Chlorination Process Research Articles

Abiotic chlorination of organic matter in the soil environment: A simulation study

Chlorination of organic matter occurs naturally and is an important part of the chlorine cycle. To investigate the likelihood that inorganic oxidants, (Fe(NO3)3, H2O2, and hydroxyl radicals (·OH), frequently present in soil environments, could promote the synthesis of chlorinated organic matter in the soil environment, litterfall, humus, and soil (0–20 cm) were collected and used in laboratory based simulation experiments. Results indicate that these inorganic oxidants might promote the synthesis of chlorinated organic matter, but their impact varied due to varying suitable reaction circumstances. Litterfall was the most sensitive to chlorination, likely caused by the presence of abundant amounts of labile organic matter, and the chlorination process was limited by its Cl− level. Hydroxyl radicals showed a dual effect (producing or degrading chlorinated organic matter) on the three materials assessed, which was controlled by both ·OH concentration and the stability of organic matter, and the dual effect was evident in order of litterfall > humus > soil. The Fe(NO3)3-mediated chlorination of organic matter was only significant in litterfall due to its labile organic matter composition, while the peroxidative reaction caused by H2O2 in the producing chlorinated organic matter was only obvious in soil, most likely due to the presence of metals, facilitating the process. Combined this study sheds light on the chlorine cycle by verifying that inorganic oxidants might mediate abiotic chlorination of organic matter in a natural soil environment.

The chlorination and separation of aluminum using low-temperature sulfur chloride reagents

ABSTRACT There is currently no strategy for the permanent waste disposal or recycling for used nuclear fuels from research reactors. For this reason, low-temperature reactions have been developed for the chlorination of the Al alloys and subsequent separation from used nuclear fuels to reduce the volume of high-level waste in storage. Three sulfur chloride reagents – S2Cl2, SOCl2, and SO2Cl2—were tested, and two were found to quantitatively chlorinate Al metal and Al alloys under mild conditions. These low-temperature reactions proceed between 298 and 411 K, and up to 5 g of metal is chlorinated in 1–3 h. Preliminary results indicate that the reactivity and exothermicity of the reaction between the Al and sulfur chloride reagents is highly dependent on the surface area-to-volume ratio of the metal and the volume of solvent. Elemental S is produced as a by-product during the chlorination with S2Cl2 but can be quantitatively rechlorinated under mild conditions to regenerate the initial chlorination reagent. Therefore, in this case, chlorine is the only element consumed in the reaction, thus minimizing the waste generated during the chlorination process. The AlCl3 may then be separated from other materials present in Al 6061 or Al 8001 because of its high solubility in the sulfur chloride reagents. This process may also be extended to chlorinate Al from research reactor fuels.

Action of chlorine, peracetic acid, UV-LED radiation, and advanced oxidation process on Giardia lamblia cysts for reclaimed water production

Action of chlorine, peracetic acid, UV-LED radiation, and advanced oxidation process on Giardia lamblia cysts for reclaimed water production

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.

Insights into the enhancement of trace level NO2− on 2,4,6-tribromophenol degradation in UV/PS process: Experimental study and theoretical calculation

Sulfate radical (SO4−)-based UV/persulfate (PS) process is extensively studied to remove organic pollutants in water, while the wide presence of nitrite (NO2−) in natural water can quickly react with SO4− and hydroxyl radicals (OH) to form reactive nitrogen species (RNS). In this study, the degradation of 2,4,6-tribromophenol (TBP) in UV/PS process in the presence of low concentration of NO2− was systematically investigated through experimental studies and theoretical calculations. The introduction of trace NO2− enhanced the TBP degradation by UV/PS process due to the formation of RNS (such as NO2 and BrNO2) and both RNS and SO4− played the important role in the pH range of 6.0–8.0. TBP was more easily photolyzed under alkaline conditions due to higher photodegradation coefficient at pH 8.0. When TBP underwent deprotonation, the reaction energy barrier of TBP with SO4−, OH and NO2 significantly decreased and subsequent debromination may be more likely to occur. Additionally, NO2 attacked ionized TBP at relatively high rate mainly through electron transfer. The degradation pathways of TBP mainly involved in the debromination, hydroxylation and nitrosylation and the generated products all presented lower toxicity than TBP. Moreover, the effects of PS dosage, NO2− concentration, humic acid, bicarbonate and chloride on TBP elimination also were thoroughly assessed. The presence of low concentration of NO2− reduced the toxicity risk caused by the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) during the chlorination process after UV/PS pre-oxidation. This study broadens the knowledge of trace NO2− enhancing organic pollutants degradation by UV/PS process.

A convenient reduction method for the detection of low concentration free available chlorine——utilizing sodium sulfite as a quencher

Chlorine, serving as the mainstream disinfectant, can react with dissolved organic matter (DOM) to form undeserved disinfection by-products (DBPs). Free available chlorine (FAC) concentration is crucial to ensure effective disinfection while minimizing the formation of toxic DBPs. In this study, we propose a convenient method using sodium sulfite (Na2SO3) to reduce oxidized chlorine in FAC. The molar concentration of reduced chloride ion (Cl−) was quantified directly by ion chromatography to reflect FAC concentration. Compared with common FAC detection techniques including DPD colorimetry, iodometry, and UV methods, this novel reduction method exhibits a lower detection limit and is more resistant to interference. Common water matrices, such as DOM and anions did not affect the method accuracy (< 3.6%). Furthermore, carbonaceous DBPs (C-DBPs) like regulated trihalomethanes and halogenacetic acids, unregulated aromatic chlorophenols, did not interfere with the determination of FAC by using this reduction method. This lack of interference can be attributed to the low redox potential of Na2SO3, which does not readily react with these C-DBPs. However, nitrogenated DBPs (N-DBPs) like dichloroacetonitrile displayed slight interference (the effect of common dichloroacetonitrile concentration in water on FAC was less than 0.0007 μM). This suggests that this method is well-suited for determining FAC in chlorination processes where the C-DBPs predominated. Overall, the reduction method enables precise determination of FAC and proves valuable in assessing residual chlorine levels in both laboratory and real disinfected water samples dominated by C-DBPs.

Chlorination of Biopterin in Water: Deciphering the Kinetics, Disinfection Byproducts, and Toxicity.

Pterins, including biopterin prevalent during cyanobacterial blooms, are nitrogen-containing heterocyclic compounds ubiquitous in both natural and engineered environments. However, their roles and associated human risks in water treatment remain poorly understood. This study systematically investigated the kinetics, disinfection byproducts (DBPs), and toxicity of biopterin in chlorination. For deciphering the reaction kinetics, 1,3,5-trimethoxybenzene proved to be a more effective chlorine quencher than the commonly used reducing agents, as it preserved N-chlorinated intermediates without reversing them back to biopterin. The pH-dependent kinetics demonstrated that both chlorine and biopterin species had a significant influence on the reaction rates, with deprotonated biopterin exhibiting a markedly higher reactivity toward HClO/ClO-. Based on time-of-flight mass spectrometry, ten transformation products (TPs) including seven halogenated N-Cl ones, have been identified for the first time. These cyclic TPs were transformed into various aliphatic carbonaceous and nitrogenous DBPs during the subsequent chlorination process. Notably, theoretical predictions and the luminescent bacteria assay confirmed potential higher toxicities of these products than biopterin. These findings highlight the potential risks of pterins during water disinfection and provide a reference framework for accurately revealing the chlorination behavior of emerging nitrogenous chemicals.

Formation and estimated cytotoxicity of trihalomethanes and haloacetic acids during ozonation of nonylphenol in bromide-containing water after chlorination process: Impact of ozonation initial pH

The presence of nonylphenol (NP) in bromide-containing water contributed to the formation of regulated disinfection by-products (DBPs): trihalomethanes-4 (THM4) and haloacetic acids-5 (HAA5). This study investigates the effects of ozonation pH on the degradation of NP, DBP formation, and DBP-estimated cytotoxicity. The ozonation pH was varied to 5, 7, and 9 to determine the effect of acidic, neutral, and alkaline conditions. The increase of ozonation initial pH improved the NP degradation. Ozonation of all initial pH conditions could decrease TCM, BDCM, and BDCM formation but increase the TBM formation at alkaline conditions. The formation of mono-HAA5 on the other hand, increased at all ozonation initial pH. Ozonation at acidic and neutral initial conditions can reduce the estimated cytotoxicity of the total formation of THM4 and HAA5 by 74.34 % and 93.31 %, respectively. In contrast, DBP's estimated cytotoxicity was raised by 33.72 % upon ozonation at an initial pH of alkaline. According to the study's findings, lowering the cytotoxicity of DBPs in acidic or alkaline environments can be achieved without changing the ozonation's pH. Based on these findings, pH changes are not required to reduce DBP during ozonation of NP-bromide-containing water. Future research on the impact of natural organic matter is recommended to investigate ozonation's capacity to reduce DBP production during ozonation of NP-containing natural water.

Novel catalyst-free activation of chlorine by visible light for micropollutant abatement

This study systematically investigated the direct activation of chlorine by visible light emitting diode (Vis-LED). Vis-LED could effectively activate chlorine to degrade micropollutants with degradation efficiency and pseudo-first-order degradation rate constant range of 64.3–100 % and 0.0340–0.195 min−1, respectively. Quenching experiments and modeling results suggested that reactive chlorine species (RCS, including ClO•, Cl2•-, and Cl•) and hydroxyl radical (•OH) were involved in the degradation of atenolol (ATL). The contribution ratio of ClO•, free available chlorine, Cl•, Cl2•-, and •OH to ATL degradation were 58.7 %, 17.4 %, 15.6 %, 1.8 %, and 5.9 %, respectively, in Vis-LED448/chlorine process. Moreover, the innate quantum yields of HClO and ClO- decreased from 0.229 and 0.0206 to 0.0489 and 0.0109 mol·Einstein−1, respectively, as the wavelength increased from 448 to 513 nm, leading to a decrease in ATL degradation, which was consistent with the model results. Experimental and modeling results have confirmed that ATL degradation decreased when pH increased from 4.0 to 9.0. Cl- had little effect on the degradation of ATL, while HA and HCO3- affected ATL degradation by scavenging reactive species and/or shielding effect. The concentration of disinfection by-products decreased with the increase of wavelength and pH. In summary, Vis-LED/chlorine is an efficient water treatment process even without a catalyst.

Development of the novel advanced electrooxidation process for decolorization of recalcitrant dyes (Methylene Blue, Rhodamine B, Congo Red): Effect of operating factors

The research aims to develop an advanced electrooxidation process for decolorization of recalcitrant dye. To enhance the radical formation, a combination of UV irradiation and electrooxidation (UV/EO) is used. Methylene Blue (MB), Rhodamine B (RB) and Congo Red (CR) dyes were used as model compounds to represent recalcitrant dyes. The performance of UV/EO process was investigated under various operating factors (i.e., current density (CD), voltage, pH, NaCl, anodic material), and compared with chlorination, UV irradiation, and electrooxidation (EO) process. MB was the highest resistant dye to the UV/EO process. The UV/EO process exhibited a synergistic effect on decolorization, and it removed MB 1.35 time faster than the EO process. Based on indirect determination of •OH, the •OH formation in the EO process was 2.4 ×10−13 M, which lower than that in the UV/EO process by 4 times. The second-order rate constant for MB oxidation by HO• (kHO•,MB) was 3.31 × 109 M−1s−1. The pseudo 1st-order decolorization kinetic (k’) was independent with voltages, but directly depended on CD and NaCl concentrations. Lower pH enhanced the k’ value. The specific energy consumption was in a range of 0.408 – 5.303 kWh/m3, depending on the k’ value. The energy consumption decreased with higher the k’ value, except for increasing CD. The Boron Doped Diamond (BDD) was more effective in the decolorization rate than dimensional active anode (DSA) by 1.6 times. Treatment of industrial dye wastewater by the UV/EO process eliminated color intensity (ADMI), COD, and BOD5 by 80 %, 91 %, and 9 %, respectively.

Transformation of dissolved organic matter leached from biodegradable and conventional microplastics under UV/chlorine treatment and the subsequent effect on contaminant removal

The ultraviolet (UV)/chlorine process has been widely applied for water treatment. However, the transformation of microplastic-leached dissolved organic matter (MP-DOM) in advanced treatment of real wastewater remains unclear. Here, we investigated alterations in the photoproperties of MP-DOM leached from biodegradable and conventional microplastics (MPs) and their subsequent effects on the degradation of sulfamethazine (SMT) by the UV/chlorine process. Spectroscopy was used to assess photophysical properties, focusing on changes in light absorption capacity, functional groups, and fluorescence components, while photochemical properties were determined by calculating the apparent quantum yields of reactive intermediates (ΦRIs). For photophysical properties, our findings revealed that the degree of molecular structure modification, functional group changes, and fluorescence characteristics during UV/chlorine treatment are closely linked to the type of MPs. For photochemical properties, the ΦRIs increased with higher chlorine dosages due to the formation of new functionalities. Both singlet oxygen (1O2) and hydroxyl radicals (•OH) formation were strongly correlated with excited triplet state of DOM (3DOM*) in the UV/chlorine treatment. Additionally, we found that the four types of MP-DOM inhibit the degradation of SMT and elucidated the mechanisms behind this inhibition. We also proposed degradation pathways for SMT and assessed the ecotoxicity of the resulting intermediates. This study provides important insights into how the characteristics and transformation of MP-DOM affect contaminant degradation, which is critical for evaluating the practical application of UV-based advanced oxidation processes (UV-AOPs).

Extraction and characterization of cellulose from agricultural waste of hemp (&lt;i&gt;Cannabis sativa)&lt;/i&gt; and parthenium (&lt;i&gt;Parthenium hysterophorus)&lt;/i&gt;

The current study focused on the extraction of cellulose from two selected plants, hemp (Cannabis sativa) and parthenium (Parthenium hysterophorus). The research successfully isolated high-purity cellulose from both plants using a chlorination and alkaline extraction process. A higher yield (%) (38.4 ± 0.18) was obtained from hemp compared to parthenium (22 ± 0.82). Characterization techniques were used to probe the structure and properties of the extracted cellulose. Fourier transform infrared spectroscopy analysis revealed functional groups characteristic of cellulose, while X-ray diffraction confirmed its highly crystalline structure in both samples. Scanning electron microscopy provided valuable insights into the cellulose morphology, indicating a smoother surface and reduced fiber diameter after treatment due to the removal of noncellulosic components. The research paved the way for the development of eco-friendly bioproducts utilizing cellulose from hemp and parthenium, promoting a more sustainable future.

NCS-Mediated Direct C(sp3)-H Oxygenation of 2-Methylindoles Using Water as the Oxygen Source.

In continuation of our research interest in the green oxidation of indoles, we further explore the direct oxidation of 2-methylindoles to 2-formyl indoles promoted by NCS and associated with H2O as the oxygen source. This methodology was demonstrated to be a robust protocol consisting of chlorination, SN2', and oxidation processes, and presents a reasonably broad substrate scope and excellent functional group tolerance, thus enabling the preparation of high added-value versatile building blocks susceptible to further functionalization.

Novel Strategy for Efficient Recovery of CuO-Based Multiple-Metals from Copper Smelter Dust toward CO2 Electrocatalytic Reduction.

Copper smelter dust, a typical hazardous waste that is abundant in valuable heavy metals, holds the potential to be regarded as a promising resource. This study introduces a new approach that integrates chlorination roasting and cascade condensation to efficiently recover heavy metals from copper smelter dust. The findings demonstrate the successful separation of heavy metals (Cu, Pb, and Zn) as chlorides at nearly 100% efficiency while also effectively converting trivalent arsenic (As(III)) into pentavalent arsenic (As(V)) and immobilizing it in the roasting residues, thereby reducing environmental risk. Through the utilization of thermogravimetric mass spectrum analysis and thermodynamic equilibrium calculations, the chlorination process for heavy metals was investigated, revealing both direct and indirect chlorination processes. Additionally, the study resulted in the development of a CuO-based multiple-metals electrocatalyst from the oxidized roasting-recovered heavy metal chlorides, exhibiting significantly enhanced catalytic activity and faradaic efficiency for the electroreduction of CO2 into CO and CH4 compared to pure CuO electrocatalyst under similar electrocatalytic conditions. Overall, this work presents a sustainable and scalable method and new insights for addressing environmental risks while repurposing copper smelter dust.

Stratospheric Chlorine Processing After the Unprecedented Hunga Tonga Eruption

AbstractFollowing the Hunga Tonga–Hunga Ha'apai (HTHH) eruption in January 2022, significant reductions in stratospheric hydrochloric acid (HCl) were observed in the Southern Hemisphere mid‐latitudes during the latter half of 2022, suggesting potential chlorine activation. The objective of this study is to comprehensively understand the loss of HCl in the aftermath of HTHH. Satellite measurements and a global chemistry‐climate model are employed for the analysis. We find strong agreement of 2022 anomalies between the modeled and the measured data. The observed tracer‐tracer relations between nitrous oxide (N2O) and HCl indicate a significant role of chemical processing in the observed HCl reduction, especially during the austral winter of 2022. Further examining the roles of chlorine gas‐phase and heterogeneous chemistry, we find that heterogeneous chemistry emerges as the primary driver for the chemical loss of HCl, and the reaction between hypobromous acid (HOBr) and HCl on sulfate aerosols is the dominant loss process.

An Efficient and Eco-Friendly Recycling Route of Valuable Metals from Spent Ternary Li-Ion Batteries: Kinetics Evaluation of Chlorination Processes and Regeneration of LiNi0.8Co0.1Mn0.1O2 Cathode Materials.

The recycling of spent Li-ion batteries is urgent, and the effective recovery of valuable metals from spent cathode material is an economic and eco-friendly approach. In this study, Ni, Cu, Co, and Mn were extracted synchronously from spent LiNixCoyMn1-x-yO2 by chlorination and the complexation reaction of ammonium chloride at low temperatures. The kinetics of the chlorination process was investigated by nonisothermal thermal analysis to determine the rate equation of metal conversion, and the apparent activation energies were calculated to be 99.96 kJ·mol-1 for lithium and 146.70 kJ·mol-1 for nickel, cobalt, and manganese, respectively. The separation of valuable metals from polymetallic leaching solution and the regeneration of cathode materials were further investigated to promote the industrialization of the process. The recoveries of Ni, Co, Mn, and Li can reach 97.75, 99.99, 99.99, and 92.23%, respectively. The prepared LiNi0.8Co0.1Mn0.1O2 precursor is a multilayer spherical particle formed by stacking primary hexagonal nanosheets along the (010) crystal axis, the formation mechanism of which was discussed. The effect of temperature, time, and mixed lithium ratio on the performance of single crystal LiNi0.8Co0.1Mn0.1O2 cathode in the synthesis process was investigated to determine the optimum conditions. Compared with commercial materials, the prepared single crystal LiNi0.8Co0.1Mn0.1O2 cathode has a more regular crystal structure and higher initial discharge capacity (215.9 mAh·g-1 at 0.1 C).

Impacts of chloride ions on the electrochemical decomplexation and degradation of Cr(III)-EDTA: Reaction mechanisms of HO• and RCS

The removal of Cr(III)-organic complexes, encompassing both decomplexation and ligand degradation, presents significant challenges in industrial wastewater treatment. As one of the most common anions in wastewater, Cl− significantly improves the efficiency of electrochemically removing Cr(III)-organic complexes through generated reactive chlorine species (RCS). In the electrochemical chlorine (EC/Cl2) process, extensive experimentation revealed that ClO• plays a dominant role in the degradation of Cr(III)-EDTA, surpassing the effects of free chlorine, direct electrooxidation, HO•, and other RCS. Density functional theory calculations indicated that RCS, primarily Cl• and ClO•, preferentially oxidize the ligand in Cr(III)-EDTA via H-abstraction, whereas HO• trends to attack the Cr atom through electron transfer. The influential factors on the degradation efficiency of Cr(III)-EDTA, Cr(VI) yield, and total organic carbon removal in EC/Cl2 were also assessed, including Cl− concentration, current density, and pH. Real industrial wastewater was employed as a reaction matrix to evaluate the application of the EC/Cl2 process for treating Cr(III)-EDTA, accompanied by energy efficiency calculations. Additionally, a two-chamber reactor was established to simultaneously oxidize Cr(III)-EDTA at the anode and reduce Cr(VI) at the cathode. This study provided insight into developing RCS-dominated AOPs to effectively decomplex and decompose organic Cr(III)-complexes in Cl−-containing industrial wastewater.

Femtosecond laser technology: A new approach for water disinfection

Water makes up around 60 % of the body, making it essential to all body systems and crucial to human health and survival. The lack of clean drinking water is currently a problem in many different countries. While there are several approaches for disinfecting drinking water, including the widely used ozonation, UV irradiation, and chlorination processes, each has some drawbacks. The purpose of this study is to evaluate the effectiveness of femtosecond laser technology in disinfecting water polluted with Escherichia coli (E. coli), for the first time. Bacterial cells were exposed to a femtosecond laser light with different wavelengths, intensities, and exposure times. E. coli was subjected to femtosecond laser irradiation for 5, 10, 15, 30, and 45 min at different powers of 50, 100, and 200 mW. Femtosecond laser light, ranging from 400 to 800 nm in wavelengths, was used to irradiate E. coli bacteria. These wavelengths cover the ultraviolet, visible, and infrared spectra. Under these experimental settings, the concentration of E. coli bacteria (in CFU/ml) was instantly determined using the MTT assay. Bacterial growth was dramatically decreased to 45.2 CFU/ml (%) after 45 min of exposure to 400 nm wavelength and 200 mW averaged power. The results obtained in this study provide evidence to conclude that femtosecond laser irradiation dramatically suppresses E. coli growth. Without making direct chemical contact, femtosecond laser irradiation offers a possible remote water disinfection approach. Therefore, the femtosecond laser light could be used for water disinfection as a promising eco-friendly technique.

Homogeneous versus heterogeneous Mn(II) oxidation in peroxymonosulfate assisting chlorination: Synergistic role for enhanced Mn(II) oxidation in water treatment

Removal of Mn(II) is an essential step for addressing water discoloration in water treatment utilities worldwide. However, conventional chlorination suffers from poor oxidation of Mn(II) due to its low homogeneous oxidation kinetics. This study explored the oxidation capability of a new chemical dosing strategy employing peroxymonosulfate (PMS) to assist the chlorination process (PMS@Cl2) for effective Mn(II) oxidation. The study comprehensively explored both oxidation kinetics and underlying mechanisms associated with homogeneous and heterogeneous oxidation within the PMS@Cl2 system. At an [Mn(II)]0 of 1 mg/L, chlorination demonstrated inability in oxidizing Mn(II), with <10 % oxidation even at an elevated [Cl2] of 150 μM (∼10 mg/L). By contrast, PMS completely oxidized 100 % Mn(II) within a 30-minute reaction at a much lower [PMS] of 60 μM (kobs = 0.07 min−1 and t1/2 = 9 min), demonstrating its superior Mn(II) oxidation kinetics (over one order of magnitude faster than conventional chlorine). PMS@Cl2 exhibited an interesting synergistic benefit when combining a lower dose PMS with a higher routine dose Cl2 (loPMS@hiCl2), e.g. [PMS]:[Cl2] at 15:30 or 30:30 μM. Both conditions achieved 100 % Mn(II) oxidation, with even better values of kobs and t1/2 (0.16–0.17 min−1 and ∼4 min) relative to PMS alone at 60 µM. The synergic benefit of PMS@Cl2 was attributed to distinct functions played by PMS and Cl2 in both homogeneous and heterogeneous oxidation processes. Reactive species identification excluded the possible involvement of SO4•−, OH•, or chlorine radicals in the homogeneous oxidation of the PMS@Cl2 system. Instead, the dominant species was O2•− radical generated during the reaction of Mn(II) and PMS. Furthermore, the heterogeneous oxidation emphasized the important role of combining Cl2 dosing, which demonstrated an increased reactivity and electron transfer with the Mn−O−Mn complex, surpassing PMS. Overall, heterogeneous oxidation accelerated the oxidation kinetics of the PMS@Cl2 system by 1.1–2 orders of magnitude relative to the homogeneous oxidation of Cl2 alone. We here demonstrated that PMS@Cl2 could offer a more efficient mean of soluble Mn(II) mitigation, achieved with a relatively low routine dose of oxidant in a short reaction period. The outcomes of this study would address the existing limitations of traditional chlorine oxidation, minimizing the trade-offs associated with high residual chlorine levels after treatments for soluble manganese-containing water.

Study on the influence of temperature on a baddeleyite concentrate chlorination process

Study on the influence of temperature on a baddeleyite concentrate chlorination process