Chlorination Rate Research Articles

Preparation of TiCl4 from Ilmenite Concentrates via Carbothermal Reduction and Boiling Chlorination for Different Carbon Proportions.

Low-temperature boiling chlorination is the most common approach used to achieve a clean preparation of TiCl4 from ilmenite concentrates with high contents of calcium and magnesium impurities. However, this process did not systematically investigate the impact of the Ti/C ratio of the raw materials on the chlorination efficiency of Ti, Ca, and Mg elements. Thus, the influence of the carbon allocation proportion on the carbothermal reduction and boiling chlorination process of ilmenite concentrates with high contents of calcium and magnesium impurities was investigated in this study. The results show that the reduction products of ilmenite concentrates are mainly Mg-rich Ti2O3 impurities at a low carbon proportion. However, with increasing carbon proportion, Ti2O3 is gradually reduced to TiC x O1-x , and Mg2TiO4 appears. The Ti2O3 content in the acid-insoluble matter of the reduced products decreases after acid washing, while the TiC x O1-x content increases with increasing carbon allocation proportion. With increasing carbon proportion, the chlorination rate of the acid-insoluble matter increases, and the corresponding chlorination rates of titanium, magnesium, and calcium also increase. The residual carbon produced by acid-insoluble chlorination at high carbon proportions exacerbates the chlorination of Mg and Ca impurities.

Exploring chlorination as a removal process for antiretroviral drugs (Nevirapine and Efavirenz) from water: Effect of operational parameters, kinetics, and trihalomethane formation

This study investigates the removal of antiretroviral drugs (ARVs), Nevirapine (NVP) and Efavirenz (EFV), from drinking water through chlorination, focusing on the influence of pH, temperature, chlorine concentration, and ARV initial concentration on the degradation kinetics and trihalomethane (THM) formation. At 25 °C and an initial concentration of 100 μg/L, the degradation trends for both ARVs were examined across varying pH levels. EFV exhibited greater pH sensitivity, with removal increasing from 37 % at pH 5.5 to 68 % at pH 8, while NVP removal increased only from 40 % at pH 5.5 to 48 % at pH 8. Temperature also played an essential role, as the removal of both ARVs increased with rising temperature, indicating an endothermic reaction. Higher chlorine concentrations resulted in increased removal, >90 % at 5 mg/L for both ARVs. Kinetic analysis revealed second-order behaviour, with higher rate constants observed at pH 5.5–7 for NVP and pH 7–8 for EFV. The intrinsic chlorination rate constants for both ARVs were estimated. The calculated half-lives indicated slow removal. The study also assessed contact time for NVP and EFV in a plug-flow reactor (PFR) and continuous stirred tank reactor model (CSTR). Also considering hydraulic residence time (HRT) rather than reaction time to assess the average amount of time that the ARVs spent in the selected reactors. The HRT for a CSTR was lower than the PFR, and the estimated HRT for a CSTR was a feasible value. The minimum HRT came out to 1.56 h (pH 7.5 and a temperature of 25 °C) for NVP and 1.07 h (pH 7 and a temperature of 25 °C) for EFV. Finally, THM formation was observed, with chloroform, dibromochloromethane and bromoform detected. Among the three THMs, the most significant change occurred between 4 and 6 h, with chloroform levels increasing from 31.59 μg/L to 63.49 μg/L. This study underscores the influence of operational parameters on ARV removal via chlorination. Highlighting pH sensitivity, temperature control, precise chlorine dosage, and environmental concerns such as trihalomethane formation ensures effective disinfection while minimizing negative impacts on both water quality and the environment. Emphasizing the importance of a comprehensive approach to ARV removal in water treatment processes is a proactive measure that integrates considerations of environmental impact, public health, regulatory compliance, and long-term sustainability into the design and operation of water treatment facilities.

Transformation of brackish water Reverse Osmosis membranes to nanofiltration & ultrafiltration membranes by NaOCl treatment: Kinetic and characterization studies

Thin Film Composite (TFC) Reverse Osmosis (RO) membranes used in desalination, reach their End-of-Life (EoL) due to fouling and chemical degradation and pose disposal problem. Their lifetime can be increased by converting them into Ultrafiltration (UF) or Nanofiltration (NF) membranes. The present work demonstrates a systematic methodology in terms of ‘ppm-h/ppm∙h exposure’ to chemically convert brackish water RO membranes into NF and subsequently into UF membranes using sodium hypochlorite (NaOCl). Post-performance studies of pure water flux, monovalent and bivalent salt rejection are carried at each treatment level. RO membrane has transformed into NF at 3000–3 ppm-h, 2000–6 ppm-h, 3000–6 ppm-h and in to UF membrane beyond 10000–3 ppm-h. Gradual changes in physicochemical properties of membrane during conversion are ascertained from Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Photoelectron Spectroscopy (XPS), contact angle, zeta potential etc. The rate of chlorination of polyamide is derived using XPS elemental data from initial stages of NaOCl exposure, and rate of hydrolysis from the membrane resistance, and pH. The overall rate equation is combination of both. The membrane thickness calculated from the kinetics match with experimental data. This study gives account of depolymerization of polyamide upon NaOCl exposure (ppm-h) which can be useful in chemical recycling/treatment of EoL membranes on a plant scale.

Preparation of TiCl4 from panzhihua ilmenite concentrate by boiling chlorination

Titanium tetrachloride (TiCl4) is an important raw material for preparing metallic Ti and TiO2. At present, TiCl4 is mainly produced through boiling chlorination and molten salt chlorination. However, the quality of the titanium slag (or rutile) is significantly influenced by the preparation method. The content of Ca and Mg impurities in Panzhihua ilmenite is high, and the titanium slag after smelting is suitable for the production of TiCl4 via molten salt chlorination. However, chlorinated waste salt pollutes the environment, which should be avoided to meet sustainability goals. Herein, a novel process for preparing TiCl4 from Panzhihua ilmenite involving boiling chlorination is proposed. The carbothermal reduction of the ilmenite concentrate, acid leaching separation of the reduced products, and boiling chlorination process were investigated via X-ray diffraction, mineral dissociation analysis, scanning electron microscopy, and energy-dispersive spectroscopy. The reduced products, which are rich in titanium oxycarbide, Ti2O3 and iron, were prepared after reacting at 1550 °C for 3 h. The Fe content in the reduced products was reduced from 37.85 to 3.0 wt % after leaching with 1–5 wt. % hydrochloric acid. The obtained acid insoluble substances were chlorinated at 500 °C for 25 min to prepare TiCl4, resulting in a chlorination rate of 77.4%. The chlorination residue is rich in unchlorinated rutile, which can be recovered by repeating the boiling chlorination process. Therefore, the environmentally friendly boiling chlorination of Panzhihua ilmenite can be used to prepare TiCl4 avoiding the waste of chlorinated salt.

Effect of Titanium tetrachloride on the rate of chlorination of Yarega quartz-leucoxene concentrate

This paper considers the results of a study that looked at chlorination of the Yarega quartz-leucoxene concentrate in an ebullated bed reactor (EBR) that feeds titanium tetrachloride vapours and their mixture with chlorine to the reaction mass. The experiments were conducted at a temperature of 850 oC and an incoming gas flow rate of 1,600 ml/min. 250–315 μm concentrate grains mixed with 160–250 μm calcined petroleum coke (the carbon to titanium dioxide molecular ratio was 5) were subjected to chlorination. The reaction products were analyzed with the help of inductively coupled plasma optical emission spectroscopy. It was found that, in the absence of chlorine, titanium tetrachloride only interacts with iron oxides. Feeding a mixture of titanium tetrachloride vapours and chlorine into the reactor leads to an intensified chlorination of the main concentrate components, including TiO2, SiO2, Al2O3 and Fe2O3. The TiO2 chlorination rate rises proportionally to the square root of the partial pressure of titanium tetrachloride in the gas-vapour mixture. The risen rate can be attributed to a higher concentration of active chlorine atoms, which in this case occur on carbon surface not only due to dissociation of molecular chlorine but also as a result of decomposition of titanium tetrachloride. A higher partial pressure of chlorine atoms leads to higher rates of reaction between the chlorine atoms and the concentrate components. According to the proposed reaction mechanism, the TiO2 chlorination rate is proportional to the square root of the product of the partial pressure of TiCl4 and the carbon grains surface area. The excessive chlorine does not impact the chlorination rate. It would be advisable to take into account the discovered ability of TiCl4 to intensify the titanium dioxide chlorination process when designing a chlorine feeding unit in the ebullated bed reactor. Feeding chlorine mixed with titanium tetrachloride vapours into the lower section of the reactor can help enhance the process performance while avoiding using too much chlorine.The work weas carried out under financial support of the Russian Foundation for Basic Research grant, the project No. 18-29-24187mk.

Carbochlorination mechanism of low-grade titanium slag: Ab initio molecular dynamic simulation

The carbochlorination process of low-grade titanium slag and the formation mechanism of intermediate products are difficult to completely explain at the microscopic level. According to the phase and chemical composition of low-grade titanium slag, MgTi4FeO10 was used to study the carbochlorination mechanism. The effects of the Fe and Mg in the complex oxide on the chlorination rate and the important roles of C were elucidated by ab initio molecular dynamic (AIMD) simulation. The difference in the adsorption behavior of the intermediate product COCl2 on MgTi4FeO10(011) and TiO2(110) was also analyzed. Thermodynamics, AIMD simulation, the adsorption configuration of COCl2 and experimental results indicated that the presence of rutile is the bottleneck restricting the high efficiency chlorination of low-grade titanium slag. This study is expected to provide ideas for the further improvement of the chlorination efficiency and rate of low-grade titanium slag.

Novel insight into composite packing of copper modified adsorbents for synergistically capturing H2S&HCl in low-temperature anaerobic environment

• Simultaneous removal of HCl&H 2 S in low-temperature anaerobic condition was designed. • Mixed packing adsorbents achieved the optimal and synchronous capture of HCl&H 2 S. • HCl led to the formation of flower-like nanosheets and reduced sulfate production. • The effects of adsorption parameters on simultaneous HCl@H 2 S removal were studied. Trace amount of acid gas components in industrial gas is the main cause of air pollution, which greatly restricts the sustainable utilization of industrial coal gas resources. However, there is still a blank in the research of selective deep removal of H 2 S&HCl under low temperature anaerobic conditions. In this work, simultaneous desulfurization and dechlorination performance were investigated using the combined two copper based porous adsorbents under low-temperature anaerobic conditions in a traditional fixed bed reactor. The breakthrough curves of simultaneous desulfurization and dechlorination over single or composite adsorbents were respectively explored, and the results showed that the composite packing indicated the optimal adsorption efficiencies. The maximum chlorination rate and sulfurization rate of the adsorbents Cu@Na and Cu@ASC were 0.787 and 0.6, respectively. Among the adsorption process, the presence of HCl leads to the distribution of copper sulfide products in the form of flower-like nanosheets and partly inhibited the formation of sulfate. In addition, the effects of different adsorption conditions such as reaction temperature, mass ratio, humidity and CO 2 concentration on simultaneous desulfurization and dechlorination were also studied. The experimental results illustrate that the composite packing of these two porous materials has the opportunity to achieve the selective separation of multi-component trace acid gas from low temperature industrial gas.

Chlorination of soil organic matter: The role of humus type and land use

The levels of natural organic chlorine (Clorg) typically exceed levels of chloride in most soils and is therefore clearly of high importance for continental chlorine cycling. The high spatial variability raises questions on soil organic matter (SOM) chlorination rates among topsoils with different types of organic matter. We measured Clorg formation rates along depth profiles in six French temperate soils with similar Cl deposition using 36Cl tracer experiments. Three forest sites with different humus types and soils from grassland and arable land were studied. The highest specific chlorination rates (fraction of chlorine pool transformed to Clorg per time unit) among the forest soils were found in the humus layers. Comparing the forest sites, specific chlorination was highest in mull-type humus, characterized by high microbial activity and fast degradation of the organic matter. Considering non-humus soil layers, grassland and forest soils had similar specific chlorination rates in the uppermost layer (0–10 cm below humus layer). Below this depth the specific chlorination rate decreased slightly in forests, and drastically in the grassland soil. The agricultural soil exhibited the lowest specific chlorination rates, similar along the depth profile. Across all sites, specific chlorination rates were correlated with soil moisture and in combination with the patterns on organic matter types, the results suggest an extensive Cl cycling where humus types and soil moisture provided best conditions for microbial activity. Clorg accumulation and theoretical residence times were not clearly linked to chlorination rates. This indicates intensive Cl cycling between organic and inorganic forms in forest humus layers, regulated by humic matter reactivity and soil moisture, while long-term Clorg accumulation seems more linked with overall deep soil organic carbon stabilization. Thus, humus types and factors affecting soil carbon storage, including vegetation land use, could be used as indicators of potential Clorg formation and accumulation in soils.

Hot corrosion behavior of refractory high entropy alloys in molten chloride salt for concentrating solar power systems

Refractory high entropy alloys have recently attracted widespread attention due to their outstanding mechanical properties at elevated temperatures, making them appealing for concentrating solar power and nuclear energy applications. However, their molten salt corrosion behavior has not been reported, which is critical in evaluating their application merit. Here, the corrosion behavior of two recently developed refractory high entropy alloys, namely TaTiVWZr and HfTaTiVZr, was studied in molten 33NaCl–22KCl–45MgCl2 (wt. %) eutectic salt at 450 °C and 650 °C, using potentiodynamic polarization technique. The results were compared with benchmark alloys, namely 304 stainless steel (SS304) and Inconel 718 (IN718). TaTiVWZr refractory high entropy alloy exhibited an order of magnitude lower corrosion current density (Icorr = 0.7× 10-3 A cm-2) compared to SS304 (Icorr = 9.2 × 10-3 A cm-2) at the higher temperature of 650 °C. The corrosion rate of all the alloys increased with increase in temperature from 450 °C to 650 °C with the exception of TaTiVWZr. The TaTiVWZr alloy showed a corrosion rate of ~ 5 mm/year at 650 °C compared to ~ 110 mm/year for SS304. HfTaTiVZr and IN718 showed comparable corrosion rates in the range of ~ 40 mm/year at 650 °C. The high corrosion resistance of the two refractory high entropy alloys was attributed to a combination of three factors: (i) slower chlorination rate of refractory elements in the molten chloride salt environment driven by thermodynamics, (ii) formation of stable Ta–V and Ta–V–W based complex oxides on their surface, and (iii) Ti/TiCl2 and Zr/ZrCl2 redox couple formation which retarded the depletion of refractory elements. In contrast, the Cr-, Fe-, and Ni-based surface passivation oxides for SS304 and IN718 were less protective in the molten salt environment, particularly at the higher temperature of 650 °C.

PhICl2 is activated by chloride ions.

A study on the potential activating role of pyridine in the electrophilic chlorination of anisole by PhICl2 has led to the discovery that soluble sources of chloride ions activate PhICl2 in the reaction at catalytic loadings, greatly increasing the rate of chlorination. It is further shown that presence of chloride increases the rate of decomposition of PhICl2 into PhI and Cl2. The specific mechanism by which chloride induces electrophilic chlorination and decomposition of PhICl2 remains an open question.

Experimental evidence that halogen bonding catalyzes the heterogeneous chlorination of alkenes in submicron liquid droplets.

A key challenge in predicting the multiphase chemistry of aerosols and droplets is connecting reaction probabilities, observed in an experiment, with the kinetics of individual elementary steps that control the chemistry that occurs across a gas/liquid interface. Here we report evidence that oxygenated molecules accelerate the heterogeneous reaction rate of chlorine gas with an alkene (squalene, Sqe) in submicron droplets. The effective reaction probability for Sqe is sensitive to both the aerosol composition and gas phase environment. In binary aerosol mixtures with 2-decyl-1-tetradecanol, linoleic acid and oleic acid, Sqe reacts 12–23× more rapidly than in a pure aerosol. In contrast, the reactivity of Sqe is diminished by 3× when mixed with an alkane. Additionally, small oxygenated molecules in the gas phase (water, ethanol, acetone, and acetic acid) accelerate (up to 10×) the heterogeneous chlorination rate of Sqe. The overall reaction mechanism is not altered by the presence of these aerosol and gas phase additives, suggesting instead that they act as catalysts. Since the largest rate acceleration occurs in the presence of oxygenated molecules, we conclude that halogen bonding enhances reactivity by slowing the desorption kinetics of Cl2 at the interface, in a way that is analogous to decreasing temperature. These results highlight the importance of relatively weak interactions in controlling the speed of multiphase reactions important for atmospheric and indoor environments.

Cleaner and effective extraction and separation of iron from vanadium slag by carbothermic reduction-chlorination-molten salt electrolysis

In this work, a cleaner and effective method for selective extraction of iron from vanadium slag was developed, including carbothermal reduction of iron from vanadium slag, chlorination of reduced slag, and electrolysis of chlorinated slag. In the reduction process of vanadium slag, the influence of temperature and C/slag mass ratio on the reduction percentage of FeO, V2O3, Cr2O3, MnO and TiO2 were also investigated by isothermal method. Under the optimal process conditions, the reduction percentage of FeO, V2O3, Cr2O3, MnO, and TiO2 in vanadium slag is 38.6% at 1100 °C for 135 min and the metallization ratio of Fe is 85.4%. After carbothermal reduction of vanadium slag, the unreduced iron oxide is chlorinated to obtain FeCl2 and the chlorination rate of unreduced iron oxide is 85.6% at 900 °C for 4 h. In the electrolysis process, the selective electrolysis of iron ions is achieved by controlling the potential of electrolysis to obtain metal Fe (95 wt%) with 0.9 wt% of V and 0.25 wt% of Cr at 1.6 V. This is a new and cleaner method for the selective removal of Fe from vanadium slag. This novel and cleaner process has potential application for processing materials with high Fe content and low content of other valuable elements (Ti, Cr, V, Nb, etc) such as rare earth iron ore, vanadium titanomagnetite ore, and chromite ore.

Generation of hydroxyl radical during chlorination of hydroxyphenols and natural organic matter extracts

The generation of hydroxyl radicals (•OH) during the chlorination of air saturated solutions of different hydroxyphenols (hydroquinone, resorcinol, catechol, gallic and tannic acids) at pH 7 has been determined by the formation of phenol (in presence of benzene in excess) or 2-hydroxyterephthalic acid (in presence of terephthalic acid). Formation of •OH was only detected during the chlorination of o- or p-hydroxyphenols, compounds that react with chlorine by electron transfer forming the corresponding semiquinones/quinones. In aerated solutions, oxygen is reduced by the semiquinone to the superoxide radical, O2•−, which reacts with HOCl to •OH. Compared to the studied o-hydroxyphenols, the lower reactivity of hydroquinone towards chlorine favours the reaction between chlorine and O2•−, and its •OH formation potential is ∼50 times higher. The extent of •OH generated increased with the concentration of the hydroxyphenol and chlorine, but the •OH yield (moles formed per mole of hydroxyphenol eliminated), decreased due to the formation of the quinone, that acts as O2•− scavenger. The yield was almost not affected by the pH (6 ≤ pH ≤ 7.5), whereas a strong impact of dissolved O2 was observed. The •OH production was null in absence of O2 and 2.5–3 times higher at oxygen saturated conditions compared to air-saturated. Contrary to chlorination, during bromination of hydroquinone •OH was not formed, which can be attributable to a much faster consumption of the oxidant, with no chance for O2•− to react with bromine.Formation of •OH during the chlorination of different NOM extracts (SRHA, SRFA, PLFA and Nordic Lake NOM) and water from Lake Greifensee (Switzerland) was also studied using terephthalic acid as •OH scavenger. For SRHA, SRFA and Nordic Lake NOM (all of allochthonous origin and presenting high electron-donating capacity, EDC), •OH yields expressed as moles formed per mole of DOC0 (%), were between 1.1 and 2.0, similar to that of hydroquinone (∼1.5). For PLFA and Lake Greifensee water (autochthonous, lower EDC) much lower •OH yields were observed (0.1–0.3). Both chlorination rate and EDC, the later favouring the formation/stabilization of O2•−, seem to be key factors involved in •OH generation during the chlorination of NOM. A mechanism for these findings is proposed based on kinetic simulations of hydroquinone chlorination at pH 7.

Kinetic Study of Selective Chlorination of Iron in Ilmenite Ore

The selective chlorination of ilmenite with coke and chlorine gas was conducted in the fixed bed reactor and effects of coke content and reaction temperature on reaction rate were investigated. In particular, the chlorination rate of iron in ilmenite was simulated by the unreacted shrinking core model. The reaction rate was simulated by calculating the chlorine gas consumption rate as the unreacted core shrinks. In addition, each of reaction resistances that chemical reaction at the reaction interface, diffusion through the product layer, and boundary film mass transfer resistances were calculated. The simulated reaction rates were in good agreement with the experimental results and the rate controlling step changed as the chlorination reaction progressed. Furthermore, the diffusion resistance through the product layer was dominant at lower reaction temperature, whereas the chemical reaction was dominant as the reaction temperature increased. It is because the diffusion of chlorine gas through the product layer could be hindered at lower reaction temperatures. Key words: Ilmenite, Selective chlorination, Synthetic rutile, Shrinking core model

The Influence of KCl and HCl on the High-Temperature Oxidation of a Fe-2.25Cr-1Mo Steel at 400\xa0\xb0C

The influence of alkali- and chlorine-containing compounds on the corrosion of superheater alloys has been studied extensively. The current paper instead investigates the corrosive effects of KCl and HCl under conditions relevant to waterwall conditions. A low-alloy (Fe-2.25Cr-1Mo) steel was exposed to KCl(s), 500 vppm HCl(g) and (KCl + HCl) in the presence of 5%O2 and 20% H2O at 400 °C. The results indicate that alloy chlorination by KCl occurs by an electrochemical process, involving cathodic formation of chemisorbed KOH on the scale surface and anodic formation of solid FeCl2 at the bottom of the scale. The process is accompanied by extensive cracking and delamination of the iron oxide scale, resulting in a complex, convoluted scale morphology. Adding 500 vppm HCl to the experimental environment (KCl + HCl) initially greatly accelerated the formation of FeCl2 at the scale/alloy interface. The accelerated alloy chlorination is attributed to HCl reacting with KOH at the scale surface, causing the cathodic process to be depolarized. A rapid slowing down of the rate of chlorination and corrosion in KCl + HCl environment was observed which was attributed to the electronically insulating nature of the FeCl2 layer which forms at the bottom of the scale, disconnecting the anodic and cathodic regions.

Global Fitting Functions for Kinetics of Fe-Selective Chlorination in Ilmenite and Successive Chlorination of Beneficiated TiO2

Global fitting functions for Fe-selective chlorination in ilmenite(FeTiO2) and successive chlorination of beneficiated TiO2 are proposed and validated based on a comparison with experimental data collected from the literature. The Fe-selective chlorination reaction is expressed by the unreacted shrinking core model, which covers the diffusion-controlling step of chlorinated Fe gas that escapes through porous materials of beneficiated TiO2 formed by Fe-selective chlorination, and the chemical reaction-controlling step of the surface reaction of unreacted solid ilmenite. The fitting function is applied for both chemical controlling steps of the unreacted shrinking core model. The validation shows that our fitting function is quite effective to fit with experimental data by minimum and maximum values of determination coefficients of R2 as low as 0.9698 and 0.9988, respectively, for operating parameters such as temperature, Cl2 pressure, carbon ratio and particle size that change comprehensively. The global fitting functions proposed in this study are expressed simply as exponential functions of chlorination rate(X) vs. time(t), and each of them are validated by a single equation for various reaction conditions. There is therefore a certain practical merit for the optimal process design and performance analysis for field engineers of chlorination reactions of ilmenite and TiO2.

Methane to Chloromethane by Mechanochemical Activation: A Selective Radical Pathway.

State-of-the-art processes to directly convert methane into CH3Cl are run under corrosive conditions and typically yield a mixture of chloromethanes requiring subsequent separation. We report a mechanochemical strategy to selectively convert methane to chloromethane under overall benign conditions, employing trichloroisocyanuric acid (TCCA) as a cheap and noncorrosive solid chlorinating agent. TCCA is shown to release active chlorine species upon milling with Lewis acids such as alumina and ceria to functionalize methane at moderate temperatures (<150 °C). A thorough parameter optimization led to a maximum methane chlorination rate of 0.8 μmol(CH4,conv) (g(catalyst) s)-1. Findings were compared to the thermal reaction of methane with TCCA and evidenced that mechanochemical activation permitted significantly lower reaction temperatures (90 vs 200 °C) at a drastically improved CH3Cl selectivity (95% vs 66% at 30% conversion). Considering the characterization of the interaction between TCCA and Lewis acids as well as the in-depth analysis of byproducts, we suggest a plausible reaction mechanism and a possible regeneration of the chlorinating agent.

Chlorinated reclaimed rubber: preparation, structure and performance

PurposeThe purpose of this study is to investigate the effect of chlorination on the structure and properties of reclaimed rubber and to discuss the feasibility of a novel method to chlorinate reclaimed rubber.Design/methodology/approachA series of chlorinated reclaimed rubber with different chlorination degrees (CD) was prepared by suspension chlorination in aqueous phase (SCAP). Their structure and performance were characterized by Fourier transform infrared spectrometer, energy dispersive spectroscopy, scanning electron microscopy, thermogravimetric and mechanical property test.FindingsThe chemistry structure, mechanical performance and heat resistance of CRR is affected greatly by its CD.Research limitations/implicationsAlthough in the present work only chlorination of reclaimed rubber is researched, but this method can be used to modify other recycled rubber.Practical implicationsSCAP is a useful method to produce CRR, and it is feasible for production of chlorinated recycled rubber in large scale. The present work provides a new strategy to fabricate new materials based on recycled rubber.Social implicationsChlorination of reclaimed rubber by SCAP is useful to convert waste rubber into new materials, and it is useful to decrease environment pollution.Originality/valueSCAP method provides a new technology to chlorinate waste rubber with many merits, such as chlorination rate of RR is accelerated and the reaction can be controlled or adjusted easily. Moreover, conversion of chlorine is increased remarkably.

Migration and Transformation of Ofloxacin by Free Chlorine in Water Distribution System

This study investigated the degradation kinetics and product generation of ofloxacin (OFL) in the pipe network under different pipe materials, flow rate, pH, free chlorine concentration and temperature. The experiments done in the beaker and pipe network were compared. The results showed that the reaction rate of OFL chlorination with free chlorine increased with the increase of the free chlorine concentration in the pipe network and deionized water, and the degradation efficiency of OFL in the pipe network was higher than that in the deionized water, satisfying the second-order dynamics model. The degradation rate under different pHs was: neutral &gt; acidic &gt; alkaline. The influence of the flow rate is not significant while the influence of the pipe materials and temperature is obvious. The degradation rate of OFL increased with the increase of the temperature, indicating that the OFL degradation was an endothermic process. A liquid chromatograph-mass spectrometer (LC-MS) was used to detect the chlorination intermediates, and the results showed that the piperazine ring was the main group involved in the chlorination reaction, and the main point involved in the chlorination reaction was the N4 atom on the piperazine ring. We also found that, as the reaction time increases, the concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) increase and THMs mainly exist in the form of trichloromethane (TCM) while HAAs mainly exist in the form of monochloroacetic acid (MCAA).

Chlorination of enoxacin (ENO) in the drinking water distribution system: Degradation, byproducts, and toxicity

Chlorine is widely used as a drinking water disinfectant to ensure water security. However, the transformation mechanisms of its degradation of emerging pollutants within the water distribution system (WDS) is insufficiently understood. Thus, the kinetics, degradation byproducts, and toxicity of the chlorination of enoxacin (ENO, a type of emerging pollutant) were explored in a pilot-scale WDS for the first time. It was found that the chlorination rate of ENO was higher in deionized water (DW) than in the pilot-scale WDS, and the degradation followed second-order kinetics in DW. The degradation efficiency was found to be sensitive to pH, and was highest at a pH of 7.4. The chlorination rate of ENO increased with increasing temperature in both DW and WDS. For different pipe materials, the relative performance of ENO chlorination efficiency followed the order of steel pipe > ductile iron pipe > polyethylene (PE) pipe. Seven intermediates were identified during ENO chlorination, and the primary oxidation reaction involved the cleavage of the piperazine group. Finally, it was found that the potential for chlorine toxicity in treated drinking water in the presence of ENO is higher than it is without this pollutant.