Determination of bromide ions in seawater using flow system with chemiluminescence detection

Unexpected trends for the formation of chlorate and bromate during the photolysis of chlorine in bromide-containing water

Solar photolysis of free chlorine (solar/chlorine) in bromide-containing water occurs under various scenarios, such as chlorinated reservoirs and outdoor swimming pools, and the formation of chlorate and bromate is an important issue in the system. We reported unexpected trends for the formation of chlorate and bromate in the solar/chlorine system. Excess chlorine inhibited the formation of bromate, i.e., increasing chlorine dosages from 50 to 100 μM reduced the bromate yield from 6.4 to 1.2 μM in solar/chlorine at 50 μM bromide and pH 7. The yield of bromate in solar/chlorine at 100 μM chlorine and 50 μM bromide in 240 min was 18.8% of that at 50 μM bromine only. The underlying mechanism was that HOCl can react with bromite (BrO₂^-) to form HOClOBrO^-, whose multi-step transformation finally formed chlorate as the major product and bromate as the minor product. This reaction overwhelmed the oxidation of bromite to form bromate by reactive species, such as ^•OH, BrO^• and ozone. On the other hand, the presence of bromide greatly enhanced the formation of chlorate. Increasing bromide concentrations from 0 to 50 μM enhanced the chlorate yields from 2.2 to 7.0 μM at 100 μM chlorine. The absorbance of bromine was higher than that of chlorine, thus the photolysis of bromine formed higher levels of bromite at higher bromide concentrations. Then, bromite rapidly reacted with HOCl to form HOClOBrO^- and it further transformed to chlorate. Additionally, 1 mg L^-1 NOM had a negligible effect on bromate yields in solar/chlorine at 50 μM bromide, 100 μM chlorine and pH 7. This study demonstrated a new pathway of chlorate and bromate formation in the solar/chlorine system with bromide.

Adsorption of low concentrations of bromide ions from water by cellulose-based beads modified with TEMPO-mediated oxidation and Fe(III) complexation

Due to strong activity, it is very difficult to remove low concentrations of bromide in medical wastewater by traditional method, thus highly effective and greener adsorbents should be utilized to design. In this work, the cellulose beads (CBs) were modified by the TEMPO-mediated oxidation and then bonded with Fe³⁺ to fabricate Fe(III)-complexed carboxylated cellulose beads (Fe-CCBs) adsorbents. Structure and properties of Fe-CCBs were analyzed using Energy dispersive spectrum (EDS), Scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), total acidity and basicity groups, X-ray diffraction (XRD), N₂ adsorption-desorption and Thermogravimetric (TGA). Moreover, batch adsorption experiments showed that the adsorption of Br^- was better consistent with general-order kinetic model and Liu isotherm model, which could also further clarify the adsorption process mechanism. Meanwhile, the results revealed that removal of Br- was a spontaneous exothermic process and was more suitable to be carried out under neutral or acidic conditions. Furthermore, the mechanism of adsorption behavior of bromide ions on Fe-CCBs was based on a combination of electrostatic attraction and outer-sphere complexation. The results of this study can provide guidance for the design of novel material adsorbents and the removal of harmful anions from aqueous solutions.

Low concentration of 2,4,6-tribromophenol (TBP) represents a risk to South American silver catfish Ramdia quelen (Quoy and Gaimard, 1824) population

The 2,4,6-tribromophenol (TBP) is an environmental persistent pollutant widely used as flame retardant, antimicrobial and insecticide agent in wood preservation and plastic production. Currently, TBP is found in environmental compartments such as soil, freshwater, groundwater, sewage sludge and domestic dust, but the effects to biota and the risk of exposure to aquatic vertebrates are still scarce. In the present study, Rhamdia quelen fish embryos (8 h post-fertilization - hpf) were exposed to 0.3 and 3.0 μg L^-1 of TBP until 96 hpf. Biochemical biomarkers, hatching, survival and larvae/embryo malformations were evaluated after exposure. Additionally, a mathematical model was proposed to evaluate the effects along further generations. The results showed that TBP decreased the survival level but did not cause significant difference in the hatching rates. After 72 and 96 hpf, individuals from the highest tested concentration group showed more severe malformations than individuals from control and the lower concentrations groups. The deformities were concentrated on the embryos facial region where the sensorial structures related to fish behavior are present. The biochemical biomarkers revealed both oxidative stress and neurotoxicity signs after exposure to the contaminant, while the application of the mathematical model showed a decrease of population in both tested TBP concentrations. In conclusion, the current results demonstrated that TBP is toxic to R. quelen embryos and represents a risk to population after early life stage exposure.

Regulation, formation, exposure, and treatment of disinfection by-products (DBPs) in swimming pool waters: A critical review

The microbial safety of swimming pool waters (SPWs) becomes increasingly important with the popularity of swimming activities. Disinfection aiming at killing microbes in SPWs produces disinfection by-products (DBPs), which has attracted considerable public attentions due to their high frequency of occurrence, considerable concentrations and potent toxicity. We reviewed the latest research progress within the last four decades on the regulation, formation, exposure, and treatment of DBPs in the context of SPWs. This paper specifically discussed DBP regulations in different regions, formation mechanisms related with disinfectants, precursors and other various conditions, human exposure assessment reflected by biomarkers or epidemiological evidence, and the control and treatment of DBPs. Compared to drinking water with natural organic matter as the main organic precursor of DBPs, the additional human inputs (i.e., body fluids and personal care products) to SPWs make the water matrix more complicated and lead to the formation of more types and greater concentrations of DBPs. Dermal absorption and inhalation are two main exposure pathways for trihalomethanes while ingestion for haloacetic acids, reflected by DBP occurrence in human matrices including exhaled air, urine, blood, and plasma. Studies show that membrane filtration, advanced oxidation processes, biodegradation, thermal degradation, chemical reduction, and some hybrid processes are the potential DBP treatment technologies. The removal efficiency, possible mechanisms and future challenges of these DBP treatment methods are summarized in this review, which may facilitate their full-scale applications and provide potential directions for further research extension.

Nitrogen-doped carbon dot mediated fluorescence on–off assay for highly sensitive detection of I− and Br− ions

Nitrogen-doped carbon quantum dots (CDs) were synthesized in ethanol media by using citric acid (CA) as the carbon source and ethanediamine (EDA) as the nitrogen source.

Characterization of trihalomethane, haloacetic acid, and haloacetonitrile precursors in a seawater reverse osmosis system

Seawater reverse osmosis (SWRO) has been extensively applied to replenish the limited freshwater resources. One concern of such technology is the formation of disinfection by-products (DBPs) during the pre-chlorination process. For the SWRO tested in this study, the concentrations of trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs) increased by 35.1, 23.7 and 4.9μg/L, respectively, after a seawater sample (with UV₂₅₄/DOC of 3.7L/mg·m and Br^- of 50.9mg/L) was pre-chlorinated (1-2mg-Cl₂/L). The dissolved organic matter (DOM) with molecular weight (MW) <1kDa dominated the formation of total THMs, HAAs and HANs. To further investigate DBPs precursors in the seawater, the DOM with MW<1kDa was fractionated to hydrophobic acids (HOA), hydrophobic bases (HOB), hydrophobic neutrals (HON), and hydrophilic substances (HIS). The excitation emission matrix fluorescence spectra analysis showed that most aromatic protein and fulvic acid of the DOM with MW<1kDa were present in the HON and HIS fractions. The HON fraction was the dominant precursor to form THMs and HAAs, while HIS controlled the formation of HANs. Furthermore, bromo - DBPs dominated the total DBPs yields after the chlorination of HIS fraction.

The screening of metal ion inhibitors for glucose oxidase based on the peroxidase-like activity of nano-Fe3O4

In this study, a colorimetric method is proposed based on the peroxidase-like activity of Fe₃O₄magnetic nanoparticles for screening metal ion inhibitors for glucose oxidase activity.

Detection of water contamination from hydraulic fracturing wastewater: a μPAD for bromide analysis in natural waters

A field test was developed for the quantification of bromide in water as an indicator of contamination from hydraulic fracturing.

Distribution and formation of chlorophenols and bromophenols in marine and riverine environments

To understand the distribution and formation of chlorophenols (CPs) and bromophenols (BPs), we analyzed water and sediment samples collected from the riverine areas and the marine environments near a nuclear power plant (NPP) in Korea. In the seawater, only BPs (2,4-dibromophenol and 2,4,6-tribromophenol) were detected, while CPs and BPs (4-chlorophenol, 2,6-dichlorophenol, 2,4,6-trichlorophenol and 2,4,6-tribromophenol) were detected in the riverine water. 2,4-DBP (0.531-32.7 ng/L) in the seawater was detected in sites near the NPP and 2,4,6-TBP (0.378-20.2 ng/L) was found in most of the seawater. In the riverine water, the sample near the industrial complex (118 ng/L) showed a greater total concentration than others (0.510-7.64 ng/L). In the marine sediments, BPs (99.0-553 ng/g dry weight) showed higher concentrations than CPs (0.145-16.1 ng/g dry weight). The BPs levels (1.01-8.55 ng/g dry weight) in the riverine sediments were much lower (10-500 times) than those in the marine sediments. The distribution patterns of CPs and BPs between the marine and riverine environments differed, with relatively high levels of BPs appearing in the marine environments due to natural formation except for anthropogenic sources. The chlorination process of the NPP also seems to form BPs (2-bromophenol, 2,4-dibromophenol and 2,4,6-tribromophenol). However, the effluents had an influence on the seawater near the NPP (about 2 km). In the riverine environments, CPs were dominant, which are related to the industrial complex. Thus, CPs and BPs in the marine and riverine environments are generated via various routes such as anthropogenic formation and biosynthesis.

Multicommuted flow system employing pinch solenoid valves and micro-pumps

A multicommuted spectrophotometric flow-based procedure for the determination of paracetamol in pharmaceutical formulations is proposed. The method is based on the reaction of paracetamol with sodium hypochlorite forming N-acetyl-p-benzoquinoneimine, which reacts with sodium salicylate in alkaline medium producing a blue indophenol dye that was measured at 640nm. The flow system was designed employing four pinch solenoid valves and two solenoid micro-pumps, which were assembled aiming to obtain a compact module, resulting in minimization of reagents consumption and waste generation. Aiming to prove the usefulness of flow system an analytical procedure for paracetamol determination in pharmaceutical formulations was developed. To allow accuracy assessment samples were also analyzed using the AOAC reference method. Applying the paired t-test between results no significant difference at the 95% confidence level was observed. Other profitable features such as a linear response ranging from 5.0 to 125.0mgl(-1) (R=0.9992, n=7), a sampling rate of 60 determinations per hour, a detection limit of 0.4mgl(-1) paracetamol, a relative standard deviation of 1.5% (n=11) for a typical sample solution containing 25.0mgl(-1) paracetamol, reagent consumption of 1.28mg sodium hypochlorite and 6.4mg sodium salicylate per determination were also achieved.