the foliar broths and their capability to reduce Au(III) into Au(0). Furthermore, the preliminary investigation based on the boxplot on the size/shape distribution of the biosynthesized GNPs revealed that gold nanospheres with higher degree of homogeneity in size tended to be promoted by foliar broths containing higher content of reducing sugars/flavonoids and proteins. Otherwise, i.e., for those broths with lower content of the above biocompounds, sphere GNPs of wider size distribution or even gold nanotriangles tended to be fabricated.(See supplementary material 1)

The phenol contents and the antioxidant activities of 12 Chinese longan cultivars were studied. The polyphenols of longan pericarp and seed demonstrated significantly higher antioxidant capacities than did the pulp. The ferric reducing antioxidant powers of longan fruits were closely correlated with the polyphenol contents (r2 = 0.8609, p < 0.001, n = 36). 52.9 mg g−1 (dry matter) polyphenols were extracted from the pericarp of cultivar Wulongling fruit with acetone aqueous along with ultrasonic treatment. Further fractionation was performed by Sephadex LH-20 chromatography. The results suggested that gallic acid (GA) and ellagic acid (EA) were not the major contributors to the antioxidant activity of longan pericarp. 15 other phenolic profiles in longan pericarp along with a number of unknown structures were revealed with high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC–ESI-MS) analysis. The rich array of phenolic compounds of several different types in longan pericarp extract might form a synergistic multilevel defence system against oxidation.

The degradation of anthraquinone dye Reactive Blue 19 (RB19) of 600 mg/L in the synthetic wastewater was studied using a biofilm hydrolytic–aerobic recycling process (recycling process). The COD (chemical oxygen demand) and RB19 removal efficiency could be up to 91% and 90% in 24 h, respectively, with the recycling rate being 10 mL/min. When the recycling rates were 8 mL/min and 10 mL/min, the average COD and RB19 removal rate reached the largest values of 109.9 mg/L h and 23.6 mg/L h, respectively. The results also showed that RB19 removal rate in both the hydrolytic and aerobic reactor declined whereas COD removal rate in the aerobic reactor increased with increasing of recycling rate. With the recycling rate of 10 mL/min, VFA (volatile fatty acid) in the wastewater was of the lowest value and pH value was apparently higher than those with other recycling rates. The ratios of VFA/alkalinity were all less than 0.6 when the recycling rate was more than 5 mL/min, which indicated that the activity of hydrolytic microorganisms had not been inhibited and the recycling process maintained a stable condition. Results in this work shown that hydrolytic–aerobic recycling process successfully dealt with the issues of over-acidification and inhibition in the hydrolysis process and effectively enhanced the removal efficiencies of RB19 and COD.

Biological production of silver nanoparticles by lixivium of sundried Cinnamomum camphora leaf in continuous-flow tubular microreactors was investigated. Properties of silver nanoparticles were examined by transmission electron microscopy (TEM), UV−vis spectroscopy, X-ray diffraction (XRD), and energy dispersive X-ray (EDX). The concentration of residual silver ions after reaction was measured by atomic absorption spectophotometry (AAS) spectroscopy. Fourier transform infrared (FTIR) spectra of C. camphora leaf lixivium were analyzed and temperature profiles along the tubes were calculated to explore formation mechanism of silver nanoparticles. Comparison of FTIR spectra of C. camphora leaf lixivium before and after reaction demonstrated the polyols in the lixivium may be mainly responsible for reduction of silver ions. According to the temperature profiles, at the inlet of the microreactors at 90 °C, the soar of the fluid temperature induced the burst of silver nuclei by homogeneous nucleation. Subsequently, the nuclei grew gradually along the reactors into silver nanoparticles from 5 to 40 nm. Polydisperse particles were formed by combination of heterogeneous nucleation and Ostwald ripening along the tubes at 60 °C.

SO42−/ZrO2 solid super-acid catalysts (SZ) doped with Ni2+ or Sn2+ (Ni2+/SZ, Sn2+/SZ) were prepared for catalytic visbreaking of heavy petroleum oil from Shengli oil field. The visbreaking reactions were carried out at 240°C and 3–4 MPa for 24 h using a heavy petroleum oil to catalyst mass ratio of 100 : 0.05. The effect of water content on viscosity of heavy petroleum oil was also investigated. Both catalysts can promote thermolysis of heavy petroleum oil and the viscosity was reduced from 0.319 Pa·s to 0.135 Pa·s for Ni2+/SZ and 0.163 Pa·s for (Sn2+/SZ) with visbreaking rates of 57.7% and 48.9%, respectively. After visbreaking, the saturated hydrocarbon content increased while aromatics, resin, asphaltene, sulfur and nitrogen content decreased. The presence of water was disadvantageous to visbreaking of heavy petroleum oil.

Microorganism-mediated, hexadecyltrimethylammonium chloride (CTAC)-directed (MCD) method was employed in this work to synthesize Pd nanoflowers (PdNFs). Proper Pichia pastoris cells (PPCs) dosage, ascorbic acid (AA), Pd(NO3)2 and CTAC concentrations were essential for the growth of the PdNFs. The size of the as-synthesized PdNFs could be tuned by adjusting the amount of Pd(NO3)2 solution and dosage of PPCs used. Characterization techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to verify the nature of the PdNFs. Finally the PdNF/PPC nanocomposites were immobilized onto TiO2 supports to obtain bio-PdNF/TiO2 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100% conversion at 100 °C and remaining stable over a period of 52 h of reaction time.Download full-size image

•This study presented a novel solid digestate-derived biochar-Cu NP composite.•The dispersive Cu NPs on biochar facilitated the decomposition of H2O2.•Tetracycline was nearly completely removed in both the liquid and solid phases.•OH was generated from the released Cu species and FRs in biochar activation of H2O2.Solid digestate, a by-product of anaerobic digestion systems, has led to a range of environmental issues. In the present study, a novel composite based on a solid digestate-biochar-Cu NP composite was synthesized for tetracycline removal from an aqueous medium. The removal efficiency values for tetracycline (200 mg L−1) were 31.5% and 97.8%, respectively, by the biochar-Cu NP composite (0.5 g L−1) in the absence and presence of hydrogen peroxide (H2O2, 20 mM) within 6 h of reaction time. The possible degradation pathway of tetracycline was investigated using liquid chromatography-mass spectrometry. The desorption experiment results suggested that no significant concentration of tetracycline was detected on the composite after the reaction, but a small amount of intermediates in terms of total organic carbon (TOC) accounting for 3.1%, and 23.3% of the end-product NH4+ was adsorbed onto the biochar sheets. The dispersive Cu NPs on the biochar resulted in an increase in the surface area and pore volume of the biochar-Cu NP composite, which enhanced tetracycline adsorption as well as the degradation efficiency. Relative tetracycline removal mechanisms were dominantly ascribed to ·OH generation from the Cu(II)/Cu(I) redox reaction with H2O2 and the electron-transfer process of free radicals (FRs) in biochar. The proposed approach serves dual purposes of waste digestate reuse and treatment of antibiotic pollutants.This study highlights the activation of H2O2 by the dispersive Cu NPs coupling with biochar derived from a waste solid digestate for tetracycline treatment.Download high-res image (247KB)Download full-size image

•Production of carbohydrate in microalgae from biogas slurry was proven feasible.•High ammonia removal efficiency, rate and carbohydrate content have been obtained in biogas slurry.•Phosphorus and magnesium starvation is proposed as a valid strategy for advancing the timing of carbohydrate accumulation in biogas slurry.•Magnesium is proved firstly as the influence factor for carbohydrate accumulation.In this study, five microalgae strains were cultured for their ability to survive in biogas slurry, remove nitrogen resources and accumulate carbohydrates. It was proved that five microalgae strains adapted in biogas slurry well without ammonia inhibition. Among them, Chlorella vulgaris ESP-6 showed the best performance on carbohydrate accumulation, giving the highest carbohydrate content of 61.5% in biogas slurry and the highest ammonia removal efficiency and rate of 96.3% and 91.7 mg/L/d respectively in biogas slurry with phosphorus and magnesium added. Additionally, the absence of phosphorus and magnesium that can be adverse for biomass accumulation resulted in earlier timing of carbohydrate accumulation and magnesium was firstly recognized and proved as the influence factor for carbohydrate accumulation. Microalgae that cultured in biogas slurry accumulated more carbohydrate in cell, making biogas slurry more suitable medium for the improvement of carbohydrate content, thus can be regarded as a new strategy to accumulate carbohydrate.Download high-res image (134KB)Download full-size image

The direct vapor-phase epoxidation of propylene in the presence of hydrogen and oxygen was studied at a space velocity of 7000mLh-1gcat.-1 over gold catalysts with varying gold and titanium contents prepared by ionic liquid-enhanced immobilization (ILEI) method in which biosynthesized gold nanoparticles (GNPs) were immobilized onto the titanium silicalite-1 (TS-1) supports through the assistance of a small amount of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). The results showed that [BMIM]+ specially adsorbed onto the support to increase its isoelectric point, leading to the enhanced immobilization. The propylene conversion of 14.6% and PO formation rate of 164.4gpoKgcat.-1h-1 were higher than those in any other reports, probably attributing to enhanced interaction between the GNPs and TS-1. Furthermore, the excellent activity and high selectivity of the Au/TS-1 catalysts at a relatively high reaction temperature might be attributed to the existence of residual biomolecules on the catalysts.Graphical abstractBiosynthesized gold nanoparticles (GNPs) were immobilized onto TS-1 through 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). [BMIM]+ specially adsorbed onto the support to increase its isoelectric point, leading to the enhanced immobilization and high activity and stability for propylene epoxidation with H2/O2 mixture, probably attributing to enhanced interaction between the GNPs and TS-1 and the role of residual biomolecules in protecting the GNPs thereof.Download high-res image (45KB)Download full-size imageHighlights► The gold nanoparticles were prepared by biosynthesis method. ► Au nanoparticles were completely immobilized on TS-1 support with ionic liquid. ► Au/TS-1 catalysts exhibited high activity and stability for propylene epoxidation. ► About 4.6% of propylene conversion could be obtained. ► The isoelectric point of TS-1 could be changed by ionic liquid.

This critical review focuses on recent advances in the bio-inspired synthesis of metal nanomaterials (MNMs) using microorganisms, viruses, plants, proteins and DNA molecules as well as their applications in various fields. Prospects in the design of bio-inspired MNMs for novel applications are also discussed.