NaClO4 Solutions Research Articles

Catalyst deactivation in the hydrodechlorination of micropollutants. A case of study with neonicotinoid pesticides

This work aims to analyse the effectiveness of catalytic hydrodechlorination (HDC) for the degradation of the neonicotinoid pesticides listed in the EU Watch List (Decision 2018/840): acetamiprid (ACT), imidacloprid (IMD), clothianidin (CLT), thiacloprid (THC) and thiamethoxam (THM). With the exception of THC, all neonicotinoid pesticides (1000 μg L−1) were completely removed in 30 min at 25 °C, using 0.25 g L−1 of a commercial Pd/Al2O3 (1 wt. %) catalyst and 50 N mL min−1 H2 flow rate. Strikingly, the micropollutant nature played a critical role on the activity and stability of the catalyst. The sulphur-bearing structures (CLT, THC and THM) showed the slowest degradation rates and led to a progressive deactivation of the catalyst. TEM/EDS and elemental analyses confirmed that the selective interaction of sulphur species on Pd active sites was the main reason for catalyst deactivation. The position of the heteroatom in the pesticide structure also influenced the catalytic deactivation. The catalyst showed a constant activity upon its sequential use in the HDC of ACT and IMD when these compounds were treated individually. Nevertheless, the interaction of the sulphur-containing compounds with the catalyst was remarkably favoured when the five micropollutants were treated in a mixture. A deactivation kinetic model in a long-term experiment was proposed with THC. To overcome catalyst deactivation, a regeneration procedure, based on a simple catalyst washing with a diluted NaClO solution, was developed. The process suitability was finally demonstrated in successive HDC-regeneration runs.

Theoretical analysis of the influence of spatial-spectral characteristics of a quartz surface on the field contrast during photochemical polishing

A method of photochemical subnano-polishing of a quartz surface covered with NaClO solution is considered when the lighting is produced from the quartz side at an angle that provides the total internal reflection of light. It was found the use of the effect of total internal reflection of light significantly enhances the electric field near the quartz surface with a sinusoidal profile (about three times) compared with direct illumination of such a surface under the normal incidence of light from the side of the solution. It has also been shown that for a random profile with a Gaussian correlation function at the initial stage of polishing, the etching of the components of the profile spatial spectrum located near the maximum of the spectral function derivative, as well as in the frequency region having resonance with the incident wave, occurs most intensively.

Separation of ions from water and wastewater using micro-scale capacitive-faradaic fuel cells (CFFCs), powered by H2(g) and air

A novel method for separation of ions from water and wastewater is proposed. The technique utilizes micro-scale porous conducting particles (e.g. activated carbon) loaded with bifunctional catalyst capable of hydrogen oxidation and oxygen reduction reactions. Within the proposed process of ions removal, the particles act as micro-scale adsorbing capacitive-faradaic fuel cells (CFFCs) which require air and hydrogen gas for the adsorption of ions during the water treatment step and desorption of ions in the brine production.The process was proved for the removal of perchlorate ions from NaClO4 solutions in deionized water and groundwater using two types of CFFCs prepared from Lewatit AF5 microporous carbon and a powdered activated charcoal loaded with Pt (5 wt%) catalyst. During the O2-induced adsorption of ClO4− ions, the reduction of atmospheric oxygen on Pt (faradaic electrode of the CFFC) results in depletion of electrons from the carbonaceous part (i.e. the capacitive electrode) of the micro-scale fuel cell, which leads to adsorption of anions in the electric double layer. The hydrogen oxidation reaction that occurs during the regeneration of the ClO4− - loaded CFFCs results in accumulation of electrons in the capacitive electrode and in repulsion of perchlorate ions into the regenerant solution. The principle of the novel technique was also proved for separation of Cu2+ cations from CuCl2 solution using micro-scale CFFCs made of Lewatit AF5 loaded with Pt catalyst (wt 5%). In these experiments the fuel cells were powered by H2 gas during the Cu2+ adsorption step and by air during the regeneration.

Secret underneath: Fouling of membrane support layer in anaerobic osmotic membrane bioreactor (AnOMBR)

Anaerobic osmotic membrane bioreactor (AnOMBR) holds promise for simultaneous wastewater purification and biogas production, allowing for an energy and carbon-neutral treatment facility. In a typical AnOMBR, reverse osmosis (RO) is employed for re-concentrating draw solution for continuous operation and cost saving. We compared membrane fouling behaviors between AnOMBR-RO hybrid system and AnOMBR without RO unit. We concluded that the porous support layer was susceptible to both inorganic scaling and biofouling in the closed-loop AnOMBR-RO system. We also explored two cleaning approaches to mitigate inorganic scaling and biofouling. Specifically, ethylenediaminetetraacetic acid (EDTA) was introduced into draw solution for minimizing inorganic scaling, but biofouling was deteriorated as EDTA provided extra nutrients for bacterial proliferation and biofouling. On the other hand, chemical cleaning of membrane support layer was performed using NaClO solution for biofouling control, but such cleaning efficacy attenuated after several cleaning cycles, because inorganic minerals accumulated and grew within membrane porous layer which could not be flushed by NaClO cleaning. Our finding highlighted the complexity and courter intuitive perspective to membrane fouling and cleaning in AnOMBR-RO hybrid system for inorganic scaling and biofouling management.

Ionophore properties of valinomycin in the model bilayer lipid membrane 1. Selectivity towards a cation

The electrochemical impedance spectroscopy (EIS) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) techniques were employed to study the ionophore properties of valinomycin in a model floating bilayer lipid membrane (fBLM) in perchlorate supporting electrolytes with potassium and sodium cations. Valinomycin decreases the membrane resistance of the fBLM in KClO4 solution by about 180 times, while it has a negligible effect on the membrane resistivity in NaClO4 solution. The IR spectra indicate that valinomycin forms a complex with K+, but not with Na+. The valinomycin-K+ complex adopts a small tilt angle with respect to the electrode surface normal and is well interdigitated between the acyl chains of the bilayer. The EIS and PM-IRRAS results indicate that valinomycin forms complexes with K+ and transports K+ across the lipid bilayer. This transport is potential independent and hence has a passive character.

Study on the Effect of Bleaching Treatment on the Mechanical Properties of Kenaf Fibers

Automotive industries are trying to reduce the weight of cars by replacing parts that are made of steel and aluminum with lighter material but equally strong. It is an emerging trend in these industries to utilize polypropylene reinforced with natural fiber as the alternative lightweight material. PP-natural fiber composite is projected to have market growth with compound annual growth rate (CAGR) of 9.5% within 2018-2025. Blending PP with natural fiber is a challenging process considering these two materials are not compatible enough to produce composite with desired mechanical properties. Prior treatment to the fiber is required to improve its compatibility with PP with cautionary that it does not degrading the mechanical strength of the fiber. The aim of this work was to study the effect of chemical treatment on Kenaf fiber to the tensile strength of the fiber. Kenaf fiber was bleached with NaClO solution at various concentration (1-10% v/w), temperature (25-55°C), and duration (1-6 hours). The effect of bleaching treatment to the chemical structure and the tensile strength of the fiber was analyzed using FTIR and UTM respectively. This study showed that the fiber with highest tensile strength was the one that treated with NaClO solution with concentration 1% v/w, at 25°C for 1 hour. This treatment removed impurities for the surface and reduced some amorphous part of the fiber. However further increasing NaClO concentration, mixing temperature and duration will damage the cellulose chain in Kenaf fiber which will decrease the mechanical strength of the fiber.

Fabrication of pervaporation desalination membranes with excellent chemical resistance for chemical washing

Pervaporation membranes have exhibited great potential for desalinating brine solutions. However, the flux recovery after membrane washing and the membrane's resistance to chemical cleaning reagents were barely studied. Our group has reported excellent desalination properties of PVA based pervaporation membranes. Nevertheless, the membranes were damaged during chemical cleaning due to the poor chlorine resistance of PVA. In this study, the more active 1, 2-diol units of PVA were removed by sodium periodate treatment. And then, the modified PVA was crosslinked by FS-3100, a fluorocarbon based crosslinker, to improve its hydrostability and chlorine resistance. The FS-3100 crosslinked composite (PVA-FS/PVDF) showed a water flux of 34 ± 1 kg m−2 h−1 with a NaCl rejection of 99.93% when desalinated a 35000 ppm NaCl solution at 70 °C. Salt rejections were maintained after soaking in 2000 ppm NaClO, acid (pH = 2), and alkali (pH = 12) solutions for 168, 180, and 180 h, respectively. A long term desalination experiment was carried out using Tween 20 and HA as foulants. The water fluxes could be recovered to 100% after chemical washing without losing salt rejections, indicating an excellent long term operation stability of the FS-3100 crosslinked PV membranes.

Improving chlorine resistance and separation performance of thin-film composite nanofiltration membranes with in-situ grafted melamine

Nanofiltration (NF) membranes exhibit great performance deterioration when contacting with high concentration chlorine solutions, which is unbeneficial to their sustainable operation. Herein, a chlorine-stable melamine was surface-grafted to the polyamide membrane by a covalent modification method to improve the anti-chlorine property of NF membranes. The grafting of melamine significantly changed the surface features of NF membranes. The grafted membranes owned rougher morphology, narrower pore size, higher hydrophilicity, and greater positive charge compared to the unmodified membrane. Higher salt rejections (NaCl, MgCl2, MgSO4, and Na2SO4) with slightly declined water permeability were obtained for the grafted membranes. Importantly, the optimized membrane with melamine grafting could maintain a high separation performance when contacting with 2000 ppm NaClO solution for 10 h at a pH of 10.5. For the control membrane without modification, more defects appeared on the membrane surface when the pH of the chlorine solution decreased from 10.5 to 3.5. In contrast, the original surface characteristics and chemical structures of the grafted membranes were well preserved under the same conditions. The grafting layer endowed the grafted membrane outstanding chlorine resistance and high separation performance, making it attractive for the construction of chlorine tolerant desalination membranes for the environmental process.

Macroscopic Kinetics of Simultaneous Desulfurization and Denitrification by MgO/NaClO2 Solution

Based on the early research results of reaction characteristics of the simultaneous desulfurization and denitrification by MgO/NaClO2 solution, the macroscopic reaction kinetics was investigated in a small-scale bubbling reactor. The effect of various factors on the reaction rate was investigated in the experiments, i.e. initial NaClO2 concentration, solution pH and reaction temperature. The reaction rate equations and the reaction order of NO, SO2 and NaClO2 were also obtained by experiments and analysis. The results showed that reaction orders of NO, SO2 and NaClO2 during simultaneous desulfurization and denitrification were all pseudo-first-order. And the reaction equations of NO, SO2 and NaClO2 were r=0.079C0.984 NO , r=0.066C0.989 SO 2 and r=0.066C0.998 SO 2 , respectively. The reaction rate of NO, SO2 and NaClO2 were proportional to the NaClO2 concentration and inversely proportional to the solution pH; the reaction rate of SO2 was less affected by the concentration and pH of NaClO2. When the reaction temperature was 50 °C, the reaction rate of NO and SO2 was the largest, and the reaction temperature had little effect on the reaction rate of NaClO2.

Self-assembly of octanethiol on oxide-free cobalt electrode from aqueous solution under electrochemical control

Self-assembly of alkanethiols on Co surface from organic solution has met with limited success due to the presence of the native oxides. A way needs to be found to remove any oxide and form perfect self-assembled monolayers (SAMs). We report the development of electrochemical approach for formation of alkanethiol self-assembled monolayers on base metals in aqueous solutions. For formation of octanethiol (OT) SAMs on oxide-free cobalt surfaces, we combine the surface renewal technique with in situ electrochemical procedure of removing the native oxide, thiol adsorption, and electrochemical control of SAMs properties in one aqueous solution. The use of aqueous thiol-containing media results in removing any oxide by electrochemical reduction, accelerated monolayer formation under electrochemical control, and investigating SAMs surface coverage and monolayer integrity by voltammetry. In this work, we study the influence of different factors on self-assembly process such as the surface pretreatment, adsorption time, the presence of dissolved oxygen, solution pH, and potential cycling on polycrystalline cobalt microelectrode from aqueous 0.1 M NaClO4 solutions of 0.1 mM OT. We obtain the high-quality self-assembled monolayers which are stable in wide range of potentials and show blocking characteristics toward the following Faradaic processes: Co surface oxidation and O2 and H+ reduction.

Tunable electrochemical activity of polyaniline salt by doping anion exchange

The exchange of mobile anion of chemically synthesized polyaniline with counter anions of electrolyte solutions is studied by using cyclic voltammetry (CV). The synthesized polyaniline (PANI) doped with sulfuric acid (H2SO4) and dodecyl benzenesulfonic acid (DBSA) is soluble in a wide range of organic solvents which makes it appealing for further processability. The exchange of dopant anions (of H2SO4 and DBSA) with a variety of counter anion has been inspected by electrochemical cycling in aqueous sodium sulfate (Na2SO4), sodium perchlorate (NaClO4), and sodium hydroxide (NaOH) solution. The CV measurements have revealed that PANI remains redox active at higher scan rate and there is exchange of dopant anion with SO42- and ClO41- of electrolytes. In NaOH solution, the emeraldine salt form of PANI is transformed into emeraldine base due to deintercalation of the anion form polymer matrix. The results indicate a significant change in electrochemical conductance and behavior of PANI in each electrolyte. Furthermore, the polymer film displayed a high specific capacitance value of 588 F/g in 1.0 M NaClO4 solution in the optimized potential window of -0.2 V to 0.9 V at 20 mV/s.

Preparation of antibacterial conductive cotton fabrics via silane-modified polypyrrole

In this study, silane-modified polypyrrole (PPy) was coated onto cotton fabrics through a conventional “in situ polymerization” method. And by chlorination with NaClO solution, we obtained antimicrobial conductive PPy/Si–Cl–cotton fabrics. The PPy/Si–Cl–cotton fabrics were characterized by scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared and thermogravimetric analysis. Also, the electrical conductivity property, antibacterial property, and ultraviolet light stability of the coated fabrics were tested. The PPy/Si–Cl–cotton fabrics showed antimicrobial and electrical conductivity properties when the chlorination time was up to 30 s. The chlorine content was 0.30 wt% and the resistance was 26.79 kΩ/cm. The PPy/Si–Cl–cotton fabrics (Cl+% 0.30) showed excellent antibacterial properties against 100% Staphylococcus aureus and 100% Escherichia coli O157:H7 were inactivated within 1 min of contact. Due to the proportional relationship of the electrical conductivity and chlorine content of the PPy/Si–Cl–cotton fabrics, the electrical conductivity of the PPy/Si–Cl–cotton fabrics can be used for monitoring the antimicrobial activity.

Preparation and performance of a solid-state thin-film Ag/AgCl quasi-reference electrode modified by chitosan-graphene

ABSTRACT Ag/AgCl reference electrode is widely used in electrochemical and photoelectrochemical measurement. In this paper, we developed a solid-state thin film Ag/AgCl quasi-reference electrode modified by chitosan-graphene. The quasi-reference electrode consisted of Ag layer (deposited by magnetron sputtering), AgCl layer (chloridized by NaClO solution), and modification membrane. The performance of a bared Ag/AgCl electrode, an Ag/AgCl electrode modified by chitosan, graphene, and by chitosan-graphene respectively was investigated. Surface morphology, energy spectrum, and electrochemical experiments were conducted in four Ag/AgCl electrodes with different modifications, respectively. With the surface morphology and energy spectrum analysis, the thickness of Ag layer and the conversion of Ag to AgCl were verified firstly. Then the durability, reversibility, and CV behavior were tested in different solutions. The results demonstrated excellent features of the Ag/AgCl quasi-reference electrode modified by chitosan-graphene in all measurements. The developed quasi-reference electrode can be applied in pH measurement, electrochemical tests, and photoelectrochemical test.

Effect of Wet Scrubbing Oxidation Denitration Technology Combined with Ultraviolet Online Irradiation on the Efficiency of Desulfurization and Denitrification of Ship Exhaust Gas

In order to alleviate the air pollution caused by nitrogen and sulfur oxides discharged from ships, the efficient method of deoxidization and desulfurization of marine diesel engine exhaust gas has been explored. In this study, at present, the mainstream technology of ship exhaust gas removal at home and abroad, wet scrubbing oxidation denitration technology is taken as the research object. Ultraviolet (UV) online irradiation is introduced into the process of wet scrubbing oxidation denitration of NaClO2 solution. The effects of different parameters, such as the concentration of NaClO2, the temperature of washing solution, the concentration of O2 and SO2, on the removal of No are studied. The reaction mechanism is further analyzed. The results show that photochemical reaction will take place between UV online irradiation and NaClO2 solution, resulting in a large number of active radicals with strong oxidation, which can obviously enhance the effect of No removal by wet scrubbing of NaClO2 solution. It can be seen that the wet scrubbing oxidation denitration technology combined with UV online irradiation can greatly improve the efficiency of desulfurization and denitrification of ship's exhaust gas. It is an efficient method of deoxidization and desulfurization of ship's diesel engine exhaust gas, which is of great help to alleviate exhaust gas pollution.

“NaClO2-Sea Water” Wet Denitrification Technology Using NOx Treatment Technology in the Desulfurization and Denitrification of Ship Exhaust Gas

To minimize the emission pollution of nitrogen oxides (NOx) in marine diesel engine exhaust, based on the existing NOx treatment technology, the "NaClO2-sea water" wet denitrification technology was further proposed. The denitrification performance of NaClO2 solution in seawater and NaClO2 solution in fresh water was analyzed by self-designed and built experimental platform. Moreover, the effects of the temperature of the absorption solution, the initial concentration of NaClO2 and the concentration of NO in diesel exhaust gas on the denitrification performance of NaClO2 sea water solution were studied. The experimental results showed that the denitrification rate of NaClO2 solution with seawater as solvent was slightly lower than that of NaClO2 solution with fresh water, but the denitrification duration of seawater solution had obvious advantages over that of fresh water solution. In addition, by increasing the temperature of the absorption solution and the initial concentration of NaClO2 and decreasing the concentration of NO, the denitrification rate of NaClO2 sea water solution was increased. Whereas, if the temperature exceeded a certain limit, the continuous denitrification time of the solution would be decreased. Therefore, “NaClO2-sea water” wet denitrification technology has the advantages of cheap raw materials and long continuous denitrification time. High denitrification efficiency can be achieved by optimizing reaction conditions, so it can be used for denitrification of marine diesel engine exhaust gas.

Synthesis, structure and fluxionality of Co(III) complexes containing chelated sulfate

The syntheses and characterisation of the complexes [Co(pmea)(O2SO2)]ClO4 and [Co(pmap)(O2SO2)]ClO4 (pmea = bis((2-pyridyl)methyl)-2-((2-pyridyl)ethyl)amine; pmap = bis(2-(2-pyridyl)ethyl)(2-pyridylmethyl)amine), containing chelating sulfato ligands, are reported. These were prepared by oxidation of a solution containing CoSO4·7H2O and the tripodal tetraamine ligand with either (NH4)2[Ce(O2NO)6] (pmea) or Oxone (2KHSO5·KHSO4·K2SO4; pmap), and their structures were confirmed by X-ray crystallography. [Co(pmap)(O2SO2)]ClO4 crystallised as the 6-isomer from aqueous NaClO4 solution, while [Co(pmea)(O2SO2)]ClO4 was obtained as a mixture of the 5- and 6-isomers, with both isomers being able to be resolved in the X-ray structure. Comparison of the IR spectra of [Co(pmap)(O2SO2]ClO4 and [Co(pmap)(O2CO)]ClO4 allowed assignment of IR bands due to the chelated sulfato ligand. Fluxionality in [Co(pmea)(O2SO2)]ClO4 was resolved using 1H VT-NMR, and was found to result from ‘flapping’ of the pyridylethyl arm of the pmea ligand between two possible conformations.

Multinuclear Magnetic Resonance Study of Sodium Salts in Water Solutions

The small amounts of gaseous 3He dissolved in low concentrated water solutions of NaCl, NaNO3 and NaClO4 were prepared and examined by 3He-, 23Na-, 35Cl- and 15N-NMR spectroscopy. This experimental data, along with new theoretical shielding factors, was used to measure the 23Na nuclear magnetic moment against that of helium-3 μ(23Na) = +2.2174997(111) in nuclear magnetons. The standard relationship between NMR frequencies and nuclear magnetic moments of observed nuclei was used. The nuclear magnetic shielding factors of 23Na cation were verified against that of counter ions present in water solutions. Very good agreement between shielding constants σ(3He), σ(23Na+), σ(35Cl‒), σ(35ClO4‒), σ(15NO3‒) in water at infinite dilution and nuclear magnetic moments was observed for all magnetic nuclei. It can be used as a reference nucleus for calculating a few other magnetic moments of different nuclei by the NMR method. An analysis of new and former μ(23Na) experimental data obtained by the atomic beam magnetic resonance method (ABMR) and other NMR measurements shows good replicability of all specified results. The composition of sodium water complexes was discussed in terms of chemical equilibria and NMR shielding scale.

Investigation on inhibition of ruthenium corrosion by glycine in alkaline sodium hypochlorite based solution

Removal of Ru by etching in alkaline sodium hypochlorite (NaClO) based solution is carried out. The glycine on the corrosion of Ru in NaClO based solution is systematically investigated. The results show that in the alkaline NaClO solution, glycine is a good corrosion inhibitor for Ru. Through electrochemical measurements, electrochemical quartz crystal microbalance (EQCM) and X-Ray photoelectron microscopy (XPS) measurements, it is found that the glycine adsorption isotherm on the Ru surface follows TEMKIN’s model. Glycine can not only adsorb on the Ru surface to inhibit the corrosion of Ru, but also promote the dissolution of the formed oxide layer through complexing action. Finally, we use glycine and NaClO for chemical mechanical polishing (CMP) of the Cu/Ru interconnect structure and the removal rate selectivity of Cu and Ru can be adjusted to 1:1.

Chemical cleaning of algae-fouled ultrafiltration (UF) membrane by sodium hypochlorite (NaClO): Characterization of membrane and formation of halogenated by-products

This paper presents an investigation of the variation in membrane characteristics and formation of halogenated by-products during the off-line chemical cleaning of algae-fouled ultrafiltration (UF) membrane by NaClO solution. The chemical treatment led to the recovery of membrane flux, decrease of membrane hydrophilicity and HA rejection. Proteins, amino acids, and polysaccharides contained in algal cells were easy to adsorb on the membrane surface and contributed to the formation of halogenated by-products during the NaClO cleaning process. The increase of NaClO concentration and temperature significantly promoted the formation of most selected halogenated by-products. With the increase of pH, trichloromethane (TCM), dichloroacetic acid (DCAA) and trichloronitromethane (TCNM) rose continuously; monochloroacetic acid (MCAA), trichloroacetic acid (TCAA) and trichloroacetonitrile (TCAN) followed an increasing and then decreasing trend. With the prolonged exposure time from 2 to 24 h, most halogenated by-products from the cleaning of algal cell-, extracellular organic matter (EOM)- and humic acid (HA)-fouled membranes monotonically increased, while the formation of 1,1-dichloro-2-propanone (DCP) and dichloroacetonitrile (DCAN) varied differently. NaClO cleaning of algal cell-fouled membrane generated much lower concentrations of selected carbonaceous halogenated by-products and TCNM, but caused higher yields of haloacetonitriles (HANs) than that of HA-fouled membrane.

Separation and recovery of Rh, Ru and Pd from nitrate solution with a silica-based IsoBu-BTP/SiO2-P adsorbent

The separation of fission products Ru, Rh, and Pd will benefit both the nuclear fuel cycle and enlarge the platinum group metals source. A silica-based isoBu-BTP/SiO2-P adsorbent was used to separate Ru, Rh, and Pd from nitrate solution. It exhibited good adsorption towards Ru, Rh, and Pd with the uptake rates over 95% at 55 °C in 0.1 M HNO3–3 M NaNO3 solution and no adsorption towards 238U(VI). The adsorption towards Ru, Rh, and Pd matched well with pseudo-second-order model with the equilibrium obtained within 24 h, 24 h and 0.5 h and Langmuir adsorption isotherm model with the saturation adsorption amounts as high as 0.37 mmol/g, 0.34 mmol/g and 0.71 mmol/g respectively. The adsorbed Pd, Rh, and Ru can be desorbed by 0.1 M HNO3–0.1 M thiourea, 2 M HCl and NaClO solution (CP) which is expected to realize their mutual separation in desorption stage using the above-mentioned eluents successively. Both FT-IR and XPS revealed that CNC played key role during adsorption and the adsorption needed the participation of NO3− to keep charge balance. In a word, isoBu-BTP/SiO2-P is a promising adsorbent for separation and recovery Ru, Rh, and Pd, especially in the case of separating them from other fission products and actinides from high level liquid waste.