scholarly journals Experimental Analysis and Modeling of Nitrate Removal through Zero-Valent Magnesium Particles

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1276 ◽  
Author(s):  
Siciliano ◽  
Curcio ◽  
Limonti
Keyword(s):  
Nitrate Concentration ◽  
Nitrate Removal ◽  
Experimental Results ◽  
Process Efficiency ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Nitrogen Forms ◽  
Sustainable Technologies ◽  
Batch Tests ◽  
Effects Of Ph

The pollution of water by nitrates represents an important environmental and health issue. The development of sustainable technologies that are able to efficiently remove this contaminant is a key challenge in the field of wastewater treatment. Chemical denitrification by means of zero-valent metallic elements is an interesting method to reduce the oxidized forms of nitrogen. Compared to other metallic reactants, zero-valent magnesium (ZVM) has many profitable aspects, but its use for nitrate removal has scarcely been investigated. In the present work, several batch tests were conducted to examine the concurrent effects of pH, initial nitrate concentration and Mg0 quantity on process performance. The experimental results proved that at pH 3, for a given initial nitrate concentration, the dose of ZVM largely influences process efficiency. In particular, with a ratio between Mg0 and initial N-NO3− amount (Mg/NNi) of 0.33 g/mg, it is possible to obtain complete denitrification within 30 min. Beyond this ratio, no further improvement of treatment was observed. The experiments allowed us to identify the nitrogen forms produced during the treatment. Nitrogen gas was generally the main reaction product, but the trends of the different compounds (NO3−, NO2−, NH4+ and N2) notably changed in response to the modification of operating parameters. Moreover, the results demonstrated that, in a highly acidic environment, when treating solutions with a low nitrate concentration, process performances are unsatisfactory even when using a high Mg/NNi ratio. By increasing the process pH to 5 and 7, a significant denitrification decline occurred. Furthermore, at these pH levels, the enhancement of nitrate concentration caused a progressive process deterioration. Through detailed analysis of experimental results, reactions kinetics and new mathematical equations, able to describe the trends of different nitrogen forms, have been defined. Moreover, reactions pathways have been proposed. Finally, the characterization of exhausted material allowed us to identify the corrosion products formed during the treatment.

scholarly journals Chemical Denitrification with Mg0 Particles in Column Systems

2020 ◽  
Vol 12 (7) ◽  
pp. 2984 ◽  
Author(s):  
Alessio Siciliano ◽  
Giulia Maria Curcio ◽  
Carlo Limonti
Keyword(s):  
Kinetic Constant ◽  
Operating Parameter ◽  
Process Efficiency ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Reaction Products ◽  
Metallic Elements ◽  
Reactive Material ◽  
Maximum Reaction Rate ◽  
Maximum Reaction

The removal of nitrate from aqueous environments through zero-valent metallic elements is an attractive technique that has gained increasing interest in recent years. In comparison to other metallic elements, zero-valent magnesium (ZVM) has numerous beneficial aspects. Nevertheless, the use of Mg0 particles for nitrate reduction in column systems has not been investigated yet. To overcome the lack of research, in the present study, a wide experimental activity was carried out to develop a chemical denitrification process through ZVM in batch column equipment. Several tests were executed to evaluate the effects of recirculation hydraulic velocity, pH, Mg0 amount, N-NO3− initial concentration and temperature on the process performance. The results show that the process efficiency is positively influenced by the recirculation velocity increase. In particular, the optimal condition was detected with a value of 1 m/min. The process pH was identified as the main operating parameter. At pH 3, abatements higher than 86.6% were reached for every initial nitrate concentration tested. In these conditions, nitrogen gas was detected as the main reaction product. The pH increase up to values of 5 and 7 caused a drastic denitrification decline with observed efficiencies below 26%. At pH 3, the ratio (RMN) between Mg0 and initial nitrate amount also plays a key role in the treatment performance. A characteristic value of about RMN = 0.333 gMg0/mgN-NO3− was found with which it is possible to reach the maximum reaction rate. Unexpectedly, the process was negatively affected by the increase in temperature from 20 to 40 °C. At 20 °C, the material showed satisfactory denitrification efficiencies in subsequent reuse cycles. With the optimal RMN ratio, removals up to 90% were detected by reusing the reactive material three times. By means of a kinetic analysis, a mathematical law able to describe the nitrate abatement curves was defined. Moreover, the relation between the observed kinetic constant and the operating parameters was recognized. Finally, the reaction pathways were proposed and the corrosion reaction products formed during the treatment were identified.

scholarly journals Denitrification Kinetics of Nitrate by a Heterotrophic Culture in Batch and Fixed-Biofilm Reactors

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 547
Author(s):  
Yen-Hui Lin ◽  
Yi-Jie Gu
Keyword(s):  
Continuous Flow ◽  
Nitrate Concentration ◽  
Batch Reactor ◽  
Nitrate Removal ◽  
Biofilm Reactor ◽  
Experimental Results ◽  
Heterotrophic Culture ◽  
Concentration Data ◽  
Water And Wastewater Treatment ◽  
Fixed Biofilm

Herein, the progress of nitrate removal by a heterotrophic culture in a batch reactor and continuous-flow fixed-biofilm reactor was examined. Two batch experiments for nitrate reduction with acetate degradation using 250 mL batch reactors with acclimated denitrifying biomass were conducted. The experimental results indicated that the nitrate was completely reduced; however, the acetate remained at a concentration of 280 mg/L from initial nitrate concentration of 100 mg/L. However, the acetate was fully biodegraded by the denitrifying biomass at an initial nitrate concentration of 300 mg/L. To evaluate the biokinetic parameters, the concentration data of nitrate, nitrite, acetate, and denitrifying biomass from the batch kinetic experiments were compared with those of the batch kinetic model system. A continuous-flow fixed-biofilm reactor was used to verify the kinetic biofilm model. The removal efficiency of nitrate in the fixed-biofilm reactor at the steady state was 98.4% accompanied with 90.5% acetate consumption. The experimental results agreed satisfactorily with the model predictions. The modeling and experimental approaches used in this study could be applied in the design of a pilot-scale, or full-scale, fixed-biofilm reactor for nitrate removal in water and wastewater treatment plants.

Innovative process using Fe0/CO2 for the removal of nitrate from groundwater

2005 ◽  
Vol 5 (5) ◽  
pp. 41-48 ◽  
Author(s):  
C. Ruangchainikom ◽  
C.H. Liao ◽  
J. Anotai ◽  
M.T. Lee
Keyword(s):  
Flow Rate ◽  
Nitrate Concentration ◽  
Air Flow ◽  
Nitrate Removal ◽  
Operation Mode ◽  
Nitrate Solution ◽  
Process Efficiency ◽  
Ammonium Concentration ◽  
Air Flow Rate ◽  
Solution Ph

In this study, the Fe0/CO2 process was investigated for removing nitrate from aqueous solution, in terms of process efficiency, process operation mode, and post-treatment of the end product ammonium. The results show that nitrate at 30 mg/L could be removed from solution within 30 min under the conditions of 2 g/L Fe0 and 200 mL/min CO2 flow rate. Additionally, nitrite was not detected in treated solution, whereas ammonium is the predominant nitrogen-containing species. The normalized residual nitrate concentration decreased with increasing nitrate concentration (2.18–24.19 mg N/L). Nitrate removal was inhibited significantly in the presence of humic acid. Comparing operation modes, NO3− reduction efficiency with increasing number of batch operations in Mode 2 (treated solution was emptied and refilled with freshly prepared solution for the next batch treatment, containing the same level of nitrate as the previous batch) is better than that with Mode 1 (treated solution was retained in the reactor and spiked with concentrated nitrate solution to raise nitrate concentration to a level close to the one in the previous batch). However, to guarantee satisfactory nitrate removal in batch operation mode, zero-valent iron supplementation needs to be taken into consideration. For example, the nitrate removal efficiency without Fe0 supplementation is decreasing in the third batch, compared with those with supplements of 0.25 and 1 g/L. According to a preliminary study, the undesired end-product ammonium can be removed from solution by about 95% within 22.5 h with an air flow rate of 500 mL/min and a solution pH around 12; the ammonium concentration decreased from 6.4 to 0.3 mg 12 N/L. Stripping time can be further shortened by increasing air flow rate and using an efficient air diffuser.

Investigations on Phosphate Cements Hardening at Room Temperature

1989 ◽  
Vol 179 ◽  
Author(s):  
Alfred Zurz ◽  
I. Odler ◽  
B. Dettki
Keyword(s):  
Ultimate Strength ◽  
Room Temperature ◽  
Main Reaction ◽  
Main Reaction Product

AbstractPastes prepared from diammonium orthophosphate and calcined magnesia, MgO, exhibit a fast setting and hardening associated with NH3 liberation. Struvite, MgNH4PO4.6H2O, was found to be the main reaction product. Pastes made with NaH2PO4 or Na-polyphosphate exhibit a similar hardening reaction. The hardening reaction may be retarded and the ultimate strength moderately increased by adding appropriate retarders, such as Na2B4O7 10H2O to the system. The quality of the used MgO and its fineness has a significant effect on the rate of the hardening reaction.

scholarly journals Oxidative Destruction of Vulcanized by Changing the Dispersion Composition of Oxidized Vulcanized

2021 ◽  
pp. 207-214
Author(s):  
Milen Dimov ◽  
Zhuldyz Smailova
Keyword(s):  
Nitric Acid ◽  
Ir Spectra ◽  
Structural Changes ◽  
Main Reaction ◽  
Chemical Heterogeneity ◽  
Main Reaction Product ◽  
Oxidative Destruction ◽  
Rubber Component ◽  
Acetone Extracts ◽  
Dispersion Composition

The aim of the present work is to study the processes of oxidative destruction of waste vulcanizates (flakes) with nitric acid. The composition of the particles of the main reaction product was determined (oxidized vulcanized). The IR spectra of hexane and acetone extracts of the oxidized vulcanizates are also presented. It was found that the rubber component of the vulcanizates undergoes deep structural changes leading to the formation of products characterized by chemical heterogeneity

Comparison of denitrification performances using PLA/starch with different mass ratios as carbon source

2015 ◽  
Vol 71 (7) ◽  
pp. 1019-1025 ◽  
Author(s):  
Chuanfu Wu ◽  
Danqi Tang ◽  
Qunhui Wang ◽  
Juan Wang ◽  
Jianguo Liu ◽  
...  
Keyword(s):  
Carbon Source ◽  
Groundwater Remediation ◽  
Nitrate Concentration ◽  
Starch Content ◽  
Nitrate Removal ◽  
Carbon Sources ◽  
National Standard ◽  
Biofilm Carrier ◽  
Carbon Release ◽  
Biological Nitrate Removal

A suitable carbon source is significant for biological nitrate removal from groundwater. In this study, slow-release carbon sources containing polylactic acid (PLA) and starch at 8:2, 7:3, 6:4, 5:5, 4:6, and 3:7 ratios were prepared using a blending and fusing technique. The PLA/starch blend was then used as a solid carbon source for biological nitrate removal. The carbon release rate of PLA/starch was found to increase with increased starch content in leaching experiments. PLA/starch at 5:5 mass ratio was found to have the highest denitrification performance and organic carbon consumption efficiency in semi-continuous denitrification experiments, and was also revealed to support complete denitrification at 50 mg-N/L influent nitrate concentration in continuous experiments. The effluent nitrate concentration was <2 mg NO3–-N/L, which met the national standard (GB 14848-93) for groundwater. Scanning electron microscopy results further showed that the surface roughness of PLA/starch increased with prolonged experimental time, which may be conducive to microorganism attachment. Therefore, PLA/starch was a suitable carbon source and biofilm carrier for groundwater remediation.

scholarly journals Hundred Years of Lactitol: From Hydrogenation to Food Ingredient

2020 ◽  
Author(s):  
Sergio I. Martinez-Monteagudo ◽  
Kaavya Rathnakumar ◽  
Maryam Enteshari ◽  
Collette Nyuydze ◽  
Juan C. Osorio-Arias ◽  
...  
Keyword(s):  
Historical Development ◽  
Main Reaction ◽  
Chewing Gum ◽  
Main Reaction Product ◽  
Food Ingredient ◽  
First Report

The first report on the synthesis of lactitol dates back to the early 1920s. Nearly 100 years have passed since then, and the applications of lactitol have exceeded its original purpose. Currently, lactitol is used in bakery, confectionery, chocolate, desserts, chewing gum, cryoprotectant, delivery agent, and stabilizer in biosensors. Lactitol is the main reaction product derived from the hydrogenation of lactose. This chapter is aimed at providing a succinct overview of the historical development of lactitol, a summary of its synthesis, and an overview of its properties and applications.

THE SOLVOLYSIS OF THE ALPHA- AND BETA-3,4,6-TRI-O-ACETYL-D-GLUCOPYRANOSYL CHLORIDES

1955 ◽  
Vol 33 (1) ◽  
pp. 128-133 ◽  
Author(s):  
R. U. Lemieux ◽  
G. Huber
Keyword(s):  
Acetic Acid ◽  
Double Bond ◽  
Positive Charge ◽  
Main Reaction ◽  
Main Reaction Product ◽  
Double Bond Character ◽  
Ionic Reactions ◽  
Oxygen Bond ◽  
Bond Character ◽  
Anomeric Center

3,4,6-Tri-O-acetyl-β-D-glucopyranosyl chloride was found to undergo solvolysis in acetic acid to form 1,3,4,6-tetra-O-acetyl-α-D-glucopyranose as the main reaction product. The much less reactive anomeric α-chloride also appeared to undergo solvolysis with extensive inversion of the anomeric center. It is submitted that the tendencies for inversion obtained in these ionic reactions are due to the conformations imposed on the intermediate ions through distribution of the positive charge to the ring oxygen and the consequent introduction of double-bond character to the carbon-1 to ring-oxygen bond.

Pseudo-Second-Order Kinetics for the Adsorption of Uranyl Ion onto Peat at Different pH Value

2010 ◽  
Vol 113-116 ◽  
pp. 33-36
Author(s):  
Zhi Rong Liu ◽  
Qin Qin Tao ◽  
Chuan Xi Wen
Keyword(s):  
Contact Time ◽  
Adsorption Process ◽  
Adsorption Equilibrium ◽  
Ph Value ◽  
Second Order ◽  
Uranyl Ions ◽  
Batch Tests ◽  
Effects Of Ph ◽  
Pseudo Second Order

Batch tests were used to investigate the effects of pH and contact time on the adsorption capability of peat. The results indicate that adsorption of uranyl ions on peat increase with increasing pH from 1 to 5. However it takes longer contact time to reach the adsorption equilibrium with increase of pH from 1 to 5. The adsorption process can be described by type 1 of the pseudo-second-order kinetics excellently.

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