Chlorine reactivity

The combination of chlorine and UV (i.e. chlorine-UV process) has been attracting more attentions in recent years due to its ready incorporation into existing water treatment facilities to remove PPCPs. However, limited information is available on the impact of total ammonia nitrogen (TAN). This study investigated two model PPCPs, N,N-diethyl-3-toluamide (DEET) and caffeine (CAF), in the two stages of chlorine-UV process (i.e. chlorination and UV/chlor(am)ine) to elucidate the impact of TAN. During chlorination, the degradation of DEET and CAF was positively correlated with the overall consumption of total chlorine by TAN...

Layered FeII-FeIII hydroxide chloride (chloride green rust, GRCl) has high reactivity towards reducible pollutants such as chlorinated solvents. However, this reactive solid is prone to dissolution, and hence loss of reactivity during storage and handling. In this study, adsorption of silicate (Si) to GRCl was tested for its ability to minimize GRCl dissolution and to inhibit reduction of carbon tetrachloride (CT). Silicate adsorbed with high affinity to GRCl yielding a sorption maximum of 0.026 g Si per g GRCl...

Titania nanotube (TNT) powder was prepared by rapid breakdown anodization (RBA) in a perchloric acid electrolyte. The photocatalytic efficiency of the as-prepared and powders annealed at temperatures between 250 and 550 °C was tested under UV and natural sunlight irradiation by decolorization of both anionic and cationic organic dyes, i.e., methyl orange (MO) and rhodamine B (RhB), as model pollutants. The tubular structure of the nanotubes was retained up to 250 °C, while at 350 °C and above, the nanotubes transformed into nanorods and nanoparticles...

Nanocarrier-mediated photodynamic therapy (PDT), which involves the systemic delivery of photosensitizers (PSs) into tumor tissue and tumor cells, has emerged as an attractive treatment for cancer. However, insufficient PS release limits intracellular cytotoxic reactive oxygen species (ROS) generation, which has become a major obstacle to improving the PDT therapeutic efficacy. Herein, a novel hyperbranched polyphosphoester (hbPPE) containing numerous acetal bonds (S-hbPPE/Ce6) was explored as a chlorin e6 (Ce6) nanocarrier for PDT...

Chloropicrin (CCl3NO2) is widely used in agriculture as a pesticide, weed-killer, fungicide or nematicide. It has also been used as chemical agent during World War I. The precise understanding of its combustion chemistry for destruction processes or in the event of accidental fire of stored reserves is a major safety issue. A detailed chemical kinetic model for the combustion and pyrolysis of chloropicrin is proposed for the first time. A large number of thermo-kinetic parameters were calculated using quantum chemistry and reaction rate theory...

Seasonal algal blooms in freshwater and marine water can increase the input of algal organic matter (AOM) to the pool of dissolved organic matter. The impact of bromide (Br- ) and iodide (I- ) on the formation of regulated and unregulated disinfection byproducts (DBPs) was studied from chlorination of AOM solutions extracted from three species of cultured isolates of freshwater and marine algae (Microcystis aeruginosa (MA), Synechococcus (SYN), and Alexandrium tamarense (AT)). Comparable concentrations of DBPs were formed from three types of AOM...

The survivability of viruses in natural and engineered systems impacts public health. Inactivation mechanisms in the environment have been described for nonenveloped viruses, but it remains unclear how the membrane layer of enveloped viruses influences inactivation. We applied molecular tools and high-resolution mass spectrometry to measure reactions in the genome, proteins, and lipids of enveloped Pseudomonas phage Phi6 during inactivation by free chlorine and UV254 . Free chlorine readily penetrated the lipid membrane to react with proteins in the nucleocapsid and polymerase complex...

Oxygen (O2 ) plays a critical role during photodynamic therapy (PDT), however, hypoxia is quite common in most solid tumors, which limits the PDT efficacy and promotes the tumor aggression. Here, a safe and multifunctional oxygen-evolving nanoplatform is costructured to overcome this problem. It is composed of a prussian blue (PB) core and chlorin e6 (Ce6) anchored periodic mesoporous organosilica (PMO) shell (denoted as PB@PMO-Ce6). In the highly integrated nanoplatform, the PB with catalase-like activity can catalyze hydrogen peroxide to generate O2 , and the Ce6 transform the O2 to generate more reactive oxygen species (ROS) upon laser irradiation for PDT...

In this study, significant synergistic degradation of antibiotic diclofenac (DCF) was demonstrated in a novel magnetic field (MF) enhanced zero-valent iron (ZVI)/EDTA Fenton-like system. Five operational parameters, namely, initial ZVI loading, pH, EDTA dosage, DCF concentration and reaction temperature, were investigated for their effects on the DCF degradation. OH was identified as the predominant reactive oxygen species for DCF degradation in ZVI/EDTA systems whether in the presence or absence of MF. DCF molecule can be oxidized by OH, attacking via the hydroxylation and substituted dechlorination of the chlorinated aromatic ring, as well as by dehydration between the N atom and the acetoxyl...

The aim of this study is to evaluate the micropollutant removal capacity of a 275 nm light-emitting diode (LED)-UV/chlorine system. The sulfamethoxazole, ibuprofen, and nitrobenzene removal efficiencies of this system were compared with those of a conventional 254 nm low-pressure (LP)-UV system as a function of the UV dose. In a direct photolysis system, the photon reactivity of sulfamethoxazole is higher than that of nitrobenzene and ibuprofen at both wavelengths. The molar absorption coefficients and quantum yields of each micropollutant were as follows: sulfamethoxazole (εSMX, 275 nm protonated  = 17,527 M-1  cm-1 , ΦSMX, 275 nm protonated  = 0...

A practical meta C-H chlorination protocol is established via a Ru(0)-catalyzed ortho-metalation strategy. The use of N-chloro-2,10-camphorsultam as a new chlorinating agent is crucial for the success of the current reaction and an N-heterocyclic carbene (NHC) ligand could significantly enhance the reactivity of the catalytic transformation. The mechanistic studies reveal that an unusual ortho C-H ruthenation relay process with ortho chlorination of the C-Ru bond is probably involved.

Cancer cells in hypoxic tumors are remarkably resistant to photodynamic therapy. Here, we hypothesize that an oxygen and Pt(II) self-generating multifunctional nanocomposite could reverse the hypoxia-triggered PDT resistance. The nanocomposite contains Pt(IV) and chlorin e6, in which upconversion nanoparticles are loaded to convert 980 nm near-infrared light into 365 nm and 660 nm emissions. Upon accumulation at the tumor site, a 980 nm laser is used to trigger the nanocomposite to generate O2 for consumption in the PDT process and to produce cytotoxic reactive oxygen species...

Living drug delivery system has been proposed as new concept materials since it is able to communicate with biological system, sense subtle changes of body microenvironment caused by disease and then make rapid response to cure in early stage of disease. Herein, taking full advantage of the tumor hypoxia physiology and successive effects of photodynamic therapy (PDT), we designed a new living delivery system via combining the PDT and hypoxia-responsive chemotherapy, abbreviated as Ce6-PEG-Azo-PCL. Then, according to the facts that oxygen can be converted into reactive oxygen species during irradiation of the photosensitizer, tumor cells could be killed after the poly(ethylene glycol) (PEG) conjugated photosensitizer chlorine e6 were irradiated at tumor site...

Oxidative stresses, such as reactive oxygen species, reactive electrophilic species, reactive nitrogen species, and reactive chlorine species, can damage cellular components, leading to cellular malfunction and death. In response to oxidative stress, bacteria have evolved redox-responsive sensors that enable them to simultaneously monitor and eradicate potential oxidative stress. Specifically, redox-sensing transcription regulators react to oxidative stress by means of modifying the thiol groups of cysteine residues, functioning as part of an efficient survival mechanism for many bacteria...

Residual chlorine is often required to remain present in public drinking water supplies during distribution to ensure water quality. It is essential to understand how bacteria respond to long-term chlorine exposure, especially with the presence of assimilable organic carbon (AOC). This study aimed to investigate the effects of chlorination on Pseudomonas aeruginosa in low AOC medium by both conventional plating and culture-independent methods including flow cytometry (FCM) and quantitative PCR (qPCR). In a simulated chlorinated system using a bioreactor, membrane damage and DNA damage were measured by FCM fluorescence fingerprint...

Regioselective chlorination of cellulose is challenging due to its low reactivity, the small reactivity differences between cellulosic hydroxyl groups, and the high and diverse reactivity of most common chlorinating agents. Halogenation of cellulose affords useful precursors for subsequent nucleophilic substitution reactions, permitting incorporation of new functionality. Herein we report a simple and efficient pathway for preparation of 6-chloro-6-deoxycellulose esters and their derivatives. Cellulose acetate (degree of substitution (DS) 1...

With an objective to develop efficient sensitizers for therapeutical applications, we synthesized a water soluble, 5,10,15,20-tetrakis(3,4-dihydroxyphenyl)chlorin (TDC), and investigated its in vitro and in vivo biological efficacy and compared with the commercially available sensitizers. TDC showed high water solubility (6-fold), when compared to Foscan and exhibited excellent triplet excited state () and singlet oxygen () yields. In vitro photobiological investigations in human ovarian cancer cell lines SKOV-3 showed high photocytotoxicity, negligible dark toxicity, rapid cellular uptake and specific localization of TDC in neoplastic cells as assessed by flow cytometric cell-cycle and propidium iodide staining analysis...

Photodynamic therapy (PDT) has increasingly become an efficient and attractive cancer treatment modality based on reactive oxygen species (ROS) that can induce tumor death after irradiation with ultraviolet or visible light. Herein, to overcome the limited tissue penetration in traditional PDT, a novel near-infrared (NIR) light-activated NaScF4 : 40% Yb, 2% Er@CaF2 upconversion nanoparticle (rUCNP) is successfully designed and synthesized. Chlorin e6, a photosensitizer and a chelating agent for Mn2+ , is loaded into human serum albumin (HSA) that further conjugates onto rUCNPs...

This modeling study aims to investigate how reactive processes in aquitards impact plume persistence in adjacent aquifers. For that purpose the migration of a trichloroethene (TCE) plume in an aquifer originating from dense non-aqueous phase liquid (DNAPL) source dissolution and back-diffusion from an underlying reactive aquitard was simulated in a 2D-numerical model. Two aquitard degradation scenarios were modeled considering one-step degradation from TCE to cis-dichloroethene (cDCE): a uniform (constant degradation with aquitard depth) and a non-uniform scenario (decreasing degradation with aquitard depth) and were compared with a no-degradation scenario...

Mesoporous silica nanoparticles (MSNs) with stimuli-responsive gatekeepers have been extensively investigated for controlled drug delivery at the target sites. Herein, we developed reactive oxygen species (ROS)-responsive MSNs (R-MSNs), consisting of a gadolinium (Gd)-DOTA complex as the ROS-responsive gatekeeper and polyethylene glycol (PEG)-conjugated chlorin e6 as the ROS generator, for magnetic resonance (MR) imaging-guided photodynamic chemotherapy. Doxorubicin (DOX), chosen as an anticancer drug, was physically encapsulated into DOTA-conjugated MSNs, followed by chemical crosslinking via the addition of GdCl3...