Removal Of Chlorine Research Articles

Deterioration of static mechanical properties of RC beams due to bond damage induced by electrochemical rehabilitation

Electrochemical rehabilitation (ER) techniques are very efficient and non-destructive methods to improve the durability of existing concrete structures. However, the induced bond damage between steel bar and concrete will affect the mechanical properties. In order to investigate the effect of ER on the static mechanical properties of concrete structures, three types of tests after electrochemical chloride extraction and bidirectional electromigration were carried out in this study. Based on the desired constitutive models, finite element analysis was then used to verify the effect of bond damage on the static mechanical properties of RC beams. Results showed that the spacing and width of cracks both increased with increasing current density and duration. The yield bearing capacity of beams decreased by 20% when the electrical parameters were 3 A/m2 for 4 weeks and 5 A/m2 for 2 weeks. Careful investigation with experiments, finite element simulations, and theoretical explanation demonstrated that bond damage was the main reason. As a result, a modified flexural stiffness model of concrete beams considering the electrification parameters was established. Combined with data from the relevant literature, the optimal quantity of electric charge for ER balancing chlorine removal efficiency and flexural stiffness was finally determined as 500–1400 Ah/m2.

Gasification of real MSW-derived hydrochar under various atmosphere and temperature

The hydrothermal carbonization could improve the fuel quality of municipal solid waste (MSW), in terms of water content reduction, chlorine removal, and energy densification. The chlorine content plays a significant role in determining whether the derived hydrochar is suitable as a fuel or chemical product. Many works focus on the chlorine behavior and fuel quality of hydrochar. However, few works focus on the gasification characteristics of real MSW-derived hydrochar. In this work, the hydrochar derived from real MSW employing hydrothermal treatment were gasified under various temperatures (600–1000 °C) and atmospheres (Air, CO2/O2 and steam/O2), with gas and tar analyzed by GC and GC–MS, respectively. The results showed that the hydrothermal treatment could remove 90.5 % chlorine of the MSW at an HTC temperature of 220 °C for 30 min. The syngas quality was improved whereas the tar yield was generally reduced with the reaction temperature, independent on the atmosphere. The H2, CO and CH4 yield was increased gradually, while the CO2 yields kept decreasing with the gasification temperature ranging from 600 to 900 °C. The highest H2 yield occured in the steam/O2 gasification, resulting in the highest H2/CO ratio of 4.58 at a gasification temperature of 1000 °C. The tar yield in the air gasification was the maximum, while it was the minimum in the steam/O2 gasification. The carbon conversion rate was increased with the gasification temperature. 900 ℃ was supposed to be a suitable operating window for obtaining gas with high H2 concentration and heating value. All these results indicated that the hydrothermal carbonization (HTC) coupled with gasification was an effective approach to produce hydrogen-rich gas from MSW. And these findings might be helpful for the design and further optimization MSW thermochemical conversion process.

Kinetics of chlorine deposition and removal over promoted silver catalysts during ethylene epoxidation

High partial oxidation selectivity in ethylene oxidation over Ag catalysts is achieved in part via the presence of adsorbed chlorine promoters. Chlorine coverage during ethylene oxidation is maintained by co-feeding organic chlorides in ppm levels and alkane moderators in concentrations of ~0.5 mol%. The relative efficacy of organic chlorides in Cl deposition and of alkanes in Cl removal is typically estimated using empirical correlations. Apparent kinetics of Cl removal were measured by feeding ethyl chloride and propane during ethylene oxidation catalysis over a highly-promoted Ag/α-Al2O3 catalyst and quantifying the rate of chloropropane formation during steady state reaction. Propane oxychlorination forms 1- and 2-chloropropane in a ~1:2 ratio, as expected given the lower bond dissociation enthalpy of methylene than methyl CH bonds in propane, and at total rates on the order of 10-4 mol C3H7Cl (mol Agsurf)-1 s−1. Concurrent ethylene oxidation rates of order 10-1 mol (mol Agsurf)-1 s−1 provide evidence that Cl moderation occurs in a distinct catalytic cycle over promoted Ag catalysts. Cl removal has a supralinear dependence on propane pressure (PC3H8) and an inverse dependence on ethyl chloride pressure (PC2H5Cl) at high PC2H5Cl/PC3H8, while Cl removal is positive order in pressures of both C2H5Cl and C3H8 at low PC2H5Cl/PC3H8, as expected for surfaces that are increasingly covered in Cl as PC2H5Cl/PC3H8 increases. Chloropropane formation rates were positive order in dioxygen pressure for all PC2H5Cl/PC3H8 ratios. Taken together, the kinetics of Cl removal require both rate determining deposition of Cl from an alkyl chloride and kinetically relevant removal of Cl by an alkane. We develop a kinetic model that describes these trends and allows for quantification of rate and equilibrium parameters, and provide evidence for the elementary steps enumerated by measuring a kinetic isotope effect and assessing the fate of alkyl fragments from chloroethane and chloropropane in gas-phase batch reactions. Rate and equilibrium constants regressed from this kinetic model are used to develop an isotherm for Cl coverage as a function of the ratio of organic chloride promoter to alkane moderator pressures. This isotherm quantitatively predicts Cl coverages measured in situ after steady state reactions with feedstreams containing both ethyl chloride-ethane and ethyl chloride-propane mixtures. Measured reaction orders for chloropropane formation with respect to ethylene and carbon dioxide pressure reflect surface ethylene and carbon dioxide coverages that are lower for sites that form chloropropane than for sites that form ethylene oxide, suggesting that site ensembles for Cl deposition and removal vary from those involved in selective oxidation of ethylene.

Development of a Measuring Method for the Determination of Bisulfite and Sulfite in Seawater

AbstractIn conventional reverse osmosis processes for seawater desalination, a disinfection of the process stream with chlorine compounds is carried out for antifouling. After disinfection the reduction agent Na2S2O5 is used for the removal of residual chlorine in a strongly overstoichiometric way in order to protect the membranes from oxidational damages. To save chemicals a controlled dosing of Na2S2O5 based on a reliable concentration measurement is desirable. Therefore, a measuring method for the determination of the sulfur(IV) components bisulfite and sulfite in seawater is developed based on the combination of UV spectroscopy and a PLS regression method. Experimental results as well as the development of the regression model for sulfur species in ultrapure and seawater is described.

Improved chlorine and chromium ion removal from leather processing wastewater by biocharcoal-based capacitive deionization

Red oak biocharcoal, a novel electrode material that is inexpensive and highly conductive, was used for capacitive deionization (CDI) to simultaneously remove Cl− and Cr3+ from leather processing wastewater. The results showed that both the carbonization temperature and time played important roles in reducing the resistivity (ρ) of biocharcoal. Additionally, at 1000 °C and 3 h, the ρ value was reduced from 4.68 to 1.19 Ω·cm after the addition of Fe2O3. KOH impregnation enhanced the desalination capacity of the biocharcoal electrodes by increasing the specific surface area and hydrophilicity. Under the optimal operating parameters (voltage of 1.8 V, flow rate of 10 ml/min and electrode spacing of 2 mm), the KOBC15 electrode exhibited a maximum adsorption capacity of 13.79 mg/g. After 10 cycles of CDI system operation, the removal rates of Cl− and Cr3+ reached 86.7% and 100%, respectively, in simulated leather processing wastewater. Thiswork provides new ideas and methods for the treatment of high-salinity wastewater.

Chlorine removal from MSWI fly ash by thermal treatment: Effects of iron/aluminum additives

The high content of alkali chlorides in municipal solid waste incineration (MSWI) fly ash limit its resource reuse due to the potential environmental risks. In this paper, with superheated steam as the gasifying agent and inducer, chlorides in fly ash were removed by thermal treatment within a moderate temperature range. Thermal treatment experiments were performed under different conditions: temperature (500–800°C), steam addition (mass ratio of steam to fly ash = 0.25–1) and residence time (0.5–3 hr). Iron and aluminum powders were added to fly ash to improve the chlorine removal efficiency. Water-soluble chlorides included NaCl and KCl, and insoluble chlorides mainly included Ca(OH)Cl. The heating process with the addition of water steam was more efficient than that without steam in terms of the removal performance of water-soluble chlorides. The removal efficiency of soluble chlorides reached 75.25% for a mass ratio of 1:1 after 1-hr thermal treatment at 700°C. When the residence time was increased above 1 hr, the total dechlorination efficiency was not increased dramatically. Moreover, adding iron and aluminum powder into the fly ash improved the removal of water-insoluble chlorides, and the total dechlorination efficiency was increased by 11.41%–16.64%.

Molecular characteristics governing chlorine deposition and removal on promoted Ag catalysts during ethylene epoxidation

The selectivity of Ag ethylene epoxidation catalysts correlates with surface coverage of the promoter chlorine. Cl coverage, in turn, is a function of co-fed organic chloride and alkane moderator pressures. Organic molecules can be classified based on their deprotonation enthalpy, as those that are inert, those capable of selective oxidation, or those that act as gas-phase acids. The influence of alkane moderator and alkyl chloride promoter identities on Cl coverage was assessed by titration of Cl by ethane in a recirculating gas-phase batch reactor immediately following steady-state reactions with various alkane and alkyl chlorides included in ethylene oxidation feedstreams. The faculty of organic molecules for Cl removal correlates with the weakest CH bond dissociation enthalpy, such that molecules with CH bonds susceptible to homolysis remove Cl more effectively than those with stronger CH bonds. Cl deposition likely occurs via heterolytic cleavage of CCl bonds in alkyl chlorides, such that molecules with weak CCl bonds deposit multiple monolayers of Cl. Cl coverage affects ethylene epoxidation rates identically regardless of the organic chloride or the aliphatic hydrocarbon employed, demonstrating that these molecules only impact catalysis by moderating Cl coverage. These findings implicate the concurrent prevalence of homolytic and heterolytic pathways during ethylene epoxidation on promoted Ag/α-Al2O3 catalysts and provide context to examine additional roles of surface oxygen beyond involvement in oxidation pathways.

Cisplatin as a Potential Platinum Focused Electron Beam Induced Deposition Precursor: NH3 Ligands Enhance the Electron-Induced Removal of Chlorine

Nanostructures fabricated by focused electron beam induced deposition (FEBID) often have low deposit purities that can be traced back to incomplete precursor decomposition. Among others, removal of...

Aminobacter sp. MSH1 Mineralizes the Groundwater Micropollutant 2,6-Dichlorobenzamide through a Unique Chlorobenzoate Catabolic Pathway.

2,6-Dichlorobenzamide (BAM) is a major groundwater micropollutant posing problems for drinking water treatment plants (DWTPs) that depend on groundwater intake. Aminobacter sp. MSH1 uses BAM as the sole source of carbon, nitrogen, and energy and is considered a prime biocatalyst for groundwater bioremediation in DWTPs. Its use in bioremediation requires knowledge of its BAM-catabolic pathway, which is currently restricted to the amidase BbdA converting BAM into 2,6-dichlorobenzoic acid (2,6-DCBA) and the monooxygenase BbdD transforming 2,6-DCBA into 2,6-dichloro-3-hydroxybenzoic acid. Here, we show that the 2,6-DCBA catabolic pathway is unique and differs substantially from catabolism of other chlorobenzoates. BbdD catalyzes a second hydroxylation, forming 2,6-dichloro-3,5-dihydroxybenzoic acid. Subsequently, glutathione-dependent dehalogenases (BbdI and BbdE) catalyze the thiolytic removal of the first chlorine. The remaining chlorine is then removed hydrolytically by a dehalogenase of the α/β hydrolase superfamily (BbdC). BbdC is the first enzyme in that superfamily associated with dehalogenation of chlorinated aromatics and appears to represent a new subtype within the α/β hydrolase dehalogenases. The activity of BbdC yields a unique trihydroxylated aromatic intermediate for ring cleavage that is performed by an extradiol dioxygenase (BbdF) producing 2,4,6-trioxoheptanedioic acid, which is likely converted to Krebs cycle intermediates by BbdG.

Removal of Chlorine from Municipal Solid Waste Fly Ash by using Acid and Alkaline Solution

Removal of Chlorine from Municipal Solid Waste Fly Ash by using Acid and Alkaline Solution

Exploring the lignolytic potential of a new laccase producing strain Kocuria sp. PBS-1 and its application in bamboo pulp bleaching

The pulp and paper industry is one of the largest polluting industries in the world employing chlorine-based bleaching processes. The hazardous impact on the environment can be mitigated by either removal of chlorine or minimizing its use by developing alternative bleaching methods. This study was undertaken to explore the applicability of a new laccase isolated from Kocuria sp. PBS-1 for bamboo pulp bleaching. The enzyme was optimally active at 50 °C and pH 7 and the Km, Vmax and Kcat were 39.45 ± 5.47 mM, 407.40 ± 4.9 μmol min−1 and 124.5 s−1 respectively. Further, the t1/2 was found to be 13 h at 30 °C. This laccase produced a significant increase in the ISO brightness to 80.03 ± 1.68% after LMPZ (Laccase, Mediator, Peroxide and Ozone) bleaching. A significant reduction in the kappa number was recorded for L, LM, LMP and LMPZ treated pulp samples. The FTIR peak at ~1118 cm−1 attributed to lignin present in spectra of the control pulp sample was not observed in spectra of the treated pulps. A new band at 1162 cm−1 in treated pulps indicated degradation of syringyl groups along with an increase in the total crystallinity index, empirical crystallinity index and apparent crystallite size of the cellulose. XRD data of treated pulp samples revealed an increase in the cellulose crystallinity index as per A1430/897 ratio. The SEM of treated pulps showed a change in morphology of pulps like the appearance of cracks, crevices, grooves and peeling of fibrils due to lignolytic activity. These findings may provide leads for the development of new cleaner and alternative methods for pulp bleaching.

Conversion of chlorine/nitrogen species and formation of nitrogenous disinfection by-products in the pre-chlorination/post-UV treatment of sulfamethoxazole

Pre-chlorination and UV disinfection are two common processes in drinking water treatment plants. Sulfamethoxazole (SMX), an antibiotic widely detected in source water, was selected as a precursor to study the conversion of chlorine/nitrogen species and DBP formation in pre-chlorination/post-UV process. The combined chlorine (mainly organic chloramines) produced in pre-chlorination of SMX can self-degrade and release free chlorine back again as pre-chlorination time goes on. With free chlorine dose increasing, the self-degradation rate of combined chlorine increased obviously. But the combined chlorine stopped self-degrading and remained stable around 1 mg-Cl2/L after adding 0.30 mM chlorine for 30 min. Post-UV treatment after pre-chlorination can enhance the degradation and achieve a complete removal of combined chlorine (including organic chloramines). Deamination occurred during pre-chlorination/post-UV process and deamination amount (-NH2) per SMX concentration was 0.19 M/M. Radicals in this process had no obvious influence on chlorine/nitrogen species conversion. Direct chlorination of SMX had the lowest DBP formation potentials while the application of pre-chlorination and UV enhanced them. Compared with UV treatment only, dichloroacetonitrile formation potential of SMX reduced by 1.58 × 10−3 mol/mol-SMX (17.37 μg/l) after pre-chlorination/post-UV treatment. During pre-chlorination/post-UV/final-chlorination treatment of SMX, Br− and natural organic matter can enhance DBP formation and toxicity-weighted values. Acid conditions showed a very high DBP risk, while alkaline conditions could cut this risk obviously, especially for the toxicity-weighted values of these DBPs.

Determination of the specifications and quantities of pollutants present in water discharged from oil plant and their treatment methods

Water pollution is an important environmental problem at present and has a direct impact on the lives of individuals, families and society. Water pollution is produced from several industrial processes. One of these processes is the making vegetable oils, where the polluted water is produced by the refining of vegetable oils, there is also contaminated water resulting from the process of bleaching vegetable oil, there is another pollution of the water produced by the process of removing the smell of vegetable oil and there is also pollution of water resulting from heat exchangers where the use of cold or hot water. In this research, were used natural and chemical materials, different concentrations and different weights to reach the best results. The treatment process is done in two phases, the first by adding the following substances (alum, calcium hydroxide alkaline and concentrated sulfuric acid) in different quantities to the polluted water and then leaving a period of time after it is separated from the sediment method. After treatment, (pH), residual Chlorine (cl), bioactive oxygen (BOD5), Oils and Greases (O & G) and phosphate (PO4) are measured. The second phase of the water is adsorbed by activated carbon adsorption for the removal of chlorine from the water (a class of halogens) which is strongly adsorbed by activated carbon. First, (pH), (BOD5), (O & G), and phosphate (PO4) have been controlled within the allowable limits, while the residual chlorine (cl) is much higher than the maximum limits, where it was treated in the second stage, up to the surveyed boundary before it was put into the river water.

Mechanical activation of fly ash from MSWI for utilization in cementitious materials

In the present study, the physicochemical characteristics of municipal solid waste incineration fly ashes (FA) from circulating fluidized bed (CFB) or grate furnaces are studied in detail. It is identified that the CFB FA, containing high amount of Si and Al, has better potential and properties for utilization than the grate FA, which is much richer in chlorides. Mechanical activation (MA) allows amending the properties of CFB FA, thus preparing for its subsequent utilization in cementitious materials. Compared to simple water washing, MA treatment of CFB FA further reduces the residual amount of chlorine in fly ash from 0.72 to 0.33 wt%, giving the possibility of doubling the capacity of cement kiln for fly ash disposal. The improvement in chlorine removal relates to the conversion of FA compounds from a crystalline to an amorphous state, increasing the solubility of sparingly soluble chlorides. During the curing of mortars, traces of aluminum or other nonferrous metals in CFB FA are oxidized, liberating lots of hydrogen gas; this would cause expansion problems and significantly reduce the flexural and compressive strength. MA treatment of CFB FA solves such expansion problems by exhausting these reactions in advance, respectively enhancing flexural and compressive strength from 5.7 and 35.3 MPa to 9.1 and 56.9 MPa, which is comparable to the performance of Ordinary Portland Cement. Finally, an innovative pre-treatment technique for CFB FA, combining wet ball milling and counter-current two-stage water washing, is proposed for facilitating its recycling.

Numerical analysis on efficiency of electrochemical chloride extraction of one side anode in concrete

Electrochemical Chloride Extraction (ECE) is one of the key ways to enhance the durability of concrete structure which suffered or are suffering from chloride attack. To deeply understand the influence of various factors on chlorine removal efficiency, this paper presents a numerical study to characterize transport and distribution of each ion during ECE. A plain concrete specimen was used as an example to investigate the influence of various factors on the efficiency of ECE of one side anode. These factors were: time, current density, ratio of cover thickness and side length, initial chloride ion concentration, and ratio of cross-sectional area of reinforcement to cross-sectional area of specimen. In addition, the quantitative relationship model between these factors and total electrochemical desalination efficiency are also proposed. Good agreement between the present the quantitative relationship model of total desalination efficiency and the FEM solution illustrates reliability and accuracy of the proposed relationship model.

Study on the variation of electric potential in reinforced concrete members during accelerated corrosion and electrochemical chloride extraction process

This paper mainly studies the corrosion potential and current of reinforced concrete beams during accelerated corrosion and electrochemical chloride extraction. The results show that the corrosion potential and current of concrete beams increase with the corrosion time. In the process of electrochemical chloride extraction, the corrosion potential and current of concrete beams decrease with the prolongation of chlorine removal time. Electrochemical chloride extraction can effectively reduce the corrosion rate of reinforced concrete components and reduce the corrosion risk of steel bars.

Treatment of organic wastewater containing nitrogen and chlorine by combinatorial electrochemical system: Taking biologically treated landfill leachate treatment as an example

This study presents a combinatorial electrochemical system (CES) for the treatment of refractory organic wastewater containing nitrogen and chloride ion. The CES was composed of iron anode reactor (IAR), Ti/RuO2 anode reactor (TAR) and available chlorine removal reactor (CRR). Biologically treated landfill leachate (BTLL) was selected as the treatment object to evaluate the performance of CES. The results showed that CES could simultaneously remove chemical oxygen demand (COD) and total nitrogen (TN) by 94.6% and 98.3%, respectively. Reduction of nitrite-N by cathode in IAR and oxidation of ammonium-N by available chlorine in TAR were the major pathways for TN removal. Fluorescence spectroscopy and parallel factor analysis (PARAFAC) showed that the main organic components in BTLL were humic-like substances and soluble microbial degradation products. These substances were removed by CES and the remaining organics were some hydrocarbons and carboxylic acids. The available chlorine was rapidly reduced into chloride ion by IAR precipitates, thus decreasing the cytotoxicity. In addition, the formation of stable Fe3+ crystals was promoted by the oxidation of available chlorine in CRR, which increased the density of the precipitates and reduced their volume. Therefore, the CES is a promising solution for the treatment of refractory organic wastewater containing nitrogen and chlorine ion.

КВАНТОВО-ХИМИЧЕСКОЕ ИЗУЧЕНИЕ ВЗАИМОДЕЙСТВИЯ 1,2-ЭТАНДИТИОЛА С 1,3-ДИХЛОРБУТЕНОМ-2 В СИСТЕМЕ ГИДРАЗИНГИДРАТКОН

According to the results of quantum-chemical studies in the framework of the theory
 of functional density of the electron density using the B3LYP / 6-311 ++ G (d, p) method, a theoretical
 mechanism of the reaction of 1,3-dichlorobutene-2 with 1,2-ethanedithiol in the hydrazine hydrateKOH system has been proposed. It has been shown that this interaction proceeds sequentially in several stages, including the nucleophilic substitution of the chlorine atom of the sp3 hybridized carbon
 atom to the sulfur atom with the formation of a monosubstitution product (SN2 mechanism), which under the action of alkali undergoes deprotonation of the methylene group to form an allyl carbanion .
 The resulting carbanion, due to the migration of hydrogen and the removal of chlorine, is converted
 into an allene derivative, which as a result of the intramolecular nucleophilic attack of the free
 thiolate group on the central carbon atom of the allene fragment closes into the final dithian cycle.

Highly efficient catalytic combustion of o-dichlorobenzene over three-dimensional ordered mesoporous cerium manganese bimetallic oxides: A new concept of chlorine removal mechanism

A series of three-dimensional (3D) ordered mesoporous cerium manganese bimetallic oxide catalysts (marked as CeMnX, X refers to the molar percentage of Mn relative to total molar quantity of Ce and Mn) were prepared using KIT-6 as hard template. The highly ordered mesoporous structural CeMn30 had a large specific surface area where the formation of CeMnOx solid solution led to a great enrichment of Ce3+, oxygen vacancies, active oxygen species and acidic sites, which promoted the catalytic activity of CeMn30. CeMn30 exhibited a good stability which activity did not decrease after five cycles of activity test and o-dichlorobenzene conversion kept over 95% at 370 ºC for more than 1600 min. The deactivation of CeMn30 used in stability test mainly caused by adsorption of inorganic chlorine species which are hardly to be removed completely by simple calcination process in air condition. CeMn30 also had a good water resistance and high airspeed applicability. In this work, the selectivity of HCl and CO2 can reach 100% at 347 °C and the chlorine dissociated from o-dichlorobenzene as a form of HCl without any Cl2 produced which is an inevitable product of Deacon Reaction. Thus, the mechanism of chlorine removal from o-dichlorobenzene molecule is different from general cognition (Deacon Reaction). Based on this, we introduced a new and reasonable reaction mechanism in conjunction with a series of characterization analysis.

Chemical kinetics and particle size effects of activated carbon for free chlorine removal from drinking water

Abstract Activated carbon is an economic material to grab free chlorine in drinking water to reduce potential health risks. In this research, chemical kinetic reaction of the activated carbon for free chlorine removal was studied, which exhibited the first order kinetic reaction performance. A relationship between the rate of chlorinated water flowing through the activated carbon, and the free chlorine (ClO−) concentrations before and after the reduction by activated carbon was obtained. The logarithm of the free chlorine concentration (lnC) was linearly related to the reciprocal of the volume flow rate (1/v). The slope was dependant on the kinetic constant of the activated carbon dechlorination reaction. This research is beneficial for the scientists and engineers to study the mechanism of the chemical kinetic reaction of the free chlorine removal by activated carbon and design activated carbon-loaded water purification reactors.