Continuous-flow Column Reactor Research Articles

Bifunctional Co3O4-La2O2CO3@C derived from MOFs for peroxymonosulfate activation to degrade roxarsone and simultaneous removal of released inorganic arsenic from water

• MOFs derived difunctional Co 3 O 4 -La 2 O 2 CO 3 @C was successfully fabricated. • ROX was efficiently degraded by Co 3 O 4 -La 2 O 2 CO 3 @C activated PMS. • The generated arsenic was simultaneously adsorbed onto Co 3 O 4 -La 2 O 2 CO 3 @C. • Co 3 O 4 -La 2 O 2 CO 3 @C exhibited superior stability and reusability. • SO 4 − and OH were involved in the oxidation and transformation of ROX. In this study, a novel Co 3 O 4 -La 2 O 2 CO 3 @C composite was fabricated via the calcination of Co-La bimetallic MOFs at 500 °C, and was employed to efficiently activate peroxymonosulfate (PMS) for simultaneous oxidation of roxarsone (ROX) and adsorption of concomitant inorganic arsenic. Approximately 100% of ROX (50 μmol L −1 ) was degraded by PMS (0.5 mmol L −1 ) activated with Co 3 O 4 -La 2 O 2 CO 3 @C (0.2 g L −1 ) at initial pH 6 within 10 min. Meanwhile, the produced inorganic arsenic was almost completely adsorbed within 90 min. The maximum adsorption capacity of As(V) by Co 3 O 4 -La 2 O 2 CO 3 @C was determined to be high up to 275.4 mg g −1 . Co 3 O 4 -La 2 O 2 CO 3 @C also exhibited superior stability. During 6 rounds, the degradation efficiency of ROX and the removal efficiency of the total As maintained almost 100% and more than 97%, respectively. SO 4 − and OH were confirmed to be the reactive oxygen species (ROS) in charge of the degradation of ROX and the conversion of As(III) to As(V). The investigation of the adsorption mechanism revealed that the As species were combined with La species via ligand and anion exchange, resulting in the formation of La-O-As bond. Furthermore, the practical application potential of Co 3 O 4 -La 2 O 2 CO 3 @C in the ROX degradation and the in-situ adsorption of the released arsenic were further evaluated in a continuous flow column reactor. The Co 3 O 4 -La 2 O 2 CO 3 @C composite as catalyst and adsorbent may offer a feasible strategy for the implementation of organoarsenic degradation and produced inorganic arsenic adsorption.

Enhanced biosorption of fluoride by extracted nanocellulose/polyvinyl alcohol composite in batch and fixed-bed system: ANN analysis and numerical modeling.

The present investigation attempted to examine the defluoridation feasibility onto the extracted nanocellulose/PVA polymer composites. Nanocellulose were derived from sugarcane bagasse and blended with PVA (polyvinyl alcohol) polymer matrix. The defluoridation potential of nanocellulose/PVA was observed to be significantly dependent on the various operational factors including pH, time interval, etc. the Temkin isotherm (R2 = 0.989) as well as the Langmuir isotherm equation (R2 = 0.982) could well fit with the investigational data. Following the Langmuir isotherm, the maximum monolayer adsorption capacity for fluoride elimination at 25°C was obtained as 11.363 mg g-1. The nature of rate-limiting steps involved in defluoridation process might be effectively predicted by pseudo-second-order kinetics. Values of thermodynamic state properties achieved as of the thermodynamic analysis showed that the defluoridation process was spontaneous, exothermic, and feasible. The diffusion and mass transfer study were estimated by following the Boyd's model. Average effective diffusion coefficient (De) at various initial fluoride concentrations (4-10 mg L-1) was obtained as 15.3343×10-7 m2s-1 and the estimated magnitude of the mass-transfer coefficient (Kf) was 0.0346×10-9 m s-1 (temperature = 298 K, C0= 6 mgL-1). An ANN (artificial neural network) model applied to optimize and simulate the defluoridation procedure. Furthermore, continuous flow column reactor was conducted to investigate the practical applicability of composites in the defluoridation process. The Yoon-Nelson and the Thomas model exhibited excellent conformity with the breakthrough curves. Nanocellulose/PVA satisfactorily eliminated fluoride from its aqueous solution and can be considered as a suitable bio-sorbent for defluoridation.

Oxidation of arsenite by self-regenerative bioactive birnessite in a continuous flow column reactor

Naturally occurring manganese (Mn) oxide, biogenic birnessite ((Na, Ca, K)0.5 MnIII, IV2O4·1.5 H2O), is involved in the geochemical cycling of variety of metals including arsenic (As). This natural reaction was exploited in this study to develop a sustainable oxidation treatment process of As(III) to the less soluble (and less toxic) As(V). It is known that the birnessite surface becomes passivated during As(III) oxidation, which quickly decreases its reactivity. The cycle batch test and the following XANES (X-ray absorption near-edge structure) analysis in this study confirmed that combining chemical As(III) oxidation by birnessite with simultaneous birnessite regeneration by Mn-oxidizing microorganisms (Pseudomonas sp. SK3) can avoid passivation of MnIII-precipitates and enables continuous As(III) oxidation while increasing the AOS (average oxidation state) of birnessite. This chemical/microbiological synergism was observed for the As(III) concentration range of 0.2–0.5 mM with 0.1% birnessite, wherein no net Mn loss from birnessite was noticed for complete As(III) oxidation. The continuous column test was run for 40 days at a HRT (hydraulic retention time) of 3 h by feeding a 0.2 mM As(III) solution. The As(III) oxidation efficiency of >98% was consistently achieved while strictly controlling the Mn2+ dissolution throughout the test period. This study concluded that by taking advantage of a robust microbial Mn-oxidizing activity, the use of “bioactive” birnessite realizes self-sustainable oxidation of As(III), without necessitating additional feed of oxidant birnessite, Mn2+ ions or organics.

Biogenic coal-to-methane conversion can be enhanced with small additions of algal amendment in field-relevant upflow column reactors

Subsurface coal environments, where biogenic coal-to-methane conversion occurs, are difficult to access, resulting in inherent challenges and expenses for in situ experiments. Previous batch reactor studies provided insights into specific processes, pathways, kinetics, and engineering strategies, but field-relevance is restricted due to limited substrate availability or byproduct accumulation that may influence reactions or metabolisms. In this study, continuous-flow column reactors were used to overcome some batch limitations, improve the understanding of in situ conditions, and increase field-relevance for subsurface engineering technology development. The bench-scale reactor system was constructed to investigate the addition of algal amendment for enhancing microbial coal-to-methane conversion previously developed in batch systems. Four reactor columns were packed with coal and inoculated with a microbial consortium from the same Flowers-Goodale coal bed. Two reactors were amended with 13C-labeled algal amendment on day 0, and two were unamended. On day 61, one previously amended and one previously unamended reactor were re-amended. Produced gases were captured in a gas trap, and CH4 and CO2 were quantified. The reactor amended twice produced 1712.6 µmol CH4 (4.6% as 13CH4). The reactor amended only on day 0 produced 1485.5 µmol CH4 (2.6% as 13CH4). The reactor amended only on day 61 produced 278.9 µmol CH4 (3.9% as 13CH4). The reactor with no amendment produced no measurable gases for the duration of the 172-day experiment. Amendment increased the rate of coal-to-methane conversion and total gas production; most of the produced gases were due to coal conversion with only small contributions (<7%) from amendment conversion.

Improving catalytic activity of supported Au nanoparticles depending on its density

Supporting density of Au nanoparticles on the surface of magnetic carrier was carefully investigated because of its great effect on the catalytic activity. Micro-sized magnetic polymer beads (Fe3O4@PMMA) were employed to immobilize Au nanoparticles due to its easy surface modification and rapid magnetic separation. By controlling the supporting density and particles size of Au NPs, the catalytic activity of immobilized Au NPs in reducing p-nitrophenol was effectively improved. When 10nm Au NPs were employed to be immobilized on the magnetic carrier with the density of 4292μg/g, the catalytic activity of Fe3O4@PMMA/Au even approached to that of isolated Au NPs, which indicated that suitable supporting density of Au NPs might compensate some drawbacks of heterogeneous catalysts. It meant that the catalytic activity of Au NPs was not damaged even after its immobilization. Furthermore, this magnetic supported catalyst could be easily separated and recycled. After 23 runs of recycling, no significant loss of catalytic activity was found. This catalyst also performed high catalytic activity in continuous-flow column reactors, which showed much potential in practical application.

Electrochemically enhanced reduction of trichloroethene by passivated zero-valent iron

Zero-valent iron (ZVI) is commonly used for the in situ remediation of groundwater aquifers contaminated with trichloroethylene (TCE); however, ZVI is susceptible to passivation over time, which can significantly reduce its treatment efficiency. Recent studies have suggested that electrically-induced reduction (EIR) or "E-Redox" technology, which applies a low-level direct current (DC), can restore the reactivity of passivated ZVI in situ. In this study, a continuous-flow column reactor was used to assess the effects of low-voltage DC on the abiotic reduction of TCE in groundwater and on the performance of passivated ZVI. In experiments with partially passivated ZVI, the application of DC increased the rate and the extent of TCE reduction; both were correlated with the level of applied voltage (0–12V). The results provide evidence that EIR may partially recover the reduction potential of passivated ZVI and shows promise as a technique to extend the longevity of zero-valent iron. Several mechanisms, including the reduction of ferric iron minerals to ferrous iron at the ZVI surface, likely results in the enhanced TCE reduction.

Palladium supported on alginate/ionic liquid highly porous monoliths: Application to 4-nitroaniline hydrogenation

A catalytic system was designed in the form of highly porous monoliths (HPM) in order to be used in a continuous flow column reactor. This catalyst system was composed of an ionic liquid and a transition metal catalyst supported on a biopolymer matrix. Alginate was used as a natural support for immobilizing Cyphos IL-111 (an alkylphosphonium ionic liquid) and for Pd binding. The supported catalyst was efficiently used for the hydrogenation of 4-nitroaniline in the presence of either sodium formate or formic acid as the hydrogen donor. The catalytic HPM was elaborated using a combined procedure of solution icing and freeze-drying. The HPM could be used in a fixed-bed column system under “forced flux” (and recycling mode). The hydrogenation reaction, studied with solution recycling through the HPM, was mainly influenced by the flow rate in the column, the excess of hydrogen donor, the pH of the solution and the type of acid used for pH control (poisoning effect of chloride ions), but was poorly influenced by temperature. The hydrogenation reaction, in the single-pass mode, showed breakthrough curves of higher catalytic activity for HCOONa as hydrogen donor than for HCOOH.

Chlorinated solvent aerobic biodegradation via cometabolism in a continuous-flow column reactor

Chlorinated solvent aerobic biodegradation via cometabolism in a continuous-flow column reactor

Chimeric Lactase Capable of Spontaneous and Strong Immobilization on Cellulose and Development of a Continuous-Flow System for Lactose Hydrolysis at High Temperatures

Recombinant plasmids containing fusion proteins composed of two different modules were constructed and expressed in Escherichia coli. The modules encoded the lactase LacA (LacZ) from the thermophilic bacterium Thermoanaerobacter ethanolicus and the cellulase CelD, a cellulose-binding module (CBM) from Anaerocellum thermophilum. The CelD CBM provides a spontaneous and strong sorption of the fusion proteins onto a cellulose carrier. The enzymatic activities of both the free LacA protein and LacA-CelD CBM fusion proteins immobilized onto the cellulose carrier were assessed. The LacA activity of the fusion protein was dependent upon its position with respect to the CBM. The highest level of lactase activity and stability was observed when the lactase domain was localized at its N terminus. A continuous-flow column reactor of lactase immobilized on a cellulose carrier was constructed, and its activity was assessed. The lactose hydrolysis rate for a 150 mM (5%) solution at a flow rate of 1 reactor volume per min was 75%, which is a value optimal for further whey transformation into glucose/galactose syrup.

Bacterial reductive dissolution of crystalline Fe(III) oxide in continuous-flow column reactors.

Bacterial reductive dissolution of synthetic crystalline Fe(III) oxide-coated sand was studied in continuous-flow column reactors in comparison with parallel batch cultures. The cumulative amount of aqueous Fe(II) exported from the columns over a 6-month incubation period corresponded to (95.0 +/- 3.7)% (n = 3) of their original Fe(III) content. Wet-chemical analysis revealed that only (6.5 +/- 3.2)% of the initial Fe(III) content remained in the columns at the end of the experiment. The near-quantitative removal of Fe was visibly evidenced by extensive bleaching of color from the sand in the columns. In contrast to the column reactors, Fe(II) production quickly reached an asymptote in batch cultures, and only (13.0 +/- 2.2)% (n = 3) of the Fe(III) oxide content was reduced. Sustained bacterial-cell growth occurred in the column reactors, leading to the production and export of a quantity of cells 100-fold greater than that added during inoculation. Indirect estimates of cell growth, based on the quantity of Fe(III) reduced, suggest that only an approximate doubling of initial cell abundance was likely to have occurred in the batch cultures. Our results indicate that removal of biogenic Fe(II) via aqueous-phase transport in the column reactors decreased the passivating influence of surface-bound Fe(II) on oxide reduction activity, thereby allowing a dramatic increase in the extent of Fe(III) oxide reduction and associated bacterial growth. These findings have important implications for understanding the fate of organic and inorganic contaminants whose geochemical behavior is linked to Fe(III) oxide reduction.

Interactions between Fusarium culmorum and its potential biocontrol agent, Trichoderma harzianum, in a packed-bed, continuous-flow column reactor

The interaction between the filamentous fungi Fusarium culmorum and Trichoderma harzianum was studied. A continuous-flow column reactor analogous to a soil column was used to provide a unidirectional flow of nutrients and solid support particles to which the fungi could attach. Such a system gave rise to a heterogeneous distribution of microorganisms and concentration gradients, and thus exhibited the most significant physical characteristics of the soil. In columns inoculated with both fungal species, a succession in population dominance was observed. F. culmorum was the dominant organism at the beginning of the experiment; however, it was gradually replaced by T. harzianum. To analyze the results obtained from the dual culture columns, a mathematical model was developed. Three functions representing interaction between the two species were tested to determine which represented the experimental results most accurately. The best qualitative fit was obtained with a model incorporating Monod kinetics and making logistic limitation of F. culmorum a linear function of the population density of T. harzianum. The implication of combined experimental and mathematical evidence was that the interaction between the two species was not solely competition for a single resource; the population of T. harzianum had a direct effect on that of F. culmorum.

Immobilization of the serine protease from Thermomonospora fusca YX on porous glass

As much as 84% of the thermostable serine protease from Thermomonospora fusca strain YX was covalently attached to silanized glass using glutaraldehyde. The immobilized protease exhibited a higher temperature optimum (86 degrees C) and pH optimum (9.4) for activity compared to soluble YX-protease (80 degrees C and pH 9.0, respectively). Immobilization improved enzyme thermo-stability above 90 degrees C and reduced inactivation during prolonged storage (9% loss of activity after 90 days at 12 degrees C). A continuous-flow column reactor packed with immobilized protease readily hydrolyzed casein over broad ranges of temperature and pH.

Catalytic Transfer Hydrogenation of Glucose‐Fructose Syrups in Alkaline Solution

AbstractEquimolar mixtures of glucose and fructose were found to undergo quantitative transfer hydrogenation yielding equal amounts of gluconic acid and of hexitols (mannitol and sorbitol). The oxidationreduction occurs in aqueous alkaline medium under nitrogen at room temperature in the presence of Pt/C or Rh/C as the catalyst. Other group VIII metals did not give satisfactory results. Both a stirred batch and a continuous flow column reactor have been applied. The influence of several reaction variables has been studied, leading to the conclusion that the rate‐limiting step ist the dehydrogenation reaction of glucose into gluconic acid and chemisorbed hydrogen. Subsequently, the latter is quickly consumed by coadsorbed fructose under formation of mannitol and sorbitol (in the ratio of 1.5. – 1.9: 1). Alkaline degradation products are found to be of minor importance at temperatures ≦ 25°C.