scholarly journals Characterizing the impact of MnO2 addition on the efficiency of Fe0/H2O systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Viet Cao ◽  
Ghinwa Alyoussef ◽  
Nadège Gatcha-Bandjun ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Ph Value ◽  
Iron Corrosion ◽  
Dissolved Iron ◽  
Ph Values ◽  
Solid Iron ◽  
Initial Ph ◽  
Fixation Capacity ◽  
Co Precipitation ◽  
The Impact

AbstractThe role of manganese dioxide (MnO2) in the process of water treatment using metallic iron (Fe0/H2O) was investigated in quiescent batch experiments for t ≤ 60 d. MnO2 was used as an agent to control the availability of solid iron corrosion products (FeCPs) while methylene blue (MB) was an indicator of reactivity. The investigated systems were: (1) Fe0, (2) MnO2, (3) sand, (4) Fe0/sand, (5) Fe0/MnO2, and (6) Fe0/sand/MnO2. The experiments were performed in test tubes each containing 22.0 mL of MB (10 mg L−1) and the solid aggregates. The initial pH value was 8.2. Each system was characterized for the final concentration of H+, Fe, and MB. Results show no detectable level of dissolved iron after 47 days. Final pH values varied from 7.4 to 9.8. The MB discoloration efficiency varies from 40 to 80% as the MnO2 loading increases from 2.3 to 45 g L−1. MB discoloration is only quantitative when the operational fixation capacity of MnO2 for Fe2+ was exhausted. This corresponds to the event where adsorption and co-precipitation with FeCPs is intensive. Adsorption and co-precipitation are thus the fundamental mechanisms of decontamination in Fe0/H2O systems. Hybrid Fe0/MnO2 systems are potential candidates for the design of more sustainable Fe0 filters.

scholarly journals Characterizing the impact of pyrite addition on the efficiency of Fe0/H2O systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rui Hu ◽  
Xuesong Cui ◽  
Minhui Xiao ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Methylene Blue ◽  
Methyl Orange ◽  
Ph Value ◽  
Batch Experiments ◽  
Ph Variation ◽  
Ph Values ◽  
Ph Shifting ◽  
Co Precipitation ◽  
The Impact

AbstractThe role of pyrite (FeS2) in the process of water treatment using metallic iron (Fe0) was investigated. FeS2 was used as a pH-shifting agent while methylene blue (MB) and methyl orange (MO) were used as an indicator of reactivity and model contaminant, respectively. The effect of the final pH value on the extent of MB discoloration was characterized using 5 g L−1 of a Fe0 specimen. pH variation was achieved by adding 0 to 30 g L−1 of FeS2. Quiescent batch experiments with Fe0/FeS2/sand systems (sand loading: 25 g L−1) and 20 mL of MB were performed for 41 days. Final pH values varied from 3.3 to 7.0. Results demonstrated that MB discoloration is only quantitative when the final pH value was larger than 4.5 and that adsorption and co-precipitation are the fundamental mechanisms of decontamination in Fe0/H2O systems. Such mechanisms are consistent with the effects of the pH value on the decontamination process.

scholarly journals The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Viet Cao ◽  
Ghinwa Alyoussef ◽  
Nadège Gatcha-Bandjun ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Contact Time ◽  
Diffusive Transport ◽  
Iron Hydroxides ◽  
Iron Corrosion ◽  
Short Term ◽  
Batch Studies ◽  
Water Decontamination ◽  
Co Precipitation

AbstractMetallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.

scholarly journals Bonding of Selected Hardwoods with PVAc Adhesive

2020 ◽  
Vol 11 (1) ◽  
pp. 67
Author(s):  
Ján Iždinský ◽  
Ladislav Reinprecht ◽  
Ján Sedliačik ◽  
Jozef Kúdela ◽  
Viera Kučerová
Keyword(s):  
Adhesion Strength ◽  
Cold Water ◽  
Ph Value ◽  
Water Extract ◽  
Solid Wood ◽  
Contact Angles ◽  
Water Contact ◽  
Ph Values ◽  
Positive Tendency ◽  
The Impact

The bonding of wood with assembly adhesives is crucial for manufacturing wood composites, such as solid wood panels, glulam, furniture parts, and sport and musical instruments. This work investigates 13 hardwoods—bangkirai, beech, black locust, bubinga, ipé, iroko, maçaranduba, meranti, oak, palisander, sapelli, wengé and zebrano—and analyzes the impact of their selected structural and physical characteristics (e.g., the density, cold water extract, pH value, roughness, and wettability) on the adhesion strength with the polyvinyl acetate (PVAc) adhesive Multibond SK8. The adhesion strength of the bonded hardwoods, determined by the standard EN 205, ranged in the dry state from 9.5 MPa to 17.2 MPa, from 0.6 MPa to 2.6 MPa in the wet state, and from 8.5 MPa to 19.2 MPa in the reconditioned state. The adhesion strength in the dry state of the bonded hardwoods was not influenced by their cold water extracts, pH values, or roughness parallel with the grain. On the contrary, the adhesion strength was significantly with positive tendency influenced by their higher densities, lower roughness parameters perpendicular to the grain, and lower water contact angles.

Catalytic Hydrolysis of Hydrogen Cyanide on Cu-Al Catalyst

2015 ◽  
Vol 1094 ◽  
pp. 15-19
Author(s):  
Lin Xia Yan ◽  
Sen Lin Tian ◽  
Qiu Lin Zhang
Keyword(s):  
Calcination Temperature ◽  
Hydrogen Cyanide ◽  
Influence Factor ◽  
Ph Value ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Cu Content ◽  
Co Precipitation ◽  
The Impact ◽  
Hydrolysis Of

Cu-Al catalysts were synthesized by the co-precipitation method to study hydrolysis of hydrogen cyanide. During the synthesis, the impact of Cu/Al molar ratio, pH value and calcination temperature was investigated and the best synthesis condition was found. The results indicate that the remove of hydrogen cyanide first increases and then decreases with increasing Cu/Al molar ratio, pH value and calcination temperature, which reaches the maxima and remains above 95% at 360 min when Cu/Al molar ratio is 2:1, pH value is approximately 8.0 and calcination temperature is 400°C around. The analysis of X-ray diffraction (XRD) shows that Cu content is the main influence factor at Cu/Al molar ratio below 2:1 whereas crystallinity of catalysts is the key factor at Cu/Al molar ratio above 2:1.

Effect of Environment Factors on Phosphorus Removal Efficiency of Phosphate Reduction System

2011 ◽  
Vol 255-260 ◽  
pp. 2797-2801
Author(s):  
Chen Yao ◽  
Chun Juan Gan ◽  
Jian Zhou
Keyword(s):  
Removal Efficiency ◽  
Phosphorus Removal ◽  
Ph Value ◽  
Removal Rate ◽  
Mass Rearing ◽  
Phosphate Removal ◽  
Environment Factors ◽  
Reduction System ◽  
Initial Ph ◽  
The Impact

Effect of environment factors such as initial pH value, dissolved oxygen (DO) and temperature on phosphorus removal efficiency of phosphate reduction system was discussed in treating pickled mustard tube wastewater. Results indicate that environment factors have significant influence on dephosphorization efficiency. And, the impact of DO on phosphate reduction is mainly by affecting the distribution of micro-environment inner biofilm, manifest as phosphate removal rate decreased with a fall in DO concentration, while overhigh DO can lead to detachment of biofilm, thus causing the increase of effluent COD concentration, and so DO need to be controlled in the range of 6 mg/L. Moreover, a higher temperature is more beneficial to phosphorus removal by PRB. Unfortunately, exorbitant temperature can result in mass rearing of Leuconostoc characterized with poor flocculability in reactor, and that cause turbidity in effluent appeared as a rise in COD of effluent. Hence, the optimal temperature is found to be about 30°C.

Optimization of Kaolin Bioleaching by Aspergillus niger

2007 ◽  
Vol 20-21 ◽  
pp. 115-118 ◽  
Author(s):  
M. Ranjbar ◽  
E. Aghaie ◽  
M.R. Hosseini ◽  
Mohammad Pazouki ◽  
F. Ghavipanjeh
Keyword(s):  
Aspergillus Niger ◽  
Ph Value ◽  
Iron Concentration ◽  
Iron Removal ◽  
Pistachio Shell ◽  
Dissolved Iron ◽  
Initial Ph ◽  
Negative Effect ◽  
Concentration Changes ◽  
Central Composite

In this paper, a central composite design was applied to optimize the bioleaching of iron from a kaolin sample containing 2.2% iron impurity by Aspergillus niger isolated from pistachio shell. The strains were inoculated into 500 ml flasks containing 100 ml media consisted of (g/l): sucrose 120; NH4NO3 0.45; KH2PO4 0.1; MgSO4.7H2O 0.3; FeSO4.7H2O 10-4; ZnSO4.7H2O 25×10- 5. The effects of initial pH, sugar and spore concentrations on iron removal extent were investigated. The two-level factorial design points were pH 2 and 5, sugar conc. 70 g/l and 130 g/l, spore conc. 9×107 and 35×107 spores/l. Also, the increase of dissolved iron, oxalic acid concentration, changes in pH value, and sugar concentration were registered. Consequently, after 10 days, the iron concentration of the best condition reached to 179.3 ppm that means 38.8% of the total iron content is removed. Furthermore, the data analysis showed that all the factors are significant, and the iron removal extent increases by increasing the initial pH to 4.4, sucrose content to 93.8 g/l, and spore concentration to 305.5 spores/μl, but further increase in each factor value has negative effect on the response.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

2019 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte i.e. proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included in the model. It can be regarded as a kind of "minimal'' model in the sense that contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase, and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 to low pH-values (Pincus regime), is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

scholarly journals Revisiting the fundamentals of p-nitrophenol analysis for its application in the quantification of lipases activity. A graphical update.

Uniciencia ◽  
2020 ◽  
Vol 34 (2) ◽  
pp. 31-43
Author(s):  
Randall Syedd-León ◽  
Manuel Sandoval-Barrantes ◽  
Humberto Trimiño-Vásquez ◽  
Luis Roberto Villegas-Peñaranda ◽  
Gerardo Rodríguez-Rodríguez
Keyword(s):  
Lipase Activity ◽  
Ph Value ◽  
Protonated Form ◽  
Spectrophotometric Analysis ◽  
Spectrophotometric Methods ◽  
Ph Values ◽  
Reaction Media ◽  
Activity Quantification

p-Nitrophenol (pNP) is a widely used compound for analytical determinations of several esterases (EC. 3.1.1.X), including lipases (E.C. 3.1.1.3). Most enzymatic measurements employ pNP derivatives such as esters, which are broken down by enzymatic hydrolysis, releasing pNP that is quantified by its absorbance at 410 nm. Although this type of methods was developed a few decades ago, the spectrophotometric analysis of pNP requires analytical measurements of pH and temperature to achieve reliable determinations. The aim of this paper is to offer a graphical update of how pH and temperature affect the p-nitrophenol absorbance at different wavelengths in lipase emulsified media, due to its relevance for the quantitative determination of lipase activity using spectrophotometric methods. To highlight the importance of each variable involved in this analysis, we dissolved pNP in emulsified media (for lipase activity quantification) at several pH values from 4.00 to 11.00, and measured its absorbance in a range of 270 nm – 500 nm and at several temperatures from 25°C to 50°C. The absorption patterns of pNP under the established conditions were graphed in 3D plots. The constructed 3D plots showed that, regardless of the temperature, below pH 6.00, pNP predominantly absorbs at 317 nm, due to the greater abundance of its protonated form, which is completely predominant at pH 3.50 and below. On the other hand, at pH 10.0 and above, the major absorption occurs at about 401 nm, confirming that the equilibrium is completely shifted to the pNP anionic form. These results also indicate that close to neutral pH value pNP, it displays a temperature dependence effect, increasing absorbance to 410 nm at higher temperatures. Due to many analytical determinations of enzymatic activities, the release of pNP is carried around pH 7.00. It is necessary to consider the determinant role of both pH and temperature over these measurements, how these variables must be strictly controlled, and how the calibration curves and blanks should take the reaction media pH and temperature into account.

The Role of Acetate in Denitrification and Biological Phosphate Removal in Modified Bardenpho Systems

1989 ◽  
Vol 21 (4-5) ◽  
pp. 375-385 ◽  
Author(s):  
C. T. Winter
Keyword(s):  
Sodium Acetate ◽  
Ph Value ◽  
Phosphate Removal ◽  
Organic Substances ◽  
Phosphate Release ◽  
Ph Values ◽  
Experimental Systems ◽  
Removal Capacity ◽  
Equivalent Sequence

The importance of easily biodegradable organic substances such as acetate and propionate in biological phosphate removal has been recognised by many researchers. Laboratory-scale studies on the performance of three-stage modified Bardenpho nutrient removal systems, fed with settled sewage supplemented with 0, 50, 100 and 200 mg/l sodium acetate respectively are described. Particular attention is given to the effects of these additions on biological phosphate release and uptake and also to the fate of parameters such as pH, calcium, potassium, ammonia and nitrate. Additional phosphate of 10 mg/l (as P) was initially introduced into the feed in order to burden the experimental systems beyond their normal phosphate removal capacity. This was increased to 20 mg/l and eventually to 40 mg/l of phosphate (as P). Increasing concentrations of sodium acetate resulted in distinct increases in pH values, increase in phosphate release in the anaerobic zones and significantly improved overall phosphate removal in the experimental units. The correlation of phosphate removal on acetate concentration was found to be 0.9886. In some instances the unit receiving 200 mg/l acetate removed up to an average of 30 mg/l of phosphate (as P), constituting an improvement of up to 200% compared with the unit receiving no acetate. The alternating release and uptake of phosphate was accompanied by an equivalent sequence for potassium and magnesium. The high pH value plus the disappearance of phosphate, ammonia and magnesium places doubt on a purely biological phosphate removal but could point at the crystallization of ammonium magnesium phosphate.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1962 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte that is, proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included. This model can be regarded as a kind of “minimal” in the sense that it contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both, with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 at low pH-values (Pincus regime) is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to the changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

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