Inorganic Chlorine Research Articles

Defect-Rich Regulatory Activity Strategy: Disordered Structure for Enhanced Catalytic Interfacial Reaction of Chlorobenzene.

In contrast to previous defect engineering methods, the preparation of amorphous materials can obtain abundant defect sites through a simple way, which is expected to effectively degrade Volatile Organic Compounds (VOCs) under milder conditions. However, in-depth and systematic studies in this area are still lacking. Novel types of amorphous CeMnx catalysts with abundant defects were prepared through simple hydrothermal synthesis and used for Cl-VOCs catalysis for the first time. Experimental characterizations and DFT calculations proved that Ce doping induced MnO2 lattice distortion, which led to the transformation of CeMnx into an amorphous structure and the formation of abundant defect sites. It was observed that CeMn0.16 was able to eliminate chlorobenzene (CB) at 200 °C, and the CO2 yields and the selectivity of inorganic chlorine was significantly higher than that of MnO2. The 18O isotope kinetic experiments revealed that the interfacial reaction process followed the MVK mechanism. The large number of oxygen vacancies accelerated the migration of lattice oxygen from the interior to the exterior, enhancing the ability to trap gas-phase oxygen. Mn4+ acted as the main active center to participate in CB catalysis, and the resulting reactive oxygen species (ROS) and Mn3+-[O2-]-Ce4+ further accelerated the entire oxidation cycle.

Elucidating synergistic effects and environmental value enhancement in infrared-Assisted Co-Pyrolysis of coal and polyvinyl chloride

Co-pyrolysis of high-alkali coal and polyvinyl chloride (PVC) through infrared heating is a promising approach for managing escalating PVC waste and converting low-grade coal resources efficiently. The synergistic effects during co-pyrolysis and thermal degradation of PVC were studied through thermogravimetric analysis (TG-FTIR) and spectral analysis. Furthermore, chlorine migration and chemical transformation integral to the process, along with catalytic interactions, were explored through chlorine mass balance assessment, employing X-ray photoelectron spectroscopy and ion chromatography to establish a groundbreaking understanding of these phenomena. The results of products exhibited a trend of initially increasing and then decreasing with increasing temperatures and mixing ratios. The maximum oil yield was 14.62 %, achieving at 600 °C and 20 %. Meanwhile, the content of aromatic hydrocarbons remained high level through the synergistic interaction of Lewis and Brønsted acid sites, nearly exceeding 60 %. The results showed that the Artificial Neural Network model had a high prediction accuracy with an R2 value of 0.99, while the decarboxylation effect dissociated the metal, resulting in an increase in the fixation of inorganic chlorine from 1 % to 66 % and a decrease in the chlorine content in the liquid phase. Innovatively, the study employs an ANN model for predicting the behavior of co-pyrolysis, exemplifying high accuracy in understanding complex thermal conversions of PVC and coal. Notably, the work challenges existing constraints by applying sophisticated analytical methods to elucidate the thermodynamics and kinetics of the co-pyrolysis processes, thereby enhancing the energetic and environmental value of the products.

Low-temperature dechlorination methods for pyrolysis oil of municipal plastic waste

Pyrolysis oil produced from municipal plastic waste can be utilized as fuel and various valuable chemicals as an alternative to petroleum. However, pyrolysis oil usually contains a relatively high concentration of chlorinated compounds, obstructing its utilization in the chemical industry. The present research reveals that pyrolysis oil contains inorganic chlorine and organochlorine compounds, and differentiated approaches should be considered to remove Cl from covalent and ionic chlorine linkages. Transition metal-based ZSM-5 catalysts showed remarkable dechlorination performance via mild C-Cl cracking of 1-chlorooctane and 4-chlorotoluene at 180 °C or below. The neutralization method of mixing pyrolysis oil with an alkaline solution quickly eliminated ionic chlorine from inorganic chlorine compounds, reducing Cl concentrations by up to 70 % at temperature below 40 °C. Based on the different dechlorinating pathways, an ideal combination of these two methods was suggested to enhance chlorine removal efficiency from pyrolysis oil.

Chlorine evolution and char characteristics during pyrolysis upgrading of Xinjiang high chlorine coal

Xinjiang ShaErHu (SEH) coal, characterized by a high chlorine concentration exceeding 1 %, can cause severe chlorine corrosion when directly burned. To utilize this high-chlorine coal in an effective and clean way, specific pretreatments such as low-temperature pyrolysis upgrading are required. In this paper, the changes in tar, pyrolysis gas, combustion characteristics, and chlorine evolution features were analyzed during the low-temperature pyrolysis of SEH coal. The effects of increasing temperature (350 °C, 450 °C, and 550 °C) were studied. The results show that the proportion of aromatic compounds released consistently increases with temperature, reaching a peak of 80 % at 550 °C in the tar. It is noteworthy that chlorine is hardly detected in tar. The percentage of chlorine released in the pyrolysis gas remains relatively stable as the temperature rises from 350 °C to 550 °C, accounting for approximately 17.5 % of the total chlorine. The percentages of water-soluble chlorine in raw coal, char-350 °C, char-450 °C and char-550 °C are 74.3 %, 80.4 %, 82.2 %, and 55.1 % respectively. The majority of the chlorine in the char produced at 350 °C and 450 °C is inorganic, making up 68.9 % and 69.4 %, respectively. In contrast, char generated at 550 °C has 58.4 % chlorine that is primarily organic. About 40 % of the inorganic chlorine is converted to organic chlorine when the pyrolysis temperature is raised to 550 °C. This conversion likely occurs as a result of the inorganic chlorine ions combining with carbon to form C-Cl bonds. In order to effectively prevent high temperature corrosion, high-chlorine coal can be treated by pyrolysis at temperatures between 350 and 450 °C, followed by water washing and burning. This research provides a theoretical foundation for the clean and efficient use of high-chlorine coal.

Insights into the inhibitory effects of trichloroisocyanuric acid disinfectant on the phototransformation of polypropylene microplastics

The chemical components in the natural aquatic environment have the potential to be involved in phototransformation of microplastics (MPs). Little information is available regarding the mediation effects of artificially introduced chemicals on MP phototransformation, especially those used in aquaculture water that are vulnerable to human interference. Herein, this study investigated the phototransformation process and mechanism of polypropylene microplastic (PP MPs) in presence of trichloroisocyanuric acid (TCCA) disinfectant with unique properties unlike the conventional inorganic chlorine disinfectants. The results showed that the presence of TCCA inhibited the surface photooxidation of PP MPs. Analysis of PP MP surface and reaction filtrate indicated that the inhibitory effects were likely derived from TCCA derivatives and the weakening in promoting effect of polypropylene microplastic-derived dissolved organic matter (PP-DOM) as photolytic byproducts, with the more important role of free chlorine in initial period and that of other chlorine species (i.e., the adsorbed chloride ions (Cl−), newly formed carbon-chlorine (CCl) bonds, chlorinated cyanurates, and chlorinated products) in middle and later period. The study highlights for the first time the important role of chlorine species derived from TCCA in phototransformation process of co-existed PP MPs and proposes a previously unrecognized phototransformation pathway, which will provide a new understanding and knowledge for the environmental behavior of MPs in aquaculture environment.

Hydrophobic TaOx Species Overlayer Tuning Light-Driven Methane Chlorination with Inorganic Chlorine.

Halogenated methane serves as a universal platform molecule for building high-value chemicals. Utilizing sodium chloride solution for photocatalytic methane chlorination presents an environmentally friendly method for methane conversion. However, competing reactions in gas-solid-liquid systems leads to low efficiency and selectivity in photocatalytic methane chlorination. Here, an in situ method is employed to fabricate a hydrophobic layer of TaOx species on the surface of NaTaO3. Through in-situ XPS and XANES spectra analysis, it is determined that TaOx is a coordination unsaturated species. The TaOx species transforms the surface properties from the inherent hydrophilicity of NaTaO3 to the hydrophobicity of TaOx/NaTaO3, which enhances the accessibility of CH4 for adsorption and activation, and thus promotes the methane chlorination reaction within the gas-liquid-solid three-phase system. The optimized TaOx/NaTaO3 photocatalyst has a good durability for multiple cycles of methane chlorination reactions, yielding CH3Cl at a rate of 233 µmol g-1 h-1 with a selectivity of 83%. In contrast, pure NaTaO3 exhibits almost no activity toward CH3Cl formation, instead catalyzing the over-oxidation of CH4 into CO2. Notably, the activity of the optimized TaOx/NaTaO3 photocatalyst surpasses that of reported noble metal photocatalysts. This research offers an effective strategy for enhancing the selectivity of photocatalytic methane chlorination using inorganic chlorine ions.

Insight into dechlorination of pyrolysis oil during fast co-pyrolysis of high-alkali coal and polyvinyl chloride (PVC)

Thermal treatment can utilize polyvinyl chloride (PVC) in a high-value, eco-friendly method, but HCl generation and high oil chlorine content are key pyrolysis issues. Therefore, this research extensively characterized fast co-pyrolysis of PVC and high-alkali coal (HAC) using XPS, TG-FTIR-GC/MS, and GC-MS. This explored alkali metal catalysis and volatile reforming effects on Cl transfer and utilizing PVC as a hydrogen donor to improve the quality of pyrolysis oil. According to the GC-MS results, increasing the PVC ratio to 40 % raised monocyclic (MAHs) and polycyclic aromatic hydrocarbons (PAHs) to 59.1 % and 33.4 % respectively. However, co-pyrolysis of PVC and HAC inhibited the polyene reconstruction of the carbon skeleton, leading to a decrease of oxygenates, such as phenolic, acid, and ester. The XPS results showed that the inorganic chlorine in the solid product increased from 1 % to 66 % after co-pyrolysis at 600 °C, indicating the high fixed chlorine effect of HAC. Fast heating almost merges the PVC dechlorination stage with the conjugated polyene reconstruction stage, creating a liquid–gas synergy. Abundant coal α-carbon selectively binds with H+, dechlorinated PVC, and polyene fragments, rather than binding with Cl-. This study provides valuable insights into coal-PVC interactions and the dechlorination of pyrolysis oil during fast co-pyrolysis processes and advances the sustainable management of PVC waste.

Study of the migration and distribution pathways of key corrosive species during high-temperature corrosion by means of atom probe tomography and δ35Cl isotope tracer

This study investigated the migration pathways and the dominant chlorine- and alkali-induced corrosion mechanisms of Ni-28Cr-13Al-0.6B-0.5 W alloy at 600ºC. The distribution of key elements (35Cl, 37Cl, Na, O, Ni, Cr, Al) at the alloy/oxide interface was analyzed by APT coupled with δ35Cl isotope labeling for tracing the competitiveness of organic chlorine and inorganic chlorine. The alloying element`s migration rate was in the order of Al > Cr > Ni > W. Cl diffused through oxide grain-boundaries as Cl- ions formed by the decomposition of sulfate-melt and corrosion in grain-boundaries was dominated by electrochemical reaction mechanisms. Na enhances the diffusion of elements by widening the grain-boundaries.

In-situ poly(hexahydrotriazine) gels temporary plugging agent suitable for high-temperature reservoirs: Regulation by inorganic chloride salts

A new acid-soluble in-situ temporary plugging agent suitable for high-temperature reservoirs was developed. By regulating the aldehyde-amine condensation reaction using inorganic chlorine salts, the poly(hexahydrotriazine) gels (PHT gels) exhibit good plugging performance and high-temperature resistance and can be degraded in weak acid solutions without residue. Results show that inorganic chlorine salts have a regulating effect on the gelling time of the gelant. Without the salt or the addition of monovalent chlorine salt, the gelant gels at room temperature but does not form a gel at high temperatures. After adding divalent or trivalent inorganic salts, PHT gels are formed at high temperatures, and their gelling time increases with the increase in salt content. Mechanical compression experiments show that the compression resistance of PHT gels is almost unchanged after exposure to high temperature (140 °C) and high salt (200 g/L NaCl and 10 g/L CaCl2). Displacement experiments show that PHT gels have excellent plugging performance with a plugging rate of more than 98.50% and a maximum plugging pressure of 5.34 MPa under the high temperature and high-salt conditions mentioned above. In addition, a hydrochloric acid solution with pH ≤ 5 can achieve residue-free breakage of PHT gels. The gel-breaking fluid has a high surface activity to facilitate flowback and a core unblocking rate of more than 100% after gel-breaking, making the reservoir permeability recoverable. The plugging and acidolysis ability of PHT gels make them excellent in-situ temporary plugging agents. This study aims to provide insights into the preparation of PHT gels and their use in high-temperature reservoirs.

Plasma driven exsolution of Ca as the adjacent dechlorinated site in La0.8Ca0.2MnO3 perovskite: A highly mineralization chlorobenzene oxidation catalyst

The degradation of chlorine-containing volatile organic compounds (CVOCs) catalytic combustion technology is subject to the catalyst chlorine poisoning, which is resulted from the chlorination of active phases, even though the structural stable perovskite. The reaction between Ca species and dissociated chlorine species is demonstrated as an efficient way to inhibited chlorine poisoning of the active phase. Herein, a Ca substituted partial La prepared La0.8Ca0.2MnO3 (named as L8C2MO) perovskite was treated by 5% H2/Ar plasma driven route (the treated sample was denoted as L8C2MO-P), which was applied for the chlorobenzene oxidation removal. The integrated characterization results of XRD, XPS, HRTEM, etc. confirmed that Ca (mainly exhibited as CaCO3) was successfully exsolved from La0.8Ca0.2MnO3 and simultaneously leaved oxygen vacancies on the surficial layers. The continuous catalytic oxidation experiments illustrated that the conversion efficiency of L8C2MO was unexpectedly decreased compared with that of LaMnO3 (LMO in short) sample, while that of L8C2MO-P was nearly maintained the oxidation capacity, with approximately 12 °C of 90% chlorobenzene conversion temperature (T90) higher than that of LMO. Importantly, the CO2 and inorganic chlorine species yields were significantly enhanced for L8C2MO and L8C2MO-P. The characteristic of used samples showed a possible chlorinated Ca species formation while the status of Mn phases was hardly changed, suggesting the exsolved Ca could inhibit the poison of Mn sites by binding with dissociative chlorine species. Additionally, oxygen vacancies that generated along with Ca exsolution process was definitely contributed to the deep oxidation of chlorobenzene. The possible reaction route was also studied by in situ DRIFTS and GCMS. The work provides a potential route as in situ growth of adjacent sites to protect active phases from chlorine poison in CVOCs catalytic oxidation process.

Phosphotungstic Acid as a Dechlorination Agent Collaborates with CeO2 for Synergistic Catalytic Elimination of NOx and Chlorobenzene.

The development of efficient technologies for the synergistic catalytic elimination of NOx and chlorinated volatile organic compounds (CVOCs) remains challenging. Chlorine species from CVOCs are prone to catalyst poisoning, which increases the degradation temperature of CVOCs and fails to balance the selective catalytic reduction of NOx with the NH3 (NH3-SCR) performance. Herein, synergistic catalytic elimination of NOx and chlorobenzene has been originally demonstrated by using phosphotungstic acid (HPW) as a dechlorination agent to collaborate with CeO2. The conversion of chlorobenzene was over 80% at 270 °C, and the NOx conversion and N2 selectivity reached over 95% at 270-420 °C. HPW not only allowed chlorine species to leave as inorganic chlorine but also enhanced the Bro̷nsted acidity of CeO2. The NH4+ produced in the NH3-SCR process can effectively promote the dechlorination of chlorobenzene at low temperatures. HPW remained structurally stable in the synergistic reaction, resulting in good water resistance and long-term stability. This work provides a cheaper and more environmentally friendly strategy to address chlorine poisoning in the synergistic reaction and offers new guidance for multipollutant control.

Source analysis of chlorine in municipal solid waste under waste classification: a case study of Hangzhou, China.

Inorganic chlorine is susceptible to water and soil salinization due to its non-degradability and high mobility. To clarify the environmental risks associated with the active inorganic chlorine in municipal solid waste (MSW), the specific characteristics and contributions of inorganic chlorine in different MSW categories were investigated in this study. MSW samples were collected from eight representative waste classification residential areas in Hangzhou, China. It was found that the inorganic chlorine content in different MSW categories varied significantly (0-113 mg/g). Perishable waste, paper, and plastic were found to be the main sources of inorganic chlorine in MSW. A four-category classification system was used to quantify the contribution of inorganic chlorine from each waste category. It was found that the misclassification of inorganic chlorine contributions from perishable waste and other waste accounted for 51.96% and 48.04%, respectively. However, when correctly classified into the four-category system, their contributions were reduced to 67.14% and 30.65%, respectively. Therefore, MSW classification showed a significant reduction in the overall contribution of inorganic chlorine. The misclassification reduces the contribution of inorganic chlorine to 48.04%, while correct classification increases the reduction to 69.35%.

Evolution and speciation transformation of chlorine during automobile shredder residue pyrolysis

Disposal of automobile shredder residue (ASR) via pyrolysis enables the recovery of valuable products; however, the production of hazardous pollutants and low-value products is inevitable due to its high chlorine content. In this work, chlorine evolution behavior and the conversion mechanism during ASR pyrolysis between 480 and 600 °C were systematically studied. The experimental results for organic chlorine (Org-Cl) showed that released chlorinated gases were complex, and HCl only accounted for 35% of the gas phase products, while short-chain hydrocarbons with carbon atoms between two and four accounted for 52%. Chlorine was predominantly retained in the char, and Org-Cl was the primary contributor to the residual chlorine, accounting for over 50% of the char. The content of inorganic chlorine (InO-Cl) was low in the raw sample but significantly increased in the char. Through the distinction between organic and inorganic chlorine content in char, it was confirmed that Org-Cl could be converted to InO-Cl due to complex secondary reactions with metallic compounds. The conversion was favored by increasing the Org-Cl content and the temperature. Our findings clarified the evolution mechanism of chlorine and the transformation from Org-Cl to InO-Cl, thus providing guidance for chlorine regulation and the efficient recycling of metal resources.

Comparison on the formation and toxicity for chlorinated products during the oxidation of acetic acid (CH3COOH) by three widely used advanced oxidation processes (AOPs) at the presence of [formula omitted]

As a technology for industrial wastewater advanced treatment, there is a lack of relevant information the impacts of the treated effluents by advanced oxidation processes (AOPs) on ecological environment. Therefore, this study mainly compared the differences of the formation types and concentrations of chlorinated organic products（COPs）and active inorganic chlorine species (AICS) and toxicity changes in the oxidation of CH3COOH by three commonly used AOPs technologies as Fenton, ozone and electrochemical advanced oxidation process (EAOP) with the addition of Cl−. The results illustrate that in the EAOP process, trichloromethane (TCM) and Chloroacetic acids (CAAs) were the main COPs in the oxidation of CH3COOH by EAOP at 120 min. CCl4 was major COPs for the Fenton and ozone oxidation of CH3COOH, respectively. Through the algae growth inhibition experiment and the toxicity evaluation by using ECOTOX toxicity database, the toxicity of EAOP oxidation of CH3COOH to algae and fish were much higher than those from Fenton and ozone oxidation as the highest formation concentrations of inorganic by-products. Considering the toxic effects on the environment, when choosing the AOPs for the further treatment of wastewater containing Cl−, try to avoid the use of EAOP technology, and it is better to choose Fenton and ozone oxidation.

Highly efficient MnOx catalysts derived from Mn-MOFs for chlorobenzene oxidation: The influence of MOFs precursors, oxidant and doping of Ce metal

In this research, we introduce a simple, effective, and eco-friendly approach for preparing MnOx materials with a hierarchical porous structure and apply it to the catalytic oxidation of chlorobenzene. In this method, different Mn-based MOFs are used as templates, and MnOx materials with various morphologies and structures are prepared through an alkaline hydrolysis-oxidation method. Different Mn-MOF precursors, oxidants and doping of different metals have a considerable influence on the structural morphology of the obtained MnOx materials. Through adjusting the structural morphology, it is conducive to transfer, diffusion and enrichment of chlorobenzene during the reaction process, and improving the reaction activity. MnO2-74 catalyst derived from Mn-MOF-74 in the presence of H2O2 showed the best catalytic activity (T90 = 174 °C). The exceptional catalytic efficiency is attributed to its large specific surface area, mesoporous structure, better low-temperature reducibility, sufficient acidic sites, and enhanced oxygen activation ability. The primary cause of the decrease in catalytic activity is the existence of surface carbon and inorganic chlorine on the catalyst. This green, efficient, and economical preparation method introduces a novel strategy for the traditional derivatization of MOFs to prepare metal oxide materials for the catalytic oxidation of chlorinated volatile organic compounds (CVOCs).

An alkali-enhanced subcritical water treatment strategy of short-chain chlorinated paraffins: Dechlorination and hydrocarbons recovery

As persistent organic pollutants, short-chain chlorinated paraffins (SCCPs) have attracted wide attention in the field of environmental health risk and hazardous waste management. Efficient dechlorination of high content of SCCPs in plastic waste is the committed step for its detoxification and safety treatment. In this study, a high-efficiency and low-temperature process for dechlorination and hydrocarbons recovery from typical SCCPs (52#SCCPs) by subcritical water (SubCW) with alkali enhancer was developed. The introduction of alkali enhancer in the SubCW process had significantly enhanced effect on the dechlorination of 52#SCCPs, and the order of the enhanced effect of alkali enhancer for the dechlorination was NaOH > Na2CO3 > NaHCO3 > NH3·H2O > KOH. The dechlorination behaviors of 52#SCCPs in the NaOH-enhanced SubCW process were studied systematically under different conditions including temperature, residence time, alkali concentration, and volume ratio. The results showed that high-efficiency dechlorination (100 %) of 52#SCCPs could be achieved by the NaOH-enhanced SubCW process at low temperature for a short time (250 °C, 5 min). All of the chlorine released from the molecular chain of 52#SCCPs was transferred to the aqueous phase in the form of inorganic chlorine. The continuous HCl elimination reaction was the primary dechlorination mechanism for 52#SCCPs in the NaOH-enhanced SubCW process. After the dechlorination of 52#SCCPs, high value-added hydrocarbons such as 2,4-hexadiyne (31.74 %) could be obtained. The alkali-enhanced SubCW process proposed in this study is believed to be an environmentally friendly and high-efficiency method for dechlorination/detoxification and resource recovery of SCCPs.

Driving factors influencing spatiotemporal variation of natural organic chlorine in Shennongjia forest soil

Studying the geochemical behavior of chlorine is the basis of understanding the chlorine cycle in nature. To explore the spatiotemporal distribution of natural organic chlorine (Clorg), L layer (litter fall), F–H layer (humification zone), topsoil layer (0–20 cm), and deep soil layer (20–40 cm) samples were collected from 18 sampling sites at different altitudes (851–2918 m) in Shennongjia Forest in May, August, and December. Clorg content was analyzed, and the Clorg stocks were calculated. The major factors affecting the distribution of Clorg were explored. The results revealed that the sum of Clorg content in four layers varied from 7.958 to 184.686 mg/kg, and the highest value was observed in August. Clorg accounted for 46%–77% of total chlorine, with the highest mean ratio in soil layer (0–20 cm). Clorg content exhibited the following trend: F–H layer > L layer > topsoil layer (0–20 cm) > deep soil layer (20–40 cm). The seasonal patterns of Clorg in soil layers were different from that in L and F–H layers, which were mainly controlled by the content and humification degree of organic matter. Clorg storage was much higher in soil layers (61–246 kg/ha) than those in F–H layer (1.1–7.1 kg/ha) and in L layer (0.1–0.8 kg/ha) because of the large thickness of the soil layers. Overall, the Clorg content exhibited an increasing trend with altitude, except at an altitude of approximately 1800 m. Clorg content in L and F–H layers varied more obviously with altitude than that in soil layers. When inorganic chlorine (Clin) was not a limiting factor for the chlorination process, Clorg content in L and F–H layers was significantly affected by climate and organic matter controlled by altitude, while Clorg content in soil layers was also mediated by metal ions and pH, and soil particle size. This study could provide a scientific basis for assessing the chlorine cycle in nature.

High-efficiency promotion on dechlorination of polyvinyl chloride in subcritical water treatment by introducing waste concrete

Polyvinyl chloride (PVC) is one of the most widely used plastics in the world. Due to the generation of corrosive HCl and chlorine-containing organic pollutants during the recycling process, waste PVC can cause great environmental risks. At the same time, a large number of waste concrete in the construction industry have not been effectively utilized. Subcritical water (SubCW) has showed good prospect for treatment of PVC due to that dechlorination can be carried out with lower energy consumption. In this study, a high-efficiency and low-temperature SubCW treatment for dechlorination of PVC using waste concrete as an enhancer was proposed. The effects of temperature, residence time, solid-to-liquid ratio and PVC-to-Concrete ratio on dechlorination efficiency, chlorine distribution and weight loss ratio were studied. The PVC dechlorination efficiency could be enhanced to as high as 95.04% by introducing waste concrete. Significant dechlorination occurred under the conditions of 220 ℃, 60 min, solid-to-liquid ratio of 1:30 g/mL, and PVC-to-Concrete ratio of 4:1. Under the optimal conditions, all the removed chlorine from PVC was transferred into the liquid phase in the form of inorganic chlorine. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and elemental analysis were used to analyze the PVC dechlorination mechanism. The dechlorination pathway of PVC was found to include both direct dehydrochlorination and hydroxyl substitution. The enhancement mechanism of the waste concrete on the PVC dechlorination could be attributed to the rapid capture ability of CaCO3 for HCl. The SubCW-Concrete process proposed in this study was beneficial to both the low-temperature dechlorination of PVC and the resource utilization of waste concrete.

Effect of granulation on chlorine-release behavior during municipal solid waste incineration.

The preparation of refuse-derived fuel (RDF) is an effective and simple means of rural municipal solid waste utilization. The release of chlorine during RDF combustion is important as it causes high-temperature corrosion and pollutants emission such as HCl, dioxins, etc. In this paper, constant-temperature and increasing-temperature combustion experiments were carried out using an electrically heating furnace to analyse the effects of granulation (pressure and additives) on the release of chlorine in particles. During the constant-temperature combustion below 800 °C, only organic chlorine was released from the RDF. The increase of granulation pressure from 1 MPa to 10 MPa did not affect the total amount of chlorine release, but delayed the organic chlorine release by increasing the gas diffusion resistance. During the constant-temperature combustion above 900 °C, inorganic chlorine was released as well. The increase of granulation pressure enhanced the inorganic chlorine release significantly by promoting the reactants contact. During the increasing-temperature combustion, the increase of granulation pressure delayed the organic chlorine release as well but inhibited the inorganic chlorine release. This was mainly attributed to the slow temperature rise to 900 °C, during which the inherent calcium in the RDF reacted with silicon and aluminium, resulting in less reactants for an inorganic chlorine release reaction. Three calcium-based additives were used to inhibit chlorine release. CaCO3 showed no dechlorination effect, and CaO showed better dechlorination effect than Ca(OH)2. For the constant-temperature combustion at 900 °C, the addition of CaO with a Ca/Cl ratio of 2 achieved a dechlorination efficiency of over 90%, with little influence from the granulation pressure. For the increasing-temperature combustion, the granulation pressure had a significant influence on CaO dechlorination effectiveness. Only at a granulation pressure as high as 10 MPa, did the addition of CaO with the Ca/Cl ratio of 2.5 achieve a dechlorination efficiency of 95%.

Comparison of the ability of three advanced oxidation processes (AOPs) converting [formula omitted] to active inorganic chlorine species (AICS)

Advanced oxidation processes (AOPs) during wastewater treatment oxidise Cl−to active inorganic chlorine species (AICS). AICS can react with organic compounds in wastewater to form toxic and hazardous chlorinated organic compounds, most of which are carcinogenic, teratogenic, and mutagenic. In this study, the abilities of three AOPs, i.e., electrochemical, ozone, and Fenton, to convert Cl− to AICS were compared. The results showed that at an initial Cl−concentration of 710 mg-Cl/L and a reaction time of 120 min, the conversion efficiencies of electrochemical, ozone, and Fenton processes were 74.1%, 21.0%, and 4.1%, respectively. The respective concentrations were 436.44 mg-Cl/L, 2.23 mg-Cl/L, and below detection limit for free chlorine; and 82.29 mg-Cl/L, 65.11 mg-Cl/L, and 6.30 mg-Cl/L for ClO3−. The abilities of the three AOPs to convert Cl−to AICS were in the order, electrochemical≫ ozone ≫ Fenton. In the present study, the potential reasons for the significant differences in theCl− oxidising ability of the AOPs were discussed. The effects of temperature and initial pH on the formation of free chlorine in the ozone and electrochemical processes were also investigated. These results are of great significance for the selection of AOPs for treating wastewater containing Cl− in practical applications.