Removal Of Chlorine Research Articles

Removal of chlorine and monochloramine from tap water using graphene oxide membranes

Residual levels of chlorine and monochloramine (chlor(am-)ine) in water not only cause unpleasant odour and taste but also pose a challenge for chlor(am-)ine sensitive applications such as polymeric membranes used in reverse osmosis for desalination. Current solutions to remove chlor(am-)ine have their limitations and it is thus desirable to develop an alternative technology that can remove chlor(am-)ine in a simple filtration process. In this study, we show that graphene oxide (GO) membranes can be used to remove chlor(am-)ine from tap water. The tested feed chlorine and monochloramine concentrations are up to 50 ppm and 9 ppm respectively. For all tested feed concentrations, the permeate chlor(am-)ine concentration is < 0.1 ppm after passing through GO membranes. We show that both flat sheet and hollow fibre GO membranes filter out chlor(am-)ine over days of continuous operation. Especially our hollow fibre GO membranes offer a great opportunity for easy scalability. Thus our study highlights not only the filtration properties of GO membranes but also its feasibility as an excellent contender for next-generation membrane technology.

TECHNOLOGY FOR PRODUCING THERMOPHOSPHATE PRODUCTS BASED ON PHOSPHORITES WITH ADDITIVES OF ALKALINE SALTS

The essence of this work is to study the microstructure and mechanical properties of mixed salts of alkali metals, such as sodium and potassium, phosphorites of the Central Kyzylkum of various compositions. This raw material, low in phosphorus and rich in carbonate and chlorine, is not suitable for acid treatment. To obtain high-quality phosphate fertilizers from raw materials, it must first be enriched. At the Kyzylkum Phosphate Plant, multi-stage enrichment is carried out: crushing, dry enrichment, chlorine removal, sintering to remove CO2. One of the promising areas for the processing of phosphate raw materials of this type is heat treatment, based on the destruction of the crystalline structure of the mineral, which is indigestible by plants, during thermal activation. The work is aimed at obtaining a thermophosphate fertilizer, which is insoluble in water at different temperatures and times in optimal proportions with sodium chloride, sulfate, potassium carbonate, chloride, sulfate salts, sylvinite and silicon oxide/coal, which are more active. The regularity of the influence of temperature and weight ratios of the mineralized mass from the fractions of phosphorite ore of the Central Kyzylkum: silicon oxide/coal: sodium salts on the assimilable phosphorus in thermophosphate fertilizer is shown, as well as the fact that the digestibility of phosphorite ore of the II-layer is higher than that of other raw materials. An increase in the content of assimilable phosphorus in synthesized primary phosphorus thermophosphate fertilizers with an increase in temperature and time is substantiated at equal weight ratios of phosphorite ore of the II layer: silicon oxide/coal: sodium salt.

Experimental study of order and constant rate of chlorine removal reaction using ion exchange resin

In this research, a strong anionic resin was prepared to remove chloride ions. This study was performed in a laboratory pilot to evaluate effective parameters such as temperature, amine flow rate, pH, chloride ion concentration and concentration of resin caustic. The purpose of this work is to determine kinetics of the resin reaction and determination of the optimal operating conditions in order to achieve maximum saturation. This study shows that volume of distilled water passing through resin to eliminate alkalinity at temperatures 40 °C, 50 °C and 60 °C is equal to 5500 ml, 5000 ml and 7000 ml, respectively. This work states that a temperature 50 °C is more appropriate than other temperatures. The results of this research show that volume of caustic for resin recovery is 8.5 L at a temperature of 50 °C. This study shows that amount of distilled water to eliminate alkalinity of the resin is equal to 5 L. Results show that the order of reaction to chloride ion concentration is equal to 0.794 and reaction constant is equal to exp (−1.8753).

Dechlorination of waste polyvinyl chloride (PVC) through non-thermal plasma

Dechlorination is essential for the chemical recycling of waste polyvinyl chloride (PVC) plastics. This study investigated the use of non-thermal plasma (NTP) for chlorine removal, with a focus on the effects of treatment time and discharge power on dechlorination efficiency. The results showed that longer treatment times and higher discharge powers led to better dechlorination performance. The maximum efficiency (98.25%) and HCl recovery yield (55.72%) were achieved at 180 W power after 40 min of treatment where 96.44% of Cl existed in the form of HCl gas, 1.44% in the liquid product, and 2.12% in the solid residue product. NTP at a discharge power of 150 W showed better dechlorination performance compared to traditional thermal pyrolysis treatment in temperatures ranging from 200 to 400 °C. The activation energy analysis of the chlorine removal showed that compared to pyrolysis-based dechlorination (137.09 kJ/mol), NTP-based dechlorination (23.62 kJ/mol) was more easily achievable. This work presents a practical method for the dechlorination of waste PVC plastic using a novel technology without requiring additional thermal and pressure input.

Unlocking the potential of resuscitation-promoting factor for enhancing anaerobic microbial dechlorination of polychlorinated biphenyls

Microbial dechlorination of polychlorinated biphenyls (PCBs) is limited by the slow growth rate and low activity of dechlorinators. Resuscitation promoting factor (Rpf) of Micrococcus luteus, has been demonstrated to accelerate the enrichment of highly active PCB-dechlorinating cultures. However, it remains unclear whether the addition of Rpf can further improve the dechlorination performance of anaerobic dechlorination cultures. In this study, the effect of Rpf on the performance of TG4, an enriched PCB-dechlorinating culture obtained by Rpf amendment, for reductive dechlorination of four typical PCB congeners (PCBs 101, 118, 138, 180) was evaluated. The results indicated that Rpf significantly enhanced the dechlorination of the four PCB congeners, with residual mole percentages of PCBs 101, 118, 138 and 180 in Rpf-amended cultures being 16.2–29.31 %, 13.3–20.1 %, 11.9–14.4 % and 9.4–17.3 % lower than those in the corresponding cultures without Rpf amendment after 18 days of incubation. Different models were identified as appropriate for elucidating the dechlorination kinetics of distinct PCB congeners, and it was observed that the dechlorination rate constant is significantly influenced by the PCB concentration. The supplementing Rpf did not obviously change dechlorination metabolites, and the removal of chlorines occurred mainly at para- and meta- positions. Analysis of microbial community and functional gene abundance suggested that Rpf-amended cultures exhibited a significant enrichment of Dehalococcoides, Dehalogenimonas and Desulfitobacterium, as well as non-dechlorinators belonging to Desulfobacterota and Bacteroidetes. These findings highlight the potential of Rpf as an effective additive for enhancing PCB dechlorination, providing new insights into the survival of functional microorganisms involved in anaerobic reductive dechlorination.

Methods for removing chloride ions to manufacture zinc from arc melting dust

In this work, we review literature sources to identify an industrial-scale technology for manufacturing cathode zinc from technogenic chlorine-containing raw materials of a complex chemical composition, in particular, from arc melting dust. The conducted review of Russian and foreign publications was used to search for a method of purifying process solutions with a high concentration of chloride ions produced by hydrometallurgical processing of technogenic arc melting dusts. It was found that the existing purification methods are associated with substantial limitations, including strict requirements for the acidity of the treated solution, low efficiency of treatment, secondary contamination of the medium by released chloride ions, and the high cost of reagents or equipment. Approaches to reducing the chlorine content in the initial dust and dechlorination of process solutions based on principles of sedimentation, ion exchange, sorption, and oxidation are described. In addition, we analyzed information published on chlorine removal from process effluents and solutions of various nature. Industrially-implemented and recently-reported laboratory methods of solution dechlorination were compared in terms of their feasibility, economic efficiency, and extent of chloride ion removal. It was concluded that the disadvantages of existing methods for processing technogenic chlorine-containing raw materials of arc melting can be eliminated by developing large, stable, and cheap hydride technologies based on principles of extraction, ion exchange, and sedimentation.

Triggered heavy metals and chlorine simultaneous removal from hazardous waste incineration fly ash

To date, heavy metals and chlorine removal from hazardous waste incineration fly ash (HWI FA) by thermal treatment was scarcely reported. High content of calcium in HWI FA might affect heavy metals chlorination volatilization. The aim of this study was to realize heavy metals and chlorine simultaneous removal from HWI FA triggered by fluidized-bed municipal solid waste incineration fly ash (FBMSWI FA) during sintering. Results showed that the dilemma of low heavy metals removal efficiency was due to the dense structure and the difficulty of transformation of the stable phases including Cu2S, CuSiO3, and Zn2SiO4. By co-sintering with FBMSWI FA at the ratio of 1:1, the removal efficiency of Cu, Zn, Pb, Cd, and Cl reached as high as 84.4%, 92.0%, 99.9%, 99.5%, and 99.7%, respectively. Compared with the control, chlorination volatilization efficiency of Cu and Zn was significantly increased by 210.5% and 89.2%. The favourable promotion could be mainly attributed to Si/Al matrix in FBMSWI FA triggered the following reaction: i) Ca-bearing compounds in HWI FA were activated to destroy the dense structure, which facilitated the transformation of Cu2S to CuO; and ii) the conversion of NaCl and KCl to gaseous chlorine was promoted, which the formation of metal chlorides was accelerated.

Synergistic effect and chlorine migration behavior in co-pyrolysis of Pingshuo coal and polyvinyl chloride and directional chlorine enrichment using calcium oxide

Co-pyrolysis of waste plastics and low-rank coal is an important way to realize the recycling of plastic wastes and the clean and efficient conversion of coal. However, halogens released would cause equipment corrosion and affect tar quality when halogenated plastics were co-pyrolyzed with coal. For this reason, polyvinyl chloride (PVC), as a representative of halogenated plastic, was co-pyrolyzed with Pingshuo coal (PS) in a two-stage fixed-bed reactor. The synergistic effect between PS and PVC and the migration behavior of chlorine were investigated, and the in-situ removal of chlorine during pyrolysis was explored by adding a CaO bed in the second stage of the reactor. The results showed that the addition of PVC in PS has a positive synergistic effect on tar yield with a maximum tar yield increment of 2.30 wt% at 30 wt% PVC, which is related to the negative synergistic effect on gas yield. Furthermore, the addition of PVC increases the content of 1–3 ring aromatics and decreases the content of aliphatics in the tar. The chlorine content in char and tar increases significantly with the increase of PVC addition. The addition of a CaO bed can significantly reduce the yield of HCl and the chlorine content in the tar. At 700 ℃, the dehydrochlorination efficiency of CaO can reach 78.1%. However, the CO2 produced by PS pyrolysis will reduce the dehydrochlorination efficiency of CaO, and this effect of CO2 can be reduced by increasing the temperature of the CaO bed.

Production, Characterization, and Activation of Biochars from a Mixture of Waste Insulation Electric Cables (WIEC) and Waste Lignocellulosic Biomass (WLB)

Waste insulation electrical cables (WIEC) currently do not have an added value, due to their physical–chemical characteristics. Carbonization is known to enhance feedstock properties, particularly fuel and material properties; as such, this article aimed to study the production and activation of biochars using WIEC and lignocellulosic biomass wastes as feedstock. Biochars were produced in a ceramic kiln with an average capacity of 15 kg at different temperatures, namely 300, 350 and 400 °C. After production, the biochars were further submitted to a washing process with water heated to 95 °C ± 5 °C and to an activation process with 2 N KOH. All biochars (after production, washing and activation) were characterized regarding an elemental analysis, thermogravimetric analysis, heating value, chlorine removal, ash content, apparent density and surface area. The main results showed that the increase in carbonization temperature from 300 to 400 °C caused the produced biochars to present a lower amount of oxygen and volatile matter, increased heating value, greater chlorine removal and increased ash content. Furthermore, the activation process increased the surface area of biochars as the production temperature increased. Overall, the carbonization of WIEC mixed with lignocellulosic wastes showed potential in enhancing these waste physical and chemical properties, with prospects to yield added-value products that activates biochar.

Chlorine and heavy metals removal from municipal solid waste incineration fly ash by electric field enhanced oxalic acid washing

Electric field enhanced oxalic acid (H2C2O4) washing was conducted to examine the simultaneously removal efficiency of heavy metals (HMs) and chlorine, especially insoluble chlorine from municipal solid waste incineration fly ash (MSW FA). Results show that chlorine and HMs can be effectively removed with a total chlorine, As, Ni and Zn removal rate of 99.10%, 79.08%, 75.42% and 71.43%, when the electrode exchange frequencies is 40 Hz, current density is 50 mA/cm2, H2C2O4 adding amount is 0.5 mol/L and the reaction time is 4 h. Insoluble chlorine removal efficiency is up to 95.32%, much higher than reported studies. And the chlorine content in the residue is lower than 0.14%. Meanwhile, HMs removal efficiency is remarkable, 41.62%–67.51% higher than that of water washing. The high-efficient removal effect is caused by the constantly changing direction of electrons hitting the fly ash surface, which provides more escape channels for internal chlorine and HMs. These results proved that electric field enhanced oxalic acid washing could be a promising method for removing contaminants from MSWI fly ash.

Chemical Regeneration of Activated Carbon Used in A Water Treatment System for Medical Services

The chemical regeneration of exhausted granular activated carbon (GAC) from a water treatment plant to produce dialysis water used in hemodialysis treatments for chronic renal disease patients from a general Hospital of Ciego de Avila province, Cuba, was investigated. Activated carbon (AC) exhausted mainly by inorganics (Ca (Ca-chelates), Mg and Na) was regenerated using hydrochloric acid and acetic acid (one regeneration cycle). Solutions of 5%, 10%, 15% and 20%(v/v) as well as four contact times (2 h, 4 h, 6 h and 48 h) for hydrochloric acid and three contact times (2 h, 4 h and 6 h) for acetic acid at 25°C and 1 atm in a dosage of 1 g GAC/10 mL were used. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), thermogravimetric analysis (TGA), X-ray absorption technique (XRA) and Scanning Electronic Microscopy (SEM) were used to evaluate the effect of the regeneration on exhausted GAC. Batch and scaled column experiments were developed. Breakthrough curves were obtained to assess the AC’s performances after chemical regeneration. The removal/adsorption capacity towards free chlorine (as disinfection agent) and hardness ions (expressed in mg CaCO&lt;sub&gt;3&lt;/sub&gt;/L) was estimated using the area under the breakthrough curves from scaled columns experiments. The hydrochloric acid arises as the best acidic regenerator; using a concentration of 20%(v/v), regenerated GACs using hydrochloric acid showed the highest desorption rate of inorganics as well as a free chlorine removal performance of around 30% concerning the virgin GAC sample. A new GAC management scheme is proposed for GACs used in the medical industry to improve the sustainability and economics of the water treatment process.

Properties of composite sintered modified fluidized bed incineration fly ash as cement admixture

As a hazardous solid waste, circulating fluidized bed incineration fly ash faces the risk of heavy metal leaching and excess dioxin content, and thermal treatment plays an important and increasingly evident role in its environmentally sound disposal. This paper summarizes numerous studies and proposes the composite sintering of circulating fluidized bed incineration fly ash with limestone powder. The operation of the composite sintering on the physicochemical properties of circulating fluidized bed incineration fly ash and the performance of the cement prepared as cement admixture were studied. The results show that the composite sintering can decompose more than 92.7% of chlorine and 99.9% of dioxins, increase the activity of volcanic ash to 79%, and produce new minerals - Ye'elimite and Larnite, However, the content of heavy metals will increase due to the enrichment. The prepared cement can solve the bulk cracking caused by aluminum, reduce the water demand by more than 3.6%, and increase the 3 d compressive strength by 19.09% at 5% admixture and 50.2 MPa at 28 d. Besides, there is no risk of excessive leaching of heavy metals. The content of fly ash from circulating fluidized bed incineration in cement increases from 0.52% to 7.14% after composite sintering. It is proved that composite sintering is beneficial to the enhancement of the resource recovery capacity of hazardous solid waste in the cement industry. In this experiment, chlorine remains the most critical factor limiting its application, and the removal of chlorine should be the focus of the subsequent experiments to expand its resource recovery pathway.

Space stability by incorporating iron atoms into the cobalt structure enabling capacitive deionization stability possible

Exploring and designing high performance pseudocapacitance electrode materials is of great significance in enhancing the desalination performance of capacitive deionization (CDI). Transition metal cobalt is considered a prospective electrode material for CDI because of its abundance and high theoretical capacity, which can produce a higher salt removal capacity than pure capacitive materials in the CDI process. However, due to the collapse and loss of the active electrode crystal matrix, the cobalt electrode exhibits poor electrochemical performance. In this work, we used a second metal element, Fe, introduced by ion exchange pyrolysis to regulate the leaching effect and optimize the ion matching for cobalt to protect the electrode structure. In addition, the interconnected external carbon layers form a robust matrix for enhanced electrical conductivity with ion transport. Thanks to the synergistic effect of the cobalt‑iron (Co3Fe7@C) electrode structure and surface engineering, the adsorption capacity reached 72.29 mg·g−1, achieving 110 % capacity retention in 100 cycles of chlorine removal. As a result, the carbon-coated cobalt‑iron bimetallic electrode exhibits excellent dechlorination capabilities in capacity, cycle life and rate capability. This study provides a promising avenue for the design of stable electrode materials for capacitive deionization electrodes.

Enhancing the dechlorination of CuCl residue using a microwave sulfation-roasting method: Process optimization and mechanism investigation

Spent CuCl residue produced from zinc hydrometallurgy is a typical toxic and hazardous solid waste as well as a secondary resource owing to its high contents of chlorine and valuable metals (Pb, Cu, Zn). The removal of chlorine from the CuCl residue and recycling of valuable metals are critical issues for the copper slag resource treatment process. In this study, a novel method of microwave sulfation-roasting under an oxygen atmosphere is used to improve the dechlorination process, and various parameters, such as roasting temperature, duration, sulfuric acid concentration, and liquid/solid ratio, are optimized. First, according to thermodynamic calculations, the addition of H2SO4 can significantly decrease both the roasting temperature and time needed for microwave oxidation-roasting. The dechlorination experimental results reveal that the dechlorination rate of the CuCl residue is as high as 91.91% under a temperature of 250 °C, holding time of 120 min, sulfuric acid concentration of 70%, and liquid-solid ratio of 1.42. The microstructure, chemical composition, and phase changes of the CuCl residue before and after roasting are characterized using scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray fluorescence and X-ray diffraction; further, the mass contents of the main elements in the roasting product and tail gas absorption solution are determined by chemical analysis, Evidently, the selective heating property of microwaves produces more holes and cracks in the copper slag, which can provide a new reaction channel for H2SO4 and CuCl slag reactions, and almost all CuCl in the copper slag is completely removed by transformation into CuO, CuSO4 and Cu2O(SO4). Simultaneously, a large number of gas by-products produced in the dechlorination process, such as SO2 and Cl2, can be absorbed by the NaOH solution. Therefore, no pollution is generated in the environment. These findings illustrate that microwave sulfation-roasting is an effective method for promoting the treatment and recycling of CuCl waste residues.

Insights into the evolution of chemical structure and pyrolysis reactivity of PVC-derived hydrochar during hydrothermal carbonization.

Hydrothermal carbonization (HTC) is emerging as an effective technology to convert PVC into highly valuable materials via the removal of chlorine. This means that an in-depth understanding of HTC requires the hydrochar structure, thermal degradation behavior, and relationship between structure and thermal reactivity to be understood. In this work, two typical PVC waste materials were selected for HTC experiments at different temperatures. The structure of the hydrochar was characterized in detail by compositional analysis, FTIR spectroscopy, and 13C NMR analysis. Furthermore, the thermal degradation behavior of the hydrochar was analyzed. The changes after thermal degradation were used to establish a correlation with pyrolysis reactivity. The results showed that the C content and chemical structure of the hydrochar approached that of bituminous coal with increasing HTC temperature. Compared with the untreated PVC feedstock, the hydrochar exhibited higher levels of oxygen-containing functional groups on its surface, and its carbon skeleton structure changed from polymeric straight chains to short-chain paraffins, cycloalkanes, and aromatics. A negative correlation was observed between the CPI value of the hydrochar derived from SPVC and the HTC temperature. The structural evolution path of the hydrochar was altered by additives, which improved its thermal reactivity. These findings are expected to play a significant role in bridging the gap from the creation of a theoretical potential energy source to the development of a sustainable alternative renewable fuel.

Chlorine Removal from Water by Biochar Derived from Various Food Waste Natural Materials

The aim of this paper was to investigate the effectiveness of pyrolyzed low-cost food waste natural materials from the food industry on the removal of chlorine from water. Biochar was produced after pyrolysis at 850 oC from malt spent rootlets (MSR), walnut shells, and apricot, olive, carob and grape kernels. The biochars were characterized for their surface area, microporosity, functional groups and pH. Continuous flow column experiments were conducted at varying flow rates to evaluate the efficiency of biochars to remove free and total chlorine. The initial free and total chlorine concentrations in water fed to the columns were 2.0 and 2.2 mg/L, respectively. The chlorine removal of free and total chlorine of all materials tested ranged from 76 to 92% and 80 to 95%, respectively, with the MSR exhibiting the highest removal. MSR biochar was subjected to the highest cumulative water volume passed through the column (162 L/g) and exhibited the highest total chlorine removal capacity (6 to 330 mg/g). Olive kernel also reached high chlorine removal (99%), while apricot kernel, grape kernel, carob seed and pulp presented poor chlorine removals.

Removal of chlorine, microparticles and water from high-viscosity liquids by a sand filter coupling hydrocyclone

Separation energy consumption in industrial production accounts for 10–15 % of global energy consumption. Nonthermal separation represented by sand filtration can open a new door to separation energy savings. Traditional sand filters cannot be regenerated completely, which limits their efficiency. A sand filter coupling hydrocyclone (SFCH) was proposed to enhance regeneration. The performance of SFCHs with different separation particle sizes was systematically analyzed, as indicated by turbidity, water, and chlorine in a pilot-scale experiment. The larger the sand particle size of the SFCH was, the longer it took to reach saturation. The efficiency and cycle were balanced by combining SFCHs with particle sizes of 1–2 mm and 0.5–1 mm. The average turbidity, water and chlorine decreased from 793 NTU, 1439 mg/L, and 126 mg/L to 155 NTU, 389 mg/L, and 88 mg/L, respectively, with a cycle of 88 h. Under the same conditions, the effluent turbidity of the SFCH was half of that of the original disc centrifuge, which indicates that the life of the downstream alumina bed was doubled. Almost 260 t/year alumina consumption can be reduced in a 200,000 tons/year-capacity petroleum resin plant, saving 600,000 USD/year, mainly due to the extension of the service life of the alumina bed.

Co-hydrothermal carbonization of polyvinyl chloride and lignocellulose biomasses for chlorine and inorganics removal

Co-hydrothermal carbonization (co-HTC) of lignocellulose biomass (LB) and chlorinated waste can simultaneously remove organic chlorine and inorganics, however, the interaction mechanisms are unclear owing to the variety of operating conditions and complexity of biomass compositions. Pine, bamboo, corncob, corn stalk, and wheat straw were co-hydrothermally carbonized with polyvinyl chloride (PVC) at the mass ratio of 9:1 for 30 min under 260 °C to explore the fundamental interactions. The synergistic index (SI) of dechlorination efficiency ranged from −20.3 % to 19.9 %, indicating the interaction depended on the content and composition of cellulose, hemicellulose, and lignin in the LB feedstocks. Hydroxyl functional groups in cellulose and soluble lignin dehydration intermediates promoted PVC substitution. The LB fragments prevented PVC aggregation while promoted PVC fragmentation, thereby facilitating dechlorination. The polyaromatic hydrochar derived from insoluble lignin and polymeric hydrochar derived from hemicellulose, cellulose, and soluble lignin can coat the surface of molten PVC and act as significant dechlorination inhibitors. All SI of removal efficiency of inorganics (RE) were positive, ranging from 0.74 % to 154 %, with large variations for different inorganics, indicating that inorganics contents in LB influenced RE significantly. A large amount of water-insoluble/acid-soluble inorganics was removed via a metathesis reaction. Soluble inorganics were dissolved in the process water by HCl leaching.

Tap Water Purification Using Pitcher Filters

Abstract Due to the high risk of exposure to various contaminants in drinking water, pitcher filtration is rapidly growing in popularity worldwide as a cheap and easy method to remove pollutants from drinking water. On the other hand, an evaluation of the real-time performance of pitchers is not possible for usual consumers. This study presents the performance of pitcher filtration in the removal of copper, chlorine, and chloroform from tap drinking water. Pitchers were packed with Aquaphor cartridges JS500, A5, and B25. Experiments were performed with model solutions, which were prepared from hard drinking water (7.5 mval/L, pH=7) spiked with copper, hypochlorite sodium, and chloroform. It was found that pitcher filtration is a very effective method for the removal of pollutants such as heavy metals, chlorine, and disinfectants byproducts. The concentration of copper, chlorine, and chloroform in filtrates did not exceed the maximum admissible values. Cartridges JS500, A5, and B25 reduced chlorine at a comparable level – almost 100%. During the whole experimental period, removal of chloroform was slightly better for JS500 (100%) and A5 (100%) cartridges than for B25 (91.4–97.7%).

Chlorine-mediated synthesis of self-exfoliated and wavy-structured graphitic carbon nitride nanosheets for enhanced photocatalytic hydrogen evolution

Graphitic carbon nitride (GCN) has drawn widespread interests in solar hydrogen production. However, the difficult exfoliation and the intrinsic shortcomings greatly restrict the hydrogen production efficiency. Herein, we report a chlorine-mediated strategy to synthesize ultrathin wavy-structured GCN nanosheets for enhancing photocatalytic activity. Chlorine is firstly doped into the melem-based oligomer; in subsequent polymerization process, self-exfoliated wavy-structured GCN are obtained owing to the effect from chlorine removal. The obtained wavy-GCN presents superior H2 evolution rate at 3372 μmol·g−1 h−1, which is 25 times higher than pristine GCN. Comprehensive characterizations reveal two main reasons for the enhanced photocatalytic activity. 1) The GCN is in-situ self-exfoliated owing to removal of doped chlorine, increasing accessible active sites. 2) The introduction of nitrogen-defects into GCN gives rise to enhanced light absorption capacity and reduced charge carriers recombination rate. This work provides a new bottom-up two-step strategy for structural regulation of GCN towards enhanced photocatalytic performance.